Proceedings of the National Academy of Sciences Acta Medica Okayama 0027-8424 123 17 2026 A magnesium efflux transporter required for seed development and eating quality in rice e2536813123 EN Sheng Huang Institute of Plant Science and Resources, Okayama University Kiyosumi Hori National Institute of Crop Science, National Agriculture Research Organization Naoki Yamaji Institute of Plant Science and Resources, Okayama University Yuma Yoshioka Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Min Ning Institute of Plant Science and Resources, Okayama University Yu Nagaya Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Takaaki Miyaji Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Namiki Mitani-Ueno Institute of Plant Science and Resources, Okayama University Shin-ichiro Inoue Department of Regulatory Biology, Saitama University June-Sik Kim Institute of Plant Science and Resources, Okayama University Miho Kashino Institute of Plant Science and Resources, Okayama University Jian Feng Ma Institute of Plant Science and Resources, Okayama University As a staple food for half the world’s population, rice is an important dietary source of magnesium (Mg), an essential mineral for human health. Enhanced Mg accumulation in rice grains has also been linked to eating quality. However, the mechanisms underlying Mg transport to the grains remains poorly understood. Here, we report that OsMGR2, a member belonging to Magnesium Release (MGR) family, is required for Mg accumulation in rice grains. OsMGR2 encodes a plasma membrane-localized transporter that mediates Mg efflux. OsMGR2 is constitutively and highly expressed in the stele tissues of roots, the phloem region of both enlarged and diffused vascular bundles in nodes, and the ovular vascular trace of caryopses. Knockout of this gene results in decreased root-to-shoot translocation and altered distribution of Mg to different organs; less Mg is allocated to the second newest leaf with high Mg requirement for active photosynthesis. The osmgr2 mutants exhibit decreased Mg accumulation in the grain, which are smaller, lighter, and shriveled, but show increased accumulation in the husk. The eating quality of the mutant grains is significantly decreased compared with the wild-type rice. These results indicate that OsMGR2 plays multiple roles within the rice; facilitating the root-to-shoot Mg translocation, mediating phloem-to-xylem Mg transfer at nodes for preferential distribution to the most active leaf, and exporting Mg from maternal vascular tissues of the caryopsis to the grains, processes essential for grain development and eating quality in rice. No potential conflict of interest relevant to this article was reported.

Pharmaceutical Society of Japan Acta Medica Okayama 0918-6158 49 2 2026 Functional Transport Properties of Human Zinc Transporter 1: Kinetics and pH-Dependency 364 370 EN Yuma Yoshioka Department of Molecular Membrane Biology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Takaaki Miyaji Department of Molecular Membrane Biology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Intracellular zinc (Zn2+) homeostasis is essential for physiological and pathological processes and is strictly regulated by Zn2+ transporters. Zinc transporter 1 (ZnT1) is a ubiquitously expressed plasma membrane-localized Zn transporter that exports Zn2+ from the cytoplasm to the extracellular space. However, the functional transport properties regarding kinetics and driving forces of ZnT1 remain debatable. In this study, we established a cell-free proteoliposome assay system and demonstrated that ZnT1 transports Zn2+ with high affinity in pH-dependent and pH-independent manners. The Km and Vmax of pH-dependent Zn2+ transport were 0.40 μM and 15.13 nmol/min/mg protein, and those of pH-independent Zn2+ transport were 0.52 μM and 8.88 nmol/min/mg protein (low concentrations of Zn2+), 3.02 μM and 17.59 nmol/min/mg protein (high concentrations of Zn2+), respectively, suggesting biphasic kinetic components of Zn2+ transport. Even without pH gradient formation, ZnT1 exhibits potent Zn2+ transport activity. In pH dependency, Zn2+ transport activity was higher at an inside pH of 6.0 than at 6.5–7.5 for proteoliposomes, despite the same ΔpH of 0.5–1.5. The Zn2+ transport activity decreased at an outside pH of 8.0, despite an increase in ΔpH. Although previous studies have proposed that ZnT1-mediated Zn2+ transport activity is driven by a calcium (Ca2+) gradient and not by a pH gradient, Ca2+ does not enhance Zn2+ transport activity in the presence or absence of a pH gradient. These results strongly suggest that ZnT1 protein transports Zn2+ optimally at a specific pH and exports excess intracellular Zn2+ even without ΔpH. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 2041-1723 16 1 2025 A node-localized efflux transporter for loading iron to developing tissues in rice 9916 EN Jing Che Institute of Plant Science and Resources, Okayama University Sheng Huang Institute of Plant Science and Resources, Okayama University Yuting Qu State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences Yuma Yoshioka Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Chiyuri Tomita Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Takaaki Miyaji Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Zhenyang Liu State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences Renfang Shen State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences Naoki Yamaji Institute of Plant Science and Resources, Okayama University Jian Feng Ma Institute of Plant Science and Resources, Okayama University Iron (Fe) is an essential micronutrient for plant growth and development. It plays crucial roles in various organs and tissues of plants, but the molecular mechanisms governing its distribution to the above-ground parts after root uptake remain unclear. In this study, we identify OsIET1 (Oryza sativa Iron Efflux Transporter 1), a rice gene highly expressed in the nodes. OsIET1 encodes a plasma membrane-localized protein, which shows efflux transport activity for ferrous iron. It is predominantly expressed in the xylem regions of diffuse vascular bundles, and its expression is upregulated under high Fe conditions. Disruption of OsIET1 impairs Fe allocation, reducing Fe transport to developing tissues (young leaves and grains), while increasing accumulation in nodes and older leaves. This misdistribution causes chlorosis in young leaves and decreases grain yield, especially under Fe-deficient conditions. Furthermore, we detect excessive Fe deposition around the xylem of diffuse vascular bundles in the nodes. Given the pivotal role of nodes in mineral distribution, our results indicate that OsIET1 mediates inter-vascular Fe transfer by facilitating Fe loading into the xylem of diffuse vascular bundles. This process ensures preferential Fe delivery to developing tissues, thereby promoting optimal plant growth and productivity. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 2041-1723 15 1 2024 Neurotransmitter recognition by human vesicular monoamine transporter 2 7661 EN Dohyun Im Department of Cell Biology, Graduate School of Medicine, Kyoto University Mika Jormakka Department of Cell Biology, Graduate School of Medicine, Kyoto University Narinobu Juge Department of Genomics and Proteomics, Advanced Science Research Center, Okayama University Jun-ichi Kishikawa Department of Applied Biology, Kyoto Institute of Technology Takayuki Kato Institute for Protein Research, Osaka University Yukihiko Sugita Laboratory of Ultrastructural Virology, Institute for Life and Medical Sciences, Kyoto University Takeshi Noda Laboratory of Ultrastructural Virology, Institute for Life and Medical Sciences, Kyoto University Tomoko Uemura Department of Cell Biology, Graduate School of Medicine, Kyoto University Yuki Shiimura Department of Cell Biology, Graduate School of Medicine, Kyoto University Takaaki Miyaji Department of Genomics and Proteomics, Advanced Science Research Center, Okayama University Hidetsugu Asada Department of Cell Biology, Graduate School of Medicine, Kyoto University So Iwata Department of Cell Biology, Graduate School of Medicine, Kyoto University Human vesicular monoamine transporter 2 (VMAT2), a member of the SLC18 family, plays a crucial role in regulating neurotransmitters in the brain by facilitating their uptake and storage within vesicles, preparing them for exocytotic release. Because of its central role in neurotransmitter signalling and neuroprotection, VMAT2 is a target for neurodegenerative diseases and movement disorders, with its inhibitor being used as therapeutics. Despite the importance of VMAT2 in pharmacophysiology, the molecular basis of VMAT2-mediated neurotransmitter transport and its inhibition remains unclear. Here we show the cryo-electron microscopy structure of VMAT2 in the substrate-free state, in complex with the neurotransmitter dopamine, and in complex with the inhibitor tetrabenazine. In addition to these structural determinations, monoamine uptake assays, mutational studies, and pKa value predictions were performed to characterize the dynamic changes in VMAT2 structure. These results provide a structural basis for understanding VMAT2-mediated vesicular transport of neurotransmitters and a platform for modulation of current inhibitor design. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 1661-6596 26 6 2025 Vesicular Glutamate Transporter 3 Is Involved in Glutamatergic Signalling in Podocytes 2485 EN Naoko Nishii Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Tomoko Kawai Department of Cell Physiology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Hiroki Yasuoka Department of Neuroscience, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Tadashi Abe Department of Neuroscience, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Nanami Tatsumi Department of Neuroscience, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Yuika Harada Department of Genomics and Proteomics, Advanced Science Research Center, Okayama University Takaaki Miyaji Department of Genomics and Proteomics, Advanced Science Research Center, Okayama University Shunai Li Center for Innovative Clinical Medicine, Okayama University Hospital Moemi Tsukano Central Research Laboratory, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Masami Watanabe Center for Innovative Clinical Medicine, Okayama University Hospital Daisuke Ogawa Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Jun Wada Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Kohji Takei Department of Neuroscience, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Hiroshi Yamada Department of Neuroscience, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Glomerular podocytes act as a part of the filtration barrier in the kidney. The activity of this filter is regulated by ionotropic and metabotropic glutamate receptors. Adjacent podocytes can potentially release glutamate into the intercellular space; however, little is known about how podocytes release glutamate. Here, we demonstrated vesicular glutamate transporter 3 (VGLUT3)-dependent glutamate release from podocytes. Immunofluorescence analysis revealed that rat glomerular podocytes and an immortal mouse podocyte cell line (MPC) express VGLUT1 and VGLUT3. Consistent with this finding, quantitative RT-PCR revealed the expression of VGLUT1 and VGLUT3 mRNA in undifferentiated and differentiated MPCs. In addition, the exocytotic proteins vesicle-associated membrane protein 2, synapsin 1, and synaptophysin 1 were present in punctate patterns and colocalized with VGLUT3 in MPCs. Interestingly, approximately 30% of VGLUT3 colocalized with VGLUT1. By immunoelectron microscopy, VGLUT3 was often observed around clear vesicle-like structures in differentiated MPCs. Differentiated MPCs released glutamate following depolarization with high potassium levels and after stimulation with the muscarinic agonist pilocarpine. The depletion of VGLUT3 in MPCs by RNA interference reduced depolarization-dependent glutamate release. These results strongly suggest that VGLUT3 is involved in glutamatergic signalling in podocytes and may be a new drug target for various kidney diseases. No potential conflict of interest relevant to this article was reported.

Okayama University Medical School Acta Medica Okayama 0386-300X 78 5 2024 Effect of Radon Inhalation on Murine Brain Proteins: Investigation Using Proteomic and Multivariate Analyses 387 399 EN Shota Naoe Graduate School of Health Sciences, Okayama University Ayumi Tanaka Graduate School of Health Sciences, Okayama University Norie Kanzaki Ningyo-toge Environmental Engineering Center, Japan Atomic Energy Agency Reiju Takenaka Graduate School of Health Sciences, Okayama University Akihiro Sakoda Ningyo-toge Environmental Engineering Center, Japan Atomic Energy Agency Takaaki Miyaji Advanced Science Research Center, Okayama University Kiyonori Yamaoka Faculty of Health Sciences, Okayama University Takahiro Kataoka Faculty of Health Sciences, Okayama University Original Article 10.18926/AMO/67663 Radon is a known risk factor for lung cancer; however, it can be used beneficially, such as in radon therapy. We have previously reported the enhancement of antioxidant effects associated with trace amounts of oxidative stress as one of the positive biological effects of radon inhalation. However, the biological effects of radon inhalation are incompletely understood, and more detailed and comprehensive studies are required. Although several studies have used proteomics to investigate the effects of radon inhalation on body proteins, none has focused on brain proteins. In this study, we evaluated the expression status of proteins in murine brains using proteomic and multivariate analyses to identify those whose expressions changed following two days of radon inhalation at a concentration of 1,500 Bq/m3. We found associations of radon inhalation with the expressions of seven proteins related to neurotransmission and heat shock. These proteins may be proposed as biomarkers indicative of radon inhalation. Although further studies are required to obtain the detailed biological significance of these protein alterations, this study contributes to the elucidation of the biological effects of radon inhalation as a low-dose radiation. No potential conflict of interest relevant to this article was reported.

