title: Endoplasmic reticulum chaperone GRP78 suppresses the aggregation of proteins containing expanded polyglutamine tract.
abstract: Polyglutamine (polyQ) diseases are inherited neurodegenerative diseases characterized by the aggregation of proteins containing expanded polyQ tract. It has been shown that expanded polyQ tract-containing proteins impair the functions of other cellular proteins. However, quantitative changes of cellular proteins in cells expressing expanded polyQ tract-containing proteins have not been performed. Here, we performed proteomic analysis of cells expressing expanded polyQ tract-containing proteins, and showed that GRP78, the endoplasmic reticulum (ER) chaperone, was significantly decreased in the cells expressing enhanced green fluorescent protein with a pathological-length polyQ tract (EGFP-polyQ97), but not with a non-pathological-length polyQ tract (EGFP-polyQ24). In addition, we revealed that down-regulation of GRP78 expression resulted in increase of the aggregation of EGFP-polyQ97. Conversely, the aggregation of EGFP-polyQ97 was suppressed by the overexpression of GRP78 in the cells. Furthermore, it seemed that the decreased GRP78 expression in the cells expressing EGFP-polyQ97 was due to the enhanced protein degradation of GRP78 through the ubiquitin-proteasome pathway. These findings indicated that GRP78, which has an inhibitory effect on the aggregation of proteins containing expanded polyQ tract, may be an effective target for the treatment of polyQ diseases.
authors.affiliation: Department of Biochemistry & Molecular Biology, Division of Biological Sciences, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan. yamagisi@mb.kyoto-phu.ac.jp
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Yamagishi
authors.forename: Shoichi
authors.initials: S
authors.lastname: Magara
authors.forename: Satoko
authors.initials: S
authors.lastname: Tamura
authors.forename: Youhei
authors.initials: Y
authors.lastname: Saito
authors.forename: Takumi
authors.initials: T
authors.lastname: Hatayama
mesh_terms: D004721:Endoplasmic Reticulum / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D055785:Gene Knockdown Techniques; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D010455:Peptides / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D059748:Proteolysis; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D010455:Peptides; D025801:Ubiquitin; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; C097188:polyglutamine; D046988:Proteasome Endopeptidase Complex