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A3.20 TNF Regulates CD3ζ Expression of T Lymphocytes Via SRC-Like Adaptor Protein-Dependent Proteasomal Degradation
  1. Barbara Érsek1,
  2. Viktor Molnár1,
  3. Andrea Balogh2,
  4. János Matkó2,
  5. Andrew P Cope3,
  6. Edit I Buzás1,
  7. András Falus1,
  8. György Nagy1,4
  1. 1Department of Genetics, Cell, and Immunobiology, Faculty of Medicine, Semmelweis University, 1089 Budapest, Hungary
  2. 2Department of Immunology, Eötvös Loránd University, 1117 Budapest, Hungary
  3. 3Division of Immunology, Infection and Inflammatory Disease, Academic Department of Rheumatology, Center for Molecular and Cellular Biology of Inflammation, King’s College School of Medicine, King’s College London, London WC2R 2LS, UK
  4. 4Department of Rheumatology, Semmelweis University, Medical School, 1023 Budapest, Hungary

Abstract

Background and Objectives although ζ-chain downregulation of human T lymhocytes is common at sites of chronic inflammation, the precise mechanism of ζ-chain regulation is not known. Src-like adaptor protein (SLAP) is a regulator of T cell activation; earlier data have reported that SLAP regulates immunoreceptor signalling. We studied the mechanism of CD3 ζ-chain downregulation.

Materials and Methods CD3ζ and SLAP protein levels of T lymphocytes were measured by Western blot. Jurkat cells were transiently transfected with siRNAs to silence SLAP, knockdown efficiency of the siRNAs was measured by real-time RT-PCR and by Western blot. For confocal microscopy experiments cells were transfected with eGFP-SLAP cDNA vector or control eGFP vector. The colocalisation between CD3ζ and SLAP were measured by laser confocal microscopy. CD3ζ mRNA was measured by quantitative real-time RT-PCR, IL-2 level was measured by ELISA.

Results in vitro TNF treatment of human T cells selectively, dose dependently and reversibly downregulates CD3 ζ-chain expression and inhibits activation-induced IL-2 expression (p < 0.01). Inhibition of the proteasome prevented the effect of TNF on CD3 ζ-chain expression. The colocalization of SLAP with CD3 ζ-chain and the SLAP expression were enhanced by TNF treatment (p < 0.01 and p < 0.05, respectively). SLAP silencing with small interfering RNA inhibited the TNF-induced ζ-chain downregulation. SLAP levels of the CD4 T cells, isolated from patients with rheumatoid arthritis were higher than that of the healthy donors’ (p < 0.05). In addition, in vitro TNF treatment did not alter the SLAP expression of the CD4 lymphocytes of anti-TNF therapy-treated RA patients.

Conclusions our present data suggest that TNF regulates T cell activation during inflammatory processes, by altering CD3 ζ-chain expression via a SLAP-dependent mechanism. Thereafter SLAP-dependent regulation of CD3 ζ-chain may have an important role in the fine control of TCR signalling during chronic inflammation. SLAP may have a role in the pathomechanism of RA.

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