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Title: HTLV-1 bZIP Factor Enhances T-Cell Proliferation by Impeding the Suppressive Signaling of Co-inhibitory Receptors
Authors: Kinosada, Haruka
Yasunaga, Jun Ichirou
Shimura, Kazuya  kyouindb  KAKEN_id  orcid (unconfirmed)
Miyazato, Paola
Onishi, Chiho
Iyoda, Tomonori
Inaba, Kayo
Matsuoka, Masao
Author's alias: 安永, 純一朗
稲葉, カヨ
松岡, 雅雄
Keywords: Immunology
Molecular Biology
Issue Date: 3-Jan-2017
Publisher: Public Library of Science
Journal title: PLoS Pathogens
Volume: 13
Thesis number: e1006120
Abstract: Human T-cell leukemia virus type 1 (HTLV-1) causes adult T-cell leukemia-lymphoma (ATL) and inflammatory diseases. To enhance cell-to-cell transmission of HTLV-1, the virus increases the number of infected cells in vivo. HTLV-1 bZIP factor (HBZ) is constitutively expressed in HTLV-1 infected cells and ATL cells and promotes T-cell proliferation. However, the detailed mechanism by which it does so remains unknown. Here, we show that HBZ enhances the proliferation of expressing T cells after stimulation via the T-cell receptor. HBZ promotes this proliferation by influencing the expression and function of multiple co-inhibitory receptors. HBZ suppresses the expression of BTLA and LAIR-1 in HBZ expressing T cells and ATL cells. Expression of T cell immunoglobulin and ITIM domain (TIGIT) and Programmed cell death 1 (PD-1) was enhanced, but their suppressive effect on T-cell proliferation was functionally impaired. HBZ inhibits the co-localization of SHP-2 and PD-1 in T cells, thereby leading to impaired inhibition of T-cell proliferation and suppressed dephosphorylation of ZAP-70 and CD3ζ. HBZ does this by interacting with THEMIS, which associates with Grb2 and SHP-2. Thus, HBZ interacts with the SHP containing complex, impedes the suppressive signal from PD-1 and TIGIT, and enhances the proliferation of T cells. Although HBZ was present in both the nucleus and the cytoplasm of T cells, HBZ was localized largely in the nucleus by suppressed expression of THEMIS by shRNA. This indicates that THEMIS is responsible for cytoplasmic localization of HBZ in T cells. Since THEMIS is expressed only in T-lineage cells, HBZ mediated inhibition of the suppressive effects of co-inhibitory receptors accounts for how HTLV-1 induces proliferation only of T cells in vivo. This study reveals that HBZ targets co-inhibitory receptors to cause the proliferation of infected cells.
Rights: © 2017 Kinosada et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
DOI(Published Version): 10.1371/journal.ppat.1006120
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