In vivo association of CD5 with tyrosine-phosphorylated ZAP-70 and p21 phospho-zeta molecules in human CD3+ thymocytes.
CD5 is a 67-kDa T cell surface Ag that can be found physically associated with the CD3-TCR molecular complex. In different experimental models it has been shown to act as a costimulatory receptor for T cell activation. Unexpectedly, studies in CD5-deficient mice suggested a negative role for the CD5 Ag in CD3-TCR signaling in the thymus. In this report we assessed the constitutive interactions of CD5 in freshly isolated human thymocytes with signaling elements of the CD3-TCR complex. We determined that the ZAP-70 protein tyrosine kinase was present in CD5 immunoprecipitates. The two molecules were constitutively tyrosine phosphorylated in a complex also associating with unphosphorylated as well as phosphorylated zeta-chains. Although both p21 and p23 tyrosine-phosphorylated forms of zeta as well as phospho-CD3 epsilon molecules were constitutively present in human thymocytes and could be immunoprecipitated with ZAP-70- or CD3 epsilon-specific Abs, the p21 species of zeta was predominant in CD5 immune complexes. The interaction between CD5 and ZAP-70 was not observed in CD3-negative thymocytes, where the constitutive tyrosine phosphorylation of ZAP-70 was very low. We conclude that CD5 may affect in vivo the signaling capacity of TCRs expressed by human thymocytes by altering the phosphorylation state of CD3 and/or by retaining ZAP-70 with the p21 species of zeta.
Gary-Gouy
H
H
Laboratoire d'Immunologie Cellulaire, Centre National de Recherche Scientifique, Centre Hospitalier Pitié-Salpêtrière, Paris, France.
Lang
V
V
Sarun
S
S
Boumsell
L
L
Bismuth
G
G
D019921:Biotinylation; D018956:CD5 Antigens / Q000378:metabolism*; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008565:Membrane Proteins / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism*; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D016176:T-Lymphocyte Subsets / Q000201:enzymology* / Q000378:metabolism; D013950:Thymus Gland; D051746:ZAP-70 Protein-Tyrosine Kinase
D018956:CD5 Antigens; D008565:Membrane Proteins; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D011948:Receptors, Antigen, T-Cell; C054979:antigen T cell receptor, zeta chain; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human