Oxidative photocatalysis on membranes triggers non-canonical pyroptosis.

Intracellular membranes composing organelles of eukaryotes include membrane proteins playing crucial roles in physiological functions. However, a comprehensive understanding of the cellular responses triggered by intracellular membrane-focused oxidative stress remains elusive. Herein, we report an amphiphilic photocatalyst localised in intracellular membranes to damage membrane proteins oxidatively, resulting in non-canonical pyroptosis. Our developed photocatalysis generates hydroxyl radicals and hydrogen peroxides via water oxidation, which is accelerated under hypoxia. Single-molecule magnetic tweezers reveal that photocatalysis-induced oxidation markedly destabilised membrane protein folding. In cell environment, label-free quantification reveals that oxidative damage occurs primarily in membrane proteins related to protein quality control, thereby aggravating mitochondrial and endoplasmic reticulum stress and inducing lytic cell death. Notably, the photocatalysis activates non-canonical inflammasome caspases, resulting in gasdermin D cleavage to its pore-forming fragment and subsequent pyroptosis. These findings suggest that the oxidation of intracellular membrane proteins triggers non-canonical pyroptosis.

Iterative SuFEx approach for sequence-regulated oligosulfates and its extension to periodic copolymers.

The synthesis of sequence-regulated oligosulfates has not yet been established due to the difficulties in precise reactivity control. In this work, we report an example of a multi-directional divergent iterative method to furnish oligosulfates based on a chain homologation approach, in which the fluorosulfate unit is regenerated. The oligosulfate sequences are determined by high resolution mass spectrometry of the hydrolyzed fragments, and polysulfate periodic copolymers are synthesized by using oligomeric bisfluorosulfates in a bi-directional fashion. The synthetic utility of this iterative ligation is demonstrated by preparing crosslinked network polymers as synthetic adhesive materials.

Suboptimal Mitochondrial Activity Facilitates Nuclear Heat Shock Responses for Proteostasis and Genome Stability.

Thermal stress induces dynamic changes in nuclear proteins and relevant physiology as a part of the heat shock response (HSR). However, how the nuclear HSR is fine-tuned for cellular homeostasis remains elusive. Here, we show that mitochondrial activity plays an important role in nuclear proteostasis and genome stability through two distinct HSR pathways. Mitochondrial ribosomal protein (MRP) depletion enhanced the nucleolar granule formation of HSP70 and ubiquitin during HSR while facilitating the recovery of damaged nuclear proteins and impaired nucleocytoplasmic transport. Treatment of the mitochondrial proton gradient uncoupler masked MRP-depletion effects, implicating oxidative phosphorylation in these nuclear HSRs. On the other hand, MRP depletion and a reactive oxygen species (ROS) scavenger non-additively decreased mitochondrial ROS generation during HSR, thereby protecting the nuclear genome from DNA damage. These results suggest that suboptimal mitochondrial activity sustains nuclear homeostasis under cellular stress, providing plausible evidence for optimal endosymbiotic evolution via mitochondria-to-nuclear communication.

Direct 18F-Fluorosulfurylation of Phenols and Amines Using an [18F]FSO2+ Transfer Agent Generated In Situ.

We report the direct radiofluorosulfurylation method for the synthesis of 18F-labeled fluorosulfuryl derivatives from phenols and amines using an [18F]FSO2+ transfer agent generated in situ. Nucleophilic radiofluorination is achieved even in a hydrous organic medium, obviating the need for azeotropic drying and the use of cryptands. This unprecedented, operationally simple isotopic functionalization facilitates the reliable production of potential radiotracers for positron emission tomography, rendering facile access to SuFEx radiochemistry.

Microphysiological system recapitulating the pathophysiology of adipose tissue in obesity.

