Altered PKC expression and phosphorylation in response to the nature, direction, and magnitude of mechanical stretch
Protein kinase C (PKC) isozymes have been shown to play a role in mechanotransduction in a variety of cell types. We sought to identify the PKC isozymes involved in transducing mechanical (cyclic vs. static), direction and intensity of stretch by examining changes in protein expression and phosphorylation. We used a 3-dimensional culture system with aligned neonatal rat cardiac myocytes on silastic membranes. Myocytes were subjected to either cyclic stretch at 5 cycles/min or static stretch for a period of 24 h at intensities of 0%, 2.5%, 5%, or 10% of full membrane length. Stretch was applied in perpendicular or parallel directions to myocyte alignment. PKC δ was most sensitive to stretch applied perpendicular to myocyte alignment regardless of the nature of stretch, while phospho PKC δ T505 increased in response to static-perpendicular stretch. PKC ε expression was altered by cyclic stretch but not static stretch, while phospho PKC ε S719 remained unchanged. PKC α expression was not altered by stretch; however, phospho PKC α S657 increased in a dose-dependent manner following cyclic-perpendicular stretch. Our results indicate that changes in PKC expression and phosphorylation state may be a mechanism for cardiac myocytes to discriminate between the nature, direction, and intensity of mechanical stretch.