Biology subjects

Harata, M.

Publications and source records attributed to Harata, M..

6 recordsLinked to original sources

bioRxiv2025

Lipids Are Involved in Heterochromatin Condensation: A Quantitative Raman and Brillouin Microscopy Study

Chromatin, a fundamental component of eukaryotic genomes, is categorized into euchromatin and heterochromatin, which play distinct roles in gene regulation. Although these two chromatin states are distinguished by their degree of condensation, quantitatively measuring the degree of chromatin condensation, as well as the physical properties of chromatin in living cells, remains challenging. In this study, label-free in situ quantitative imaging was performed using a Raman-Brillouin microscope to visualize the spatial distribution of molecular concentration and viscoelasticity within the nuclear environment of a living cell. A quantitative concentration distribution image of each intracellular biomolecule was obtained by combining Raman imaging with multivariate curve resolution analysis, using a water Raman band as an internal standard. Simultaneous Raman-Brillouin imaging enables the quantitative visualization of viscoelasticity within a cell. Using this approach, we found that, in addition to DNA, heterochromatin is enriched in lipids and that lipids play a critical role in heterochromatin formation, determining its mechanical properties. These findings provide new insights into the mechanism of heterochromatin formation and its chemical and physical properties, leading to a comprehensive understanding of gene regulation and nuclear organization.

biophysics↗

bioRxiv2021

THz irradiation inhibits cell division by affecting actin dynamics

Biological phenomena induced by terahertz (THz) irradiation are described in recent reports, but underlying mechanisms, structural and dynamical change of specific molecules are still unclear. In this paper, we performed time-lapse morphological analysis of human cells and found that THz irradiation halts cell division at cytokinesis. At the end of cytokinesis, the contractile ring, which consists of filamentous actin (F-actin), needs to disappear; however, it remained for 1 hour under THz irradiation. Induction of the functional structures of F-actin was also observed in interphase cells. Similar phenomena were also observed under chemical treatment (jasplakinolide), indicating that THz irradiation assists actin polymerization. We previously reported that THz irradiation enhances the polymerization of purified actin in vitro; our current work shows that it increases cytoplasmic F-actin in vivo. Thus, we identified one of the key biomechanisms affected by THz waves.

cell biology↗

bioRxiv2021

Fundamental Role Of The H2A.Z C-Terminal Tail In The Formation Of Constitutive Heterochromatin

H2A.Z-nucleosomes are present in both euchromatin and heterochromatin and it has proven difficult to interpret their disparate roles in the context of their stability features. Using an in situ assay of nucleosome stability and DT40 cells expressing engineered forms of the histone variant we show that native H2A.Z, but not C-terminally truncated H2A.Z (H2A.Z{Delta}C), is released from nucleosomes of peripheral heterochromatin at unusually high salt concentrations. H2A.Z and H3K9me3 landscapes are reorganized in H2A.Z{Delta}C-nuclei and overall sensitivity of chromatin to nucleases is increased. These tail-dependent differences are recapitulated upon treatment of HeLa nuclei with the H2A.Z-tail-peptide (C9), with MNase sensitivity being increased at specific regions including promoters. Introduced into live cells C9 elicits down-regulation of [~]560 genes with nonrandom chromosomal band-localization and pathway-spectrum. Thus, tail-dependent heterogeneity of H2A.Z-nucleosomes is revealed at all organization levels of chromatin and epigenetic modulation can be achieved by targeting molecular interactions involving its C-terminal tail.

cell biology↗

bioRxiv2020

ADH5-mediated NO Bioactivity Maintains Metabolic Homeostasis in Brown Adipose Tissue

Brown adipose tissue (BAT) thermogenic activity is tightly regulated by cellular redox status but the molecular mechanisms underlying this regulation are incompletely understood. Protein S-nitrosylation, the nitric oxide-mediated cysteine thiol modification of proteins, plays important roles in cellular redox regulation. Here we show that both diet-induced obesity (DIO) and acute cold exposure elevates protein S-nitrosylation of BAT proteins, including UCP1, to regulate thermogenesis. This effect in BAT is regulated largely by S-nitrosoglutathione reductase (GSNOR, ADH5), a denitrosylase that balances the intracellular nitroso-redox status. Loss of ADH5 specifically in BAT impairs UCP1-dependent thermogenesis during acute cold challenge and worsens metabolic dysfunction during diet-induced obesity. Mechanistically, we demonstrate that Adh5 expression in BAT is controlled by the transcription factor heat shock factor 1 (HSF1) and administration of an HSF1 activator to the BAT of mice with DIO increased Adh5 expression and significantly improved UCP1-mediated mitochondrial respiration. Together, these data demonstrate that ADH5 controls BAT nitroso-redox homeostasis to regulate adipose thermogenesis which may be therapeutically targeted to improve metabolic health. HighlightsO_LIThermogenesis induces protein S-nitrosylation modification in the BAT; C_LIO_LIADH5, a major cellular denitrosylase, is required for maintaining BAT metabolic homeostasis under both overnutrition and cold stress conditions; C_LIO_LIDiet-induced obesity suppresses HSF1-mediated activation of Adh5 in the BAT; C_LIO_LIADH5 overexpression in BAT improves whole-body glucose homeostasis in obesity. C_LI

molecular biology↗

bioRxiv2020

Perilipin2 down-regulation in beta cells impairs insulin secretion under nutritional stress and damages mitochondria

Perilipin 2 (PLIN2) is the lipid droplet (LD) protein in {beta} cells that increases under nutritional stress. Down-regulation of PLIN2 is often sufficient to reduce LD accumulation. To determine whether PLIN2 positively or negatively affects {beta} cell function under nutritional stress, PLIN2 was down-regulated in mouse {beta} cells, INS1 cells, and human islet cells. {beta} cell specific deletion of PLIN2 in mice on a high fat diet reduced glucose-stimulated insulin secretion (GSIS) in vivo and in vitro. Down-regulation of PLIN2 in INS1 cells blunted GSIS after 24 h incubation with 0.2 mM palmitic acids. Down-regulation of PLIN2 in human pseudoislets cultured at 5.6 mM glucose impaired both phases of GSIS, indicating that PLIN2 is critical for GSIS. Down-regulation of PLIN2 decreased specific OXPHOS proteins in all three models and reduced oxygen consumption rates in INS1 cells and mouse islets. Moreover, we found that PLIN2 deficient INS1 cells increased the distribution of a fluorescent oleic acid analog to mitochondria and showed signs of mitochondrial stress as indicated by susceptibility to fragmentation and alterations of acyl-carnitines and glucose metabolites. Collectively, PLIN2 in {beta} cells have an important role in preserving insulin secretion, {beta} cell metabolism and mitochondrial function under nutritional stress.

molecular biology↗

bioRxiv2019

Propagation of THz irradiation energy through aqueous layers: Demolition of actin filaments in living cells

The effect of terahertz (THz) radiation on deep tissues of human body has been considered negligible due to strong absorption by water molecules. However, we observed that the energy of THz pulses transmits a millimeter thick in the aqueous solution, possibly as a shockwave, and demolishes actin filaments. Collapse of actin filament induced by THz irradiation was also observed in the living cells under an aqueous medium. We also confirmed that the viability of the cell was not affected under the exposure of THz pulses. The potential of THz waves as an invasive method to alter protein structure in the living cells is demonstrated. One sentence summaryThe energy of the THz wave propagates several millimeters into an aqueous medium and demolishes actin filaments via shockwaves.

cell biology↗