Purpose: Hepatocyte growth factor (HGF) has been implicated in retinal pigment epithelial (RPE) cell proliferation and migration that occurs in proliferative retinal diseases such as proliferative vitreoretinopathy (PVR). The aim of this study is to investigate HGF induced signaling pathways that lead to RPE cell migration. Methods: Localization of β-catenin was determined by immunofluorescence. HGF induced migration of ARPE-19 cells was studied using a quantitative migration assay after wounding in the presence of a DNA polymerase inhibitor, and in the presence or absence of a mitogen activated protein kinase (MAP kinase) kinase inhibitor. C-jun expression was determined by semi-quantitative RT-PCR and by Northern blot analysis. P42/p44 MAP kinase activity was determined by western blot and by an immunoprecipitation kinase assay. Tyrosine phosphorylation of the HGF receptor (HGFR or c-met) and β-catenin was determined by immunoprecipitation and western blot analysis. Transactivation activity of β-catenin was determined by luciferase reporter gene analysis. Results: β-catenin and E-cadherin were co-localized on the basal surface of the RPE in vivo. Diffusion of the cell surface-localized β-catenin occurs in migratory cells in vitro in the presence of HGF. HGF induced a MAP kinase dependent ARPE-19 cell migration, which is accompanied with a transient increase of c-jun expression and concomitant increases of MAP kinase activity, tyrosine phosphorylation of HGFR and β-catenin, increased cytosolic levels of β-catenin, and transactivation activity of β-catenin. Tyrosine phosphorylation of HGFR and β-catenin occurs in the primary or passaged RPE cultures or proliferative ARPE-19 cells, but not freshly isolated RPE or differentiated ARPE-19 cells. Conclusions: This study defines the signal transduction pathways activated by HGF in RPE cells, leading to an increase in the MAP kinase activity and free pool of β-catenin, and changes in gene expression. These findings are consistent with the hypothesis that both β-catenin and MAP kinases are components of the HGF induced RPE migration that occurs in proliferative retinal diseases.
|Original language||English (US)|
|Number of pages||11|
|State||Published - 2002|
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