title: Resting lymphocyte kinase (Rlk/Txk) phosphorylates the YVKM motif and regulates PI 3-kinase binding to T-cell antigen CTLA-4.
abstract: CTLA-4 and CD28 are differentially expressed on T-cells. They bind to a common ligand B71/2 (CD80/86), however with different avidities. Unlike CD28 which augments the T-cell response, CTLA-4 operates predominately as a negative regulator of T-cell proliferation. The mechanism by which CTLA-4 can generate these intracellular signals is unclear. Little is known regarding the identity of the protein-tyrosine kinase(s) responsible for CTLA-4 phosphorylation and thus creating conditions for the reported binding to PI 3-kinase and the protein tyrosine phosphatase SHP-2. In this study, we demonstrate that Rlk (resting lymphocyte kinase) is capable of phosphorylating CTLA-4 at the YVKM motif. Consistent with this finding, Rlk is capable of providing conditions for the binding of the SH2 domains of PI 3-kinase to the receptor. CTLA-4 is therefore the first known substrate for Rlk suggesting the possibility that this kinase may participate in CTLA-4 function.
authors.affiliation: Department of Cancer Immunology and AIDS, Harvard Medical School, Boston, Massachusetts, 02115, USA.
authors.forename: H
authors.initials: H
authors.lastname: Schneider
authors.forename: P L
authors.initials: PL
authors.lastname: Schwartzberg
authors.forename: C E
authors.initials: CE
authors.lastname: Rudd
mesh_terms: D000069594:Abatacept; D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019556:COS Cells; D060908:CTLA-4 Antigen; D006706:Homeostasis; D006801:Humans; D018796:Immunoconjugates; D047908:Intracellular Signaling Peptides and Proteins; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity; D014162:Transfection
chemical_list: D015703:Antigens, CD; D000943:Antigens, Differentiation; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; D018796:Immunoconjugates; D047908:Intracellular Signaling Peptides and Proteins; D011993:Recombinant Fusion Proteins; D000069594:Abatacept; D019869:Phosphatidylinositol 3-Kinases; C089848:Tec protein-tyrosine kinase; D011505:Protein-Tyrosine Kinases; C516724:PTPN11 protein, human; C509249:PTPN6 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases