Biology subjects

Snyder, N. W.

Publications and source records attributed to Snyder, N. W..

At least 19 recordsLinked to original sources

bioRxiv2026

Disconnect Between Succinate, Succinyl-CoA, and Histone Succinylation in Cells and Gastrointestinal Stromal Tumors with Succinate Dehydrogenase Deficiency

Background: Succinate dehydrogenase (SDH) is a heterotetrameric enzyme in both the tricarboxylic acid (TCA) cycle and the electron transport chain. SDH-deficiency has been shown to drive the oncogenesis of cancer types including gastrointestinal stromal tumors (GIST), paraganglioma/pheochromocytoma, and clear cell renal cell carcinoma. Previous work on SDH loss has shown increases in succinate, decreases in fumarate, as well as increase in the succinate to -ketoglutarate ratio, and correlated these changes to metabolite signaling and epigenetic dysregulation. Alterations to other TCA intermediates, including succinyl-CoA, the acyl-donor for succinylation, and the resulting cellular effects has not been fully explored. Methods: We used liquid chromatography high resolution mass spectrometry to quantify TCA cycle metabolites across the NCI-60 panel of cell lines, three SDH-competent and SDH-deficient model systems, and human tumor samples. We measured histone post-translational modifications in SHD-deficient and SDH-competent models and examined the correlation and potential pharmacological targeting of described desuccinylase enzymes by protein and cell assays. Results: We found an increase in succinyl-CoA in multiple SDH-deficient models, but no correlation between succinate to fumarate ratio and succinyl-CoA concentrations in the NCI-60. Interestingly, we found that while there was an increase in succinyl-CoA in the SDH-deficient cells, there was no corresponding increase in histone succinylation. We also observed a decrease in lysine malonylation and glutarylation, two other anionic lysine modifications. Cell viability and clonogenic assays revealed very weak or no selective effect of desuccinylase targeting in SDH-deficient models. Similarly, using SDH-deficient versus SDH-competent GIST patient samples, we examined both protein expression and metabolite abundance at the bulk tumor level and found no significant increase in succinyl-CoA or desuccinylase expression, despite the increase in succinate to fumarate ratio. Conclusions: We found that SDH-deficiency led to altered central carbon metabolism including increases to succinate and succinyl-CoA. Despite data that suggested the upregulation of desuccinylases may mediate a disconnect between succinyl-CoA concentration and histone succinylation, we found weak or no reductions in cell viability in response to pharmacological inhibition of desuccinylases. Additionally, no correlation of SDH loss with desuccinylase expression and succinyl-CoA in bulk tumor samples was observed.

cancer biology↗

bioRxiv2026

Nutrient-sensitive histone propionylation regulates T cell fate and function

Tissue microenvironments differ widely in nutrient composition; yet how local nutrient conditions shape epigenetic programs that direct immune cell fate is poorly understood. We identify histone lysine propionylation (Kpr) as a chromatin mechanism linking nutrient availability to T cell fate decisions. Proteomic analysis reveals that Kpr is broadly reduced in exhausted T cells. H3K18pr is enriched at stemness-associated loci in effector T cells and depleted upon exhaustion. Isoleucine and propionate supply propionyl-CoA in T cells, and restricted nutrient availability within the tumor microenvironment limits histone Kpr, promoting T cell exhaustion. Disrupting isoleucine catabolism in T cells further suppresses Kpr, without altering histone acetylation, and impairs T cell function and antitumor immunity in a manner rescued by propionate. Dietary supplementation of isoleucine and propionate increases Kpr in tumor infiltrating lymphocytes, limits exhaustion, and improves tumor control. These findings establish a microenvironment-chromatin axis crucial for antitumor immunity and amenable to nutritional intervention.

immunology↗

bioRxiv2026

Female-specific m6A remodeling in the liver correlates with post-transcriptional metabolic adaptation to high fat diet

