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Blood, 21 May 2009, Vol. 113, No. 21, pp. 5186-5191. Prepublished online as a Blood First Edition Paper on March 16, 2009; DOI 10.1182/blood-2008-11-187633. This Article Full Text (PDF) All Versions of this Article: blood-2008-11-187633v1 113/21/5186    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Rights and Permissions Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Tomaru, U. Articles by Kasahara, M. Search for Related Content PubMed PubMed Citation Articles by Tomaru, U. Articles by Kasahara, M. Social Bookmarking                   What's this?  Previous Article  |  Next Article  Submitted November 4, 2008 Accepted February 27, 2009 Exclusive expression of proteasome subunit 5t in the human thymic cortex Utano Tomaru*, Akihiro Ishizu, Shigeo Murata, Yukiko Miyatake, Sayuri Suzuki, Satomi Takahashi, Taku Kazamaki, Jiro Ohara, Tomohisa Baba, Sari Iwasaki, Kazunori Fugo, Noriyuki Otsuka, Keiji Tanaka, and Masanori Kasahara Department of Pathology, Hokkaido University Graduate School of Medicine, Sapporo, Japan Faculty of Health Sciences, Hokkaido University, Sapporo, Japan Laboratory of Protein Metabolism, Graduate School of Pharmaceutical Science, The University of Tokyo, Tokyo, Japan Division of Molecular Bioregulation, Cancer Research Institute, Kanazawa University, Kanazawa, Japan Laboratory of Frontier Science, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan * Corresponding author; email: tomaruu{at}med.hokudai.ac.jp. The ubiquitin-proteasome pathway, which degrades intracellular proteins, is involved in numerous cellular processes, including the supply of immunocompetent peptides to the antigen presenting machinery. Proteolysis by proteasomes is conducted by three subunits, 1, 2, and 5, of the 20S proteasome. Recently, a novel subunit expressed exclusively in cortical thymic epithelial cells was discovered in mice. This subunit, designated 5t, is a component of the thymoproteasome, a specialized type of proteasomes implicated in thymic positive selection. In this study, we show that, like its mouse counterpart, human 5t is expressed exclusively in the thymic cortex. Human 5t was expressed in approximately 80% of cortical thymic epithelial cells and some cortical dendritic cells. Human 5t was incorporated into proteasomes with two other catalytically active subunits 1i and 2i, forming 20S proteasomes with subunit compositions characteristic of thymoproteasomes. The present study demonstrates for the first time the existence of thymoproteasomes in the human thymic cortex, indicating that thymoproteasome function is likely conserved between humans and mice. CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

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