Targeted deletion of integrin-linked kinase reveals a role in T-cell chemotaxis and survival

Mol Cell Biol. 2005 Dec;25(24):11145-55. doi: 10.1128/MCB.25.24.11145-11155.2005.

Abstract

Integrin-linked kinase (ILK) is a serine/threonine kinase that is important in cell-matrix interactions and cell signaling. To examine the role of ILK in leukocyte trafficking and survival, we generated T cell-specific ILK knockouts by breeding ILK(flox/flox) mice to transgenic mice expressing Cre recombinase under control of the Lck proximal promoter. Thymic T cells from Lck-Cre(+)/ILK(flox/flox) mice had a marked reduction (>95%) in ILK protein levels. Thymic cellularity was comparable in 3- to 4-week-old mice, but a threefold diminution of thymic T cells became evident by 6 to 8 weeks of age in the T cell-specific ILK knockout mice due to increased cell death of double-positive (DP) T cells. Analysis of peripheral T cells by quantitative PCR and by breeding Lck-Cre(+)/ILK(flox/flox) mice to a YFP-transgenic reporter strain demonstrated an approximate 20-fold enrichment of ILK-competent cells, suggesting these cells have a competitive advantage in trafficking to and/or survival in peripheral lymphatic organs. We explored mechanisms related to altered cell trafficking and survival that might explain the decreases in thymic cellularity and enrichment for ILK-competent cells in the spleen and lymph nodes. We observed a >50% reduction in chemotaxis of ILK-deficient T cells to the chemokines CXCL12 (stromal cell-derived factor [SDF]-1alpha) and CCL19 (macrophage inflammatory protein [MIP]-3beta), as well as enhanced apoptosis of ILK-deficient cells upon stress. Signaling studies in ILK-deficient T cells demonstrated diminished phosphorylation of Akt on the activating phosphorylation site, Ser 473, and a concordant decrease in Akt kinase activity following stimulation with the chemokine SDF-1. Rac1 activation was also markedly diminished in ILK-deficient T cells following chemokine stimulation. These data extend the role of ILK to immune-cell trafficking and survival via modulation of Akt- and Rac-dependent substrates, and have implications for cell recruitment in both homeostatic and pathological processes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis
  • Chemokine CCL19
  • Chemokine CXCL12
  • Chemokines, CC / metabolism
  • Chemokines, CXC / metabolism
  • Chemotaxis, Leukocyte* / genetics
  • Gene Deletion
  • Gene Targeting
  • Mice
  • Mice, Knockout
  • Phosphorylation
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / physiology*
  • Proto-Oncogene Proteins c-akt / metabolism
  • Serine / metabolism
  • Signal Transduction
  • T-Lymphocytes / enzymology*
  • T-Lymphocytes / immunology*

Substances

  • Ccl19 protein, mouse
  • Chemokine CCL19
  • Chemokine CXCL12
  • Chemokines, CC
  • Chemokines, CXC
  • Cxcl12 protein, mouse
  • Serine
  • integrin-linked kinase
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt