Role of protein kinase C-ε in hypertrophy of cultured neonatal rat ventricular myocytes

Using adenovirus (Adv)-mediated overexpression of constitutively active (ca) and dominant-negative (dn) mutants, we examined whether protein kinase C (PKC)-epsilon, the major novel PKC isoenzyme expressed in the adult heart, was necessary and/or sufficient to induce specific aspects of the hypertrophic phenotype in low-density, neonatal rat ventricular myocytes (NRVM) in serum-free culture. Adv-caPKC-epsilon did not increase cell surface area or the total protein-to-DNA ratio. However, cell shape was markedly affected, as evidenced by a 67% increase in the cell length-to-width ratio and a 17% increase in the perimeter-to-area ratio. Adv-caPKC-epsilon also increased atrial natriuretic factor (ANF) and beta-myosin heavy chain (MHC) mRNA levels 2.5 +/- 0.3- and 2.1 +/- 0.2-fold, respectively, compared with NRVM infected with an empty, parent vector (P < 0.05 for both). Conversely, Adv-dnPKC-epsilon did not block endothelin-induced increases in cell surface area, the total protein-to-DNA ratio, or upregulation of beta-MHC and ANF gene expression. However, the dominant-negative inhibitor markedly suppressed endothelin-induced extracellular signal-regulated kinase (ERK) 1/2 activation. Taken together, these results indicate that caPKC-epsilon overexpression alters cell geometry, producing cellular elongation and remodeling without a significant, overall increase in cell surface area or total protein accumulation. Furthermore, PKC-epsilon activation and downstream signaling via the ERK cascade may not be necessary for cell growth, protein accumulation, and gene expression changes induced by endothelin.