Lipidomics Resource Center
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Molecular Metabolism, 2019
1Comprehensive and quantitative analysis of white and brown adipose tissue by shotgun lipidomicsAbstractpublications
Shotgun lipidomics enables an extensive analysis of lipids from tissues and fluids. Each specimen requires appropriate extraction and processing procedures to ensure good coverage and reproducible quantification of the lipidome. Adipose tissue (AT) has become a research focus with regard to its involvement in obesity-related pathologies. However, the quantification of the AT lipidome is particularly challenging due to the predominance of triacylglycerides, which elicit high ion suppression of the remaining lipid classes.
We present a new and validated method for shotgun lipidomics of AT, which tailors the lipid extraction procedure to the target specimen and features high reproducibility with a linear dynamic range of at least 4 orders of magnitude for all lipid classes. Utilizing this method, we observed tissue-specific and diet-related differences in three AT types (brown, gonadal, inguinal subcutaneous) from lean and obese mice. Brown AT exhibited a distinct lipidomic profile with the greatest lipid class diversity and responded to high-fat diet by altering its lipid composition, which shifted towards that of white AT. Moreover, diet-induced obesity promoted an overall remodelling of the lipidome, where all three AT types featured a significant increase in longer and more unsaturated triacylglyceride and phospholipid species.
The here presented method facilitates reproducible systematic lipidomic profiling of AT and could be integrated with further –omics approaches used in (pre-) clinical research, in order to advance the understanding of the molecular metabolic dynamics involved in the pathogenesis of obesity-associated disorders.
BBA Biomembranes, 2019
2Membrane cholesterol depletion reduces downstream signaling activity of the adenosine A2a receptorAbstractpublications
Cholesterol has been shown to modulate the activity of multiple G Protein-coupled receptors (GPCRs), yet whether cholesterol acts through specific interactions, indirectly via modifications to the membrane, or via both mechanisms is not well understood. High-resolution crystal structures of GPCRs have identified bound cholesterols; based on a β2-adrenergic receptor (β2AR) structure bound to cholesterol and the presence of conserved amino acids in class A receptors, the cholesterol consensus motif (CCM) was identified. Here in mammalian cells expressing A2aR, ligand dependent production of cAMP is reduced following membrane cholesterol depletion with methyl-beta-cyclodextrin (MβCD), indicating that adenosine A2a receptor (A2aR) signaling is dependent on cholesterol. In contrast, ligand binding is not dependent on cholesterol depletion. All-atom molecular simulations suggest that cholesterol interacts specifically with the CCM when the receptor is in an active state, but not when in an inactive state. Taken together, the data support a model of receptor state-dependent binding between cholesterol and the CCM, which could facilitate both G-protein coupling and downstream signaling of A2aR.
Nature Communications Biology, 2018
3Dissection of metabolic reprogramming in polycystic kidney disease reveals coordinated rewiring of bioenergetic pathwaysAbstractpublications
Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a genetic disorder caused by loss-of-function mutations in PKD1 or PKD2. Increased glycolysis is a prominent feature of the disease, but how it impacts on other metabolic pathways is unknown. Here, we present an analysis of mouse Pkd1 mutant cells and kidneys to investigate the metabolic reprogramming of this pathology. We show that loss of Pkd1 leads to profound metabolic changes that affect glycolysis, mitochondrial metabolism, and fatty acid synthesis (FAS). We find that Pkd1-mutant cells preferentially use glutamine to fuel the TCA cycle and to sustain FAS. Interfering with either glutamine uptake or FAS retards cell growth and survival. We also find that glutamine is diverted to asparagine via asparagine synthetase (ASNS). Transcriptional profiling of PKD1-mutant human kidneys confirmed these alterations. We find that silencing of Asns is lethal in Pkd1-mutant cells when combined with glucose deprivation, suggesting therapeutic approaches for ADPKD.
4Compositions for facilitating membrane fusion and uses thereofAbstractproducts
In some aspects, fusosome compositions and methods are described herein that comprise membrane enclosed preparations, comprising a fusogen. In some embodiments, the fusosome can target the cell, thereby delivering complex biologic agents to the target cell cytoplasm.
5Viscous control of cellular respiration by membrane lipid compositionAbstractpublications
Lipid composition determines the physical properties of biological membranes and can vary substantially between and within organisms. We describe a specific role for the viscosity of energy-transducing membranes in cellular respiration. Engineering of fatty acid biosynthesis in Escherichia coli allowed us to titrate inner membrane viscosity across a 10-fold range by controlling the abundance of unsaturated or branched lipids. These fluidizing lipids tightly controlled respiratory metabolism, an effect that can be explained with a quantitative model of the Electron Transport Chain (ETC) that features diffusion-coupled reactions between enzymes and electron carriers (quinones). Lipid unsaturation also modulated mitochondrial respiration in engineered budding yeast strains. Thus, diffusion in the ETC may serve as an evolutionary constraint for lipid composition in respiratory membranes.
White Paper Series, 2018
6Unlocking the Power of MultiomicsAbstractwhite papers
Multiomics approaches are on their way to revolutionize medicine and biology. Being major players in cardiovascular disease research, genomics and lipidomics are perfectly suited for a joint multiomics approach. Combining genomic risk prediction with lipidomic phenotyping will result in an effective payoff.
This whitepaper will answer how linking the lipid phenotype to the genotype will improve performance and showcase immediate and future consequences for prevention, clinical diagnostics and drug research.
Frontiers in Psychiatry, 2018
7Lipidomics in Major Depressive DisorderAbstractreviews
Omic sciences coupled with novel computational approaches such as machine intelligence offer completely new approaches to major depressive disorder (MDD) research. The complexity of MDD’s pathophysiology is being integrated into studies examining MDD’s biology within the omic fields. Lipidomics, as a late-comer among other omic fields, is increasingly being recognized in psychiatric research because it has allowed the investigation of global lipid perturbations in patients suffering from MDD and indicated a crucial role of specific patterns of lipid alterations in the development and progression of MDD. Combinatorial lipid-markers with high classification power are being developed in order to assist MDD diagnosis, while rodent models of depression reveal lipidome changes and thereby unveil novel treatment targets for depression. In this systematic review, we provide an overview of current breakthroughs and future trends in the field of lipidomics in MDD research and thereby paving the way for precision medicine in MDD.
Scientific Reports, 2018
8Cholesterol is Inefficiently Converted to Cholesteryl Esters in the Blood of Cardiovascular Disease PatientsAbstractpublications
Shotgun lipidomic analysis of 203 lipids in 13 lipid classes performed on blood plasma of donors who had just suffered an acute coronary syndrome (ACS, n = 74), or an ischemic stroke (IS, n = 21), or who suffer from stable angina pectoris (SAP, n = 78), and an age-matched control cohort (n = 52), showed some of the highest inter-lipid class correlations between cholesteryl esters (CE) and phosphatidylcholines (PC) sharing a common fatty acid. The concentration of lysophospatidylcholine (LPC) and ratios of concentrations of CE to free cholesterol (Chol) were also lower in the CVD cohorts than in the control cohort, indicating a deficient conversion of Chol to CE in the blood plasma in the CVD subjects. A non-equilibrium reaction quotient, Q′, describing the global homeostasis of cholesterol as manifested in the blood plasma was shown to have a value in the CVD cohorts (Q′ACS = 0.217 ± 0.084; Q′IS = 0.201 ± 0.084; Q′SAP = 0.220 ± 0.071) that was about one third less than in the control cohort (Q′Control = 0.320 ± 0.095, p < 1 × 10−4), suggesting its potential use as a rapid predictive/diagnostic measure of CVD-related irregularities in cholesterol homeostasis.
Product development, 2018
9Photodamaged dry facial skin from different ethnic groupsAbstractproducts
Even though decades of moisturizer development have passed, dry facial skin remains a major concern for consumers. Thus, DSM’s aim was to understand more precisely the underlying biochemistry, particularly of the maturation of the stratum corneum and its relation to facial photodamage, skin pigmentation and ethnicity. In contrast to traditional research of skin analyte composition, a more revolutionary ‘omic’ approach was applied.
