A human PSMB11 variant affects thymoproteasome processing and CD8+ T cell production
Izumi Ohigashi ... Shigeo Murata, Yousuke Takahama
Izumi Ohigashi ... Shigeo Murata, Yousuke Takahama
Published May 18, 2017
Citation Information: JCI Insight. 2017;2(10):e93664. doi:10.1172/jci.insight.93664.
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Categories: Research Article Genetics Immunology

A human PSMB11 variant affects thymoproteasome processing and CD8+ T cell production

Abstract

The Psmb11-encoded β5t subunit of the thymoproteasome, which is specifically expressed in cortical thymic epithelial cells (cTECs), is essential for the optimal positive selection of functionally competent CD8+ T cells in mice. Here, we report that a human genomic PSMB11 variation, which is detectable at an appreciable allele frequency in human populations, alters the β5t amino acid sequence that affects the processing of catalytically active β5t proteins. The introduction of this variation in the mouse genome revealed that the heterozygotes showed reduced β5t expression in cTECs and the homozygotes further exhibited reduction in the cellularity of CD8+ T cells. No severe health problems were noticed in many heterozygous and 5 homozygous human individuals. Long-term analysis of health status, particularly in the homozygotes, is expected to improve our understanding of the role of the thymoproteasome-dependent positive selection of CD8+ T cells in humans.

Authors

Izumi Ohigashi, Yuki Ohte, Kazuya Setoh, Hiroshi Nakase, Akiko Maekawa, Hiroshi Kiyonari, Yoko Hamazaki, Miho Sekai, Tetsuo Sudo, Yasuharu Tabara, Hiromi Sawai, Yosuke Omae, Rika Yuliwulandari, Yasuhito Tanaka, Masashi Mizokami, Hiroshi Inoue, Masanori Kasahara, Nagahiro Minato, Katsushi Tokunaga, Keiji Tanaka, Fumihiko Matsuda, Shigeo Murata, Yousuke Takahama

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G49S variation affects processing of human and mouse β5t protein. (A) WT...

Figure 1

G49S variation affects processing of human and mouse β5t protein.

(A) WT (hβ5t WT-Flag) and G49S (hβ5t G49S-Flag) human β5t tagged at C-terminus with the Flag epitope was transfected into HEK293T cells. Proteins extracted from transfected cells were immunoblotted with anti-Flag, anti-α6, and anti-β7 antibodies. (B) Proteins extracted from hβ5t WT-Flag and hβ5t G49S-Flag transfected cells were fractionated by glycerol gradient centrifugation, and the fractions containing the 26S proteasome were immunoprecipitated with anti-α6 antibody followed by immunoblotting with anti-Flag, anti-α6, and anti-β7 antibodies. (C) WT or G49S mouse β5t (mβ5t) tagged with the Flag epitope at either N-terminus or C-terminus was transduced in fibroblasts isolated from β5i-deficient embryos. Cells were treated with IFN-γ to induce the expression of β1i and β2i, and extracted proteins were immunoprecipitated and immunoblotted with anti-Flag antibody. See complete unedited blots in the supplemental material. Asterisks indicate additional signals with an intermediate molecular size.