Targeted deletion of integrin-linked kinase reveals a role in T-cell chemotaxis and survival.
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.
Liu
Emerson
E
Center for Immunology and Inflammatory Diseases, Massachusetts General Hospital, Charlestown, 02129, USA.
Sinha
Sumita
S
Williams
Christine
C
Cyrille
Marcoli
M
Heller
Eric
E
Snapper
Scott B
SB
Georgopoulos
Katia
K
St-Arnaud
Rene
R
Force
Thomas
T
Dedhar
Shoukat
S
Gerszten
Robert E
RE
D000818:Animals; D017209:Apoptosis; D054415:Chemokine CCL19; D054377:Chemokine CXCL12; D019742:Chemokines, CC / Q000378:metabolism; D019743:Chemokines, CXC / Q000378:metabolism; D002634:Chemotaxis, Leukocyte / Q000235:genetics; D017353:Gene Deletion; D018390:Gene Targeting; D051379:Mice; D018345:Mice, Knockout; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000201:enzymology* / Q000276:immunology*; D000099200:Scaffold Protein ILK
D054415:Chemokine CCL19; D054377:Chemokine CXCL12; D019742:Chemokines, CC; D019743:Chemokines, CXC; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D012694:Serine; D000099200:Scaffold Protein ILK; C515461:Ccl19 protein, mouse; C515256:Cxcl12 protein, mouse