Biology subjects

Liang, Y.

Publications and source records attributed to Liang, Y..

At least 127 records · Page 7Linked to original sources

bioRxiv2025

Structure of mycobacterial NDH-2 bound to a 2-mercapto-quinazolinone inhibitor

The mycobacterial type II NADH dehydrogenase (NDH-2) is a promising drug target because of its central role in energy metabolism in Mycobacterium tuberculosis and other pathogens, and because it lacks a known mammalian homologue. However, the absence of structural information on how the enzyme binds inhibitors has made optimization of lead compounds challenging. We used electron cryomicroscopy (cryo-EM) to determine the structure of NDH-2 from Mycobacterium smegmatis, a fast-growing non-pathogenic model for respiration in M. tuberculosis, both alone and in complex with a 2-mercapto-quinazolinone inhibitor. The structure shows that active mycobacterial NDH-2 is dimeric, with the dimerization interface stabilized by an extended C-terminal helix not found in NDH-2 from other bacterial genera. The arrangement of monomers in the dimer differs from the arrangement described for other prokaryotic NDH-2 dimers, instead resembling dimers formed by NDH-2 in eukaryotes. Density for the 2-mercapto-quinazolinone in the menaquinone-binding site shows that the inhibitor blocks menaquinone reduction through direct interaction with the flavin adenine dinucleotide cofactor. These results reveal structural elements of NDH-2 that could be used to design specific inhibitors of the mycobacterial enzyme.

biochemistry↗

bioRxiv2025

Maturase K forms a plastidial splicing complex with a neofunctionalized branching enzyme

Chloroplast group IIA introns derive from bacterial ribozymes. Their splicing likely requires Maturase K (MatK), which has been largely inaccessible to functional analyses being itself a chloroplast intron-encoded protein. Here we show that MatK physically interacts with a conserved, essential plastid-localized homolog of starch-branching enzymes (BEs), dubbed MATURASE K INTERACTING PROTEIN1 (MKIP1). We demonstrate that MKIP1 proteins have lost BE activity and acquired an insertion enabling direct interaction with the N-terminal region of MatK. Arabidopsis MKIP1 specifically co-precipitates all known intron targets of MatK. Induced MKIP1 silencing results in pale newly emerging leaves, in which the splicing of these intron targets is strongly reduced. Our data suggest that MKIP1 functionally diverged from canonical BEs to facilitate splicing in conjunction with MatK. We propose that the N-terminus of MatK, in turn, has evolved from an RNA-binding domain into a platform for protein interaction, helping its transition towards a general splicing factor.

plant biology↗

bioRxiv2025

ORP2 regulates free cholesterol accumulation in hepatocytes during MASH

BackgroundCholesterol crystals in hepatocytes are known to strongly associate with human Metabolic Dysfunction-Associated Steatohepatitis (MASH). However, it remains unclear which molecular pathway(s) regulates free cholesterol accumulation, and therefore the formation of cholesterol crystals in hepatocytes. In cultured cell lines, oxysterol-binding protein-related protein 2 (ORP2) functions to deliver cholesterol to the plasma membrane from internal organelles. MethodsHere, we generated liver-specific ORP2 knockout (ORP2-LKO) mice and characterized their metabolic phenotypes on chow and high fat diet. ResultsThe ORP2-LKO mice developed much more severe hepatic steatosis than wild type mice after high-fat diet feeding. They also demonstrated more severe liver inflammation and damage. Notably, free but not esterified cholesterol, as well as cholesterol crystals accumulated in ORP2-LKO liver. The expression of Cyp7a1 was significantly upregulated in ORP2-LKO liver, accompanied with accumulation of taurocholic acid. Our results thus unveil an important in vivo function of ORP2 in preventing free cholesterol from accumulating in mouse liver. Conclusionsour results suggest that impaired cholesterol trafficking may enhance the deposition of cholesterol crystals in hepatocytes, promoting the development of MASH.

cell biology↗

bioRxiv2024

Cell fate specification modes shape transcriptome evolution in the highly conserved spiral cleavage

