TANK-binding Kinase Research Articles

Control of mitophagy initiation and progression by the TBK1 adaptors NAP1 and SINTBAD.

Mitophagy preserves overall mitochondrial fitness by selectively targeting damaged mitochondria for degradation. The regulatory mechanisms that prevent PTEN-induced putative kinase 1 (PINK1) and E3 ubiquitin ligase Parkin (PINK1/Parkin)-dependent mitophagy and other selective autophagy pathways from overreacting while ensuring swift progression once initiated are largely elusive. Here, we demonstrate how the TBK1 (TANK-binding kinase 1) adaptors NAP1 (NAK-associated protein 1) and SINTBAD (similar to NAP1 TBK1 adaptor) restrict the initiation of OPTN (optineurin)-driven mitophagy by competing with OPTN for TBK1. Conversely, they promote the progression of nuclear dot protein 52 (NDP52)-driven mitophagy by recruiting TBK1 to NDP52 and stabilizing its interaction with FIP200. Notably, OPTN emerges as the primary recruiter of TBK1 during mitophagy initiation, which in return boosts NDP52-mediated mitophagy. Our results thus define NAP1 and SINTBAD as cargo receptor rheostats, elevating the threshold for mitophagy initiation by OPTN while promoting the progression of the pathway once set in motion by supporting NDP52. These findings shed light on the cellular strategy to prevent pathway hyperactivity while still ensuring efficient progression.

Glycyrrhetinic acid blocks SARS-CoV-2 infection by activating the cGAS-STING signalling pathway.

Traditional Chinese medicine (TCM) played an important role in controlling the COVID-19 pandemic, but the scientific basis and its active ingredients are still weakly studied. This study aims to decipher the underlying anti-SARS-CoV-2 mechanisms of glycyrrhetinic acid (GA). GA's anti-SARS-CoV-2 effect was verified both in vitro and in vivo. Homogeneous time-resolved fluorescence assays, biolayer interferometry technology, and molecular docking were employed to examine interactions of GA with human stimulator of interferon genes (hSTING). Immunofluorescence staining, western blot, and RT-qPCR were used to investigate nuclear translocation of interferon regulatory factor 3 (IRF3) and levels of STING target genes. Pharmacokinetics of GA was studied in mice. GA could directly bind to Ser162 and Tyr240 residues of hSTING, thus up-regulating downstream targets and activation of the STING signalling pathway. Such activation is crucial for limiting the replication of SARS-CoV-2 Omicron in Calu-3 cells and protecting against lung injury induced by SARS-CoV-2 Omicron infection in K18-ACE2 transgenic mice. Immunofluorescence staining and western blot indicated that GA increased levels of phosphorylated STING, phosphorylated TANK-binding kinase-1, and cyclic GMP-AMP synthase (cGAS). Importantly, GA increased nuclear translocation of IRF3. Pharmacokinetic analysis of GA in mice indicated it can be absorbed into circulation and detected in the lung at a stable level. Activation of the cGAS-STING pathway through the GA-STING-IRF3 axis is essential for the antiviral activity of GA in mice, providing new insights into the potential translation of GA for treating SARS-CoV-2 in patients.

Suppression of smooth muscle cell inflammation by myocardin-related transcription factors involves inactivation of TANK-binding kinase 1

Myocardin-related transcription factors (MRTFs: myocardin/MYOCD, MRTF-A/MRTFA, and MRTF-B/MRTFB) suppress production of pro-inflammatory cytokines and chemokines in human smooth muscle cells (SMCs) through sequestration of RelA in the NF-κB complex, but additional mechanisms are likely involved. The cGAS-STING pathway is activated by double-stranded DNA in the cytosolic compartment and acts through TANK-binding kinase 1 (TBK1) to spark inflammation. The present study tested if MRTFs suppress inflammation also by targeting cGAS-STING signaling. Interrogation of a transcriptomic dataset where myocardin was overexpressed using a panel of 56 cGAS-STING cytokines showed the panel to be repressed. Moreover, MYOCD, MRTFA, and SRF associated negatively with the panel in human arteries. RT-qPCR in human bronchial SMCs showed that all MRTFs reduced pro-inflammatory cytokines on the panel. MRTFs diminished phosphorylation of TBK1, while STING phosphorylation was marginally affected. The TBK1 inhibitor amlexanox, but not the STING inhibitor H-151, reduced the anti-inflammatory effect of MRTF-A. Co-immunoprecipitation and proximity ligation assays supported binding between MRTF-A and TBK1 in SMCs. MRTFs thus appear to suppress cellular inflammation in part by acting on the kinase TBK1. This may defend SMCs against pro-inflammatory insults in disease.

