Systemic lupus erythematosus serum IgG increases CREM binding to the IL-2 promoter and suppresses IL-2 production through CaMKIV
Yuang-Taung Juang, Ying Wang, Elena E. Solomou, Yansong Li, Christian Mawrin, Klaus Tenbrock, Vasileios C. Kyttaris, George C. Tsokos
Yuang-Taung Juang, Ying Wang, Elena E. Solomou, Yansong Li, Christian Mawrin, Klaus Tenbrock, Vasileios C. Kyttaris, George C. Tsokos
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Article Autoimmunity

Systemic lupus erythematosus serum IgG increases CREM binding to the IL-2 promoter and suppresses IL-2 production through CaMKIV

Abstract

Systemic lupus erythematosus (SLE) T cells express high levels of cAMP response element modulator (CREM) that binds to the IL-2 promoter and represses the transcription of the IL-2 gene. This study was designed to identify pathways that lead to increased binding of CREM to the IL-2 promoter in SLE T cells. Ca2+/calmodulin–dependent kinase IV (CaMKIV) was found to be increased in the nucleus of SLE T cells and to be involved in the overexpression of CREM and its binding to the IL-2 promoter. Treatment of normal T cells with SLE serum resulted in increased expression of CREM protein, increased binding of CREM to the IL-2 promoter, and decreased IL-2 promoter activity and IL-2 production. This process was abolished when a dominant inactive form of CaMKIV was expressed in normal T cells. The effect of SLE serum resided within the IgG fraction and was specifically attributed to anti–TCR/CD3 autoantibodies. This study identifies CaMKIV as being responsible for the increased expression of CREM and the decreased production of IL-2 in SLE T cells and demonstrates that anti–TCR/CD3 antibodies present in SLE sera can account for the increased expression of CREM and the suppression of IL-2 production.

Authors

Yuang-Taung Juang, Ying Wang, Elena E. Solomou, Yansong Li, Christian Mawrin, Klaus Tenbrock, Vasileios C. Kyttaris, George C. Tsokos

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CaMKIV upregulates the expression of CREM and its binding to the –180 si...
CaMKIV upregulates the expression of CREM and its binding to the –180 site of the IL-2 promoter in SLE T cells. (A) Normal T cells were transfected with a CaMKIV expression construct for the indicated time, and the lysates were blotted with an anti-CaMKIV or an anti-hnRNP (control) antibody. (B) SLE T cells were transfected with control plasmid or a plasmid overexpressing CaMKIV and then were treated with PMA and ionomycin. Four hours later, nuclear proteins were purified, and Western blotting was conducted by sequential use of antibodies as indicated. An antibody against hnRNP was used as control. (C) SLE T cells were transfected with control plasmid or a plasmid expressing wild-type CaMKIV and then were treated with PMA and ionomycin. At the indicated time points, cells were harvested, and EMSA was conducted using the oligonucleotide encoding the –180 site of the IL-2 promoter. (D) Cumulative time-curve results of the effect of CaMKIV overexpression in normal and SLE T cells. The y axis represents the ratio of the intensity of the –180/protein complex in the CaMKIV-transfected cells to that in the cells transfected with control plasmid. Normal and SLE T cells were subjected to the experimental protocol detailed in C. Filled symbols, SLE T cells; open symbols, normal T cells. *P < 0.05.