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Characterization of Two Distinct Monoclonal Antibodies to Paired Helical Filaments: Further Evidence for Fetal-Type Phosphorylation of the τ in Paired Helical Filaments

Authors

  • Masato Hasegawa,

    1. Department of Neuropathology, Institute for Brain Research, Faculty of Medicine, University of Tokyo, Tokyo
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  • Atsushi Watanabe,

    1. Department of Neuropathology, Institute for Brain Research, Faculty of Medicine, University of Tokyo, Tokyo
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  • Koji Takio,

    1. Division of Biomolecular Characterization, The Institute of Physical and Chemical Research (RIKEN), Saitama
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  • Masami Suzuki,

    1. Department of Neuropathology, Institute for Brain Research, Faculty of Medicine, University of Tokyo, Tokyo
    2. Division of Biomedical Polymer Science, Institute for Comprehensive Medical Science, School of Medicine, Fujita Health University, Aichi, Japan
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  • Takao Arai,

    1. Department of Applied Biological Science, Faculty of Science and Technology, Science University of Tokyo, Chiba
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  • Koiti Titani,

    1. Department of Neuropathology, Institute for Brain Research, Faculty of Medicine, University of Tokyo, Tokyo
    2. Division of Biomedical Polymer Science, Institute for Comprehensive Medical Science, School of Medicine, Fujita Health University, Aichi, Japan
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  • Yasuo Ihara

    Corresponding author
    1. Department of Neuropathology, Institute for Brain Research, Faculty of Medicine, University of Tokyo, Tokyo
      Address correspondence and reprint requests to Dr. Y. Ihara at Department of Neuropathology, Institute for Brain Research, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyoku, Tokyo 113, Japan.
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Address correspondence and reprint requests to Dr. Y. Ihara at Department of Neuropathology, Institute for Brain Research, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyoku, Tokyo 113, Japan.

Abstract

Abstract: Two monoclonal antibodies C5 and M4 raised against Sarkosyl-insoluble paired helical filaments (PHF) specifically labeled fetal τ, but hardly labeled normal adult τ. C5 immunoreactivity was eliminated by alkaline phosphatase treatment at 37°C, whereas M4 reactivity could be removed only by the treatment at 67°C. Epitope analysis showed that C5 and M4 recognition sites are in residues 386–406 and 198–250, respectively, according to the numbering of the longest human τ isoform. Thus, the phosphorylation sites are located in the amino- and carboxyl-terminal portions of the microtubule-binding region. These two well-characterized monoclonals should be valuable in the identification of a protein kinase(s) that converts normal τ into PHF-τ.

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