Gangliosides cholera toxin binding

Holmgren, J. Mansson, J.-E. Svennerholm, L. Tissue receptor for cholera enterotoxin Structural requirements of GM1 ganglioside in toxin binding and inactivation. Medical Biology, 1971, 52, 229-233. 

Ganser AL, Kirsclmer DA, Willinger M (1983) Ganglioside localization on myelinated nei ve fibres by cholera toxin binding. J Neur ocytol 12 921-938. 

Gangliosides are receptors for specific agents, such as cholera toxin and influenza virus. Cholera toxin binds to ganglioside GMl, whereas influenza virus recognizes the sialic acid portion of certain gangliosides. The influenza virus then cleaves the gangliosides as part of its entry process into cells. 

Stevens, R., Cholera toxin binding affinity and specificity for gangliosides determined by surface plasmon resonance. Biochemistry, 35, 6375-6380 (1996). 

Two of the most widely spread and well-studied enterotoxigenic forms of bacterial diarrhea are ETEC and Vibrio cholerae. The toxins they produce, labile toxin (LT) and cholera toxin (CT) respectively, are very similar in primary sequence, structure, and mechanism of action [72]. They are homologous multi-subunit proteins in which the non-toxic B subunit mediates GMj ganglioside binding, and thus are candidates for vaccines that can neutralize toxin activity. 

Caveolae can mediate the delivery of CtxB that binds to GM1 ganglioside at the plasma membrane and is delivered to intracellular compartments. Cholera toxin, produced by Vibrio cholerae, consists of five identical subunits B and one A chain. In addition to labeled SV40 and caveolin-1-GFP, CtxB is one of the most commonly used caveolae markers. However, two groups reported that the toxin is internalized by either a clathrin-independent caveolae pathway or a clathrin-dependent uptake, bringing its selectivity/specificity into question (31,81,118). We controlled the suitability of this marker for COS-7 cells pretreated with CPZ, mpCD, and filipin and as expected, the uptake was not influenced by CPZ treatment but was strongly decreased by the latter two (data not shown). 

In both of these cases, the ligand (sialic acid) for the analyte of interest (influenza vims) was covalently linked to the PDA backbone generated upon photopolymerization. Functional sensors based on ligands that are noncovalently incorporated into liposomes have also been reported (Charych et al. 1996 Pan and Charych 1997). Mixed liposomes as well as mixed thin films on glass containing a combination of the ganglioside GMl and diacetylene lipids detect the presence of cholera toxin, a protein that binds to GMl. 

Figure 7-5 Stereoscopic view of the B5 pentamer of cholera toxin B. The pentamer, known as choleragenoid, has a central hole of 1.5 nm diameter into which a helix from the A subunit is inserted. As viewed here, the front surface of the pentamer has binding sites for the oligosaccharide chains of ganglioside CM, which serves as the toxin receptor. The back side binds the A subunit. See also Box 11-A. From Zhang et al,31...

Cholera toxin consists of one 240-residue A subunit and a ring of five 103-residue B subunits.c e The latter is a "targeting complex," a bacterial lectin each subunit of which binds to the galactose and sialic acid termini of a single molecule of ganglioside Gm1. 

Ellipsometry can follow the interactions between two types of biological macromolecules, the first of those two bound physically to the surface, the other acting from the solution. The binding of conconavalin A to adsorbed mannan 180) and of cholera toxin to adsorbed ganglioside t83) are examples. The adsorption of complement factors to an antibody-coated surface was monitored by ellipsometry and a modification of the same method was used for quantification of migration inhibition of human polymorphonuclear leucocytes 182). Interaction of proteins and cells with affinity ligands covalently coupled to silicon surfaces has been also studied 183). 

Chemical modifications of cholera toxins by means of various reagents were consistently found to affect binding to cells and to GM1 ganglioside to the same extent (lU). 

Figure 5. Effect of hydrolysis of plastic-attached gangliosides with V. cholerae sialidase on their binding capacity for tetanus (%) and cholera toxins as determined by ganglioside-ELlSA method...

Williams TL, Jenkins ATA (2008) Measurement of the binding of cholera toxin to GM1 gangliosides on solid supported lipid bilayer vesicles and inhibition by europium (III) chloride. J Am Chem Soc 130 6438-6443... 

Magnani JL, Smith DE, Ginsburg V. Detection of gangliosides that bind cholera toxin direct binding of 1251-labeled toxin to thin-layer chromatograms. Anal. Biochem. 1980 109 399 02. 

We consider here some pathologies of the G-protein-dependent signal pathways. Let us first consider the mechanism of action of the cholera toxin, secreted by the intestinal bacterium Vibrio cholera. Cholera is an acute diarrheal disease that can be life threatening. It causes voluminous secretion of electrolytes and fluids from the intestines of infected persons. The cholera toxin, choleragen, is a protein composed of two functional units—a B subunit that binds to gangliosides of the intestinal epithelium and a catalytic A subunit that enters the cell. The A subunit... 

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