Biology subjects

Xia, Y.

Publications and source records attributed to Xia, Y..

At least 73 records · Page 4Linked to original sources

bioRxiv2025

Clarifying the priming requirement and activator specificity for the NLRP3 inflammasome in human keratinocytes in vitro

While NLRP3 has been extensively studied in myeloid cells, its existence and regulation in epithelial cells, including keratinocytes, are unclear. In fact, whether human keratinocytes express a functional NLRP3 inflammasome at all remains a matter of debate in the inflammasome field. Here, we provide additional evidence that NLRP3 is repressed in human keratinocytes cultured under non-inflammatory conditions but can be sharply induced by interferon-{gamma} (IFN{gamma})--but not lipopolysaccharide (LPS). In this IFN{gamma}-primed state, not all established NLRP3 activators are specific to NLRP3. We report that nigericin-driven keratinocyte pyroptosis occurs via both NLRP1 and NLRP3, whereas Staphylococcus aureus -hemolysin (Hla) exclusively and nonredundantly activates NLRP3, even though both require K+ efflux. Furthermore, in the presence of T cells, certain virulent S. aureus strains can cause NLRP3-dependent pyroptotic death in keratinocytes in vitro through the cooperative actions of superantigens (SAgs) and Hla. In summary, our findings establish the strict inducibility and functional relevance of the NLRP3 inflammasome in non-myeloid, epithelial cells in vitro. These results resolve conflicting reports and position keratinocytes as a context-specific, non-hematopoietic cellular model for studying NLRP3 activation in host-microbe interactions at barrier tissues. KEY FINDINGSO_LIAdditional evidence that NLRP3 is absent in resting, nonstimulated human keratinocytes in vitro C_LIO_LIIFN{gamma}, but not LPS, is a potent priming signal for NLRP3 in human keratinocytes in vitro C_LIO_LIIn IFN{gamma}-primed keratinocytes, S. aureus -hemolysin (Hla) selectively activates NLRP3, whereas nigericin activates both NLRP1 and NLRP3 in vitro C_LIO_LISAg and Hla kill keratinocytes via NLRP3-driven pyroptosis in the presence of T cells in vitro C_LI GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=156 SRC="FIGDIR/small/669639v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@4996f4org.highwire.dtl.DTLVardef@155a2a9org.highwire.dtl.DTLVardef@12a21a0org.highwire.dtl.DTLVardef@105bc15_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2025

Rationally Engineered Coronavirus-mimicking Protein Nanocage Platform for Glioblastoma Targeted Delivery and Immunity Regulation

Glioblastoma (GBM) is one of the most aggressive and treatment-resistant brain tumors, owing to the dual challenges of the blood-brain barrier (BBB) and a profoundly immunosuppressive tumor microenvironment. However, few existing strategies are capable of simultaneously overcoming these two barriers, underscoring a critical scientific gap and the need for innovative therapeutic platforms that enable both effective BBB traversal and tumor immune reprogramming. Here, we present a coronavirus-mimicking protein nanocage platform (EcomPC) derived from Thermotoga maritima encapsulin, rationally engineered for the targeted and sustained delivery of interferon- (IFN-) to GBM lesions. Through strategic insertion of flexible linkers, cysteine-to-serine mutations, and modular surface functionalization via SpyTag/SpyCatcher chemistry, EcomPC enables intracellular self-assembly of IFN- and glioma-specific targeting. In orthotopic GBM models, EcomPC-IFN demonstrates efficient BBB translocation, selective tumor accumulation, and potent anti-tumor efficacy. Mechanistically, localized IFN- release induces tumor cell apoptosis and reprograms the immune microenvironment--characterized by increased CD8 T cell infiltration, decreased Foxp3 regulatory T cells, and a favorable chemokine shift. These therapeutic effects are not recapitulated by free IFN- or untargeted nanocages, underscoring the essential role of both structural mimicry and ligand-guided delivery. Collectively, this work establishes EcomPC as a programmable, virus-inspired protein delivery platform capable of overcoming key physiological barriers in brain tumor immunotherapy, and lays the foundation for its broader application in CNS-targeted biologic delivery.

bioengineering↗

bioRxiv2025

Phosphoglycerate Kinase Can Adopt a Topologically Misfolded Form that is More Stable than its Native State

The native states of globular proteins are typically viewed as being the most stable conformations on their respective proteins soluble free energy landscapes. This view, known as the Thermodynamic Hypothesis, explains why many proteins can reversibly refold after being denatured. Here we report an intriguing counterexample to this paradigm. When E. coli phosphoglycerate kinase (PGK) is stimulated to refold upon dilution from denaturant, instead of returning to its native state, it populates an unusual misfolded form that is monomeric and native-like, but which is even more kinetically stable than its native form, as based on its resistance to thermal and detergent-induced denaturation. Moreover, this misfolded form cannot self-correct, even for days. We show that the key structural feature of this misfolded form of PGK is topological in nature by demonstrating that kinetically stable misfolded forms do not form any longer if PGK is circularized, which prevents its termini from threading through other portions of the protein. Our findings demonstrate that a misfolded protein need not aggregate or form an amyloid to become stabilized with respect to the native state, and call attention to topologically-misfolded proteins as a potential Achilles heel to the cellular proteostasis network.

biophysics↗

bioRxiv2025

BiGER: Bayesian Rank Aggregation in Genomics with Extended Ranking Schemes

With the rise of large-scale genomic studies, large gene lists targeting important diseases are increasingly common. While evaluating each study individually gives valuable insights on specific samples and study designs, the wealth of available evidence in the literature calls for robust and efficient meta-analytic methods. Crucially, the diverse assumptions and experimental protocols underlying different studies require a flexible but rigorous method for aggregation. To address these issues, we propose BiGER, a fast and accurate Bayesian rank aggregation method for the inference of latent global rankings. Unlike existing methods in the field, BiGER accommodates mixed gene lists with top-ranked and top-unranked genes as well as bottom-tied and missing genes, by design. Using a Bayesian hierarchical framework combined with variational inference, BiGER efficiently aggregates large-scale gene lists with high accuracy, while providing valuable insights into source-specific reliability for researchers. Through both simulated and real datasets, we show that BiGER is a useful tool for reliable meta-analysis in genomic studies.

genomics↗

bioRxiv2025

Complex I Governs Iron Levels in Bat Mitochondria to Couple Respiration with Lipid Metabolism

The evolution of mitochondrial respiration has been implicated in the remarkable adaptations of bats, including powered flight, longevity and viral tolerance. However, the mechanisms coordinating mitochondrial respiration with lipid metabolism--a critical energy source for flight--remain poorly understood. Here, we discovered that complex I inhibition triggered iron overload into bat mitochondria, inducing a burst of reactive oxygen species (ROS). This iron translocation relied on the VDAC-MCU axis and mitochondrial membrane potential. Intriguingly, disrupting VDAC oligomerization enhanced iron uptake in a complex I-dependent manner. Mitochondrial iron translocation perturbed fatty acid oxidation and upregulated linoleic acid species, which promoted the reversible accumulation of lipid droplets, suggesting metabolic plasticity crucial for bat energetics. Our findings establish complex I as a pivotal regulatory hub that directly couples respiratory efficiency to lipid metabolism by governing mitochondrial iron levels. This mechanism may represent a key evolutionary adaptation supporting the unique metabolic demands of bat physiology. HIGHLIGHTSComplex I inhibition induces unique mitochondrial ROS burst in bat cells. Mitochondrial iron overload is the primary trigger of complex I-linked ROS burst. VDAC-MCU axis couples membrane potential to drive mitochondrial iron influx. Mitochondrial iron translocation remodels lipid metabolism in bat cells.

cell biology↗

bioRxiv2025

Imaging CRISPR-Edited CAR-T Cell Therapies with Optical and Positron Emission Tomography Reporters

RationaleChimeric antigen receptor (CAR) T cell therapies have shown remarkable success in treating hematological cancers and are increasingly demonstrating potential for solid tumors. CRISPR-based genome editing offers a promising approach to enhance the potency and safety of CAR-T cells. However, several challenges persist, including inefficient tumor homing and treatment-related toxicities in normal tissues, which continue to hinder widespread adoption. Advanced imaging technologies, including bioluminescence imaging (BLI) and positron emission tomography (PET), provide real-time insights into CAR-T cell distribution and activity in vivo, both in preclinical models and in patients. Here, we developed Trackable Reporter Adaptable CRISPR-Edited CAR (tRACE-CAR) T cells, a modular system for site-specific integration of CARs and imaging reporters. MethodsThe luciferase reporter AkaLuciferase (AkaLuc) or the human sodium iodide symporter (NIS) were cloned downstream of the CAR in adeno-associated virus (AAV) donors for BLI or PET tracking, respectively. CARs with imaging reporters were knocked into the TRAC locus of primary human T cells via CRISPR editing and AAV transduction. Editing efficiency was evaluated by flow cytometry and junction PCR. In vitro cytotoxicity was assessed by BLI using firefly luciferase (Fluc)-expressing cancer cells co-cultured with CAR-T cells at varying effector-to-target ratios. In vivo, BLI and PET imaging assessed CAR-AkaLuc and CAR-NIS T cell expansion and trafficking in Nod-SCID-gamma mice bearing xenograft tumors. ResultsT cell receptor (TCR) knockout efficiency exceeded 85%, with CAR expression observed in 70-80% of cells, depending on the reporter used. Reporter-engineered CAR-T cells retained functionality in vitro and exhibited significant cytotoxicity against target cancer cells, outperforming naive T cells. In vivo, AkaLuc BLI and 18F-tetrafluoroborate PET enabled non-invasive tracking of viable CAR-T cells. Notably, the route of administration (intravenous, peritumoral, or intraperitoneal) significantly influenced the distribution of CAR-T cells and their therapeutic effectiveness. ConclusiontRACE-CAR enabled precise optical and PET tracking of CAR-T cells in models of B cell leukemia and ovarian cancer, allowing dynamic, non-invasive monitoring of cell distribution in both tumors and off-target tissues. This imaging platform could lead to more personalized, effective CRISPR-edited CAR cell therapies.

immunology↗

bioRxiv2025

Features fusion or not: harnessing multiple pathological foundation models using Meta-Encoder for downstream tasks fine-tuning

The emergence of diverse pathological foundation models has empowered computational pathology tasks, including tumor classification, biomarker prediction, and RNA expression prediction. However, variations in model architecture and data sources lead to inconsistent downstream performance and complicate centralized training. Specifically, the lack of data sharing makes retraining foundation models with pooled data infeasible. Alternatively, the release of model parameters enables combining multiple models during fine-tuning. Inspired by the meta-analysis method, we propose the Meta-Encoder framework, which integrates features from multiple foundation models to generate a comprehensive representation, improving downstream fine-tuning task performance. Comparative experiments demonstrate that Meta-Encoder is more effective than individual foundation models, with its strengths more pronounced in handling complex tasks. While single models may perform sufficiently well for simple tasks, Meta-Encoder can match or even surpass the best-performing single model, alleviating concerns over model selection. Moderately challenging tasks benefit from Meta-Encoders concatenation or self-attention strategies, with the latter demonstrating superior performance in more challenging scenarios. For highly complex tasks, such as high-dimensional gene expression prediction, self-attention proves to be the most effective Meta-Encoder strategy, balancing feature integration and computational efficiency. For three patch-level spatial gene expression prediction tasks (HEST-Benchmark, CRC-inhouse, and Her2ST), the self-attention strategy improved the Pearson correlation by 38.58%, 26.06%, and 20.39%, respectively, compared to the average performance of three patch-level single models. Similarly, for the TCGA-BRCA, TCGA-NSCLC, and TCGA-CRC WSI-level bulk gene expression prediction tasks, the Pearson correlation increased by 14.36%, 9.27%, and 42.55%, respectively, compared to the average performance of two WSI-level single models. By leveraging multiple pathological foundation models using Meta-Encoder, it can further improve molecular characterization in pathology images to advance precision oncology.

bioinformatics↗

bioRxiv2025

Caffeine Impairs Red Blood Cell Storage Quality by Dual Inhibition of ADORA2b Signaling and G6PD Activity

Caffeine is the most widely consumed psychoactive substance globally, yet its peripheral physiological effects remain incompletely understood. Leveraging comprehensive data from 13,091 blood donors in the REDS RBC-Omics study, we identify caffeine as a significant modulator of red blood cell (RBC) storage quality and transfusion outcomes. Elevated caffeine levels were reproducible across multiple donations from 643 recalled donors, selected based on their extremes in hemolytic propensity. Both in the screening and recalled cohorts, higher caffeine levels were associated with disrupted RBC metabolism, characterized by reduced glycolysis, depletion of adenylate pools or 2,3-bisphosphoglycerate, and increased markers of oxidative stress and osmotic fragility, including kynurenine accumulation. These observations were recapitulated in plasma and RBCs of eight volunteers upon consumption of a cup of coffee independently of brewing method (Chemex vs espresso). Clinically, elevated caffeine correlated with increased hemolysis and lower post-transfusion hemoglobin increments, especially pronounced in recipients transfused with RBCs from donors carrying common polymorphisms in the ADORA2b gene, a key regulator of RBC metabolism in hypoxia. These human findings were mechanistically validated using a murine model deficient in ADORA2b, which demonstrated impaired glycolytic flux, compromised antioxidant defenses - including caffeine-dependent direct inhibition of recombinantly-expressed glucose 6-phosphate dehydrogenase, and decreased transfusion efficacy (lower hemoglobin increments, higher bilirubin post-transfusion), effects further exacerbated by caffeine exposure during storage. Our study positions caffeine consumption as a modifiable factor in blood transfusion practice, advocating for precision strategies that integrate genetic and exposome factors, and identifies metabolic interventions to enhance blood quality and clinical outcomes. One sentence summaryCaffeine consumption and genetic variants in the ADORA2b receptor synergistically impair red blood cell metabolism and transfusion efficacy, revealing a modifiable exposome-gene interaction for precision transfusion medicine.

biochemistry↗

bioRxiv2025

Enhanced Kidney Targeting and Distribution of Tubuloids During Normothermic Perfusion

Tubuloids have become a promising tool for kidney disease model and regeneration, although their ability for integration and regeneration in vivo is not well documented. Here we establish, characterize and compare human tubuloids using two optimized protocols, which added a prior isolation of tubular cells (Crude tubuloids) and proximal tubular cells (F4 tubuloids). Secondly, using this protocol, healthy rat-derived tubuloids were established. Finally, we compared two strategies to deliver GFP tubuloids in a kidney host: 1) subcapsular/intracortical injection and 2) tubuloid infusion during normothermic preservation in a rat transplantation model and a human discarded kidney. F4 tubuloids achieved a more differentiation state compared to Crude tubuloids. When analyzing tubuloid delivery to the kidney, normothermic perfusion was more efficient compared to in vivo injection, observing fully-developed tubules in the host parenchyma after 1 week and 1 month. Normothermic perfusion also successfully delivered kidney tubuloids to a discarded human kidney for transplantation. These results suggest that tubuloids administered during normothermic perfusion represent a potential strategy to enhance the translatability of kidney regenerative therapies to the clinical practice to condition kidney grafts and to treat kidney diseases.

bioengineering↗

bioRxiv2025

High-accuracy protein complex structure modeling based on sequence-derived structure complementarity

In living organisms, proteins perform key functions required for life activities by interacting to form complexes. Determining the protein complex structure is crucial for understanding and mastering biological functions. Although AlphaFold2 has made a revolutionary breakthrough in predicting protein monomeric structures, accurately capturing inter-chain interaction signals and modeling the structures of protein complexes remain a formidable challenge. In this work, we report DeepSCFold, a pipeline for improving protein complex structure modeling. DeepSCFold uses sequence-based deep learning models to predict protein-protein structural similarity and interaction probability, providing a foundation for identifying interaction partners and constructing deep paired multiple-sequence alignments (MSAs) for protein complex structure prediction. Benchmark results show that DeepSCFold significantly increases the accuracy of protein complex structure prediction compared with state-of-the-art methods. For multimer targets from CASP15, DeepSCFold achieves an improvement of 11.6% and 10.3% in TM-score compared to AlphaFold-Multimer and AlphaFold3, respectively. Furthermore, when applied to antibody-antigen complexes from the SAbDab database, DeepSCFold enhances the prediction success rate for antibody-antigen binding interfaces by 24.7% and 12.4% over AlphaFold-Multimer and AlphaFold3, respectively. These results demonstrate that DeepSCFold effectively captures intrinsic and conserved protein-protein interaction patterns through sequence-derived structure-aware information, rather than relying solely on sequence-level co-evolutionary signals.

