Biology subjects

Shi, X.

Publications and source records attributed to Shi, X..

At least 109 records · Page 6Linked to original sources

bioRxiv2024

Modulating Cardiac Energetics in Cardio-Metabolic Syndromes: A mechanistic, hyperpolarized MR Trial of Ninerafaxstat Treatment

BackgroundType 2 diabetes (T2D) and obesity are key contributors for heart failure (HF)- development, especially for HF with a preserved ejection fraction (HFpEF). On a molecular basis, excessive use of fatty acids (FA) induces lipotoxicity which in turn promotes inflammation, reduces mitochondrial pyruvate dehydrogenase (PDH) activity and impairs myocardial energetics and -function. Harnessing in-vivo, real time measurement of cellular metabolism via hyperpolarized pyruvate MR, we aimed to assess the effects of ninerafaxstat, a selective FA oxidation inhibitor, on cardiac energetics, metabolism & diastolic function in patients with cardio-metabolic syndromes. MethodsIMPROVE-DiCE was an open-label, mechanistic phase 2a trial. 21 participants received 200mg ninerafaxstat twice daily for four (n=5) or eight weeks (n=16). Myocardial energetics (phosphocreatine to adenosine triphosphate ratio, PCr/ATP), metabolism and function were assessed pre-& post-treatment using magnetic resonance imaging (MRI), 31P- and 1H-MR spectroscopy (MRS). We utilised hyperpolarized [1-13C]pyruvate MRS to assess in-vivo PDH-flux (n=9) and plasma metabolomics and proteomics to assess whole body metabolism. ResultsPatients presented with impaired PCr/ATP, (median 1.6 [IQR 1.4, 2.1]), myocardial steatosis (2.2 % [IQR 1.5, 3.2]) and LV diastolic dysfunction (peak circumferential diastolic strain rate 0.86/s [IQR 0.82, 1.06]) at baseline. Ninerafaxstat treatment improved myocardial energetics by 32% (p<0.01), reduced myocardial triglyceride content by 34% (p=0.03) and showed a trend towards improved PDH-flux (mean 45% increase, p=0.08). Diastolic function was significantly improved post-treatment (peak diastolic strain rate by 10%, peak LV filling rate by 11%, both p<0.05). ConclusionsMetabolic modulation with ninerafaxstat significantly improved myocardial energetics, reduced myocardial steatosis and improved LV diastolic filling. Combining hyperpolarized MRS and metabolomics, is a powerful approach to examine the mechanism of action of novel metabolic modulators. REGISTRATIONURL: https://clinicaltrials.gov; Unique identifier: NCT04826159 O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=121 SRC="FIGDIR/small/591019v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@86fae1org.highwire.dtl.DTLVardef@1c1037eorg.highwire.dtl.DTLVardef@cc5ca9org.highwire.dtl.DTLVardef@d789d1_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2024

A bispecific antibody-drug conjugate targeting pCAD and CDH17 has antitumor activity and improved tumor specificity

P-cadherin (pCAD) and LI-cadherin (CDH17) are cell surface proteins belonging to the cadherin superfamily that are both highly expressed in colorectal cancer. This co-expression profile presents a novel and attractive opportunity for a dual targeting approach using an antibody-drug conjugate (ADC). In this study, we used a unique avidity-driven in vitro screening approach to generate pCAD x CDH17 bispecific antibodies that selectively targets cells expressing both antigens over cells expressing only pCAD or only CDH17. Based off the in vitro results we selected a lead bispecific antibody to link to the cytotoxic payload MMAE to generate a pCAD x CDH17 bispecific MMAE ADC. In in vivo dual flank mouse models, we demonstrated antitumor activity of the bispecific ADC in tumors expressing both antigens, but not in tumors expressing only pCAD or only CDH17. Overall, the preclinical data presented here suggests that a pCAD x CDH17 bispecific MMAE ADC has the potential to provide clinical benefit to colorectal cancer patients.

cancer biology↗

bioRxiv2024

NSm is a critical determinant for bunyavirus transmission between vertebrate and arthropod hosts