Role of TBK1 Inhibition in Targeted Therapy of Cancer.

TANK-binding kinase 1 (TBK1) is a serine/threonine protein that plays a crucial role in various biological processes like immunity, autophagy, cell survival, and proliferation. The level and kinase activity of the TBK1 protein is regulated through post-translational modifications (PTMs). TBK1 mainly mediates the activation of IRF3/7 and NF-κB signaling pathways while also participating in the regulation of cellular activities such as autophagy, mitochondrial metabolism, and cell proliferation. TBK1 regulates immune, metabolic, inflammatory, and tumor occurrence and development within the body through these cellular activities. TBK1 kinase has emerged as a promising therapeutic target for tumor immunity. However, its molecular mechanism of action remains largely unknown. The identification of selective TBK1 small molecule inhibitors can serve as valuable tools for investigating the biological function of TBK1 protein and also as potential drug candidates for tumor immunotherapy. The current research progress indicates that some TBK1 inhibitors (compounds 15,16 and 21) exhibit certain antitumor effects in vitro culture systems. Here, we summarize the mechanism of action of TBK1 in tumors in recent years and the progress of small molecule inhibitors of TBK1.

IKK2 modulates the innate immune response of Zhikong scallop (Chlamys farreri) to bacterial and viral stimuli through the MyD88-dependent Toll-like receptor signaling pathway

Members of the inhibitor of nuclear factor kappa-B kinase (IKK) family are pivotal components of the innate immune signaling pathway responsible for regulating immune and inflammatory responses. Nevertheless, the various roles that IKKs play in the physiology of invertebrates, particularly marine mollusks, remain largely unexplored. In this study, an IKK gene was cloned from the Zhikong scallop, Chlamys farreri, and denoted as CfIKK2. CfIKK2 belongs to the TANK-binding kinase 1 (TBK1)/IKKε family. Real-time quantitative reverse transcription-polymerase chain reaction analysis showed that CfIKK2 was expressed in various scallop tissues and that its transcript levels substantially increased under different pathogenic stress conditions (including lipopolysaccharide, peptidoglycan, poly(I:C), acute viral necrosis virus, and Vibrio challenge). Co-immunoprecipitation experiments revealed that CfIKK2 interacts with MyD88 (a crucial adaptor in the Toll-like receptor signaling pathway) proteins through its C-terminal TBK1 coiled-coil domain 1. Moreover, CfIKK2 has been shown to interact with itself. In HEK293T cells, CfIKK2 overexpression resulted in an augmentation of mitogen-activated protein kinase phosphorylation. Furthermore, overexpression of CfIKK2 resulted in the activation of interferon reporter genes. In summary, our findings offer valuable insights into the mechanisms through which CfIKK2 responds to stress generated by pathogen-associated molecular patterns, participates in Toll-like receptor signaling, and ultimately activates some of the key cytokines involved in innate immunity in C. farreri. As a critical signaling molecule and immunoregulatory factor, CfIKK2 plays a vital role in the innate immune system of the Zhikong scallop.

African swine fever virus MGF505-6R attenuates type I interferon production by targeting STING for degradation.

