Osmomechanical stress selectively regulates translocation of protein kinase C isoforms

Osmomechanical stress, resulting in cell swelling and activation/regulation of numerous cellular processes, may play a critical role in cell signaling by selectively regulating translocation of protein kinase C (PKC) isoforms from cytosol to membrane compartments. Western blotting of renal epithelial cell fractions demonstrated the expression of five PKC isoforms. Three of these isoforms (PKCalpha, PKCepsilon, PKCzeta) translocated to the membrane fraction upon exposure of cells to osmomechanical stress (hypotonic medium). Immunohistochemical staining of cells using isoform-specific antibodies further demonstrated translocation of the phorbol ester-sensitive isoforms, PKCalpha and PKCepsilon, to both the plasma membrane and perinuclear sites, reflecting potential initial steps in regulation of specific effector pathways. Indeed, selective inhibition of PKCs indicates a potential role for PKCalpha in modulating a calcium influx channel. It is concluded that osmomechanical stress induces selective translocation of specific PKC isoforms, demonstrating a key role of osmomechanical stress in selectively regulating PKC-dependent signaling pathways.