Bunyavirales is a very large order including viruses infecting a variety of taxonomic groups such as arthropods, vertebrates, plants, and protozoan. Some bunyaviruses are transmitted between vertebrate hosts by blood-sucking arthropods and cause major diseases in humans and animals. It is not understood why only some bunyaviruses have evolved the capacity to be transmitted by arthropod vectors. Here we show that only vector-borne bunyaviruses express a non-structural protein, NSm, whose function has so far remained largely elusive. Using as experimental system Bunyamwera virus (BUNV) and its invertebrate host, Aedes aegypti, we show that NSm is dispensable for viral replication in mosquito cells in vitro but is absolutely required for successful infection in the female mosquito following a blood meal. More specifically, NSm is required for cell-to-cell spread and egress from the mosquito midgut, a known barrier to viral infection. Notably, the requirement for NSm is specific to the midgut; bypassing this barrier by experimental intrathoracic infection of the mosquito eliminates the necessity of NSm for virus spread in other tissues, including the salivary glands. Overall, we unveiled a key evolutionary process that allows the transmission of vector-borne bunyaviruses between arthropod and vertebrate hosts.

microbiology↗

bioRxiv2024

MGPfactXMBD: A Model-Based Factorization Method for scRNA Data Unveils Bifurcating Transcriptional Modules Underlying Cell Fate Determination

Manifold-learning is particularly useful to resolve the complex cellular state space from single-cell RNA sequences. While current manifold-learning methods provide insights into cell fate by inferring graph-based trajectory at cell level, challenges remain to retrieve interpretable biology underlying the diverse cellular states. Here, we described MGPfactXMBD, a model-based manifold-learning framework and capable to factorize complex development trajectories into independent bifurcation processes of gene sets, and thus enables trajectory inference based on relevant features. MGPfactXMBD offers more nuanced understanding of the biological processes underlying cellular trajectories with potential determinants. When bench-tested across 239 datasets, MGPfactXMBD showed advantages in major quantity-control metrics, such as branch division accuracy and trajectory topology, outperforming most established methods. In real datasets, MGPfactXMBD recovered the critical pathways and cell types in microglia development with experimentally valid regulons and markers. Furthermore, MGPfactXMBD discovered evolutionary trajectories of tumor-associated CD8+ T cells and yielded new subtypes of CD8+ T cells with gene expression signatures significantly predictive of the responses to immune checkpoint inhibitor in independent cohorts. In summary, MGPfactXMBD offers a manifold-learning framework in scRNA-seq data which enables feature selection for specific biological processes and contributing to advance our understanding of biological determination of cell fate.

bioinformatics↗

bioRxiv2024

Protocatechuic acid induces endogenous oxidative stress in CR-hvKP by regulating the EMP-PPP pathway

BackgroundKlebsiella pneumoniae is an important opportunistic pathogen and zoonotic pathogen. The widespread use of antibiotics has led to the emergence of a large number of multidrug-resistant Klebsiella pneumoniae in clinical animal husbandry, posing a serious threat to global health security. Protocatechuic acid (PCA) is a phenolic acid substance naturally present in many vegetables and fruits. It is a safe and highly developed new type of antibacterial synergist. PurposeThis study explored the antibacterial and synergistic mechanisms of PCA against Carbapenem-resistant hypervirulent Klebsiella pneumoniae. Study designMetabolomic analysis using PCA to investigate the metabolic effects of CR-hvKP and further explore the antibacterial mechanisms resulting from this metabolic regulation. MethodsThe MIC of PCA was measured by microdilution, and its bactericidal effect was observed by DAPI staining. Resistance and hemolysis tests were performed to ensure safety. The synergy of PCA and meropenem was tested by checkerboard assay. The biofilm inhibition was assessed by crystal violet and EPS assays. The membrane morphology, permeability, and potential were examined by SEM, PI, NPN, and DiSC3(5). The metabolic changes were evaluated by AlamarBlue, metabolomics, enzyme activity, ELISA, molecular docking, and qRT-PCR. The oxidative stress and metabolic disorders were verified by NADP(H), ROS, MDA, and ATP assays. ResultsThe results showed that PCA can synergize with antibiotics and inhibit the biofilm and membrane functions of CR-hvKP at low concentrations. Metabolomics revealed that PCA affects the EMP and PPP pathways of CR-hvKP, causing oxidative stress. This involves the binding of PGAM and the downregulation of BPGM, leading to the accumulation of glycerate-3P. This results in the inhibition of G6PDH and the imbalance of NADPH/NADP+, disrupting the energy metabolism and increasing the oxidative stress, which impair the biofilm and membrane functions and enhance the antibiotic efficacy. ConclusionThe results demonstrate that PCA regulates the EMP-linked PPP pathway of CR-hvKP, inhibits biofilm and membrane functions, and synergizes with antibiotics to kill bacteria, providing new insights and candidates for natural antibacterial enhancers. Author SummaryKlebsiella pneumoniae is a common pathogenic bacterium that can infect both humans and animals, causing serious diseases such as pneumonia, meningitis, and sepsis. Due to the overuse of antibiotics, this bacterium has developed resistance to many drugs, posing a significant threat to global health security. Through our research, we have discovered a natural substance called protocatechuic acid (PCA) that can enhance the effectiveness of antibiotics against this bacterium. PCA is found in many vegetables and fruits and is a safe and non-toxic antibacterial adjuvant. Our analysis of the metabolomics of PCA on Klebsiella pneumoniae has revealed its antibacterial and synergistic mechanisms. The study found that PCA can affect the bacteriums sugar metabolism pathway, leading to the generation of endogenous oxidative stress. This disrupts their energy metabolism, damages their cell membranes and biofilms, making them more susceptible to being killed by antibiotics. Through this mechanism, PCA can synergize with common antibiotics such as meropenem, enhancing their bactericidal ability. Our research has demonstrated that PCA is an effective antibacterial adjuvant, providing new candidates and insights for the development of natural antibacterial agents. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=104 SRC="FIGDIR/small/583678v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@2e2963org.highwire.dtl.DTLVardef@9f3c51org.highwire.dtl.DTLVardef@3125a8org.highwire.dtl.DTLVardef@9f39b7_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2024