bioinformatics↗

bioRxiv2025

Measuring Longitudinal Genome-wide Clonal Evolution of Pediatric Acute Lymphoblastic Leukemia at Single-Cell Resolution

Approximately 15-20% of children with acute lymphoblastic leukemia (pALL) are not cured despite years of treatment with more than ten chemotherapeutic agents, yet bulk sequencing reveals minimal somatic variation that could explain genetic treatment resistance. Using error-corrected bulk sequencing, and primary template-directed amplification (PTA)-enabled single-cell exome and whole-genome sequencing, we discovered much more genetic diversity in pALL. Individual leukemic cells harbor 3.7-fold more mutations (mean 3,553) than detected in bulk samples (mean 965). Many ETV6-RUNX1 patients harbor multiple independent ras-mutated clones, and we also identified convergent evolution of JAK2 mutations as well as copy number alterations. PTA-based phylogenetic analysis of over 150 single-cell genomes linked heritable phenotypes to specific genetic alterations and identified low-frequency clones harboring mutations in treatment resistance-associated genes (ITGA9, NTRK3, SULF2) that increased in frequency during treatment. These findings reveal extensive hidden genetic diversity in pALL while providing a framework for the early detection of high-risk leukemic populations.

cancer biology↗

bioRxiv2025

Chimeric Collagen-like Proteins with Tunable Structural Heterogeneity for Precise Control and Targeted Doxorubicin Delivery

Protein-based drug delivery systems offer advantages such as genetic tunability, structural homogeneity, and high biocompatibility. However, precisely controlling the assembly of protein nanoparticles and establishing correlations between their macroscopic properties and molecular architecture remain significant challenges. Here, inspired by chimeric collagen-like proteins, we rationally designed a series of de novo chimeric proteins comprising an N-terminal globular domain fused to a linear collagen-like domain. These structurally heterogeneous proteins were conjugated with doxorubicin (DOX) and homogenized to form chimeric collagen-like protein-DOX nanocomplexes (CDCNs). By fine-tuning the protein structure and domain organization, we achieved precise control over CDCN architecture and drug release kinetics. Furthermore, to enhance tumor specificity, triple-negative breast cancer (TNBC)- and glioblastoma (GBM)-targeting peptides were genetically fused to the chimeric proteins, respectively. In both in vitro and in vivo models of TNBC and GBM, CDCNs facilitated selective tumor accumulation, enhanced cellular uptake, and promoted apoptosis while minimizing off-target toxicity. This work establishes a strategy for designing protein-based nanoplatforms with programmable structures and tunable functionalities, offering promising potential for precisely controlling of protein-based delivery system.

bioengineering↗

bioRxiv2025

Deciphering the molecular mechanisms of FET fusion oncoprotein-DNA hollow co-condensates

Biomolecules such as nucleic acids and proteins can undergo liquid-liquid phase separation to form biomolecular condensates with diverse architectures. However, fundamental questions surrounding the biophysical principles that govern condensate architecture and their potential biotechnological applications remain unresolved. Here, we report that the FUS/EWS/TAF15 family fusion oncoprotein FUS-ERG forms hollow co-condensates with double-stranded DNA containing GGAA microsatellites. Through a combination of biochemical assays, super-resolution imaging, and mathematical modeling, we reveal that the interior surface of hollow co-condensates exhibits properties distinct from those of the external surface, a phenomenon we term nested asymmetric phase separation. Furthermore, we demonstrate that the self-organization and morphology control of FUS-ERG hollow co-condensates can be harnessed for DNA-based information manipulation, enabling targeted DNA deletion within dsDNA libraries and facilitating dynamic, hierarchical data selection. These findings provide critical insights into the biophysical mechanisms underlying multicomponent phase-separated cellular bodies and establish a foundation for leveraging condensate morphology in biotechnology.

