Biology subjects

Udagawa, O.

Publications and source records attributed to Udagawa, O..

6 recordsLinked to original sources

bioRxiv2026

Biological differences in promyelocytic leukemia (PML) proteins between PML-nuclear bodies (PML-NBs) and extranuclear PML bodies (EnPBs) in arsenite-exposed cells.

Promyelocytic leukemia (PML) proteins are known to form phase-separated nuclear punctate structures called PML-nuclear bodies (PML-NBs). The integrity disruption of PML-NBs is linked with the pathogenesis of acute promyelocytic leukemia (APL), and trivalent arsenic (As3+) has been used for the clinical treatment of APL to restore normal PML-NBs. As3+ is considered to bind to cysteine residues and enhances modification of PML with small-ubiquitin-like protein (SUMO). We exposed U-2OS and CHO-K1 cells stably overexpressing PML-VI to As3+ and found that the solubility of PML decreased and SUMOylation of PML increased after 2 h-exposure to 3 M As3+. Contrary to As3+-induced remarkable biochemical changes including the solubility change and SUMOylation of PML, microscopic observation of PML-NBs was not changed clearly after a short-term exposure to As3+. The number of PML-NBs decreased and extranuclear PML bodies (EnPBs), which are remniscences of PML-NBs after nuclear membrane breakdown at mitosis, increased after exposure to As3+ for 24 - 72 h. The amount of SUMOylated PML decreased after prolonged exposure to As3+ while the solubility of PML was kept low, suggesting that As3+ stabilized EnPB without SUMOylation. The effects of As3+ on EnPBs were clearly observed at as low as 0.3 M As3+ which corresponds to inorganic arsenic level in drinking water worldwide.

cell biology↗

bioRxiv2025

Whole-Tissue Distribution Analysis for Visualization of Nanoplastics in the Mouse Brain

Nanoplastics (NPs) are increasingly recognized as environmental contaminants and have been detected in diverse biological tissues; however, their biodistribution in complex organs remains poorly understood. Conventional section-based imaging restricts spatial context and volumetric analysis, making it challenging to map NP distribution in structurally complex organs such as the brain, even with fluorescent labeling. To address these limitations, we developed an integrated workflow combining tissue optical clearing (SeeDB2G) with light-sheet fluorescence microscopy (LSFM), enabling three-dimensional visualization of fluorescently labeled polystyrene (PS) NPs in neonatal mouse brains. At postnatal day 0 - a critical window of heightened vulnerability due to immature barrier systems and rapid neurodevelopment - pups were orally administered spherical PSNPs of 50 or 500 nm. Fluorescence stereoscopic imaging revealed pronounced organ-level accumulation of 50 nm PSNPs in the intestine, liver, kidney, and brain, compared with markedly lower signals from 500 nm PSNPs 24 h post-exposure. Optical clearing rendered the entire brain transparent while preserving fluorescence, allowing LSFM to accurately assess regional PSNP accumulation without sectioning. This workflow enabled whole-brain visualization of size-dependent NP uptake, with 50 nm PSNP detected throughout the brain and the highest accumulation observed in the thalamus and brainstem. Although the current implementation relies on fluorescent labeling and model NPs, this approach provides a scalable platform for whole-organ biodistribution analysis and lays the foundation for mechanistic studies of barrier permeability, developmental vulnerability, and organ-specific interactions.

pharmacology and toxicology↗

bioRxiv2024

Formation of stress granules and non-canonical survival responses in arsenite-exposed cells.

The concentration-dependent decrease in viable cells is a well-documented phenomenon in cytotoxicity assays for most toxic substances. We report that arsenite (As3+), a widely recognized oxidative toxicant, exhibited lower cytotoxic effects at 300 {micro}M compared to 100 {micro}M As3+ in CHO-K1 and Jurkat cells. Formation of stress granules (SGs), which appear in the cytoplasm shortly after exposure to hypertonicity, heat shock, and high concentrations of As3+ is considered as a pro-survival cellular event. We hypothesized that unusual cytotoxicity profile of As3+ could be attributed to SG formation. In both CHO-K1 and Jurkat cells stably expressing GFP-tagged G3BP1, SGs were more rapidly and distinctly induced by 300 {micro}M As3+ than 100 {micro}M As3+. Other toxic metals and a metalloid such as Cd2+, Cu2+, Ag+, and Se4+ did not clearly induce SG formation and instead reduced the viability in a concentration-dependent manner. Exposure to As3+ led to phosphorylation of eIF2, a key regulator of polysome stability and a hallmark of SG formation. Depletion of intracellular glutathione (GSH) increased the susceptibility of cells to As3+, highlighting its role in cellular defense mechanisms. Exposure to As3+ activated small ubiquitin-like modifier (SUMO) which is implicated in phase separation. However, neither depletion of GSH nor overexpression of SUMO contributed As3+-induced SG formation. Consistently, THP-1 and HL60 cells exposed to As3+ also exhibited non-canonical cytotoxic features, albeit at higher concentrations (1 mM). These findings underscore the need for further mechanistic investigations into As3+-induced SG formation, given that As3+ is a promising anti-cancer agent, and resistance of tumor cells to As3+ is a critical issue.

cell biology↗

bioRxiv2023

Arsenic induces two different interaction modes of SUMO with promyelocytic leukemia (PML) proteins.