Sex differences strongly influence susceptibility to metabolic dysfunction-associated steatotic liver disease (MASLD), yet the regulatory mechanisms underlying these differences remain incompletely understood. To examine sex-specific hepatic adaptation to a high-fat (HF) diet mouse model of MASLD, we integrated proteomics, transcriptomics, and Oxford Nanopore direct RNA sequencing for transcriptome-wide m6A profiling in male and female mouse livers. Female mice were relatively protected from HF diet-induced hepatic steatosis and exhibited distinct proteome remodeling enriched for peroxisomal pathways. In contrast, transcriptomic responses in females were dominated by inflammatory signatures and did not recapitulate the metabolic adaptations observed at the protein level, revealing extensive RNA-protein discordance and post-transcriptional remodeling. Integrated RNA-protein analyses identified female-specific amplification of peroxisomal proteins despite modest transcript-level changes. HF diet also induced sex-specific remodeling of m6A RNA methylation and altered regulation of the m6A methylation system. Notably, reduced 3' UTR m6A methylation of peroxisomal transcripts inversely correlated with increased protein abundance relative to RNA expression in female mice. Together, these findings implicate m6A-associated post-transcriptional regulation in sex-specific hepatic adaptation to HF diet exposure and the basis for discordance between many of the mRNAs and proteins in the liver.

systems biology↗

bioRxiv2026

Histone succinylation directly inhibits Jumonji domain demethylases and stabilizes repressive chromatin states

Herein we uncover a relationship between histone succinylation and Jumonji (JmjC) domain-containing histone demethylases. We used quantitative proteomics and peptide pull-down assays to identify JmjC demethylases as candidate interactors with succinylated histone peptides. Succinyl-lysine peptides bind and inhibit the catalytic activity of JmjC demethylases in a dose-dependent manner. This includes KDM4D and KDM6B, which are responsible for the removal of the silencing marks H3K9me2/3 and H3K27me2/3. Supraphysiological sodium succinate treatment of HepG2/C3A cells increased the relative abundance of histone succinylation, H3K9me2/3, and H3K27me2/3. CUT&Tag and ChIP-mass spectrometry revealed the co-occurrence of succinylation with these repressive methylation marks, in addition to reduced transcriptional output. This work establishes a novel mechanistic link between metabolite abundance and chromatin regulation and suggests a role for histone succinylation in the maintenance of heterochromatin.

biochemistry↗

bioRxiv2026

Mitochondrial copper stabilizes lipoylated TCA cycle proteins to sustain metabolism and proliferation

Copper (Cu) is an essential cofactor for mitochondrial cytochrome c oxidase, yet whether it directly regulates mitochondrial metabolism beyond respiration remains unclear. Here we show that mitochondrial Cu, delivered by SLC25A3, is required to maintain the stability of lipoylated TCA cycle proteins. Loss of Slc25a3 or pharmacological Cu depletion selectively destabilized the lipoylated E2 subunits of mitochondrial dehydrogenases and the lipoylation enzymes LIPT1 and LIPT2, an effect not reproduced by acute electron transport chain inhibition. Mechanistically, we find that Cu directly engages the reduced lipoyl moiety using chemical probes and synthetic peptide approaches. Cu depletion impaired PDH and OGDH activity, rewired TCA cycle metabolism, and imposed a dependence on pyruvate carboxylase for anaplerosis. This metabolic defect depleted aspartate, suppressed mTORC1 signaling, and limited proliferation. Conversely, selective delivery of Cu to the mitochondria restored lipoylation, TCA cycle function, and cell growth. Together, these findings identify mitochondrial Cu as a structural regulator of the lipoylation machinery and reveal a direct link between Cu homeostasis and central carbon metabolism.