Early animal development can be remarkably variable, influenced by lineage-specific reproductive strategies and adaptations. Yet, early embryogenesis is also strikingly conserved in some groups, like Spiralia (e.g., snails, clams, and many marine worms). In this large clade, a shared cleavage program -- the so-called spiral cleavage -- and similar cell lineages are ancestral to at least seven animal phyla. Why early development is so conserved in specific groups and plastic in others is not fully understood. Here, we investigated two annelid species -- Owenia fusiformis and Capitella teleta -- with spiral cleavage but different modes of specifying their primary progenitor cells. By generating high-resolution transcriptomic time courses from the oocyte and fertilisation until gastrulation, we show transcriptional dynamics are markedly different between these species during spiral cleavage and instead reflect their distinct timings of embryonic organiser specification. However, the end of cleavage and gastrulation exhibit high transcriptomic similarity. At these stages, orthologous transcription factors share gene expression domains, suggesting this period is a previously overlooked mid-developmental transition in annelid embryogenesis. Together, our data reveal hidden developmental plasticity in the genetics underpinning spiral cleavage, indicating an evolutionary decoupling of morphological and transcriptomic conservation during early animal embryogenesis.

developmental biology↗

bioRxiv2024

PPARδ restrains the suppression function of intra-tumoral Tregs by limiting CIITA-MHC II expression

Regulatory T cells (Treg cells) play a critical role in suppressing anti-tumor immunity, often resulting in unfavorable clinical outcomes across numerous cancers. However, systemic Treg depletion, while augmenting anti-tumor responses, also triggers detrimental autoimmune disorders. Thus, dissecting the mechanisms by which Treg cells navigate and exert their functions within the tumor microenvironment (TME) is pivotal for devising innovative Treg-centric cancer therapies. Our study highlights the role of peroxisome proliferator-activated receptor {beta}/{delta} (PPAR{delta}), a nuclear hormone receptor involved in fatty acid metabolism. Remarkably, PPAR{delta} ablation in Treg escalated tumor growth and augmented the immunosuppressive characteristics of the TME. This absence of PPAR{delta} spurred an increased expression of genes central to antigen presentation, notably CIITA and MHC II. Our results showcase a novel association where the absence of CIITA in PPAR{delta}-deficient Treg bolsters anti-tumor responses, casting CIITA as a pivotal downstream regulator of PPAR{delta} within Treg. In vitro assays demonstrated that elevated CIITA levels enhance the suppressive capacity of Treg, facilitated by an antigen-independent interaction between Treg-MHC II and Tconv-TCR/CD4/Lag3. A significant revelation was the role of type 1 interferon as a TME signal that promotes the genesis of MHC II+ Treg; PPAR{delta} deficiency intensifies this phenomenon by amplifying type 1 interferon signaling, mediated by a notable upsurge in JAK3 transcription and an increase of pSTAT1-Y701. In conclusion, the co-regulation between TME cues and PPAR{delta} signaling shapes the adaptive and suppressive roles of Treg cells through the CIITA-MHC II pathway. Strategically targeting the potent MHC II+ Treg population could open a new avenue for cancer therapies by boosting anti-tumor defenses while curbing autoimmune threats. HighlightsO_LIPPAR{delta} Treg conditional knockout mice show accelerated tumor growth due to increased expression of CIITA-MHC II. C_LIO_LIType I interferon signal regulates Treg CIITA-MHC II axis in vitro and in vivo. C_LIO_LIPPAR{delta} attenuates Type I interferon response and restrains CIITA-MHC II expression in Treg cells. C_LIO_LITreg suppressive function is enhanced by Treg MHC IIs direct interaction with TCR/CD4/Lag3 on Teff cells. C_LI

immunology↗

bioRxiv2024

Recombinant Pichinde reporter virus as a safe and suitable surrogate for high-throughput antiviral screening against highly pathogenic arenaviruses