Nature Publishing Group Acta Medica Okayama 2041-1723 6 2015 AtPHT4;4 is a chloroplast-localized ascorbate transporter in Arabidopsis EN Takaaki Miyaji Takashi Kuromori Yu Takeuchi Naoki Yamaji Kengo Yokosho Atsushi Shimazawa Eriko Sugimoto Hiroshi Omote Jian Feng Ma Kazuo Shinozaki Yoshinori Moriyama Ascorbate is an antioxidant and coenzyme for various metabolic reactions in vivo. In plant chloroplasts, high ascorbate levels are required to overcome photoinhibition caused by strong light. However, ascorbate is synthesized in the mitochondria and the molecular mechanisms underlying ascorbate transport into chloroplasts are unknown. Here we show that AtPHT4;4, a member of the phosphate transporter 4 family of Arabidopsis thaliana, functions as an ascorbate transporter. In vitro analysis shows that proteoliposomes containing the purified AtPHT4;4 protein exhibit membrane potential- and Cl-dependent ascorbate uptake. The AtPHT4;4 protein is abundantly expressed in the chloroplast envelope membrane. Knockout of AtPHT4;4 results in decreased levels of the reduced form of ascorbate in the leaves and the heat dissipation process of excessive energy during photosynthesis is compromised. Taken together, these observations indicate that the AtPHT4;4 protein is an ascorbate transporter at the chloroplast envelope membrane, which may be required for tolerance to strong light stress. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 2045-2322 4 2014 Identification of a mammalian vesicular polyamine transporter EN Miki Hiasa Takaaki Miyaji Yuka Haruna Tomoya Takeuchi Yuika Harada Sawako Moriyama Akitsugu Yamamoto Hiroshi Omote Yoshinori Moriyama Spermine and spermidine act as neuromodulators upon binding to the extracellular site(s) of various ionotropic receptors, such as N-methyl-d-aspartate receptors. To gain access to the receptors, polyamines synthesized in neurons and astrocytes are stored in secretory vesicles and released upon depolarization. Although vesicular storage is mediated in an ATP-dependent, reserpine-sensitive fashion, the transporter responsible for this process remains unknown. SLC18B1 is the fourth member of the SLC18 transporter family, which includes vesicular monoamine transporters and vesicular acetylcholine transporter. Proteoliposomes containing purified human SLC18B1 protein actively transport spermine and spermidine by exchange of H+. SLC18B1 protein is predominantly expressed in the hippocampus and is associated with vesicles in astrocytes. SLC18B1 gene knockdown decreased both SLC18B1 protein and spermine/spermidine contents in astrocytes. These results indicated that SLC18B1 encodes a vesicular polyamine transporter (VPAT). No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 105 15 2008 Identification of a vesicular nucleotide transporter 5683 5686 EN Keisuke Sawada Noriko Echigo Narinobu Juge Takaaki Miyaji Masato Otsuka Hiroshi Omote Akitsugu Yamamoto Yoshinori Moriyama <p>ATP is a major chemical transmitter in purinergic signal transmission. Before secretion, ATP is stored in secretory vesicles found in purinergic cells. Although the presence of active transport mechanisms for ATP has been postulated for a long time, the proteins responsible for its vesicular accumulation remains unknown. The transporter encoded by the human and mouse SLC17A9 gene, a novel member of an anion transporter family, was predominantly expressed in the brain and adrenal gland. The mouse and bovine counterparts were associated with adrenal chromaffin granules. Proteoliposomes containing purified transporter actively took up ATP, ADP, and GTP by using membrane potential as the driving force. The uptake properties of the reconstituted transporter were similar to that of the ATP uptake by synaptic vesicles and chromaffin granules. Suppression of endogenous SLC17A9 expression in PC12 cells decreased exocytosis of ATP. These findings strongly suggest that SLC17A9 protein is a vesicular nucleotide transporter and should lead to the elucidation of the molecular mechanism of ATP secretion in purinergic signal transmission. </p> No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 2009 小胞型アスパラギン酸トランスポーターの発見とその生理的意義について EN Takaaki Miyaji No potential conflict of interest relevant to this article was reported.