African swine fever (ASF) is an acute hemorrhagic and devastating infectious disease affecting domestic pigs and wild boars. It is caused by the African swine fever virus (ASFV), which is characterized by genetic diversity and sophisticated immune evasion strategies. To facilitate infection, ASFV encodes multiple proteins to antagonize host innate immune responses, thereby contributing to viral virulence and pathogenicity. The molecular mechanisms employed by ASFV-encoded proteins to modulate host antiviral responses have not been comprehensively elucidated. In this study, it was observed that the ASFV MGF505-6R protein, a member of the multigene family 505 (MGF505), effectively suppressed the activation of the interferon-beta (IFN-β) promoter, leading to reduced mRNA levels of antiviral genes. Additional evidence has revealed that MGF505-6R antagonizes the cGAS-STING signaling pathway by interacting with the stimulator of interferon genes (STING) for degradation in the autophagy-lysosomal pathway. The domain mapping revealed that the N-terminal region (1-260aa) of MGF505-6R is the primary domain responsible for interacting with STING, while the CTT domain of STING is crucial for its interaction with MGF505-6R. Furthermore, MGF505-6R also inhibits the activation of STING by reducing the K63-linked polyubiquitination of STING, leading to the disruption of STING oligomerization and TANK binding kinase 1 (TBK1) recruitment, thereby impairing the phosphorylation and nuclear translocation of interferon regulatory factor 3 (IRF3). Collectively, our study elucidates a novel strategy developed by ASFV MGF505-6R to counteract host innate immune responses. This discovery may offer valuable insights for further exploration of ASFV immune evasion mechanisms and antiviral strategies.

SGIV VP82 inhibits the interferon response by degradation of IRF3 and IRF7

During virus-host co-evolution, viruses have developed multiple strategies to dampen IFN response and prevent its antiviral activity in host cells. To date, the interactions between host IFN response and the immune evasion strategies exploited by fish iridoviruses still remain largely uncertain. Here, a potential immune evasion protein candidate of Singapore grouper iridovirus (SGIV), VP82 (encoded by SGIV ORF82) was screened and its roles during viral replication were investigated in detail. Firstly, VP82 overexpression dramatically decreased IFN or ISRE promoter activity and the transcription levels of IFN stimulated genes (ISGs) stimulated by grouper cyclic GMP-AMP synthase (EccGAS)/stimulator of interferon genes (EcSTING), TANK-binding kinase 1 (EcTBK1), IFN regulatory factor 3 (EcIRF3)and EcIRF7. Secondly, Co-IP assays indicated that VP82 interacted with EcIRF3 and EcIRF7, but not EcSTING and EcTBK1, which was consistent with the co-localization between VP82 and EcIRF3 or EcIRF7. Furthermore, VP82 promoted the degradation of EcIRF3 and EcIRF7 in a dose-dependent manner via the autophagy pathway. Finally, VP82 overexpression accelerated SGIV replication, evidenced by the increased transcriptions of viral core genes and viral production. Moreover, the antiviral action of EcIRF3 or EcIRF7 was significantly depressed in VP82 overexpressed cells. Together, VP82 was speculated to exert crucial roles for SGIV replication by inhibiting the IFN response via the degradation of IRF3 and IRF7. Our findings provided new insights into understanding the immune evasion strategies utilized by fish iridovirus through IFN regulation.

PLK1-activating IFI16-STING-TBK1 pathway induces apoptosis of intestinal epithelial cells in patients with intestinal Behçet's syndrome.

Inflammatory signals from immunological cells may cause damage to intestinal epithelial cells (IECs), resulting in intestinal inflammation and tissue impairment. Interferon-γ-inducible protein 16 (IFI16) was reported to be involved in the pathogenesis of Behçet's syndrome (BS). This study aimed to investigate how inflammatory cytokines released by immunological cells and IFI16 participate in the pathogenesis of intestinal BS. RNA sequencing and real-time quantitative PCR (qPCR) showed that the positive regulation of tumor necrosis factor-α (TNF-α) production in peripheral blood mononuclear cells (PBMCs) of intestinal BS patients may be related to the upregulation of polo like kinase 1 (PLK1) in PBMCs (P = 0.012). The plasma TNF-α protein level in intestinal BS was significantly higher than in healthy controls (HCs; P = 0.009). PBMCs of intestinal BS patients and HCs were co-cultured with human normal IECs (NCM460) to explore the interaction between immunological cells and IECs. Using IFI16 knockdown, PBMC-NCM460 co-culture, TNF-α neutralizing monoclonal antibody (mAb), stimulator of interferon genes (STING) agonist 2'3'-cGAMP, and the PLK1 inhibitor SBE 13 HCL, we found that PLK1 promotes the secretion of TNF-α from PBMCs of intestinal BS patients, which causes overexpression of IFI16 and induces apoptosis of IECs via the STING-TBK1 pathway. The expressions of IFI16, TNF-α, cleaved caspase 3, phosphorylated STING (pSTING) and phosphorylated tank binding kinase 1 (pTBK1) in the intestinal ulcer tissue of BS patients were significantly higher than that of HCs (all P < 0.05). PLK1 in PBMCs of intestinal BS patients increased TNF-α secretion, inducing IEC apoptosis via activation of the IFI16-STING-TBK1 pathway. PLK1 and the IFI16-STING-TBK1 pathway may be new therapeutic targets for intestinal BS.

