Metabotropic glutamate receptor analogues inhibit p[NH]ppG-stimulated phospholipase C activity in bovine brain coated vesicles: involvement of a pertussis toxin-sensitive G-protein.
Guanosine 5'-[beta gamma-imido]triphosphate (p[NH]ppG)-stimulated phospholipase C (PLC) activity in bovine brain coated vesicles is inhibited by glutamate agonists. In the present study we show that quisqualic acid (QA), (+/-)-trans-1-aminocyclopentane-1,3-dicarboxylate (trans-ACPD), glutamic acid and ibotenic acid inhibited p[NH]ppG-stimulated PLC by 44, 41, 36 and 25% respectively. Carbachol also produced an inhibition of p[NH]ppG-stimulated PLC by 45%. The inhibition caused by trans-ACPD and QA was dose-dependent. DL-2-Amino-3-phosphonopropionic acid and (RS)-alpha-methyl-4-carboxyphenylglycine, specific antagonists of metabotropic glutamate receptors (mGluRs), abolished these inhibitory effects. trans-ACPD inhibition of p[NH]ppG-stimulated PLC was also observed in the presence of ionotropic glutamate receptor antagonists. When carbachol and QA or trans-ACPD were combined, additive inhibitory effects were observed. Preincubation of bovine brain coated vesicles with pertussis toxin abolished the inhibitory effects of mGluR analogues and carbachol on p[NH]ppG-stimulated PLC activity. The presence of Gs alpha and pertussis toxin substrates, Gi alpha and Go alpha subunits as well as PLC beta 1 in bovine brain coated vesicles has been confirmed by immunoblot. These results support the coupling of mGluRs to a PLC in an inhibitory manner through a pertussis toxin-sensitive G-protein in bovine brain coated vesicles.
Martín
M
M
Departamento de Inorgánica Orgánica y Bioquímica, Facultad de Químicas, Universidad de Castilla-La Mancha, Ciudad Real, Spain.
Sanz
J M
JM
Ros
M
M
Cubero
A
A
D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000201:enzymology*; D002417:Cattle; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology*; D007527:Isoenzymes / Q000037:antagonists & inhibitors* / Q000378:metabolism; D008081:Liposomes; D008566:Membranes / Q000201:enzymology; D037342:Pertussis Toxin; D017470:Receptors, Glutamate / Q000378:metabolism*; D013268:Stimulation, Chemical; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D007527:Isoenzymes; D008081:Liposomes; D017470:Receptors, Glutamate; D010566:Virulence Factors, Bordetella; D006165:Guanylyl Imidodiphosphate; D037342:Pertussis Toxin; D010738:Type C Phospholipases