Biology subjects

Oda, T.

Publications and source records attributed to Oda, T..

At least 19 recordsLinked to original sources

bioRxiv2026

Microbiota-derived pantothenic acid rapidly restores colonic mucus barrier after antibiotic-induced dysbiosis

The intestinal mucus layer forms the primary physical barrier separating the host epithelium from the gut microbiota. Antibiotic-induced dysbiosis compromises this barrier, yet the microbial metabolites and host mechanisms responsible for its rapid restoration remain poorly understood. Here, we identify pantothenic acid (vitamin B5) as a microbial metabolite that rapidly restores colonic mucus integrity following antibiotic administration. Integrated 16S rRNA gene sequencing and metabolomic profiling of murine feces revealed a positive association between Muribaculaceae abundance, fecal pantothenic acid level, and colonic mucus thickness. Among four isolated Muribaculaceae species, only Sangeribacter muris produced pantothenic acid. An exogenous pantothenic acid supplement quickly restored the thin mucus layer. This rapid response occurred without detectable transcriptional activation. This response did not recur in isolated colonic epithelium or colonic organoids, indicating that pantothenic acid acts through a non-epithelial, non-autonomous mechanism. Together, these findings identify a previously unrecognized microbe-metabolite-host signaling pathway that rapidly regulates colonic mucus barrier homeostasis and reveal a local barrier-protective function of microbiota-derived pantothenic acid.

microbiology↗

bioRxiv2026

Tubulin Monoglutamylation is Sufficient to Rescue the Ciliary Motility Defects in a Chlamydomonas Polyglutamylation Deficient Mutant

The axonemes of eukaryotic cilia and flagella display high tubulin glutamylation heterogeneity, yet the functional significance of this variation remains elusive. We previously showed that long-chain polyglutamylation is crucial for ciliary motility in Chlamydomonas. However, the respective contributions of long-chain polyglutamylation versus short-chain species to motility remain unclear, as existing mutants did not allow for a clear functional dissection of these two modification states. Here, we generated mutants deficient in deglutamylases, cytosolic carboxypeptidases (CCPs) 1, 2, and 5. Importantly, CCP5 is known to remove the branch-point glutamate residue, the final step in deglutamylation. While axonemal polyglutamylation levels remained largely unaffected in these mutants, abundance of short-chain glutamylation was significantly increased in both the axonemal and cytoplasmic microtubules of ccp5-1, consistent with CCP5s role as a branch-point deglutamylase. Although each single mutant exhibited slightly reduced swimming velocity, the loss of CCP5 in the tpg1 background lacking long polyglutamate side chains resulted in a significant restoration of motility. These findings indicate that the abundance of short-chain species, regulated by CCP5, plays a distinct role in modulating ciliary motility, particularly in the absence of long polyglutamate side chains. This suggests that even minimal glutamylation can functionally support dynein-driven microtubule sliding.

cell biology↗

bioRxiv2026

Kinetic hierarchy of Kai protein complex formation governs the cyanobacterial circadian oscillator

Cyanobacterial circadian oscillations arise from a phosphorylation cycle of KaiC that is coupled to reversible complex formation with KaiA and KaiB. Although representative assemblies such as A2C6, B6C6, and A12B6C6 have been structurally characterized, quantitative understanding of their stoichiometry, affinity, and formation kinetics during the oscillation cycle remains limited. Here, we systematically quantified AC, BC and ABC complex formation using phosphorylation-mimetic KaiC and controlled protein mixing ratios by integrating analytical ultracentrifugation with small-angle X-ray/neutron scattering. A2C6 formation exhibits graded dependence on the phosphorylation state of KaiC and occurs rapidly in solution. In contrast, B6C6 formation behaves in a switch-like manner, showing strong selectivity for the hyperphosphorylation mimic and proceeding on a slow timescale ([~] 6 h). Upon B6C6 formation, KaiA rapidly associates with the complex to generate AnB6C6, with KaiA occupancy n determined by the mixing ratio through fast redistribution among coexisting complexes. This behavior enables dynamic allocation of KaiA among clock complexes. Together, these quantitative insights delineate a hierarchy of assembly dynamics--fast, graded AC exchange; slow, state-selective BC formation; and rapid KaiA redistribution--revealing a mechanistic basis for the dynamic regulation of the Kai oscillator.