Rainbow trout DUBA inhibits type I interferon signaling by deubiquitinating TRAF3

Deubiquitinating enzyme A (DUBA), a member of the ovarian tumor (OTU) subfamily of deubiquitinases (DUBs), is recognized for its negative regulatory role in type I interferon (IFN) expression downstream of Toll-like receptor 3 (TLR3). However, its involvement in the TLR3 signaling pathway in fish remains largely unexplored. In this study, we investigated the regulatory role of DUBA (OmDUBA) in the TLR3 response in rainbow trout (Oncorhynchus mykiss). OmDUBA features a conserved OTU domain, and its expression increased in RTH-149 cells following stimulation with the TLR3 agonist poly(I:C). Gain- and loss-of-function experiments demonstrated that OmDUBA attenuated the activation of TANK-binding kinase 1 (TBK1), resulting in a subsequent reduction in type I IFN expression and IFN-stimulated response element (ISRE) activation in poly(I:C)-stimulated cells. OmDUBA interacted with TRAF3, a crucial mediator in TLR3-mediated type I IFN production. Under poly(I:C) stimulation, there was an augmentation in the K63-linked polyubiquitination of TRAF3, a process significantly inhibited upon OmDUBA overexpression. These findings suggest that OmDUBA may function similarly to its mammalian counterparts in downregulating the poly(I:C)-induced type I IFN response in rainbow trout by removing the K63-linked ubiquitin chain on TRAF3. Our study provides novel insights into the role of fish DUBA in antiviral immunity.

Inhibition of Usp14 ameliorates renal ischemia-reperfusion injury by reducing Tfap2a stabilization and facilitating mitophagy

Mitochondrial dysfunction is recognized as a pivotal contributor to the pathogenesis of renal ischemia-reperfusion (IR) injury. Mitophagy, the process responsible for removing damaged protein aggregates, stands as a critical mechanism safeguarding cells against IR injury. Currently, the role of deubiquitination in regulating mitophagy still needs to be completely elucidated. This study aimed to evaluate the impact of ubiquitin-specific peptidase 14 (Usp14), a deubiquitinase, in IR injury by influencing mitophagy. Utilizing a murine model of renal IR injury, Usp14 silencing was found to ameliorate kidney injury, leading to decreased levels of serum creatinine and blood urea nitrogen, alongside diminished oxidative stress and inflammation. In renal epithelial cells subjected to hypoxia/reoxygenation (H/R), Usp14 knockdown increased cell viability and reduced apoptosis. Further mechanistic studies revealed that Usp14 interacted with and deubiquitinated transcription factor AP-2 alpha (Tfap2a), thereby suppressing its downstream target gene, TANK binding kinase 1 (Tbk1), to influence mitophagy. Tfap2a overexpression or Tbk1 inhibition reversed the protective effects of Usp14 silencing on renal tubular cell injury and its facilitation of mitophagy. In summary, our study demonstrated the renoprotective role of Usp14 knockdown in mitigating renal IR injury by promoting Tfap2a-mediated Tbk1 upregulation and mitophagy. These findings advocate for exploring Usp14 inhibition as a promising therapeutic avenue for mitigating IR injury, primarily by enhancing the clearance of damaged mitochondria through augmented mitophagy.