Several arenaviruses, such as the Old World (OW) Lassa virus (LASV) and the New World (NW) Junin virus (JUNV), can cause severe and lethal viral hemorrhagic fevers in humans. Currently, no vaccines or specific antiviral therapies are FDA-approved for treating arenavirus infections. One major challenge for the development of new therapeutic candidates against these highly pathogenic viruses is that they are BSL-3/4 pathogens that need to be handled in high biocontainment laboratories. In this work, a recombinant non-pathogenic New World arenavirus, Pichinde virus (rPICV), was used for the development of a high-throughput screening (HTS) assay in the BSL-2 laboratory for the screening and identification of small molecule inhibitors against arenaviruses. The rPICV is a replication-competent virus expressing the firefly luciferase reporter gene in the infected cells proportionally to the infection rate. rPICV infection was optimized for an automated HTS in 384-well format with robust Z' scores, high signal-to-background ratios, and low intrinsic variance. Screening an established library allowed for the identification of five top hit compounds, which included ribavirin, a known inhibitor of arenaviral RNA synthesis, showing good potency and selectivity in inhibiting rPICV replication. The antiviral activity of the top hit compounds was further validated against another recombinant arenavirus, the OW lymphocytic choriomeningitis virus (rLCMV) and against laboratory strains of LASV (Josiah) and JUNV (Romero). The use of rPICV in the HTS-based antiviral assay under BSL-2 condition has proven to be safe and suitable for the identification of broad-spectrum small molecule inhibitors against highly pathogenic arenaviruses.

microbiology↗

bioRxiv2024

Natural monoclonal autoantibodies against HERV-K102 Envelope-TM from SLE patients selectively eliminate autoreactive immune cells and cancer cells

In sharp contrast to immune dysfunction in cancer, autoimmune diseases such as systemic lupus erythematosus (SLE) exhibit excessive immune reactions characterized by high titers of autoantibodies to HERV-K102-envelope (HERV-K102-Env) neoantigens, which are frequently found in cancer patients but seldom elicit a strong immune response. Here we aim to address whether anti-HERV-K102-Env autoantibodies in SLE can effectively eliminate autoreactive immune cells and cancer cells expressing HERV-K102-Env neoantigens. We established world-first fully human autoantibody phage display library with 3.67x108 cfu using peripheral blood mononuclear cells (PBMCs) from SLE patients. Through high-throughput screening, we identified nineteen monoclonal autoantibodies (mAbs) targeting the conserved HERV-K102 Env-TM subunit. The EC50 values of these autoantibodies binding to the HERV-K102 Env-TM subunit ranged from 0.002436 g/ml to 1.798 g/ml. Remarkably, eleven of these mAbs not only recognized the HERV-K102 Env-TM glycoprotein on the cell surface but also effectively eliminated autoreactive B, T, and natural killer (NK) cells in SLE, as well as cancer cells. Our findings provide a conceptually new immunotherapy target HERV-K102 Env-TM subunit and open the era of using natural human autoantibodies to treat autoimmune disease and cancers. Several of these monoclonal autoantibodies show promise as potential diagnostic and therapeutic agents, paving the way for innovative approaches to treating SLE and various malignancies.

immunology↗

bioRxiv2024

Assessment of DNA methylation from a single genomic region of ELOV2 is sufficient to predict chronological age

Estimation of chronological age is particularly informative in forensic contexts. Assessment of DNA methylation status allows for the prediction of age, though the accuracy and ease of manipulation may vary across different models. In this study, we started with a carefully designed discovery cohort recruiting more elderly subjects than other age categories, to diminish the effect of epigenetic drifting. We analyzed DNA methylation from a single genomic region of ELOV2, which was sufficient to construct an age-prediction model comprising 15 CpG sites. This model is further validated by an independent cohort as well as a multi-center test using trace dried bloodstains. The nature of our analytical pipeline, when combined the assessment of a single genomic locus with high-throughput sequencing, can easily be scaled up with low cost. Taken together, we propose a new age-prediction model featuring accuracy, ease of manipulation, high-throughput, and low cost. This model can be readily applied in both classic and newly emergent forensic contexts that require age estimation.

genetics↗

bioRxiv2024

Gut microbiota-derived GlcNAc-MurNAc is a TLR4 agonist that protects the host gut