Promyelocytic leukemia-nuclear bodies (PML-NBs) are dot-like protein assemblies and implicated in the pathogenesis of leukemia and viral infection. PML is the scaffold protein of PML-NB and its client proteins such as SUMO, DAXX, and Sp100 reside in PML-NBs. It is known that a short exposure to trivalent arsenic (As3+) induces the solubility change and the subsequent SUMOylation of PML, and the SUMO interacting motif (SIM) is not necessary for these biochemical changes. However, it has not been well studied how As3+ initiates or enhances the association of SUMO with PML and the other PML-NB client proteins. Here, we report that As3+ enhanced non-covalent association of PML with SUMO via the SUMO-SIM interaction which is dispensable for the solubility change and SUMOylation of PML. We also report that the As3+-induced solubility change of PML was not affected by ML792, a SUMO E1 enzyme inhibitor, even though the nuclear localization of SUMO2/3 and protein SUMOylation were halted by ML792. As3+ did not change the solubility of DAXX and SUMOylation enzymes such as SAE1, UBA2, and UBC9. In contrast, As3+ induced SUMOylation of Sp100 with a concomitant loss of its solubility like PML in human leukemia cell lines. Our current results indicate that both covalent and non-covalent associations of SUMO with PML are increased in As3+-exposed cells, and Sp100 may play a role in the maintenance of PML-NBs.

cell biology↗

bioRxiv2021

Promyelocytic leukemia nuclear body (PML-NB) -free intranuclear milieu facilitates development of oocytes in mice

Promyelocytic leukemia (PML) nuclear bodies (PML-NBs), a class of membrane-less organelles in cells, are involved in multiple biological activities and are present throughout cells of adult organisms. Although the oocyte nucleus is an active region for the flux of multiple non-membranous organelles, PML-NBs have been predicted to be absent from oocytes. Here, we show that the deliberate assembly of PML-NBs during oocyte growth preferentially sequestered Small Ubiquitin-related Modifier (SUMO) protein from the nucleoplasm. SUMO not only was involved in the regulation of oocyte nuclear maturation but also was committed to the response, mediated by liquid droplet formation, to multiple stressors including nucleolar stress and proteotoxic stresses. Exogenous assembly of PML-NBs in the nucleus of oocytes affected the efficiency of the response of SUMO. These observations suggest that the PML-NB-free intranuclear milieu ensures that a reserve of SUMO remains available for emergent responses in oocyte development. This work demonstrated a benefit of the PML-NB-free intranuclear milieu, namely the ability to redirect the flux of SUMO otherwise needed to control PML-NB dynamics.

developmental biology↗

bioRxiv2021

Effects of arsenic on the topology and solubility of promyelocytic leukemia (PML)-nuclear bodies

Promyelocytic leukemia (PML) proteins are involved in the pathogenesis of acute promyelocytic leukemia (APL). Trivalent arsenic (As3+) is known to cure APL by binding to cysteine residues of PML and enhance the degradation of PML-retinoic acid receptor (RAR), a t(15;17) gene translocation product in APL cells, and restore PML-nuclear bodies (NBs). The size, number, and shape of PML-NBs vary among cell types and during cell division. However, topological changes of PML-NBs in As3+-exposed cells have not been well-documented. We report that As3+-induced solubility shift underlies rapid SUMOylation of PML and late aggregation of PML-NBs. Most PML-NBs were toroidal and irregular-shaped in GFPPML-transduced CHO-K1 and HEK293 cells, respectively. The annular PML-NBs appeared unstable and dissipated into small PML-NBs in HEK cells. Exposure to As3+ and antimony (Sb3+) greatly reduced the solubility of PML and enhanced SUMOylation within 2 h, and prolonged exposure resulted in PML-NB agglomeration. Exposure to bismuth (Bi3+), another Group 15 element, did not induce any of these changes. ML792, a SUMO activation inhibitor, reduced the number of PML-NBs and increased the size of the NBs, but had little effect on the As3+-induced solubility change of PML. The results show that SUMOylation regulates the dynamics of PML-NBs but does not contribute to the As3+-induced solubility change of PML.

cell biology↗