biophysics↗

bioRxiv2025

Template-based RNA structure prediction advanced through a blind code competition

Automatically predicting RNA 3D structure from sequence remains an unsolved challenge in biology and biotechnology. Here, we describe a Kaggle code competition engaging over 1700 teams and 43 previously unreleased structures to tackle this challenge. The top three submitted algorithms achieved scores within statistical error of the winners of the recent CASP16 competition. Unexpectedly, the top Kaggle strategy involved a pipeline for discovering 3D templates, without the use of deep learning. We integrated this template-modeling pipeline and other Kaggle strategies to develop a single model RNAPro that retrospectively outperformed individual Kaggle models on the same test set. These results suggest a growing importance of template-based modeling in RNA structure prediction.

biophysics↗

bioRxiv2025

Tubulin Acetylation Deficiency Promotes Axonemal Turnover and Increases Cytoplasmic Microtubules

Tubulin post-translational modifications regulate microtubule dynamics; among these, -tubulin acetylation has been linked to microtubule stability. We generated a Chlamydomonas mutant lacking the acetyltransferase TAT1, which completely abolished -tubulin K40 acetylation. Surprisingly, the lengths of normally acetylated structures, axonemes and rootlets, were largely unaffected. TAT1 localized to the flagellar tip, suggesting that it is the primary site of acetylation. Loss of acetylation caused an increase in axonemal tubulin turnover, as revealed by dikaryon-fusion assays. Unexpectedly, the tat1 mutant displayed an increased number of dynamic cytoplasmic microtubules and could regenerate long flagella after amputation, even when protein synthesis was inhibited. Despite these cytoskeletal changes, steady-state flagellar length, cell growth, and cell division remained essentially normal. These findings suggest that acetylation modulates microtubule behavior by regulating axonemal tubulin turnover and cytoplasmic microtubule dynamics, while cellular morphology is buffered against variations in microtubule content.

cell biology↗

bioRxiv2025

Dotplotic: a lightweight visualization tool for BLAST+ alignments and genomic annotations

With the development of sequencing technologies, chromosome-level genome assemblies have become increasingly common across various organisms, including non-model species. BLAST+ is one of the most widely used bioinformatics tools for computing sequence alignments, offering numerous optimizations for speed and scalability. Dot plots, which visualize the similarity between two sequences, are widely used in biological research. However, while many dot plot-generating programs exist, most rely on their own alignment algorithms, and it is uncommon to visualize external BLAST results directly. Here, we present Dotplotic, a lightweight Perl program that generates dot plot-like visualizations based on BLAST output in tabular format. Dotplotic visualizes each alignment as a line connecting the start and end points of the query and subject sequences, with a gradient color indicating sequence identity. It allows users to overlay annotation data from external files onto the plot. Although command-line-based, Dotplotic requires only core Perl modules and is implemented as a single script, making it easy to install and run across platforms. The program supports standard input for both BLAST results and annotation files, enabling flexible visualization under various conditions, such as filtering specific alignments or displaying selected genomic features like genes or repeats. Dotplotic is an efficient, portable, and easy-to-use visualization tool that enhances the exploration of sequence alignments and serves as a valuable resource for both bioinformatics and broader biological research.

bioinformatics↗

bioRxiv2025

Membrane-enhanced repulsive interactions regulate protein diffusion in cell-size space

Intracellular molecular organization is often explained by attractive interactions driving clustering and phase separation. Although consideration of repulsive forces is essential in physics, their roles remain unclear in cellular contexts. Here, we demonstrated the fundamental role of repulsion in regulating protein diffusion within cell-size space. By analyzing negatively charged protein diffusion in bulk solutions and in cell-size spaces with membranes, we revealed that membrane-enhanced repulsion inhibited protein diffusion in cell-size spaces. This was due to the amplified electrostatic interactions among proteins because of the large membrane area-to-volume ratio. Notably, ATP, a cellular central energy source, further inhibited protein diffusion in cell-size spaces, whereas protein wave propagation on the membrane counteracted this inhibition. These findings suggest an active regulatory mechanism restoring molecular mobility by dynamically adjusting membrane-enhanced repulsive forces. Our study challenges the traditional emphasis on attractive interactions, highlighting repulsion as a critical tunable factor governing molecular transport and spatial organization in cells. TeaserProtein diffusion within crowded cell-size spaces is tuned by membrane-enhanced repulsion and its active regulation.

