Biology subjects

Shah, H.

Publications and source records attributed to Shah, H..

At least 19 recordsLinked to original sources

bioRxiv2026

Latent Transforming Growth Factor Binding Protein ? 2 promotes microfibrillar TGF-? bioavailability to drive pathologic fibrosis in remote regions of infarcted hearts

Myocardial infarction (MI) initiates ventricular remodeling that extends beyond the infarct into remote, viable myocardium, where diffuse extracellular matrix (ECM) remodeling and stiffening contribute to progressive dysfunction and heart failure. Latent transforming growth factor binding protein 2 (LTBP2) is an injury-induced, microfibril-associated ECM glycoprotein that, among the LTBP family, does not covalently bind latent TGF-?. We asked whether LTBP2 regulates remote remodeling after MI, and how a protein lacking latent TGF-??binding capacity could influence TGF-??dependent fibrosis. Wild-type and Ltbp2-null mice underwent permanent coronary ligation or sham surgery and were followed for 28 days by echocardiography and speckle-tracking strain analysis. Remote myocardium was assessed by histology, atomic force microscopy, and quantitative proteomics. Mechanism was interrogated in primary cardiac fibroblasts using a TGF-? reporter assay. Sufficiency was tested with a fibrillin-1?binding module of LTBP2 delivered as purified protein or by lentiviral expression. LTBP2 was induced in injury-activated cardiac fibroblasts and localized to infarct and remote myocardium by 7 days post-MI. Ltbp2 deletion improved 28-day survival (P=0.0272) where Ltbp2-null hearts showed preserved ejection fraction and faster diastolic strain rates, with protection concentrated in segments remote from the infarct. Remote myocardium contained less interstitial collagen and was significantly less stiff. Proteomic profiling showed enrichment of ECM organization and TGF-??responsive programs in wild-type hearts that was attenuated in knockouts. In fibroblasts, loss of LTBP2 increased LTBP1 matrix incorporation and shifted TGF-? from the soluble to the matrix-bound compartment; conversely, the minimal LTBP2 module bound fibrillin-1 directly and mobilized latent TGF-? from established matrix within 20 minutes. LTBP2 drives maladaptive remodeling of remote myocardium after MI by limiting matrix sequestration of latent TGF-? and expanding the activatable pool, resolving how an LTBP that does not bind latent TGF-? amplifies TGF-??dependent fibrosis. LTBP2 and its fibrillin-1 interaction surface may be tractable targets.

physiology↗

bioRxiv2026

Adenosylhomocysteinase drives epigenetic and metabolic reprogramming in ZFTA-RELA ependymoma

Supratentorial ependymomas (ST-EPNs) are aggressive pediatric brain tumors predominantly driven by the recurrent ZFTA-RELA fusion, an oncogenic chromatin regulator that establishes an aberrant transcriptional program. Although metabolic pathways modulate epigenetic regulation by controlling the availability of metabolic cofactors, how ZFTA-RELA coordinates metabolic reprogramming with epigenetic regulation is not well understood. Here, we show that ZFTA-RELA-positive ependymomas exhibit enhanced methionine dependency, elevated adenosyl homocysteinase (AHCY) expression, and epigenetically control aspartate metabolism for tumor growth. Mechanistically, ZFTA-RELA upregulates AHCY, increasing cellular methylation potential which promotes H3K4me3-dependent expression of CAD, the first enzyme complex of de novo pyrimidine biosynthesis, while simultaneously enforcing H3K27me3 mediated repression of ASNS, which encodes asparagine synthetase. Through this coordinated epigenetic program, aspartate utilization is directed toward pyrimidine biosynthesis while endogenous asparagine production is limited. Restricting S-adenosylmethionine availability or genetically or pharmacologically inhibiting AHCY reverses these epigenetic states, leading to CAD downregulation, ASNS upregulation, impaired nucleotide synthesis, and suppression of tumor growth in vitro and in vivo. Similarly, EZH2 inhibition also restores ASNS expression and suppresses tumor proliferation. These findings suggest that ZFTA-RELA EPN maintain ASNS-low phenotype which conditionally make them dependent on extracellular asparagine. We further show that enhanced de novo pyrimidine synthesis not only supports nucleotide production but also provides UDP-sugars required for N-glycosylation and stabilization of the asparagine transporter SLC1A5, thereby promoting extracellular asparagine uptake and tumor proliferation. Collectively, our findings identify AHCY as a critical metabolic regulator of epigenetic and metabolic reprogramming that drives pyrimidine synthesis and establishes extracellular asparagine dependency, revealing actionable metabolic vulnerabilities in ZFTA-RELA-positive ST-EPNs.

cancer biology↗

bioRxiv2026

MCT1 activity defines an aggressive metabolic phenotype and therapeutic target in non-small cell lung cancer

Lactate uptake through monocarboxylate transporter 1 (MCT1) is associated with aggressive disease in non-small cell lung cancer (NSCLC), but how lactate transport supports tumor metabolism remains incompletely understood. Integrating stable isotope tracing, metabolomics, and transcriptomics across patient tumors, animal models, and cultured cells, we show that elevated lactate utilization and SLC16A1 expression correlate with worse clinical outcomes in NSCLC. Although MCT1 inhibition with AZD3965 does not significantly impair tumor growth as a monotherapy, it depletes purine-associated metabolite pools, alters redox balance, and induces a conserved transcriptional response involving MYC target dysregulation and suppression of nucleotide metabolism genes. Addition of exogenous hypoxanthine, or expression of the E. coli-derived NADH-producing enzyme soluble transhydrogenase, partially rescues the effects of MCT1 inhibition. Importantly, this metabolically compromised state sensitizes NSCLC to nucleotide-targeting chemotherapies, including pemetrexed. These findings reveal that MCT1 mediated lactate uptake sustains nucleotide homeostasis in NSCLC, and that its inhibition exposes a context-dependent vulnerability that can be leveraged to enhance chemotherapy efficacy.

cancer biology↗

bioRxiv2026

Myeloid-targeted RNA nanotherapeutics rewire cholesterol metabolism to unleash anti-tumor immunity in glioblastoma

Tumor-associated myeloid cells (TAMCs) dominate the glioblastoma (GBM) microenvironment and suppress anti-tumor immunity. Here, we identify cholesterol efflux via ABCA1 as a targetable metabolic checkpoint controlling TAMC immunosuppression in GBM. Reprogramming TAMC cholesterol metabolism using TAMC-targeting lipid nanoparticle encapsulating ABCA1 siRNA (ABCA1 LNP) converts TAMCs into potent antigen-presenting cells with enhanced pro-inflammatory activity and antigen-presenting capacity, thereby inducing T cell activation, expansion, and tumor infiltration. Mechanistically, ABCA1 blockade induces cholesterol accumulation in TAMC membranes, promoting lipid raft formation and enhancing MHC-I-mediated antigen presentation. In multiple preclinical GBM models, ABCA1 LNP treatment dramatically induces T cell priming, extends animal survival, and overcomes GBM resistance to radiotherapy and immune checkpoint therapy. This efficacy was well-maintained in stem-like and recurrent GBM models, GBM patient specimens, and a renal cell carcinoma model. Altogether, our work identifies cholesterol efflux as a targetable metabolic vulnerability in TAMCs to overcome therapy resistance in myeloid-rich, immunologically "cold" tumors.

immunology↗

bioRxiv2026

Gut Microbiota-derived Acetate Safeguards the Colonic Epithelial Acetyl-CoA Reserve to Avert Colonic Senescence

Aging is a major driver of tissue senescence, but little is known about the development of age-unrelated tissue senescence. Here we show that nucleocytosolic acetyl-CoA deficiency in colon epithelial cells, caused by Acly ablation and bacterial depletion, triggers age-independent, p53-dependent colonic senescence leading to severe systemic inflammation. Acetate supplementation, acetate-producing bacterial transplantation, targeted depletion of senescent cells or treatment with lysine deacetylase inhibitors blocks colonic senescence and inflammatory injury. Spontaneous colonic senescence develops following simultaneous deletion of epithelial Acly and Acss2, confirming that microbe-derived acetate maintains the epithelial acetyl-CoA pool via ACSS2 to avert colonic senescence. Mechanistically, acetyl-CoA deficiency deprives a cohort of mitochondrial and nuclear proteins of acetylation, leading to increased oxidative stress and DNA repair stress that trigger cellular senescence. Among these proteins, ATP5F1A-K161 acetylation and H4-K5/8 acetylation are required to protect colonic epithelial cells from developing senescence. These observations unveil a previously unknown mechanism that governs colonic senescence.

physiology↗

bioRxiv2026

Melatonin improves neuro-behavioral perturbations in diet/photoperiod induced chronodisruption

Endogenous circadian oscillators regulate learning, cognitive performance and memory are disrupted due to circadian shifts. High-fat-high-fructose (H) diet, photoperiodic shifts induced chronodisruption (CD) and a combination (HCD) causes neurobehavioral perturbations wherein; the merits of exogenous melatonin in alleviating the said behavioral deficits are studied herein. Indices of anxiety (marble burying test, elevated plus maze test and hole board test) and depressive behavior (sucrose preference test, forced swim test and tail suspension test) were elevated in H, CD and HCD groups. Significant increments in the titres of thyroid hormone levels (T3, T4 and TSH) and mRNA levels of hippocampal pro-inflammatory genes (Tnf-, Il-1{beta}, Il-4, Il-6, Il-10, Il-12, Il-17, Mcp-1 and Nf-{kappa}b) in the said experimental groups corroborates with the said changes. Exogenous melatonin treatment to the said experimental groups viz. HM, CDM and HCDM; accounted for moderate to significant improvement in the said neurobehavioral perturbations and hippocampal inflammatory markers. Hippocampal BDNF-TrkB pathway genes of H, CD and HCD had recorded a non-significant downregulation in mRNA but without prominent changes in proteins. Likewise, melatonin-treated groups showed moderate to significant improvement in transcripts of Bdnf, Trkb, Nt-3, Nt-4, Psd-95 and Syn-1. Herein, we report neurobehavioral perturbations caused by a combination of H and CD. Melatonin-mediated improvement in neurobehavior and the corrective changes in hippocampal BDNF-TrkB pathway implies towards the potential anxiolytic and anti-depressive activity as reported herein.

animal behavior and cognition↗

bioRxiv2026

An Advanced Mobile Laboratory to enable field-based microbial ecology and cell biology across scales

Microbial biodiversity is central to ecosystem function, yet mechanistic insights into the cell biology of environmental organisms remain limited. The underlying challenges are twofold: most microbes remain uncultivable, and a persistent gap exists between field sampling and laboratory analyses. Here, we introduce the Advanced Mobile Laboratory (AML), a field-deployable platform that integrates confocal microscopy, image-enabled cell sorting, and cryo-preparation for expansion and electron microscopy. This setup enables immediate, standardized processing and analysis of environmental communities directly at the sampling site. We demonstrate its capability using marine eukaryotic plankton, showing how the AML enables multiscale investigations, from live imaging of natural communities to enabling ultrastructural and single-cell omics analyses, while minimizing sample degradation and enabling on-site experimentation. By bringing high-end sample preparation and analytical capacity into the field, the AML enables studying life in its natural context to mechanistically understand lifes diversity in the environment.

cell biology↗

bioRxiv2026

Microtubules sustain the fidelity of cellularization in a coenocytic relative of animals

Cellularization is the coordinated division of a multinucleate cytoplasm into many cells.1-3 Multinucleation is a common life cycle strategy observed across eukaryotic lineages, including in microbial eukaryotes, fungi, plants and animals, and is associated with the ability to transition to a unicellular state through cellularization.4 In the best-studied model for this process, Drosophila melanogaster, cellularization requires the coordinated action of actin and microtubule (MT) networks to bring about the synchronous invagination of plasma membrane furrows, but the extent of conservation of these mechanisms across eukaryotes remains unknown.1,5,6 Here we investigate cellularization in the ichthyosporean Sphaeroforma arctica, a close relative of animals with a multinucleate life cycle stage.7-9 Using live cell imaging, ultrastructure expansion microscopy (U-ExM) and volume electron microscopy, we define the membrane, MT and actin dynamics that accompany cellularization in S. arctica. Using pharmacological inhibitors and centrifugation, we show that MTs, in addition to positioning nuclei, play a role in guiding nascent furrows to sustain equi-partitioning of nuclei and cytoplasm between daughter cells. Our findings indicate that cellularization is regulated through crosstalk between actin and MT networks, exhibiting mechanistic parallels with canonical cytokinesis, and establish S. arctica as a valuable model for investigating general principles of cellularization.

cell biology↗

bioRxiv2025

Chronic semaglutide treatment reveals stage-dependent changes to feeding behavior and metabolic adaptations in male mice

Glucagon-like peptide-1 receptor (Glp1r) agonists have transformed obesity treatment, but weight loss responses to these drugs vary widely. Elucidating behavioral and metabolic phenotypes throughout Glp1r agonist treatment could identify mechanisms underlying this response spectrum. We characterized food intake, meal patterns, energy expenditure (EE), and substrate oxidation during chronic semaglutide treatment and post-treatment recovery in obese male mice at room temperature (RT) and thermoneutral temperature (TN). Semaglutide-induced weight loss and post-treatment weight regain were similar at RT and TN. Weight loss was divided into three stages at both temperatures: 1) rapid initial weight loss, 2) slower gradual weight loss, and 3) weight maintenance. Initial weight loss was marked by reduced food intake, smaller and less frequent meals, and increased lipid oxidation. Food intake gradually returned to pre-treatment levels through increased meal frequency, while meal size remained suppressed. Lipid oxidation gradually decreased while carbohydrate oxidation increased. Weight-adjusted EE and locomotor activity increased throughout semaglutide treatment. Mice rapidly regained weight after treatment cessation, and this was associated with increased food intake, meal size and frequency, carbohydrate oxidation, EE, and activity. These findings reveal that semaglutide-induced weight loss and regain after treatment cessation involve dynamic, stage-specific changes in feeding behavior, EE, and substrate oxidation. ARTICLE HIGHLIGHTSO_LIAlthough many studies demonstrate acute behavioral and metabolic effects of glucagon- like peptide-1 receptor (Glp1r) agonists, few have assessed chronic effects of these drugs on these phenotypes. C_LIO_LIWe wanted to assess changes to various behavioral and metabolic phenotypes throughout a chronic treatment regimen with semaglutide and post-treatment. C_LIO_LIWeight loss in response to chronic semaglutide treatment can be divided into distinct phases, and each phase is characterized by different effects on food intake, meal patterns, energy expenditure, and substrate oxidation. C_LIO_LIOur findings suggest that differences in behavioral changes and/or metabolic adaptations may underlie the degree of weight loss responsiveness to Glp1r agonists. C_LI

physiology↗

bioRxiv2025

Mdm2 restrains the activity of the CRL4Cdt2 E3 ubiquitin ligase to promote cell cycle progression through the G2/M phase

The canonical function of the Mdm2 oncoprotein is widely recognized as the negative regulation of the p53 tumor suppressor. However, growing evidence indicates that its physiological activities extend far beyond p53. Here, we show that Mdm2 promotes cell cycle progression at the G2/M phase through the ubiquitin-mediated degradation of the substrate recognition adaptor Cdt2 of the CRL4Cdt2 E3 ubiquitin ligase complex, independently of p53. The attenuation of CRL4Cdt2 activity by Mdm2 stabilizes its cell cycle-specific substrates including p21, Set8, and Cdt1, at the G2/M phase following their proteasomal degradation in the S phase. Furthermore, the delay in cell cycle progression at the G2/M phase and the decreased cell proliferation observed in the absence of Mdm2 are largely caused by an increase in Cdt2 and a subsequent decrease in p21. Collectively, our data illustrate a previously unexplored mechanism by which Mdm2 regulates the cell cycle and promotes cellular proliferation by neutralising the CR4Cdt2 E3 ubiquitin ligase activity and subsequently stabilizing p21.

