English

Noun

1. Any of several galactocerebrosides found in the surface membranes of nerve cells

Ganglioside is a compound composed of a glycosphingolipid (ceramide and oligosaccharide) with one or more sialic acids (AKA n-acetylneuraminic acid) linked on the sugar chain. The 40+ known gangliosides differ mainly in the position and number of NANA residues.

It is a component of the cell plasma membrane which modulates cell signal transduction events. It appears they concentrate in lipid rafts.

They have recently been found to be highly important in immunology. Natural and semisynthetic gangliosides are considered possible therapeutics for neurodegenerative disorders.

Haemagglutinin of Influenza virus exploits certain gangliosides to enter and infect the cells expressing them.

Gangliosides are more complex glycosphingolipids in which oligosaccharide chains containing N-acetylneuraminic acid (NeuNAc) are attached to a ceramide. NeuNAc, an acetylated derivative of the carbohydrate sialic acid, makes the head groups of Gangliosides anionic. NB: the M in GM2 stands for monosialo i.e. one NeuNAc residue. GM2 was the second monosialo ganglioside characterized, thus the subscript 2. Their structural diversity results from variation in the composition and sequence of the sugar residues. In all Gangliosides the ceramide is linked through its C-1 to a β-glucosyl residue which in turn is bound to a β-galactosyl residue.

Where are Gangliosides found?

They are present on cell surfaces, with the 2 hydrocarbon chains of the ceramide moiety embedded in the plasma membrane and the oligosaccharides on the extracellular surface. They are found predominantly in the nervous system where they constitute 6% of all phospholipids.

They are involved in diverse roles including cell to cell contact, ion conductance, and receptor.

Tay-Sachs Disease is caused by a build up of gangliosides due to a non functioning B-N-acetyl hexosaminidase.

Function

Gangliosides, glycosphingolipids and glycoproteins found on the surface of oligosaccharide provide cells with distinguishing surface markers that can serve in cellular recognition and cell-to-cell communication. Structures similar to the ABO blood group antigens on the surface of human cells can be oligosaccharide components of glycosphingolipids in addition to being linked to proteins to form glycoproteins.

Common gangliosides

• One NANA ("M")
  • GM1
  • GM2
  • GM3

• Two NANAs ("D")
  • GD1a
  • GD1b
  • GD2
  • GD3

• Three NANAs ("T")
  • GT1b

• Four NANAs ("Q")
  • GQ1

structures of the common gangliosides

GM2-1 = aNeu5Ac(2-3)bDGalp(1-?)bDGalNAc(1-?)bDGalNAc(1-?)bDGlcp(1-1)Cer GM3 = aNeu5Ac(2-3)bDGalp(1-4)bDGlcp(1-1)Cer GM2,GM2a(?) = bDGalpNAc(1-4)[aNeu5Ac(2-3)]bDGalp(1-4)bDGlcp(1-1)Cer GM2b(?) = aNeu5Ac(2-8)aNeu5Ac(2-3)bDGalp(1-4)bDGlcp(1-1)Cer GM1,GM1a = bDGalp(1-3)bDGalNAc[aNeu5Ac(2-3)]bDGalp(1-4)bDGlcp(1-1)Cer asialo-GM1,GA1 = bDGalp(1-3)bDGalpNAc(1-4)bDGalp(1-4)bDGlcp(1-1)Cer asialo-GM2,GA2 = bDGalpNAc(1-4)bDGalp(1-4)bDGlcp(1-1)Cer GM1b = aNeu5Ac(2-3)bDGalp(1-3)bDGalNAc(1-4)bDGalp(1-4)bDGlcp(1-1)Cer GD3 = aNeu5Ac(2-8)aNeu5Ac(2-3)bDGalp(1-4)bDGlcp(1-1)Cer GD2 = bDGalpNAc(1-4)[aNeu5Ac(2-8)aNeu5Ac(2-3)]bDGalp(1-4)bDGlcp(1-1)Cer GD1a = aNeu5Ac(2-3)bDGalp(1-3)bDGalNAc(1-4)[aNeu5Ac(2-3)]bDGalp(1-4)bDGlcp(1-1)Cer GD1alpha = aNeu5Ac(2-3)bDGalp(1-3)bDGalNAc(1-4)[aNeu5Ac(2-6)]bDGalp(1-4)bDGlcp(1-1)Cer GD1b = bDGalp(1-3)bDGalNAc(1-4)[aNeu5Ac(2-8)aNeu5Ac(2-3)]bDGalp(1-4)bDGlcp(1-1)Cer GT1a = aNeu5Ac(2-8)aNeu5Ac(2-3)bDGalp(1-3)bDGalNAc(1-4)[aNeu5Ac(2-3)]bDGalp(1-4)bDGlcp(1-1)Cer GT1,GT1b = aNeu5Ac(2-3)bDGalp(1-3)bDGalNAc(1-4)[aNeu5Ac(2-8)aNeu5Ac(2-3)]bDGalp(1-4)bDGlcp(1-1)Cer OAc-GT1b = aNeu5Ac(2-3)bDGalp(1-3)bDGalNAc(1-4)aXNeu5Ac9Ac(2-8)aNeu5Ac(2-3)]bDGalp(1-4)bDGlcp(1-1)Cer GT1c = bDGalp(1-3)bDGalNAc(1-4)[aNeu5Ac(2-8)aNeu5Ac(2-8)aNeu5Ac(2-3)]bDGalp(1-4)bDGlcp(1-1)Cer GT3 = aNeu5Ac(2-8)aNeu5Ac(2-8)aNeu5Ac(2-3)bDGal(1-4)bDGlc(1-1)Cer GQ1b = aNeu5Ac(2-8)aNeu5Ac(2-3)bDGalp(1-3)bDGalNAc(1-4)[aNeu5Ac(2-8)aNeu5Ac(2-3)]bDGalp(1-4)bDGlcp(1-1)Cer GGal = aNeu5Ac(2-3)bDGalp(1-1)Cer

where aNeu5Ac = 5-acetyl-alpha-neuraminic acid aNeu5Ac9Ac = 5,9-diacetyl-alpha-neuraminic acid bDGalp = beta-D-galactopyranose bDGalpNAc = N-acetyl-beta-D-galactopyranose bDGlcp = beta-D-glucopyranose Cer = ceramide (general N-acylated sphingoid)

References

External links

• Overview of gangliosides at lipidlibrary.co.uk
• Overview of gangliosides at cyberlipid.org