Resting murine neutrophils express functional alpha 4 integrins that signal through Src family kinases.
There is mounting evidence that alpha(4) (CD49d) integrins are involved in neutrophil recruitment and function during inflammatory responses. We report that all resting murine neutrophils derived from bone marrow or peripheral blood express easily detectable levels of alpha(4) integrins on their surface. These alpha(4) integrins were functional, as demonstrated by stimulation of respiratory burst when neutrophils adhered to surfaces coated with the murine vascular cell adhesion molecule-1 (mVCAM-1). Adhesion occurred via alpha(4) integrins, as preincubation of neutrophils with an anti-alpha(4)-specific Ab inhibited attachment to mVCAM-1. Direct cross-linking of the alpha(4) integrin subunit by surface-bound mAbs also elicited superoxide release and release of the secondary granule marker, lactoferrin. The functional responses that occurred downstream of alpha(4) integrin cross-linking required signaling by Src family kinases. Neutrophils derived from hck(-/-)fgr(-/-)lyn(-/-) triple-knockout or hck(-/-)fgr(-/-) double-knockout mice failed to undergo respiratory burst when plated on mVCAM-1. Triple mutant neutrophils were also defective in release of both superoxide and lactoferrin when plated on surfaces coated with mAbs directed against alpha(4). Correlated with impaired alpha(4)-induced functional responses, triple-mutant neutrophils also failed to spread and tightly adhere to anti-alpha(4) mAb-coated surfaces. This is the first direct evidence that functional alpha(4) integrins are expressed by murine PMNs, and that these surface molecules can mediate cellular responses such as tight adhesion, spreading, sustained respiratory burst, and specific granule release in vitro. Moreover the alpha(4) integrins, like all other integrins tested, use the Src family kinases to transduce intracellular signals.
Department of Laboratory Medicine, University of California, San Francisco, CA 94143, USA.
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S
Pereira
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M
Zhou
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A
Mócsai
C
C
Lowell
D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism / Q000502:physiology; D015703:Antigens, CD / Q000096:biosynthesis* / Q000276:immunology / Q000502:physiology; D002448:Cell Adhesion / Q000235:genetics / Q000276:immunology; D002462:Cell Membrane / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D002465:Cell Movement / Q000235:genetics / Q000276:immunology; D002469:Cell Separation; D003594:Cytoplasmic Granules / Q000378:metabolism; D039441:Integrin alpha4; D016023:Integrins / Q000096:biosynthesis* / Q000502:physiology; D007399:Interphase / Q000235:genetics / Q000276:immunology*; D007781:Lactoferrin / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009504:Neutrophils / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000172:deficiency / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000172:deficiency / Q000235:genetics; D051572:Proto-Oncogene Proteins c-hck; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*; D013481:Superoxides / Q000378:metabolism; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism; D019061:src-Family Kinases / Q000172:deficiency / Q000235:genetics / Q000502:physiology*
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D016023:Integrins; D011518:Proto-Oncogene Proteins; D011947:Receptors, Antigen, B-Cell; D019010:Vascular Cell Adhesion Molecule-1; D013481:Superoxides; D039441:Integrin alpha4; D011505:Protein-Tyrosine Kinases; C496632:Hck protein, mouse; D051572:Proto-Oncogene Proteins c-hck; C060902:lyn protein-tyrosine kinase; C053102:proto-oncogene proteins c-fgr; D019061:src-Family Kinases; D007781:Lactoferrin