biophysics↗

bioRxiv2025

GerNA-Bind: Geometric-enhanced RNA-ligand Binding Specificity Prediction with Deep Learning

RNA molecules are essential regulators of biological processes and promising therapeutic targets for various diseases. Discovering small molecules that selectively bind to specific RNA conformations remains challenging due to RNAs structural complexity and the limited availability of high-resolution data. Herein, we introduce GerNA-Bind, a geometric deep learning framework to predict RNA-ligand binding specificity by integrating multi-state RNA-ligand representations and interactions. GerNA-Bind achieves state-of-the-art performance on multiple benchmark datasets and excels in predicting interactions for low-homology RNA-ligand pairs. It achieves a 20.8% improvement in precision for binding site prediction compared to AlphaFold3. Furthermore, it offers informative, well-calibrated predictions with built-in uncertainty quantification. In a large-scale virtual screening application, GerNA-Bind identified 18 structurally diverse compounds targeting the oncogenic MALAT1 RNA, with experimentally confirmed submicromolar affinities. Among them, one lead compound selectively binds the MALAT1 triple-helix, reduces its transcript levels, and inhibits cancer cell migration. These findings highlight GerNA-Binds potential as a powerful tool for RNA-focused drug discovery, offering both accuracy and biological insight.

bioinformatics↗

bioRxiv2025

miR-124 acts during Drosophila development to determine the phase of adult circadian behavior

Circadian behaviors need to be properly phased with the day/night cycle to be beneficial. We previously showed that the microRNA miR-124 regulates circadian behavior phase in Drosophila. Here, we report that miR-124 expression during larval development is required for proper phasing of both morning and evening peaks of activity in adults. Loss of miR-124 results in significant miswiring within the circadian neural network and severely alters neural activity rhythms in the ventral Lateral Neurons (s-LNvs) and the posterior Dorsal Neurons 1 (DN1ps), which control the timing of morning and evening activity. Silencing the s-LNvs in miR-124 mutant flies restores the phase of evening activity, while activating the DN1ps rescues the phases of both morning and evening activities. Our findings thus reveal the pivotal role of miR-124 in sculpting the circadian neural network during development and its long-lasting impact on circuit activity and adult circadian behavior.

neuroscience↗

bioRxiv2025

Loss of intestinal endosome associated protein sorting nexin 27 disrupts epithelial barrier and promotes inflammation

Backgrounds and aimsSNX27, member of the sorting nexin (SNX) family, carries a unique PDZ domain and mediates recycling of endocytosed transmembrane proteins. SNX27 is critical for neurodevelopmental processes, however its role in intestine remains unexplored. We aim to determine the previously unknown roles of SNX27 in regulating intestinal homeostasis, epithelial barrier integrity, and inflammatory responses. MethodsWe used available datasets to analyze SNX27 expression in human IBD. We generated a novel mouse model of SNX27 conditional deletion from intestinal epithelial cells (SNX27{Delta}IEC) and challenged these mice with Dextran Sulfate Sodium (DSS). ResultsSNX27 expression was significantly lower in human IBD, including UC and CD. SNX27{Delta}IEC mice had significantly lower bodyweight and exhibited increased proliferation and poor differentiation of secretory Paneth and Goblet cells. We found reduced mucin layer and downregulation of crucial epithelial barrier proteins {Delta}-catenin, E-cadherin, ZO-1, and Claudin10 in SNX27{Delta}IEC mice. SNX27{Delta}IEC mice showed high intestinal permeability and spontaneously developed intestinal inflammation. Moreover, SNX27{Delta}IEC mice were more susceptible towards DSS-induced colitis, compared to the SNX27Loxp mice. ConclusionOverall, deletion of intestinal epithelial SNX27 weakens barrier functions and promotes inflammation. Our results indicate a novel role of SNX27 in regulating intestinal physiology and protecting against intestinal disorders. Thus, understanding the mechanisms of SNX27 downregulation in IBD will provide insights into new prevention and targets against chronic inflammation. SynopsisO_LISNX27 recycles internalized transmembrane proteins in the endocytic pathway. Human IBD showed reduced levels of SNX27. C_LIO_LISNX27 plays novel functions by maintaining intestinal homeostasis and inhibiting inflammation. C_LIO_LISNX27 protects the host against losing intestinal integrity during inflammation. C_LI

