Insulin stimulates spreading of skeletal muscle cells involving the activation of focal adhesion kinase, phosphatidylinositol 3-kinase and extracellular signal regulated kinases.
Insulin plays an important role in muscle cell survival and proliferation. However, there is no report showing the role of insulin in spreading of muscle cells. In the present report, we showed that insulin enhances muscle cell spreading concomitant with enhanced tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin. Moreover, insulin can stimulate the cell spreading even in presence of integrin alpha5 blockers although to a lesser extent as compared to control. Cell adhesion was not dependent on insulin and serum, and decreased in presence of integrin blockers. We found direct association of FAK with affinity purified insulin receptors using in vitro kinase assay. The increase in FAK tyrosine phosphorylation was associated with increase in its kinase activity and further supported by increased phosphotyrosine accumulation on focal adhesions and increased membrane localization of FAK after stimulation by insulin. Moreover, insulin-mediated muscle cell spreading was dependent upon phosphatidylinositol 3-kinase (PI 3-kinase) activity. PI 3-kinase activity was found to be associated with FAK and the FAK associated PI 3-kinase activity enhanced when cells were plated in presence of insulin. We also observed activation of MAP kinases, i.e., ERK-1/-2 during insulin mediated muscle cell spreading. In conclusion, FAK, PI 3-kinase, and MAP kinase are important components of pathway(s) that regulate insulin stimulated muscle cell spreading.
Goel
Hira Lal
HL
Signal Transduction Research Laboratory, Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Punjab, India.
Dey
Chinmoy Sankar
CS
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D002465:Cell Movement; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005353:Fibronectins / Q000494:pharmacology; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009025:Morpholines / Q000494:pharmacology; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology; D051419:Paxillin; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011972:Receptor, Insulin / Q000378:metabolism; D000077191:Wortmannin
D000730:Androstadienes; D002867:Chromones; D003598:Cytoskeletal Proteins; D004791:Enzyme Inhibitors; D005353:Fibronectins; D007328:Insulin; D009025:Morpholines; D009842:Oligopeptides; D051419:Paxillin; D010750:Phosphoproteins; C496062:Pxn protein, mouse; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C047981:arginyl-glycyl-aspartic acid; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496051:Ptk2 protein, mouse; D020928:Mitogen-Activated Protein Kinases; D000077191:Wortmannin