OVER-EXPRESSION OF PROTEIN-KINASE-C-ALPHA AND BETA-1 HAS DISTINCT EFFECTS ON BOVINE AORTIC ENDOTHELIAL-CELL GROWTH

Protein kinase C (PKC) plays an important role in the mitogenic respon se of endothelial cells to growth factors. PKC alpha and beta 1 are th e predominant classical isoforms expressed by bovine aortic endothelia l cells (BAECs). The present studies were undertaken to elucidate the effect of PKC alpha and beta 1 overexpression in BAEC growth. A series of BAEC lines that stably overexpress the full-length PKC alpha and b eta 1 cDNA were generated by using a replication-defective recombinant retrovirus. The level of PKC alpha and beta 1 cDNA expression was det ermined by assaying for PKC alpha and beta 1 mRNA transcripts. PKC alp ha and beta 1 protein levels were analysed by Western blotting. Functi onal analysis of these overexpressing lines was performed by measuring PKC activity and phorbol ester-binding assays. PKC alpha and beta 1 o verexpression had distinctive effects on BAEC growth and cell-cycle pr ogression. Relative to untransfected BAECs and BAECs transfected with the viral vector alone, BAECs that overproduced PKC alpha exhibited re duced proliferation in vitro and increased accumulation of cells in th e G(2)/M phase of die cell cycle. Growth inhibition was greater in cel l lines overexpressing higher levels of PKC alpha. Conversely, a 5-fol d greater increase in PKC beta 1 activity promoted BAEC growth and sho rtened BAEC doubling time, whereas cells with a 2- to 4-fold increase in enzyme activity had growth profiles similar to those of both contro l groups. These results suggest that PKC alpha and beta 1 overexpressi on has reciprocal effects on BAEC growth. CELL SIGNAL 10;8:589-597, 19 98. Published by Elsevier Science Inc.