The assembly and efflux processes revealed by in situ structures of the ABC-type tripartite pump MacAB-TolC

The MacAB-TolC tripartite efflux pump is widely distributed in Gram-negative bacteria, extruding antibiotics and virulence factors that lead to multidrug resistance and pathogenicity. This pump spans the cell envelope through its three components, an inner membrane ATP-binding cassette (ABC) transporter MacB, a periplasmic adaptor protein MacA, and an outer membrane protein TolC. However, the assembly process and efflux mechanism of the MacAB-TolC in cells remain unclear. Here, we resolve the in situ structures of Escherichia coli (E. coli) MacAB-TolC efflux pump by electron cryo-tomography and subtomogram averaging. In E. coli without antibiotic treatment, we observe a fully assembled MacAB-TolC pump with a weak constriction density in the middle of the MacA region. When E. coli cells were treated with erythromycin, we discovered the emergence of MacA-TolC subcomplexes, indicating flexible binding of MacB in the presence of an antibiotic substrate. This finding was further validated by in vivo crosslinking results. Together, our data present the in situ assembly process of the MacAB-TolC and derive a substrate-driven working model for ABC-type tripartite pump.

microbiology↗

bioRxiv2024

UBA1-CDK16: A Sex-Specific Chimeric RNA and Its Role in Immune Sexual Dimorphism

RNA processing mechanisms, such as alternative splicing and RNA editing, have been recognized as critical means to expand the transcriptome. Chimeric RNAs formed by intergenic splicing provide another potential layer of RNA diversification. By analyzing a large set of RNA-Seq data and validating results in over 1,200 blood samples, we identified UBA1-CDK16, a female-specific chimeric transcript. Intriguingly, both parental genes, are expressed in males and females. Mechanistically, UBA1-CDK16 is produced by cis-splicing between the two adjacent X-linked genes, originating from the inactive X chromosome. A female-specific chromatin loop, formed between the junction sites, facilitates the alternative splicing of its readthrough precursor. This unique chimeric transcript exhibits evolutionary conservation, evolving to be female-specific from non-human primates to humans. Furthermore, our investigation reveals that UBA1-CDK16 is enriched in the myeloid lineage and plays a regulatory role in myeloid differentiation. Notably, female COVID-19 patients who tested negative for this chimeric transcript displayed higher counts of neutrophils, highlighting its potential role in disease pathogenesis. These findings support the notion that chimeric RNAs represent a new repertoire of transcripts that can be regulated independently from the parental genes, and a new class of RNA variance with potential implications in sexual dimorphism and immune responses.

genomics↗

bioRxiv2024

Distinct Effects of Aducanumab and Lecanemab on Intraneuronal Endogenous Aβ42 and Phosphorylated Tau in Alzheimer's Disease Treatment