biophysics↗

bioRxiv2025

Microscopic and structural observations of actin filament capping and severing by Cytochalasin D

Cytochalasin D (CytoD) is widely used to inhibit actin polymerization, but the underlying regulatory mechanism is unclear. We addressed this using Total Internal Reflection Fluorescence (TIRF) microscopy. Our time course depolymerization assay of individual actin filaments showed that CytoD tightly caps the barbed end, with an estimated Km value for inhibition of 4.1 nM and a duration time of [~]1 min. Consistently, in polymerization assays, CytoD at concentrations near the Km value completely suppressed barbed end elongation. Interestingly, at lower concentrations, CytoD acted as a leaky capper, allowing actin monomer addition by rapidly binding to and dissociating from barbed ends. We interpreted this contradictory behavior as arising from differences in binding modes: capping one strand (fast dissociation) or both strands (slow dissociation). CytoD severs actin filaments at micromolar levels, a concentration range commonly used in cell biological studies. Although the severing rate is slower than cofilin, the frequency is higher, resulting in the fragmentation of filaments into shorter pieces. Severing activity was suppressed by inorganic phosphate or cofilin. We determined the crystal structure of CytoD bound to filamentous conformation (F-form) actin and found that CytoD fits better in the hydrophobic cleft of F-form actin than in the monomeric conformation actin, explaining the preferential binding towards barbed end subunits. The structure further indicates that CytoD prevents barbed end depolymerization by stabilizing the terminal subunits in the F-form, which is supported by our MD simulations. Collectively, our results demonstrate how CytoD regulates actin dynamics at the molecular level.

biophysics↗

bioRxiv2024

Cryo-EM of PMEL Amyloids Reveals Pathogenic Mechanism of Pigment Dispersion Syndrome

PMEL amyloids provide a vital scaffold for melanin deposition in melanosomes, playing a central role in pigmentation. Despite their importance, the high-resolution structure of PMEL amyloids has remained elusive. Here, we determined near-atomic resolution structures of wild-type PMEL amyloids using cryo-electron microscopy, revealing two distinct polymorphic forms with unique structural features. We further examined the pathogenic G175S mutation linked to pigment dispersion syndrome (PDS). Structural analysis showed that the G175S mutation introduces an additional hydrogen bond, stabilizing a novel fibril conformation. In vitro assays demonstrated a fourfold increase in polymerization efficiency for the G175S mutant compared to the wild-type. This enhanced polymerization correlated with a [~]70% increase in secreted amyloids in G175S-expressing cells without detectable changes in melanosome morphology or number. These findings suggest that the G175S mutation promotes amyloidogenesis within melanosomes, increasing amyloid load and contributing to PDS pathophysiology. This study provides insights into the molecular basis of PMEL amyloid formation in both physiological and pathological contexts, offering new perspectives on their structural diversity and dysregulation in pigmentation disorders.

cell biology↗

bioRxiv2024

Comprehensive gene expression analysis of organoid-derived healthy human colonic epithelium and cancer cell line by stimulated with live probiotic bacteria