Gut microbiota-derived peptidoglycan fragments (PGNs) are key signaling molecules that regulate multiple aspects of the hosts health. Yet the exact structures of natural PGNs in hosts have not been fully elucidated. Herein, we developed an LC-HRMS/MS analytical platform for global quantification and profiling of natural PGN subtypes in host gut and sera, unexpectedly revealing the abundance of PGN-derived saccharide moieties that do not resemble canonical ligands of mammalian NOD1/2 receptors. Focusing on the disaccharide GlcNAc-MurNAc (GM), a natural gut PGN that does not activate NOD1/2 yet still exhibits robust immunostimulatory effects in host immune cells, we unambiguously established GM as a TLR4 agonist, adding to the growing knowledge of NOD-independent mechanisms of PGN sensing in hosts. Importantly, the administration of GM effectively mitigates colonic inflammation in the DSS-induced colitis model in mice via TLR4-dependent mechanisms, highlighting the in vivo significance of natural gut microbiota-derived PGNs in maintaining host intestinal homeostasis.

biochemistry↗

bioRxiv2024

The virulence and motility of Pseudomonas syringae pv. Actinidiae mediated by a temperature sensor HktS-HktR

Kiwifruit bacterial canker (KBC), caused by Pseudomonas syringae pv. actinidiae (Psa) is one of the most devastating diseases of kiwifruit and can damage almost all kiwifruit varieties. The severity of the disease occurrence is closely related to the temperature. Our previous research indicated that Psa showed stronger pathogenicity and expansion ability at relatively cool temperatures, but how Psa senses environmental temperature and regulates its virulence mechanism remains unclear. In this study, 69 Histidine kinases (HK) in Psa were predicted through bioinformatics analysis, and 9 differentially expressed HK genes were identified at varying temperatures through pathogenicity detection and quantitative reverse transcription PCR (qRT-PCR). Among them, HktS as a temperature signal receiver was identified, and its response regulator (RR) HktR was determined through structure analysis and cotranscription assay. The results showed that HktR can bind to transcription factor RpoD, and RpoD bind to hrpRS promoter region, thus initiating the expression level of the type III secretion system (T3SS), which plays an important role in the pathogenesis of Psa. In addition, the motility of Psa was also regulated by HktS-HktR in a temperature-dependent manner. These findings reveal the molecular mechanism by which HktS-HktR acts as a temperature sensor to regulate bacterial virulence and motility of Psa, providing a new potential target for KBC control.

microbiology↗

bioRxiv2024

Agouti and BMP signaling drive a naturally occurring fate conversion of melanophores to leucophores in zebrafish

The often-prominent pigment patterns of vertebrates are varied in form and function and depend on several types of pigment cells derived from embryonic neural crest or latent stem cells of neural crest origin. These cells and the patterns they produce have been useful for uncovering features of differentiation and morphogenesis that underlie adult phenotypes, and they offer opportunities to discover how patterns and the cell types themselves have diversified. In zebrafish, a body pattern of stripes arises by self organizing interactions among three types of pigment cells. Yet these fish also exhibit white ornamentation on their fins that depends on the transdifferentiation of black melanophores to white cells, "melanoleucophores." To identify mechanisms underlying this conversion we used ultrastructural, transcriptomic, mutational and other approaches. We show that melanophore- melanoleucophore transition depends on regional BMP signals transduced through non-canonical receptors (Rgmb-Neo1a-Lrig2) as well as BMP-dependent signaling by Agouti genes, asip1 and asip2b. These signals lead to expression of transcription factor genes including foxd3 and runx3 that are necessary to induce loss of melanin by an autophagy-like process, curtail new melanin production, and deploy a pathway for accumulating guanine crystals that, together, confer a white phenotype. These analyses uncover an important role for positional information in specifying ornamentation in zebrafish and show how tissue environmental cues and a novel gene regulatory program have allowed terminal addition of a distinct phenotype to a pre-existing cell type. SignificanceFish often have striking color patterns with important functions in behavior. In zebrafish, the familiar striped pattern forms through self-organizing interactions between pigment cells, yet the white highlights on their fins arise differently--through the transformation of black pigment cells into white ones. This study reveals how this dramatic cell transformation happens: signals from the surrounding tissue, specifically BMP and Agouti proteins, instruct black cells to change their fate. These signals trigger expression of specific genes that cause the cells to break down their black pigment while acquiring white, crystal-like structures. This work shows how local signals in tissues can drive the development of ornamental features and provides insights into how new cell types evolve.

