Hsp90-mediated assembly of the 26 S proteasome is involved in major histocompatibility complex class I antigen processing

Taketoshi Yamano, Shusaku Mizukami, Shigeo Murata, Tomoki Chiba, Keiji Tanaka, Heiichiro Udono


35 被引用数 (Scopus)


Heat shock protein 90 (hsp90) and the proteasome activator PA28 stimulate major histocompatibility complex (MHC) class I antigen processing. It is unknown whether hsp90 influences the proteasome activity to produce T cell epitopes, although association of PA28 with the 20 S proteasome stimulates the enzyme activity. Here, we show that hsp90 is essential in assembly of the 26 S proteasome and as a result, is involved in epitope production. Addition of recombinant hsp90α to cell lysate enhanced chymotrypsin-like activity of the 26 S proteasome in an ATP-dependent manner as determined by an in-gel hydrolysis assay. We successfully pulled down histidine-tagged hsp90α- and PA28α-induced, newly assembled 26 S proteasomes from the cell extracts for in vitro epitope production assay, and we found these structures to be sensitive to geldanamycin, an hsp90 inhibitor. We found a cleaved epitope unique to the proteasome pulled down by both hsp90α and PA28α, whereas two different epitopes were identified in the hsp90α- and PA28α-pulldowns, respectively. Processing of these respective peptides in vivo was enhanced faithfully by the protein combinations used for the proteasome pulldowns. Inhibition of hsp90 in vivo by geldanamycin partly disrupted the 26 S proteasome structure, consistent with down-regulated MHC class I expression. Our results indicate that hsp90 facilitates MHC class I antigen processing through epitope production in a complex of the 26 S proteasome.

ジャーナルJournal of Biological Chemistry
出版ステータスPublished - 10月 17 2008

ASJC Scopus subject areas

  • 生化学
  • 分子生物学
  • 細胞生物学


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