The large intestine has a dense milieu of indigenous bacteria, generating a complex ecosystem with crosstalk between individual bacteria and host cells. In vitro host cell modeling and bacterial interactions at the anaerobic interphase have elucidated the crosstalk molecular basis. Although classical cell lines derived from patients with colorectal cancer including Caco-2 cells are used, whether they adequately mimic normal colonic epithelial physiology is unclear. To address this, we performed transcriptome profiling of Caco-2 and Monolayer cells derived from healthy Human Colonic Organoid (MHCO) cultured hemi-anaerobically. Coculture with the anaerobic gut bacteria, Bifidobacterium longum subsp. longum differentiated the probiotic effects of test cells from those of physiologically normal intestinal and colorectal cancer cells. We cataloged non- or overlapping gene signatures where gene profiles of Caco-2 cells represented absorptive cells in the small intestinal epithelium, and MHCO cells showed complete colonic epithelium signature, including stem/progenitor, goblet, and enteroendocrine cells colonocytes. Characteristic gene expression changes related to lipid metabolism, inflammation, and cell-cell adhesion were observed in cocultured live Bifidobacterium longum and Caco-2 or MHCO cells. B. longum-stimulated MHCO cells exhibited barrier-enhancing characteristics, as demonstrated in clinical trials. Our data represent a valuable resource for understanding gut microbe and host cell communication.

ecology↗

bioRxiv2024

SLC-25A46 Regulates Mitochondrial Fusion through FZO-1/Mitofusin and is Essential for Maintaining Neuronal Morphology

Mitochondria are dynamic organelles shaped by sequential fission and fusion events. The mitochondrial protein SLC25A46 has been identified as a causative gene for mitochondrial neuropathies. However, the function of SLC25A46 in mitochondrial morphogenesis remains controversial, with several reports suggesting it acts as a mitochondrial fission factor, while others propose it as a fusion factor. In this study, employing forward genetics, we identified slc-25A46, a Caenorhabditis elegans orthologue of human SLC25A46, as an essential factor for mitochondrial fusion. Suppressor mutagenesis screening revealed loss-of-function mutations in drp-1, a mitochondrial fission factor, as suppressors of slc-25A46. The phenotype of slc-25A46 mutants is similar to those of fzo-1 mutants, wherein the mitochondrial fusion factor Mitofusin is disrupted. Overexpressing FZO-1/Mitofusin mitigated mitochondrial defects in slc-25a46 mutants, indicating SLC-25A46 promotes fusion through FZO-1/Mitofusin. Disease model worms carrying mutations associated with SLC25A46 exhibited mitochondrial fragmentation and accelerated neurodegeneration, suggesting slc-25A46 maintains neuronal morphology through mitochondrial fusion regulation.

cell biology↗

bioRxiv2023

Molecular Mechanism of a FRET Biosensor for the Cardiac Ryanodine Receptor Pathologically Leaky State

Ca2+ leak from cardiomyocyte sarcoplasmic reticulum (SR) via hyperactive resting cardiac ryanodine receptor channels (RyR2) is pro-arrhythmic. An exogenous peptide, (DPc10) detects leaky RyR2 in cardiomyocytes. Conversely, calmodulin (CaM) inhibits RyR2 leak. These observations have led to designing a FRET biosensor for drug discovery targeting RyR2. Here we used FRET to understand the molecular mechanism driving the DPc10-CaM interdependence when binding RyR2 in SR vesicles. We used donor-FKBP12.6 (D-FKBP) to resolve RyR2 binding of acceptor-CaM (A-CaM). In low nanomolar Ca2+, DPc10 decreased both FRETmax (under saturating [A-CaM]) and the CaM/RyR2 binding affinity. In micromolar Ca2+, DPc10 decreased FRETmax without affecting CaM/RyR2 binding affinity. This correlates with analysis of fluorescence-lifetime-detected FRET indicating that DPc10 lowers occupancy of the RyR2 CaM-binding sites in nanomolar (not micromolar) Ca2+ and lengthens D-FKBP/A-CaM distances independent of [Ca2+]. To observe DPc10/RyR2 binding, we used acceptor-DPc10 (A-DPc10). CaM weakens A-DPc10/RyR2 binding, this effect being larger in micromolar vs. nanomolar Ca2+. Moreover, A-DPc10/RyR2 binding is cooperative in CaM- and FKBP-dependent manner, suggesting that both endogenous modulators promote concerted structural changes between RyR2 protomers for channel regulation. Aided by analysis of cryo-EM structures, these insights inform further development of the DPc10-CaM paradigm for therapeutic discovery targeting RyR2.

