CD44-initiated cell spreading induces Pyk2 phosphorylation, is mediated by Src family kinases, and is negatively regulated by CD45.
CD44 is a cell adhesion molecule implicated in leukocyte adhesion and migration, co-stimulation of T cells, and tumor metastasis. CD45 is a leukocyte-specific protein tyrosine phosphatase that dephosphorylates the Src family kinases, Lck and Fyn, in T cells. Positive regulation of Lck by CD45 is required for its effective participation in T cell receptor signaling events. Here, immobilized CD44 antibody induced a distinctive cell spreading in CD45(-), but not CD45(+), T cells, and this correlated with the induction of tyrosine-phosphorylated proteins. Two focal adhesion family kinases, Pyk2 and, to a lesser extent, FAK were inducibly phosphorylated, as was a potential substrate, Cas. CD44-mediated cell spreading and induced tyrosine phosphorylation were prevented by the Src family kinase inhibitor, PP2. Furthermore, 2-fold more Lck associated with CD44 in the low density sucrose fraction from CD45(-) T cells compared with CD45(+) T cells, suggesting that CD45 may regulate the association of Lck with CD44 in this fraction. Therefore, in CD45(-) T cells, CD44 signaling is mediated by Src family kinases, and this leads to Pyk2 phosphorylation, cytoskeletal changes, and cell spreading. This implicates CD45 in the negative regulation of Src family kinase-mediated CD44 signaling leading to T cell spreading.
Li
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R
Department of Microbiology and Immunology, 6174 University Blvd., University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
Wong
N
N
Jabali
M D
MD
Johnson
P
P
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D000081247:CSK Tyrosine-Protein Kinase; D002465:Cell Movement / Q000502:physiology; D002499:Centrifugation, Density Gradient; D051418:Focal Adhesion Kinase 2; D018960:Hyaluronan Receptors / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D017493:Leukocyte Common Antigens / Q000187:drug effects / Q000502:physiology*; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000378:metabolism; D016399:Lymphoma, T-Cell; D051379:Mice; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051381:Rats; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000502:physiology; D011994:Recombinant Proteins / Q000378:metabolism; D013601:T-Lymphocytes / Q000166:cytology / Q000502:physiology*; D014162:Transfection; D014407:Tumor Cells, Cultured; D019061:src-Family Kinases
D000911:Antibodies, Monoclonal; D018960:Hyaluronan Receptors; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D011994:Recombinant Proteins; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D051418:Focal Adhesion Kinase 2; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); C496053:Ptk2b protein, mouse; C496054:Ptk2b protein, rat; D019061:src-Family Kinases; D017493:Leukocyte Common Antigens