Graduate Student Vanderbilt University, United States
Background: Many inflammatory diseases and cancer can be driven by dysregulation of T helper cells (Th cells). We have previously shown that manipulation of metabolic pathways can affect Th cell differentiation and disease development.
Methods: In this study, we developed a custom CRISPR library to investigate the role of lipid metabolism in survival and proliferation of Th cells. In pooled genetic screens using in vivo models of allergic airway disease, inflammatory bowel disease, and adoptive cell transfer therapy tumor model, CD4+ of CD8+ T cells were transduced with a lipid metabolism library and adoptively transferred into Rag1 -/- mice. After disease development, the relative abundance of each guide RNA was determined in lung-infiltrating CD4+ T cells to identify immunometabolic regulators of CD4+ T cell recruitment and persistence in inflammation.
Results: Mitochondrial trans-2-enoyl-coenzyme A reductase (Mecr) was a significantly depleted gene, demonstrating a potential role in T cell-mediated inflammation. Therefore, further studies used CRISPR/Cas9 to test the role of Mecr in T cell function. Mecr-knockout in vitro caused no significant changes in cytokine production or transcription factor expression. When tested in a side-by-side Th17-transfer inflammatory bowel disease model, the proportion of Mecr-knockout cells was decreased compared to a non-targeting control in the spleens, mesenteric lymph nodes, and lamina propria in addition to lower IFNg and Tbet expression. In our CD8+ adoptive cell transfer therapy model using the side-by-side control and Mecr-knockout, the Mecr-knockout cells were also significantly reduced in the tumor. High MECR expression has also been correlated with worse survival outcomes in RCC patients. Using immunohistochemistry of syngeneic orthotopic mouse Renca tumors, Mecr expression was significantly reduced in tumor compared to normal kidney.
Conclusions: Together, these results show that Mecr plays an important role in T cell immunometabolism further studies are focused on elucidating its role in inflammatory diseases in different T cell subsets.
