Involvement of mu- and m-calpains and protein kinase C isoforms in L8 myoblast differentiation.
The objectives were to investigate the roles of different calpains and protein kinase C (PKC) isoforms in muscle differentiation. Concentrations of mu- and m-calpain increased significantly whereas PKCalpha and delta declined significantly during L8 myoblast differentiation. Both mu-calpain and m-calpain antisense oligonucleotides inhibited myotube formation and creatine kinase activity during L8 myoblast differentiation. These results implied that both mu- and m-calpain were involved in L8 myoblast differentiation. To investigate the involvement of calpain in regulation of PKC concentrations, mu-calpain antisense oligonucleotides were added to L8 myoblasts. PKCalpha remained unchanged and PKCdelta declined. By adding m-calpain antisense oligonucleotides instead, PKCalpha level remained unchanged and PKCdelta concentrations increased significantly during differentiation. These results suggest that PKCalpha, but not PKCdelta, is the substrate for mu-calpain and PKCalpha and delta are the substrates for the m-calpain. In addition, more phosphorylated myogenin was found in day 2 antisense oligonucleotides treated L8 cells. It is concluded that the decline of PKCalpha mediated by m- and mu-calpain is essential for L8 myoblast differentiation. The decline of PKC during myoblast differentiation may cause hypo-phosphorylation of myogenin, which in turn activates muscle-specific genes during myogenesis.
Liang
Yu-Chuan
YC
Department of Animal Science and Biotechnology, Tunghai University, Taichung, 407, Taiwan, ROC.
Yeh
Jan-Ying
JY
Forsberg
Neil E
NE
Ou
Bor-Rung
BR
D000818:Animals; D002154:Calpain / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology; D032446:Myoblasts / Q000378:metabolism*; D020319:Oligodeoxyribonucleotides, Antisense / Q000235:genetics / Q000494:pharmacology; D051571:Protein Kinase C-alpha / Q000235:genetics / Q000378:metabolism*; D051745:Protein Kinase C-delta / Q000235:genetics / Q000378:metabolism*; D051381:Rats
D020319:Oligodeoxyribonucleotides, Antisense; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta; D002154:Calpain; C449000:m-calpain; C449002:mu-calpain