A growing body of evidence has indicated that white adipose tissue (AT) remodeling is a major trigger for obesity-associated metabolic complications. However, the scarcity of translational models is an obstacle to the development of medicines that act on adipose restoration. Here, we describe a microphysiological system (MPS) that emulates the unique features of reprogrammed AT as a new in vitro tool for studying AT pathophysiology in obesity. The AT MPS contained mature adipocytes embedded in an extracellular matrix (ECM) hydrogel interfaced with AT microvascular endothelium, which was constantly perfused with fresh media. The unique biochemical signals due to the remodeled ECM in obesity were recapitulated using a decellularized AT ECM (AT dECM) hydrogel, which preserves the features of altered ECM composition in obesity. The mature adipocytes embedded in the AT dECM hydrogel maintained their function and morphology for a week without dedifferentiation. Using the AT MPS, we successfully modeled inflammation-induced AT microvascular dysfunction, the recruitment of immune cells due to the upregulation of cell adhesion molecules, and higher cancer cell adhesion as an indicator of metastasis, which are observed in obese individuals. The AT MPS may therefore represent a promising platform for understanding the dynamic cellular interplay in obesity-induced AT remodeling and validating the efficacy of drugs targeting AT in obesity. STATEMENT OF SIGNIFICANCE: The lack of translational in vitro white adipose tissue (AT) models is one of the main obstacles for understanding the obesity-induced reprogramming and the development of medicines. We report herein the AT microphysiological system (MPS), which recapitulates obesity and normal conditions and yields cell- and AT dECM-derived signals, thereby allowing accurate comparative in vitro analyses. Using the AT MPS, we successfully modeled reprogrammed AT in obesity conditions, including inflammation-induced AT vascular dysfunction, the recruitment of immune cells, and higher cancer cell metastasis, which are observed in obese individuals. Our proposed adipose tissue model providing physiological relevance and complexity may therefore enhance the understanding of obesity-associated disorders and be used to investigate their underlying molecular mechanisms to develop pharmacologic treatment strategies.

GPR143 controls ESCRT-dependent exosome biogenesis and promotes cancer metastasis.

Exosomes transport a variety of macromolecules and modulate intercellular communication in physiology and disease. However, the regulation mechanisms that determine exosome contents during exosome biogenesis remain poorly understood. Here, we find that GPR143, an atypical GPCR, controls the endosomal sorting complex required for the transport (ESCRT)-dependent exosome biogenesis pathway. GPR143 interacts with HRS (an ESCRT-0 Subunit) and promotes its association to cargo proteins, such as EGFR, which subsequently enables selective protein sorting into intraluminal vesicles (ILVs) in multivesicular bodies (MVBs). GPR143 is elevated in multiple cancers, and quantitative proteomic and RNA profiling of exosomes in human cancer cell lines showed that the GPR143-ESCRT pathway promotes secretion of exosomes that carry unique cargo, including integrins signaling proteins. Through gain- and loss-of-function studies in mice, we show that GPR143 promotes metastasis by secreting exosomes and increasing cancer cell motility/invasion through the integrin/FAK/Src pathway. These findings provide a mechanism for regulating the exosomal proteome and demonstrate its ability to promote cancer cell motility.

Epigenetic regulation of Neuregulin 1 promotes breast cancer progression associated to hyperglycemia.

Hyperglycemia is a risk factor for breast cancer-related morbidity and mortality. Hyperglycemia induces Neuregulin 1 (Nrg1) overexpression in breast cancer, which subsequently promotes tumor progression. However, molecular mechanisms underlying hyperglycemia-induced Nrg1 overexpression remain poorly understood. Here, we show that hyperglycemia causes active histone modifications at the Nrg1 enhancer, forming enhanceosome complexes where recombination signal binding protein for immunoglobulin kappa J region (RBPJ), E1A binding protein p300 (P300), and SET domain containing 1 A (SETD1A) are recruited to upregulate Nrg1 expression. Deletions in RBPJ-binding sites causes hyperglycemia-controlled Nrg1 levels to be downregulated, resulting in decreased tumor growth in vitro and in vivo. Mice with modest-temporary hyperglycemia, induced by low-dose short-exposure streptozotocin, display accelerated tumor growth and lapatinib resistance, whereas combining lapatinib with N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S42 phenylglycine t-butyl ester (DAPT) ameliorates tumor growth under these modest hyperglycemic conditions by inhibiting NOTCH and EGFR superfamilies. NOTCH activity is correlated with NRG1 levels, and high NRG1 levels predicts poor outcomes, particularly in HER2-positive breast cancer patients. Our findings highlight the hyperglycemia-linked epigenetic modulation of NRG1 as a potential therapeutic strategy for treating breast cancer patients with diabetes.

