CB1 receptor-G protein association. Subtype selectivity is determined by distinct intracellular domains.
The CB1 cannabinoid receptor in N18TG2 neuroblastoma cells inhibits adenylate cyclase, and this response can be mimicked by a peptide corresponding to the juxtamembrane C-terminal domain (CB(1)401-417). Guanosine 5'-O-(3-thio)triphosphate binding to G proteins can be stimulated by both peptide CB(1)401-417 and peptides corresponding to the third intracellular loop [Howlett, A.C., Song, C., Berglund, B.A., Wilken, G.H. & Pigg, J.J. (1998) Mol. Pharmacol. 53, 504-510; Mukhopadhyay, S., Cowsik, S.M., Welsh, W.J. & Howlett, A.C. (1999) Biochemistry 38, 3447-3455]. In Chaps-solubilized N18TG2 membranes, the CB1 receptor coimmunoprecipitated with all three Gi subtypes. Pertussis toxin significantly reduced the CB(1) receptor-G alpha(i) association and attenuated the CB(1)401-417-induced inhibition of adenylate cyclase. CB(1)401-417 significantly reduced the CB(1) receptor association with G alpha(i3), but not with G alpha(i1) or G alpha(i2). In contrast, third intracellular loop peptides significantly reduced the CB(1) receptor association with G alpha(i1) and G alpha(i2), but not G alpha(i3). These interactions are specific for the CB(1) receptor because a peptide corresponding to the juxtamembrane C-terminal domain of the CB(2) receptor failed to compete for the association of the CB1 receptor with any of the Gi alpha subtypes, and was not able to activate Gi proteins to inhibit adenylate cyclase. These studies indicate that different domains of the CB(1) receptor direct the interaction with specific G protein subtypes.
Mukhopadhyay
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Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, St Louis, MO, USA.
Howlett
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AC
D037361:Adenylate Cyclase Toxin; D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D016466:CHO Cells; D002462:Cell Membrane / Q000737:chemistry; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D019204:GTP-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D037342:Pertussis Toxin; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000737:chemistry* / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D000067956:Adenylyl Cyclase Inhibitors; D010455:Peptides; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug; D010566:Virulence Factors, Bordetella; D006160:Guanosine Triphosphate; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases