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The ubiquitin‐like protein monoclonal nonspecific suppressor factor β conjugates to endophilin II and regulates phagocytosis
Author(s) -
Nakamura Morihiko,
Shimosaki Shunsuke
Publication year - 2009
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2009.07348.x
Subject(s) - ubiquitin , phagocytosis , conjugate , microbiology and biotechnology , chemistry , suppressor , monoclonal antibody , biology , biochemistry , immunology , antibody , gene , mathematical analysis , mathematics
Monoclonal nonspecific suppressor factor β (MNSFβ) is a ubiquitously expressed member of the ubiquitin‐like family that has been implicated in various biological functions. Previous studies have demonstrated that MNSFβ covalently binds to the intracellular proapoptotic protein Bcl‐G in cells of the macrophage cell line Raw264.7, suggesting involvement of this ubiquitin‐like protein in apoptosis. In this study, we purified a 62 kDa MNSFβ adduct from murine liver lysates by sequential chromatography on DEAE and anti‐MNSFβ IgG‐conjugated Sepharose. MALDI‐TOF MS fingerprinting revealed that this MNSFβ adduct consists of an 8.5 kDa MNSFβ and endophilin II, a member of the endophilin A family. MNSFβ may conjugate to endophilin II with a linkage between the C‐terminal Gly74 and Lys294. We confirmed this result by immunoprecipitation/western blot studies. Endophilin II was ubiquitously expressed in various tissues, although a truncated form was observed in liver. The 62 kDa MNSFβ–endophilin II was specifically expressed in liver and macrophages. Small interfering RNA‐mediated knockdown of endophilin II and/or MNSFβ promoted phagocytosis of zymosan in Raw264.7 cells. Conversely, cotransfection of endophilin II and MNSFβ cDNAs inhibited the phagocytosis of zymosan. Such inhibition was not observed in cells expressing a mutant of endophilin II in which Lys294 was replaced by arginine. These results suggest that the post‐translational modification of endophilin II by MNSFβ might be implicated in phagocytosis by macrophages. Structured digital abstract• MINT‐7261558 , MINT‐7261537 , MINT‐7261546 : MNSF beta (uniprotkb: P35545 ) physically interacts ( MI:0915 ) with Endophilin‐2 (uniprotkb: Q62419 ) by anti bait coimmunoprecipitation ( MI:0006 )