Biology subjects

Rhee, H.-W.

Publications and source records attributed to Rhee, H.-W..

17 recordsLinked to original sources

bioRxiv2026

Spatial Metabolomics by Desthiobiotin Ligase (DESTNI) in Live Cells

Proximity labeling has transformed spatial proteomics by enabling compartment-resolved mapping of protein environments in living cells, yet its extension to small-molecule metabolites has not been demonstrated, probably due to limitations in labeling chemistry and labeled metabolites identification. Here, we introduce DESTNI, an engineered desthiobiotin (DTB) ligase derived from TurboID through directed evolution, and establish a platform for spatially resolved profiling of amine-containing metabolites. A directed evolution strategy based on a yeast display system yielded DESTNI with efficient DTB-dependent reactivity, enabling robust and compartment-specific proximity labeling across diverse subcellular environments. To identify the DTB-modified amino metabolome, we developed an integrated analytical framework combining DTB-modified amino metabolite standards, in vitro DESTNI profiling, and in silico MS/MS prediction, enabling systematic annotation of DTB-modified amino metabolites. To extend this chemistry to metabolites, we combined synthetic DTB-conjugated metabolite reference standards, in vitro DESTNI-reactive metabolite discovery, and machine-learning prediction of DTB-derivatized metabolites and oligopeptides. Organelle-targeted DESTNI recovered reproducible compartment-enriched amino metabolite signatures, including mitochondrial matrix-enriched glycine, 5-aminolevulinic acid, ornithine and spermidine adducts, as well as nuclear-enriched {gamma}-aminobutyric acid and 5-aminovaleric acid adducts. Together, this work establishes DESTNI as a proximity labeling platform that bridges spatial proteomics and metabolomics and provides a general strategy for mapping subcellular biochemical environments in living cells.

biochemistry↗

bioRxiv2026

Water oxidation-driven histidine dioxidation enables probe-free proximity labeling

Photocatalytic proximity labeling (photo-PL) has emerged as a powerful tool for spatial proteomics in subcellular compartments. However, many photo-PL toolboxes rely on singlet oxygen (1O2) to generate highly unstable endoperoxide intermediates that must be trapped immediately by high concentrations of exogenous probes. This constraint can bias spatial proteome coverage, particularly in dynamic and heterogeneous compartments such as endosomes and exosomes, where probe accessibility is intrinsically nonuniform. Here, we develop IDM, an organic photocatalyst that generates hydroxyl (*OH) and superoxide (O *-) radicals via water oxidation instead of 1O , enabling a synergistic dual-radical mechanism for probe-free proximal protein mapping in live cells (PF-Map). The resulting radicals dioxidize proximal histidine residues into a persistent dioxidized state (His-2O) that is thermodynamically stabilized as lactam tautomers, which remain electrophilic and chemically addressable after cell lysis. By decoupling histidine oxidation from live{square}cell probe capture, PF{square}Map can minimize spatial bias arising from heterogeneous probe distribution. Applying PF{square}Map to intracellular vesicle trafficking, we find that both PF{square}Map and a probe{square}dependent workflow (PD{square}Map) robustly identify exosome markers, whereas PF{square}Map additionally reveals a hidden vesicle trafficking-related subproteome that PD-Map underestimated. Together, we establish a minimally biased photocatalytic strategy for spatial protein mapping in complex biological systems. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=111 SRC="FIGDIR/small/731337v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@13da43dorg.highwire.dtl.DTLVardef@1e9cb7corg.highwire.dtl.DTLVardef@2e7557org.highwire.dtl.DTLVardef@19e16c_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2026

hnRNPA2B1 Modulates Early TIA1 Recruitment into Stress Granules through an RNA-Dependent Assembly Mechanism

