Access to nutrients is critical for an effective T cell immune response to infection. Although transporters for sugars and amino acids have previously been described in the context of the CD8 + T cell immune response, the active transport of exogenous fatty acids has remained enigmatic. In this study, we discovered that the sodium-dependent lysophosphatidylcholine (LPC) transporter major facilitator superfamily domain containing 2A (MFSD2A) is upregulated on activated CD8 + T cells and is required for memory T cell maintenance. MFSD2A deficiency in mice resulted in decreased import of LPC esterified to long chain fatty acids into activated CD8 + T cells, and MFSD2A-deficient cells are at a competitive disadvantage resulting in reduced memory T cell formation and maintenance and reduced response to secondary infection. Mechanistically, import of LPCs was required to maintain T cell homeostatic turnover, which when lost resulted in a decreased memory T cell pool and thus a reduced secondary response to repeat infection.

Adipose regulatory T cells (aTregs) have emerged as critical cells for the control of local and systemic inflammation. In this study, we show a distinctive role for the transcriptional regulator Id2 in the differentiation, survival, and function of aTregs in mice. Id2 was highly expressed in aTregs compared with high Id3 expression in lymphoid regulatory T cells (Tregs). Treg-specific deletion of Id2 resulted in a substantial decrease in aTregs, whereas Tregs in the spleen and lymph nodes were unaffected. Additionally, loss of Id2 resulted in decreased expression of aTreg-associated markers, including ST2, CCR2, KLRG1, and GATA3. Gene expression analysis revealed that Id2 expression was essential for the survival of aTregs, and loss of Id2 increased cell death in aTregs due to increased Fas expression. Id2-mediated aTreg depletion resulted in increased systemic inflammation, increased inflammatory macrophages and CD8 + effector T cells, and loss of glucose tolerance under standard diet conditions. Thus, we reveal an unexpected and novel function for Id2 in mediating differentiation, survival, and function of aTregs that when lost result in increased metabolic perturbation.

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Adipose regulatory T cells (aTregs) have emerged as critical cells for the control of local and systemic inflammation. In this study, we show a distinctive role for the transcriptional regulator Id2 in the differentiation, survival and function of aTregs. Id2 was highly expressed in aTregs compared with high Id3 expression in lymphoid Tregs. Treg-specific deletion of Id2 resulted in a substantial decrease in aTregs, while Tregs in the spleen and lymph nodes were unaffected. Additionally, loss of Id2 resulted in decreased expression of aTreg associated markers including ST2, CCR2, KLRG1 and GATA3. Gene expression analysis revealed that Id2 expression was essential for the survival of aTregs and loss of Id2 increased cell death in aTregs due to increased Fas expression. Id2-mediated aTreg depletion resulted in increased systemic inflammation, increased inflammatory macrophages and CD8 + effector T cells and loss of glucose tolerance under standard diet conditions. Thus, we reveal an unexpected and novel function for Id2 in mediating differentiation, survival and function of adipose-resident Tregs, that when lost resulting in increased metabolic perturbation.3

Objective-Aberrant proliferation of smooth muscle cells (SMC) in response to injury induces pathological vascular remodeling during atherosclerosis and neointima formation. Telomerase is rate limiting for tissue renewal and cell replication; however, the physiological role of telomerase in vascular diseases remains to be determined. The goal of the present study was to determine whether telomerase reverse transcriptase (TERT) affects proliferative vascular remodeling and to define the molecular mechanism by which TERT supports SMC proliferation. Approach and Results-We first demonstrate high levels of TERT expression in replicating SMC of atherosclerotic and neointimal lesions. Using a model of guidewire-induced arterial injury, we demonstrate decreased neointima formation in TERT-deficient mice. Studies in SMC isolated from TERT-deficient and TERT overexpressing mice with normal telomere length established that TERT is necessary and sufficient for cell proliferation. TERT deficiency did not induce a senescent phenotype but resulted in G1 arrest albeit hyperphosphorylation of the retinoblastoma protein. This proliferative arrest was associated with stable silencing of the E2F1-dependent S-phase gene expression program and not reversed by ectopic overexpression of E2F1. Finally, chromatin immunoprecipitation and accessibility assays revealed that TERT is recruited to E2F1 target sites and promotes chromatin accessibility for E2F1 by facilitating the acquisition of permissive histone modifications. cultured cells, TERT is induced in both activated macrophages and proliferating SMC. 14,17 In SMC, the transient increase in TERT abundance in response to growth factor stimulation serves a mitogenic role because inhibition of TERT by oligonucleotide or pharmacological targeting inhibits SMC proliferation. 15,[17][18][19][20] Furthermore, acute telomerase downregulation using TERT antisense RNA decreases proliferation of SMC isolated from genetically hypertensive rats. 21 Although recent genetic experiments established that the mitogenic activity of TERT requires neither telomere extension nor the catalytic activity, 5-8 the molecular mechanisms by which TERT supports cellular proliferation remain elusive. Conclusions-TheseIn this study, we used a genetic model of TERT deficiency to investigate the transcriptional mechanisms underlying the mitogenic activity of TERT during proliferative vascular remodeling. Our studies reveal that TERT deletion prevents neointima formation and SMC proliferation by inducing a silenced chromatin environment at S phase gene promoters. Materials and MethodsMaterials and Methods are available in the online-only Data Supplement. Results TERT Is Expressed in Replicating Neointimal Smooth Muscle CellsTERT protein expression was first analyzed in neointimal SMC of human coronary artery atherosclerotic lesions from hearts explanted during cardiac transplantation. Although TERT expression is considered negligible in normal arteries, 13,14 we confirmed abundant TERT expression in the SMCrich neoint...