A role for the protein tyrosine phosphatase CD45 in macrophage adhesion through the regulation of paxillin degradation.
CD45 is a protein tyrosine phosphatase expressed on all cells of hematopoietic origin that is known to regulate Src family kinases. In macrophages, the absence of CD45 has been linked to defects in adhesion, however the molecular mechanisms involved remain poorly defined. In this study, we show that bone marrow derived macrophages from CD45-deficient mice exhibit abnormal cell morphology and defective motility. These defects are accompanied by substantially decreased levels of the cytoskeletal-associated protein paxillin, without affecting the levels of other proteins. Degradation of paxillin in CD45-deficient macrophages is calpain-mediated, as treatment with a calpain inhibitor restores paxillin levels in these cells and enhances cell spreading. Inhibition of the tyrosine kinases proline-rich tyrosine kinase (Pyk2) and focal adhesion kinase (FAK), kinases that are capable of mediating tyrosine phosphorylation of paxillin, also restored paxillin levels, indicating a role for these kinases in the CD45-dependent regulation of paxillin. These data demonstrate that CD45 functions to regulate Pyk2/FAK activity, likely through the activity of Src family kinases, which in turn regulates the levels of paxillin to modulate macrophage adhesion and migration.
Department of Medical Microbiology and Immunology, and the Li Ka Shing Institute of Virology, University of Alberta, Edmonton, Alberta, Canada.
Joëlle
J
St-Pierre
Hanne L
HL
Ostergaard
D000818:Animals; D015153:Blotting, Western; D002154:Calpain / Q000378:metabolism; D002448:Cell Adhesion / Q000235:genetics; D002465:Cell Movement / Q000235:genetics; D048430:Cell Shape / Q000235:genetics; D002478:Cells, Cultured; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism*; D051417:Focal Adhesion Kinase 1 / Q000378:metabolism; D051418:Focal Adhesion Kinase 2 / Q000378:metabolism; D017493:Leukocyte Common Antigens / Q000235:genetics / Q000378:metabolism*; D007976:Leupeptins / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D051419:Paxillin / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D059748:Proteolysis / Q000187:drug effects; D059008:Time-Lapse Imaging / Q000379:methods; D019061:src-Family Kinases / Q000378:metabolism
D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D051419:Paxillin; C063261:acetylleucyl-leucyl-norleucinal; D051417:Focal Adhesion Kinase 1; D051418:Focal Adhesion Kinase 2; C496051:Ptk2 protein, mouse; C496053:Ptk2b protein, mouse; D019061:src-Family Kinases; D017493:Leukocyte Common Antigens; C516770:Ptprc protein, mouse; D002154:Calpain