OTULIN allies with LUBAC to govern angiogenesis by editing ALK1 linear polyubiquitin.

OTULIN coordinates with LUBAC to edit linear polyubiquitin chains in embryonic development, autoimmunity, and inflammatory diseases. However, the mechanism by which angiogenesis, especially that of endothelial cells (ECs), is regulated by linear ubiquitination remains unclear. Here, we reveal that constitutive or EC-specific deletion of Otulin resulted in arteriovenous malformations and embryonic lethality. LUBAC conjugates linear ubiquitin chains onto Activin receptor-like kinase 1 (ALK1), which is responsible for angiogenesis defects, inhibiting ALK1 enzyme activity and Smad1/5 activation. Conversely, OTULIN deubiquitinates ALK1 to promote Smad1/5 activation. Consistently, embryonic survival of Otulin-deficient mice was prolonged by BMP9 pretreatment or EC-specific ALK1Q200D (constitutively active) knockin. Moreover, mutant ALK1 from type 2 hereditary hemorrhagic telangiectasia (HHT2) patients exhibited excessive linear ubiquitination and increased HOIP binding. As such, a HOIP inhibitor restricted the excessive angiogenesis of ECs derived from ALK1G309S-expressing HHT2 patients. These results show that OTULIN and LUBAC govern ALK1 activity to balance EC angiogenesis.

Acetylation-mediated proteasomal degradation of core histones during DNA repair and spermatogenesis.

Histone acetylation plays critical roles in chromatin remodeling, DNA repair, and epigenetic regulation of gene expression, but the underlying mechanisms are unclear. Proteasomes usually catalyze ATP- and polyubiquitin-dependent proteolysis. Here, we show that the proteasomes containing the activator PA200 catalyze the polyubiquitin-independent degradation of histones. Most proteasomes in mammalian testes ("spermatoproteasomes") contain a spermatid/sperm-specific α subunit α4 s/PSMA8 and/or the catalytic ß subunits of immunoproteasomes in addition to PA200. Deletion of PA200 in mice abolishes acetylation-dependent degradation of somatic core histones during DNA double-strand breaks and delays core histone disappearance in elongated spermatids. Purified PA200 greatly promotes ATP-independent proteasomal degradation of the acetylated core histones, but not polyubiquitinated proteins. Furthermore, acetylation on histones is required for their binding to the bromodomain-like regions in PA200 and its yeast ortholog, Blm10. Thus, PA200/Blm10 specifically targets the core histones for acetylation-mediated degradation by proteasomes, providing mechanisms by which acetylation regulates histone degradation, DNA repair, and spermatogenesis.

Mycobacterium tuberculosis suppresses innate immunity by coopting the host ubiquitin system.

Mycobacterium tuberculosis PtpA, a secreted tyrosine phosphatase essential for tuberculosis pathogenicity, could be an ideal target for a drug against tuberculosis, but its active-site inhibitors lack selectivity over human phosphatases. Here we found that PtpA suppressed innate immunity dependent on pathways of the kinases Jnk and p38 and the transcription factor NF-κB by exploiting host ubiquitin. Binding of PtpA to ubiquitin via a region with no homology to human proteins activated it to dephosphorylate phosphorylated Jnk and p38, leading to suppression of innate immunity. Furthermore, the host adaptor TAB3 mediated NF-κB signaling by sensing ubiquitin chains, and PtpA blocked this process by competitively binding the ubiquitin-interacting domain of TAB3. Our findings reveal how pathogens subvert innate immunity by coopting host ubiquitin and suggest a potential tuberculosis treatment via targeting of ubiquitin-PtpA interfaces.

Pyroptosis modulation by bacterial effector proteins.

Pyroptosis is a proinflammatory form of programmed cell death featured with membrane pore formation that causes cellular swelling and allows the release of intracellular inflammatory mediators. This cell death process is elicited by the activation of the pore-forming proteins named gasdermins, and is intricately orchestrated by diverse regulatory factors in mammalian hosts to exert a prompt immune response against infections. However, growing evidence suggests that bacterial pathogens have evolved to regulate host pyroptosis for evading immune clearance and establishing progressive infection. In this review, we highlight current understandings of the functional role and regulatory network of pyroptosis in host antibacterial immunity. Thereafter, we further discuss the latest advances elucidating the mechanisms by which bacterial pathogens modulate pyroptosis through adopting their effector proteins to drive infections. A better understanding of regulatory mechanisms underlying pyroptosis at the interface of host-bacterial interactions will shed new light on the pathogenesis of infectious diseases and contribute to the development of promising therapeutic strategies against bacterial pathogens.