In the treatment of Alzheimers Disease (AD), two FDA-approved monoclonal antibodies, Aducanumab (Adu) and Lecanemab (LCN), exhibit significant differences in clinical benefits. By utilizing human-induced basal forebrain cholinergic neurons (BFCNs) derived from AD patient skin fibroblasts, we successfully recapitulated the natural endogenous neuropathologies of A{beta}42 and Tau within just 21 days and revealed distinct intraneuronal effects of Adu and LCN. Both antibodies are internalized into BFCNs and localize with cytosolic A{beta}42. However, LCN, selectively targeting A{beta}42 oligomers and protofibrils, triggers TRIM21 pathway and significantly enhances autolysosome- and proteasome-mediated A{beta}42 clearance, thereby leading to a marked reduction in phosphorylated Tau181 (pTau181) pathology. In contrast, the fibrillized A{beta}42-selective Adu shows considerably weaker effects. This study not only reveals the unique intraneuronal actions of Adu and LCN but also provides a reliable and accessible human neuronal model for evaluating potential AD therapeutics, emphasizing the importance of intraneuronal pathology in the treatment of AD.

neuroscience↗

bioRxiv2024

Development of immobilized antibody-based affinity grid strategy and application in on-grid purification of target proteins for high-resolution cryo-EM

In cryo-electron microscopy (cryo-EM), sample preparation, especially for rare or fragile macromolecular assemblies and those suffering from air-water interface denaturation and particle orientation distribution problems, is a major bottleneck. Here, we developed and characterized an immobilized antibody-based affinity grid (IAAG) strategy based on the high-affinity PA tag/NZ-1 antibody epitope tag system. We used Pyr-NHS as a linker to immobilize NZ-1 Fab on the graphene oxide or carbon covered grid surface. We showed that the IAAG grid can enrich the PA-tagged target proteins, and overcome preferred orientation problems. Furthermore, we demonstrated that our IAAG strategy can be utilized for on-grid purification of low-abundance target complexes from cell lysates and enables atomic resolution cryo-EM. This approach greatly streamlines the purification process, reduces the need for large quantities of biological samples, and addresses common challenges encountered in cryo-EM sample preparation. Collectively, our IAAG strategy provides an efficient and robust means for combined sample purification and vitrification feasible for high-resolution cryo-EM. This approach also has the potential for broader applicability in cryo-EM and cryo-ET.

molecular biology↗

bioRxiv2024

Mitochondrial choline import regulates purine nucleotide pools via SLC25A48

Choline is an essential nutrient for cellular metabolism, including the biosynthesis of phospholipids, neurotransmitters, and one-carbon metabolism. A critical step of choline catabolism is the mitochondrial import and synthesis of chorine-derived methyl donors, such as betaine. However, the underlying mechanisms and the biological significance of mitochondrial choline catabolism remain insufficiently understood. Here, we report that a mitochondrial inner-membrane protein SLC25A48 controls mitochondrial choline transport and catabolism in vivo. We demonstrate that SLC25A48 is highly expressed in brown adipose tissue and required for whole-body cold tolerance, thermogenesis, and mitochondrial respiration. Mechanistically, choline uptake into the mitochondrial matrix via SLC25A48 facilitates betaine synthesis and one-carbon metabolism. Importantly, cells lacking SLC25A48 exhibited reduced synthesis of purine nucleotides and failed to initiate the G1-to-S phase transition, thereby leading to cell death. Taken together, the present study identified SLC25A48 as a mitochondrial carrier that mediates choline import and plays a critical role in mitochondrial respiratory capacity, purine nucleotide synthesis, and cell survival. Key pointsO_LISLC25A48 is required for mitochondrial choline uptake. C_LIO_LIMitochondrial choline uptake regulates one-carbon contribution to purine nucleotide synthesis. C_LIO_LIBrown fat thermogenesis requires mitochondrial choline catabolism for respiratory capacity. C_LIO_LICancer cells require mitochondrial choline uptake for cell survival. C_LI

cell biology↗

bioRxiv2023

An Efficient and Safe Trans-complementation System of Mpox Virus Reproduces Authentic Viral Architecture and Infection

Since the Mpox virus (MPXV) outbreak in 2022, there have been 97,745 cases and 203 fatalities. This outbreak features increased transmission efficiency and a higher infection rate in the MSM population, with the underlying causes remaining unknown. The requirement of BSL-3 laboratories poses a barrier to MPXV research and antiviral development. Here, we report an efficient and safe trans-complementary system that produces a single-round infectious MPXV, preserving the viruss authentic architecture and enabling it to complete its life cycle in complementing cells. This deficient MPXV genome, lacking two essential genes crucial for late gene transcription and viral assembly, is restricted to a single-round infection in non-complementing cell lines. Notably, SCID mice inoculated with this deficient MPXV exhibited no detectable disease or viral load. This deficient MPXV platform has demonstrated its capacity to study innate immunity and cell death during infection in complementing cells. It can also be used for antibody neutralization assays and anti-MPXV drug evaluation. This trans-complementation platform, safe for use in low-biosafety laboratories, offers a valuable resource for MPXV research and countermeasure development.