physiology↗

bioRxiv2025

MISO Regulates Mitochondria Dynamics and mtDNA Homeostasis by Establishing Inner Membrane Subdomains

Mitochondrial dynamics and mtDNA homeostasis are essential for numerous biological processes and have recently been linked through distinct subdomains termed small MTFP1-enriched mitochondria (SMEM). However, the molecular mechanisms governing this connection remain unclear. Here, we identified MISO (Mitochondrial Inner membrane Subdomain Organizer), a novel protein that regulates mitochondrial dynamics and drives SMEM formation in response to inner mitochondrial membrane (IMM) stresses. We demonstrate that MISO regulates mitochondrial dynamics in both Drosophila stem cells in vivo and mammalian cells in vitro. Mechanistic study showed that MISO promotes mitochondrial fission while inhibiting fusion. Notably, MISO induces SMEM formation and facilitates their peripheral fission, which regulates the lysosomal degradation of mtDNA. Meanwhile, MISO knock-out completely abolishes SMEM generation, indicating that MISO is both necessary and sufficient for SMEM biogenesis. Furthermore, SMEM functionality requires MISO-dependent recruitment of MTFP1 and subsequent engagement of downstream effectors, including the FIS1-DRP1 fission machinery. IMM stresses, including damages in mtDNA, OXPHOS complexes, and cristae, stabilize the normally short-lived MISO protein, thereby triggering SMEM assembly. Furthermore, MISO-orchestrated SMEM formation depends on its C-terminal domain, likely mediated by oligomerization. Together, our work elucidates a molecular mechanism by which IMM stresses affect mitochondrial dynamics and mtDNA homeostasis.

cell biology↗

bioRxiv2024

Zero valent sulfur is the product of assimilatory sulfite reductase and a substrate of cysteine synthase

The long process of the assimilatory sulfate-reduction consists of sulfate reduction to H2S and then H2S assimilation for cysteine synthesis. However, recent studies indicate that both H2S and zero valent sulfur (S0) are produced during dissimilatory sulfate reduction process, which leads to the question whether S0 also is involved in assimilatory sulfate-reduction. Herein, phylogenetic analysis grouped assimilatory sulfite reductases into five clusters and we re-examined four representatives from two major clusters. These enzymes produced both S0 and H2S from sulfite. However, S0 was more like a direct product, while H2S was just a derivative of S0 via chemical reduction. Phylogenetic analysis of cysteine synthases grouped them into six clusters, and we re-examined six representatives from two major clusters. These enzymes used both glutathione persulfide (GSSH, a common intracellular compound containing a S0 atom) and H2S as substrates to synthesize cysteine, but preferred to use GSSH. These findings indicated that S0, other than H2S, is the key intermediate during the process of inorganic sulfur converting to organic sulfur. ImportanceSulfate reduction is an important link in the global sulfur cycle. Assimilatory sulfate-reduction consists of sulfate-reduction to H2S and then H2S assimilation for cysteine synthesis. This concept was founded in 1950s and has not been challenged until today. In this study, we re-examined four representative assimilatory sulfite reductases (aSiRs) and found that these enzymes directly reduced sulfite to zero valent sulfur (S0). A small portion of produced S0 was reduced to H2S via aSiR-independent chemical reactions. Further, we re-examined six representative cysteine synthases and found that these enzymes used S0 derivative compounds (thiosulfate and glutathione persulfide) as substrates to synthesize cysteine. Thus, S0 is the key intermediate of assimilatory sulfate reduction process, other than H2S.

microbiology↗