title: Growth factors stimulate kidney proximal tubule cell migration independent of augmented tyrosine phosphorylation of focal adhesion kinase.
abstract: Migration of human proximal tubule cells (HKC-5) was stimulated by epidermal growth factor (EGF), hepatocyte growth factor (HGF), and insulin-like growth factor-1 (IGF-1). Integrin signaling via phosphorylation of focal adhesion kinase (FAK) appears to play a central role in cell migration. Once stimulated, FAK undergoes autophosphorylation at tyrosine (Y) 397, followed by phosphorylation of several sites including Y576/Y577 which increases FAK's kinase activity, as well as at Y407, Y861, and Y925. EGF, HGF, and IGF-1 stimulate FAK phosphorylation in various cells. We showed that endothelin stimulated phosphorylation of Y397 in fibroblasts but not HKC-5 cells. After EGF stimulation, HKC-5 cells showed no change in tyrosine phosphorylation at FAK Y397, 407, 576, 861, or 925. Similarly, HGF and IGF-1 did not stimulate the phosphorylation of FAK Y397 in HKC-5 cells. Further, after inhibition of FAK expression by siRNA, cell migration was similar to cells treated with non-target siRNA and responded to EGF with increased migration. Thus, in proximal tubule cells, stimulation of cell migration by growth factors was independent of augmented FAK tyrosine phosphorylation.
authors.affiliation: Section of Nephrology, Tulane University School of Medicine, Veterans Administration Hospital, New Orleans, LA, USA.
authors.forename: Yangming
authors.initials: Y
authors.lastname: Cao
authors.forename: Masood R
authors.initials: MR
authors.lastname: Baig
authors.forename: L Lee
authors.initials: LL
authors.lastname: Hamm
authors.forename: Kuoting
authors.initials: K
authors.lastname: Wu
authors.forename: Eric E
authors.initials: EE
authors.lastname: Simon
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology*; D004815:Epidermal Growth Factor / Q000494:pharmacology; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006133:Growth Substances / Q000494:pharmacology*; D017228:Hepatocyte Growth Factor / Q000494:pharmacology; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D010766:Phosphorylation / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D006133:Growth Substances; D014443:Tyrosine; D004815:Epidermal Growth Factor; D017228:Hepatocyte Growth Factor; D007334:Insulin-Like Growth Factor I; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; C496051:Ptk2 protein, mouse