title: Characterization of the carboxyl terminal-truncated endothelin B receptor coexpressed with G protein-coupled receptor kinase 2.
abstract: The role of phosphorylation of the C-terminal tail of endothelin B receptor (ETBR) in agonist-induced desensitization was investigated, using a mutant lacking C-terminal 40 amino acids (delta 40 ETBR). In cells expressing the wild type or delta 40 ETBR, ET-1 caused rapid desensitization of calcium responses. The wild type ETBR was phosphorylated by biotinylated ET-1, and the phosphorylation was markedly enhanced by coexpression with G protein-coupled receptor kinase 2 (GRK2). However, delta 40 ETBR was not phosphorylated regardless of coexpression with GRK2. On the other hand, ET-1-induced IP3 formation in these cells was decreased by coexpression with GRK2 or catalytically inactive Lys220Arg GRK2 to the similar extent. The present study demonstrates the presence of phosphorylation-independent desensitization mechanism in delta 40 ETBR and suggests that GRK2 might play a role other than that as a kinase.
mesh_terms: D000818:Animals; D019556:COS Cells; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism; D010766:Phosphorylation; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin / Q000235:genetics / Q000378:metabolism*; D051552:beta-Adrenergic Receptor Kinases