Endothelin-induced cardiac myocyte hypertrophy: role for focal adhesion kinase

sEndothelin-1 (ET) produces neonatal rat ventricular myocyte (NRVM) hypertr ophy and activates focal adhesion kinase (FAK) in other cell types. In the present study, we examined whether ET activated FAK in NRVM and whether FAK was necessary and/or sufficient for ET-induced NRVM hypertrophy. Chronic E T-1 stimulation (100 nhl, 48 h) increased protein-to-DNA and myosin heavy c hain (MHC)-to-DNA ratios and stimulated the assembly of newly synthesized M HC into sarcomeres. ET-1 also induced the assembly of focal adhesions and c ostameres, as evidenced by increased phosphotyrosine, FAK, and paxillin imm unostaining. Acutely, ET treatment rapidly increased tyrosine phosphorylati on of FAK and paxillin. FAK was also activated by phorbol 12-myristate 13-a cetate (2 mu M, 5 min). Pretreatment with chelerythrine (5 mu M) Or rottler in (10 mu M) completely blocked ET-induced FAK phosphorylation, indicating that protein kinase C activation was upstream of ET-induced FAK activation. In contrast, ET-induced FAK activation was not affected by blocking calciu m influx via L-type voltage-gated calcium channels. Adenoviruses (Adv) cont aining FAK and FAK-related nonkinase (FRNK) were used to specifically defin e the role of FAK in ET-induced hypertrophy. ET stimulation failed to incre ase total protein-to-DNA or MHC-to-DNA ratios or to stimulate sarcomeric as sembly in myocytes infected with AdV-FRNK. However, AdV-FAK alone did not i ncrease total protein-to-DNA or MHC-to-DNA ratios and failed to increase th e number or size of myofibrils as evidenced by double immunofluorescence la beling for MHC and FAK. Thus, although FAK is necessary for ET-induced NRVM hypertrophy, other ET-generated signals are also required to elicit the hy pertrophic phenotype.