Functional roles of the tyrosine within the NP(X)nY motif and the cysteines in the C-terminal juxtamembrane region of the CB2 cannabinoid receptor

In G protein-coupled receptors, a NP(X)(n)Y motif in the seventh transmembrane domain and cysteine residues in the C-terminal juxtamembrane region are conserved. In the current study the roles of Y299 within the NPVIY motif and C313 and C320 in the C-terminal juxtamembrane region of the human CB2 cannabinoid receptor were investigated by site-directed mutagenesis. Replacing Y299 with alanine resulted in a complete loss of ligand binding and a severe impairment of cannabinoid-induced inhibition of forskolin-stimulated cAMP accumulation. The C313A and C320A mutations markedly reduced functional coupling to adenylate, cyclase, but had no effect on ligand binding and agonist-induced receptor desensitization. (C) 2001 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.