Journal of Biological Chemistry, 2018
10An oxanthroquinone derivative that disrupts RAS plasma membrane localization inhibits cancer cell growthAbstractpublications
Oncogenic RAS proteins are commonly expressed in human cancer. To be functional, RAS proteins must undergo post-translational modification and localize to the plasma membrane (PM). Therefore, compounds that prevent RAS PM targeting have potential as putative RAS inhibitors. Here we examine the mechanism of action of oxanthroquinone G01 (G01), a recently described inhibitor of KRAS PM localization. We show that G01 mislocalizes HRAS and KRAS from the PM with similar potency and disrupts the spatial organization of RAS proteins remaining on the PM. G01 also inhibited recycling of epidermal growth factor receptor and transferrin receptor, but did not impair internalization of cholera toxin, indicating suppression of recycling endosome function. In searching for the mechanism of impaired endosomal recycling we observed that G01 also enhanced cellular sphingomyelin (SM) and ceramide levels and disrupted the localization of several lipid and cholesterol reporters, suggesting that the G01 molecular target may involve SM metabolism. Indeed, G01 exhibited potent synergy with other compounds that target SM metabolism in KRAS localization assays. Furthermore, G01 significantly abrogated RAS-RAF-MAPK signaling in MDCK cells expressing constitutively activated, oncogenic mutant RASG12V. G01 also inhibited the proliferation of RAS-less mouse embryo fibroblasts (MEFs) expressing oncogenic mutant KRASG12V or KRASG12D but not RAS-less MEFs expressing oncogenic mutant BRAFV600E. Consistent with these effects, G01 selectively inhibited the proliferation of KRAS-transformed pancreatic, colon, and endometrial cancer cells. Taken together, these results suggest that G01 should undergo further evaluation as a potential anti-RAS therapeutic.
npj Vaccines, 2018
11Activation of the endoplasmic reticulum stress sensor IRE1α by the vaccine adjuvant AS03 contributes to its immunostimulatory propertiesAbstractpublications
The oil-in-water emulsion Adjuvant System 03 (AS03) is one of the few adjuvants used in licensed vaccines. Previous work indicates that AS03 induces a local and transient inflammatory response that contributes to its adjuvant effect. However, the molecular mechanisms involved in its immunostimulatory properties are ill-defined. Upon intramuscular injection in mice, AS03 elicited a rapid and transient downregulation of lipid metabolism-related genes in the draining lymph node. In vitro, these modifications were associated with profound changes in lipid composition, alteration of endoplasmic reticulum (ER) morphology and activation of the unfolded protein response pathway. In vivo, treatment with a chemical chaperone or deletion of the ER stress sensor kinase IRE1α in myeloid cells decreased AS03-induced cytokine production and its capacity to elicit high affinity antigen-specific antibodies. In summary, our results indicate that IRE1α is a sensor for the metabolic changes induced by AS03 in monocytic cells and may constitute a canonical pathway that could be exploited for the design of novel vaccine adjuvants.
12Methods and systems for metabolite and/or lipid-based detection of colorectal cancer and/or adenomatous polypsAbstractproducts
Described herein are sets of metabolite and lipid (e.g., fatty acid) markers that can be used in the detection of early stage colorectal cancer and/or early development of adenomatous polyps. Presented herein are illustrative pathology-linked panels. In certain embodiments, the markers presented herein (or subsets thereof) are used as a panel for detecting either colorectal cancer or adenomatous polyps at the same time. The markers presented herein include metabolites and lipids (e.g., fatty acid) freely detectable and accurately quantifiable in human serum. In certain embodiments, the sample may be plasma, urine, saliva, whole blood, dried blood spot or dried serum spot.
13ER Lipid Defects in Neuropeptidergic Neurons Impair Sleep Patterns in Parkinson’s DiseaseAbstractpublications
Parkinson’s disease patients report disturbed sleep patterns long before motor dysfunction. Here, in parkin and pink1 models, we identify circadian rhythm and sleep pattern defects and map these to specific neuropeptidergic neurons in fly models and in hypothalamic neurons differentiated from patient induced pluripotent stem cells (iPSCs). Parkin and Pink1 control the clearance of mitochondria by protein ubiquitination. Although we do not observe major defects in mitochondria of mutant neuropeptidergic neurons, we do find an excess of endoplasmic reticulum-mitochondrial contacts. These excessive contact sites cause abnormal lipid trafficking that depletes phosphatidylserine from the endoplasmic reticulum (ER) and disrupts the production of neuropeptide-containing vesicles. Feeding mutant animals phosphatidylserine rescues neuropeptidergic vesicle production and acutely restores normal sleep patterns in mutant animals. Hence, sleep patterns and circadian disturbances in Parkinson’s disease models are explained by excessive ER-mitochondrial contacts, and blocking their formation or increasing phosphatidylserine levels rescues the defects in vivo.
Biochemical Journal, 2018
14A phosphatidic acid binding protein is important for lipid homeostasis and adaption to anaerobic biofilm conditions in Pseudomonas aeruginosaAbstractpublications
A quantitative Pseudomonas aeruginosa proteomics approach revealed increased abundance of the so far uncharacterized protein PA3911 in anaerobic biofilms grown under conditions of the cystic fibrosis lung. Physiological relevance of ORF PA3911 was demonstrated, inter alia, using phenotype microarray experiments. The mutant strain showed increased susceptibility in the presence of antimicrobials (minocycline, nafcillin, oxacillin, chloramphenicol, thiamphenicol), enhanced twitching motility and significantly impaired biofilm formation. PA3911 is a soluble, cytoplasmic protein in P. aeruginosa. In protein-lipid overlay experiments, purified PA3911 bound specifically to phosphatidic acid (PA), the central hub of phospholipid metabolism. Structure-guided site-directed mutagenesis was used to explore the proposed ligand binding cavity of PA3911. Proteins variant of Leu56, Leu58, Val69 and Leu114 were shown to impair PA interaction. A comparative shotgun lipidomics approach demonstrated a multifaceted response of P. aeruginosa to anaerobic conditions at the lipid head group and fatty acid level. Lipid homeostasis in the PA3911 mutant strain was imbalanced with respect to lysophosphatidylcholine, phosphatidylcholine and diacylglycerol under anaerobic and/or aerobic conditions. The impact of the newly identified PA binding protein on lipid homeostasis and the related macroscopic phenotypes of P. aeruginosa are discussed.
Product development, 2018
15Lipid analysis for skin penetration properties of saturated phospholipidsAbstractproducts
Lipoid conducted this novel study to investigate skin penetration properties of dermal formulations based on hydrogenated phospholipids. Common to all topically used phospholipids is their ability to interact with skin structures and the similarity to epidermal lipids. For the first time, the quantitative analysis of both exogenous phospholipids and endogenous skin lipids within a single measurement was demonstrated. The results confirm the properties of hydrogenated phospholipids to penetrate and accumulate in upper epidermal layers.
Phytochemical Analysis, 2018
16Dereplication of plant phenolics using a mass‐spectrometry database independent methodAbstractpublications
Dereplication, an approach to sidestep the efforts involved in the isolation of known compounds, is generally accepted as being the first stage of novel discoveries in natural product research. It is based on metabolite profiling analysis of complex natural extracts.
To present the application of LipidXplorer for automatic targeted dereplication of phenolics in plant crude extracts based on direct infusion high‐resolution tandem mass spectrometry data.
LipidXplorer uses a user‐defined molecular fragmentation query language (MFQL) to search for specific characteristic fragmentation patterns in large data sets and highlight the corresponding metabolites. To this end, MFQL files were written to dereplicate common phenolics occurring in plant extracts. Complementary MFQL files were used for validation purposes.
New MFQL files with molecular formula restrictions for common classes of phenolic natural products were generated for the metabolite profiling of different representative crude plant extracts. This method was evaluated against an open‐source software for mass‐spectrometry data processing (MZMine®) and against manual annotation based on published data.
The targeted LipidXplorer method implemented using common phenolic fragmentation patterns, was found to be able to annotate more phenolics than MZMine® that is based on automated queries on the available databases. Additionally, screening for ascarosides, natural products with unrelated structures to plant phenolics collected from the nematode Caenorhabditis elegans, demonstrated the specificity of this method by cross‐testing both groups of chemicals in both plants and nematodes.
