Regulation of Focal Adhesion Kinase by Its Amino-Terminal Domain through an Autoinhibitory Interaction

Abstract

We have investigated a role for the amino-terminal FERM-like domain of the focal adhesion kinase (FAK) as a negative regulator of its own activity and phosphorylation state. Deletion of the first 375 amino acids from the amino terminus of FAK increases its catalytic activity in vitro, its phosphorylation when expressed in mammalian cells, and the phosphorylation of a FAK substrate, paxillin. Deletion mutants are phosphorylated in suspension, suggesting that they are no longer regulated by adhesion. The amino terminus of FAK can interact with the kinase domain of FAK in vitro and in vivo, suggesting that it might act as an autoinhibitor of FAK activity. The amino terminus of FAK can act in trans to inhibit FAK phosphorylation when expressed in mammalian cells or to directly inhibit FAK activity in vitro. Expression of the amino terminus of FAK inhibits cell cycle progression in CHO cells, consistent with its inhibition of FAK phosphorylation and function in trans. A glutathione S-transferase fusion protein containing the cytoplasmic tail of the β1 integrin stimulates FAK activity in vitro, suggesting that FAK could be regulated by molecular interactions with the amino terminus. Based on these and previous data, we propose a working model for activation of FAK in cell adhesion.

ACKNOWLEDGMENTS

Lee Ann Cooper and Tang-Long Shen contributed equally to the work presented in this paper.

We are grateful to F. Matsumura of Rutgers University for recombinant baculovirus encoding His-tagged FAK and to C. E. Turner of SUNY Health Science Center in Syracuse for pEGFP-Paxillin. We thank our colleagues Luis Rodriguez, Daniel Rhoades, Xiaoyang Wu, Boyi Gan, Tamas Nagy, Xu Peng, and Zara Melkoumian for their critical reading of the manuscript and helpful comments.

This research was supported by NIH grants GM48050 and GM52890 to J.-L.G.