PKACs attenuate innate antiviral response by phosphorylating VISA and priming it for MARCH5-mediated degradation

Abstract

Sensing of viral RNA by RIG-I-like receptors initiates innate antiviral response, which is mediated by the central adaptor VISA. How the RIG-I-VISA-mediated antiviral response is terminated at the late phase of infection is enigmatic. Here we identified the protein kinase A catalytic (PKAC) subunits α and β as negative regulators of RNA virus-triggered signaling in a redundant manner. Viral infection up-regulated cellular cAMP levels and activated PKACs, which then phosphorylated VISA at T54. This phosphorylation abrogated virus-induced aggregation of VISA and primed it for K48-linked polyubiquitination and degradation by the E3 ligase MARCH5, leading to attenuation of virus-triggered induction of downstream antiviral genes. PKACs-deficiency or inactivation by the inhibitor H89 potentiated innate immunity to RNA viruses in cells and mice. Our findings reveal a critical mechanism of attenuating innate immune response to avoid host damage at the late phase of viral infection by the house-keeping PKA kinase.

The E3 Ubiquitin Ligase TBK1 Mediates the Degradation of Multiple Picornavirus VP3 Proteins by Phosphorylation and Ubiquitination

“…Protein phosphorylation and ubiquitination regulate the activity and stability of target proteins and are important for signal transduction and multiple physiological processes. Viral infection activates the protein kinase A catalytic subunits (PKACs), which in turn phosphorylate VISA at T54, thereby impairing VISA aggregation and leading to its K48-linked polyubiquitination and degradation by the E3 ligase MARCH5 (39). The serine-threonine kinase CK1 interacts with and phosphorylates TRAF3 at Ser349, which thereby promotes the Lys63 (K63)-linked ubiquitination of TRAF3 and subsequent recruitment of kinase TBK1 to TRAF3 (40).…”

TRAF 3 IP 3 mediates the recruitment of TRAF 3 to MAVS for antiviral innate immunity

“…In contrast, dissecting the molecular mechanisms underlying MAVS activation and how MAVS activates its downstream signaling has been arduous. As such, a number of proteins have been identified to modulate MAVS antiviral activity (Moore et al, 2008;Lei et al, 2012;Liu et al, 2012Liu et al, , 2017Zhang et al, 2014;Yan et al, 2017). Among them, TRAF proteins were found to play redundant roles downstream of MAVS.…”

SARS-CoV-2 membrane glycoprotein M antagonizes the MAVS-mediated innate antiviral response

“…Semidenaturing detergent agarose gel electrophoresis (SDD-AGE) Semidenaturing detergent agarose gel electrophoresis (SDD-AGE) was performed as previously described. 14 In brief, crude mitochondria were resuspended in 1× sample buffer (0.5× TBE, 10% glycerol, 2% SDS, and 0.0025% bromophenol blue) and loaded onto a vertical 1.5% agarose gel (Bio-Rad). After electrophoresis in running buffer (1×TBE and 0.01% SDS) for 50 min with a constant voltage of 100 V at 4°C, the proteins were transferred to an immobile membrane (Millipore) for immunoblot analysis.…”

“…13 The aggregated MAVS acts as a central platform for the recruitment of downstream signaling components, including TRAF2/3/5/6, TBK1 and IKK, leading to the activation of the transcription factors IRF3 and NF-κB and to the induction of downstream antiviral effector genes. [14][15][16][17] SARS-CoV-2, a member of the coronavirus family, is a typical single-stranded positive-sense RNA virus that encodes over 28 proteins, including 4 structural proteins (spike, membrane, envelope, and nucleocapsid), 16 nonstructural proteins (NSP1-NSP16), and 8 auxiliary proteins (ORF3a, ORF3b, ORF6, ORF7a, ORF7b, ORF8, ORF9b and ORF14). [18][19][20] Recently, SARS-CoV-2 has caused a global pandemic and worldwide social and economic disruption.…”