Regulation of Focal Adhesion Kinase through a Direct Interaction with an Endogenous Inhibitor

Biochemistry. 2017 Sep 5;56(35):4722-4731. doi: 10.1021/acs.biochem.7b00616. Epub 2017 Aug 23.


Focal adhesion kinase (FAK) plays a key role in integrin and growth factor signaling pathways. FAK-related non-kinase (FRNK) is an endogenous inhibitor of FAK that shares its primary structure with the C-terminal third of FAK. FAK S910 phosphorylation is known to regulate FAK protein-protein interactions, but the role of the equivalent site on FRNK (S217) is unknown. Here we determined that S217 is highly phosphorylated by ERK in cultured rat aortic smooth muscle cells. Blocking phosphorylation by mutation (S217A) greatly increased FRNK inhibitory potency, resulting in strong inhibition of FAK autophosphorylation at Y397 and induction of smooth muscle cell apoptosis. FRNK has been proposed to compete for FAK anchoring sites in focal adhesions, but we did not detect displacement of FAK by WT-FRNK or superinhibitory S217A-FRNK. Instead, we found FRNK interacted directly with FAK, and this interaction is markedly strengthened for the superinhibitory S217A-FRNK. The results suggest that FRNK limits growth and survival signaling pathways by binding directly to FAK in an inhibitory complex, and this inhibition is relieved by phosphorylation of FRNK at S217.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Focal Adhesion Kinase 1
  • Focal Adhesion Protein-Tyrosine Kinases / metabolism*
  • Gene Expression Regulation, Enzymologic / physiology*
  • Muscle, Smooth, Vascular / cytology
  • Myocytes, Smooth Muscle / enzymology*
  • Phosphorylation
  • Protein Kinase Inhibitors / metabolism*
  • Rats
  • Signal Transduction / physiology


  • Protein Kinase Inhibitors
  • Focal Adhesion Kinase 1
  • Focal Adhesion Protein-Tyrosine Kinases
  • Ptk2 protein, rat