Identification of a Target Site for Covalent Inhibition of Protein Phosphohistidine Phosphatase 1.

Despite the recent discovery of numerous phosphohistidine (pHis) sites in mammalian proteomes, the functions of this labile post-translational modification (PTM) mostly remain unknown. Phosphohistidine phosphatase 1 (PHPT1), one of the few known protein pHis phosphatases, regulates important cellular processes, and its genetic knockdown attenuated cancer cell proliferation and a liver fibrosis model. Unfortunately, the lack of PHPT1 inhibitors has limited further understanding and the therapeutic potential of this unique enzyme. We report that PHPT1 can be covalently inhibited by targeting Cys73, a residue that is nonessential for the enzyme activity. We also determined the inhibition kinetics of various small molecule electrophiles as potential warheads against PHPT1. Our results lay a foundation for the development of more potent and specific PHPT1 inhibitors.

Identification of proteomic landscape of drug-binding proteins in live cells by proximity-dependent target ID.

Direct identification of the proteins targeted by small molecules can provide clues for disease diagnosis, prevention, and drug development. Despite concentrated attempts, there are still technical limitations associated with the elucidation of direct interactors. Herein, we report a target-ID system called proximity-based compound-binding protein identification (PROCID), which combines our direct analysis workflow of proximity-labeled proteins (Spot-ID) with the HaloTag system to efficiently identify the dynamic proteomic landscape of drug-binding proteins. We successfully identified well-known dasatinib-binding proteins (ABL1, ABL2) and confirmed the unapproved dasatinib-binding kinases (e.g., BTK and CSK) in a live chronic myeloid leukemia cell line. PROCID also identified the DNA helicase protein SMARCA2 as a dasatinib-binding protein, and the ATPase domain was confirmed to be the binding site of dasatinib using a proximity ligation assay (PLA) and in cellulo biotinylation assay. PROCID thus provides a robust method to identify unknown drug-interacting proteins in live cells that expedites the mode of action of the drug.

Inositol polyphosphate multikinase physically binds to the SWI/SNF complex and modulates BRG1 occupancy in mouse embryonic stem cells.

Inositol polyphosphate multikinase (IPMK), a key enzyme in inositol polyphosphate (IP) metabolism, is a pleiotropic signaling factor involved in major biological events, including transcriptional control. In the yeast, IPMK and its IP products promote the activity of the chromatin remodeling complex SWI/SNF, which plays a critical role in gene expression by regulating chromatin accessibility. However, the direct link between IPMK and chromatin remodelers remains unclear, raising the question of how IPMK contributes to transcriptional regulation in mammals. By employing unbiased screening approaches and in vivo/in vitro immunoprecipitation, here we demonstrate that mammalian IPMK physically interacts with the SWI/SNF complex by directly binding to SMARCB1, BRG1, and SMARCC1. Furthermore, we identified the specific domains required for 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 in mouse embryonic stem cells. Together, these findings show that IPMK regulates the promoter targeting of the SWI/SNF complex, thereby contributing to SWI/SNF-meditated chromatin accessibility, transcription, and differentiation in mouse embryonic stem cells.

Rapid access to polycyclic N-heteroarenes from unactivated, simple azines via a base-promoted Minisci-type annulation.

