RESUMEN
60-75% of PKC alpha and 30-40% of PKC beta I++ protein was located to the membranes and nuclear/nuclear associated endoplasmatic reticulum fractions of resting 10T1/2CI 8 mouse embryo fibroblasts. On average, 35% of the PKC alpha and 65% of the PKC beta I++ isoforms existed in a soluble state. Maximum PDGF-BB-mediated Erk1 activation was obtained without significant changes in soluble PKC alpha- or PKC beta I++- levels. The subcellular localisation of PKC alpha and PKC beta I was not affected by PDGF-BB treatment. 12-O-tetradecanoyl phorbol-13-acetate (TPA) caused translocation of cytoplasmic PKC alpha and beta I to the nucleus/nuclear associated endoplasmatic reticulum fraction. Down-regulation of PKC and bisindolylmaleimide I inhibited both TPA and PDGF-BB stimulated Erk1 activity. We are the first to show that PDGF-mediated activation of Erk1 involves a PKC-dependent step in 10T1/2CI 8 cells. We also provide novel evidence that PDGF-BB mediated Erk1 activation can take place in these cells without apparent recruitment of soluble PKC alpha/beta I to the particulate cell fractions.