Biology subjects

Motohashi, H.

Publications and source records attributed to Motohashi, H..

8 recordsLinked to original sources

bioRxiv2026

Epithelial Glutamate Retention Protects against Colitis

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract that encompasses ulcerative colitis and Crohns disease. Here we identify the cystine/glutamate antiporter xCT as being markedly upregulated in the inflamed intestinal epithelium of patients with IBD. To clarify its functional contribution to disease pathogenesis, we performed genetic loss-of-function study and found that inhibition of xCT confers robust protection against dextran sulfate sodium (DSS)-induced colitis in mice. Intestinal epithelial cell (IEC)-specific deletion of xCT markedly attenuated colitis severity, demonstrating that epithelial xCT upregulation acts as a disease-exacerbating factor in IBD. Mechanistically, xCT deficiency preserved intracellular glutamate levels and protein polyglutamylation, thereby maintaining epithelial barrier integrity and protecting IECs from inflammatory injury. Consistently, pharmacological inhibition of glutamine synthetase, which increases intracellular glutamate, exerted a potent anti-inflammatory effect on the DSS-induced colitis. These findings identify intracellular glutamate retention in IECs as a previously unrecognized mechanism of epithelial protection and highlight both inhibition of xCT-dependent glutamate efflux and suppression of glutamine synthetase as potential therapeutic strategies for IBD.

molecular biology↗

bioRxiv2026

Sulfide:quinone oxidoreductase drives mitochondrial supersulfide metabolism to regulate bioenergetics and longevity in eukaryotes

Sulfide:quinone oxidoreductase (SQR) is a critical enzyme that maintains sulfur metabolism by oxidizing sulfide to supersulfides, currently defined as sulfur metabolites with six valence electrons and no charge that are covalently catenated with other sulfur atoms and excludes disulfides. While SQR is known to contribute to mitochondrial electron transport, its physiological impact on systemic energy metabolism and longevity remains largely undefined. In this study, we investigated the role of SQR in mitochondrial bioenergetics and aging using SQR-deficient Schizosaccharomyces pombe ({Delta}hmt2) and a mitochondria-selective SQR-deficient (Sqrdl{Delta}N/{Delta}N) mice model. Functional analysis demonstrated that{Delta} hmt2 grew normally in glucose but not in glycerol, indicating impaired mitochondrial respiration. It showed reduced membrane potential, ATP, and lifespan. Consistent with the yeast findings, Sqrdl{Delta}N/{Delta}N mice exhibited accumulated levels of hydrogen sulfide and persulfides, and demonstrated impaired mitochondrial energy metabolism. Furthermore, supersulfide donor supplementation selectively conferred lifespan extension in wild-type yeast, but not in SQR-deficient strain, and similarly improved mitochondrial function exclusively in wild-type mouse embryonic fibroblasts, with no benefit observed in SQR-mutant counterparts. Together, our findings demonstrate that mitochondrial SQR plays an essential role in sulfur respiration, critically supporting mitochondrial function and organismal longevity across eukaryotes. Graphic Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=175 SRC="FIGDIR/small/716515v1_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@d834forg.highwire.dtl.DTLVardef@127dc7dorg.highwire.dtl.DTLVardef@1fccb8eorg.highwire.dtl.DTLVardef@197e910_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIDeveloped an SQR-deficient S. pombe ({Delta}hmt2) model that exhibits sulfur metabolism, mitochondrial dysfunction, and shortened chronological lifespan C_LIO_LISulfide and supersulfide donors prolong yeast lifespan in a SQR-dependent manner C_LIO_LIMitochondrial SQR is essential for membrane potential formation and ATP production in yeast and mammals C_LI

biochemistry↗

bioRxiv2025

Regnase-1 Promotes Tumor-Initiating Activity in Non-Small Cell Lung Cancer

Regnase-1, encoded by the ZC3H12A gene, is a well-known RNase that suppresses inflammation by degrading the mRNAs of inflammatory cytokines. However, its role in cancer pathogenesis, especially in non-small cell lung cancer (NSCLC), remains poorly understood. Through an analysis of public databases, we found that NSCLC patients with higher ZC3H12A expression levels had a worse prognosis than those with lower levels. To explore the function of Regnase-1 in NSCLC, we knocked out the ZC3H12A gene in NSCLC cell lines and compared their transcriptomes with those of parental cells. This analysis identified the SOX2 pathway as a common pathway suppressed by Regnase-1 deficiency. Consistent with the SOX2 contribution to the cancer stemness, Regnase-1 inhibition impaired oncosphere growth and tumor formation of cell lines derived from adenocarcinoma, squamous cell carcinoma and large cell carcinoma. It was also effective for NRF2-activated NSCLC cells, which are highly resistant to most of the therapeutics. Notably, post-tumorigenic suppression of Regnase-1 significantly inhibited tumor growth, suggesting that Regnase-1 could be a promising therapeutic target for post-tumorigenic treatment of NSCLC. Given recent studies describing that Regnase-1 inhibition enhances anti-cancer immunity, we propose that targeting Regnase-1 could be an ideal strategy for controlling intractable cancers by both suppressing cancer cells and activating anti-cancer immunity.

cancer biology↗

bioRxiv2024

Mitochondria Regulate the Cell Fate Decisions of Megakaryocyte-Erythroid Progenitors