biophysics↗

bioRxiv2023

Unveiling Liquid-Crystalline Lipids in the Urothelial Membrane through Cryo-EM

The urothelium, a distinct epithelial tissue lining the urinary tract, serves as an essential component in preserving urinary tract integrity and thwarting infections. The asymmetric unit membrane (AUM), primarily composed of the uroplakin complex, constitutes a critical permeability barrier in fulfilling this role. However, the molecular architectures of both the AUM and the uroplakin complex have remained enigmatic due to the paucity of high-resolution structural data. In this study, we utilized cryo-electron microscopy to elucidate the three-dimensional structure of the uroplakin complex within the porcine AUM. While the global resolution achieved was 3.5 [A], we acknowledge that due to orientation bias, the resolution in the vertical direction was determined to be 6.3 [A]. Our findings unveiled that the uroplakin complexes are situated within hexagonally arranged crystalline lipid membrane domains, rich in hexosylceramides. Moreover, our research rectifies a misconception in a previous model by confirming the existence of a domain initially believed to be absent, and pinpointing the accurate location of a crucial Escherichia coli binding site implicated in urinary tract infections. These discoveries offer valuable insights into the molecular underpinnings governing the permeability barrier function of the urothelium and the orchestrated lipid phase formation within the plasma membrane.

biochemistry↗

bioRxiv2023

Distinct roles of α- and β-tubulin C-terminal tails for ciliary function as revealed by a CRISPR/Cas9 mediated gene editing in Chlamydomonas

- and {beta}-tubulin have an unstructured glutamate-rich region at their C-terminal tails (CTT). The function of this region in cilia/flagella is still unclear, except that glutamates in CTT act as the sites for posttranslational modifications that affect ciliary motility. A unicellular alga Chlamydomonas possesses only two -tubulin genes and two {beta}-tubulin genes, each pair encoding an identical protein. This simple gene organization may enable a complete replacement of the wild-type tubulin with its mutated version. Here, using CRISPR/Cas9, we generated mutants expressing tubulins with modified CTTs. We found that the mutant whose four glutamate residues in the -tubulin CTT have been replaced by alanine almost completely lacked polyglutamylated tubulin and displayed paralyzed cilia. In contrast, the mutant lacking the glutamate-rich region of the {beta}-tubulin CTT assembled short cilia without the central apparatus. This phenotype is similar to the mutants harboring a mutation in a subunit of katanin, whose function has been shown to depend on the {beta}-tubulin CTT. Therefore, our study reveals distinct and important roles of - and {beta}-tubulin CTT in the formation and function of cilia. Summary statementChlamydomonas mutants were produced by CRISPR/Cas9 mediated gene editing to investigate ciliary function of tubulin C-terminal tails (CTTs). We found that - and {beta}-tubulin CTTs are essential for ciliary motility and assembly.

cell biology↗

bioRxiv2022

Refinement of AlphaFold-Multimer structures with single sequence input

AlphaFold2, introduced by DeepMind in CASP14, demonstrated outstanding performance in predicting protein monomer structures. It could model more than 90% of targets with high accuracy, and so the next step would surely be multimer predictions, since many proteins do not act by themselves but with their binding partners. After the publication of AlphaFold2, DeepMind published AlphaFold-Multimer, which showed excellent performance in predicting multimeric structures. However, its accuracy still has room for improvement compared to that of monomer predictions by AlphaFold2. In this paper, we introduce a fine-tuned version of AlphaFold-Multimer, named AFM-Refine-G, which uses structures predicted by AlphaFold-Multimer as inputs and produces refined structures without the help of multiple sequence alignments or templates. The performance of AFM-Refine-G was assessed using four datasets: Ghani_et_al_Benchmark2 and Yin_et_al_Hard using AlphaFold-Multimer version 2.2 outputs, and CASP15_multimer and Yin_and_Pierce_af23 using AlphaFold-Multimer version 2.3 outputs. Of 1925 predicted structures, 203 had DockQ improvement > 0.05 after refinement, demonstrating that our model is useful for the refinement of multimer structures. However, considering the per target success rate, the overall improvement was modest, suggesting that the original AlphaFold-Multimer network had already learned a biophysical energy function independent of MSAs or templates, as proposed by Roney and Ovchinnikov (Roney and Ovchinnikov, 2022). Furthermore, both the default AlphaFold-Multimer and our refinement model showed lower performance for immune-related targets compared to general targets, indicating that room for improvement remains. AvailabilityThe inference scripts are available from https://github.com/t-oda-ic/afm_refiner under the Apache License, Version 2.0. The network parameters are available from https://figshare.com/articles/online_resource/afm_refine_g_20230110_zip/21856407 under the license CC BY 4.0.

bioinformatics↗

bioRxiv2022

ROR1 plays a critical role in pancreatic tumor-initiating cells with a partial EMT signature.

