title: The ubiquitin-specific protease USP15 promotes RIG-I-mediated antiviral signaling by deubiquitylating TRIM25.
abstract: Ubiquitylation is an important mechanism for regulating innate immune responses to viral infections. Attachment of lysine 63 (Lys(63))-linked ubiquitin chains to the RNA sensor retinoic acid-inducible gene-I (RIG-I) by the ubiquitin E3 ligase tripartite motif protein 25 (TRIM25) leads to the activation of RIG-I and stimulates production of the antiviral cytokines interferon-α (IFN-α) and IFN-β. Conversely, Lys(48)-linked ubiquitylation of TRIM25 by the linear ubiquitin assembly complex (LUBAC) stimulates the proteasomal degradation of TRIM25, thereby inhibiting the RIG-I signaling pathway. Here, we report that ubiquitin-specific protease 15 (USP15) deubiquitylates TRIM25, preventing the LUBAC-dependent degradation of TRIM25. Through protein purification and mass spectrometry analysis, we identified USP15 as an interaction partner of TRIM25 in human cells. Knockdown of endogenous USP15 by specific small interfering RNA markedly enhanced the ubiquitylation of TRIM25. In contrast, expression of wild-type USP15, but not its catalytically inactive mutant, reduced the Lys(48)-linked ubiquitylation of TRIM25, leading to its stabilization. Furthermore, ectopic expression of USP15 enhanced the TRIM25- and RIG-I-dependent production of type I IFN and suppressed RNA virus replication. In contrast, depletion of USP15 resulted in decreased IFN production and markedly enhanced viral replication. Together, these data identify USP15 as a critical regulator of the TRIM25- and RIG-I-mediated antiviral immune response, thereby highlighting the intricate regulation of innate immune signaling.
authors.affiliation: 1Department of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, USA.
authors.forename: Eva-Katharina
authors.initials: EK
authors.lastname: Pauli
authors.forename: Ying Kai
authors.initials: YK
authors.lastname: Chan
authors.forename: Meredith E
authors.initials: ME
authors.lastname: Davis
authors.forename: Sebastian
authors.initials: S
authors.lastname: Gableske
authors.forename: May K
authors.initials: MK
authors.lastname: Wang
authors.forename: Katharina F
authors.initials: KF
authors.lastname: Feister
authors.forename: Michaela U
authors.initials: MU
authors.lastname: Gack
mesh_terms: D000998:Antiviral Agents / Q000276:immunology / Q000378:metabolism; D015153:Blotting, Western; D002478:Cells, Cultured; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D007113:Immunity, Innate / Q000276:immunology; D016898:Interferon-alpha / Q000276:immunology / Q000378:metabolism; D016899:Interferon-beta / Q000276:immunology / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D018613:Microscopy, Confocal; D009522:Newcastle disease virus / Q000235:genetics / Q000276:immunology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D059748:Proteolysis; D034622:RNA Interference; D011971:Receptors, Immunologic; D029082:Sendai virus / Q000276:immunology; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*; D014157:Transcription Factors / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D064570:Ubiquitin-Specific Proteases / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D054875:Ubiquitination; D014721:Vesicular stomatitis Indiana virus / Q000235:genetics / Q000276:immunology; D014779:Virus Replication / Q000276:immunology
chemical_list: D000998:Antiviral Agents; D016898:Interferon-alpha; D011971:Receptors, Immunologic; D014157:Transcription Factors; D000070584:Tripartite Motif Proteins; D049452:Green Fluorescent Proteins; D016899:Interferon-beta; C084523:TRIM25 protein, human; D044767:Ubiquitin-Protein Ligases; C579226:USP15 protein, human; D064570:Ubiquitin-Specific Proteases; D046988:Proteasome Endopeptidase Complex; C452820:RIGI protein, human; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases; D008239:Lysine