Hepatic stellate cells (HSCs) play a key role in the development of liver fibrosis. Integrin receptors contribute to the regulation cell adhesion and migration. The aim of this study was to evaluate the interaction between focal adhesion kinase (FAK) and phospholipase C gamma (PLC gamma) potentially involved in HSC integrin- mediated signaling pathways.

Interaction between FAK and PLC gamma was determined by immunoprecipitation and immunoblotting. HSC chemotactic activity was evaluated using the Boyden chamber technique.

HSC adhesion to extracellular matrix components (collagen type I and IV, laminin, and fibronectin) and antibody-mediated beta 1 ligation elicited increased tyrosine phosphorylation of FAK. HSC adhesion to different extracellular matrix components did not result in PLC gamma tyrosine phosphorylation. However, HSC adhesion induced association between PLC gamma and FAK. All extracellular matrix components tested stimulated HSC chemotactic activity only at high concentrations. On the contrary, platelet-derived growth factor, homodimer BB (PDGF-BB), was able to stimulate HSC migration in a dose- dependent manner; this event, occurring in the presence of FAK phosphorylation, was associated to a dose-dependent PLC gamma tyrosine phosphorylation.

These findings provide the first evidence that PLC gamma recruitment by FAK during HSC adhesion is an important process implicating a link between integrin and PDGF-mediated signaling pathways to regulate HSC adhesion and motility. (Gastroenterology 1997 Feb;112(2):522-31)