An N-ethylmaleimide-sensitive G-protein modulates Aplysia Ca2+ channels.
The sulfhydryl alkylating agent N-ethylmaleimide (NEM) was used to probe the possible modulation of calcium current (ICa) by G-proteins in identified neurons of Aplysia californica. ICa recorded with conventional two-electrode voltage clamp was irreversibly suppressed by bath applied NEM in a concentration-dependent manner. This effect was fully blocked by addition of dithiothreitol or intracellular pressure injection of GTP gamma S but was unaffected by pre-treatment with pertussis toxin. These findings suggest that NEM inhibits ICa by causing persistent activation of an inhibitory G-protein in the absence of applied agonist. It appears that alkylation of key cysteine residues involved in G-protein deactivation underlie this effect.
Fryer
M W
MW
Department of Zoology, La Trobe University, Bundoora, Australia.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001048:Aplysia / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects*; D004229:Dithiothreitol / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology*; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D005724:Ganglia / Q000166:cytology / Q000187:drug effects; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D037342:Pertussis Toxin; D013779:Tetrodotoxin / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D015220:Calcium Channels; D010566:Virulence Factors, Bordetella; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D013779:Tetrodotoxin; D037342:Pertussis Toxin; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D005033:Ethylmaleimide; D004229:Dithiothreitol