17How Can Omic Science be Improved?Abstractreviews
One of the promises of multiomic analysis was to transform the clinical diagnostics to deliver much more exact phenotyping of disease states. However, despite enormous investments, the transformation of clinical routine has not taken place. There are many reasons for this lack of success but one is the failure to deliver quantitative and reproducible data. This failure is not only impeding progress in clinical phenotyping but also in the application of omic science in systems biology. The focus in this Viewpoint will be on lipidomics but the lessons learned are generally applicable
Cancer Research, 2018
18Organelle-derived acetyl-CoA promotes prostate cancer cell survival, migration, and metastasis via activation of calmodulin kinase IIAbstractpublications
Although emerging evidence suggests a potential role of calcium/calmodulin-dependent kinase II (CaMKII) in prostate cancer (PCa), its role in PCa tumorigenesis is largely unknown. Here we examine whether the acetyl CoA-CaMKII pathway, first described in frog oocytes, promotes PCa tumorigenesis. In human PCa specimens, metastatic PCa expressed higher levels of active CaMKII compared to localized PCa. Correspondingly, basal CaMKII activity was significantly higher in the more tumorigenic PC3 and PC3-mm2 cells relative to the less tumorigenic LNCaP and C4-2B4 cells. Deletion of CaMKII by CRISPR/Cas9 in PC3-mm2 cells abrogated cell survival under low-serum conditions, anchorage-independent growth and cell migration; overexpression of constitutively active CaMKII in C4-2B4 cells promoted these phenotypes. In an animal model of PCa metastasis, genetic ablation of CaMKII reduced PC3-mm2 cell metastasis from the prostate to the lymph nodes. Knockdown of the acetyl-CoA transporter carnitine acetyltransferase (CRAT) abolished CaMKII activation, providing evidence that acetyl-CoA generated from organelles is a major activator of CaMKII. Genetic deletion of the β-oxidation rate-limiting enzyme ACOX family proteins decreased CaMKII activation, while overexpression of ACOXI increased CaMKII activation. Overall, our studies identify active CaMKII as a novel connection between organelle β-oxidation and acetyl-CoA transport with cell survival, migration, and PCa metastasis.
Current Protocols in Bioinformatics, 2018
19LipidXplorer: Software for Quantitative Shotgun Lipidomics Compatible with Multiple Mass Spectrometry PlatformsAbstractpublications
LipidXplorer is an open-source software kit that supports the identification and quantification of molecular species of any lipid class detected by shotgun experiments performed on any mass spectrometry platform. LipidXplorer does not rely on a database of reference spectra: instead, lipid identification routines are user defined in the declarative molecular fragmentation query language (MFQL). The software supports batch processing of multiple shotgun acquisitions by high-resolution mass mapping, precursor and neutral-loss scanning, and data-dependent MS/MS lending itself to a variety of lipidomics applications in cell biology and molecular medicine.
Molecular and Cellular Biology, 2018
20Sphingomyelin Metabolism Is a Regulator of K-Ras FunctionAbstractpublications
K-Ras must localize to the plasma membrane (PM) for biological activity. We show here that multiple acid sphingomyelinase (ASM) inhibitors, including tricyclic antidepressants, mislocalized phosphatidylserine (PtdSer) and K-RasG12V from the PM, resulting in abrogation of K-RasG12V signaling and potent, selective growth inhibition of mutant K-Ras-transformed cancer cells. Concordantly, in nude mice, the ASM inhibitor fendiline decreased the rate of growth of oncogenic K-Ras-expressing MiaPaCa-2 tumors but had no effect on the growth of the wild-type K-Ras-expressing BxPC-3 tumors. ASM inhibitors also inhibited activated LET-60 (a K-Ras ortholog) signaling in Caenorhabditis elegans, as evidenced by suppression of the induced multivulva phenotype. Using RNA interference against C. elegans genes encoding other enzymes in the sphingomyelin (SM) biosynthetic pathway, we identified 14 enzymes whose knockdown strongly or moderately suppressed the LET-60 multivulva phenotype. In mammalian cells, pharmacological agents that target these enzymes all depleted PtdSer from the PM and caused K-RasG12V mislocalization. These effects correlated with changes in SM levels or subcellular distribution. Selected compounds, including sphingosine kinase inhibitors, potently inhibited the proliferation of oncogenic K-Ras-expressing pancreatic cancer cells. In conclusion, these results show that normal SM metabolism is critical for K-Ras function, which may present therapeutic options for the treatment of K-Ras-driven cancers.
21Modulation of Myelopoiesis Progenitors Is an Integral Component of Trained ImmunityAbstractpublications
Trained innate immunity fosters a sustained favorable response of myeloid cells to a secondary challenge, despite their short lifespan in circulation. We thus hypothesized that trained immunity acts via modulation of hematopoietic stem and progenitor cells (HSPCs). Administration of β-glucan (prototypical trained-immunity-inducing agonist) to mice induced expansion of progenitors of the myeloid lineage, which was associated with elevated signaling by innate immune mediators, such as IL-1β and granulocyte-macrophage colony-stimulating factor (GM-CSF), and with adaptations in glucose metabolism and cholesterol biosynthesis. The trained-immunity-related increase in myelopoiesis resulted in a beneficial response to secondary LPS challenge and protection from chemotherapy-induced myelosuppression in mice. Therefore, modulation of myeloid progenitors in the bone marrow is an integral component of trained immunity, which to date, was considered to involve functional changes of mature myeloid cells in the periphery.
PLOS genetics, 2018
22Adipose tissue ATGL modifies the cardiac lipidome in pressure-overload-induced left ventricular failureAbstractpublications
Adipose tissue lipolysis occurs during the development of heart failure as a consequence of chronic adrenergic stimulation. However, the impact of enhanced adipose triacylglycerol hydrolysis mediated by adipose triglyceride lipase (ATGL) on cardiac function is unclear. To investigate the role of adipose tissue lipolysis during heart failure, we generated mice with tissue-specific deletion of ATGL (atATGL-KO). atATGL-KO mice were subjected to transverse aortic constriction (TAC) to induce pressure-mediated cardiac failure. The cardiac mouse lipidome and the human plasma lipidome from healthy controls (n = 10) and patients with systolic heart failure (HFrEF, n = 13) were analyzed by MS-based shotgun lipidomics. TAC-induced increases in left ventricular mass (LVM) and diastolic LV inner diameter were significantly attenuated in atATGL-KO mice compared to wild type (wt) -mice. More importantly, atATGL-KO mice were protected against TAC-induced systolic LV failure. Perturbation of lipolysis in the adipose tissue of at ATGL-KO mice resulted in the prevention of the major cardiac lipidome changes observed after TAC in wt-mice. Profound changes occurred in the lipid class of phosphatidylethanolamines (PE) in which multiple PE-species were markedly induced in failing wt-hearts, which was attenuated in atATGL-KO hearts. Moreover, selected heart failure-induced PE species in mouse hearts were also induced in plasma samples from patients with chronic heart failure. TAC-induced cardiac PE induction resulted in decreased PC/ PE-species ratios associated with increased apoptotic marker expression in failing wt-hearts, a process absent in atATGL-KO hearts. Perturbation of adipose tissue lipolysis by ATGL-deficiency ameliorated pressure-induced heart failure and the potentially deleterious cardiac lipidome changes that accompany this pathological process, namely the induction of specific PE species. Non-cardiac ATGL-mediated modulation of the cardiac lipidome may play an important role in the pathogenesis of chronic heart failure.
Current Biology, 2017
23Cell Size and Growth Rate Are Modulated by TORC2-Dependent SignalsAbstractpublications
The size of all cells, from bacteria to vertebrates, is proportional to the growth rate set by nutrient availability, but the underlying mechanisms are unknown. Here, we show that nutrients modulate cell size and growth rate via the TORC2 signaling network in budding yeast. An important function of the TORC2 network is to modulate synthesis of ceramide lipids, which play roles in signaling. TORC2-dependent control of ceramide signaling strongly influences both cell size and growth rate. Thus, cells that cannot make ceramides fail to modulate their growth rate or size in response to changes in nutrients. PP2A associated with the Rts1 regulatory subunit (PP2A[Rts1]) is embedded in a feedback loop that controls TORC2 signaling and helps set the level of TORC2 signaling to match nutrient availability. Together, the data suggest a model in which growth rate and cell size are mechanistically linked by ceramide-dependent signals arising from the TORC2 network.
Journal of Lipid Research, 2017
24Harmonizing lipidomics: NIST interlaboratory comparison exercise for lipidomics using SRM 1950–Metabolites in Frozen Human PlasmaAbstractpublications
As the lipidomics field continues to advance, self-evaluation within the community is critical. Here, we performed an interlaboratory comparison exercise for lipidomics using Standard Reference Material (SRM) 1950–Metabolites in Frozen Human Plasma, a commercially available reference material. The interlaboratory study comprised 31 diverse laboratories, with each laboratory using a different lipidomics workflow. A total of 1,527 unique lipids were measured across all laboratories and consensus location estimates and associated uncertainties were determined for 339 of these lipids measured at the sum composition level by five or more participating laboratories. These evaluated lipids detected in SRM 1950 serve as community-wide benchmarks for intra- and interlaboratory quality control and method validation. These analyses were performed using nonstandardized laboratory-independent workflows. The consensus locations were also compared with a previous examination of SRM 1950 by the LIPID MAPS consortium. While the central theme of the interlaboratory study was to provide values to help harmonize lipids, lipid mediators, and precursor measurements across the community, it was also initiated to stimulate a discussion regarding areas in need of improvement.
