title: Structural requirements for beta1 integrin-mediated tyrosine phosphorylation in human T cells.
abstract: The beta1 integrin adhesion receptors activate signal transduction pathways that induce tyrosine phosphorylation of a variety of substrates. Increased tyrosine phosphorylation is mediated by the beta1 subunit cytoplasmic domain, which consists of 46 amino acids and contains no intrinsic kinase activity. In the H9 T cell line, beta1 integrin engagement leads to the increased tyrosine phosphorylation of three 105 to 115-kDa substrates that are distinct from focal adhesion kinase (FAK): HEF1 (human enhancer of filamentation 1), a protein with structural homology to p130Cas, and two novel substrates, pp105 and pp115. DNA-mediated gene transfer was used to explore the role of the beta1 cytoplasmic domain in integrin-mediated tyrosine phosphorylation of HEF1, pp105, and pp115 in human T cells. Using a chimeric receptor composed of the cytoplasmic domain of the beta1 integrin subunit and the extracellular and transmembrane domains of the CD2 Ag, we demonstrate that the beta1 cytoplasmic domain is necessary and sufficient for inducing tyrosine phosphorylation of each of these three substrates in H9 T cells. Analysis of a series of beta1 cytoplasmic domain truncations reveals that a truncation of only five amino acids from the carboxyl-terminal end of the beta1 cytoplasmic domain abrogates the ability of the CD2/beta1 chimera to activate tyrosine phosphorylation of HEF1, pp105, or pp115. Thus, the carboxyl-terminal five amino acids, Lys-Tyr-Glu-Gly-Lys (KYEGK), of the beta1 integrin cytoplasmic domain are critical for the coordinate tyrosine phosphorylation of three non-FAK substrates in human T cells.
authors.affiliation: Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor 48109, USA.
authors.forename: L D
authors.initials: LD
authors.lastname: Finkelstein
authors.forename: P J
authors.initials: PJ
authors.lastname: Reynolds
authors.forename: S W
authors.initials: SW
authors.lastname: Hunt
authors.forename: Y
authors.initials: Y
authors.lastname: Shimizu
mesh_terms: D000595:Amino Acid Sequence; D018801:CD2 Antigens / Q000235:genetics; D002460:Cell Line; D003593:Cytoplasm / Q000737:chemistry; D006801:Humans; D019012:Integrin beta1 / Q000235:genetics / Q000494:pharmacology*; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D050737:Proto-Oncogene Proteins c-crk; D011994:Recombinant Proteins; D015682:Retroviridae Proteins, Oncogenic / Q000378:metabolism; D013601:T-Lymphocytes / Q000737:chemistry / Q000378:metabolism*; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism
chemical_list: D018801:CD2 Antigens; D019012:Integrin beta1; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D050737:Proto-Oncogene Proteins c-crk; D011994:Recombinant Proteins; D015682:Retroviridae Proteins, Oncogenic; C037459:phosphoprotein pp105; D014443:Tyrosine; D011494:Protein Kinases