Stress granules (SGs) are dynamic, membrane-less assemblies that form in the cytoplasm in response to cellular stress. The ordered recruitment of proteins into SGs is fundamental to condensate composition and function, yet the molecular determinants of this ordered client recruitment remain incompletely understood. Using proximity photo-crosslinking proteomics, we identified heterogeneous nuclear ribonucleoprotein A2B1 (hnRNPA2B1) as a TIA1-proximal protein preferentially enriched in SGs under arsenite stress. Knockdown of hnRNPA2B1 preferentially delayed TIA1 enrichment in G3BP1-marked SGs at 20 min without affecting G3BP1 or the overall SG-positive cell fraction, and this phenotype showed directional rescue upon re-expression. In vitro droplet reconstitution assays with purified proteins revealed that hnRNPA2B1 and RNA cooperatively increased TIA1 incorporation capacity into G3BP1 condensates, an effect not attributable to changes in droplet size. Kinetic fitting identified hnRNPA2B1 + RNA as uniquely increasing the plateau amplitude of TIA1 recruitment (Cohens d = 1.62 versus RNA-alone condition). Coarse-grained simulations support an inside-out assembly model in which hnRNPA2B1 stabilizes the condensate core through homotypic interactions while RNA-bound TIA1 accumulates at the periphery. Together, these findings identify hnRNPA2B1 as a capacity-determining modulator of early TIA1 recruitment and provide a framework for understanding ordered protein assembly within stress granules.

cell biology↗

bioRxiv2026

Endogenous nucleophilic scavengers of reactive acyl-species neutralize carbon stress

Aberrant protein acylation by reactive acyl species (RAS)--termed carbon stress--is a major driver of aging and metabolic disease. While enzymatic deacylases such as sirtuins counteract aberrant acylation, whether endogenous metabolites can directly neutralize RAS remains unclear. Here, we report that nucleophilic metabolites--taurine, spermidine, and ethanolamine--react with acyl-CoAs, preventing aberrant protein acylation and potentially extending lifespan. We demonstrate that spermidine scavenges acetyl-CoA within the catalytic pocket of p300, a histone acetyltransferase, and extends lifespan in Drosophila. Taurine supplementation in mice fed a high-fat diet promotes N-fatty acyl taurine formation, confirming in vivo scavenging of RAS. These findings identify endogenous nucleophilic metabolites as scavengers that neutralize carbon stress, with implications for combating aging and metabolic disease. SummaryProtein homeostasis is constantly challenged by reactive metabolic intermediates that drive aberrant post-translational modifications, contributing to aging and metabolic disease. While the antioxidant systems that neutralize reactive oxygen species (ROS) are well characterized, whether analogous defenses exist against reactive acyl species (RAS)--the metabolic drivers of non-enzymatic protein acylation, termed carbon stress--has remained unknown. Here we show that three abundant endogenous nucleophilic metabolites--taurine, spermidine, and ethanolamine--directly intercept reactive acyl-CoA species through nucleophilic attack, preventing aberrant protein acylation. We demonstrate that spermidine scavenges acetyl-CoA within the catalytic pocket of the histone acetyltransferase p300, effectively buffering p300-mediated hyperacetylation of muscle, cytosolic, and mitochondrial proteins and extending lifespan in a Drosophila model of p300-driven toxicity. In mice fed a high-fat diet, taurine supplementation promotes the formation of N-fatty acyl taurines, providing direct in vivo evidence for nucleophilic scavenging of diet-derived RAS. Our findings reveal a previously unrecognized metabolite-based defense system--parallel to classical antioxidant defenses against ROS--that neutralizes carbon stress, with broad implications for understanding the molecular mechanisms of aging and the long-observed but mechanistically unexplained health benefits of taurine and spermidine.

biochemistry↗

bioRxiv2026

MitoAtlas: a Domain-Resolved Spatial Map of the HumanMitochondrial Proteome

Mitochondrial function depends on the precise sub-organellar localization and topological orientation of its proteome. However, mapping this architecture with domain-level precision across the double-membrane system has remained challenging. Here, we present MitoAtlas, a spatial systems biology resource built on SR-PL (super-resolution proximity labeling) that resolves the sub-mitochondrial architecture of 861 proteins at domain-level resolution. By deploying 42 spatially restricted APEX2 and BioID/BioID2 baits across mitochondrial compartments and cytosol in HEK293T-REx cells, we mapped 13,440 unique proximity-labeled sites. Integrating high-density spatial data with a machine-learning classification pipeline and AlphaFold structural modeling, we resolved membrane topologies for 196 transmembrane proteins and assigned sub-mitochondrial localizations to 160 previously unannotated mitochondrial proteins absent from MitoCarta3.0, including MINPP1 as an intermembrane space resident. Coupling bait-specific proximity labeling signatures with AlphaFold structure prediction and metabolite docking identified 47 protein-protein interactions, including the LETM1-Citrate Synthase complex, and 155 protein-metabolite interactions. MitoAtlas is available at mitoatlas.org as a domain-resolution spatial map of mitochondrial architecture and metabolism.

cell biology↗

bioRxiv2026

The mitochondrial cohibitin complex facilitates the biogenesis of inner membrane proteins

The inner membrane of mitochondria contains many membrane-embedded carrier proteins of the SLC25 family to facilitate the exchange of metabolites between the cytosol and mitochondria. These carriers use a specific import route for their biogenesis that relies on the TIM22 complex as an inner membrane translocase. The molecular details of carrier biogenesis are not well understood. Using an improved, desthiobiotin-based proximity labeling approach called Destni in living yeast cells, we identified the mitochondrial protein Aim11 as an interactor of newly imported carrier proteins. Aim11 forms a 160 kDa complex together with Iai11, Gep7 and Mtc1 in the mitochondrial inner membrane that we named the comrade-of-prohibitin (cohibitin) complex owing to its genetic interaction with prohibitins. Deletion of Aim11 impairs the import of carrier proteins into the inner membrane and renders cells hypersensitive to carrier overexpression. Our data suggest that the cohibitin complex plays a quality control function that supports the TIM22-mediated insertion of carrier proteins into the inner membrane of mitochondria. SummaryKizmaz et al. identified Aim11 as a novel quality control factor that facilitates the insertion of carrier proteins into the inner membrane of mitochondria. Aim11 is part of the membrane-embedded cohibitin complex which cooperates with prohibitins in inner membrane protein biogenesis.

biochemistry↗

bioRxiv2024

Painting cell-cell interactions by horseradish peroxidase and endogenously generated hydrogen peroxide

Cell-Cell interactions are fundamental in biology for maintaining physiological conditions, with direct contact being the most straightforward mode of interaction. Recent advancements have led to the development of various chemical tools for detecting or identifying these interactions. However, the use of exogenous cues, such as toxic reagents, bulky probes, and light irradiations, can disrupt normal cell physiology. For example, the toxicity of hydrogen peroxide (H2O2) limits the applications of peroxidases in proximity labeling field. In this study, we aimed to address this limitation by demonstrating that membrane-localized Horseradish Peroxidase (HRP-TM) efficiently utilizes endogenously generated extracellular H2O2. By harnessing endogenous H2O2, we observed that HRP-TM-expressing cells can effectively label contacting cells without the need for exogenous H2O2 treatment. Furthermore, we confirmed that HRP-TM labels proximal cells in an interaction-dependent manner. These findings offer a novel approach for studying cell-cell interactions under more physiological conditions, without the confounding effects of exogenous stimuli. Our study contributes to elucidating cell-cell interaction networks in various model organisms, providing valuable insights into the dynamic interplay between cells in their native network.

biochemistry↗

bioRxiv2023

Mitochondrial thermogenesis regulates heat-shock response in the nucleus

Mitochondrial thermogenesis is a process in which heat is generated by mitochondrial respiration. In living organisms, the thermogenic mechanisms that maintain body temperature have been studied extensively in fat cells, with little knowledge on how mitochondrial heat may act beyond energy expenditure. Here, we highlighted exothermic oxygen reduction reaction ({Delta}Hf{degrees} = -285 kJ/mol) is the main source of the protonophore-induced mitochondrial thermogenesis and this heat was conducted to other cellular organelles, including the nuclei. As a result, mitochondrial heat that reached the nucleus initiated the classical heat shock response, including the formation of nuclear stress granules and localization of heat shock factor 1 to chromatin. Consequently, activated HSF1 increases gene expression associated with the response to thermal stress in mammalian cells. Our results illustrate heat generated within the cells as a potential source of mitochondrial-nucleus communication and expand our understanding of the biological functions of mitochondria in cell physiology.