Nature Communications, 2017
25Machine learning meets complex networks via coalescent embedding in the hyperbolic spaceAbstractpublications
Physicists recently observed that realistic complex networks emerge as discrete samples from a continuous hyperbolic geometry enclosed in a circle: the radius represents the node centrality and the angular displacement between two nodes resembles their topological proximity. The hyperbolic circle aims to become a universal space of representation and analysis of many real networks. Yet, inferring the angular coordinates to map a real network back to its latent geometry remains a challenging inverse problem. Here, we show that intelligent machines for unsupervised recognition and visualization of similarities in big data can also infer the network angular coordinates of the hyperbolic model according to a geometrical organization that we term “angular coalescence.” Based on this phenomenon, we propose a class of algorithms that offers fast and accurate “coalescent embedding” in the hyperbolic circle even for large networks. This computational solution to an inverse problem in physics of complex systems favors the application of network latent geometry techniques in disciplines dealing with big network data analysis including biology, medicine, and social science.
26Means and methods for treatment of early-onset Parkinson’s diseaseAbstractproducts
This application relates to the field of neurodegenerative diseases, more particularly to the field of Parkinson’s disease. In particular, the disclosure describes that inhibitors reducing FAS activity can be used for treatment of Parkinson’s disease, in particular, the treatment of patients suffering from Parkinson’s disease having loss of function mutations in PINK1 or PARKIN genes.
Science Advances, 2017
27ω-3 polyunsaturated fatty acids direct differentiation of the membrane phenotype in mesenchymal stem cells to potentiate osteogenesisAbstractpublications
Mammalian cells produce hundreds of dynamically regulated lipid species that are actively turned over and trafficked to produce functional membranes. These lipid repertoires are susceptible to perturbations from dietary sources, with potentially profound physiological consequences. However, neither the lipid repertoires of various cellular membranes, their modulation by dietary fats, nor their effects on cellular phenotypes have been widely explored. We report that differentiation of human mesenchymal stem cells (MSCs) into osteoblasts or adipocytes results in extensive remodeling of the plasma membrane (PM), producing cell-specific membrane compositions and biophysical properties. The distinct features of osteoblast PMs enabled rational engineering of membrane phenotypes to modulate differentiation in MSCs. Specifically, supplementation with docosahexaenoic acid (DHA), a lipid component characteristic of osteoblast membranes, induced broad lipidomic remodeling in MSCs that reproduced compositional and structural aspects of the osteoblastic PM phenotype. The PM changes induced by DHA supplementation potentiated osteogenic differentiation of MSCs concurrent with enhanced Akt activation at the PM. These observations prompt a model wherein the DHA-induced lipidome leads to more stable membrane microdomains, which serve to increase Akt activity and thereby enhance osteogenic differentiation. More broadly, our investigations suggest a general mechanism by which dietary fats affect cellular physiology through remodeling of membrane lipidomes, biophysical properties, and signaling.
Hormone and Metabolic Research, 2017
28Lipidomic Changes in Skeletal Muscle in Patients after Biliopancreatic DiversionAbstractpublications
The mechanisms behind the fast improvements of insulin sensitivity and release of the diabetic metabolic state after bariatric surgery are still not completely understood. To further elucidate the effects on the individual cellular level, we applied mass spectrometry to investigate the changes in the lipidomic profile of skeletal muscle cells before and after biliopancreatic diversion in six patients. We found a decrease in lipid storage species, mainly triacylglycerides (e. g., TAG 52:2 from 19.84 to 13.26 mol%; p=0.028), and an increase in structural and signaling lipids, including phosphatidylcholines [PC 36:2 (18:1/18:1) from 0.12 to 0.65 mol%; p=0.046], phosphatidylinositols (PI 36:2 from 0.008 to 0.039 mol%; p=0.046), and cardiolipins (CL 72:8 from 0.16 to 1.22 mol%; p=0.043). The proportional increase in structural lipids was directly and the decrease in TAGs was inversely correlated to improved post-operative insulin sensitivity, measured by euglycemic hyperinsulinemic clamp. Thus, short-term recovery of insulin sensitivity after biliopancreatic diversion may, beside gut hormonal adaptation, mechanical factors, shifts in the gut microbiome, and changes in bile acid and phospholipid metabolism, additionally be attributed to a metabolic recovery of skeletal muscle cells, reflected by normalization of the cellular lipidomic profile. Further studies are needed to investigate whether improved insulin sensitivity of skeletal muscle might be directly associated with the degradation of ectopic triglycerides, thereby reducing the reservoir of lipotoxic intermediates, which might interfere with insulin signaling and hamper mitochondrial metabolism.
Journal of Cell Science, 2017
29Iron affects Ire1 clustering propensity and the amplitude of endoplasmic reticulum stress signalingAbstractpublications
The unfolded protein response (UPR) allows cells to adjust secretory pathway capacity according to need. Ire1, the endoplasmic reticulum (ER) stress sensor and central activator of the UPR is conserved from the budding yeast Saccharomyces cerevisiae to humans. Under ER stress conditions, Ire1 clusters into foci that enable optimal UPR activation. To discover factors that affect Ire1 clustering, we performed a high-content screen using a whole-genome yeast mutant library expressing Ire1–mCherry. We imaged the strains following UPR induction and found 154 strains that displayed alterations in Ire1 clustering. The hits were enriched for iron and heme effectors and binding proteins. By performing pharmacological depletion and repletion, we confirmed that iron (Fe3+) affects UPR activation in both yeast and human cells. We suggest that Ire1 clustering propensity depends on membrane composition, which is governed by heme-dependent biosynthesis of sterols. Our findings highlight the diverse cellular functions that feed into the UPR and emphasize the cross-talk between organelles required to concertedly maintain homeostasis.
Biophysical Journal, 2017
30Miscibility Transition Temperature Scales with Growth Temperature in a Zebrafish Cell LineAbstractpublications
Cells can alter the lipid content of their plasma membranes upon changes in their environment to maintain and adjust membrane function. Recent work suggests that some membrane functions arise because cellular plasma membranes are poised close to a miscibility transition under growth conditions. Here we report experiments utilizing giant plasma membrane vesicles (GPMVs) to explore how membrane transition temperature varies with growth temperature in a zebrafish cell line (ZF4) that can be adapted for growth between 20 and 32°C. We find that GPMV transition temperatures adjust to be 16.7 +/- 1.2°C below growth temperature for four growth temperatures investigated and that adjustment occurs over roughly 2 days when temperature is abruptly lowered from 28 to 20°C. We also find that GPMVs have slightly different lipidomes when isolated from cells adapted for growth at 28 and 20°C. Similar to past work in vesicles derived from mammalian cells, fluctuating domains are observed in ZF4-derived GPMVs, consistent with their having critical membrane compositions. Taken together, these experimental results suggest that cells in culture biologically tune their membrane composition in a way that maintains specific proximity to a critical miscibility transition.
Molecular Metabolism, 2017
31The Munich MIDY Pig Biobank – A unique resource for studying organ crosstalk in diabetesAbstractpublications
The prevalence of diabetes mellitus and associated complications is steadily increasing. As a resource for studying systemic consequences of chronic insulin insufficiency and hyperglycemia, we established a comprehensive biobank of long-term diabetic INSC94Y transgenic pigs, a model of mutant INS gene-induced diabetes of youth (MIDY), and of wild-type (WT) littermates.
Female MIDY pigs (n = 4) were maintained with suboptimal insulin treatment for 2 years, together with female WT littermates (n = 5). Plasma insulin, C-peptide and glucagon levels were regularly determined using specific immunoassays. In addition, clinical chemical, targeted metabolomics, and lipidomics analyses were performed. At age 2 years, all pigs were euthanized, necropsied, and a broad spectrum of tissues was taken by systematic uniform random sampling procedures. Total beta cell volume was determined by stereological methods. A pilot proteome analysis of pancreas, liver, and kidney cortex was performed by label free proteomics.
