title: Tyrosine-phosphorylated Hic-5 inhibits epidermal growth factor-induced lamellipodia formation.
abstract: The focal adhesion protein Hic-5, a homologue to paxillin, has been shown to be tyrosine-phosphorylated in fibroblasts in response to stimuli such as osmotic stress, serum, LPA and endothelin. However, the function of this modification to Hic-5 is unclear. Herein, we show that Hic-5 is tyrosine-phosphorylated on residues 38 and 60 following epidermal growth factor (EGF) treatment of COS-7 cells, coincident with an increase in peripheral actin reorganization. To explore the role of Hic-5 phosphorylation in this process, we introduced wild-type (WT) and mutant Hic-5 constructs into COS-7 cells and determined that EGF-induced lamellipodia formation was suppressed by WT Hic-5. This effect required localization to focal adhesions as well as phosphorylation of Hic-5 as overexpression of both a non-targeting and a non-phosphorylatable Hic-5 failed to inhibit peripheral actin reorganization. Interestingly, overexpression of non-phosphorylatable Y31/118F or WT paxillin did not affect lamellipodia formation, indicating that this effect is specific to Hic-5. The EGF-induced lamellipodia were Rac-dependent and overexpressed WT Hic-5, but not non-phosphorylatable Hic-5 inhibited Rac activation. Our data suggest that Hic-5 tyrosine phosphorylation functions to regulate signaling associated with lamellipodia formation, a process fundamental to cell motility.
authors.affiliation: Department of Cell and Developmental Biology, State University of New York Upstate Medical University, 750 East Adams Street, Syracuse, New York 13210, USA.
authors.forename: Sara E
authors.initials: SE
authors.lastname: Hetey
authors.forename: David P
authors.initials: DP
authors.lastname: Lalonde
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Turner
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D022001:Focal Adhesions; D006801:Humans; D060588:LIM Domain Proteins; D051379:Mice; D009154:Mutation; D051419:Paxillin / Q000378:metabolism; D010766:Phosphorylation; D011554:Pseudopodia / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism*; D020744:rac GTP-Binding Proteins / Q000378:metabolism
chemical_list: D000199:Actins; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D060588:LIM Domain Proteins; D051419:Paxillin; C090090:Tgfb1i1 protein, mouse; D014443:Tyrosine; D004815:Epidermal Growth Factor; D020744:rac GTP-Binding Proteins