cell biology↗

bioRxiv2026

Metabolic control of smooth muscle cell phenotype switching in atherosclerosis

The loss of smooth muscle cell (SMC) contractile phenotype contributes to various diseases including atherosclerosis. However, its metabolic basis is not entirely elucidated. Since the transforming growth factor beta (TGF{beta}) signaling is among principal regulators of SMC contractility, we studied metabolic regulation of TGF{beta} signaling in SMCs in vitro and atherosclerotic mouse models and human lesions. We found that TGF{beta} induced Ac-CoA synthetase 2 (ACSS2)-dependent Ac-CoA production, by suppressing pyruvate dehydrogenase kinase 4 (PDK4). This stabilized R-SMADs and TGF{beta} receptor 1, preserving SMC contractile phenotype. SMC-specific PDK4 knockout mimicked the effect of TGF{beta} signaling both metabolically and phenotypically, increasing glucose-derived synthesis of Ac-CoA and SMC contractile phenotype. SMC-specific Pdk4 knockout in ApoE knockout mice reduced atherosclerosis. Furthermore, human specimens demonstrated a strong correlation between PDK4 level and atherosclerosis severity. These findings indicate that continuous TGF{beta} signaling, critical to the maintenance of the normal SMC contractile state and is regulated by PDK4 and carbohydrate metabolism. TeaserReducing PDK4 metabolically restricts aortic plaque growth via TGF{beta}-dependent SMC contractility.

cell biology↗

bioRxiv2026

A liquid chromatography-mass spectrometry method to quantify total Coenzyme A concentration and isotopic labeling

Coenzyme A is an essential cofactor synthesized from pantothenate, cysteine, and ATP, and is involved in numerous processes of cellular metabolism through its ability to carry activated acyl groups. Coenzyme A participates in catabolism of carbohydrate, fat and amino acids; biosynthesis of fatty acids, cholesterol and heme; and protein modification including acetylation and 4-phosphopantetheinylation. Despite CoAs critical functions, the regulation of CoA levels and the rate of CoA synthesis in different cell types and disease states are not well understood. One reason for this gap is that many acyl-CoA species are analytically challenging to measure due to factors including instability, poor ionization, and the wide range of biochemical properties conferred by different acyl chain lengths. In addition, most current methods do not support analysis of CoA isotopic labeling, which is required to quantify CoA synthesis rate or to measure absolute concentration using isotope-labeled internal standards. Here, we describe a method to quantify the concentration and isotopic labeling of total CoA, defined as the sum of CoASH plus all acyl-CoA species. Acyl-CoA species are hydrolyzed using sodium hydroxide to remove acyl chains, then CoA is derivatized on the thiol with N-ethylmaleimide (NEM). Following protein precipitation and solid phase extraction, samples are analyzed by liquid chromatography-mass spectrometry. This method is linear in a wide range that captures mouse tissue CoA levels, with accuracy within 15% error and precision below 15% relative standard deviation for both pure standards and tissue samples. We applied this method to measure total CoA concentration in five tissues from male and female mice, and total CoA synthesis rate in mouse liver via infusion of 13C-15N-pantothenate. Overall, this method offers a tractable approach to measure total CoA concentration and isotopic labeling to enable study of total CoA synthesis rates and concentrations in health and disease.

biochemistry↗

bioRxiv2025

Synthesis of stable isotope labeled analogs of phytanic acid for separate and combined tracing of alpha-, beta- and omega-oxidation

Phytanic acid (3,7,11,15-tetramethylhexadecanoic acid) is a branched very long chain fatty acid (VLCFA) derived in humans from the diet and catabolized via peroxisomal metabolism. Catabolism of phytanic acid is important in humans as certain inborn errors of peroxisomal metabolism, including Refsum Disease, manifest when catabolism of diet derived phytanic acid is impaired. We developed a novel, linear, unified, unoptimized synthesis of all-racemic phytanic acid along with its 2,3,6,7,10,11,14,15-d8, 1,2-13C2, and 1,2-13C2-2,3,6,7,10,11,14,15-d8 stable isotope labeled analogs from commercially available materials including the common starting material ethyl 2-bromoacetate and ethyl 2-bromoacetate-13C2. This improves upon previous synthetic work to provide a simple synthetic route to produce amounts of stable isotope labeled analogs useful for biochemical studies. The neutron encoded position of the stable isotope enrichment allow distinct examination of oxidative pathways of catabolism, allowing comparison of alpha, beta, and omega oxidation through the combination of labels. This provides a useful set of stable isotope labeled analogs for studies of phytanic acid and branched VLCFA metabolism.

