LKB1 represses focal adhesion kinase (FAK) signaling via a FAK-LKB1 complex to regulate FAK site maturation and directional persistence

J Biol Chem. 2013 Jun 14;288(24):17663-74. doi: 10.1074/jbc.M112.444620. Epub 2013 May 1.

Abstract

Liver kinase β1 (LKB1, also known as STK11) is a serine/threonine kinase that has multiple cellular functions including the regulation of cell polarity and motility. Murine proteomic studies show that LKB1 loss causes aberrant adhesion signaling; however, the mechanistic underpinnings of this relationship are unknown. We show that cells stably depleted of LKB1 or its co-activator STRADα have increased phosphorylation of focal adhesion kinase (FAK) at Tyr(397)/Tyr(861) and enhanced adhesion to fibronectin. LKB1 associates in a complex with FAK and LKB1 accumulation at the cellular leading edge is mutually excluded from regions of activated Tyr(397)-FAK. LKB1-compromised cells lack directional persistence compared with wild-type cells, but this is restored through subsequent pharmacological FAK inhibition or depletion, showing that cell directionality is mediated through LKB1-FAK signaling. Live cell confocal imaging reveals that LKB1-compromised cells lack normal FAK site maturation and turnover, suggesting that defects in adhesion and directional persistence are caused by aberrant adhesion dynamics. Furthermore, re-expression of full-length wild-type or the LKB1 N-terminal domain repressed FAK activity, whereas the kinase domain or C-terminal domain alone did not, indicating that FAK suppression is potentially regulated through the LKB1 N-terminal domain. Based upon these results, we conclude that LKB1 serves as a FAK repressor to stabilize focal adhesion sites, and when LKB1 function is compromised, aberrant FAK signaling ensues, resulting in rapid FAK site maturation and poor directional persistence.

Keywords: Adhesion; Cell Migration; Cell Motility; Epithelial Mesenchymal Transition; Focal Adhesion Kinase; Imaging; LKB1.

Publication types

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

MeSH terms

  • AMP-Activated Protein Kinase Kinases
  • Cell Adhesion
  • Cell Line, Tumor
  • Cell Movement*
  • Cell Polarity
  • Focal Adhesion Kinase 1 / antagonists & inhibitors
  • Focal Adhesion Kinase 1 / genetics
  • Focal Adhesion Kinase 1 / metabolism*
  • Focal Adhesions / metabolism
  • Gene Knockdown Techniques
  • Humans
  • Phosphorylation
  • Protein Binding
  • Protein Interaction Domains and Motifs
  • Protein Multimerization
  • Protein Processing, Post-Translational
  • Protein Serine-Threonine Kinases / chemistry
  • Protein Serine-Threonine Kinases / physiology*
  • Quinolones / pharmacology
  • RNA, Small Interfering / genetics
  • Signal Transduction*
  • Single-Cell Analysis
  • Sulfones / pharmacology

Substances

  • 6-(4-(3-(methylsulfonyl)benzylamino)-5-(trifluoromethyl)pyrimidin-2-ylamino)-3,4-dihydroquinolin-2(1H)-one
  • Quinolones
  • RNA, Small Interfering
  • Sulfones
  • Focal Adhesion Kinase 1
  • PTK2 protein, human
  • Protein Serine-Threonine Kinases
  • STK11 protein, human
  • AMP-Activated Protein Kinase Kinases