title: SARA and Hgs attenuate susceptibility to TGF-beta1-mediated T cell suppression.
abstract: Transforming growth factor-beta1 (TGF-beta1) is a pluripotent cytokine that controls peripheral T cell tolerance mainly in mucosal immunity. It is secreted by regulatory T cells (Tr /Th3) but also by other immununologically active cells. Smad anchor for receptor activation (SARA) and hepatic growth factor-regulated tyrosine kinase substrate (Hgs) are involved in TGF-beta1 signaling. Both molecules are known to present Smad2 and Smad3 to the TGF-beta receptor complex. The role of SARA and Hgs in TGF-beta1 susceptibility of human CD4+ T cells is unclear. We demonstrate here that TGF-beta1 up-regulates SARA mRNA expression in CD4+ T cells similar to that of Smad7. However, the increase in SARA expression was lower (6.1+/-0.3-fold vs. 25+/-4.1-fold) compared with Smad7 and delayed, with a maximum at 12 h compared with 2 h. Th1 and Th2 cell subsets expressed the same levels of SARA and Hgs. Compared with resting cells, significantly lower levels of the two molecules were found in antigen/allergen- or anti-CD3/CD28-stimulated cells. Down-regulation of SARA and Hgs mRNA in preactivated CD4+ T cells was accompanied by a twofold increase in a TGF-beta1 responsive reporter gene assay. Overexpression of SARA and Hgs in T cells yielded a dose-dependent decrease in cotransfected reporter gene expression, indicating an inhibitory function of both molecules. Thus, SARA and Hgs are regulators of TGF-beta1 susceptibility in T cells and integrate regulatory signals into the influence of TGF-beta1-mediated suppression of human T cells.
authors.affiliation: Swiss Institute of Allergy and Asthma Research (SIAF), CH-7270 Davos, Switzerland.
authors.forename: S
authors.initials: S
authors.lastname: Kunzmann
authors.forename: J G
authors.initials: JG
authors.lastname: Wohlfahrt
authors.forename: S
authors.initials: S
authors.lastname: Itoh
authors.forename: H
authors.initials: H
authors.lastname: Asao
authors.forename: M
authors.initials: M
authors.lastname: Komada
authors.forename: C A
authors.initials: CA
authors.lastname: Akdis
authors.forename: K
authors.initials: K
authors.lastname: Blaser
authors.forename: C B
authors.initials: CB
authors.lastname: Schmidt-Weber
mesh_terms: D000485:Allergens / Q000494:pharmacology; D000906:Antibodies / Q000494:pharmacology; D018106:CD28 Antigens / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D056827:Endosomal Sorting Complexes Required for Transport; D005786:Gene Expression Regulation / Q000187:drug effects; D049452:Green Fluorescent Proteins; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D007376:Interleukin-2 / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D019169:Jurkat Cells; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects; D010750:Phosphoproteins / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012697:Serine Endopeptidases; D013601:T-Lymphocytes / Q000187:drug effects* / Q000378:metabolism; D018417:Th1 Cells / Q000187:drug effects / Q000378:metabolism; D018418:Th2 Cells / Q000187:drug effects / Q000378:metabolism; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1
chemical_list: D000485:Allergens; D000906:Antibodies; D018106:CD28 Antigens; D017252:CD3 Complex; D002352:Carrier Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D007376:Interleukin-2; D047908:Intracellular Signaling Peptides and Proteins; D008164:Luminescent Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; C508960:TGFB1 protein, human; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; C096164:hepatocyte growth factor-regulated tyrosine kinase substrate; D049452:Green Fluorescent Proteins; D007371:Interferon-gamma; C116420:ZFYVE16 protein, human; D012697:Serine Endopeptidases