title: The CB(1) cannabinoid receptor juxtamembrane C-terminal peptide confers activation to specific G proteins in brain.
abstract: Under reducing conditions of SDS-polyacrylamide gel electrophoresis, the CB(1) receptor exists in its monomeric form as well as in an SDS-resistant high molecular weight form that appears to be devoid of G proteins. The CB(1) cannabinoid receptor was immunoprecipitated from 3-[(3-cholamidopropyl)dimethylammonio]propanesulfonate-solubilized rat brain membranes using an antibody against the CB(1) receptor N terminus. The CB(1) receptor was coimmunoprecipitated with its associated G proteins, specifically those of the Galpha(i/o) family, but not Galpha(s), Galpha(q), or Galpha(z). The CB(1) receptor-Galpha(i/o) complex existed in the absence of exogenous agonists, and the cannabinoid receptor agonist desacetyllevonantradol failed to alter the stoichiometry of the receptor-Galpha(i/o) interaction. Guanosine-5'-O-(3-thio)triphosphate could disrupt the interaction. A peptide derived from the CB(1) receptor juxtamembrane C-terminal domain, peptide CB(1)401-417, autonomously activates G(i/o) proteins. Peptide CB(1)401-417 competitively disrupted the CB(1) receptor association with Galpha(o) and Galpha(i3) but not Galpha(i1) or Galpha(i2). This G protein specificity was also observed in detergent extracts from membranes of the frontal cortex, striatum, and cerebellum. Alternative peptides, including peptides from the CB(1) receptor third intracellular loop and the G protein activating peptide mastoparan-7, failed to promote uncoupling from Galpha(o). A CB(2) receptor juxtamembrane C-terminal peptide failed to disrupt the CB(1) receptor-Galpha(o) complex. These studies illustrate that the CB(1) receptor can exist as an SDS-resistant multimer. In 3-[(3-cholamidopropyl)dimethylammonio]propanesulfonate detergent, the CB(1) receptor exists in a complex with G proteins of the G(i/o) family in the absence of exogenous agonists. Furthermore, this study provides the first description of domain specificity for interaction with a selective set of G proteins.
authors.affiliation: Department of Pharmacological Science, Saint Louis University School of Medicine, St. Louis, Missouri, USA.
authors.forename: S
authors.initials: S
authors.lastname: Mukhopadhyay
authors.forename: H H
authors.initials: HH
authors.lastname: McIntosh
authors.forename: D B
authors.initials: DB
authors.lastname: Houston
authors.forename: A C
authors.initials: AC
authors.lastname: Howlett
mesh_terms: D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D002186:Cannabinoids; D002793:Cholic Acids / Q000737:chemistry; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000819:agonists / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000032:analysis / Q000378:metabolism; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D011108:Polymers / Q000378:metabolism; D011233:Precipitin Tests; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D043885:Receptor, Cannabinoid, CB2; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D002186:Cannabinoids; D002793:Cholic Acids; C469526:Cnr2 protein, rat; D008565:Membrane Proteins; D010446:Peptide Fragments; D011108:Polymers; D011518:Proto-Oncogene Proteins; D043885:Receptor, Cannabinoid, CB2; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D020962:Heterotrimeric GTP-Binding Proteins; C028213:3-((3-cholamidopropyl)dimethylammonium)-1-propanesulfonate