Involvement of μ- and m-calpains and protein kinase C isoforms in L8 myoblast differentiation

• Published in: The international journal of biochemistry & cell biology 2006, Vol.38 (4), p.662-670
• Main Authors: Liang, Yu-Chuan, Yeh, Jan-Ying, Forsberg, Neil E., Ou, Bor-Rung
• Format: Article
• Language: English
• Subjects: Animals; Antisense oligonucleotide; Calpain - antagonists & inhibitors; Calpain - genetics; Calpain - metabolism; Calpains; Cell Differentiation - drug effects; Cell Differentiation - physiology; Cell Line; Enzyme Activation - drug effects; Enzyme Activation - genetics; Gene Expression Regulation, Enzymologic - drug effects; Gene Expression Regulation, Enzymologic - physiology; L8 myoblast; Myoblasts - metabolism; Oligodeoxyribonucleotides, Antisense - genetics; Oligodeoxyribonucleotides, Antisense - pharmacology; Protein kinase C; Protein Kinase C-alpha - genetics; Protein Kinase C-alpha - metabolism; Protein Kinase C-delta - genetics; Protein Kinase C-delta - metabolism; Rats
• ISSN: 1357-2725; 1878-5875
• DOI: 10.1016/j.biocel.2005.11.009

The objectives were to investigate the roles of different calpains and protein kinase C (PKC) isoforms in muscle differentiation. Concentrations of μ- and m-calpain increased significantly whereas PKCα and δ declined significantly during L8 myoblast differentiation. Both μ-calpain and m-calpain antisense oligonucleotides inhibited myotube formation and creatine kinase activity during L8 myoblast differentiation. These results implied that both μ- and m-calpain were involved in L8 myoblast differentiation. To investigate the involvement of calpain in regulation of PKC concentrations, μ-calpain antisense oligonucleotides were added to L8 myoblasts. PKCα remained unchanged and PKCδ declined. By adding m-calpain antisense oligonucleotides instead, PKCα level remained unchanged and PKCδ concentrations increased significantly during differentiation. These results suggest that PKCα, but not PKCδ, is the substrate for μ-calpain and PKCα and δ 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 PKCα mediated by m- and μ-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.