Mycobacterium tuberculosis protein kinase G acts as an unusual ubiquitinating enzyme to impair host immunity.

Upon Mycobacterium tuberculosis (Mtb) infection, protein kinase G (PknG), a eukaryotic-type serine-threonine protein kinase (STPK), is secreted into host macrophages to promote intracellular survival of the pathogen. However, the mechanisms underlying this PknG-host interaction remain unclear. Here, we demonstrate that PknG serves both as a ubiquitin-activating enzyme (E1) and a ubiquitin ligase (E3) to trigger the ubiquitination and degradation of tumor necrosis factor receptor-associated factor 2 (TRAF2) and TGF-ß-activated kinase 1 (TAK1), thereby inhibiting the activation of NF-κB signaling and host innate responses. PknG promotes the attachment of ubiquitin (Ub) to the ubiquitin-conjugating enzyme (E2) UbcH7 via an isopeptide bond (UbcH7 K82-Ub), rather than the usual C86-Ub thiol-ester bond. PknG induces the discharge of Ub from UbcH7 by acting as an isopeptidase, before attaching Ub to its substrates. These results demonstrate that PknG acts as an unusual ubiquitinating enzyme to remove key components of the innate immunity system, thus providing a potential target for tuberculosis treatment.

[COL4A5 genotypes and clinical characteristics of children with Alport syndrome]. / 儿童Alport综合征COL4A5åŸºå› åž‹åŠä¸´åºŠç‰¹ç‚¹åˆ†æž.

OBJECTIVES: To investigate the genotypes of the pathogenic gene COL4A5 and the characteristics of clinical phenotypes in children with Alport syndrome (AS). METHODS: A retrospective analysis was performed for the genetic testing results and clinical data of 19 AS children with COL4A5 gene mutations. RESULTS: Among the 19 children with AS caused by COL4A5 gene mutations, 1 (5%) carried a new mutation of the COL4A5 gene, i.e., c.3372A>G(p.P1124=) and presented with AS coexisting with IgA vasculitis nephritis; 3 children (16%) had large fragment deletion of the COL4A5 gene, among whom 2 children (case 7 had a new mutation site of loss51-53) had gross hematuria and albuminuria at the onset, and 1 child (case 13 had a new mutation site of loss3-53) only had microscopic hematuria, while the other 15 children (79%) had common clinical phenotypes of AS, among whom 7 carried new mutations of the COL4A5 gene. Among all 19 children, 3 children (16%) who carried COL4A5 gene mutations also had COL4A4 gene mutations, and 1 child (5%) had COL4A3 gene mutations. Among these children with double gene mutations, 2 had gross hematuria and proteinuria at the onset. CONCLUSIONS: This study expands the genotype and phenotype spectrums of the pathogenic gene COL4A5 for AS. Children with large fragment deletion of the COL4A5 gene or double gene mutations of COL4A5 with COL4A3 or COL4A4 tend to have more serious clinical manifestations.

HDAC6 contributes to human resistance against Mycobacterium tuberculosis infection via mediating innate immune responses.

Tuberculosis (TB), which is caused by Mycobacterium tuberculosis (Mtb), remains a major cause of morbidity and mortality worldwide. Increasing lines of evidence indicate that certain individuals, which are termed resisters, are naturally resistant to TB infection. The resister phenotype has been linked to host efficient innate immune responses, but the underlying mechanisms and the key immune factors remain unclear. Here, we find that upon Mtb infection, monocyte-derived macrophages (MDMs) from TB resisters exhibited distinctly higher production of TNF-α, IL-1ß and IL-6, higher ratio of bacteria in acidic vacuoles, and lower intracellular bacterial loads, as compared to that from the healthy controls, individuals with latent TB infection, and TB patients. Such enhanced anti-Mtb immune capacity of macrophages from resisters largely depends on histone deacetylase 6 (HDAC6), whose expression is specifically maintained in MDMs from TB resisters during Mtb infection. Furthermore, we demonstrate that HDAC6 is required for acidification of Mtb-containing phagosomes in macrophages, thus controlling the intracellular survival of Mtb. Taken together, these findings unravel an indispensable role of HDAC6 in human innate resistance against Mtb infection, suggesting that HDAC6 may serve as a marker for individual TB risk as well as a novel host-directed anti-TB therapeutic target.

