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

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

Author information

1
Department of Pharmacology, Yale University, New Haven, CT 06520, USA.
2
Department of Cell Biology, Yale University, New Haven, CT 06520, USA.
3
Department of Pharmacology, Yale University, New Haven, CT 06520, USA Institute for Stem Cell Biology and Regenerative Medicine, Bangalore, Karnataka 560065, India.
4
Department of Pharmacology, Yale University, New Haven, CT 06520, USA Department of Cell Biology, Yale University, New Haven, CT 06520, USA david.calderwood@yale.edu.

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

PMID:
25086068
PMCID:
PMC4179494
DOI:
10.1242/jcs.155879
[Indexed for MEDLINE]
Free PMC Article
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