Cyclic guanosine monophosphate-adenosine monophosphate synthetase/stimulator of interferon genes signaling aggravated corneal allograft rejection through neutrophil extracellular traps

The activation of innate immunity following transplantation has been identified as a crucial factor in allograft inflammation and rejection. However, the role of cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)/stimulator of interferon genes (STING) signaling-mediated innate immunity in the pathogenesis of allograft rejection remains unclear. Utilizing a well-established murine model of corneal transplantation, we demonstrated increased expression of cGAS and STING in rejected-corneal allografts compared with syngeneic (Syn) and normal (Nor) corneas, along with significant activation of the cGAS/STING pathway, as evidenced by the enhanced phosphorylation of TANK-binding kinase 1and interferon regulatory factor 3. Pharmacological and genetic inhibition of cGAS/STING signaling markedly delayed corneal transplantation rejection, resulting in prolonged survival time and reduced inflammatory infiltration. Furthermore, we observed an increase in the formation of neutrophil extracellular traps (NETs) in rejected allografts, and the inhibition of NET formation through targeting peptidylarginine deiminase 4 and DNase I treatment significantly alleviated immune rejection and reduced cGAS/STING signaling activity. Conversely, subconjunctival injection of NETs accelerated corneal transplantation rejection and enhanced the activation of the cGAS/STING pathway. Collectively, these findings demonstrate that NETs contribute to the exacerbation of allograft rejection via cGAS/STING signaling, highlighting the targeting of the NETs/cGAS/STING signaling pathway as a potential strategy for prolonging allograft survival.

Dual modifying of MAVS at lysine 7 by SIRT3-catalyzed deacetylation and SIRT5-catalyzed desuccinylation orchestrates antiviral innate immunity

To effectively protect the host from viral infection while avoiding excessive immunopathology, the innate immune response must be tightly controlled. However, the precise regulation of antiviral innate immunity and the underlying mechanisms remain unclear. Here, we find that sirtuin3 (SIRT3) interacts with mitochondrial antiviral signaling protein (MAVS) to catalyze MAVS deacetylation at lysine residue 7 (K7), which promotes MAVS aggregation, as well as TANK-binding kinase I and IRF3 phosphorylation, resulting in increased MAVS activation and enhanced type I interferon signaling. Consistent with these findings, loss of Sirt3 in mice and zebrafish renders them more susceptible to viral infection compared to their wild-type (WT) siblings. However, Sirt3 and Sirt5 double-deficient mice exhibit the same viral susceptibility as their WT littermates, suggesting that loss of Sirt5 in Sirt3-deficient mice may counteract the increased viral susceptibility displayed in Sirt3-deficient mice. Thus, we not only demonstrate that SIRT3 positively regulates antiviral immunity in vitro and in vivo, likely via MAVS, but also uncover a previously unrecognized mechanism by which SIRT3 acts as an accelerator and SIRT5 as a brake to orchestrate antiviral innate immunity.

Viperin inhibits interferon-γ production to promote Mycobacterium tuberculosis survival by disrupting TBK1-IKKε-IRF3-axis and JAK-STAT signaling

Objectives and designAs an interferon-inducible protein, Viperin has broad-spectrum antiviral effects and regulation of host immune responses. We aim to investigate how Viperin regulates interferon-γ (IFN-γ) production in macrophages to control Mycobacterium tuberculosis (Mtb) infection.MethodsWe use Viperin deficient bone-marrow-derived macrophage (BMDM) to investigate the effects and machines of Viperin on Mtb infection.ResultsViperin inhibited IFN-γ production in macrophages and in the lung of mice to promote Mtb survival. Further insight into the mechanisms of Viperin-mediated regulation of IFN-γ production revealed the role of TANK-binding kinase 1 (TBK1), the TAK1-dependent inhibition of NF-kappa B kinase-epsilon (IKKε), and interferon regulatory factor 3 (IRF3). Inhibition of the TBK1-IKKε-IRF3 axis restored IFN-γ production reduced by Viperin knockout in BMDM and suppressed intracellular Mtb survival. Moreover, Viperin deficiency activated the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathway, which promoted IFN-γ production and inhibited Mtb infection in BMDM. Additionally, a combination of the anti-TB drug INH treatment in the absence of Viperin resulted in further IFN-γ production and anti-TB effect.ConclusionsThis study highlights the involvement of TBK1-IKKε-IRF3 axis and JAK-STAT signaling pathways in Viperin-suppressed IFN-γ production in Mtb infected macrophages, and identifies a novel mechanism of Viperin on negatively regulating host immune response to Mtb infection.