molecular biology↗

bioRxiv2025

A genetically encoded bifunctional enzyme mitigates redox imbalance and lipotoxicity via engineered Gro3P-Glycerol shunt

Dihydroxyacetone phosphate (DHAP), glycerol-3-phosphate (Gro3P) and reduced/oxidized nicotinamide adenine dinucleotide (NADH/NAD+) are key metabolites of the Gro3P shuttle system that forms a redox circuit, allowing transfer of reducing equivalents between cytosol and mitochondria. Targeted activation of Gro3P biosynthesis was recently identified as a promising strategy to alleviate reductive stress by promoting NAD+ recycling, including in cells with an impaired mitochondrial complex I. However, because Gro3P constitutes the backbone of triglycerides under some circumstances, its accumulation can lead to excessive fat deposition. Here, we present the development of a novel genetically encoded tool based on a di-domain glycerol-3-phosphate dehydrogenase from algae Chlamydomonas reinhardtii (CrGPDH), which is a bifunctional enzyme that can recycle NAD+ while converting DHAP to Gro3P. In addition, this enzyme possesses an N-terminal domain which cleaves Gro3P into glycerol and inorganic phosphate (Pi) (in humans and other organisms, this reaction is catalyzed by a separate glycerol-3-phosphate phosphatase, a reaction also known as "glycerol shunt"). When expressed in mammalian cells, CrGPDH diminished Gro3P levels and boosted the TCA cycle and fatty acid {beta}-oxidation in mitochondria. CrGPDH expression alone supported proliferation of HeLa cells under conditions of either inhibited activity of the mitochondrial electron transport chain or hypoxia. Moreover, human kidney cancer cells, which exhibit abnormal lipid accumulation, had decreased triglycerides levels when expressing CrGPDH. Our findings suggest that the coordinated boosting of both Gro3P biosynthesis and glycerol shunt may be a viable strategy to alleviate consequences of redox imbalance and associated impaired lipogenesis in a wide repertoire of conditions, ranging from primary mitochondrial diseases to obesity, type 2 diabetes, and metabolic dysfunction-associated steatotic liver disease (MASLD).

bioengineering↗

bioRxiv2025

Creatine synthesis is a tumor suppressor pathway hypostatic to one-carbon metabolism

Methylene tetrahydrofolate reductase 2 (MTHFD2), the rate-limiting enzyme of mitochondrial one-carbon metabolism, is one of the most highly expressed metabolic enzymes across diverse cancers and lymphoproliferative disorders. However, its exact roles in oncogenic metabolism remain poorly defined. We show that MTHFD2 is a key regulator of mitochondrial energetics in Epstein-Barr virus-transformed B lymphoblastoid cell lines (LCLs), an in vitro model of post-transplant lymphoproliferative disorder (PTLD). We also delineate a role for MTHFD2 in fueling de novo creatine synthesis; MTHFD2 mediates the production of glycine, a necessary substrate for creatine synthesis, through serine catabolism. Aminomethyltransferase (AMT) suppression short-circuits the glycine cleavage system (GCS) to augment LCL mitochondrial glycine levels. Creatine synthesis is hypostatic to mitochondrial one-carbon metabolism; inhibition of creatine synthesis improves LCL fitness only when MTHFD2 is lost. Our findings emplace MTHFD2 at the nexus of amino acid and energy metabolism pathways in LCLs, with potential clinical ramifications for PTLD. Highlights* Complete activation of creatine synthesis in an in vitro cellular model of PTLD * Creatine synthesis is a major sink for mitochondrial 1C-derived glycine * Reverse GCS activity due to AMT deficiency in lymphoblastoid cells * Epistasis between mitochondrial 1C metabolism and creatine synthesis eTOC BlurbLeung et al. demonstrate that MTHFD2 is crucial for creatine synthesis in lymphoproliferative disorders. MTHFD2 supports forward 1C flux through SHMT and drives reverse GCS activity to augment mitochondrial glycine, a substrate for creatine synthesis. Tumor-suppressive effects of creatine synthesis are unmasked with MTHFD2 loss, exhibiting metabolic epistasis.

