title: CD28-mediated up-regulation of beta 1-integrin adhesion involves phosphatidylinositol 3-kinase.
abstract: Cross-linking of the CD28 Ag on T cells results in increased beta 1-integrin-mediated adhesion to fibronectin. Chimeric contructs containing the CD28 cytoplasmic domain fused to the extracellular and transmembrane regions of CD2 were expressed in HL60 cells to investigate CD28-mediated regulation of adhesion. Ab cross-linking of the CD2/28 chimera resulted in increased beta 1-dependent adhesion of HL60 transfectants to fibronectin. Induced binding was completely inhibited by the phosphatidylinositol 3-kinase (PI 3-K) inhibitor wortmannin. Cross-linking of the CD2/28 chimera also induced association of the p85 subunit of PI 3-K with the CD2/28 cytoplasmic domain. In contrast, cross-linking of a CD2/28 chimera containing a tyrosine to phenylalanine substitution in the YMNM motif did not result in increased adhesion to fibronectin and did not lead to association of the chimera with PI 3-K. These results directly implicate the YMNM motif and PI 3-K in the regulation of beta 1-integrin activity by the CD28 Ag.
authors.affiliation: Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor 48109, USA.
authors.forename: T
authors.initials: T
authors.lastname: Zell
authors.forename: S W
authors.initials: SW
authors.lastname: Hunt
authors.forename: J L
authors.initials: JL
authors.lastname: Mobley
authors.forename: L D
authors.initials: LD
authors.lastname: Finkelstein
authors.forename: Y
authors.initials: Y
authors.lastname: Shimizu
mesh_terms: D000595:Amino Acid Sequence; D000730:Androstadienes / Q000494:pharmacology; D001483:Base Sequence; D018801:CD2 Antigens / Q000235:genetics; D018106:CD28 Antigens / Q000378:metabolism* / Q000494:pharmacology*; D002460:Cell Line; D005353:Fibronectins / Q000378:metabolism; D005822:Genetic Vectors; D006801:Humans; D019012:Integrin beta1 / Q000187:drug effects / Q000378:metabolism*; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000187:drug effects / Q000502:physiology*; D011485:Protein Binding / Q000187:drug effects / Q000276:immunology; D011994:Recombinant Proteins / Q000032:analysis; D014443:Tyrosine / Q000235:genetics / Q000502:physiology; D015854:Up-Regulation / Q000187:drug effects / Q000276:immunology*; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D018801:CD2 Antigens; D018106:CD28 Antigens; D005353:Fibronectins; D019012:Integrin beta1; D011994:Recombinant Proteins; D014443:Tyrosine; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D000077191:Wortmannin