Integrins are a family of cell surface adhesion molecules which mediate cell adhesion and initiate signaling pathways that regulate cell spreading, migration, differentiation, and proliferation. TGF-b is a multifunctional factor that induces a wide variety of cellular processes. In this study, we show that, TGF-b1 treatment enhanced the amount of a5b1 integrin on cell surface, the mRNA level of a5 subunit, and subsequently stimulated cell adhesion onto a fibronectin (Fn) and laminin (Ln) matrix in SMMC-7721 cells. TGF-b1 could also promote cell migration. Furthermore, our results showed that TGF-b1 treatment stimulated the tyrosine phosphorylation level of FAK, which can be activated by the ligation and clustering of integrins. PTEN can directly dephosphorylate FAK, and the results that TGF-b1 could down-regulate PTEN at protein level suggested that TGF-b1 might stimulate FAK phosphorylation through increasing integrin signaling and reducing dephosphorylation of FAK. These studies indicated that TGF-b1 and integrin-mediated signaling act synergistically to enhance cell adhesion and migration and affect downstream signaling molecules of hepatocarcinoma cells.

How cells couple and uncouple regulation of cellular processes such as shape change and survival is an important question in molecular cell biology. PINCH-1, a widely expressed protein consisting of five LIM domains and a C-terminal tail, is an essential focal adhesion protein with multiple functions including regulation of the integrin-linked kinase (ILK) level, cell shape, and survival signaling. We show here that the LIM1-mediated interaction with ILK regulates all these three processes. By contrast, the LIM4-mediated interaction with Nck-2, which regulates cell morphology and migration, is not required for the control of the ILK level and survival. Remarkably, a short 15-residue tail C-terminal to LIM5 is required for both cell shape modulation and survival, albeit it is not required for the control of the ILK level. The C-terminal tail not only regulates PINCH-1 localization to focal adhesions but also functions after it localizes there. These findings suggest that PINCH-1 functions as a molecular platform for coupling and uncoupling diverse cellular processes via overlapping but yet distinct domain interactions.