biochemistry↗

bioRxiv2025

Opposing effects of systemic and pancreas-specific inhibition of BCKDK on pancreatic carcinogenesis

Branched-chain amino acid (BCAA) metabolism is perturbed in patients with pancreatic cancer, but the contribution of systemic or pancreas-intrinsic BCAA catabolism to pancreatic carcinogenesis is unclear. We show here that pancreas-specific loss of DBT, the E2 subunit of the branched-chain keto-acid dehydrogenase (BCKDH) complex required for BCAA oxidation, strikingly exacerbates premalignant pancreatic intraepithelial neoplasia (PanIN) lesions in KC (p48-Cre;KrasLSL-G12D/+) mice. However, deletion of upstream enzyme BCAT2 neither phenocopied nor rescued loss of DBT in KC mice, ruling out involvement of both upstream and downstream metabolites as mediators of PanIN promotion. Instead, we observed that DBT deficiency led to loss of the kinase BCKDK, a negative regulator of the BCKDH complex, and that, remarkably, pancreas-specific loss of BCKDK phenocopied DBT deficiency in accelerating PanIN formation. These data thus support a model in which pancreas BCKDK restrains tumorigenesis. In contrast, systemic treatment of KC mice with the BCKDK inhibitor BT2, which inhibits BCKDH phosphorylation across many tissues except the pancreas, reduced PanIN formation and preserved normal acinar area. Together the data reveal the promotion of BCAA catabolism systemically, but not within the pancreas, as a promising intervention strategy to suppress tumor initiation.

cancer biology↗

bioRxiv2025

A nuclear branched-chain amino acid catabolism pathway controls histone propionylation in pancreatic cancer

Branched-chain amino acid (BCAA) catabolism contributes prominently to the TCA cycle in the healthy pancreas but is suppressed in pancreatic ductal adenocarcinoma (PDA). The impact of this metabolic remodeling on cancer phenotypes remains poorly understood. Here, we find that the BCAA isoleucine is a primary source of propionyl-CoA in PDA cells. Reduction of propionyl-CoA availability by either genetic perturbation or isoleucine and valine starvation decreases histone propionylation (Kpr) without impacting histone acetylation on specific lysine sites, correlating with reduced transcription of certain lipid- and immune-related genes. Mechanistically, we find that multiple enzymes of isoleucine catabolism unexpectedly localize to and carry out multi-step isoleucine oxidation within the nuclei of PDA cells. Importantly, nuclear localization of the rate-limiting branched-chain alpha ketoacid dehydrogenase (BCKDH) complex is essential for isoleucine-dependent Kpr and gene regulation. Moreover, we demonstrate that isoleucine-sensitive Kpr and its associated gene expression are driven by the MYST family of lysine acyltransferases (KATs), and that the BCKDHA subunit of the BCKDH complex interacts with KAT7 within the nuclear compartment. BCAA catabolism enzymes are apparent in the nuclei of PanIN lesions in mice and PDA tumors in patients, contrasting that in healthy pancreatic acinar and ductal cells. Collectively, these findings unveil a nuclear isoleucine catabolism pathway and highlight its role in controlling histone Kpr and tumorigenic transcriptional programs in PDA.