TANK Binding Kinase 1 Promotes BACH1 Degradation through Both Phosphorylation-Dependent and -Independent Mechanisms without Relying on Heme and FBXO22.

BTB and CNC homology 1 (BACH1) represses the expression of genes involved in the metabolism of iron, heme and reactive oxygen species. While BACH1 is rapidly degraded when it is bound to heme, it remains unclear how BACH1 degradation is regulated under other conditions. We found that FBXO22, a ubiquitin ligase previously reported to promote BACH1 degradation, polyubiquitinated BACH1 only in the presence of heme in a highly purified reconstitution assay. In parallel to this regulatory mechanism, TANK binding kinase 1 (TBK1), a protein kinase that activates innate immune response and regulates iron metabolism via ferritinophagy, was found to promote BACH1 degradation when overexpressed in 293T cells. While TBK1 phosphorylated BACH1 at multiple serine and threonine residues, BACH1 degradation was observed with not only the wild-type TBK1 but also catalytically impaired TBK1. The BACH1 degradation in response to catalytically impaired TBK1 was not dependent on FBXO22 but involved both autophagy-lysosome and ubiquitin-proteasome pathways judging from its suppression by using inhibitors of lysosome and proteasome. Chemical inhibition of TBK1 in hepatoma Hepa1 cells showed that TBK1 was not required for the heme-induced BACH1 degradation. Its inhibition in Namalwa B lymphoma cells increased endogenous BACH1 protein. These results suggest that TBK1 promotes BACH1 degradation in parallel to the FBXO22- and heme-dependent pathway, placing BACH1 as a downstream effector of TBK1 in iron metabolism or innate immune response.

Enteric coronavirus nsp2 is a virulence determinant that recruits NBR1 for autophagic targeting of TBK1 to diminish the innate immune response

ABSTRACT Non-structural protein 2 (nsp2) exists in all coronaviruses (CoVs), while its primary function in viral pathogenicity, is largely unclear. One such enteric CoV, porcine epidemic diarrhea virus (PEDV), causes high mortality in neonatal piglets worldwide. To determine the biological role of nsp2, we generated a PEDV mutant containing a complete nsp2 deletion (rPEDV-Δnsp2) from a highly pathogenic strain by reverse genetics, showing that nsp2 was dispensable for PEDV infection, while its deficiency reduced viral replication in vitro. Intriguingly, rPEDV-Δnsp2 was entirely avirulent in vivo, with significantly increased productions of IFNB (interferon beta) and IFN-stimulated genes (ISGs) in various intestinal tissues of challenged newborn piglets. Notably, nsp2 targets and degrades TBK1 (TANK binding kinase 1), the critical kinase in the innate immune response. Mechanistically, nsp2 induced the macroautophagy/autophagy process and recruited a selective autophagic receptor, NBR1 (NBR1 autophagy cargo receptor). NBR1 subsequently facilitated the K48-linked ubiquitination of TBK1 and delivered it for autophagosome-mediated degradation. Accordingly, the replication of rPEDV-Δnsp2 CoV was restrained by reduced autophagy and excess productions of type I IFNs and ISGs. Our data collectively define enteric CoV nsp2 as a novel virulence determinant, propose a crucial role of nsp2 in diminishing innate antiviral immunity by targeting TBK1 for NBR1-mediated selective autophagy, and pave the way to develop a new type of nsp2-based attenuated PEDV vaccine. The study also provides new insights into the prevention and treatment of other pathogenic CoVs. Abbreviations: 3-MA: 3-methyladenine; Baf A1: bafilomycin A1; CoV: coronavirus; CQ: chloroquine; dpi: days post-inoculation; DMVs: double-membrane vesicles; GABARAP: GABA type A receptor-associated protein; GFP: green fluorescent protein; GIGYF2: GRB10 interacting GYF protein 2; hpi: hours post-infection; IFA: immunofluorescence assay; IFIH1: interferon induced with helicase C domain 1; IFIT2: interferon induced protein with tetratricopeptide repeats 2; IFITM1: interferon induced transmembrane protein 1; IFNB: interferon beta; IRF3: interferon regulatory factor 3; ISGs: interferon-stimulated genes; mAb: monoclonal antibody; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAVS: mitochondrial antiviral signaling protein; NBR1: NBR1 autophagy cargo receptor; nsp2: non-structural protein 2; OAS1: 2’-5’-oligoadenylate synthetase 1; PEDV: porcine epidemic diarrhea virus; PRRs: pattern recognition receptors; RIGI: RNA sensor RIG-I; RT-qPCR: reverse transcription quantitative polymerase chain reaction; SQSTM1: sequestosome 1; TBK1: TANK binding kinase 1; TCID50: 50% tissue culture infectious doses; VSV: vesicular stomatitis virus.