cell biology↗

bioRxiv2023

Mitochondrial protein FKBP8 captures PDZD8 to form mitochondria-ER contacts

Mitochondria-ER membrane contact sites (MERCS) represent a fundamental ultrastructural feature underlying unique biochemistry and physiology in eukaryotic cells. The ER protein PDZD8 is required for the formation of MERCS in many cell types, however, its tethering partner on the outer mitochondrial membrane (OMM) is currently unknown. Here we identified the OMM protein FKBP8 as the tethering partner of PDZD8 using a combination of unbiased proximity proteomics, CRISPR-Cas9 endogenous protein tagging, Cryo-Electron Microscopy (Cryo-EM) tomography, and correlative light-EM (CLEM). Single molecule tracking revealed highly dynamic diffusion properties of PDZD8 along the ER membrane with significant pauses and capture at MERCS. Overexpression of FKBP8 was sufficient to narrow the ER-OMM distance, whereas independent versus combined deletions of these two proteins demonstrated their interdependence for MERCS formation. Furthermore, PDZD8 enhances mitochondrial complexity in a FKBP8-dependent manner. Our results identify a novel ER-mitochondria tethering complex that regulates mitochondrial morphology in mammalian cells.

cell biology↗

bioRxiv2023

Spatial Proteomics Reveals Novel TREM2 Interactors in ER-Mitochondria Interface in Microglia

Triggering receptor expressed on myeloid cells 2 (TREM2) plays a central role in microglial biology and the pathogenesis of Alzheimers disease (AD). Besides DNAX-activating protein 12 (DAP12), a communal adaptor for TREM2 and many other receptors, other cellular interactors of TREM2 remain largely elusive. We employed a proximity labeling approach using a biotin ligase, TurboID, for mapping protein-protein interactions in live mammalian cells. We discovered novel TREM2-proximal proteins with diverse functions, including those localized to the Mitochondria-ER contact sites (MERCs), a dynamic subcellular hub implicated in a number of crucial cell physiology such as lipid metabolism. TREM2 deficiency alters the thickness (inter-organelle distance) of MERCs, a structural parameter of metabolic state, in microglia derived from human induced pluripotent stem cells. Our TurboID-based TREM2 interactome study suggest novel roles for TREM2 in the structural plasticity of the MERCs, raising the possibility that dysregulation of MERC-related TREM2 functions contribute to AD pathobiology.

neuroscience↗

bioRxiv2021

Valosin-containing protein regulates the stability of amyotrophic lateral sclerosis-causing fused in sarcoma granules in cells by changing ATP concentrations inside the granules

Fused in sarcoma (FUS) undergoes liquid-liquid phase separation (LLPS) to form granules in cells, leading to pathogenic aggregations that cause neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Proteomics analysis revealed that FUS granules contain valosin-containing protein (VCP), a member of the AAA family ATPase. Confocal microscopy images showed that VCP co-localized in the FUS granules in cells. This study demonstrates that VCP in granules has a two-faced role in FUS granulation: VCP stabilizes de novo FUS granules, while VCP present in the granules for extended periods dissolves them. This VCP function relies on its ATPase activity to consume ATP in granules. VCP stabilizes de novo FUS by reducing intragranular ATP concentrations to a range below the cytosolic concentration. VCP continually consumes ATP during its stay in the granules, which eventually lowers ATP concentrations to a range that destabilizes the granules. VCP, therefore, acts as a timer to limit the residence of FUS granules in cells and thereby prohibits the FUS fibrillization that occurs in persistent granules. VCP ATPase activity plays a role in FUS granule turnover. Summary statementVCP recruited to FUS granules regulates the stability of the granules in a time-dependent manner by consuming intragranular ATP with its ATPase activity.

