Differences in binding to the ILK complex determines kindlin isoform adhesion localization and integrin activation

J Cell Sci. 2014 Oct 1;127(Pt 19):4308-21. doi: 10.1242/jcs.155879. Epub 2014 Aug 1.

Abstract

Kindlins are essential FERM-domain-containing focal adhesion (FA) proteins required for proper integrin activation and signaling. Despite the widely accepted importance of each of the three mammalian kindlins in cell adhesion, the molecular basis for their function has yet to be fully elucidated, and the functional differences between isoforms have generally not been examined. Here, we report functional differences between kindlin-2 and -3 (also known as FERMT2 and FERMT3, respectively); GFP-tagged kindlin-2 localizes to FAs whereas kindlin-3 does not, and kindlin-2, but not kindlin-3, can rescue α5β1 integrin activation defects in kindlin-2-knockdown fibroblasts. Using chimeric kindlins, we show that the relatively uncharacterized kindlin-2 F2 subdomain drives FA targeting and integrin activation. We find that the integrin-linked kinase (ILK)-PINCH-parvin complex binds strongly to the kindlin-2 F2 subdomain but poorly to that of kindlin-3. Using a point-mutated kindlin-2, we establish that efficient kindlin-2-mediated integrin activation and FA targeting require binding to the ILK complex. Thus, ILK-complex binding is crucial for normal kindlin-2 function and differential ILK binding contributes to kindlin isoform specificity.

Keywords: Focal adhesion; Integrin; Integrin activation; Integrin-linked kinase; Kindlin.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Animals
  • CHO Cells
  • Cricetulus
  • Focal Adhesions / metabolism*
  • HEK293 Cells
  • Humans
  • Integrins / metabolism*
  • Membrane Proteins / metabolism*
  • Mice
  • Molecular Sequence Data
  • NIH 3T3 Cells
  • Neoplasm Proteins / metabolism*
  • Protein Isoforms
  • Protein-Serine-Threonine Kinases / metabolism*
  • Signal Transduction

Substances

  • FERMT3 protein, human
  • Integrins
  • Membrane Proteins
  • Neoplasm Proteins
  • Protein Isoforms
  • integrin-linked kinase
  • Protein-Serine-Threonine Kinases