title: Pyk2 expression and phosphorylation in neonatal and adult cardiomyocytes.
abstract: A. L. Bayer, A. G. Ferguson, P. A. Lucchesi and A. M. Samarel. PYK2 Expression and Phosphorylation in Neonatal and Adult Cardiomyocytes. Journal of Molecular and Cellular Cardiology (2001) 33, 1017-1030. Proline-rich tyrosine kinase (PYK2) is a Ca(2+)-dependent, non-receptor protein tyrosine kinase involved in growth factor signaling. Although PYK2 is expressed in a variety of tissues, it has not yet been identified in cardiac muscle. Therefore, immunocytochemical and Western blotting techniques were used to examine PYK2 expression and phosphorylation in neonatal and adult rat ventricular cardiomyocytes (NRVM and ARVM, respectively). PYK2 concentration was much greater in neonatal, than in adult ventricular tissue and cardiomyocytes. In cultured cells, PYK2 expression was highly dependent on [Ca(2+)](i)transients and contractile activity. Non-contracting, low-density NRVM in serum-free culture expressed very low levels of PYK2, while high-density, spontaneously contracting NRVM showed a approximately 12-fold increase in PYK2 expression. Conversely, high-density NRVM treated with nifedipine (10 microM, 48 h) to block spontaneous [Ca(2+)](i)transients and contractile activity resulted in a 2.6-fold decrease in PYK2 levels. Similarly, overnight culture of quiescent ARVM markedly reduced PYK2 levels. Chronic treatment (48 h) of cultured NRVM with the hypertrophic agonist endothelin-1 (ET) (10-300 n M) did not significantly increase PYK2 levels, but strongly shifted the ratio of phosphorylated to total PYK2, indicating that PYK2 phosphorylation accompanies cardiomyocyte hypertrophy. Endothelin-1 also acutely activated PYK2 in both cultured NRVM, and in freshly isolated ARVM. These results suggest that PYK2 is involved in the generation of certain aspects of cardiomyocyte hypertrophy.
authors.affiliation: The Cardiovascular Institute, Loyola University Chicago Stritch School of Medicine, 2160 South First Avenue, Maywood, IL 60153, USA. abayer@lumc.edu
authors.forename: A L
authors.initials: AL
authors.lastname: Bayer
authors.forename: A G
authors.initials: AG
authors.lastname: Ferguson
authors.forename: P A
authors.initials: PA
authors.lastname: Lucchesi
authors.forename: A M
authors.initials: AM
authors.lastname: Samarel
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D002118:Calcium / Q000494:pharmacology; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000494:pharmacology; D005260:Female; D051418:Focal Adhesion Kinase 2; D007150:Immunohistochemistry; D008297:Male; D008856:Microscopy, Fluorescence; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology; D010766:Phosphorylation; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000096:biosynthesis* / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D013997:Time Factors
chemical_list: D016895:Culture Media, Serum-Free; D019332:Endothelin-1; D011505:Protein-Tyrosine Kinases; D051418:Focal Adhesion Kinase 2; C496054:Ptk2b protein, rat; D009543:Nifedipine; D002118:Calcium