Recent studies highlight the critical role of mitochondria in hematopoiesis, especially in stem cell function and erythroid maturation. To explore mitochondrial contributions to cell lineage commitment of hematopoietic progenitors, we utilized Cars2 mutant mice, an ideal model for this purpose. CARS2, a mitochondrial isoform of cysteinyl-tRNA synthetase, has cysteine persulfide synthase (CPERS) activity. Our new mouse model, with reduced CPERS activity, showed that the Cars2 mutation led to mitochondrial inhibition and anemia by suppressing erythroid commitment in megakaryocyte-erythroid progenitors (MEPs). This suppression was reproduced using mitochondrial electron transport chain inhibitors. We identified two distinct MEP populations based on the mitochondrial content: mitochondria-rich MEPs favored erythroid differentiation, while the mitochondria-poor MEPs favored megakaryocyte differentiation. These findings reveal critical contributions of mitochondria to the MEP lineage selection, acting as a "mitochondrial navigation" for lineage commitment.

cell biology↗

bioRxiv2024

Glutathione supersulphide regulates T-cell receptor signalling

Immunometabolism regulates functions and fates of immune cells including T cells. Supersulphides, which are universal metabolites containing catenated sulphur atoms, have various physiological functions based on their unique redox properties. Here we found that activation of T-cell receptor (TCR) signalling was accompanied by supersulphide decrease, which suggests a regulatory contribution of sulphur metabolism to immune function. Consistently, inhibiting supersulphide synthesis facilitated TCR activation and exacerbated allergen-induced type 2 inflammation in mice. Supplementation with glutathione trisulphide (GSSSG), a major endogenous supersulphide, suppressed TCR signalling in naive CD4+ T cells and their differentiation and effectively alleviated the inflammation. Docking simulation revealed interaction of GSSSG with CD3{varepsilon} chain in the TCR/CD3 complex, which was supported by mass spectrometry detection of persulphidated glutathionylation at a functionally important CXXC motif of CD3{varepsilon} chain. This study identified a new post-translational modification with supersulfides and demonstrated a critical contribution of sulphur metabolism to TCR signalling regulation.

biochemistry↗

bioRxiv2022

PNPO-PLP Axis Senses Prolonged Hypoxia by Regulating Lysosomal Activity

Oxygen is critical for all metazoan organisms on the earth and impacts various biological processes in physiological and pathological conditions. While oxygen sensing systems inducing acute hypoxic response, including HIF pathway, have been identified, those operating in prolonged hypoxia remain to be elucidated. Here, we show that pyridoxine 5-phosphate oxidase (PNPO) that catalyzes bioactivation of vitamin B6 serves as an oxygen sensor and regulates lysosomal activity in macrophages. Decline of PNPO activity under prolonged hypoxia reduced an active form of vitamin B6, pyridoxal 5-phosphate (PLP), and inhibited lysosomal activity, leading to the augmentation of inflammatory response of macrophages. The PNPO-PLP axis creates a distinct layer of oxygen sensing, which gradually turns down and up the PLP-dependent metabolism according to prolonged changes in oxygen availability.

biochemistry↗

bioRxiv2020

Enhancer Remodeling Promotes Tumor-Initiating Activity in NRF2-Activated Non-Small Cell Lung Cancers

Transcriptional dysregulation, which can be caused by genetic and epigenetic alterations, is a fundamental feature of many cancers. A key cytoprotective transcriptional activator, NRF2, is often aberrantly activated in non-small cell lung cancers (NSCLCs) and supports both aggressive tumorigenesis and therapeutic resistance. Herein, we found that persistently activated NRF2 in NSCLCs generates enhancers at gene loci that are not normally regulated by transiently activated NRF2 under physiological conditions. Elevated accumulation of CEBPB in NRF2-activated NSCLCs was found to be one of the prerequisites for establishment of the unique NRF2-dependent enhancers, among which NOTCH3 enhancer was shown to be critical for the promotion of tumor-initiating activity. Enhancer remodeling mediated by NRF2-CEBPB cooperativity promotes tumor-initiating activity and drives malignancy of NRF2-activated NSCLCs via establishment of the NRF2-NOTCH3 regulatory axis.

cancer biology↗

bioRxiv2018

Structural instability of IκB kinase β promotes autophagic degradation through enhancement of Keap1 binding

IKK{beta}, an essential kinase of NF-[kcy]B signaling, is composed of an N-terminal kinase domain (KD) and a C-terminal scaffolding domain, containing a ubiquitin-like domain (ULD). The Hsp90 chaperon has special responsibility for folding of protein kinases including IKK{beta}. Here, we found that Hsp90 inhibition induced IKK{beta} degradation, which is partially mediated by Keap1. Geldanamycin (GA), a Hsp90 inhibitor, enhances association of IKK{beta} with Keap1 through the binding site in KD, and translocates IKK{beta} to detergent-insoluble fractions leading its autophagic degradation. An electrophile tBHQ suppressed Keap1-mediated proteasomal Nrf2 degradation but not autophagic IKK{beta} degradation. Substitution mutation of Leu353 to Ala in the ULD destabilizes IKK{beta}, enhances its association with Keap1, translocates it to detergent-insoluble fractions, and causes its autophagic degradation. These results suggest that Keap1 is involved in the degradation of structural destabilized IKK{beta} and negative regulation of NF-[kcy]B under proteotoxic stress.

biochemistry↗