Enhanced GRK5 expression in the hearts of cardiomyopathic hamsters, J2N-k

GTP binding protein-coupled receptor kinase 5 (CRK5) cDNA was cloned from t he hearts of Syrian hamsters. The hamster GRK5 cDNA contained 1770 nucleoti des encoding 590 amino acids, and the nucleotide sequence had 89.6% homolog y to the human homologue. An inbred cardiomyopathic hamster strain, J2N-k, was used to investigate the alteration of GRK5 mRNA expression in the setti ng of congestive heart failure. M-mode echocardiography revealed significan t dilatation of the left ventricle and a decrease of left ventricular contr actility in 20-week-old J2N-k hamsters compared with age-matched control ha msters, J2N-n. Semi-quantitative RT-PCR showed that GRK5 mRNA expression in the hearts of J2N-k was significantly higher than in those of J2N-n (J2N-k . 60.3 +/- 13.3, J2N-n 25.8 +/- 17.2 arbitrary units, p < 0,005, n = 6 in e ach group). These results suggest that an enhanced GRR5 expression might pl ay a role in the reduced responsiveness to catecholamines in failing hearts via beta-adrenergic receptor phosphorylation. (C) 1999 Academic Press.