Anti-Globoside GL4 polyclonal antibody

Glycosphingolipids (GSLs) have a sugar or two attached to a sphingolipid moiety (usually ceramide). They are further separated into acidic, basic and amphoteric glycosphingolipids. The globo class of glycan antigens are carbohydrate antigen molecules on the surface of cells that are responsible for physiological processes like recognition of cell signals. This series includes Gb3, Gb4, Gb5, and Globo-H, among others. Gb4 refers to the glycan portion of globotetraosylceramide (Gb4Cer). It is formed by adding GalNAc to the terminal galactose of Gb3. Gb4Cer, or the P antigen, is strongly expressed on the surface of human colon epithelial cells and binds to Shiga toxin (Stx) from E. coli O157:H7.

Stx is known to be one of the most potent biological toxins, comprising two immunologically distinct groups. Stx1a and Stx2a interact with both Gb3 and Gb4, although their interaction with Gb4 is weaker. In contrast, Stx2e has a stronger binding affinity for Gb4 than for Gb3. The Galα1,4Gal sequence present in these interactions has been confirmed as the minimal structure recognized by the PapG adhesin at the tips of pili in uropathogenic Escherichia coli, making it a potential candidate for the development of toxin neutralizers or anti-adhesion agents. Further modifications or derivatives of Gb4 can yield Gb5, SSEA-4, and Globo-H, which are specifically expressed on cancer cells and are involved in processes such as tumor metastasis and signal recognition. Researchers have also identified non-acidic glycosphingolipids of the globo series, including Gb4, Gb5/SSEA-3, and Globo-H, in human embryonic stem cells (hESC).

Figure 1. Structure of Gb4Cer
(Source: Farwanah H, et al. 2012)

GSLs are mostly present in lipid rafts in the plasma membrane of vertebrate brains and spinal cords, along with cholesterol and proteins. Its hydrophobic ceramide arm keeps GSLs on the membrane, while its hydrophilic glycan chains can dangle far into the space outside of the cell to bind to other membrane- and extracellular carbohydrate-binding proteins. The biosynthesis, degradation and cytoplasmic transport of GSLs is tightly monitored in the grand scheme of things, since glycolipids play a number of key cell-specific roles. The loss of GSL homeostasis can cause severe pathological outcomes and other metabolic disorders. Sphingolipidoses are a lysosomal storage disease where GSLs build up. This builds up beyond the cell's normal storage capacity, causing membrane changes in many organs and abnormal lipid vesicles. GM2 gangliosidosis is a class of LSD characterized by a deficiency of β-hexosaminidase, which prevents the cleavage of GalNAcβ residues in GM2, GD2, GT2, and Gb4. Alongside GM2 gangliosides, Gb4Cer is a major storage material in Sandhoff disease.

Rabbit Anti-Gb4 polyclonal antibody
Rabbit Anti-globotetraosylceramide polyclonal antibody