molecular biology↗

bioRxiv2025

Microenvironmental arginine restriction sensitizes pancreatic cancers to polyunsaturated fatty acids by suppression of lipid synthesis

Nutrient limitation is a characteristic feature of poorly perfused tumors. In contrast to well-perfused tissues, nutrient deficits in tumors impose metabolic constraints on cancer cells. The metabolic constraints created by the tumor microenvironment can lead to vulnerabilities in cancers. Identifying the metabolic constraints of the tumor microenvironment and the vulnerabilities that arise in cancers can provide new insight into tumor biology and identify promising antineoplastic targets. To identify how the microenvironment constrains the metabolism of pancreatic tumors, we challenged pancreatic cancer cells with microenvironmental nutrient levels and analyzed changes in cellular metabolism. We found that arginine limitation in pancreatic tumors perturbs saturated and monounsaturated fatty acid synthesis by suppressing the lipogenic transcription factor SREBP1, in part via activation of the amino acid sensor GCN2. Synthesis of these fatty acids is critical for maintaining a balance of saturated, monounsaturated, and polyunsaturated fatty acids in cellular membranes. Because of microenvironmental constraints on fatty acid synthesis, pancreatic cancer cells and tumors are unable to maintain lipid homeostasis when exposed to polyunsaturated fatty acids, leading to cell death by ferroptosis. In sum, arginine restriction in the tumor microenvironment constrains lipid metabolism in pancreatic cancers, which renders these tumors vulnerable to polyunsaturated-enriched fats.

cancer biology↗

bioRxiv2025

Genetic vitamin B6 deficiency and alcohol interaction in behavior and metabolism

Alcohol abuse is a leading cause of preventable deaths, affecting brain function and metabolism, including GABA transmission and vitamin B6 (VB6) levels. However, the interaction between genetic VB6 deficiency and alcohol consumption remains unexplored. Here, we utilized Drosophila models with mutations in pyridox(am)ine-5-phosphate oxidase (PNPO), a key enzyme in VB6 metabolism, to examine this interaction at behavioral and biochemical levels. Our findings demonstrate that PNPO deficiency reduces alcohol aversion, increases consumption, and alters locomotor behavior. Biochemically, PNPO deficiency and alcohol exposure converge on amino acid metabolism, elevating inhibitory neurotransmitters GABA and glycine. Moreover, both PNPO deficiency and alcohol exposure lead to lethality with significant interaction, which can be rescued by VB6 supplementation. These results highlight a functional interaction between genetic VB6 deficiency and alcohol, suggesting potential therapeutic strategies for alcohol-related behaviors.

animal behavior and cognition↗

bioRxiv2025

Succinate dehydrogenase activity supports de novo purine synthesis

The de novo purine synthesis pathway is fundamental for nucleic acid production and cellular energetics, yet the role of mitochondrial metabolism in modulating this process remains underexplored. In many cancers, metabolic reprogramming supports rapid proliferation and survival, but the specific contributions of the tricarboxylic acid (TCA) cycle enzymes to nucleotide biosynthesis are not fully understood. Here, we demonstrate that the TCA cycle enzyme succinate dehydrogenase (SDH) is essential for maintaining optimal de novo purine synthesis in normal and cancer cells. Genetic or pharmacological inhibition of SDH markedly attenuates purine synthesis, leading to a significant reduction in cell proliferation. Mechanistically, SDH inhibition causes an accumulation of succinate, which directly impairs the purine biosynthetic pathway. In response, cancer cells compensate by upregulating the purine salvage pathway, a metabolic adaptation that represents a potential therapeutic vulnerability. Notably, co-inhibition of SDH and the purine salvage pathway induces pronounced antiproliferative and antitumoral effects in preclinical models. These findings not only reveal a signaling role for mitochondrial succinate in regulating nucleotide metabolism but also provide a promising therapeutic strategy for targeting metabolic dependencies in cancer.

