title: Thymocyte activation induces the association of phosphatidylinositol 3-kinase and pp120 with CD5.
abstract: CD5 is a glycoprotein expressed on thymocytes, T cells, and a subset of B cells. Antibody-mediated cross-linking studies or studies on CD5 knockout mice implicate CD5 as a co-stimulatory or negative regulatory molecule. CD5 is rapidly phosphorylated on tyrosine (Y) residues following Tcell activation. Y429 and Y441 occur in an imperfect immunoreceptor tyrosine-based activation motif (ITAM)-like sequence. We investigated whether phosphatidylinositol (PI) 3-kinase, which binds to tyrosine-phosphorylated ITAM, interacts with CD5 following T cell activation. PI 3-kinase activity and the regulatory p85 subunit of PI 3-kinase associated with CD5 in pervanadate-stimulated, but not in unstimulated thymocytes. Cellular p85 as well as the recombinant Src homology 2 (SH2) domains of p85 bound a tyrosine-phosphorylated peptide encompassing Y463 with approximately threefold greater affinity than a doubly tyrosine-phosphorylated Y429-Y441 peptide. Binding of the C-SH2 domain to the Y463 phosphopeptide, together with preferential binding of the N-SH2 domain to the Y429-Y441 phosphopeptide, suggests a bivalent interaction. A 120-kDa phosphoprotein (pp120) associated with CD5 and specifically with the Y429-Y441 phosphopeptide in stimulated thymocytes. We conclude that stimulation of thymocytes with pervanadate induces the recruitment of PI 3-kinase and pp120 to CD5.
authors.affiliation: Department of Medical Physiology and Biochemistry, University of Stellenbosch Medical School, Tygerberg, South Africa.
authors.forename: K M
authors.initials: KM
authors.lastname: Dennehy
authors.forename: R
authors.initials: R
authors.lastname: Broszeit
authors.forename: D
authors.initials: D
authors.lastname: Garnett
authors.forename: G A
authors.initials: GA
authors.lastname: Durrheim
authors.forename: L L
authors.initials: LL
authors.lastname: Spruyt
authors.forename: A D
authors.initials: AD
authors.lastname: Beyers
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018956:CD5 Antigens / Q000378:metabolism*; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D016384:Consensus Sequence; D003593:Cytoplasm / Q000378:metabolism; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D008213:Lymphocyte Activation; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases; D010748:Phosphopeptides / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D011485:Protein Binding; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction; D013950:Thymus Gland / Q000166:cytology / Q000502:physiology*; D018909:src Homology Domains
chemical_list: D018956:CD5 Antigens; D015815:Cell Adhesion Molecules; D046911:Macromolecular Substances; D010748:Phosphopeptides; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; C496052:Ptk2 protein, rat