Evidence on the participation of protein kinase C ? in the proliferation of cultured myoblasts

Abstract

There is evidence involving protein kinase C (PKC) in the signal transduction pathways that regulate the differentiation of myoblasts into mature multinucleated muscle cells (myotubes). In order to obtain information on the possible role of individual PKC isozymes in myogenesis, in the present work we investigated the differential expression of PKC isoforms alpha, beta, delta, epsilon, and zeta during muscle cell development in vitro. Chick embryo myoblasts cultured from 1 to 6 days were used as experimental model. Morphological characterization and measurement of specific biochemical parameters in cultures, e.g., DNA synthesis, creatine kinase activity, and myosin levels, revealed a typical muscle cell developmental pattern consisting of an initial proliferation of myoblasts followed by their differentiation into myotubes. PKC activity was high at the proliferation stage, decreased as myoblasts elongated and fused, and increased again in differentiated myotubes. In proliferating myoblasts, the PKC inhibitors calphostin C and bisindolylmaleimide I decreased DNA synthesis whereas in myoblasts undergoing differentiation they exerted the opposite effect, suggesting that PKC plays a role at both stages of myogenesis. Western blot analysis of changes in the expression of PKC isoforms during muscle cell development showed high levels of PKC alpha in the proliferating phase which markedly decreased as myoblasts differentiated. Treatment with TPA of proliferative myoblasts inhibited DNA synthesis and selectively down-regulated PKC alpha, suggesting that this isozyme may have an important role in maintaining myoblast proliferation. On the other hand, an increase in the expression of PKC beta, delta, and epsilon was detected during myogenesis, suggesting that one or more of these isoforms may participate in the differentiation process of myoblasts.

5-Azacytidine Induces Cardiac Differentiation of Human Umbilical Cord-Derived Mesenchymal Stem Cells by Activating Extracellular Regulated Kinase

“…These differences in results might be because of the cell types, induction time, drug doses, or means of administration. Although the activation of the PKC signaling pathway is reported to be involved in myogenesis [26], we found no significant change in total PKC or phosphorylated PKC in 5-Aza-treated hucMSCs. This indicated that PKC activation was not the major mechanism responsible for 5-Aza-induced hucMSC differentiation into cardiomyocytes.…”

Inositol 1,4,5-trisphosphate (IP3)-dependent Ca2+ signaling mediates delayed myogenesis in Duchenne muscular dystrophy fetal muscle

“…PKCα is involved in signal transduction cascades regulating the proliferation of myoblasts (Goel and Dey, 2002). Furthermore, PKCα is engaged in repressing myogenic factors, in particular MyoD (Vaidya et al, 1991), suggesting its role as a negative modulator of myogenesis (Capiati et al, 1999). Interestingly, Ryr1 activity had been related to both PKCα activation and MyHC-slow gene suppression.…”

Activation of Src kinase in skeletal muscle cells by 1,25-(OH)2-vitamin D3 correlates with tyrosine phosphorylation of the vitamin D receptor (VDR) and VDR-Src interaction

“…By this time, myoblasts become differentiated into myotubes with both biochemical and morphological characteristics of adult skeletal muscle fibers [Capiati et al, 1999].…”