Leukocyte phosphoinositide-3 kinase {gamma} is required for chemokine-induced, sustained adhesion under flow in vivo.
During inflammation, leukocytes roll along the wall of postcapillary venules scanning the surface for immobilized CXCL1, a chemokine that triggers firm adhesion by activating CXCR2 on the neutrophil. PI-3K are signaling molecules important in cellular processes, ranging from cellular differentiation to leukocyte migration. PI-3Kgamma can be activated directly by the betagamma dimer of heterotrimeric G proteins coupled to CXCR2. Here, we used in vivo and ex vivo intravital microscopy models to test the role of PI-3Kgamma in leukocyte arrest. PI-3Kgamma null mice showed an 80% decrease in CXCL1-induced leukocyte adhesion in venules of the exteriorized mouse cremaster muscle. In wild-type mice, rolling leukocytes showed rapid and sustained adhesion, but in PI-3Kgamma(-/-) mice, adhesion was not triggered at all or was transient, suggesting that absence of PI-3Kgamma interferes with integrin bond strengthening. Wild-type mice reconstituted with PI-3Kgamma null bone marrow showed a 50% decrease in CXCL1-induced leukocyte adhesion. In a blood-perfused micro-flow chamber, leukocytes from PI-3Kgamma(-/-) mice showed a defect in adhesion on a P-selectin/ICAM-1/CXCL1 substrate, indicating that leukocyte PI-3Kgamma was required for adhesion. The adhesion defect in PI-3Kgamma(-/-) mice was as severe as that in mice lacking LFA-1, the major integrin responsible for neutrophil adhesion. We conclude that the gamma isoform of PI-3K must be functional in leukocytes to allow efficient adhesion from rolling in response to chemokine stimulation.
Smith
David F
DF
Department of Molecular Physiology and Biophysics, University of Virginia, Charlottesville, Virginia 22908, USA.
Deem
Tracy L
TL
Bruce
Anthony C
AC
Reutershan
Jörg
J
Wu
Daniel
D
Ley
Klaus
K
D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D054360:Chemokine CXCL1; D019743:Chemokines, CXC / Q000378:metabolism* / Q000494:pharmacology; D058544:Class Ib Phosphatidylinositol 3-Kinase; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D007527:Isoenzymes / Q000172:deficiency / Q000378:metabolism; D036904:Leukocyte Rolling / Q000187:drug effects / Q000502:physiology*; D007962:Leukocytes / Q000166:cytology / Q000201:enzymology*; D051379:Mice; D018345:Mice, Knockout; D018482:Muscle, Skeletal / Q000098:blood supply / Q000166:cytology / Q000201:enzymology; D019007:P-Selectin / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000172:deficiency / Q000378:metabolism*; D014699:Venules / Q000166:cytology / Q000201:enzymology
D054360:Chemokine CXCL1; D019743:Chemokines, CXC; C475895:Cxcl1 protein, mouse; D007527:Isoenzymes; D019007:P-Selectin; D018799:Intercellular Adhesion Molecule-1; D019869:Phosphatidylinositol 3-Kinases; D058544:Class Ib Phosphatidylinositol 3-Kinase; C546764:Pik3cg protein, mouse; D020962:Heterotrimeric GTP-Binding Proteins