Glycoprotein A repetitions predominant, a Treg-specific molecule, in autoimmune inflammation

点击翻译按钮获取中文摘要

Rheumatoid arthritis (RA) is a chronic systemic inflammatoryautoimmune disease, which is characterized by an incompetent function of regulatory T cells (Tregs) and, subsequently, an uncontrolled expansion of effector T cells. To facilitate detailed analyses of the molecular mechanisms resulting in impaired Treg function in RA, we have previously performed a gene chip analysis of Tregs and have identified glycoprotein A repetitions predominant (GARP) as a new and specific Treg surface molecule. Functional analysis of GARP has revealed a role of GARP in Treg function in that reduced expression of GARP is associated with impaired Treg function. Of pathophysiological interest for autoimmune diseases, GARP expression is diminished in RA. This observation in combination with the recent evidence of a pro-inflammatory rather than anti-inflammatory phenotype of Tregs in RA strongly suggests a potential importance of GARP and its altered expression in the pathogenesis of autoimmune rheumatic inflammation. It is therefore of great interest to investigate in detail the role of GARP in Tregs and the molecular mechanisms that result in diminished GARP expression in Tregs in RA. In the project proposed here we will explore in detail the role of GARP in Tregs by employing various methods to interfere with GARP expression in Tregs as well as to enforce GARP expression in effector T cells and functionally assess Treg function such as proliferation, cytokine secretion, or blocking effector T cell activation. Furthermore, we will define the role of GARP in stabilizing the Treg phenotype by performing redifferentiation experiments with distinct CD4 T cell populations (e.g. Th1, Th2, and Th17 cells as well as Tregs). As GARP is tightly controlled by posttranscriptional regulation through miRNAs we plan to perform deep sequencing analysis of the 3UTR of GARP in patients and controls to gain insight into potential mechanisms of GARP regulation in RA. The analyses will be completed by assessing GARP expression in clinically well-defined patients with distinct autoimmune diseases and by determining the level of different miRNAs in Tregs from the patients. Finally, we will assess whether SNPs in the 3´UTR of GARP will contribute to a different expression level of GARP in patients by altering the affinity of miRNAs for their target sequence on the GARP 3`UTR or by introducing novel miRNA binding sites into the GARP 3`UTR. Together, the experiments are desiged to gain detailed insight into the role of GARP in Tregs, ist mechanisms of regulation and its contribution to human autoimmune diseases.