ZO-1 Regulates Hippo-Independent YAP Activity and Cell Proliferation via a GEF-H1- and TBK1-Regulated Signalling Network.

Tight junctions are a barrier-forming cell-cell adhesion complex and have been proposed to regulate cell proliferation. However, the underlying mechanisms are not well understood. Here, we used cells deficient in the junction scaffold ZO-1 alone or together with its paralog ZO-2, which disrupts the junctional barrier. We found that ZO-1 knockout increased cell proliferation, induced loss of cell density-dependent proliferation control, and promoted apoptosis and necrosis. These phenotypes were enhanced by double ZO-1/ZO-2 knockout. Increased proliferation was dependent on two transcriptional regulators: YAP and ZONAB. ZO-1 knockout stimulated YAP nuclear translocation and activity without changes in Hippo-dependent phosphorylation. Knockout promoted TANK-binding kinase 1 (TBK1) activation and increased expression of the RhoA activator GEF-H1. Knockdown of ZO-3, another paralog interacting with ZO1, was sufficient to induce GEF-H1 expression and YAP activity. GEF-H1, TBK1, and mechanotransduction at focal adhesions were found to cooperate to activate YAP/TEAD in ZO-1-deficient cells. Thus, ZO-1 controled cell proliferation and Hippo-independent YAP activity by activating a GEF-H1- and TBK1-regulated mechanosensitive signalling network.

RCHY1 and OPTN are required for melanophagy, selective autophagy of melanosomes

Melanosomes are specific organelles dedicated to melanin synthesis and accumulation in melanocytes. Autophagy is suggestively involved in melanosome degradation, although the potential underlying molecular mechanisms remain elusive. In selective autophagy, autophagy receptors and E3-ligases are the key factors conferring cargo selectivity. In B16F10 cells, β-mangostin efficiently induced melanosome degradation without affecting other organelles such as mitochondria, peroxisomes, and the endoplasmic reticulum. Among various autophagy receptors, optineurin (OPTN) contributes TANK-binding kinase 1 (TBK1)-dependently to melanosome degradation and its knockdown inhibited β-mangostin-mediated melanosome degradation. OPTN translocation to melanosomes was dependent on its ubiquitin-binding domain. Moreover, OPTN-mediated TBK1 activation and subsequent TBK1-mediated S187 OPTN phosphorylation were essential for melanosome degradation. β-mangostin increased K63-linked melanosome ubiquitination. Finally, the E3-ligase RCHY1 knockdown inhibited the melanosome ubiquitination required for OPTN- and TBK1-phosphorylation as well as melanosome degradation. This study suggests that melanophagy, melanosome-selective autophagy, contributes to melanosome degradation, and OPTN and RCHY1 are an essential autophagy receptor and a E3-ligase, respectively, conferring cargo selectivity in melanophagy.

Abstract 4003: TBK1 inhibition enhances CAR-T cell efficacy against patient-derived organotypic tumor spheroids

