Characterization of a Novel Mammalian Co-chaperone, DnaJB7, an HSP40 Family Member

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  • TAKEUCHI RIKA
    Laboratory of Cell & Stress Biology, Department of Environmental Biology, Chubu University
  • SOGA MINORU
    Laboratory of Cell & Stress Biology, Department of Environmental Biology, Chubu University
  • INAGUMA YUTAKA
    Laboratory of Molecular Neurobiology, Institute of Developmental Research, Aichi Human Service Center
  • OHTSUKA KENZO
    Laboratory of Cell & Stress Biology, Department of Environmental Biology, Chubu University

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  • HSP40ファミリーメンバーである哺乳類の新規シャペロン補助因子DnaJB7の特性解析

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Abstract

Molecular chaperones of HSP70 family members usually work together with HSP40/DNAJ family members in protein biogenesis and protein homeostasis. In mammals, approximately 50 members of the HSP40/DNAJ family are identified so far. Here, we isolated a cDNA clone of DnaJB7, one of the HSP40/DNAJ family members, and examined the properties of DnaJB7 protein in vivo and in vitro . Since the DnaJB7 gene in the human genome has no obvious heat shock element (HSE), DnaJB7 could not be induced by heat shock in HeLa cells. While overexpressed DnaJB7 in HeLa cells was distributed to both the cytoplasm and nucleolus at normal temperature, upon heat shock it accumulated in the nucleolus, where it co-localized with Hsp70. This localization pattern was very similar to that of Hsp40 (DnaJB1). Direct interaction of Hsp70 with DnaJB7 in HeLa cells was demonstrated by immunoprecipitation. Also, DnaJB7 could stimulate the ATPase activity of Hsp70. Hsp70 had molecular chaperone activity in suppressing aggregation of heat denatured luciferase, and DnaJB7 could facilitate the chaperone activity of Hsp70. In murine tissues, DnaJB7 was highly expressed in the stomach and faintly in pancreas, uterus and ovary. These results suggest that DnaJB7 is a stomach-enriched co-chaperone of Hsp70.

Journal

  • Thermal Medicine

    Thermal Medicine 27 (1), 9-23, 2010

    Japanese Society for Thermal Medicine

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