TANK Knockout Cell Line (HEK293)

Induction of autophagy is an ancient function of the cyclic GMP-AMP (cGAMP) synthase (cGAS)-stimulator of interferon genes (STING) pathway through which autophagic cargoes are delivered to lysosomes for degradation. However, whether lysosome function is also modulated by the cGAS-STING pathway remains unknown. Here, we discovered that the cGAS-STING pathway upregulated lysosomal activity by stimulating lysosome biogenesis independently of the downstream protein kinase TANK-binding kinase 1 (TBK1). STING activation enhanced lysosome biogenesis through inducing the nuclear translocation of transcription factor EB (TFEB) as well as its paralogs transcription factor E3 (TFE3) and microphthalmia-associated transcription factor (MITF). STING-induced lipidation of GABA type A receptor-associated protein (GABARAP), an autophagy-related protein, on STING vesicles was responsible for TFEB activation. Membrane-bound GABARAP sequestered the GTPase-activating protein folliculin (FLCN) and FLCN-interacting protein (FNIP) complex to block its function toward the Rag GTPases Ras-related GTP-binding C and D (RagC and RagD), abolishing mechanistic target of rapamycin (mTOR) complex 1 (mTORC1)-dependent phosphorylation and inactivation of TFEB. Functionally, STING-induced lysosome biogenesis within cells facilitated the clearance of cytoplasmic DNA and invading pathogens. Thus, our findings reveal that induction of lysosome biogenesis is another important function of the cGAS-STING pathway.

TAX1BP1 is a selective macroautophagy/autophagy receptor that inhibits NFKB and RIGI-like receptor (RLR) signaling to prevent excessive inflammation and maintain homeostasis. Selective autophagy receptors such as SQSTM1/p62 and OPTN are phosphorylated by the kinase TBK1 to stimulate their selective autophagy function. However, it is unknown if TAX1BP1 is regulated by TBK1 or other kinases under basal conditions or during RNA virus infection. Here, we found that TBK1 and IKBKE/IKKi function redundantly to phosphorylate TAX1BP1 and regulate its autophagic turnover through canonical macroautophagy. TAX1BP1 phosphorylation promotes its localization to lysosomes, resulting in its degradation. Additionally, we found that during vesicular stomatitis virus infection, TAX1BP1 is targeted to lysosomes in an ATG8-family protein-independent manner. Furthermore, TAX1BP1 plays a critical role in the clearance of MAVS aggregates, and phosphorylation of TAX1BP1 controls its MAVS aggrephagy function. Together, our data support a model whereby TBK1 and IKBKE license TAX1BP1-selective autophagy function to inhibit MAVS and RLR signaling. ATG: autophagy related; BafA1: bafilomycin A1; CALCOCO2: calcium binding and coiled-coil domain 2; GFP: green fluorescent protein; IFA: indirect immunofluorescence assay; IFN: interferon; IκB: inhibitor of nuclear factor kappa B; IKK: IκB kinase; IRF: interferon regulatory factor; KO: knockout; LAMP1: lysosomal associated membrane protein 1; LIR: LC3-interacting region; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAVS: mitochondrial antiviral signaling protein; MEF: mouse embryonic fibroblast; MOI: multiplicity of infection; IKBKG/NEMO: inhibitor of nuclear factor kappa B kinase regulatory subunit gamma; NFKB: nuclear factor kappa B; OPTN: optineurin; Poly(I:C): polyinosinic-polycytidylic acid; RB1CC1/FIP200: RB1 inducible coiled-coil 1; RIGI: RNA sensor RIG-I; RLR: RIGI-like receptor; SDD-AGE: semi-denaturing detergent-agarose gel electrophoresis; SeV: Sendai virus; SLR: SQSTM1-like receptor; SQSTM1: sequestosome 1; TAX1BP1: Tax1 binding protein 1; TBK1: TANK binding kinase 1; TNF: tumor necrosis factor; TRAF: TNF receptor associated factor; VSV: vesicular stomatitis virus; ZnF: zinc finger.

