title: Phosphatidylinositol 3-kinase inhibitors block differentiation of skeletal muscle cells.
abstract: 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.
authors.affiliation: Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Avda. Diagonal 645, 08028 Barcelona, Spain.
authors.forename: P
authors.initials: P
authors.lastname: Kaliman
authors.forename: F
authors.initials: F
authors.lastname: Viñals
authors.forename: X
authors.initials: X
authors.lastname: Testar
authors.forename: M
authors.initials: M
authors.lastname: Palacín
authors.forename: A
authors.initials: A
authors.lastname: Zorzano
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects* / Q000235:genetics; D002460:Cell Line; D002867:Chromones / Q000494:pharmacology; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins / Q000235:genetics; D009025:Morpholines / Q000494:pharmacology; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D017570:MyoD Protein / Q000378:metabolism; D018008:Myogenin / Q000235:genetics; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; C493958:Cdkn1a protein, rat; D002867:Chromones; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009025:Morpholines; D009124:Muscle Proteins; D017570:MyoD Protein; C503803:Myog protein, rat; D018008:Myogenin; D012333:RNA, Messenger; C495694:Slc2a4 protein, rat; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D000077191:Wortmannin