Ganglioside GM1 binding toxins and human neuropathy-associated IgM antibodies differentially promote neuritogenesis in a PC12 assay.
PC12 cells undergo neuritogenesis upon nerve growth factor (NGF) activation of the TrkA receptor, an effect mimicked by the ganglioside GM1 binding B-subunit of cholera toxin (CTB). Modulation of neuritogenesis by a GM1 ligand indicates a possible pathway for pathophysiological actions of neuropathy-associated anti-GM1 antibodies. Here we examine the ability of GM1 binding toxins and antibodies to induce neuritogenesis, using a PC12 neurite outgrowth assay. Cholera toxin (CT) and commercially prepared CTB (sCTB, contaminated with traces of the adenyl cyclase activating CT A-subunit) were highly neuritogenic. Recombinant cholera toxin B-subunit (rCTB, free from CTA) induced a much smaller effect, suggesting that the potent effects of sCTB are largely due to contaminating CTA. The recombinant GM1 binding B-subunit of Escherichia coli heat-labile enterotoxin (rETxB) exhibited no neuritogenic activity, whilst rETx holotoxin, which activates adenyl cyclase, was highly neuritogenic. Monoclonal anti-GM1 IgM antibodies from human neuropathy subjects induced small neuritogenic effects. These data indicate that GM1/ligand interaction does not necessarily lead to neuritogenesis and suggest that a specialisation of CTB, not shared by anti-GM1 antibodies or rETxB, is required to activate TrkA. Our data also indicate that antibodies are unlikely to exert major modulatory effects on TrkA activity in patients with anti-GM1 antibody-associated peripheral neuropathies.
O'Hanlon
Graham M
GM
University Department of Neurology, Institute of Neurological Sciences, Southern General Hospital, Glasgow G51 4TF, Scotland, UK.
Hirst
Timothy R
TR
Willison
Hugh J
HJ
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001667:Binding, Competitive; D002772:Cholera Toxin / Q000378:metabolism / Q000494:pharmacology*; D004340:Drug Contamination; D004768:Enterotoxins / Q000494:pharmacology; D004926:Escherichia coli / Q000378:metabolism; D005677:G(M1) Ganglioside / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007075:Immunoglobulin M / Q000494:pharmacology*; D016501:Neurites / Q000187:drug effects*; D016716:PC12 Cells; D010523:Peripheral Nervous System Diseases / Q000276:immunology; D051381:Rats; D020917:Receptor, trkA / Q000187:drug effects / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D004768:Enterotoxins; D007075:Immunoglobulin M; D005677:G(M1) Ganglioside; D002772:Cholera Toxin; D020917:Receptor, trkA