cell biology↗

bioRxiv2021

In vivo mitochondrial matrix proteome profiling reveals RTN4IP1/OPA10 as an antioxidant NADPH oxidoreductase

Targeting proximity labeling enzymes to specific cellular locations is a viable strategy for profiling subcellular proteomes. Here, we generated transgenic mice expressing a mitochondrial matrix-targeted ascorbate peroxidase (MAX-Tg) to analyze tissue-specific matrix proteomes. Desthiobiotin-phenol labeling of muscle tissues from MAX-Tg mice allowed for efficient profiling of mitochondrial-localized proteins in these tissues. Comparative analysis of matrix proteomes from MAX-Tg muscle tissues revealed differential enrichment of mitochondrial proteins related to energy production in between different muscle groups. Reticulon 4 interacting protein 1 (RTN4IP1), also known as Optic Atrophy-10 (OPA10), was highly enriched in the cardiac and soleus muscles and was found to localize to the mitochondrial matrix via a strong mitochondrial targeting sequence at its N-terminus. Protein structure analysis revealed that RTN4IP1 is an NADPH oxidoreductase with structural homology to bacterial quinone oxidoreductase. Enzymatic activity assays, interactome analysis, and metabolite profiling confirmed a function for RTN4IP1 in coenzyme Q (CoQ) biosynthesis. Rtn4ip1-knockout C2C12 cells had reduced CoQ9 levels, were vulnerable to oxidative stress, and had decreased oxygen consumption rates and ATP production. Collectively, RTN4IP1 is a mitochondrial antioxidant NADPH oxidoreductase supporting oxidative phosphorylation activity in muscle tissue.

cell biology↗

bioRxiv2021

IPMK physically binds to the SWI/SNF complex and modulates BRG1 occupancy

Inositol polyphosphate multikinase (IPMK), a key enzyme in the inositol polyphosphate (IP) metabolism, is a pleiotropic signaling factor involved in major biological events including transcriptional control. In yeasts, IPMK and its IP products were known to promote the activity of SWI/SNF chromatin remodeling complex, which plays a critical role in gene expression by regulating chromatin accessibility. However, the direct linkage between IPMK and chromatin remodelers remains unclear, raising a question on how IPMK contributes to the transcriptional regulation in mammals. By employing unbiased screenings and in vivo/in vitro immunoprecipitations, here we demonstrated that IPMK physically associates with native mammalian SWI/SNF complexes by directly binding to SMARCB1, BRG1, and SMARCC1. Furthermore, we identified the specific domains required for the IPMK-SMARCB1 binding. Notably, using CUT&RUN and ATAC-seq assays, we discovered that IPMK co-localizes with BRG1 and regulates BRG1 localization as well as BRG1-mediated chromatin accessibility in a genome-wide manner (including promoter-TSS) in mouse embryonic stem cells. Finally, our mRNA-seq analyses revealed that IPMK and SMARCB1 regulate common gene sets, validating a functional link between IPMK and SWI/SNF complex. Together, these findings establish an importance of IPMK in promoter targeting of the SWI/SNF complex, thereby contributing to SWI/SNF-meditated chromatin accessibility and transcription.