MIDY pigs had elevated fasting plasma glucose and fructosamine concentrations, C-peptide levels that decreased with age and were undetectable at 2 years, and an 82% reduced total beta cell volume compared to WT. Plasma glucagon and beta hydroxybutyrate levels of MIDY pigs were chronically elevated, reflecting hallmarks of poorly controlled diabetes in humans. In total, ∼1900 samples of different body fluids (blood, serum, plasma, urine, cerebrospinal fluid, and synovial fluid) as well as ∼17,000 samples from ∼50 different tissues and organs were preserved to facilitate a plethora of morphological and molecular analyses. Principal component analyses of plasma targeted metabolomics and lipidomics data and of proteome profiles from pancreas, liver, and kidney cortex clearly separated MIDY and WT samples.
The broad spectrum of well-defined biosamples in the Munich MIDY Pig Biobank that will be available to the scientific community provides a unique resource for systematic studies of organ crosstalk in diabetes in a multi-organ, multi-omics dimension.
The FASEB Journal, 2017
32Lipin-1 regulation of phospholipid synthesis maintains endoplasmic reticulum homeostasis and is critical for triple-negative breast cancer cell survivalAbstractpublications
Cancer cells reprogram their metabolism to increase the synthesis of macromolecules for rapid proliferation. Compared to fatty acids, much less is known about the synthesis of phospholipids, which is essential for membrane biogenesis in cancer cells. We found that LPIN1, which encodes lipin-1, a phosphatidic acid phosphatase (PAP) controlling the rate-limiting step in the phospholipid synthesis pathway, is highly up-regulated in basal-like triple-negative breast cancer (TNBC). Moreover, high LPIN1 expression correlates with the poor prognosis of these patients. Knockdown of LPIN1 increases apoptosis in basal-like TNBC cell lines, whereas it has minimal or less effect on normal human mammary gland epithelial cells (HMECs) and estrogen receptor-positive breast cancer cell lines. Fatty acid incorporation and lipidomics analyses showed that LPIN1 knockdown blocks phospholipid synthesis and changes membrane lipid compositions that ultimately induce the activation of 1 of the 3 branches of unfolded protein responses, the inositol-requiring enzyme-1α pathway. We also show for the first time, to our knowledge, that lipin-1 knockdown significantly inhibits tumor growth in vivo using an orthotopic xenograft breast mouse model. Our results suggest that lipin-1 is a potential target for cancer therapy.
White Paper Series, 2017
33Big Data LipidomicsAbstractwhite papers
Lipidomics is the large-scale study of lipids in biological systems. The analysis of large datasets, potentially containing up to thousands of lipidomes, is a challenging endeavour. We have established multiparametric statistical approaches, tailored to quantify lipid data. These methods are geared to identify lipid biomarkers. In this white paper a cohort of healthy subjects is compared with a cohort of diseased persons to identify lipid signatures that discriminate health from disease. Such signatures could potentially be useful for disease stratification or for diagnosis by means of predictive modelling (machine learning).
In this white paper, we will guide you through the data analysis process aiming at the identification of lipid biomarkers and the evaluations of their performance.
Scientific Reports, 2017
34Heritability and responses to high fat diet of plasma lipidomics in a twin studyAbstractpublications
Lipidomics have a great potential as clinical tool for monitoring metabolic changes in health and disease. Nevertheless hardly anything is known about the heritability of lipids. Therefore, it is necessary to clarify how and how much we can affect these progresses in individuals. In our interventional twin study (46 healthy, non-obese twin pairs) we investigated the lipid profile in plasma samples after switching from a low fat diet to an isocaloric high fat diet (HFD) to characterize the metabolic adaptation. Additionally we used the ACE model for Additive genetics, Common and unique Environment as well as linear mixed modelling to analyse the heritability of lipids. The heritability of lipids varied between 0–62% and applied to lipid species rather than to lipid classes. Phospholipids showed the highest inheritance. In addition, sex, body mass index (BMI) and age were important modifiers. The lipid profile changed already after one week of HFD and diverged further after 5 weeks of additional HFD. Basal concentrations of specific lipids within phospholipids are strongly inherited and are likely to be associated with heritable disease risks. BMI, sex and age were major modifiers. Nutrition strongly alters specific lipid classes, and has to be controlled in clinical association studies.
35Methods and compositions of chondrisomesAbstractproducts
Mitochondria are membrane bound subcellular structures found in eukaryotic cells. Sometimes described as the power plants of cells, mitochondria generate most of the energy of the cell in the form of adenosine triphosphate (ATP) through respiration. Damage and subsequent dysfunction of mitochondria are important factors in a range of human diseases. Described herein are novel preparations of chondrisomes derived from mitochondria, and related methods, that have advantageous and surprising qualities for use in human pharmaceutical and in veterinary applications. Chondrisome preparations and methods described herein have beneficial structural characteristics, yield, concentration, stability, viability, integrity, or function, e.g. bioenergetic or biological function, for use in therapeutic applications.
Scientific Reports, 2017
36Enlightening discriminative network functional modules behind Principal Component Analysis separation in differential-omic science studiesAbstractpublications
Omic science is rapidly growing and one of the most employed techniques to explore differential patterns in omic datasets is principal component analysis (PCA). However, a method to enlighten the network of omic features that mostly contribute to the sample separation obtained by PCA is missing. An alternative is to build correlation networks between univariately-selected significant omic features, but this neglects the multivariate unsupervised feature compression responsible for the PCA sample segregation. Biologists and medical researchers often prefer effective methods that offer an immediate interpretation to complicated algorithms that in principle promise an improvement but in practice are difficult to be applied and interpreted. Here we present PC-corr: a simple algorithm that associates to any PCA segregation a discriminative network of features. Such network can be inspected in search of functional modules useful in the definition of combinatorial and multiscale biomarkers from multifaceted omic data in systems and precision biomedicine. We offer proofs of PC-corr efficacy on lipidomic, metagenomic, developmental genomic, population genetic, cancer promoteromic and cancer stem-cell mechanomic data. Finally, PC-corr is a general functional network inference approach that can be easily adopted for big data exploration in computer science and analysis of complex systems in physics.
Whitepaper Series, 2017
37Skin LipidomicsAbstractwhite papers
The lipid composition of human skin is essential for its function. However, the simultaneous quantification of a wide range of stratum corneum and sebaceous lipids is not trivial. We developed and validated a quantitative high-throughput shotgun mass spectrometry-based platform for lipid analysis of tape-stripped skin samples. Lipotype analyzes also other types of skin samples, from monolayers to 3D models. It is now easy to investigate how the healthy skin lipidome is composed, how it changes in diseases or upon intervention with a drug or a cosmetic product. This lipidomic data can be used for cosmetic claim support, topical drug development and personalized cosmetics.
Scientific Reports, 2017
38Large-scale human skin lipidomics by quantitative, high-throughput shotgun mass spectrometryAbstractpublications
The lipid composition of human skin is essential for its function; however the simultaneous quantification of a wide range of stratum corneum (SC) and sebaceous lipids is not trivial. We developed and validated a quantitative high-throughput shotgun mass spectrometry-based platform for lipid analysis of tape-stripped SC skin samples. It features coverage of 16 lipid classes; total quantification to the level of individual lipid molecules; high reproducibility and high-throughput capabilities. With this method we conducted a large lipidomic survey of 268 human SC samples, where we investigated the relationship between sampling depth and lipid composition, lipidome variability in samples from 14 different sampling sites on the human body and finally, we assessed the impact of age and sex on lipidome variability in 104 healthy subjects. We found sebaceous lipids to constitute an abundant component of the SC lipidome as they diffuse into the topmost SC layers forming a gradient. Lipidomic variability with respect to sampling depth, site and subject is considerable, and mainly accredited to sebaceous lipids, while stratum corneum lipids vary less. This stresses the importance of sampling design and the role of sebaceous lipids in skin studies.
PLOS ONE, 2017
39Lipidomic approach for stratification of acute myeloid leukemia patientsAbstractpublications
The pathogenesis and progression of many tumors, including hematologic malignancies is highly dependent on enhanced lipogenesis. De novo fatty-acid synthesis permits accelerated proliferation of tumor cells by providing membrane components but these may also alter physicochemical properties of lipid bilayers, which can impact signaling or even increase drug resistance in cancer cells. Cancer type-specific lipid profiles would permit us to monitor and interpret actual effects of lipid changes, potential fingerprints of individual tumors to be explored as diagnostic markers. We have used the shotgun MS approach to identify lipid patterns in different types of acute myeloid leukemia (AML) patients that either show no karyotype change or belong to t(8;21) or inv16 types. Differences in lipidomes of t(8;21) and inv(16) patients, as compared to AML patients without karyotype change, presented mostly as substantial modulation of ceramide/sphingolipid synthesis. Furthermore, between the t(8;21) and all other patients we observed significant changes in physicochemical membrane properties. These were related to a marked alteration in lipid saturation levels. The discovered differences in lipid profiles of various AML types improve our understanding of the pathobiochemical pathways involved and may serve in the development of diagnostic tools.
