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C‐Terminal Cleavage of Human Foxp3 at a Proprotein Convertase Motif Abrogates its Suppressive Function
Author(s) -
Elhage R.,
Cheraï M.,
Levacher B.,
DarrasseJeze G.,
Baillou C.,
Zhao X.,
Khatib A.M.,
Piaggio E.,
Klatzmann D.
Publication year - 2015
Publication title -
scandinavian journal of immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.934
H-Index - 88
eISSN - 1365-3083
pISSN - 0300-9475
DOI - 10.1111/sji.12275
Subject(s) - furin , proprotein convertases , foxp3 , proprotein convertase , gene isoform , in vitro , cleavage (geology) , alternative splicing , microbiology and biotechnology , biology , western blot , chemistry , immunology , biochemistry , gene , immune system , enzyme , lipoprotein , paleontology , ldl receptor , cholesterol , fracture (geology)
Foxp3 plays a critical role in the development and function of regulatory T cells (Tregs). Differences in translational and post‐translational processing of murine and human Foxp3 have been recently reported. Human Foxp3 exists as four isoforms generated by alternative splicing. Mouse Foxp3 only exists as one isoform, but can be proteolytically cleaved by N‐terminal and/or C‐terminal proprotein convertase subtilisin/kexins ( PCSK s). Here, we show by transcriptome analysis that the proprotein convertases PCSK 7, PCSK 5 and Furin are present in human CD 4 + T cells with different expression patterns. Notably, after in vitro activation, only PCSK 7 and Furin are expressed in Tregs and T effector cells (Teffs), with overexpression of PCSK 7 in Tregs compared to Teffs. Human Foxp3 protein displays specific motifs that can be potentially cleaved by convertases. Consequently, we transduced human CD 4 + cells with Foxp3‐expressing lentiviral vectors and assessed the generation of proteolytically cleaved Foxp3 forms by Western blot. Three different Foxp3 forms were detected, indicating that human Foxp3 can also be subjected to proteolytic cleavage at the N‐terminal and C‐terminal ends. These results prompted us to assess the suppressive activity associated with each forms. We observed that full length and N‐cleaved Foxp3‐transduced CD 4 + T cells similarly suppressed the in vitro proliferation of Teffs. However, the C‐cleaved or N&C‐cleaved Foxp3 forms afforded almost no suppressive function, indicating a crucial role of the human Foxp3 C‐terminal region in Tregs suppressive activity, in marked contrast with the report of a superior suppressive activity for the C‐cleaved murine Foxp3 compared to the full length.