Conventional synthetic methods to yield polycyclic heteroarenes have largely relied on metal-mediated arylation reactions requiring pre-functionalised substrates. However, the functionalisation of unactivated azines has been restricted because of their intrinsic low reactivity. Herein, we report a transition-metal-free, radical relay π-extension approach to produce N-doped polycyclic aromatic compounds directly from simple azines and cyclic iodonium salts. Mechanistic and electron paramagnetic resonance studies provide evidence for the in situ generation of organic electron donors, while chemical trapping and electrochemical experiments implicate an iodanyl radical intermediate serving as a formal biaryl radical equivalent. This intermediate, formed by one-electron reduction of the cyclic iodonium salt, acts as the key intermediate driving the Minisci-type arylation reaction. The synthetic utility of this radical-based annulative π-extension method is highlighted by the preparation of an N-doped heptacyclic nanographene fragment through fourfold C-H arylation.

Valosin-containing protein regulates the stability of fused in sarcoma granules in cells by changing ATP concentrations.

Fused in sarcoma (FUS), a DNA/RNA-binding protein, undergoes liquid-liquid phase separation to form granules in cells. Aberrant FUS granulation is associated with neurodegenerative diseases, including amyotrophic lateral sclerosis and frontotemporal lobar degeneration. We found that FUS granules contain a multifunctional AAA ATPase, valosin-containing protein (VCP), which is known as a key regulator of protein degradation. FUS granule stability depends on ATP concentrations in cells. VCP ATPase changes the FUS granule stability time-dependently by consuming ATP to reduce its concentrations in the granules: VCPs in de novo FUS granules stabilize the granules, while long-lasting VCP colocalization destabilizes the granules. The proteolysis-promoting function of VCP may subsequently dissolve the unstabilized granules. We propose that VCP colocalized to the FUS granules acts as a timer to limit the residence time of the granules in cells.

Kap1 Regulates the Stability of Lin28A in Embryonic Stem Cells.

Lin28A is an RNA-binding protein that controls mammalian development and maintenance of the pluripotency of embryonic stem cells (ESCs) via regulating the processing of the microRNA let-7. Lin28A is highly expressed in ESCs, and ectopic expression of this protein facilitates reprogramming of somatic cells to induced pluripotent stem cells. However, the mechanisms underlying the post-translational regulation of Lin28A protein stability in ESCs remain unclear. In the present study, we identified Kap1 (KRAB-associated protein 1) as a novel Lin28A-binding protein using affinity purification and mass spectrometry. Kap1 specifically interacted with the N-terminal region of Lin28A through its coiled-coil domain. Kap1 overexpression significantly attenuated Lin28A ubiquitination and increased its stability. However, small interfering RNA-mediated knockdown of Kap1 promoted the ubiquitination of Lin28A, leading to its proteasomal degradation. Trim71, an E3 ubiquitin ligase, induced Lin28A degradation and Kap1 knockdown accelerated the Trim71-dependent degradation of Lin28A. Mutation of the lysine 177 residue of Lin28A to arginine abrogated the ubiquitination and degradation of Lin28A which were accelerated by Kap1 silencing. Moreover, Kap1 overexpression led to the accumulation of Lin28A in the cytoplasm, but not in the nucleus, and reduced the levels of let-7 subtypes. These results suggest that Kap1 plays a key role in regulation of the stability of Lin28A by modulating the Trim71-mediated ubiquitination and subsequent degradation of Lin28A, thus playing a pivotal role in the regulation of ESC self-renewal and pluripotency.

A chemical tool for blue light-inducible proximity photo-crosslinking in live cells.

