title: T cell LFA-1 engagement induces HuR-dependent cytokine mRNA stabilization through a Vav-1, Rac1/2, p38MAPK and MKK3 signaling cascade.
abstract: BACKGROUND
  Engagement of the β2 integrin, lymphocyte function-associated antigen-1 (LFA-1), results in stabilization of T cell mRNA transcripts containing AU-rich elements (AREs) by inducing rapid nuclear-to-cytosolic translocation of the RNA-stabilizing protein, HuR. However, little is known regarding integrin-induced signaling cascades that affect mRNA catabolism. This study examines the role of the GTPases, Rac 1 and Rac 2, and their downstream effectors, in the LFA-1-induced effects on mRNA.
  
  
  RESULTS
  Engagement of LFA-1 to its ligand, ICAM-1, in human peripheral T cells resulted in rapid activation of Rac1 and Rac2. siRNA-mediated knockdown of either Rac1 or Rac2 prevented LFA-1-stimulated stabilization of the labile transcripts encoding IFN-γ and TNF-α, and integrin mediated IFN-γ mRNA stabilization was absent in T cells obtained from Rac2 gene-deleted mice. LFA-1 engagement-induced translocation of HuR and stabilization of TNF- α mRNA was lost in Jurkat cells deficient in the Rac guanine nucleotide exchange factor Vav-1 (J.Vav1). The transfection of J.Vav1 cells with constitutively active Rac1 or Rac2 stabilized a labile β-globin reporter mRNA, in a HuR-dependent manner. Furthermore, LFA-1-mediated mRNA stabilization and HuR translocation in mouse splenic T cells was dependent on the phosphorylation of the mitogen-activated protein kinase kinase, MKK3, and its target MAP kinase p38MAPK, and lost in T cells obtained from MKK3 gene-deleted mice.
  
  
  CONCLUSIONS
  Collectively, these results demonstrate that LFA-1-induced stabilization of ARE-containing mRNAs in T cells is dependent on HuR, and occurs through the Vav-1, Rac1/2, MKK3 and p38MAPK signaling cascade. This pathway constitutes a molecular switch that enhances immune and pro-inflammatory gene expression in T cells undergoing adhesion at sites of activation and effector function.
authors.affiliation: Raymond and Beverly Sackler Foundation Cardiovascular Laboratory, Departments of Medicine (Cardiovascular Medicine) and Immunobiology, Vascular Biology and Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut, United States of America.
authors.forename: Vinod S
authors.initials: VS
authors.lastname: Ramgolam
authors.forename: Scott D
authors.initials: SD
authors.lastname: DeGregorio
authors.forename: Gautham K
authors.initials: GK
authors.lastname: Rao
authors.forename: Mark
authors.initials: M
authors.lastname: Collinge
authors.forename: Sharmila S
authors.initials: SS
authors.lastname: Subaran
authors.forename: Silva
authors.initials: S
authors.lastname: Markovic-Plese
authors.forename: Ruggero
authors.initials: R
authors.lastname: Pardi
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Bender
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000378:metabolism*; D016207:Cytokines / Q000378:metabolism*; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; D020558:GTP Phosphohydrolases / Q000378:metabolism; D006801:Humans; D016023:Integrins / Q000378:metabolism; D007371:Interferon-gamma / Q000378:metabolism; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism*; D048371:MAP Kinase Kinase 3 / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D009479:Neuropeptides / Q000378:metabolism*; D051567:Proto-Oncogene Proteins c-vav / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020744:rac GTP-Binding Proteins / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D000097766:RAC2 GTP-Binding Protein
chemical_list: D000954:Antigens, Surface; D016207:Cytokines; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; D020558:GTP Phosphohydrolases; D016023:Integrins; D007371:Interferon-gamma; D016169:Lymphocyte Function-Associated Antigen-1; D048371:MAP Kinase Kinase 3; D009479:Neuropeptides; D051567:Proto-Oncogene Proteins c-vav; D016601:RNA-Binding Proteins; D014409:Tumor Necrosis Factor-alpha; D048051:p38 Mitogen-Activated Protein Kinases; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein; D000097766:RAC2 GTP-Binding Protein; C098770:ELAVL1 protein, human; C107953:RAC1 protein, human; C484602:Rac1 protein, mouse; C496618:VAV1 protein, human; C496619:Vav1 protein, mouse; C482530:MAP2K3 protein, human; C482531:Map2k3 protein, mouse