STING1/MITA not only induces innate immune responses but also triggers macroautophagy/autophagy to selectively degrade signaling molecules. However, the molecular mechanisms regulating STING1-mediated selective autophagy remain unclear. Here, we first report that ATP2A2 directly interacts with STING1, regulating STING1-mediated innate immune response by modulating its polymerization and trafficking, thereby inhibiting DNA virus infection. Notably, while screening for reticulophagy receptors involved in STING1-mediated selective autophagy, we identified SEC62 as an important receptor protein in STING1-mediated reticulophagy. Mechanistically, SEC62 strengthens its interaction with STING1 upon activation and concurrently facilitates STING1-mediated reticulophagy upon starvation, which are dependent on ATP2A2. Furthermore, knocking down SEC62 in WT cells inhibits STING1-mediated MAP1LC3B/LC3B lipidation and autophagosome formation, an effect that is lost in knockout cells, suggesting that SEC62's role in STING1-mediated selective autophagy is ATP2A2 dependent. Thus, our findings identify the reticulophagy receptor SEC62 as a novel receptor protein regulating STING1-mediated selective autophagy, providing new insight into the mechanism regarding a reticulophagy receptor in the process of STING1-induced selective autophagy. aa: amino acids; AP-MS: affinity tag purification-mass spectrometry; ATP2A1: ATPase sarcoplasmic/endoplasmic reticulum Ca transporting 1; ATP2A2: ATPase sarcoplasmic/endoplasmic reticulum Ca transporting 2; ATP2A3: ATPase sarcoplasmic/endoplasmic reticulum Ca transporting 3; CANX: calnexin; CCPG1: cell cycle progression 1; CGAS: cyclic GMP-AMP synthase; ctDNA: calf thymus DNA; dsRNA: double-stranded RNA; diABZI: diamidobenzimidazole; ER: endoplasmic reticulum; ERGIC: ER-Golgi intermediate compartment; EBSS: Earle's Balanced Salt Solution; EV: empty vector; FL: full length; GOLGA2/GM130: golgin A2; HSV-1: herpes simplex virus type 1; IRF3: interferon regulatory factor 3; IFNs: type I interferons; ISD: interferon stimulatory DNA; KO: knockout; MAVS: mitochondrial antiviral signaling protein; MOI: multiplicity of infection; poly(I:C): polyinosinic-polycytidylic acid; NBR1: NBR1 autophagy cargo receptor; PRR: pattern recognition receptor; reticulophagy: selective autophagic degradation of the ER; RETREG1/FAM134B: reticulophagy regulator 1; RIGI: RNA sensor RIG-I; RTN3L: reticulon 3; SEC62: SEC62 homolog, preprotein translocation factor; SeV: Sendai virus; STIM1: stromal interaction molecule 1; STING1/MITA: stimulator of interferon response cGAMP interactor 1; TBK1: TANK binding kinase 1; TEX264: testis expressed 264, ER-phagy receptor; TMX1: thioredoxin related transmembrane protein 1; VSV: vesicular stomatitis virus; VACV: vaccinia virus; ZMPSTE24: zinc metallopeptidase STE24.

TANK-binding kinase 1 (TBK1), a core kinase of antiviral pathways, activates the production of interferons (IFNs). It has been reported that deacetylation activates TBK1; however, the precise mechanism still remains to be uncovered. We show here that during the early stage of viral infection, the acetylation of TBK1 was increased, and the acetylation of TBK1 at Lys241 enhanced the recruitment of IRF3 to TBK1. HDAC3 directly deacetylated TBK1 at Lys241 and Lys692, which resulted in the activation of TBK1. Deacetylation at Lys241 and Lys692 was critical for the kinase activity and dimerization of TBK1 respectively. Using knockout cell lines and transgenic mice, we confirmed that a HDAC3 null mutant exhibited enhanced susceptibility to viral challenge via impaired production of type I IFNs. Furthermore, activated TBK1 phosphorylated HDAC3, which promoted the deacetylation activity of HDAC3 and formed a feedback loop. In this study, we illustrated the roles the acetylated and deacetylated forms of TBK1 play in antiviral innate responses and clarified the post-translational modulations involved in the interaction between TBK1 and HDAC3.

Deeply understanding the virus-host interaction is a prerequisite for developing effective anti-viral strategies. Traditionally, the transporter associated with antigen processing type 1 (TAP1) is critical for antigen presentation to regulate adaptive immunity. However, its role in controlling viral infections through modulating innate immune signaling is not yet fully understood. In the present study, we reported that , as a product of interferon-stimulated genes (ISGs), had broadly antiviral activity against various viruses such as herpes simplex virus 1 (HSV-1), adenoviruses (AdV), vesicular stomatitis virus (VSV), dengue virus (DENV), Zika virus (ZIKV), and influenza virus (PR8) etc. This antiviral activity by TAP1 was further confirmed by series of loss-of-function and gain-of-function experiments. Our further investigation revealed that TAP1 significantly promoted the interferon (IFN)-β production through activating the TANK binding kinase-1 (TBK1) and the interferon regulatory factor 3 (IRF3) signaling transduction. Our work highlighted the broadly anti-viral function of TAP1 by modulating innate immunity, which is independent of its well-known function of antigen presentation. This study will provide insights into developing novel vaccination and immunotherapy strategies against emerging infectious diseases.