We developed a proximity photo-crosslinking method (Spotlight) with a 4-azido-N-ethyl-1,8-naphthalimide (AzNP) moiety that can be converted to reactive aryl nitrene species using ambient blue light-emitting diode light. Using an AzNP-conjugated HaloTag ligand (VL1), blue light-induced photo-crosslinked products of various HaloTag-conjugated proteins of interest were detected in subcellular spaces in live cells. Chemical or heat stress-induced dynamic changes in the proteome were also detected, and photo-crosslinking in the mouse brain tissue was enabled. Using Spotlight, we further identified the host interactome of SARS-CoV-2 nucleocapsid (N) protein, which is essential for viral genome assembly. Mass analysis of the VL1-crosslinked product of N-HaloTag in HEK293T cells showed that RNA-binding proteins in stress granules were exclusively enriched in the cross-linked samples. These results tell that our method can reveal the interactome of protein of interest within a short distance in live cells.

Synthesis of α,ß-unsaturated ketones through nickel-catalysed aldehyde-free hydroacylation of alkynes.

α,ß-Unsaturated ketones are common feedstocks for the synthesis of fine chemicals, pharmaceuticals, and natural products. Transition metal-catalysed hydroacylation reactions of alkynes using aldehydes have been recognised as an atom-economical route to access α,ß-unsaturated ketones through chemoselective aldehydic C-H activation. However, the previously reported hydroacylation reactions using rhodium, cobalt, or ruthenium catalysts require chelating moiety-bearing aldehydes to prevent decarbonylation of acyl-metal-hydride complexes. Herein, we report a nickel-catalysed anti-Markovnikov selective coupling process to afford non-tethered E-enones from terminal alkynes and S-2-pyridyl thioesters in the presence of zinc metal as a reducing agent. Utilization of a readily available thioester as an acylating agent and water as a proton donor enables the mechanistically distinctive and aldehyde-free hydroacylation of terminal alkynes. This non-chelation-controlled approach features mild reaction conditions, high step economy, and excellent regio- and stereoselectivity.

Nickelocene as an Air- and Moisture-Tolerant Precatalyst in the Regioselective Synthesis of Multisubstituted Pyridines.

Ni(COD)2-catalyzed cycloaddition reactions to access pyridines have been extensively studied. However, this catalyst typically requires drying procedures and inert-atmosphere techniques for the reactions. Herein, we report operationally simple nickel(0) catalysis to access substituted pyridines from various nitriles and 1,6-diynes without the aid of air-free techniques. The Ni-Xantphos-based catalytic manifold is tolerant to air, moisture, and heat while promoting the [2 + 2 + 2] cycloaddition reactions with high reaction yields and broad substrate scope. In addition, we disclose that not only the steric effect but also the frontier molecular orbital interactions can play a critical role in determining the regiochemical outcome of nickel-catalyzed [2 + 2 + 2] cycloaddition for the synthesis of substituted pyridines.

Late-Stage 18F/19F Isotopic Exchange for the Synthesis of 18F-Labeled Sulfamoyl Fluorides.

Synthesis of sulfamoyl [18F]fluorides has been a challenging topic owing to the inefficient nucleophilic radiofluorination of sulfamoyl derivatives. Herein, we report an 18F/19F isotopic exchange approach to synthesize various sulfamoyl [18F]fluorides, otherwise inaccessible via direct synthesis from amines, with high radiochemical yields up to 97% (30 examples). This late-stage labeling protocol offers an efficient route to yield functionalized molecules by diversifying the chemical library possessing sulfamoyl functionalities through nucleophilic 18F incorporation within nitrogen-containing sulfur(VI) frameworks.

LONP1 and ClpP cooperatively regulate mitochondrial proteostasis for cancer cell survival.