cancer biology↗

bioRxiv2025

Class I histone deacetylases catalyze lysine lactylation

Metabolism and post-translational modifications (PTMs) are intrinsically linked and the number of identified metabolites that can covalently modify proteins continues to increase. This metabolism/PTM crosstalk is especially true for lactate, the product of anaerobic metabolism following glycolysis. Lactate forms an amide bond with the {varepsilon}-amino group of lysine, a modification known as lysine lactylation, or Kla. Multiple independent mechanisms have been proposed in the formation of Kla, including p300/CBP-dependent transfer from lactyl-CoA, via a high-energy intermediate lactoylglutathione species that non-enzymatically lactylates proteins, and several enzymes are reported to have lactyl transferase capability. We recently discovered that class I histone deacetylases (HDACs) 1, 2, and 3 can all reverse their canonical chemical reaction to catalyze lysine {beta}-hydroxybutyrylation. Here we tested the hypothesis that HDACs can also catalyze Kla formation. Using biochemical, pharmacological, and genetic approaches, we found that HDAC-catalyzed lysine lactylation accounts for the majority of Kla formation in cells. Dialysis experiments confirm this is a reversible reaction that depends on lactate concentration. We also directly quantified intracellular lactyl-CoA and found that Kla abundance can be uncoupled from lactyl-CoA levels. Therefore, we propose a model in which the majority of Kla is formed through enzymatic addition of lactate by HDACs 1, 2, and 3.

biochemistry↗

bioRxiv2025

CDKN2ALow cancer cells outcompete macrophages for microenvironmental zinc to drive immunotherapy resistance

Anti-PD1 therapies are primarily thought to rely on functional T cell responses; yet tumors with limited T cell infiltration can still benefit, suggesting alternative mechanisms contribute to therapeutic efficacy. Indeed, we found that myeloid-rich, T cell-poor tumor models respond to anti-Pd1, and this is dependent on a cancer cell-macrophage crosstalk mediated by cancer cell Cdkn2a expression. Mechanistically, we found that cancer cells with decreased Cdkn2a expression (Cdkn2aLow), which occurs in [~]50% of all human cancers, reorganize zinc compartmentalization by upregulating the zinc importer Slc39a9 at the plasma membrane. Increased cancer cell plasma membrane Slc39a9 leads to intracellular zinc accumulation in cancer cells and depletion of zinc in the tumor microenvironment (TME), resulting in zinc-starved tumor-associated macrophages (TAMs) with reduced phagocytic activity. Restoring zinc availability in TAMs--via dietary supplementation or Slc39a9 knockdown in cancer cells--reprograms TAMs to a pro-phagocytic state and sensitizes Cdkn2aLow tumors to anti-Pd1 therapy. Remarkably, Slc39a9 knockdown tumors respond to anti-Pd1 in Rag1-/- mice, and co-injection of zinc-replete macrophages is sufficient to drive an anti-Pd1 response in immunodeficient mice, demonstrating the T cell-independent nature of this response. Clinically, TAMs from CDKN2ALow cancer patients show reduced zinc and phagocytosis gene signatures. Moreover, patients with lower circulating zinc levels have significantly worse time-to-event outcomes than those with higher levels. Together, these findings uncover a previously unrecognized mechanism by which Cdkn2aLow cancer cells outcompete TAMs for zinc, impairing their function and limiting anti-Pd1 efficacy. They also provide evidence that macrophages alone, without T cells, can enhance anti-PD1 response through zinc-mediated reprogramming of phagocytosis.

cancer biology↗

bioRxiv2024

Acetate drives ovarian cancer quiescence via ACSS2-mediated acetyl-CoA production

Quiescence is a reversible cell cycle exit traditionally thought to be associated with a metabolically inactive state. Recent work in muscle cells indicates that metabolic reprogramming is associated with quiescence. Whether metabolic changes occur in cancer to drive quiescence is unclear. Using a multi-omics approach, we found that the metabolic enzyme ACSS2, which converts acetate into acetyl-CoA, is both highly upregulated in quiescent ovarian cancer cells and required for their survival. Indeed, quiescent ovarian cancer cells have increased levels of acetate-derived acetyl-CoA, confirming increased ACSS2 activity in these cells. Furthermore, either inducing ACSS2 expression or supplementing cells with acetate was sufficient to induce a reversible quiescent cell cycle exit. RNA-Seq of acetate treated cells confirmed negative enrichment in multiple cell cycle pathways as well as enrichment of genes in a published G0 gene signature. Finally, analysis of patient data showed that ACSS2 expression is upregulated in tumor cells from ascites, which are thought to be more quiescent, compared to matched primary tumors. Additionally, high ACSS2 expression is associated with platinum resistance and worse outcomes. Together, this study points to a previously unrecognized ACSS2-mediated metabolic reprogramming that drives quiescence in ovarian cancer. As chemotherapies to treat ovarian cancer, such as platinum, have increased efficacy in highly proliferative cells, our data give rise to the intriguing question that metabolically-driven quiescence may affect therapeutic response.

