title: Regulation of transmembrane signaling by ganglioside GM1: interaction of anti-GM1 with Neuro2a cells.
abstract: Interaction of antibodies to ganglioside GM1 with Neuro2a cells was studied to investigate the role of GM1 in cell signaling. Binding of anti-GM1 to Neuro2a cells induced the formation of 3H-inositol phosphates (3H-IPs) and elevated the intracellular Ca2+ concentration [Ca2+]i. The rise in [Ca2+]i was due to the influx of Ca2+ from the extracellular medium and release from intracellular Ca2+ pools. The Ca2+ influx pathway did not allow the permeation of Na+ or K+. The influx was inhibited by amiloride, a specific blocker of T-type Ca2+ channels, whereas nifedipine and diltiazem, blockers of L-type Ca2+ channels, did not have any effect. Thus, anti-GM1 appears to activate a T-type Ca2+ channel in Neuro2a cells. The intracellular Ca2+ release was inhibited by pretreatment of cells with neomycin sulfate, phorbol dibutyrate, and pertussis toxin (PTx), which also inhibited the 3H-IP formation in Neuro2a cells. Addition of caffeine neither elevated the [Ca2+]i nor affected the anti-GM1-induced [Ca2+]i rise. The data reveal that the binding of anti-GM1 to Neuro2a cells activates phospholipase C via a PTx-sensitive G protein, which leads to formation of IPs and release of Ca2+ from inositol trisphosphate-sensitive pool of endoplasmic reticulum. Anti-GM1 also arrested the differentiation of Neuro2a cells in culture and significantly stimulated their proliferation. This stimulatory effect of anti-GM1 on cell proliferation was blocked by amiloride but not by PTx, suggesting that the influx of Ca2+ was essentially required for cell proliferation. Our data suggest a role for GM1 in the regulation of transmembrane signaling events and cell growth.
authors.affiliation: Department of Biophysics, National Institute of Mental Health and Neurosciences, Bangalore, India.
authors.forename: B
authors.initials: B
authors.lastname: Ravichandra
authors.forename: P G
authors.initials: PG
authors.lastname: Joshi
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000906:Antibodies / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D002455:Cell Division / Q000502:physiology; D002614:Chelating Agents / Q000494:pharmacology; D004232:Diuretics / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D005677:G(M1) Ganglioside / Q000276:immunology* / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D007295:Inositol Phosphates / Q000493:pharmacokinetics; D009355:Neomycin / Q000494:pharmacology; D009447:Neuroblastoma; D009474:Neurons / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D037342:Pertussis Toxin; D011188:Potassium / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology*; D012964:Sodium / Q000378:metabolism; D014316:Tritium; D014407:Tumor Cells, Cultured; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D000906:Antibodies; D015220:Calcium Channels; D002614:Chelating Agents; D004232:Diuretics; D007295:Inositol Phosphates; D011500:Protein Synthesis Inhibitors; D010566:Virulence Factors, Bordetella; D014316:Tritium; D005677:G(M1) Ganglioside; D004533:Egtazic Acid; D000584:Amiloride; D012964:Sodium; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D009355:Neomycin; D011188:Potassium; D002118:Calcium