Tumor-initiating cells are the major drivers of chemoresistance and relapse, making them attractive targets for cancer therapy. However, the identity of tumor- initiating cells in human pancreatic ductal adenocarcinoma (PDAC) and the key molecules underlying their traits remain poorly understood. Here, we show that a partial epithelial-mesenchymal transition (EMT)-like subpopulation marked by high expression of receptor tyrosine kinase-like orphan receptor 1 (ROR1) is the origin of heterogeneous tumor cells in PDAC. We demonstrate that ROR1 depletion suppresses tumor growth, recurrence after chemotherapy, and metastasis. Mechanistically, ROR1 induces the expression of AURKB by activating E2F to enhance PDAC proliferation. Furthermore, epigenomic analyses reveal that ROR1 is transcriptionally dependent on YAP/BRD4 binding at the enhancer region, and targeting this pathway reduces ROR1 expression and prevents PDAC growth. Collectively, our findings reveal a critical role of ROR1high cells as tumor-initiating cells and the functional importance of ROR1 in PDAC progression, thereby highlighting its therapeutic targetability. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=192 HEIGHT=200 SRC="FIGDIR/small/499868v2_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@167bf72org.highwire.dtl.DTLVardef@49df52org.highwire.dtl.DTLVardef@1e480a3org.highwire.dtl.DTLVardef@b987bf_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2022

Chemical genetic screening identifies nalacin as an inhibitor of GH3 amido synthetase for auxin conjugation

Root system is critical for plant growth and development. To develop plant growth regulators functioning in root development, we performed a phenotype-based chemical screen in Arabidopsis and identified a chemical, nalacin, that mimicked the effects of auxin on root development. Genetic, pharmacological and biochemical approaches demonstrated that nalacin exerts its auxin-like activities by inhibiting indole-3-acetic acid (IAA) conjugation that is mediated by Gretchen Hagen 3 (GH3) acyl acid amido synthetases. The crystal structure of Arabidopsis GH3.6 in complex with D4 (a derivative of nalacin) together with docking simulation analysis revealed the molecular basis of the inhibition of group II GH3 by nalacin. Sequence alignment analysis indicated broad bioactivities of nalacin and D4 as inhibitors of GH3s in vascular plants, which were confirmed, at least, in tomato and rice. In summary, our work identifies nalacin as a potent inhibitor of IAA conjugation mediated by group II GH3 that plays versatile roles in hormone-regulated plant development and has potential applications in both basic research and agriculture.

plant biology↗

bioRxiv2022

Cryo-electron tomography of Birbeck granules reveals the molecular mechanism of langerin lattice formation

Langerhans cells are specialized antigen-presenting cells localized within the epidermis and mucosal epithelium. Upon contact with Langerhans cells, pathogens are captured by the C-type lectin langerin and internalized into a structurally unique vesicle known as a Birbeck granule. Although the immunological role of Langerhans cells and Birbeck granules have been extensively studied, the mechanism by which the characteristic zippered membrane structure of Birbeck granules is formed remains elusive. In this study, we observed isolated Birbeck granules using cryo-electron tomography and reconstructed the 3D structure of the repeating unit of the honeycomb lattice of langerin at 6.4 [A] resolution. We found that the interaction between the two langerin trimers was mediated by docking the flexible loop at residues 258-263 into the secondary carbohydrate-binding cleft. Mutations within the loop inhibited Birbeck granule formation and the internalization of HIV pseudovirus. These findings suggest a molecular mechanism for membrane zippering during Birbeck granule biogenesis and provide insight into the role of langerin in the defense against viral infection.

immunology↗