Mechanisms of protease-activated receptor-4 actions in cardiomyocytes. Role of Src tyrosine kinase.
Protease-activated receptor (PAR)-4 is a low affinity thrombin receptor with slow activation and desensitization kinetics relative to PAR-1. This study provides novel evidence that cardiomyocytes express functional PAR-4 whose signaling phenotype is distinct from PAR-1 in cardiomyocytes. AYPGKF, a modified PAR-4 agonist with increased potency at PAR-4, activates p38-mitogen-activated protein kinase but is a weak activator of phospholipase C, extracellular signal-regulated kinase, and cardiomyocyte hypertrophy; AYPGKF and thrombin, but not the PAR-1 agonist SFLLRN, activate Src. The observation that AYPGKF and thrombin activate Src in cardiomyocytes cultured from PAR-1(-/-) mice establishes that Src activation is via PAR-4 (and not PAR-1) in cardiomyocytes. Further studies implicate Src and epidermal growth factor receptor (EGFR) kinase activity in the PAR-4-dependent p38-mitogen-activated protein kinase signaling pathway. Thrombin phosphorylates EGFRs and ErbB2 via a PP1-sensitive pathway in PAR-1(-/-) cells that stably overexpress PAR-4; the Src-mediated pathway for EGFR/ErbB2 transactivation underlies the protracted phases of thrombin-dependent extracellular signal-regulated kinase activation in PAR-1(-/-) cells that overexpress PAR-4 and in cardiomyocytes. These studies identify a unique signaling phenotype for PAR-4 (relative to other cardiomyocyte G protein-coupled receptors) that is predicted to contribute to cardiac remodeling and influence the functional outcome at sites of cardiac inflammation.
Sabri
Abdelkarim
A
Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.
Guo
Jianfen
J
Elouardighi
Hasnae
H
Darrow
Andrew L
AL
Andrade-Gordon
Patricia
P
Steinberg
Susan F
SF
D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D017931:DNA Primers; D051379:Mice; D008810:Mice, Inbred C57BL; D009206:Myocardium / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D018179:Receptors, Thrombin / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D019061:src-Family Kinases / Q000378:metabolism*
D017931:DNA Primers; D018179:Receptors, Thrombin; D019061:src-Family Kinases; C112908:protease-activated receptor 4