Analysis of FAK-associated signaling pathways in the regulation of cell cycle progression

Focal adhesion kinase (FAK) is an important mediator of signal transduction pathways initiated by integrins in cell migration, survival and cell cycle regulation. The ability of FAK to mediate integrin signaling in the regula tion of cell cycle progression depends on the phosphorylation of Tyr397, wh ich implies a functional significance for the formation of FAK signaling co mplexes with Src, phosphatidylinositol-3-kinase (PI3K) and Grb7. We have pr eviously described a FAK mutant, D395A, that selectively disrupts FAK bindi ng to PI3K, but allows FAK association with Src, Using this mutation in a m islocalized FAK mutant background, we show here that formation of a FAK/PI3 K complex is not sufficient for cell cycle progression but the formation of a FAK/Src complex plays an essential role. We also show that mutation of D 395 to A disrupted FAK association with Grb7. This suggests that a FAK/Grb7 complex is not involved in the cell cycle regulation either, which is supp orted by direct analysis of cells expressing a dominant negative Grb7 const ruct. Finally, we provide evidence that the Src-dependent association of FA K with Grb2 and p130(Cas) are both required for the regulation of cell cycl e progression by FAK, Together, these studies identify important FAK downst ream signaling pathways in cell cycle regulation. (C) 2000 Federation of Eu ropean Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.