Abstract Novel therapeutic strategies are needed to improve the efficacy of chimeric antigen receptor (CAR)-T cells in the treatment of solid tumors. Here, we set out to evaluate novel therapeutic strategies to improve the efficacy of B7-H3 (CD276) directed (B7-H3.CAR-T) using 3D microfluidic cultures of patient-derived organotypic tumor spheroids (PDOTS). PDOTS are generated from fresh patient tumor tissue and contain tumor cells, autologous immune cells and stromal cells, therefore recapitulating key features of the tumor microenvironment (TME), enabling the study of tumor-immune dynamics. We confirmed activity of B7-H3.CAR-T in PDOTS, although a strong correlation between B7-H3 expression and CAR-T efficacy was not observed. Mechanistic studies subsequently demonstrated dynamic upregulation of co-inhibitory receptors on CAR-T cells following target cell encounter leading to CAR-T cell dysfunction and limiting CAR-T efficacy in B7-H3 expressing tumors. PD-1 blockade restored CAR-T activity in monotypic and organotypic tumor spheroids with improved tumor control and upregulation of effector cytokines. Given the emerging role of TANK-binding kinase 1 (TBK1) as an immune evasion gene, we examined the effect of TBK1 inhibition on CAR-T efficacy. Similar to PD-1 blockade, TBK1 inhibition restored CAR-T activity in monotypic and organotypic tumor spheroids, prevented CAR-T cell dysfunction, and enhanced T cell proliferation. Inhibition or deletion of TBK1 also enhanced sensitivity of cancer cells to immune-mediated killing. Taken together, our results demonstrate the feasibility and utility of ex vivo profiling of CAR-T cells using PDOTS, and suggest that targeting TBK1 is a novel strategy to enhance CAR-T efficacy by overcoming tumor-intrinsic and -extrinsic resistance mechanisms. Citation Format: Luke Maggs, Yi Sun, Giulia Cattaneo, Marco Ventin, Feng Chen, Martin Q. Rasmussen, Xinhui Wang, Cristina R. Ferrone, Soldano Ferrone, Russell W. Jenkins. TBK1 inhibition enhances CAR-T cell efficacy against patient-derived organotypic tumor spheroids [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4003.

USP46 promotes the interferon antiviral signaling in black carp by deubiquitinating TBK1

Ubiquitin-specific peptidase 46 (USP46) functions as a deubiquitinating enzyme, facilitating the removal of ubiquitin molecules attached to substrate proteins and playing a critical role in cancer and neurodegenerative diseases. However, its function in innate antiviral immunity is unknown. In this study we cloned and identified bcUSP46, a homolog of USP46 from black carp. We discovered that overexpression of bcUSP46 enhanced the transcription of interferon (IFN) promoters and increased the expression of IFN, PKR, and Mx1. In addition, bcUSP46 knockdown significantly inhibited the expression of ISG genes, as well as the antiviral activity of the host cells. Interestingly, when bcUSP46 was co-expressed with the RLR factors, it significantly enhanced the activity of the IFN promoter mediated by these factors, especially TANK-binding kinase 1 (TBK1). The subsequent co-immunoprecipitation (co-IP) and immunofluorescence (IF) assay confirmed the association between bcUSP46 and bcTBK1. Noteworthily, co-expression of bcUSP46 with bcTBK1 led to an elevation of bcTBK1 protein level. Further analysis revealed that bcUSP46 stabilized bcTBK1 by eliminating the K48-linked ubiquitination of bcTBK1. Overall, our findings highlight the unique role of USP46 in modulating TBK1/IFN signaling and enrich our knowledge of the function of deubiquitination in regulating innate immunity in vertebrates.

A TBK1 variant causes autophagolysosomal and motoneuron pathology without neuroinflammation in mice.

Heterozygous mutations in the TBK1 gene can cause amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The majority of TBK1-ALS/FTD patients carry deleterious loss-of-expression mutations, and it is still unclear which TBK1 function leads to neurodegeneration. We investigated the impact of the pathogenic TBK1 missense variant p.E696K, which does not abolish protein expression, but leads to a selective loss of TBK1 binding to the autophagy adaptor protein and TBK1 substrate optineurin. Using organelle-specific proteomics, we found that in a knock-in mouse model and human iPSC-derived motor neurons, the p.E696K mutation causes presymptomatic onset of autophagolysosomal dysfunction in neurons precipitating the accumulation of damaged lysosomes. This is followed by a progressive, age-dependent motor neuron disease. Contrary to the phenotype of mice with full Tbk1 knock-out, RIPK/TNF-α-dependent hepatic, neuronal necroptosis, and overt autoinflammation were not detected. Our in vivo results indicate autophagolysosomal dysfunction as a trigger for neurodegeneration and a promising therapeutic target in TBK1-ALS/FTD.