Molecular Cloning of a Novel Brain-Type Na+-Dependent Inorganic Phosphate Cotransporter

Authors

  • Yasuo Aihara,

    1. Laboratory of Molecular Genetics, Department of Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, Gunma, Japan
    2. Department of Neurosurgery, Neurological Institute, Tokyo Women’s Medical University, Tokyo, Japan
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  • Hirosato Mashima,

    1. Laboratory of Cell Physiology, Department of Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, Gunma, Japan
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  • Hideaki Onda,

    1. Laboratory of Molecular Genetics, Department of Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, Gunma, Japan
    2. Department of Neurosurgery, Neurological Institute, Tokyo Women’s Medical University, Tokyo, Japan
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  • Setsuji Hisano,

    1. Department of Anatomy, Institute of Basic Medical Sciences, University of Tsukuba, Ibaraki, Japan
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  • Hidetoshi Kasuya,

    1. Department of Neurosurgery, Neurological Institute, Tokyo Women’s Medical University, Tokyo, Japan
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  • Tomokatsu Hori,

    1. Department of Neurosurgery, Neurological Institute, Tokyo Women’s Medical University, Tokyo, Japan
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  • Shirou Yamada,

    1. Laboratory of Molecular Genetics, Department of Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, Gunma, Japan
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  • Hideaki Tomura,

    1. Laboratory of Molecular Genetics, Department of Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, Gunma, Japan
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  • Yuichiro Yamada,

    1. Department of Metabolism and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
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  • Ituro Inoue,

    1. Laboratory of Molecular Genetics, Department of Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, Gunma, Japan
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  • Itaru Kojima,

    1. Laboratory of Cell Physiology, Department of Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, Gunma, Japan
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  • Jun Takeda

    1. Laboratory of Molecular Genetics, Department of Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, Gunma, Japan
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  • Lippincott Williams & Wilkins, Inc., Philadelphia

  • Abbreviations used: BNPI, brain-specific Na+-dependent Pi cotransporter; DNPI, differentiation-associated Na+-dependent Pi cotransporter; Na+/Pi, Na+-dependent Pi.

Address correspondence and reprint requests to Dr. J. Takeda at Department of Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi, Gunma 371-8512 Japan. E-mail: jtakeda@akagi.sb.gunma-u.ac.jp

Abstract

Abstract: We have isolated a human cDNA encoding a protein, designated DNPI, that shows 82% amino acid identity and 92% similarity to the human brain-specific Na+-dependent inorganic phosphate (Na+/Pi) cotransporter (BNPI), which is localized exclusively to neuron-rich regions. Expression of DNPI mRNA in Xenopus oocytes resulted in a significant increase in Na+-dependent Pi transport, indicating that DNPI is a novel Na+/Pi cotransporter. Northern blot analysis shows that DNPI mRNA is expressed predominantly in brain, where the highest levels are observed in medulla, substantia nigra, subthalamic nucleus, and thalamus, all of which express BNPI mRNA at low levels. In contrast, DNPI mRNA is expressed at low levels in cerebellum and hippocampus, where BNPI mRNA is expressed at high levels. No hybridizing signal for DNPI mRNA is observed in the glia-rich region of corpus callosum. In other regions examined, both mRNAs are moderately or highly expressed. These results indicate that BNPI and DNPI, which coordinate Na+-dependent Pi transport in the neuron-rich regions of the brain, may form a new class within the Na+/Pi cotransporter family.

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