microbiology↗

bioRxiv2023

Melon: metagenomic long-read-based taxonomic identification and quantification using marker genes

Long-read sequencing holds great potential for characterizing complex microbial communities, yet taxonomic profiling tools designed specifically for long reads remain lacking. Here we introduce Melon, a novel marker-based taxonomic profiler that capitalizes on the unique attributes of long reads. Melon employs a two-stage classification scheme to reduce computational time and is equipped with an expectation-maximization-based post-correction module to handle ambiguous reads. Melon achieves superior performance compared to other existing tools in both mock and simulated samples. Using wastewater metagenomic samples, we demonstrate the applicability of Melon by showing it is capable in providing reliable estimates of overall genome copies, and species-level taxonomic profiles.

bioinformatics↗

bioRxiv2023

Structural and mechanistic views of enzymatic, heme-dependent nitrogen-nitrogen bond formation

Molecules with nitrogen-nitrogen (N-N) bonds constitute a large group of clinically important drugs, and various synthetic approaches have been developed to construct functional groups like hydrazines, diazos, pyrazoles, and N-nitrosos. While hundreds of N-N-containing specialized natural metabolites have also been discovered, little is known about the underlying enzymatic mechanisms that have evolved for N-N bond formation. In order to directly form a single N(sp3)-N(sp3) bond, enzymes must reverse the typical nucleophilicity of one nitrogen. Here, we report structural and mechanistic interrogations of the piperazate synthase PipS, a heme-dependent enzyme that catalyzes an N-N bond forming cyclization of N5-OH-L-ornithine to give the non-proteinogenic amino acid L-piperazic acid. We show that PipS can process a variety of N-substituted hydroxylamines, to give either an imine or an N-N bond, in a substrate-specific manner. Using a combination of structural and biochemical experiments, computational studies, and spectroscopic characterization, we propose that heme-dependent dehydration and N-N bond formation in PipS proceed through divergent pathways, which may stem from a shared nitrenoid intermediate that effectively reverses the nucleophilicity of the hydroxylamine nitrogen. Our work expands the current knowledge of enzymatic N-N bond formation, and delineates the catalytic versatility of a heme cofactor, paving the way for future development of genetically encoded biocatalysts for N-N bond formation.

biochemistry↗

bioRxiv2023

Spatially resolved molecular and cellular atlas of the mouse brain

A comprehensive atlas of genes, cell types, and their spatial distribution across a whole mammalian brain is fundamental for understanding function of the brain. Here, using snRNA-seq and Stereo-seq techniques, we generated a mouse brain atlas with spatial information for 308 cell clusters with single-cell resolution involving over 6 million cells as well as for 29,655 genes. We have identified new astrocyte clusters, and demonstrated that distinct cell clusters exhibit preference for cortical subregions. In addition, we identified 155 genes exhibiting regional specificity in the brainstem, and 513 long non-coding RNA exhibited regional specificity in the adult brain. Parcellation of brain regions based on spatial transcriptomic information showed large overlap with that by traditional method. Furthermore, we have uncovered 411 transcription factor regulons with spatiotemporal specificity during development. Thus, our study has discovered genes and regulon with spatiotemporal specificity, and provided a high-resolution spatial transcriptomic atlas of the mouse brain.

neuroscience↗

bioRxiv2023

The ventral hippocampus and nucleus accumbens as neural substrates for cocaine contextual memory reconsolidation