cancer biology↗

bioRxiv2024

αKG-mediated carnitine synthesis promotes homologous recombination via histone acetylation

Homologous recombination (HR) deficiency enhances sensitivity to DNA damaging agents commonly used to treat cancer. In HR-proficient cancers, metabolic mechanisms driving response or resistance to DNA damaging agents remain unclear. Here we identified that depletion of alpha-ketoglutarate (KG) sensitizes HR-proficient cells to DNA damaging agents by metabolic regulation of histone acetylation. KG is required for the activity of KG-dependent dioxygenases (KGDDs), and prior work has shown that changes in KGDD affect demethylases. Using a targeted CRISPR knockout library consisting of 64 KGDDs, we discovered that Trimethyllysine Hydroxylase Epsilon (TMLHE), the first and rate-limiting enzyme in de novo carnitine synthesis, is necessary for proliferation of HR-proficient cells in the presence of DNA damaging agents. Unexpectedly, KG-mediated TMLHE-dependent carnitine synthesis was required for histone acetylation, while histone methylation was affected but dispensable. The increase in histone acetylation via KG-dependent carnitine synthesis promoted HR-mediated DNA repair through site- and substrate-specific histone acetylation. These data demonstrate for the first time that HR-proficiency is mediated through KG directly influencing histone acetylation via carnitine synthesis and provide a metabolic avenue to induce HR-deficiency and sensitivity to DNA damaging agents.

cancer biology↗

bioRxiv2023

ATR promotes mTORC1 activation via de novo cholesterol synthesis in p16-low cancer cells

DNA damage and cellular metabolism exhibit a complex interplay characterized by bidirectional feedback mechanisms. Key mediators of the DNA damage response and cellular metabolic regulation include Ataxia Telangiectasia and Rad3-related protein (ATR) and the mechanistic Target of Rapamycin Complex 1 (mTORC1), respectively. Previous studies have established ATR as a regulatory upstream factor of mTORC1 during replication stress; however, the precise mechanisms by which mTORC1 is activated in this context remain poorly defined. Additionally, the activity of this signaling axis in unperturbed cells has not been extensively investigated. Here, we demonstrate that ATR promotes mTORC1 activity across various cellular models under basal conditions. This effect is particularly enhanced in cells following the loss of p16, which we have previously associated with hyperactivation of mTORC1 signaling and here found have increased ATR activity. Mechanistically, we found that ATR promotes de novo cholesterol synthesis and mTORC1 activation through the upregulation of lanosterol synthase (LSS), independently of both CHK1 and the TSC complex. Furthermore, the attenuation of mTORC1 activity resulting from ATR inhibition was rescued by supplementation with lanosterol or cholesterol in multiple cellular contexts. This restoration corresponded with enhanced localization of mTOR to the lysosome. Collectively, our findings demonstrate a novel connection linking ATR and mTORC1 signaling through the modulation of cholesterol metabolism.

cancer biology↗

bioRxiv2023

Lactoylglutathione promotes inflammatory signaling in macrophages

Chronic, systemic inflammation is a pathophysiological manifestation of metabolic disorders. Inflammatory signaling leads to elevated glycolytic flux and a metabolic shift towards aerobic glycolysis and lactate generation. This rise in lactate corresponds with increased generation of lactoylLys modifications on histones, mediating transcriptional responses to inflammatory stimuli. Lactoylation is also generated through a non-enzymatic S-to-N acyltransfer from the glyoxalase cycle intermediate, lactoylglutathione (LGSH). Here, we report a regulatory role for LGSH in inflammatory signaling. In the absence of the primary LGSH hydrolase, glyoxalase 2 (GLO2), RAW264.7 macrophages display significant elevations in LGSH, while demonstrating a potentiated inflammatory response when exposed to lipopolysaccharides, corresponding with a rise in histone lactoylation. Interestingly, our data demonstrate that lactoylation is associated with more compacted chromatin than acetylation in an unstimulated state, however, upon stimulation, regions of the genome associated with lactoylation become markedly more accessible. Lastly, we demonstrate a spontaneous S-to-S acyltransfer of lactate from LGSH to CoA, yielding lactoyl-CoA. This represents the first known mechanism for the generation of this metabolite. Collectively, these data suggest that LGSH, and not intracellular lactate, is a primary contributing factor facilitating the inflammatory response.

