PDGF and IL-1 induce and activate specific protein kinase C isoforms in mesangial cells

In vitro and in vivo data suggest a remarkable plasticity in the differentiated phenotype of intrinsic glomerular cells, which after injury express new structures and functions. We have shown that a protein kinase C (PKC) isoform, βn, is expressed in diseased but not normal glomeruli. Since intrarenal cytokine synthesis has been implicated in the pathogenesis of progressive glomerular injury, we have hypothesized that these mediators induce a change in isoform profile. To test this hypothesis in vitro, we have determined whether platelet-derived growth factor (PDGF) and interleukin-1 (IL-1) alter the expression or activation of PKC isoforms in cultured mesangial cells (MCs). By immunoblot and ribonuclease (RNase) protection assays, both PDGF and IL-1 induce as early as 2 h de novo synthesis of PKC-βn. Since MCs constitutively express PKC-a, -βj, and -£, we also determined whether IL-1 or PDGF alter the activity of these isoforms. PDGF maximally induced translocation of PKC-a (10 min), -βi (90 min), -e (120 min), and -£ (120 min) from the cytosolic to the membrane fraction. IL-1, in contrast, did not alter the distribution of a, βi, or e at any time measured but did induce PKC-Ç translocation. These data suggest inflammatory mediators regulate PKC isoform activity in diseased glomeruli both by de novo synthesis of unexpressed isoforms and by activation of constitutively expressed PKC isoforms.