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Phosphatidylinositol 3-Kinase Inhibitors Block Differentiation of Skeletal Muscle Cells
Ist Teil von
The Journal of biological chemistry, 1996-08, Vol.271 (32), p.19146-19151
Ort / Verlag
United States: American Society for Biochemistry and Molecular Biology
Erscheinungsjahr
1996
Quelle
MEDLINE
Beschreibungen/Notizen
Skeletal muscle differentiation involves myoblast alignment, elongation, and fusion into multinucleate myotubes, together
with the induction of regulatory and structural muscle-specific genes. Here we show that two phosphatidylinositol 3-kinase
inhibitors, LY294002 and wortmannin, blocked an essential step in the differentiation of two skeletal muscle cell models.
Both inhibitors abolished the capacity of L6E9 myoblasts to form myotubes, without affecting myoblast proliferation, elongation,
or alignment. Myogenic events like the induction of myogenin and of glucose carrier GLUT4 were also blocked and myoblasts
could not exit the cell cycle, as measured by the lack of mRNA induction of p21 cyclin-dependent kinase inhibitor. Overexpresssion
of MyoD in 10T1/2 cells was not sufficient to bypass the myogenic differentiation blockade by LY294002. Upon serum withdrawal,
10T1/2-MyoD cells formed myotubes and showed increased levels of myogenin and p21. In contrast, LY294002-treated cells exhibited
none of these myogenic characteristics and maintained high levels of Id, a negative regulator of myogenesis. These data indicate
that whereas phosphatidylinositol 3-kinase is not indispensable for cell proliferation or in the initial events of myoblast
differentiation, i.e. elongation and alignment, it appears to be essential for terminal differentiation of muscle cells.