Myogenic signaling of phosphatidylinositol 3-kinase requires the serine-threonine kinase Akt/protein kinase B.
The oncogene p3k, coding for a constitutively active form of phosphatidylinositol 3-kinase ( PI 3-kinase), strongly activates myogenic differentiation. Inhibition of endogenous PI 3-kinase activity with the specific inhibitor LY294002, or with dominant-negative mutants of PI 3-kinase, interferes with myotube formation and with the expression of muscle-specific proteins. Here we demonstrate that a downstream target of PI 3-kinase, serine-threonine kinase Akt, plays an important role in myogenic differentiation. Expression of constitutively active forms of Akt dramatically enhances myotube formation and expression of the muscle-specific proteins MyoD, creatine kinase, myosin heavy chain, and desmin. Transdominant negative forms of Akt inhibit myotube formation and the expression of muscle-specific proteins. The inhibition of myotube formation and the reduced expression of muscle-specific proteins caused by the PI 3-kinase inhibitor LY294002 are completely reversed by constitutively active forms of Akt. Wild-type cellular Akt effects a partial reversal of LY294002-induced inhibition of myogenic differentiation. This result suggests that Akt can substitute for PI 3-kinase in the stimulation of myogenesis; Akt may be an essential downstream component of PI 3-kinase-induced muscle differentiation.[1]References
- Myogenic signaling of phosphatidylinositol 3-kinase requires the serine-threonine kinase Akt/protein kinase B. Jiang, B.H., Aoki, M., Zheng, J.Z., Li, J., Vogt, P.K. Proc. Natl. Acad. Sci. U.S.A. (1999) [Pubmed]
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