DOK3 Is Required for IFN-β Production by Enabling TRAF3/TBK1 Complex Formation and IRF3 Activation

Abstract

The downstream of kinase (DOK) family of adaptors is generally involved in the negative regulation of signaling pathways. DOK1, 2, and 3 were shown to attenuate TLR4 signaling by inhibiting Ras-ERK activation. In this study, we elucidated a novel role for DOK3 in IFN-β production. Macrophages lacking DOK3 were impaired in IFN-β synthesis upon influenza virus infection or polyinosinic-polyribocytidylic acid stimulation. In the absence of DOK3, the transcription factor IFN regulatory factor 3 was not phosphorylated and could not translocate to the nucleus to activate ifn-β gene expression. Interestingly, polyinosinic-polyribocytidylic acid–induced formation of the upstream TNFR-associated factor (TRAF) 3/TANK-binding kinase (TBK) 1 complex was compromised in dok3−/− macrophages. DOK3 was shown to bind TBK1 and was required for its activation. Furthermore, we demonstrated that overexpression of DOK3 and TBK1 could significantly enhance ifn-β promoter activity. DOK3 was also shown to bind TRAF3, and the binding of TRAF3 and TBK1 to DOK3 required the tyrosine-rich C-terminal domain of DOK3. We further revealed that DOK3 was phosphorylated by Bruton’s tyrosine kinase. Hence, DOK3 plays a critical and positive role in TLR3 signaling by enabling TRAF3/TBK1 complex formation and facilitating TBK1 and IFN regulatory factor 3 activation and the induction of IFN-β production.

TBK1 inhibitors: a review of patent literature (2011 – 2014)

“…Upon cytoplasmic DNA stimulation, autocrine motility factor receptor and INSIG1 (insulin-induced gene 1) interact to form an E3 ubiquitin ligase complex and catalyze K27-linked polyubiquitination of STING, which indirectly mediates TBK1 activity [8]. Furthermore, the downstream of kinase (DOK)3 plays a positive and critical role in TLR3 signaling through formation of the TRAF3/TBK1 complex and activation of TBK1 and IFN regulatory factor 3 [9]. In regard to negative regulation, USP2b [ubiquitin-specific protease (USP) 2b] serves as a deubiquitinating enzyme that can cleave K63-linked polyubiquitin chains from TBK1 to inhibit TBK1 kinase activity, and negatively regulate IFN signaling and the antiviral immune response [10].…”

TRAF3: a novel tumor suppressor gene in macrophages

“…Furthermore, numerous adaptor proteins either facilitate or interfere with the complex formation of MAVS-TRAF3-TBK1-IKKε or TRIF-TRAF3-TBK1-IKKε in response to infections. Examples of such adaptor proteins include TANK [50,51] , TRADD [52] , UXT-V1 [53] , DOK3 [54] , A20 [55] , TAX1BP1 [55] , UBXN1 [56] , optineurin [57] , TRAM [58] , and FLN29 [59] . Therefore, TRAF3 is a central regulatory point for optimal innate immune responses.…”

“…Similar to M-TRAF3 −/− mice, several other mouse models were previously reported to spontaneously develop histiocytic sarcomas, including p21 −/− [66] , Cyp1b1 −/− [67] , p19ARF −/− Bax −/− [68] , PTEN −/− INK4a/ARF −/− [63] , Dok1 −/− Dok2 −/− Dok3 −/− [69] , and humanized TLR7/TLR8 transgenic [70] mice, implicating these genes in the pathogenesis of HS. Among these, TRAF3 is functionally linked to TLR7, TLR8, and DOK3 [1,54] . TRAF3 is recruited to the TLR7 and TLR8 signaling complex through direct interaction with MyD88 [1] (Fig.…”

PLA1A Participates in the Antiviral Innate Immune Response by Facilitating the Recruitment of TANK-Binding Kinase 1 to Mitochondria

“…In addition to direct regulation on TBK1, several factors were found to modulate the TBK1 function by influencing the formation of functional TBK1-containing complexes. For example, DOK3 plays a positive role in TLR3 signaling by enabling TRAF3/TBK1 complex formation [18], while FOS-like antigen 1 plays a negative role in the type I IFN response to malaria and viral infection by blocking TBK1 and TRAF3/TRIF interactions [19].…”