Background/Purpose:

T cells from patients with systemic lupus erythematosus (SLE) exhibit defects in signaling and cytokine production, and aberrant numbers and/or function of regulatory T cells (Treg). By discovery approaches we previously identified the serine arginine-rich splicing factor 1 (SRSF1) in human T cells. We showed that SRSF1 promotes normal expression of the CD3 zeta signaling chain, and upregulates IL-2 production in human T cells. SRSF1 expression levels are decreased in SLE T cells, and associate with worse disease. Force expression of SRSF1 into SLE T cells rescued IL-2 production. These results indicate that the SRSF1 deficiency is important in SLE T cell dysfunction. However, it is unknown how SRSF1 deficiency contributes to immune-mediated disease. To this end, we have generated mice with a T cell-restricted deletion of SRSF1, and our goal is to evaluate the mechanistic role of SRSF1 in T cell dysfunction and the development of immune-mediated disease in vivo.

Methods:

Srsf1-conditional knockout (Srsf1-cko) mice were generated by crossing Srsf1-flox mice with d.Lck.Cre mice to delete SRSF1 in mature T cells. Peripheral lymphoid organs were analyzed for immune cell phenotype and function by flow cytometry. T cells were stimulated with anti-CD3, anti-CD28 and PMA plus Ionomycin. Serum and urine were collected at monthly intervals to assess autoantibodies and proteinuria. Tissues (lung, liver, kidney) were fixed and processed for histopathology. Suppressive function of Tregs was assessed in vitro by Treg-Teffector co-culture assays, and in vivo by adoptive transfer of Tregs followed by induction of dextran sodium sulfate (DSS)-induced colitis in B6 mice. Activity of the mammalian target of rapamycin complex (mTORC) 1 pathway was analyzed after T cell stimulation by western blot and phospho-flow cytometry. Phosphatase tensin homolog (PTEN) expression levels were analyzed by qPCR and western blot.

Results:

Srsf1-cko mice develop a systemic autoimmune disease phenotype with elevated autoantibodies and systemic inflammation in peripheral organs including lungs, liver, kidneys and increased proteinuria. Kidney histopathology shows glomerular hyperproliferation, glomerular capillary hyperplasia, and interstitial infiltration of mononuclear cells suggestive of lupus-like nephritis. CD4 T cells exhibit an activated phenotype with increased frequencies of IFN-γ and IL-17 producers but lower amounts of IL-2 upon ex vivostimulation. Tregs from Srsf1-cko mice are dysfunctional in vitro, and are unable to suppress DSS-colitis in vivo. Tregs exhibit an inflammatory phenotype with increased IFN-γ and IL-17 production upon ex vivo stimulation. Increased activity of the mTORC1 pathway is observed in Tregs from the Srsf1-cko mice, and expression levels of PTEN, an inhibitor of the mTORC1 pathway, are decreased.

Conclusion:

SRSF1 is a novel regulator of Treg function, and its deficiency in T cells leads to autoimmunity and lupus-like nephritis. Therefore, deficiency of SRSF1 in T cells may represent a molecular defect that contributes to the pathogenesis of systemic autoimmune disease.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/selective-deficiency-of-serine-arginine-rich-splicing-factor-1-srsf1-in-t-lymphocytes-leads-to-mtorc1-activation-treg-dysfunction-and-systemic-autoimmune-disease/