Regulation of CD4+ and CD8+ T cell function by CLNS1A

About This Grant

Project Summary T lymphocytes are critical for many aspects of immunity to infection and cancer, and they play important roles in autoimmune and allergic diseases where they promote inflammation and help B cells produce antibodies. Given the importance of both CD4+ and CD8+ T cells for many aspects of immune responses in health and disease, it is essential to understand the mechanisms that control their function both from a basic science and translational perspective. T cell function depends on ion channels in the cell membrane which transport charged ions such as calcium in and out of cells. While several ion channel types are known to be required for T cell function, only a small fraction of the hundreds of ion channels and related proteins have been studied in T cells. To address this knowledge gap and to identify potential new drug targets we conducted two forward genetics screens for ion channels in CD4+ T cells using animal models of brain and intestinal inflammation. We identified a putative channel protein called CLNS1A, whose deletion prevents the expansion of antigen-specific CD4+ T cells in mice and thus, their ability to induce inflammation. We had included CLNS1A in our screens because it was initially reported to be a chloride channel or a regulator of such channels. We did not, however, find evidence that CLNS1A affects chloride channel function in CD4+ T cells. Neither does it seem to regulate spliceosome maturation and thus, the splicing of pre-mRNA into mature messenger RNAs in T cells. Instead, our data show that CLNS1A controls DNA repair in activated and rapidly expanding T cells. Moreover, CLNS1A regulates several cell cycle checkpoints, thus allowing T cells to proliferate. CLNS1A controls these functions in CD4+ T cells by regulating the expression of hundreds of genes which are involved in cell cycle regulation and DNA repair. The function of CLNS1A is dependent on the enzyme PRMT5, a protein methyltransferase. Both CLNS1A and PRMT5 bind to the promoters of many genes, thereby regulating their expression. The goals of this proposal are to 1) investigate the effects of CLNS1A on DNA repair and cell cycle regulation in CD4+ and CD8+ T cells, 2) elucidate the molecular mechanisms by which CLNS1A regulates gene expression in T cells that includes the identification of additional CLNS1A binding proteins besides PRMT5, and 3) determine the role of CLNS1A in CD4+ and CD8+ T cell-mediated immune responses to infection and inflammation. Our study will shed new light on the hitherto unknown role of CLNS1A in T cells, determine the molecular mechanisms underlying CLNS1A function and reveal the involvement of CLNS1A in T cell mediated immune responses in health and disease.