Scientific Reports, 2017
40A novel approach to analyze lysosomal dysfunctions through subcellular proteomics and lipidomics: the case of NPC1 deficiencyAbstractpublications
Superparamagnetic iron oxide nanoparticles (SPIONs) have mainly been used as cellular carriers for genes and therapeutic products, while their use in subcellular organelle isolation remains underexploited. We engineered SPIONs targeting distinct subcellular compartments. Dimercaptosuccinic acid-coated SPIONs are internalized and accumulate in late endosomes/lysosomes, while aminolipid-SPIONs reside at the plasma membrane. These features allowed us to establish standardized magnetic isolation procedures for these membrane compartments with a yield and purity permitting proteomic and lipidomic profiling. We validated our approach by comparing the biomolecular compositions of lysosomes and plasma membranes isolated from wild-type and Niemann-Pick disease type C1 (NPC1) deficient cells. While the accumulation of cholesterol and glycosphingolipids is seen as a primary hallmark of NPC1 deficiency, our lipidomics analysis revealed the buildup of several species of glycerophospholipids and other storage lipids in selectively late endosomes/lysosomes of NPC1-KO cells. While the plasma membrane proteome remained largely invariable, we observed pronounced alterations in several proteins linked to autophagy and lysosomal catabolism reflecting vesicular transport obstruction and defective lysosomal turnover resulting from NPC1 deficiency. Thus the use of SPIONs provides a major advancement in fingerprinting subcellular compartments, with an increased potential to identify disease-related alterations in their biomolecular compositions.
Journal of Cell Biology, 2017
41Cardiolipin promotes electron transport between ubiquinone and complex I to rescue PINK1 deficiencyAbstractpublications
PINK1 is mutated in Parkinson’s disease (PD), and mutations cause mitochondrial defects that include inefficient electron transport between complex I and ubiquinone. Neurodegeneration is also connected to changes in lipid homeostasis, but how these are related to PINK1-induced mitochondrial dysfunction is unknown. Based on an unbiased genetic screen, we found that partial genetic and pharmacological inhibition of fatty acid synthase (FASN) suppresses toxicity induced by PINK1 deficiency in flies, mouse cells, patient-derived fibroblasts, and induced pluripotent stem cell–derived dopaminergic neurons. Lower FASN activity in PINK1 mutants decreases palmitate levels and increases the levels of cardiolipin (CL), a mitochondrial inner membrane–specific lipid. Direct supplementation of CL to isolated mitochondria not only rescues the PINK1-induced complex I defects but also rescues the inefficient electron transfer between complex I and ubiquinone in specific mutants. Our data indicate that genetic or pharmacologic inhibition of FASN to increase CL levels bypasses the enzymatic defects at complex I in a PD model.
42Lipid-Sorting Specificity Encoded in K-Ras Membrane Anchor Regulates Signal OutputAbstractpublications
K-Ras is targeted to the plasma membrane by a C-terminal membrane anchor that comprises a farnesyl-cysteine-methyl-ester and a polybasic domain. We used quantitative spatial imaging and atomistic molecular dynamics simulations to examine molecular details of K-Ras plasma membrane binding. We found that the K-Ras anchor binds selected plasma membrane anionic lipids with defined head groups and lipid side chains. The precise amino acid sequence and prenyl group define a combinatorial code for lipid binding that extends beyond simple electrostatics; within this code lysine and arginine residues are non-equivalent and prenyl chain length modifies nascent polybasic domain lipid preferences. The code is realized by distinct dynamic tertiary structures of the anchor on the plasma membrane that govern amino acid side-chain-lipid interactions. An important consequence of this specificity is the ability of such anchors when aggregated to sort subsets of phospholipids into nanoclusters with defined lipid compositions that determine K-Ras signaling output.
Molecular Biology of the Cell, 2016
43Dissecting Torsin/cofactor function at the nuclear envelope: a genetic studyAbstractpublications
The human genome encodes four Torsin ATPases, the functions of which are poorly understood. In this study, we use CRISPR/Cas9 engineering to delete all four Torsin ATPases individually and in combination. Using nuclear envelope (NE) blebbing as a phenotypic measure, we establish a direct correlation between the number of inactivated Torsin alleles and the occurrence of omega-shaped herniations within the lumen of the NE. A similar, although not identical, redundancy is observed for LAP1 and LULL1, which serve as regulatory cofactors for a subset of Torsin ATPases. Unexpectedly, deletion of Tor2A in a TorA/B/3A-deficient background results in a stark increase of bleb formation, even though Tor2A does not respond to LAP1/LULL1 stimulation. The robustness of the observed phenotype in Torsin-deficient cells enables a structural analysis via electron microscopy tomography and a compositional analysis via immunogold labeling. Ubiquitin and nucleoporins were identified as distinctively localizing components of the omega-shaped bleb structure. These findings suggest a functional link between the Torsin/cofactor system and NE/nuclear pore complex biogenesis or homeostasis and establish a Torsin-deficient cell line as a valuable experimental platform with which to decipher Torsin function.
Journal of the American Heart Association, 2016
44Identification of Shared and Unique Serum Lipid Profiles in Diabetes Mellitus and Myocardial InfarctionAbstractpublications
Diabetes mellitus (DM) and cardiovascular disease are associated with dyslipidemia, but the detailed lipid molecular pattern in both diseases remains unknown.
We used shotgun mass spectrometry to determine serum levels of 255 molecular lipids in 316 controls, 171 DM, and 99 myocardial infarction (MI) events from a cohort derived from the Malmö Diet and Cancer study. Orthogonal projections to latent structures analyses were conducted between the lipids and clinical parameters describing DM or MI. Fatty acid desaturases (FADS) and elongation of very long chain fatty acid protein 5 (ELOVL5) activities were estimated by calculating product to precursor ratios of polyunsaturated fatty acids in complex lipids. FADS genotypes encoding these desaturases were then tested for association with lipid levels and ratios. Differences in the levels of lipids belonging to the phosphatidylcholine and triacylglyceride (TAG) classes contributed the most to separating DM from controls. TAGs also played a dominating role in discriminating MI from controls. Levels of C18:2 fatty acids in complex lipids were lower both in DM and MI versus controls (DM, P=0.004; MI, P=6.0E‐06) at least due to an acceleration in the metabolic flux from C18:2 to C20:4 (eg, increased estimated ELOVL5: DM, P=0.02; MI, P=0.04, and combined elongase‐desaturase activities: DM, P=3.0E‐06; MI, P=2.0E‐06). Minor allele carriers of FADS genotypes were associated with increased levels of C18:2 (P≤0.007) and lower desaturase activity (P≤0.002).
We demonstrate a possible relationship between decreased levels of C18:2 in complex lipids and DM or MI. We thereby highlight the importance of molecular lipids in the pathogenesis of both diseases.
The Journal of Physical Chemistry B, 2016
45Domain Stability in Biomimetic Membranes Driven by Lipid PolyunsaturationAbstractpublications
Biological membranes contain a broad variety of lipid species whose individual physicochemical properties and collective interactions ultimately determine membrane organization. A key aspect of the organization of cellular membranes is their lateral subdivision into domains of distinct structure and composition. The most widely studied membrane domains are lipid rafts, which are the biological manifestations of liquid-ordered phases that form in sterol-containing membranes. Detailed studies of biomimetic membrane mixtures have yielded wide-ranging insights into the physical principles behind lipid rafts; however, these simplified models do not fully capture the diversity and complexity of the mammalian lipidome, most notably in their exclusion of polyunsaturated lipids. Here, we assess the role of lipid acyl chain unsaturation as a driving force for phase separation using coarse-grained molecular dynamics (CGMD) simulations validated by model membrane experiments. The clear trends in our observations and good qualitative agreements between simulations and experiments support the conclusions that highly unsaturated lipids promote liquid–liquid domain stability by enhancing the differences in cholesterol content and lipid chain order between the coexisting domains. These observations reveal the important role of noncanonical biological lipids in the physical properties of membranes, showing that lipid polyunsaturation is a driving force for liquid–liquid phase separation.