Genetic spectrum of CAKUT and risk factors for kidney failure: a pediatric multicenter cohort study.

BACKGROUND: Congenital anomalies of the kidney and urinary tracts (CAKUT) are the leading cause of kidney failure in children with phenotypic and genotypic heterogeneity. Our objective was to describe the genetic spectrum and identify the risk factors for kidney failure in children with CAKUT. METHODS: Clinical and genetic data were derived from a multicenter network (Chinese Children Genetic Kidney Disease Database, CCGKDD) and the Chigene database. A total of 925 children with CAKUT who underwent genetic testing from 2014 to 2020 across China were studied. Data for a total of 584 children wereobtained from the CCGKDD, including longitudinal data regarding kidney function. The risk factors for kidney failure were determined by the Kaplan-Meier method and Cox proportional hazards models. RESULTS: A genetic diagnosis was established in 96 out of 925 (10.3%) children, including 72 (8%) with monogenic variants, 20 (2%) with copy number variants (CNVs), and 4 (0.4%)with major chromosomal anomalies. Patients with skeletal abnormalities were more likely to have large CNVs or abnormal karyotypes than monogenic variants. Eighty-two patients from the CCGKDD progressed to kidney failure at a median age of 13.0 (95% confidence interval, 12.4-13.6) years, and twenty-four were genetically diagnosed with variants of PAX2, TNXB, EYA1, HNF1B and GATA3 or the 48, XXYY karyotype. The multivariate analysis indicated that solitary kidney, posterior urethral valves, bilateral hypodysplasia, the presence of certain variants and premature birth were independent prognostic factors. CONCLUSIONS: The genetic spectrum of CAKUT varies among different subphenotypes. The identified factors indicate areas that require special attention.

The mechanism and effects of remdesivir-induced developmental toxicity in zebrafish: Blood flow dysfunction and behavioral alterations.

The antiviral drug remdesivir has been used to treat the growing number of coronavirus disease 2019 (COVID-19) patients. However, the drug is mainly excreted through urine and feces and introduced into the environment to affect non-target organisms, including fish, which has raised concerns about potential ecotoxicological effects on aquatic organisms. Moreover, studies on the ecological impacts of remdesivir on aquatic environments have not been reported. Here, we aimed to explore the toxicological impacts of microinjection of remdesivir on zebrafish early embryonic development and larvae and the associated mechanism. We found that 100 µM remdesivir delayed epiboly and impaired convergent movement of embryos during gastrulation, and dose-dependent increases in mortality and malformation were observed in remdesivir-treated embryos. Moreover, 10-100 µM remdesivir decreased blood flow and swimming velocity and altered the behavior of larvae. In terms of molecular mechanisms, 80 differentially expressed genes (DEGs) were identified by transcriptome analysis in the remdesivir-treated group. Some of these DEGs, such as manf, kif3a, hnf1ba, rgn, prkcz, egr1, fosab, nr4a1, and ptgs2b, were mainly involved in early embryonic development, neuronal developmental disorders, vascular disease and the blood flow pathway. These data reveal that remdesivir can impair early embryonic development, blood flow and behavior of zebrafish embryos/larvae, probably due to alterations at the transcriptome level. This study suggests that it is important to avoid the discharge of remdesivir to aquatic ecosystems and provides a theoretical foundation to hinder remdesivir-induced ecotoxicity to aquatic environments.

SIP/CacyBP promotes autophagy by regulating levels of BRUCE/Apollon, which stimulates LC3-I degradation.