developmental biology↗

bioRxiv2024

PTBP1 is upregulated by Zika virus infection via HIF-1alpha signal and hijacks NS1 protein to induce NS1 degradation to restrain viral replication

Zika virus (ZIKV), belonging to the Flaviviridae family, has been a severe threat to human health since the worldwide outbreak. ZIKV is capable of inducing fetal microcephaly, Guillain-Barre syndrome, and other serious neurological complications. Polypyrimidine tract-binding protein 1 (PTBP1) is a key member of the heterogeneous nuclear ribonucleoproteins (hnRNPs) family, functioning in selective mRNA splicing and gene expression regulation. Our previous study has indicated that the expression of PTBP1 increases in astrocytes upon ZIKV infection, yet the precise regulatory mechanisms underlying its role in viral replication remain elusive. In this study, we elucidated the specific pathway by which ZIKV upregulates PTBP1 expression through the activation of Hypoxia-inducible factor-1 (HIF-1) expression. Further investigation revealed that overexpression of PTBP1 effectively inhibits viral replication, whereas knockdown of PTBP1 significantly enhances viral replication. Mechanistically, using co-immunoprecipitation assays for protein interaction screening, we identified an interaction between PTBP1 and ZIKV non-structural protein NS1. Detailed studies demonstrated that PTBP1 bound and colocalized with NS1 to lead to the degradation of NS1 protein via a lysosomal pathway. Collectively, our findings unveil a novel mechanism underlying that ZIKV infection induces the expression of PTBP1 via the HIF-1 pathway, subsequently the accumulated PTBP1 binds to ZIKV NS1 protein to promote NS1 degradation, thereby effectively inhibiting viral replication. The study illustrates a distinct restricted cellular factor that regulates ZIKV replication, which provides a potential target for the control of the viral replication and pathogenesis during the ZIKV epidemic. ImportanceSince the outbreak of ZIKV infection among human in 2014, a Zika epidemic has caused Zika fever accompanied with fetal microcephaly, Guillain-Barre syndrome, and other neurological symptoms. Emerging evidence reveals that ZIKV infects astrocytes to specially induce the expression of polypyrimidine tract-binding protein 1 (PTBP1), one of hnRNPs members. However, the interplay between PTBP1 and ZIKV replication is highly concerned. Here, we uncover a distinct manner that ZIKV infection induces PTBP1 expression through the activation of hypoxia-inducible factor-1 (HIF-1) signal. Additionally, activation of HIF-1 signal hinders ZIKV replication relying on PTBP1 accumulation. Further investigations suggest that PTBP1 restrains ZIKV replication by interacting with ZIKV NS1 protein, thereby leading to the degradation of NS1 protein via a lysosomal pathway. Collectively, our findings illustrate a novel restricted cellular factor PTBP1 mediated by HIF-1 that regulates ZIKV replication, which provides a potential therapeutic target of the viral replication and pathogenesis against ZIKV pandemic.

microbiology↗

bioRxiv2024

Targeting SLC7A11-mediated cysteine metabolism for the treatment of trastuzumab resistant HER2 positive breast cancer

Trastuzumab resistance remains a challenge for HER2 positive breast cancer treatment. Targeting metabolic reprogramming would provide novel insights for therapeutic strategies. Here, we integrated metabolomics, transcriptomics and epigenomics data of trastuzumab sensitive and primary resistant HER2 positive breast cancer to identify metabolic alterations. Aberrant cysteine metabolism was discovered in trastuzumab primary resistant breast cancer at both circulating and intracellular levels. The inhibition of SLC7A11 and cysteine starvation could synergize with trastuzumab to induce ferroptosis. Mechanistically, increased H3K4me3 and decreased DNA methylation enhanced SLC7A11 transcription and cystine uptake in trastuzumab resistant breast cancer. The regulation of epigenetic modifications modulated cysteine metabolism and ferroptosis sensitivity. These results revealed an innovative approach for overcoming trastuzumab resistance by targeting specific amino acid metabolism.

