CD3ζ-chain expression of human T lymphocytes is regulated by TNF via Src-like adaptor protein-dependent proteasomal degradation.
Decreased expression of the TCR ζ-chain has been reported in several autoimmune, inflammatory, and malignant diseases, suggesting that ζ-chain downregulation is common at sites of chronic inflammation. Although ζ-chain is critically important in T lymphocyte activation, the mechanism of the decreased ζ-chain expression is less clear. Src-like adaptor protein (SLAP) is a master regulator of T cell activation; previous data have reported that SLAP regulates immunoreceptor signaling. We have examined the mechanism and the functional consequences of CD3 ζ-chain downregulation. TNF treatment of human T lymphocytes (15-40 ng/ml) selectively downregulates CD3 ζ-chain expression in a dose-dependent manner (p < 0.05) and decreases activation-induced IL-2 expression (p < 0.01). Although blocking of the lysosomal compartment fails to restore TNF-induced CD3 ζ-chain downregulation, inhibition of the proteasome prevented the effect of TNF. Both SLAP expression and the colocalization of SLAP with CD3 ζ-chain was enhanced by TNF treatment (p < 0.05 and p < 0.01, respectively), whereas TNF-induced ζ-chain downregulation was inhibited by gene silencing of SLAP with small interfering RNA. SLAP levels of the CD4(+) T lymphocytes isolated from patients with rheumatoid arthritis were more than 2-fold higher than that of the healthy donors' (p < 0.05); moreover, TNF treatment did not alter the SLAP expression of the CD4(+) cells of anti-TNF therapy-treated patients. Our present data suggest that TNF modulates T cell activation during inflammatory processes by regulating the amount of CD3 ζ-chain expression via a SLAP-dependent mechanism. These data provide evidence for SLAP-dependent regulation of CD3 ζ-chain in the fine control of TCR signaling.
Department of Genetics, Cell, and Immunobiology, Faculty of Medicine, Semmelweis University, 1089 Budapest, Hungary.
Barbara
B
Érsek
Viktor
V
Molnár
Andrea
A
Balogh
János
J
Matkó
Andrew P
AP
Cope
Edit I
EI
Buzás
András
A
Falus
György
G
Nagy
D048868:Adaptor Proteins, Signal Transducing / Q000276:immunology* / Q000378:metabolism; D001172:Arthritis, Rheumatoid / Q000276:immunology / Q000378:metabolism; D015153:Blotting, Western; D017252:CD3 Complex / Q000096:biosynthesis* / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000276:immunology; D006801:Humans; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000276:immunology*; D018613:Microscopy, Confocal; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000276:immunology* / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D011948:Receptors, Antigen, T-Cell / Q000276:immunology / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology* / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D017252:CD3 Complex; C121704:CD3 antigen, zeta chain; D011948:Receptors, Antigen, T-Cell; C490635:SLA protein, human; D014409:Tumor Necrosis Factor-alpha; D016392:Proto-Oncogene Proteins pp60(c-src); D046988:Proteasome Endopeptidase Complex