The Differentiation of Skeletal Muscle Cells Involves a Protein-tyrosine Phosphatase-α-mediated C-Src Signaling Pathway

• Published in: The Journal of biological chemistry 2002-11, Vol.277 (48), p.46687
• Main Authors: Huogen Lu, Poonam Shah, David Ennis, Gail Shinder, Jan Sap, Hoang Le-Tien, I. George Fantus
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M209643200

Protein-tyrosine phosphatase-α (PTPα) plays an important role in various cellular signaling events, including proliferation and differentiation. In this study, we established L6 cell lines either underexpressing or overexpressing PTPα by stable transfection of cells with antisense PTPα or with full-length wild-type human or mouse or double catalytic site Cys → Ala mutant (DM8) PTPα cDNA. Expression of PTPα in these cell lines was determined by immunoblotting and immunofluorescence. Cells harboring antisense PTPα exhibited a significantly reduced growth rate and thymidine incorporation when compared with the wild-type L6 cells. In contrast, cells overexpressing PTPα showed more rapid (2-fold) proliferation. Myoblasts with diminished PTPα failed to undergo fusion and did not form myotubes in reduced serum whereas overexpression of PTPα promoted myogenesis 2 days earlier than wild-type L6 cells. Overexpression of phosphatase-inactive mutant PTPα recapitulated the phenotype of the antisense cells. The different myogenic activities of these cell lines were correlated with the expression of myogenin and creatine kinase activity. Consistent with previous reports, PTPα positively regulated the activity of the protein-tyrosine kinase Src. Treatment of L6 cells with PP2 or SU6656, specific inhibitors of Src family kinases, and transient transfection of dominant-inhibitory Src inhibited the formation of myotubes and expression of myogenin. Moreover, enhanced expression of PTPα and activation of Src was detected during myogenesis. Together, these data indicate that PTPα is involved in the regulation of L6 myoblast growth and skeletal muscle cell differentiation via an Src-mediated signaling pathway.