PKC-regulated myogenesis is associated with increased tyrosine phosphorylation of FAK, Cas, and paxillin, formation of Cas-CRK complex, and JNK activation.
Previous reports suggest that PKC plays an important role in regulating myogenesis. However, the regulatory signaling pathways are not fully understood. We examined the effects of PKC downregulation on signaling events during skeletal muscle differentiation. We found that downregulation of PKC results in increased myogenesis in C2C12 cells as measured by creatine kinase activity and myogenin expression. We showed that, during differentiation, downregulation of PKC expression results in increased tyrosine phosphorylation of FAK, Cas, and paxillin, concomitant with enhanced Cas-CrkII complex formation, which leads to activation of JNK2. But in proliferated muscle cells, PKC inhibition results in FAK and Cas tyrosine dephosphorylation. Further, disruption of actin cytoskeleton by cytochalasin D prevents the activation of FAK and Cas as well as the formation of Cas-CrkII complex stimulated by PKC downregulation during muscle cell differentiation. Finally, we observed that PKC downregulation increases the tyrosine phosphorylation of focal adhesion associated proteins. Based on the above data, we propose that PKC downregulation results in enhanced tyrosine phosphorylation of FAK, Cas, and paxillin, thus promoting the establishment of Cas-CrkII complex, leading to activation of JNK and that these interactions are dependent upon the integrity of actin cytoskeleton during muscle cell differentiation. Data presented here significantly contribute to elucidating the regulatory role of PKC in myogenesis possibly through integrin signaling pathway.
Signal Transduction Research Laboratory, Department of Biotechnology, National Institute of Pharmaceutical Education and Research, India.
Hira Lal
HL
Goel
Chinmoy Sankar
CS
Dey
D008841:Actin Cytoskeleton / Q000502:physiology / Q000648:ultrastructure; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division; D002478:Cells, Cultured / Q000187:drug effects; D003402:Creatine Kinase / Q000096:biosynthesis; D052283:Creatine Kinase, MM Form; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D003599:Cytoskeleton / Q000502:physiology; D004789:Enzyme Activation; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D022001:Focal Adhesions / Q000378:metabolism; D007527:Isoenzymes / Q000096:biosynthesis; D048031:JNK Mitogen-Activated Protein Kinases; D020935:MAP Kinase Signaling System; D046911:Macromolecular Substances; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000166:cytology*; D051419:Paxillin; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology*; D011499:Protein Processing, Post-Translational; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D050737:Proto-Oncogene Proteins c-crk; D015398:Signal Transduction / Q000502:physiology*
D048868:Adaptor Proteins, Signal Transducing; D003598:Cytoskeletal Proteins; D007527:Isoenzymes; D046911:Macromolecular Substances; C099942:NEDD9 protein, human; D051419:Paxillin; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D050737:Proto-Oncogene Proteins c-crk; C496062:Pxn protein, mouse; D015240:Phorbol 12,13-Dibutyrate; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496051:Ptk2 protein, mouse; D011493:Protein Kinase C; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D003402:Creatine Kinase; D052283:Creatine Kinase, MM Form