46The anti-tumor drug 2-hydroxyoleic acid (Minerval) stimulates signaling and retrograde transportAbstractpublications
2-hydroxyoleic acid (OHOA, Minerval®) is an example of a substance used for membrane lipid therapy, where the cellular membranes rather than specific proteins constitute the therapeutical target. OHOA is thought to mediate its anti-tumor effect by affecting the biophysical properties of membranes, which leads to altered recruitment and activation of amphitropic proteins, altered cellular signaling, and eventual cell death. Little is known about the initial signaling events upon treatment with OHOA, and whether the altered membrane properties would have any impact on the dynamic intracellular transport system. In the present study we demonstrate that treatment with OHOA led to a rapid release of intracellular calcium and activation of multiple signaling pathways in HeLa cells, including the PI3K-AKT1-MTOR pathway and several MAP kinases, in a process independent of the EGFR. By lipidomics we confirmed that OHOA was incorporated into several lipid classes. Concomitantly, OHOA potently increased retrograde transport of the plant toxin ricin from endosomes to the Golgi and further to the endoplasmic reticulum. The OHOA-stimulated ricin transport seemed to require several amphitropic proteins, including Src, phospholipase C, protein kinase C, and also Ca2+/calmodulin. Interestingly, OHOA induced a slight increase in endosomal localization of the retromer component VPS35. Thus, our data show that addition of a lipid known to alter membrane properties not only affects signaling, but also intracellular transport.
Molecular Biology of the Cell, 2016
47Remodeling of the postsynaptic plasma membrane during neural developmentAbstractpublications
Neuronal synapses are the fundamental units of neural signal transduction and must maintain exquisite signal fidelity while also accommodating the plasticity that underlies learning and development. To achieve these goals, the molecular composition and spatial organization of synaptic terminals must be tightly regulated; however, little is known about the regulation of lipid composition and organization in synaptic membranes. Here we quantify the comprehensive lipidome of rat synaptic membranes during postnatal development and observe dramatic developmental lipidomic remodeling during the first 60 postnatal days, including progressive accumulation of cholesterol, plasmalogens, and sphingolipids. Further analysis of membranes associated with isolated postsynaptic densities (PSDs) suggests the PSD-associated postsynaptic plasma membrane (PSD-PM) as one specific location of synaptic remodeling. We analyze the biophysical consequences of developmental remodeling in reconstituted synaptic membranes and observe remarkably stable microdomains, with the stability of domains increasing with developmental age. We rationalize the developmental accumulation of microdomain-forming lipids in synapses by proposing a mechanism by which palmitoylation of the immobilized scaffold protein PSD-95 nucleates domains at the postsynaptic plasma membrane. These results reveal developmental changes in lipid composition and palmitoylation that facilitate the formation of postsynaptic membrane microdomains, which may serve key roles in the function of the neuronal synapse.
48Shotgun Lipidomics in der biomedizinischen und klinischen ForschungAbstractreviews
Shotgun lipidomics is the comprehensive and quantitative analysis of the lipid composition of biological and clinical samples. Here we describe the application and performance of the Lipotype shotgun lipidomics technology in clinical high throughput screening projects for the identification of disease-specific lipid patterns as well as in organ-wide analysis aiming at the systemic understanding of lipid-related physiological processes.
Plant Physiology, 2016
49Lack of FTSH4 Protease Affects Protein Carbonylation, Mitochondrial Morphology, and Phospholipid Content in Mitochondria of Arabidopsis: New Insights into a Complex InterplayAbstractpublications
FTSH4 is one of the inner membrane-embedded ATP-dependent metalloproteases in mitochondria of Arabidopsis (Arabidopsis thaliana). In mutants impaired to express FTSH4, carbonylated proteins accumulated and leaf morphology was altered when grown under a short-day photoperiod, at 22°C, and a long-day photoperiod, at 30°C. To provide better insight into the function of FTSH4, we compared the mitochondrial proteomes and oxyproteomes of two ftsh4 mutants and wild-type plants grown under conditions inducing the phenotypic alterations. Numerous proteins from various submitochondrial compartments were observed to be carbonylated in the ftsh4 mutants, indicating a widespread oxidative stress. One of the reasons for the accumulation of carbonylated proteins in ftsh4 was the limited ATP-dependent proteolytic capacity of ftsh4 mitochondria, arising from insufficient ATP amount, probably as a result of an impaired oxidative phosphorylation (OXPHOS), especially complex V. In ftsh4, we further observed giant, spherical mitochondria coexisting among normal ones. Both effects, the increased number of abnormal mitochondria and the decreased stability/activity of the OXPHOS complexes, were probably caused by the lower amount of the mitochondrial membrane phospholipid cardiolipin. We postulate that the reduced cardiolipin content in ftsh4 mitochondria leads to perturbations within the OXPHOS complexes, generating more reactive oxygen species and less ATP, and to the deregulation of mitochondrial dynamics, causing in consequence the accumulation of oxidative damage.
Developmental Cell, 2016
50Torsins Are Essential Regulators of Cellular Lipid MetabolismAbstractpublications
Torsins are developmentally essential AAA+ proteins, and mutation of human torsinA causes the neurological disease DYT1 dystonia. They localize in the ER membranes, but their cellular function remains unclear. We now show that dTorsin is required in Drosophila adipose tissue, where it suppresses triglyceride levels, promotes cell growth, and elevates membrane lipid content. We also see that human torsinA at the inner nuclear membrane is associated with membrane expansion and elevated cellular lipid content. Furthermore, the key lipid metabolizing enzyme, lipin, is mislocalized in dTorsin-KO cells, and dTorsin increases levels of the lipin substrate, phosphatidate, and reduces the product, diacylglycerol. Finally, genetic suppression of dLipin rescues dTorsin-KO defects, including adipose cell size, animal growth, and survival. These findings identify that torsins are essential regulators of cellular lipid metabolism and implicate disturbed lipid biology in childhood-onset DYT1 dystonia.
Biophysical Journal, 2016
51Polyunsaturated Lipids Regulate Membrane Domain Stability by Tuning Membrane OrderAbstractpublications
The plasma membrane (PM) serves as the functional interface between a cell and its environment, hosting extracellular signal transduction and nutrient transport among a variety of other processes. To support this extensive functionality, PMs are organized into lateral domains, including ordered, lipid-driven assemblies termed lipid rafts. Although the general requirements for ordered domain formation are well established, how these domains are regulated by cell-endogenous mechanisms or exogenous perturbations has not been widely addressed. In this context, an intriguing possibility is that dietary fats can incorporate into membrane lipids to regulate the properties and physiology of raft domains. Here, we investigate the effects of polyunsaturated fats on the organization of membrane domains across a spectrum of membrane models, including computer simulations, synthetic lipid membranes, and intact PMs isolated from mammalian cells. We observe that the ω-3 polyunsaturated fatty acid docosahexaenoic acid is robustly incorporated into membrane lipids, and this incorporation leads to significant remodeling of the PM lipidome. Across model systems, docosahexaenoic acid-containing lipids enhance the stability of ordered raft domains by increasing the order difference between them and coexisting nonraft domains. The relationship between interdomain order disparity and the stability of phase separation holds for a spectrum of different perturbations, including manipulation of cholesterol levels and high concentrations of exogenous amphiphiles, suggesting it as a general feature of the organization of biological membranes. These results demonstrate that polyunsaturated fats affect the composition and organization of biological membranes, suggesting a potential mechanism for the extensive effects of dietary fat on health and disease.
Nature Cell Biology, 2016
52Control of plasma membrane lipid homeostasis by the extended synaptotagminsAbstractpublications
Acute metabolic changes in plasma membrane (PM) lipids, such as those mediating signalling reactions, are rapidly compensated by homeostatic responses whose molecular basis is poorly understood. Here we show that the extended synaptotagmins (E-Syts), endoplasmic reticulum (ER) proteins that function as PtdIns(4,5)P2– and Ca2+-regulated tethers to the PM, participate in these responses. E-Syts transfer glycerolipids between bilayers in vitro, and this transfer requires Ca2+ and their lipid-harbouring SMP domain. Genome-edited cells lacking E-Syts do not exhibit abnormalities in the major glycerolipids at rest, but exhibit enhanced and sustained accumulation of PM diacylglycerol following PtdIns(4,5)P2 hydrolysis by PLC activation, which can be rescued by expression of E-Syt1, but not by mutant E-Syt1 lacking the SMP domain. The formation of E-Syt-dependent ER–PM tethers in response to stimuli that cleave PtdIns(4,5)P2 and elevate Ca2+ may help reverse accumulation of diacylglycerol in the PM by transferring it to the ER for metabolic recycling.