cancer biology↗

bioRxiv2024

Brain Aging Among Individuals with Classical Trigeminal Neuralgia

Trigeminal neuralgia (TN) is a complex orofacial neuropathic pain condition with limited understanding of underlying mechanisms and therapeutic options. Emerging evidence suggests the involvement of the brain in persons with TN including widespread brain changes when employing a widely used brain aging biomarker that estimates a predicted brain age difference or brain age gap. The aim of the present cross-sectional study was to assess the predicted brain age difference (brain-PAD) or brain age gap across two discrete TN subtypes (classical TN, and secondary/idiopathic TN) in comparison with age-and sex-matched pain-free controls and its association with several clinical and psychological characteristics. Thirty-four individuals diagnosed with Classical TN, 17 diagnosed with secondary/idiopathic TN were age- and sex-matched to pain-free controls (n=54). All participants underwent a T1 brain MRI and completed clinical and psychological measures. There were significant differences in brain-PAD among TN subtypes (ANCOVA p = 0.0078, effect size f2 = 0.282), with individuals diagnosed with Classical TN having a brain-PAD significantly greater than the controls by 3.87 years (p = 0.01, Bonferroni-corrected). There were no significant brain-PAD differences between secondary/idiopathic TN and pain-free controls. Brain-PAD had a significant positive association with both pain catastrophizing (p = 0.032) and pain-related anxiety (p = 0.041), but no significant association with disease duration (p = 0.519) or usual pain intensity (p = 0.443). We report here accelerated brain aging processes in patients with classical TN, but not in persons diagnosed with secondary/idiopathic TN. Our study replicates previous findings and adds to the literature that accelerated brain aging may not occur across all TN subtypes. Given the increased use of MRI for TN diagnostics, combined with our own recent work deriving our brain aging biomarker from clinical-grade scans, future studies within clinical settings are feasible and needed to understand this debilitating condition.

neuroscience↗

bioRxiv2024

α-Synuclein Strain Dynamics Correlate with Cognitive Shifts in Parkinson's Disease

-Synuclein (-syn) strains can serve as discriminators between Parkinsons disease (PD) and related -synucleinopathies. The relationship between -syn strain dynamics and clinical performance as patients transition from normal cognition (NC) to cognitive impairment (CI) is not known. Here, we show that the biophysical properties and neurotoxicity of -syn strains change as PD cognitive status transitions from NC to mild cognitive impairment (PD-MCI) and dementia (PD-D). Both cross-sectional and longitudinal analyses reveal distinct -syn strains in PD patients correlating to their level of cognitive impairment. Machine learning (ML) was employed to achieve high classification accuracy. The combination of thioflavin T (ThT) maximal fluorescence intensity (mfi), max slope of rise curve (forming rate), lag time (tlag), 20% time (t20), and half-time (t50), dynamic light scattering (DLS) (peak number, [1/2] peak size, [1/2] peak intensity) and neurotoxicity together with demographic variables for model training yielded superior performance (89[~]99% accuracy in the 4- and 2- classification schema) compared to individual features alone in classifying cognitive status. For the longitudinal study, DLS peak number emerged as the strongest predictor of cognitive transition (HR = 0.12, P = 0.002), with the optimal predictive model combining DLS peak number, sex, education, DLS peak 1 size, and DLS peak 2 polydispersity achieving high accuracy (C-index of [~]93%). This study presents evidence that individuals with PD have different -syn strains correlating to their cognitive status and highlights the potential of -syn strain dynamics to guide future diagnosis, management, and stratification of PD patients. One Sentence SummaryDistinct features of -syn strains change with cognitive decline in Parkinsons disease and AI-based analysis incorporating these combined characteristics serves as a powerful tool for PD clinical stratification.

neuroscience↗

bioRxiv2024

RIG-I and MDA5 cooperatively recognize the DENV replicative-form dsRNA to activate innate immunity

