title: GTPases and phosphatidylinositol 3-kinase are critical for insulin-like growth factor-I-mediated Schwann cell motility.
abstract: Previously, we reported insulin-like growth factor-I (IGF-I) promotes motility and focal adhesion kinase (FAK) activation in neuronal cells. In the current study, we examined the role of IGF-I in Schwann cell (SC) motility. IGF-I increases SC process extension and motility. In parallel, IGF-I activates IGF-I receptor, insulin receptor substrate-1 (IRS-1), phosphatidylinositol 3 (PI-3)-kinase, and FAK. LY294002, a PI-3 kinase inhibitor, blocks IGF-I-induced motility and FAK phosphorylation. The Rho family of GTPases is important in the regulation of the cytoskeleton. Overexpression of constitutively active Leu-61 Cdc42 and Val-12 Rac1 enhances SC motility which is unaffected by LY294002. In parallel, stable transfection of SC with dominant negative Asn-17 Rac1 blocks IGF-I-mediated SC motility and FAK phosphorylation, implying Rac is an upstream regulator of FAK. Collectively our results suggest that IGF-I regulates SC motility by reorganization of the actin cytoskeleton via the downstream activation of a PI-3 kinase, small GTPase, and FAK pathway.
authors.affiliation: Department of Neurology, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: H L
authors.initials: HL
authors.lastname: Cheng
authors.forename: M L
authors.initials: ML
authors.lastname: Steinway
authors.forename: J W
authors.initials: JW
authors.lastname: Russell
authors.forename: E L
authors.initials: EL
authors.lastname: Feldman
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001369:Axons; D018797:Cell Cycle Proteins / Q000378:metabolism; D002867:Chromones / Q000494:pharmacology; D018920:Coculture Techniques; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D005727:Ganglia, Spinal / Q000166:cytology; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D020935:MAP Kinase Signaling System; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000494:pharmacology; D012583:Schwann Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology
chemical_list: D000199:Actins; D018797:Cell Cycle Proteins; D002867:Chromones; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D020558:GTP Phosphohydrolases; D007334:Insulin-Like Growth Factor I; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011505:Protein-Tyrosine Kinases; D011994:Recombinant Proteins; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C496050:PTK2 protein, human; C496052:Ptk2 protein, rat