Mitochondrial proteases are key components in mitochondrial stress responses that maintain proteostasis and mitochondrial integrity in harsh environmental conditions, which leads to the acquisition of aggressive phenotypes, including chemoresistance and metastasis. However, the molecular mechanisms and exact role of mitochondrial proteases in cancer remain largely unexplored. Here, we identified functional crosstalk between LONP1 and ClpP, which are two mitochondrial matrix proteases that cooperate to attenuate proteotoxic stress and protect mitochondrial functions for cancer cell survival. LONP1 and ClpP genes closely localized on chromosome 19 and were co-expressed at high levels in most human cancers. Depletion of both genes synergistically attenuated cancer cell growth and induced cell death due to impaired mitochondrial functions and increased oxidative stress. Using mitochondrial matrix proteomic analysis with an engineered peroxidase (APEX)-mediated proximity biotinylation method, we identified the specific target substrates of these proteases, which were crucial components of mitochondrial functions, including oxidative phosphorylation, the TCA cycle, and amino acid and lipid metabolism. Furthermore, we found that LONP1 and ClpP shared many substrates, including serine hydroxymethyltransferase 2 (SHMT2). Inhibition of both LONP1 and ClpP additively increased the amount of unfolded SHMT2 protein and enhanced sensitivity to SHMT2 inhibitor, resulting in significantly reduced cell growth and increased cell death under metabolic stress. Additionally, prostate cancer patients with higher LONP1 and ClpP expression exhibited poorer survival. These results suggest that interventions targeting the mitochondrial proteostasis network via LONP1 and ClpP could be potential therapeutic strategies for cancer.

Analysing the mechanism of mitochondrial oxidation-induced cell death using a multifunctional iridium(III) photosensitiser.

Mitochondrial oxidation-induced cell death, a physiological process triggered by various cancer therapeutics to induce oxidative stress on tumours, has been challenging to investigate owing to the difficulties in generating mitochondria-specific oxidative stress and monitoring mitochondrial responses simultaneously. Accordingly, to the best of our knowledge, the relationship between mitochondrial protein oxidation via oxidative stress and the subsequent cell death-related biological phenomena has not been defined. Here, we developed a multifunctional iridium(III) photosensitiser, Ir-OA, capable of inducing substantial mitochondrial oxidative stress and monitoring the corresponding change in viscosity, polarity, and morphology. Photoactivation of Ir-OA triggers chemical modifications in mitochondrial protein-crosslinking and oxidation (i.e., oxidative phosphorylation complexes and channel and translocase proteins), leading to microenvironment changes, such as increased microviscosity and depolarisation. These changes are strongly related to cell death by inducing mitochondrial swelling with excessive fission and fusion. We suggest a potential mechanism from mitochondrial oxidative stress to cell death based on proteomic analyses and phenomenological observations.

Kap1 regulates the self-renewal of embryonic stem cells and cellular reprogramming by modulating Oct4 protein stability.

Oct4 plays a crucial role in the regulation of self-renewal of embryonic stem cells (ESCs) and reprogramming of somatic cells to induced pluripotent stem cells. However, the molecular mechanisms underlying posttranslational regulation and protein stability of Oct4 remain unclear. Using affinity purification and mass spectrometry analysis, we identified Kap1 as an Oct4-binding protein. Silencing of Kap1 reduced the protein levels of Oct4 in ESCs, whereas the overexpression of Kap1 stimulated the levels of Oct4. In addition, Kap1 overexpression stimulated the self-renewal of ESCs and attenuated the spontaneous differentiation of ESCs in response to LIF withdrawal. Kap1 overexpression increased the stability of Oct4 by inhibiting the Itch-mediated ubiquitination of Oct4. Silencing of Kap1 augmented Itch-mediated ubiquitination and inhibited the stability of Oct4. We identified the lysine 133 (K133) residue in Oct4 as a ubiquitination site responsible for the Kap1-Itch-dependent regulation of Oct4 stability. Preventing ubiquitination at the lysine residue by mutation to arginine augmented the reprogramming of mouse embryonic fibroblasts to induced pluripotent stem cells. These results suggest that Kap1 plays a crucial role in the regulation of the pluripotency of ESCs and somatic cell reprogramming by preventing Itch-mediated ubiquitination and the subsequent degradation of Oct4.