biochemistry↗

bioRxiv2023

Trogocytosis of cancer-associated fibroblasts promotes pancreatic cancer growth and immune suppression via phospholipid scramblase anoctamin 6 (ANO6).

In pancreatic ductal adenocarcinoma (PDAC), the fibroblastic stroma constitutes most of the tumor mass and is remarkably devoid of functional blood vessels. This raises an unresolved question of how PDAC cells obtain essential metabolites and water-insoluble lipids. We have found a critical role for cancer-associated fibroblasts (CAFs) in obtaining and transferring lipids from blood-borne particles to PDAC cells via trogocytosis of CAF plasma membranes. We have also determined that CAF-expressed phospholipid scramblase anoctamin 6 (ANO6) is an essential CAF trogocytosis regulator required to promote PDAC cell survival. During trogocytosis, cancer cells and CAFs form synapse-like plasma membranes contacts that induce cytosolic calcium influx in CAFs via Orai channels. This influx activates ANO6 and results in phosphatidylserine exposure on CAF plasma membrane initiating trogocytosis and transfer of membrane lipids, including cholesterol, to PDAC cells. Importantly, ANO6-dependent trogocytosis also supports the immunosuppressive function of pancreatic CAFs towards cytotoxic T cells by promoting transfer of excessive amounts of cholesterol. Further, blockade of ANO6 antagonizes tumor growth via disruption of delivery of exogenous cholesterol to cancer cells and reverses immune suppression suggesting a potential new strategy for PDAC therapy.

cancer biology↗

bioRxiv2023

Acyl-CoA thioesterase-2 facilitates beta-oxidation in glycolytic skeletal muscle in a lipid supply dependent manner

Acyl-Coenzyme A (acyl-CoA) thioesters are compartmentalized intermediates that participate in in multiple metabolic reactions within the mitochondrial matrix. The limited availability of free CoA (CoASH) in the matrix raises the question of how the local acyl-CoA concentration is regulated to prevent trapping of CoASH from overload of any specific substrate. Acyl-CoA thioesterase-2 (ACOT2) hydrolyzes long-chain acyl-CoAs to their constituent fatty acids and CoASH, and is the only mitochondrial matrix ACOT refractory to inhibition by CoASH. Thus, we reasoned that ACOT2 may constitutively regulate matrix acyl-CoA levels. Acot2 deletion in murine skeletal muscle (SM) resulted in acyl-CoA build-up when lipid supply and energy demands were modest. When energy demand and pyruvate availability were elevated, lack of ACOT2 activity promoted glucose oxidation. This preference for glucose over fatty acid oxidation was recapitulated in C2C12 myotubes with acute depletion of Acot2, and overt inhibition of {beta}-oxidation was demonstrated in isolated mitochondria from Acot2-depleted glycolytic SM. In mice fed a high fat diet, ACOT2 enabled the accretion of acyl-CoAs and ceramide derivatives in glycolytic SM, and this was associated with worse glucose homeostasis compared to when ACOT2 was absent. These observations suggest that ACOT2 supports CoASH availability to facilitate {beta}-oxidation in glycolytic SM when lipid supply is modest. However, when lipid supply is high, ACOT2 enables acyl-CoA and lipid accumulation, CoASH sequestration, and poor glucose homeostasis. Thus, ACOT2 regulates matrix acyl-CoA concentration in glycolytic muscle, and its impact depends on lipid supply.

biochemistry↗