Expression of protein kinase C isoforms in cultured human retinal pigment epithelial cells

Protein kinase C (PKC) is involved in both physiological and pathophysiological processes and plays an important role in signal transduction. The present studies were designed to examine the 12 isoforms (PKCalpha, PKCbetaI, PKCbetaII, PKCgamma, PKCdelta, PKCepsilon, PKCeta, PKCtheta, PKCmu, PKCxi, PKClambda and PKCiota) of PKC expressed in cultured human retinal pigment epithelium (RPE) cells.

Human RPE cells were investigated for 12 PKC isoforms at the mRNA, protein and cellular levels by reverse transcription (RT)-PCR, Western blot analysis and laser scanning confocal microscope (LSCM), respectively.

RT-PCR and Western blot analyses showed similar results for specific PKC isoforms in that both revealed that PKCalpha, PKCbetaI, PKCbetaII, PKCdelta, PKCepsilon, PKCtheta, PKCmu, PKCxi, PKClambda and PKCiota, but not PKCgamma and PKCeta, were constantly expressed in RPE cells, with the exception of PKCbetaI at the protein level. Confocal microscopy showed that ten PKC isoforms - PKCalpha, PKCbetaI, PKCbetaII, PKCdelta, PKCepsilon, PKCtheta, PKCxi, PKCiota, PKClambda and PKCmu - appeared almost exclusively in the cytoplasm of the cells. However, PKCgamma and PKCeta were not detected by staining.

This study characterized the expression pattern of all 12 PKC isoforms and showed that ten of these (PKCalpha, PKCbetaI, PKCbetaII, PKCdelta, PKCepsilon, PKCtheta, PKCmu, PKCxi, PKClambda and PKCiota) are present in cultured human RPE cells. This identification provides the first step towards elucidating their roles in RPE cell proliferation.