BRUCE/Apollon is a membrane-associated inhibitor of apoptosis protein that is essential for viability and has ubiquitin-conjugating activity. On initiation of apoptosis, the ubiquitin ligase Nrdp1/RNF41 promotes proteasomal degradation of BRUCE. Here we demonstrate that BRUCE together with the proteasome activator PA28γ causes proteasomal degradation of LC3-I and thus inhibits autophagy. LC3-I on the phagophore membrane is conjugated to phosphatidylethanolamine to form LC3-II, which is required for the formation of autophagosomes and selective recruitment of substrates. SIP/CacyBP is a ubiquitination-related protein that is highly expressed in neurons and various tumors. Under normal conditions, SIP inhibits the ubiquitination and degradation of BRUCE, probably by blocking the binding of Nrdp1 to BRUCE. On DNA damage by topoisomerase inhibitors, Nrdp1 causes monoubiquitination of SIP and thus promotes apoptosis. However, on starvation, SIP together with Rab8 enhances the translocation of BRUCE into the recycling endosome, formation of autophagosomes, and degradation of BRUCE by optineurin-mediated autophagy. Accordingly, deletion of SIP in cultured cells reduces the autophagic degradation of damaged mitochondria and cytosolic protein aggregates. Thus, by stimulating proteasomal degradation of LC3-I, BRUCE also inhibits autophagy. Conversely, SIP promotes autophagy by blocking BRUCE-dependent degradation of LC3-I and by enhancing autophagosome formation and autophagic destruction of BRUCE. These actions of BRUCE and SIP represent mechanisms that link the regulation of autophagy and apoptosis under different conditions.

Host defense mechanisms against Mycobacterium tuberculosis.

Tuberculosis (TB), which is caused by Mycobacterium tuberculosis (Mtb), remains the leading cause of death worldwide from a single infectious pathogen. Mtb is a paradigmatic intracellular pathogen that primarily invades the lungs after host inhalation of bacteria-containing droplets via the airway. However, the majority of Mtb-exposed individuals can spontaneously control the infection by virtue of a robust immune defense system. The mucosal barriers of the respiratory tract shape the first-line defense against Mtb through various mucosal immune responses. After arriving at the alveoli, the surviving mycobacteria further encounter a set of host innate immune cells that exert multiple cellular bactericidal functions. Adaptive immunity, predominantly mediated by a range of different T cell and B cell subsets, is subsequently activated and participates in host anti-mycobacterial defense. During Mtb infection, host bactericidal immune responses are exquisitely adjusted and balanced by multifaceted mechanisms, including genetic and epigenetic regulation, metabolic regulation and neuroendocrine regulation, which are indispensable for maintaining host immune efficiency and avoiding excessive tissue injury. A better understanding of the integrated and equilibrated host immune defense system against Mtb will contribute to the development of rational TB treatment regimens especially novel host-directed therapeutics.

Mycobacterium tuberculosis Mce3C promotes mycobacteria entry into macrophages through activation of ß2 integrin-mediated signalling pathway.

Establishment of infection by facultative intracellular pathogen Mycobacterium tuberculosis (Mtb) requires adherence to and internalisation by macrophages. However, the effector molecules exploited by Mtb for entry into macrophages remain to be fully understood. The mammalian cell entry (Mce) proteins play an essential role in facilitating the internalisation of mycobacteria into mammalian cells. Here, we characterized Mtb Mce3C as a new mycobacterial surface protein that could promote mycobacterial adhesion to and invasion of macrophages in an RGD motif-dependent manner. We then further demonstrated that ß2 integrin was required for Mce3C-mediated cell entry. In addition, we found that binding of Mce3C recruited ß2 integrin-dependent signalling adaptors and induced local actin rearrangement at the site of mycobacterial invasion. By using specific antibodies and pharmacological inhibitors, we further demonstrated the involvement of Src-family tyrosine kinases, spleen tyrosine kinase, Vav, Rho, and Rho-associated kinase in Mce3C-mediated mycobacterial invasion. Our results reveal a novel mechanism by which Mtb Mce3C exploits integrin-mediated signalling cascade for Mce, providing potential targets for the development of therapies against Mtb infection.

Mycobacterium tuberculosis Mce3E suppresses host innate immune responses by targeting ERK1/2 signaling.

