Activation and internalization of p56lck upon CD45 triggering of Jurkat cells.
Relationships between CD45 and p56lck have been suggested by co-immunoprecipitation of both proteins and by dephosphorylation of the p56lck regulatory site, Tyr 505, by CD45 in vitro. We investigated whether the kinase activity of p56lck is modulated in T cells triggered via CD45. We showed that incubation of Jurkat cells with a combination of two anti-CD45 monoclonal antibodies (mAb) (MC5/2 + D3/9) induced an increase in p56lck kinase activity, while a single mAb did not. Under these conditions, p56lck underwent two consecutive waves of activation. This was accompanied by internalization of the kinase and by a time-dependent increased accessibility of CD45 phosphatase at the plasma membrane. Similarly, activation and internalization of p56lck were observed using a combination of anti-CD45 (MC5/2) and anti-CD2 (T11(2)) mAb, suggesting that a functional complex consisting of CD45, CD2 and p56lck was formed upon cell triggering. Taken together, these results suggests that: (i) CD45 participates in the regulation of p56lck kinase activity in vivo and that (ii) CD45 could play a mediator role in the stimulation and endocytosis of p56lck through the CD2 pathway.
Marie-Cardine
A
A
INSERUM U332, Institut Cochin de Génétique Moléculaire, Paris, France.
Maridonneau-Parini
I
I
Fischer
S
S
D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology / Q000502:physiology*; D015153:Blotting, Western; D018801:CD2 Antigens; D004789:Enzyme Activation / Q000276:immunology; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D017493:Leukocyte Common Antigens / Q000276:immunology / Q000502:physiology*; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D010449:Peptide Mapping; D010744:Phosphoric Monoester Hydrolases / Q000502:physiology; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000276:immunology / Q000502:physiology*; D013601:T-Lymphocytes / Q000201:enzymology* / Q000276:immunology*; D014357:Trypsin / Q000378:metabolism; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D018801:CD2 Antigens; D011971:Receptors, Immunologic; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D010744:Phosphoric Monoester Hydrolases; D017493:Leukocyte Common Antigens; D014357:Trypsin