title: Biochemical identification of a direct physical interaction between the CD4:p56lck and Ti(TcR)/CD3 complexes.
abstract: The CD4 and CD8 antigens function in synergy with the TcR/CD3 complex in the generation of intracellular signals leading to T cell proliferation. The association of the protein-tyrosine kinase p56lck with CD4 and CD8 provides a potential mechanism in the generation of intracellular signals. Several studies have shown that CD4 can co-modulate with TcR/CD3 suggesting that these receptor complexes may associated on the surface of the T cell. Nevertheless, it has proven difficult to formally demonstrate a direct physical interaction between the CD4 and TcR/CD3 complexes using biochemical techniques. In this study, we have used the sensitivity of the in vitro kinase assay to show a direct physical linkage between the CD4:p56lck complex and various CD3 subunits. Immunoprecipitation of CD4 from cell lysates derived from the T lymphoblastoid line HPB-ALL results in the co-purification of p56lck with an additional polypeptide at 20 kDa. Re-precipitation analysis and isoelectric focusing demonstrated that this band corresponds to the CD3 epsilon chain. An alternative approach which involves the labeling of microsomal membranes with [gamma-32P]ATP revealed the presence of CD3 epsilon and zeta chains in anti-CD4 immunoprecipitates. By contrast, we were unable to demonstrate the association of the CD4:p56lck and TcR/CD3 complex in resting peripheral blood lymphocytes. These data indicate that the CD4:p56lck and TcR/CD3 complexes have the ability to form stable complexes on the surface of certain T cell lines.
authors.affiliation: Divisions of Tumor Immunology, Dana-Farber Cancer Institute, Boston, MA 02115.
authors.forename: K E
authors.initials: KE
authors.lastname: Burgess
authors.forename: A D
authors.initials: AD
authors.lastname: Odysseos
authors.forename: C
authors.initials: C
authors.lastname: Zalvan
authors.forename: B J
authors.initials: BJ
authors.lastname: Druker
authors.forename: P
authors.initials: P
authors.lastname: Anderson
authors.forename: S F
authors.initials: SF
authors.lastname: Schlossman
authors.forename: C E
authors.initials: CE
authors.lastname: Rudd
mesh_terms: D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis*; D017252:CD3 Complex; D015704:CD4 Antigens / Q000032:analysis* / Q000502:physiology; D008213:Lymphocyte Activation; D051379:Mice; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000032:analysis*; D011948:Receptors, Antigen, T-Cell / Q000032:analysis*
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D015704:CD4 Antigens; D011948:Receptors, Antigen, T-Cell; D011505:Protein-Tyrosine Kinases