Crucial to the pathogenesis of the tuberculosis (TB)-causing pathogen Mycobacterium tuberculosis is its ability to subvert host immune defenses to promote its intracellular survival. The mammalian cell entry protein 3E (Mce3E), located in the region of difference 15 of the M. tuberculosis genome and absent in Mycobacterium bovis bacillus Calmette-Guérin, has an essential role in facilitating the internalization of mammalian cells by mycobacteria. However, relatively little is known about the role of Mce3E in modulation of host innate immune responses. In this study, we demonstrate that Mce3E inhibits the activation of the ERK1/2 signaling pathway, leading to the suppression of Tnf and Il6 expression, and the promotion of mycobacterial survival within macrophages. Mce3E interacts and colocalizes with ERK1/2 at the endoplasmic reticulum in a DEF motif (an ERK-docking motif)-dependent manner, relocates ERK1/2 from cytoplasm to the endoplasmic reticulum, and finally reduces the association of ERK1/2 with MEK1 and blocks the nuclear translocation of phospho-ERK1/2. A DEF motif mutant form of Mce3E (F294A) loses its ability to suppress Tnf and Il6 expression and to promote intracellular survival of mycobacteria. Inhibition of the ERK1/2 pathway in macrophages using U0126, a specific inhibitor of the ERK pathway, also leads to the suppressed Tnf and Il6 expression and the enhanced intracellular survival of mycobacteria. Taken together, these results suggest that M. tuberculosis Mce3E exploits the ERK1/2 signaling pathway to suppress host innate immune responses, providing a potential Mce3E-ERK1/2 interface-based drug target against M. tuberculosis.

Comparative genomic analysis of Mycobacterium tuberculosis clinical isolates.

BACKGROUND: Due to excessive antibiotic use, drug-resistant Mycobacterium tuberculosis has become a serious public health threat and a major obstacle to disease control in many countries. To better understand the evolution of drug-resistant M. tuberculosis strains, we performed whole genome sequencing for 7 M. tuberculosis clinical isolates with different antibiotic resistance profiles and conducted comparative genomic analysis of gene variations among them. RESULTS: We observed that all 7 M. tuberculosis clinical isolates with different levels of drug resistance harbored similar numbers of SNPs, ranging from 1409-1464. The numbers of insertion/deletions (Indels) identified in the 7 isolates were also similar, ranging from 56 to 101. A total of 39 types of mutations were identified in drug resistance-associated loci, including 14 previously reported ones and 25 newly identified ones. Sixteen of the identified large Indels spanned PE-PPE-PGRS genes, which represents a major source of antigenic variability. Aside from SNPs and Indels, a CRISPR locus with varied spacers was observed in all 7 clinical isolates, suggesting that they might play an important role in plasticity of the M. tuberculosis genome. The nucleotide diversity (Л value) and selection intensity (dN/dS value) of the whole genome sequences of the 7 isolates were similar. The dN/dS values were less than 1 for all 7 isolates (range from 0.608885 to 0.637365), supporting the notion that M. tuberculosis genomes undergo purifying selection. The Л values and dN/dS values were comparable between drug-susceptible and drug-resistant strains. CONCLUSIONS: In this study, we show that clinical M. tuberculosis isolates exhibit distinct variations in terms of the distribution of SNP, Indels, CRISPR-cas locus, as well as the nucleotide diversity and selection intensity, but there are no generalizable differences between drug-susceptible and drug-resistant isolates on the genomic scale. Our study provides evidence strengthening the notion that the evolution of drug resistance among clinical M. tuberculosis isolates is clearly a complex and diversified process.

TRIM27 elicits protective immunity against tuberculosis by activating TFEB-mediated autophagy flux.