biochemistry↗

bioRxiv2025

RNA Transcripts Serve as a Template for Double-Strand Break Repair in Human Cells

Double-strand breaks (DSBs) are toxic lesions that lead to genome instability. While canonical DSB repair pathways typically operate independently of RNA, emerging evidence suggests that RNA:DNA hybrids and transcripts near damaged sites can influence repair outcomes. However, a direct role for transcript RNA as a template during DSB repair in human cells is yet to be established. In this study, we designed fluorescent- and sequencing-based assays, which demonstrated that RNA-containing oligonucleotides and messenger RNA serve as templates to promote DSB repair. We conducted a CRISPR/Cas9-based genetic screen to identify factors that promote RNA-templated DSB repair (RT-DSBR), and of the candidate polymerases, we identified DNA polymerase-zeta (Pol{zeta}) as the potential reverse transcriptase that facilitates RT-DSBR. Furthermore, by analyzing sequencing data from cancer genomes, we identified the presence of whole intron deletions, a unique genomic scar reflective of RT-DSBR activity generated when spliced mRNA serves as the repair template. These findings highlight RT-DSBR as an alternative pathway for repairing DSBs in transcribed genes, with potential mutagenic consequences.

molecular biology↗

bioRxiv2024

Glycerol-3-phosphate activates ChREBP, FGF21 transcription and lipogenesis in Citrin Deficiency

Citrin Deficiency (CD) is caused by inactivation of SLC25A13, a mitochondrial membrane protein required to move electrons from cytosolic NADH to the mitochondrial matrix in hepatocytes. People with CD do not like sweets. We discovered that SLC25A13 loss causes accumulation of glycerol-3-phosphate (G3P), which activates carbohydrate response element binding protein (ChREBP) to transcribe FGF21, which acts in the brain to restrain intake of sweets and alcohol, and to transcribe key genes of de novo lipogenesis. Mouse and human data establish G3P-ChREBP as a new mechanistic component of the Randle Cycle that contributes to metabolic dysfunction-associated steatotic liver disease (MASLD) and forms part of a system that communicates metabolic states from liver to brain in a manner that alters food and alcohol choices. The data provide a framework for understanding FGF21 induction in varied conditions, suggest ways to develop FGF21-inducing drugs, and drug candidates for both lean MASLD and support of urea cycle function in CD.

molecular biology↗

bioRxiv2024

Role of Arginine and its Metabolism in TGF-β-Induced Activation of Lung Fibroblasts

Arginine is a conditionally essential amino acid with known roles in protein production, nitric oxide synthesis, biosynthesis of proline and polyamines, and regulation of intracellular signaling pathways. Arginine biosynthesis and catabolism have been linked to TGF-{beta}-induced activation of fibroblasts in the context of pulmonary fibrosis; however, a thorough study on the metabolic and signaling roles of arginine in the process of fibroblast activation has not been conducted. Here, we used metabolic dropouts and labeling strategies to determine how activated fibroblasts utilize arginine. We found that arginine limitation leads to activation of GCN2 while inhibiting TGF-{beta}-induced mTORC1 activation and collagen protein production. Extracellular citrulline could rescue the effect of arginine deprivation in an ASS1-dependent manner. Using metabolic tracers of arginine and its precursors, we found little evidence of arginine synthesis or catabolism in lung fibroblasts treated with TGF-{beta}. Extracellular ornithine or glutamine were the primary sources of ornithine and polyamines, not arginine. Our findings suggest that the major role for arginine in lung fibroblasts is for charging of arginyl-tRNAs and for promotion of mTOR signaling. Highlights- Arginine depletion inhibits TGF-{beta}-induced transcription in human lung fibroblasts (HLFs). - Arginine is not significantly catabolized in HLFs either through NOS or ARG dependent pathways. - Extracellular glutamine and ornithine are the primary sources of polyamines in lung fibroblasts. - The primary role of arginine in lung fibroblasts is for signaling through mTOR and GNC2.

cell biology↗