Tyrosine phosphorylation of focal adhesion kinase by PDGF is dependent on Ras in human hepatic stellate cells

Vlnicio Carloni, Massimo Plnzani, Sabrina Glusti, Roberto G. Romanelli, Maurizio Parola, Glorgio Bellomo, Paola Failli, Andrew D. Hamilton, Said M. Sebti, Giacomo Laffi, Paolo Gentilini

Research output: Contribution to journalArticle

Abstract

Focal adhesion kinase (FAK) is a widely expressed nonreceptor tyrosine kinase found in focal adhesions. FAK has been indicated as a point of convergence of other signaling pathways including platelet-derived growth factor (PDGF) receptors, and recently, FAK tyrosine phosphorylation has been shown to be stimulated by PDGF. In the present study we assessed the role of Ras as a possible intermediate protein regulating PDGF-induced FAK tyrosine phosphorylation in human hepatic stellate cells (HSCs), liver-specific pericytes primarily involved in the pathogenesis of liver fibrosis. For this purpose, cells were first subjected to retroviral-mediated gene transfer with a dominant-negative mutant of Ras (N17Ras). This resulted in a marked inhibition of PDGF-induced FAK tyrosine phosphorylation together with the expected reduction of PDGF-induced extracellular signal-regulated kinase activity (ERK). Afterward, the effects of pharmacological agents potentially affecting Ras isoprenylation were evaluated. PDGF-induced FAK tyrosine phosphorylation, ERK activity and intracellular calcium increase, as well as the biological effects of this growth factor, (i.e., mitogenesis and cell migration) were effectively blocked by GGTI-298, an inhibitor of geranylgeranyltransferase I. Inhibition of Ras processing obtained with FTI- 277, an inhibitor of farnesyltransferase, resulted in detectable effects only at high doses. Taken together, these results establish that Ras operates as a protein-linking PDGF-β receptor to FAK in human HscS, and that signaling molecules requiring geranylgeranylation may also be involved in this process.

Original languageEnglish (US)
Pages (from-to)131-140
Number of pages10
JournalHepatology
Volume31
Issue number1
DOIs
StatePublished - 2000

ASJC Scopus subject areas

  • Hepatology

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