Regulation of cell-matrix adhesion dynamics and Rac-1 by integrin linked kinase

FASEB J. 2006 Jul;20(9):1489-91. doi: 10.1096/fj.05-4579fje. Epub 2006 May 24.

Abstract

Extracellular matrix (ECM) receptors of the integrin family initiate changes in cell shape and motility by recruiting signaling components that coordinate these events. Integrin-linked kinase (ILK) is one such partner of beta1 integrins that participates in dynamic rearrangement of cell-matrix adhesions and cell spreading by mechanisms that are not well understood. To further elucidate the role of ILK in these events, we engineered a chimeric molecule comprising ILK fused to a membrane-targeted green fluorescent protein (ILK-GFP-F). ILK-GFP-F is highly enriched in cell-matrix adhesions, and its expression in fibroblasts leads to an accumulation of focal adhesions (2-5 microm) and elongated adhesions (>5 microm). ILK-GFP-F enhances cell spreading on fibronectin and induces a constitutive increase in the levels of GTP-bound Rac-1. Conversely, ILK knock-down by siRNA transfection decreases active Rac-1. Endogenous ILK was found to associate with PKL (paxillin kinase linker) and the Rac/Cdc42 guanine nucleotide exchange factor betaPIX. Further, expression of a dominant negative betaPIX mutant reversed the increase in active Rac-1 levels of ILK-GFP-F-expressing cells, thus placing betaPIX in the pathway leading from ILK to Rac-1 activation. However, expression of constitutively active Rac only partially restores the spreading defects of ILK-depleted cells, suggesting that an additional ILK-dependent signal is required for cell spreading.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Aorta
  • Cattle
  • Cells, Cultured
  • Endothelium, Vascular / cytology
  • Endothelium, Vascular / physiology*
  • Extracellular Matrix / physiology*
  • Genetic Vectors
  • Kinetics
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / physiology*
  • RNA, Small Interfering / genetics
  • Recombinant Fusion Proteins / metabolism
  • Signal Transduction / physiology
  • Transfection
  • rac1 GTP-Binding Protein / genetics
  • rac1 GTP-Binding Protein / metabolism*

Substances

  • RNA, Small Interfering
  • Recombinant Fusion Proteins
  • integrin-linked kinase
  • Protein Serine-Threonine Kinases
  • rac1 GTP-Binding Protein