Project description:Regulatory T cells (Tregs) maintain immune homeostasis and prevent autoimmunity. Serine can stimulate glutathione (GSH) synthesis and feeds into the one-carbon metabolic cycle essential for effector T cell (Teff) responses. However, serine’s functions, linkage to GSH, and role in stress responses in Tregs are unknown. Here we show, using mice with Treg-specific ablation of the catalytic subunit of glutamate cysteine ligase (Gclc), that GSH loss in Tregs alters serine import and synthesis, and that the integrity of this feedback loop is critical for Treg suppressive capacity. Although Gclc-ablation does not impair Treg differentiation, the mutant mice develop severe spontaneous autoimmunity and show enhanced anti-tumor responses. Gclc-deficient Tregs exhibit increased serine metabolism, mTOR activation and proliferation but FoxP3 was downregulated. Limitation of cellular serine in vitro and in vivo restores FoxP3 expression and suppressive capacity to Gclc-deficient Tregs. Our work reveals an unexpected role for GSH in restricting serine availability to preserve Treg functionality.
Project description:Serine is a substrate for nucleotides, NADPH and glutathione (GSH) synthesis. Previous studies in cancer cells and lymphocytes have shown that serine-dependent one-carbon units are necessary for nucleotide production to support proliferation. Presently, it is unknown whether serine metabolism impacts the function of non-proliferative cells, such as inflammatory macrophages. We find that in macrophages, serine is required for optimal lipopolysaccharide (LPS) induction of IL-1β mRNA expression, but not inflammasome activation. The mechanism involves a requirement for glycine, which is made from serine, to support macrophage glutathione (GSH) synthesis. Cell-permeable GSH, but not the one-carbon donor formate, rescues IL-1β mRNA expression. Pharmacological inhibition of de novo serine synthesis in vivo decreased LPS induction of IL-1β levels and improved survival in an LPS-driven model of sepsis in mice. Our study reveals that serine metabolism is necessary for GSH synthesis to support IL-1β cytokine production.
Project description:High-risk B-cell acute lymphoblastic leukemia (B-ALL) remains a therapeutic challenge despite advances in the use of tyrosine kinase inhibitors and chimeric- antigen-receptor engineered T cells. Lymphoblastic-leukemia precursors are highly sensitive to oxidative stress. KLF5 is a member of the Krüppel-like family of transcription factors. KLF5 expression is repressed in B-ALL, including BCR-ABL1+ B-ALL. Here, we demonstrate that forced expression of KLF5 in B-ALL cells bypasses imatinib resistance not associated with mutations of BCR-ABL. Expression of Klf5 impaired leukemogenic activity of BCR-ABL1+ B-cell precursors in vitro and in vivo. The complete genetic loss of Klf5 reduced oxidative stress, increased regeneration of reduced glutathione and decreased apoptosis of leukemic precursors. Klf5 regulation of glutathione levels was mediated by its regulation of glutathione-S-transferase Mu 1 (Gstm1), an important regulator of glutathione-mediated detoxification and protein glutathionylation. Expression of Klf5 or the direct Klf5 target gene Gstm1 inhibited clonogenic activity of Klf5∆/∆ leukemic B-cell precursors and unveiled a Klf5-dependent regulatory loop on glutamine-dependent glutathione metabolism. In summary, we describe a novel mechanism of Klf5 B-ALL suppressor activity through its direct role on the metabolism of antioxidant glutathione levels, a crucial positive regulator of leukemic precursor survival.
Project description:Argininosuccinate lyase (ASL) is a key enzyme integral to the hepatic urea cycle which is required for ammonia detoxification, and the citrulline-nitric oxide (NO) cycle for NO production. ASL deficient patients present with argininosuccinic aciduria (ASA), an inherited metabolic disease with hyperammonaemia and a chronic systemic phenotype with neurocognitive impairment and chronic liver disease. ASL deficiency as an inherited model of systemic NO deficiency, shows enhanced nitrosative and oxidative stress. Here, we describe the dysregulation of glutathione biosynthesis and upstream cysteine utilization in ASL-deficient patients and mice using targeted metabolomics and in vivo positron emission tomography (PET) imaging using (S)-4-(3-18F-fluoropropyl)-L-glutamate ([18F]FSPG). Upregulation of cysteine metabolism contrasted with glutathione depletion and down-regulated antioxidant pathways. hASL mRNA encapsulated in lipid nanoparticles corrected and rescued the neonatal and adult Asl-deficient mouse phenotypes, respectively, enhancing ureagenesis and glutathione metabolism and ameliorating chronic liver disease. We further present [18F]FSPG PET as a novel non-invasive diagnostic tool to assess liver disease and therapeutic efficacy in ASA. These findings support clinical translation of mRNA therapy for ASA.
Project description:Serine is a non-essential amino acid that is generated by the sequential actions of phosphoglycerate dehydrogenase (PHGDH), phosphoserine aminotransferase (PSAT1) and phosphoserine phosphatase (PSPH). Increased serine biosynthesis occurs in several cancers and supports tumor growth. In addition to serine synthesis, exogenous serine is taken up by cells and can also fuel tumor growth. Interestingly, colon cancer cells increase expression of serine biosynthesis enzymes in the absence of exogenous serine, suggesting a compensatory adaptive response to reduced availability of serine. This study explored the relative contributions of exogenous and synthesized serine to colon cancer cell growth, metabolism and response to anti-cancer therapy.
Project description:Here, gene profiles in rat spermatogonial stem cell lines are compared to publicly available mouse, monkey and human spermatogonial gene profiles. Interestingly, rat spermatogonia expressed metabolic control factors Foxa1, Foxa2 and Foxa3. Germline Foxa2 was enriched in Gfra1Hi and Gfra1Low undifferentiated A-single spermatogonia. Foxa2-bound loci in spermatogonial chromatin were over-represented by conserved stemness genes (Dusp6, Gfra1, Etv5, Rest, Nanos2, Foxp1) that intersect bioinformatically with conserved glutathione/pentose phosphate metabolism genes (Tkt, Gss, Gclc, Gclm, Gpx1, Gpx4, Fth), marking elevated spermatogonial GSH:GSSG. Cystine-uptake and intracellular conversion to cysteine typically couple glutathione biosynthesis to pentose phosphate metabolism. Rat spermatogonia, curiously, displayed poor germline stem cell viability in cystine-containing media, and, like primate spermatogonia, exhibited reduced transsulfuration pathway markers. Exogenous cysteine, cysteine-like mercaptans, somatic testis cells and ferroptosis inhibitors counteracted the cysteine starvation-induced spermatogonial death and stimulated spermatogonial growth factor activity in vitro.