κ-Opioid Receptor Signals through Src and Focal Adhesion Kinase to Stimulate c-Jun N-Terminal Kinases in Transfected COS-7 Cells and Human Monocytic THP-1 Cells

• Published in: The Journal of pharmacology and experimental therapeutics 2004-07, Vol.310 (1), p.301
• Main Authors: Angel Y. F. Kam, Anthony S. L. Chan, Yung H. Wong
• Format: Article
• Language: English
• ISSN: 0022-3565; 1521-0103
• DOI: 10.1124/jpet.104.065078

Opioid peptides exert diverse physiological functions through their cognate receptors. One subtype of the opioid receptors, κ-opioid receptor, is endogenously expressed in human monocytic THP-1 cells. Stimulation of the THP-1 cells with a κ-opioid receptor-selective agonist exerted a G i -dependent activation of c-Jun N-terminal kinase (JNK). To further investigate the signaling mechanism by which the κ-opioid receptor regulates JNK activity, heterologous expression assays in COS-7 cells were utilized. Overexpression of Gα t in COS-7 cells clearly suppressed κ-opioid receptor-stimulated JNK activity, indicating that the pathway is primarily regulated by Gβγ. In both THP-1 and transfected COS-7 cells, pretreatment of the selective Src family kinase inhibitor pyrazolopyrimidine PP1 abolished the JNK activation, whereas the epidermal growth factor receptor inhibitor AG1478 [ N -(3-chlorophenyl)-6,7-dimethoxy-4-quinazolinanine] failed to do that. Furthermore, the JNK activation in response to κ-opioid receptor was suppressed by an autophosphorylation-resistant mutant of focal adhesion kinase (FAK). Consistently, activated κ-opioid receptor induced Src stimulation and FAK autophosphorylation and promoted the formation of Src-FAK complex. The participation of small GTPases as well as a guanine nucleotide exchange factor was also implicated because dominant-negative mutants of Rac, Cdc42, and Son-of-sevenless (Sos) attenuated the agonist-induced activation of JNK. These studies demonstrate that the activation of JNK by κ-opioid receptors is routed via Gβγ, Src, FAK, Sos, Rac, and Cdc42.