title: Epithelial cell spreading induced by hepatocyte growth factor influences paxillin protein synthesis and posttranslational modification.
abstract: Superficial wounds in the gastrointestinal tract rapidly reseal by coordinated epithelial cell migration facilitated by cytokines such as hepatocyte growth factor (HGF)/scatter factor released in the wound vicinity. However, the mechanisms by which HGF promotes physiological and pathophysiologic epithelial migration are incompletely understood. Using in vitro models of polarized T84 and Caco-2 intestinal epithelia, we report that HGF promoted epithelial spreading and RhoA GTPase activation in a time-dependent manner. Inducible expression of enhanced green fluorescent protein-tagged dominant-negative RhoA significantly attenuated HGF-induced spreading. HGF expanded a zone of partially flattened cells behind the wound edge containing basal F-actin fibers aligned in the direction of spreading. Concomitantly, plaques positive for the focal adhesion protein paxillin were enhanced. HGF induced an increase in the translation of paxillin and, to a lesser extent, beta1-integrin. This was independent of cell-matrix adhesion through beta1-integrin. Subcellular fractionation revealed increased cosedimentation of paxillin with plasma membrane-containing fractions following HGF stimulation, without corresponding enhancements in paxillin coassociation with beta1 integrin or actin. Tyrosine phosphorylation of paxillin was reduced by HGF and was sensitive to the Src kinase inhibitor PP2. With these taken together, we propose that HGF upregulates a free cytosolic pool of paxillin that is unaffiliated with either the cytoskeleton or focal cell-matrix contacts. Thus early spreading responses to HGF may partly relate to increased paxillin availability for incorporation into, and turnover within, dynamic cytoskeletal/membrane complexes whose rapid and transient adhesion to the matrix drives migration.
authors.affiliation: Dept. of Pathology and Laboratory Medicine, Emory Univ., Rm. 105E, Whitehead Research Bldg., 615 Michael St., Atlanta, GA 30322, USA. anusrat@emory.edu
authors.forename: Ann M
authors.initials: AM
authors.lastname: Hopkins
authors.forename: Matthias
authors.initials: M
authors.lastname: Bruewer
authors.forename: G Thomas
authors.initials: GT
authors.lastname: Brown
authors.forename: A'Drian A
authors.initials: AA
authors.lastname: Pineda
authors.forename: Julie J
authors.initials: JJ
authors.lastname: Ha
authors.forename: L Matthew
authors.initials: LM
authors.lastname: Winfree
authors.forename: Shaun V
authors.initials: SV
authors.lastname: Walsh
authors.forename: Brian A
authors.initials: BA
authors.lastname: Babbin
authors.forename: Asma
authors.initials: A
authors.lastname: Nusrat
mesh_terms: D000199:Actins / Q000378:metabolism; D018938:Caco-2 Cells; D002462:Cell Membrane / Q000378:metabolism; D002465:Cell Movement / Q000502:physiology; D002478:Cells, Cultured; D003106:Colon / Q000166:cytology; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D022001:Focal Adhesions / Q000187:drug effects / Q000502:physiology; D017228:Hepatocyte Growth Factor / Q000494:pharmacology*; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D015854:Up-Regulation; D020742:rhoA GTP-Binding Protein / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D000199:Actins; D003598:Cytoskeletal Proteins; D019012:Integrin beta1; C496061:PXN protein, human; D051419:Paxillin; D010750:Phosphoproteins; D017228:Hepatocyte Growth Factor; D019061:src-Family Kinases; D020742:rhoA GTP-Binding Protein