Bruton’s Tyrosine Kinase Phosphorylates DDX41 and Activates Its Binding of dsDNA and STING to Initiate Type 1 Interferon Response

• Induction of IFN-β by STING-activating agents is impaired in the absence of BTK
• BTK interacts with STING and the DNA sensor, DDX41 helicase
• BTK phosphorylates DDX41
• Tyr364 and Tyr414 of DDX41 are critical for DNA recognition and binding to STING

SummaryThe innate immune system senses cytosolic dsDNA and bacterial cyclic dinucleotides and initiates signaling via the adaptor STING to induce type 1 interferon (IFN) response. We demonstrate here that BTK-deficient cells have impaired IFN-β production and TBK1/IRF3 activation when stimulated with agonists or infected with pathogens that activate STING signaling. BTK interacts with STING and DDX41 helicase. The kinase and SH3/SH2 interaction domains of BTK bind, respectively, the DEAD-box domain of DDX41 and transmembrane region of STING. BTK phosphorylates DDX41, and its kinase activities are critical for STING-mediated IFN-β production. We show that Tyr364 and Tyr414 of DDX41 are critical for its recognition of AT-rich DNA and binding to STING, and tandem mass spectrometry identifies Tyr414 as the BTK phosphorylation site. Modeling studies further indicate that phospho-Tyr414 strengthens DDX41’s interaction with STING. Hence, BTK plays a critical role in the activation of DDX41 helicase and STING signaling.

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