Structure. Tetrasialogangliosides (GQ, or GQ1) belong to the group of gangliosides within the sphingolipids. Their structure consists of a ceramide backbone linked to an oligosaccharide unit made of eight sugar molecules. Four of the sugar molecules are sialic acids. The ceramide backbone of tetrasialogangliosides contains two hydrocarbon chains: a long-chain base which is linked to a fatty acid via an amide bond. The fatty acid and the long-chain base can be of variable length, hydroxylated, and contain double bonds.
Function. Tetrasialogangliosides, or GQ1 gangliosides, belong to the major gangliosides of the mammal brain. In Miller Fisher syndrome, a rare autoimmune nerve disease that is considered to be a variant of Guillain-Barré syndrome, patients have a unique antibody against GQ1 lipids. Patients experience paralysis of ocular muscles, absence of reflexes, and lack of voluntary coordination of muscle movements. Further, GQ1 levels are reduced in Alzheimer’s models.