BBA Biomembranes, 2016
53Glycosylphosphatidylinositol-anchored proteins: Membrane organization and transportAbstractreviews
Glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs) are a class of membrane proteins containing a soluble protein attached by a conserved glycolipid anchor to the external leaflet of the plasma membrane. In polarized epithelial cells, GPI-APs are predominantly sorted to the apical surface in the trans-Golgi network (TGN) by clustering in sphingolipid- and cholesterol-dependent microdomains (or rafts), which have been proposed to act as apical sorting platforms. Recent data indicate that the mechanisms of GPI-AP sorting, occurring in the Golgi, control both the membrane transport of GPI-APs and their specific activity at the apical surface of fully polarized epithelial cells. Here, we discuss the most recent findings and the factors regulating apical sorting of GPI-APs at the Golgi in polarized epithelial cells. We also underline the differences in the plasma membrane organization of GPI-APs between polarized and non-polarized cells supporting the existence of various mechanisms that control GPI-AP organization in different cell types.
BBA Biomembranes, 2016
54Cell membranes: A subjective perspectiveAbstractreviews
Cell membranes have developed a tremendous complexity of lipids and proteins geared to perform the functions cells require. The lipids have for long remained in the background and are now regaining their role as important building blocks of cells. Their main function is to form the matrix of our cell membranes where they support a variety of functions essential for life. This 2-dimensional fluid matrix has evolved unexpected material properties that involve both lipid-lipid and lipid-protein interactions. This perspective is a short summary of the challenges that this field faces and discusses potential ways and means for coming to grips with the properties of this incredible fluid.
Methods in Molecular Biology, 2016
55Profiling of Yeast Lipids by Shotgun LipidomicsAbstractreviews
Lipidomics is a rapidly growing technology for identification and quantification of a variety of cellular lipid molecules. Following the successful development and application of functional genomic technologies in yeast Saccharomyces cerevisiae, we witness a recent expansion of lipidomics applications in this model organism. The applications include detailed characterization of the yeast lipidome as well as screening for perturbed lipid phenotypes across hundreds of yeast gene deletion mutants. In this chapter, we describe sample handling, mass spectrometry, and bioinformatics methods developed for yeast lipidomics studies.
European Journal of Lipid Science and Technology, 2015
56An automated shotgun lipidomics platform for high throughput, comprehensive, and quantitative analysis of blood plasma intact lipidsAbstractpublications
Blood plasma has gained protagonism in lipidomics studies due to its availability, uncomplicated collection and preparation, and informative readout of physiological status. At the same time, it is also technically challenging to analyze due to its complex lipid composition affected by many factors, which can hamper the throughput and/or lipidomics coverage. To tackle these issues, we developed a comprehensive, high throughput, and quantitative mass spectrometry‐based shotgun lipidomics platform for blood plasma lipid analyses. The main hallmarks of this technology are (i) it is comprehensive, covering 22 quantifiable different lipid classes encompassing more than 200 lipid species; (ii) it is amenable to high‐throughput, with less than 5 min acquisition time allowing the complete analysis of 200 plasma samples per day; (iii) it achieves absolute quantification, by inclusion of internal standards for every lipid class measured; (iv) it is highly reproducible, achieving an average coefficient of variation of <10% (intra‐day), approx. 10% (inter‐day), and approx. 15% (inter‐site) for most lipid species; (v) it is easily transferable allowing the direct comparison of data acquired in different sites. Moreover, we thoroughly assessed the influence of blood stabilization with different anticoagulants and freeze‐thaw cycles to exclude artifacts generated by sample preparation.
Product development, 2014
57Lipid analysis of microorganisms for production of ingredients for the food, beverage and consumer health sectorsAbstractproducts
Evolva has a proprietary, fermentation-based platform that allows radically different approaches to the production of ingredients for the food, beverage and consumer health sectors. As a pioneer and global leader in sustainable, fermentation-based approaches to ingredients, Evolva was interested in the quantitative analysis of the lipid composition of yeast cells and detailed information on the structural and quantitative lipid composition of yeast cells. The information on the lipid composition facilitated strain optimization and adjustments of culture conditions to ensure maximal production efficiency for the compound in question.
Current Opinion in Cell Biology, 2013
58Organellar lipidomics: background and perspectivesAbstractreviews
The basic structural units of eukaryotic cells are membrane-bound organelles and many essential cellular processes take place in and on membranes. It is becoming increasingly clear that these processes are influenced by the biophysical properties of the organelle membranes, which in turn are affected by their lipid composition. Even subtle changes in lipid composition can have a tremendous impact on membrane properties and the processes occurring within them. Therefore, in order to understand the contribution of membrane lipid composition to the functionality of membrane-bound cellular processes, comprehensive structural and quantitative information on the organellar lipidome is essential. Here we argue that only mass spectrometry-based organellar lipidomics can provide this information today.
PLOS One, 2012
59LipidXplorer: a software for consensual cross-platform lipidomicsAbstractpublications
LipidXplorer is the open source software that supports the quantitative characterization of complex lipidomes by interpreting large datasets of shotgun mass spectra. LipidXplorer processes spectra acquired on any type of tandem mass spectrometers; it identifies and quantifies molecular species of any ionizable lipid class by considering any known or assumed molecular fragmentation pathway independently of any resource of reference mass spectra. It also supports any shotgun profiling routine, from high throughput top-down screening for molecular diagnostic and biomarker discovery to the targeted absolute quantification of low abundant lipid species.
60Cell membranes: the lipid perspectiveAbstractreviews
Although cell membranes are packed with proteins mingling with lipids, remarkably little is known about how proteins interact with lipids to carry out their function. Novel analytical tools are revealing the astounding diversity of lipids in membranes. The issue is now to understand the cellular functions of this complexity. In this Perspective, we focus on the interface of integral transmembrane proteins and membrane lipids in eukaryotic cells. Clarifying how proteins and lipids interact with each other will be important for unraveling membrane protein structure and function. Progress toward this goal will be promoted by increasing overlap between different fields that have so far operated without much crosstalk.
Genome Biology, 2011
61A novel informatics concept for high-throughput shotgun lipidomics based on the molecular fragmentation query languageAbstractpublications
Shotgun lipidome profiling relies on direct mass spectrometric analysis of total lipid extracts from cells, tissues or organisms and is a powerful tool to elucidate the molecular composition of lipidomes. We present a novel informatics concept of the molecular fragmentation query language implemented within the LipidXplorer open source software kit that supports accurate quantification of individual species of any ionizable lipid class in shotgun spectra acquired on any mass spectrometry platform.
Nature reviews molecular cell biology, 2010
62Revitalizing membrane rafts: new tools and insightsAbstractreviews
Ten years ago, we wrote a Review on lipid rafts and signalling in the launch issue of Nature Reviews Molecular Cell Biology. At the time, this field was suffering from ambiguous methodology and imprecise nomenclature. Now, new techniques are deepening our insight into the dynamics of membrane organization. Here, we discuss how the field has matured and present an evolving model in which membranes are occupied by fluctuating nanoscale assemblies of sphingolipids, cholesterol and proteins that can be stabilized into platforms that are important in signalling, viral infection and membrane trafficking.
Nature reviews molecular cell biology, 2010
63Lipidomics: coming to grips with lipid diversityAbstractreviews
Although lipids are biomolecules with seemingly simple chemical structures, the molecular composition of the cellular lipidome is complex and, currently, poorly understood. The exact mechanisms of how compositional complexity affects cell homeostasis and its regulation also remain unclear. This emerging field is developing sensitive mass spectrometry technologies for the quantitative characterization of the lipidome. Here, we argue that lipidomics will become an essential tool kit in cell and developmental biology, molecular medicine and nutrition.
nature reviews drug discovery, 2010
64Subcellular targeting strategies for drug design and deliveryAbstractreviews
Many drug targets are localized to particular subcellular compartments, yet current drug design strategies are focused on bioavailability and tissue targeting and rarely address drug delivery to specific intracellular compartments. Insights into how the cell traffics its constituents to these different cellular locations could improve drug design. In this Review, we explore the fundamentals of membrane trafficking and subcellular organization, as well as strategies used by pathogens to appropriate these mechanisms and the implications for drug design and delivery.
65Lipid rafts as a membrane-organizing principleAbstractreviews
Cell membranes display a tremendous complexity of lipids and proteins designed to perform the functions cells require. To coordinate these functions, the membrane is able to laterally segregate its constituents. This capability is based on dynamic liquid-liquid immiscibility and underlies the raft concept of membrane subcompartmentalization. Lipid rafts are fluctuating nanoscale assemblies of sphingolipid, cholesterol, and proteins that can be stabilized to coalesce, forming platforms that function in membrane signaling and trafficking. Here we review the evidence for how this principle combines the potential for sphingolipid-cholesterol self-assembly with protein specificity to selectively focus membrane bioactivity.