Infectious diseases, such as Mycobacterium tuberculosis (Mtb)-caused tuberculosis (TB), remain a global threat exacerbated by increasing drug resistance. Host-directed therapy (HDT) is a promising strategy for infection treatment through targeting host immunity. However, the limited understanding of the function and regulatory mechanism of host factors involved in immune defense against infections has impeded HDT development. Here, we identify the ubiquitin ligase (E3) TRIM27 (tripartite motif-containing 27) as a host protective factor against Mtb by enhancing host macroautophagy/autophagy flux in an E3 ligase activity-independent manner. Mechanistically, upon Mtb infection, nuclear-localized TRIM27 increases and functions as a transcription activator of TFEB (transcription factor EB). Specifically, TRIM27 binds to the TFEB promoter and the TFEB transcription factor CREB1 (cAMP responsive element binding protein 1), thus enhancing CREB1-TFEB promoter binding affinity and promoting CREB1 transcription activity toward TFEB, eventually inducing autophagy-related gene expression as well as autophagy flux activation to clear the pathogen. Furthermore, TFEB activator 1 can rescue TRIM27 deficiency-caused decreased autophagy-related gene transcription and attenuated autophagy flux, and accordingly suppressed the intracellular survival of Mtb in cell and mouse models. Taken together, our data reveal that TRIM27 is a host defense factor against Mtb, and the TRIM27-CREB1-TFEB axis is a potential HDT-based TB target that can enhance host autophagy flux.Abbreviations: ATG5: autophagy related 5; BMDMs: bone marrow-derived macrophages; CFU: colony-forming unit; ChIP-seq: chromatin immunoprecipitation followed by sequencing; CREB1: cAMP responsive element binding protein 1; CTSB: cathepsin B; E3: ubiquitin ligase; EMSA: electrophoretic mobility shift assay; HC: healthy control; HDT: host-directed therapy; LAMP: lysosomal associated membrane protein; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MCOLN1: mucolipin TPR cation channel 1; Mtb: Mycobacterium tuberculosis; NLS: nuclear localization signal; PBMCs: peripheral blood mononuclear cells; PRKA/PKA: protein kinase cAMP-activated; qRT-PCR: quantitative real-time PCR; RFP: RET finger protein; TB: tuberculosis; TBK1: TANK binding kinase 1; TFEB: transcription factor EB; TRIM: tripartite motif; TSS: transcription start site; ULK1: unc-51 like autophagy activating kinase 1.

Systematic HOIP interactome profiling reveals critical roles of linear ubiquitination in tissue homeostasis.

Linear ubiquitination catalyzed by HOIL-1-interacting protein (HOIP), the key component of the linear ubiquitination assembly complex, plays fundamental roles in tissue homeostasis by executing domain-specific regulatory functions. However, a proteome-wide analysis of the domain-specific interactome of HOIP across tissues is lacking. Here, we present a comprehensive mass spectrometry-based interactome profiling of four HOIP domains in nine mouse tissues. The interaction dataset provides a high-quality HOIP interactome resource with an average of approximately 90 interactors for each bait per tissue. HOIP tissue interactome presents a systematic understanding of linear ubiquitination functions in each tissue and also shows associations of tissue functions to genetic diseases. HOIP domain interactome characterizes a set of previously undefined linear ubiquitinated substrates and elucidates the cross-talk among HOIP domains in physiological and pathological processes. Moreover, we show that linear ubiquitination of Integrin-linked protein kinase (ILK) decreases focal adhesion formation and promotes the detachment of Shigella flexneri-infected cells. Meanwhile, Hoip deficiency decreases the linear ubiquitination of Smad ubiquitination regulatory factor 1 (SMURF1) and enhances its E3 activity, finally causing a reduced bone mass phenotype in mice. Overall, our work expands the knowledge of HOIP-interacting proteins and provides a platform for further discovery of linear ubiquitination functions in tissue homeostasis.

Fungicide-tolerant persister formation during cryptococcal pulmonary infection.

Bacterial persisters, a subpopulation of genetically susceptible cells that are normally dormant and tolerant to bactericides, have been studied extensively because of their clinical importance. In comparison, much less is known about the determinants underlying fungicide-tolerant fungal persister formation in vivo. Here, we report that during mouse lung infection, Cryptococcus neoformans forms persisters that are highly tolerant to amphotericin B (AmB), the standard of care for treating cryptococcosis. By exploring stationary-phase indicator molecules and developing single-cell tracking strategies, we show that in the lung, AmB persisters are enriched in cryptococcal cells that abundantly produce stationary-phase molecules. The antioxidant ergothioneine plays a specific and key role in AmB persistence, which is conserved in phylogenetically distant fungi. Furthermore, the antidepressant sertraline (SRT) shows potent activity specifically against cryptococcal AmB persisters. Our results provide evidence for and the determinant of AmB-tolerant persister formation in pulmonary cryptococcosis, which has potential clinical significance.