RIG-I like receptors (RLRs) are a family of cytosolic RNA sensors that sense RNA virus infection to activate innate immune response. It is generally believed that different RNA viruses are recognized by either RIG-I or MDA5, two important RLR members, depending on the nature of pathogen-associated molecular patterns (PAMPs) that are generated by RNA virus replication. Dengue virus (DENV) is an important RNA virus causing serious human diseases. Despite extensive investigations, the molecular basis of the DENV PAMP recognized by the host RLR has been poorly defined, and which RLR is involved in sensing the DENV PAMP remains controversial. Here, we demonstrated that the DENV infection-induced interferon response is dependent upon both RIG-I and MDA5, with RIG-I playing a predominant role. Next we purified the DENV PAMP RNA from the DENV-infected cells, and demonstrated that the purified DENV PAMP is viral full-length double-stranded RNA bearing 5ppp modifications, likely representing the viral replicative-form RNA. Finally, we confirmed the nature of the DENV PAMP by reconstituting the viral replicative-form RNA from in vitro synthesized DENV genomic RNA. In conclusion, our work not only defined the molecular basis of the RLR-PAMP interaction during DENV infection, but also revealed the previously underappreciated recognition of the distinct moiety of same PAMP by different RLRs in innate immunity against RNA viruses. ImportanceThe molecular interaction between PAMPs and RLRs plays a crucial role in innate immune response against the RNA virus infection. To our knowledge, the exact molecular basis of the DENV PAMPs and which RLR member (RIG-I or MDA5) is involved in this recognition remain controversial. In this study, we demonstrated that the DENV PAMP is likely DENV replicative-form RNA, a double-stranded RNA. RIG-I and MDA5 can sense different moieties of this DENV PAMP to active innate immune response. Our work not only clarified which RLR and what viral PAMP are involved in innate immune sensing of DENV infection, but also revealed previously underappreciated recognition of the same PAMPs by different RLRs in innate immunity against RNA viruses.

microbiology↗

bioRxiv2024

Induction of the ISR by AB5 subtilase cytotoxin drives IFN-I expression in pDCs via STING activation

We demonstrate that exposure to the AB5 subtilase cytotoxin (SubAB) induces the unfolded protein response (UPR) in human peripheral blood mononuclear cells, concomitant with a pro-inflammatory response across distinct cell subsets. Notably, SubAB selectively induces type-I interferon (IFN) expression in plasmacytoid dendritic cells, acting synergistically with Toll-like receptor 7 stimulation. The induction of type-I IFN in response to SubAB relies on stimulator of interferon genes (STING) activation, coupled with protein synthesis inhibition mediated by protein kinase R-like endoplasmic reticulum kinase and phosphorylation of the eukaryotic translation initiation factor 2 subunit-alpha. By impeding mRNA translation through the integrated stress response, SubAB precipitates the downregulation of the negative innate signaling feedback regulator Tax1-binding protein 1. This downregulation is necessary to unleash TANK-binding kinase 1 signaling associated with STING activation. These findings shed new light on how UPR-inducing conditions may regulate the immune system during infection or pathogenesis.

immunology↗

bioRxiv2024

Cryo-EM of native membranes reveals an intimate connection between the Krebs cycle and respiration in mycobacteria

Imaging of endogenous protein complexes in their native membranes can reveal protein-protein interactions that are lost upon detergent solubilization. To investigate interactions in the mycobacterial oxidative phosphorylation machinery, we prepared inverted membrane vesicles from Mycobacterium smegmatis and enriched for vesicles containing complexes of interest by affinity chromatography. Electron cryomicroscopy (cryo-EM) of these vesicles revealed that malate-quinone oxidoreductase (Mqo), an enzyme from the Krebs cycle, physically associates with the electron transport chain Complex III2IV2 (CIII2CIV2) supercomplex. Analysis of the Mqo:CIII2CIV2 interaction shows that CIII2CIV2 is necessary for malate-driven, but not NADH- driven, electron transport chain activity and oxygen consumption. Further, the association of Mqo with CIII2CIV2 enables electron transfer from malate to CIII2CIV2 with millisecond kinetics. Together, these findings indicate a connection between the Krebs cycle and respiration that directs electrons along a single branch of the mycobacterial electron transport chain.

biochemistry↗