Drug craving triggered by cues that were once associated with drug intoxication is a major contributor to continued drug-seeking behaviors. Addictive drugs engage molecular pathways of associative learning and memory. Reactivated memories are vulnerable to disruption by interference with the process of reconsolidation, hence targeting reconsolidation could be a strategy to reduce cue-induced drug craving and relapse. Here we examined the circuitry of cocaine contextual memory reconsolidation and explored neuroplasticity following memory reactivation. Mice underwent chemogenetic inhibition of either nucleus accumbens (NA) neurons or the glutamatergic projection neurons from the ventral hippocampus (vHPC) to NA using inhibitory designer receptors exclusively activated by designer drugs (iDREADD). Mice underwent cocaine conditioned place preference followed by reactivation of the cocaine contextual memory. Clozapine-N-oxide (CNO) was administered after memory reactivation to inhibit either NA neurons or the accumbens-projecting vHPC neurons during the reconsolidation period. When retested 3 days later, a significant reduction in the previously established preference for the cocaine context was found in both conditions. FosTRAP2-Ai14 mice were used to identify neurons activated by cocaine memory recall and to evaluate plasticity in NA medium spiny neurons (MSNs) and vHPC pyramidal neurons upon recall of cocaine memories. Results indicate a significant increase in dendritic spine density in NA MSNs activated by cocaine memory recall, particularly of the thin spine type. Sholl analysis indicated longer dendritic length and more branching of NA MSNs after cocaine memory recall than without memory reactivation. vHPC neurons showed increased spine density, with the most robust change in stubby spines. These results implicate a circuit involving glutamatergic projections from the vHPC onto NA neurons which is necessary for the reconsolidation of cocaine memories. Interruption of cocaine memory reconsolidation reduced drug-seeking behavior.

neuroscience↗

bioRxiv2023

Proximity Labeling Expansion Microscopy (PL-ExM) resolves structure of the interactome

Elucidating the spatial relationships within the protein interactome is pivotal to understanding the organization and regulation of protein-protein interactions. However, capturing the 3D architecture of the interactome presents a dual challenge: precise interactome labeling and super-resolution imaging. To bridge this gap, we present the Proximity Labeling Expansion Microscopy (PL-ExM). This innovation combines proximity labeling (PL) to spatially biotinylate interacting proteins with expansion microscopy (ExM) to increase imaging resolution by physically enlarging cells. PL-ExM unveils intricate details of the 3D interactomes spatial layout in cells using standard microscopes, including confocal and Airyscan. Multiplexing PL-ExM imaging was achieved by pairing the PL with immunofluorescence staining. These multicolor images directly visualize how interactome structures position specific proteins in the protein-protein interaction network. Furthermore, PL-ExM stands out as an assessment method to gauge the labeling radius and efficiency of different PL techniques. The accuracy of PL-ExM is validated by our proteomic results from PL mass spectrometry. Thus, PL-ExM is an accessible solution for 3D mapping of the interactome structure and an accurate tool to access PL quality.

bioengineering↗

bioRxiv2023

Dual regulation of SLC25A39 by AFG3L2 and iron controls mitochondrial glutathione homeostasis

Organelle transporters define metabolic compartmentalization and how this metabolite transport process can be modulated is poorly explored. Here, we discovered that SLC25A39, a mitochondrial transporter critical for mitochondrial glutathione uptake, is a short-lived protein under dual regulation at the protein level. Co-immunoprecipitation mass spectrometry and CRISPR KO in cells identified that mitochondrial m-AAA protease AFG3L2 is responsible for degrading SLC25A39 through the matrix loop 1. SLC25A39 senses mitochondrial iron-sulfur cluster using four matrix cysteine residues and inhibits its degradation. SLC25A39 protein regulation is robust in developing and mature neurons. This dual transporter regulation, by protein quality control and metabolic sensing, allows modulating mitochondrial glutathione level in response to iron homeostasis, opening new avenues to explore regulation of metabolic compartmentalization. Neuronal SLC25A39 regulation connects mitochondrial protein quality control, glutathione and iron homeostasis, which were previously unrelated biochemical features in neurodegeneration.

cell biology↗

bioRxiv2023

Lac-Phe mediates the anti-obesity effect of metformin

Metformin is a widely prescribed anti-diabetic medicine that also reduces body weight. The mechanisms that mediate metformins effects on energy balance remain incompletely defined. Here we show that metformin is a powerful pharmacological inducer of the anorexigenic metabolite Lac-Phe in mice as well as in two independent human cohorts. In cell culture, metformin drives Lac-Phe biosynthesis via inhibition of complex I, increased glycolytic flux, and intracellular lactate mass action. Other biguanides and structurally distinct inhibitors of oxidative phosphorylation also increase Lac-Phe levels in vitro. Genetic ablation of CNDP2, the principal biosynthetic enzyme for Lac-Phe, in mice renders animals resistant to metformins anorexigenic and anti-obesity effects. Mediation analyses also support a role for Lac-Phe in metformins effect on body mass index in humans. These data establish the CNDP2/Lac-Phe pathway as a critical mediator of the effects of metformin on energy balance.

physiology↗