Functional coupling of GABA(B) receptors with G proteins that are sensitive to N-ethylmaleimide treatment, suramin, and benzalkonium chloride in rat cerebral cortical membranes.
Although it is known that GABA(B) receptors are negatively coupled to adenylyl cyclase, the detailed selectivity of functional interaction between GABA(B) receptors and Gi subfamily members is still ambiguous. (+/-)-Baclofen-stimulated high-affinity GTPase activity, which was competitively antagonized by 2-hydroxy-saclofen, was attenuated by pretreatment of the membranes with N-ethylmaleimide (NEM) in a concentration- and incubation period-dependent manner. The NEM-pretreated (50 microM, 15 min at 4 degrees C) membranes restored the (+/-)-baclofen-sensitive high-affinity GTPase activity when reconstituted with pertussis toxin-sensitive bovine brain G proteins. Among recombinant rat Galpha subunits, G(i alpha(-2)) appeared most effective as compared with other subunits (G(i alpha(-2)) > G(i alpha(-3) > G(i alpha(-1) = G(o alpha). The GABA(B) receptor-mediated high-affinity GTPase activity was also completely eliminated by 100 microM suramin and by 100 microM benzalkonium chloride. These results indicate that GABA(B) receptors in rat cerebral cortex couple to NEM-sensitive G proteins, in particular Gi2, which are sensitive to suramin and benzalkonium chloride.
Odagaki
Y
Y
Department of Psychiatry, Hokkaido University School of Medicine, Sapporo, Japan.
Nishi
N
N
Koyama
T
T
D037361:Adenylate Cyclase Toxin; D000818:Animals; D001418:Baclofen / Q000031:analogs & derivatives* / Q000494:pharmacology; D001548:Benzalkonium Compounds / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D004305:Dose-Response Relationship, Drug; D005033:Ethylmaleimide / Q000494:pharmacology*; D018756:GABA Antagonists / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000187:drug effects / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D037342:Pertussis Toxin; D051381:Rats; D017207:Rats, Sprague-Dawley; D018080:Receptors, GABA-B / Q000187:drug effects* / Q000378:metabolism; D013347:Subcellular Fractions / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D013498:Suramin / Q000494:pharmacology*; D010566:Virulence Factors, Bordetella / Q000378:metabolism
D037361:Adenylate Cyclase Toxin; D001548:Benzalkonium Compounds; D018756:GABA Antagonists; D018080:Receptors, GABA-B; D010566:Virulence Factors, Bordetella; D013498:Suramin; D037342:Pertussis Toxin; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D001418:Baclofen; C080629:saclofen; D005033:Ethylmaleimide