TRIM27 maintains gut homeostasis by promoting intestinal stem cell self-renewal.

Dysregulation of gut homeostasis is associated with irritable bowel syndrome (IBS), a chronic functional gastrointestinal disorder affecting approximately 11.2% of the global population. The poorly understood pathogenesis of IBS has impeded its treatment. Here, we report that the E3 ubiquitin ligase tripartite motif-containing 27 (TRIM27) is weakly expressed in IBS but highly expressed in inflammatory bowel disease (IBD), a frequent chronic organic gastrointestinal disorder. Accordingly, knockout of Trim27 in mice causes spontaneously occurring IBS-like symptoms, including increased visceral hyperalgesia and abnormal stool features, as observed in IBS patients. Mechanistically, TRIM27 stabilizes ß-catenin and thus activates Wnt/ß-catenin signaling to promote intestinal stem cell (ISC) self-renewal. Consistent with these findings, Trim27 deficiency disrupts organoid formation, which is rescued by reintroducing TRIM27 or ß-catenin. Furthermore, Wnt/ß-catenin signaling activator treatment ameliorates IBS symptoms by promoting ISC self-renewal. Taken together, these data indicate that TRIM27 is critical for maintaining gut homeostasis, suggesting that targeting the TRIM27/Wnt/ß-catenin axis could be a potential treatment strategy for IBS. Our study also indicates that TRIM27 might serve as a potential biomarker for differentiating IBS from IBD.

Mycobacterium tuberculosis hijacks host TRIM21- and NCOA4-dependent ferritinophagy to enhance intracellular growth.

Ferritin, a key regulator of iron homeostasis in macrophages, has been reported to confer host defenses against Mycobacterium tuberculosis (Mtb) infection. Nuclear receptor coactivator 4 (NCOA4) was recently identified as a cargo receptor in ferritin degradation. Here, we show that Mtb infection enhanced NCOA4-mediated ferritin degradation in macrophages, which in turn increased the bioavailability of iron to intracellular Mtb and therefore promoted bacterial growth. Of clinical relevance, the upregulation of FTH1 in macrophages was associated with tuberculosis (TB) disease progression in humans. Mechanistically, Mtb infection enhanced NCOA4-mediated ferritin degradation through p38/AKT1- and TRIM21-mediated proteasomal degradation of HERC2, an E3 ligase of NCOA4. Finally, we confirmed that NCOA4 deficiency in myeloid cells expedites the clearance of Mtb infection in a murine model. Together, our findings revealed a strategy by which Mtb hijacks host ferritin metabolism for its own intracellular survival. Therefore, this represents a potential target for host-directed therapy against tuberculosis.

A Golgi-resident GPR108 cooperates with E3 ubiquitin ligase Smurf1 to suppress antiviral innate immunity.

The regulation of antiviral immunity is crucial in maintaining host immune homeostasis, a process that involves dynamic modulations of host organelles. The Golgi apparatus is increasingly perceived as a host organelle functioning as a critical platform for innate immunity, but the detailed mechanism by which it regulates antiviral immunity remains elusive. Here, we identify the Golgi-localized G protein-coupled receptor 108 (GPR108) as a regulator of type Ι interferon responses by targeting interferon regulatory factor 3 (IRF3). Mechanistically, GPR108 enhances the ubiquitin ligase Smad ubiquitylation regulatory factor 1 (Smurf1)-mediated K63-linked polyubiquitination of phosphorylated IRF3 for nuclear dot 10 protein 52 (NDP52)-dependent autophagic degradation, leading to suppression of antiviral immune responses against DNA or RNA viruses. Taken together, our study provides insight into the crosstalk between the Golgi apparatus and antiviral immunity via a dynamic and spatiotemporal regulation of GPR108-Smurf1 axis, thereby indicating a potential target for treating viral infection.