molecular biology↗

bioRxiv2021

Endomembrane systems are reorganized by ORF3a and Membrane (M) of SARS-CoV-2

The endomembrane reticulum (ER) is largely reorganized by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). SARS-CoV-2 ORF3a and membrane (M) protein expression affects ER-derived structures including cubic membrane and double membrane vesicles in coronavirus-infected cells; however, the molecular mechanisms underlying ER remodeling remain unclear. We introduced a "plug and playable" proximity labeling tool (TurboID-GBP) for interactome mapping of GFP-tagged SARS-CoV-2 ORF3a and M proteins. Through mass spectrometric identification of the biotinylated lysine residue (K+226 Da) on the viral proteins using Spot-TurboID workflow, 117 and 191 proteins were robustly determined as ORF3a and M interactomes, respectively, and many, including RNF5 (E3 ubiquitin ligase), overlap with the mitochondrial-associated membrane (MAM) proteome. RNF5 expression was correlated to ORF3a ubiquitination. MAM formation and secreted proteome profiles were largely affected by ORF3a expression. Thus, SARS-CoV-2 may utilize MAM as a viral assembly site, suggesting novel anti-viral treatment strategies for blocking viral replication in host cells. HighlightsO_LISARS-CoV-2 proteins ORF3a and M alter endoplasmic reticulum proteome profile C_LIO_LIORF3a affects mitochondrial-associated membrane formation C_LIO_LISARS-CoV-2 may utilize mitochondrial-associated membrane as viral assembly site C_LIO_LIORF3a and M interactome proteins may serve as targets for COVID-19 treatment C_LI eTOC BlurbER remodelling by SARS-CoV-2 ORF3a and M protein

biochemistry↗

bioRxiv2020

Dynamic tracking and identification of tissue-specific secretory proteins in the circulation of live mice

Here we describe iSLET (in situ Secretory protein Labeling via ER-anchored TurboID) which labels secretory pathway proteins as they transit through the ER-lumen to enable dynamic tracking of tissue-specific secreted proteomes in vivo. We expressed iSLET in the mouse liver and demonstrated efficient in situ labeling of the liver-specific secreted proteome which could be tracked and identified within circulating blood plasma. iSLET is a versatile and powerful tool for studying spatiotemporal dynamics of secretory proteins, a valuable class of biomarkers and therapeutic targets.

biochemistry↗

bioRxiv2020

Split-TurboID enables contact-dependent proximity labeling in cells

Proximity labeling (PL) catalyzed by promiscuous enzymes such as TurboID have enabled the proteomic analysis of subcellular regions difficult or impossible to access by conventional fractionation-based approaches. Yet some cellular regions, such as organelle contact sites, remain out of reach for current PL methods. To address this limitation, we split the enzyme TurboID into two inactive fragments that recombine when driven together by a protein-protein interaction or membrane-membrane apposition. At endoplasmic reticulum (ER)-mitochondria contact sites, reconstituted TurboID catalyzed spatially-restricted biotinylation, enabling the enrichment and identification of >100 endogenous proteins, including many not previously linked to ER-mitochondria contacts. We validated eight novel candidates by biochemical fractionation and overexpression imaging. Overall, split-TurboID is a versatile tool for conditional and spatially-specific proximity labeling in cells.

cell biology↗

bioRxiv2019

NSUN2 introduces 5-methylcytosines in mammalian mitochondrial tRNAs

Maintenance and expression of mitochondrial DNA is indispensable for proper function of the oxidative phosphorylation machinery. Post-transcriptional modification of mitochondrial RNA has emerged as one of the key regulatory steps of human mitochondrial gene expression. Mammalian NOP2/Sun RNA Methyltransferase Family Member 2 (NSUN2) has been characterised as an RNA methyltransferase that introduces 5-methylcytosine (m5C) in nuclear-encoded tRNAs, mRNAs, microRNA and noncoding RNAs. In these roles, NSUN2 has been associated with cell proliferation and differentiation. Pathogenic variants in NSUN2 have been linked with neurodevelopmental disorders. Here we employ spatially restricted proximity labelling and immunodetection to demonstrate that NSUN2 is imported into the matrix of mammalian mitochondria. Using three genetic models for NSUN2 inactivation - knockout mice, patient-derived fibroblasts and CRISPR/Cas9 knockout in human cells - we show that NSUN2 in necessary for the generation of m5C at positions 48, 49 and 50 of several mammalian mitochondrial tRNAs. Finally, we show that inactivation of NSUN2 does not have a profound effect on mitochondrial tRNA stability and oxidative phosphorylation in differentiated cells. We discuss the importance of the newly discovered function of NSUN2 in the context of human disease.

biochemistry↗