Biology subjects

Xiang, Y.

Publications and source records attributed to Xiang, Y..

At least 37 records · Page 2Linked to original sources

bioRxiv2026

Human hindbrain organoids with segment-specific 5-HT neurons for motor modulation

The serotonergic system regulates human mood, reward, and motor control, and its impairment contributes to debilitating psychiatric disorders. Serotonergic neurons (SNs) arise predominantly in the hindbrain and acquire segment-specific identities and functions; however, the lack of human models remains a challenge to understanding the human serotonergic system. Here, we generate human serotonergic-enriched rostral and caudal hindbrain organoids (hsrHOs and hscHOs) that produce segment-specific SNs with regional identities corresponding to rhombomeres r2-r3 and r5-r8, respectively. hsrHOs and hscHOs produce SNs that recapitulate their in vivo counterparts in transcriptomic profiles, function, and ascending or descending projection preferences. Assembly with human neuromusculoskeletal organoids enables modeling of serotonergic modulation of motor control. This system further reveals that deficiency of the schizophrenia risk gene DISC1 disrupts human serotonergic development and impairs motor modulation. Together, our study establishes a human organoid platform for modeling development, circuit function and disease-associated dysfunction of the serotonergic modulatory system.

neuroscience↗

bioRxiv2026

Recovery of proofreading-impaired SARS-CoV-2 reveals a mutator phenotype and an ExoN activity threshold for viability

Coronaviruses (CoVs) replicate unusually large RNA genomes that necessitate proofreading by the 3'-to-5' exoribonuclease (ExoN) formed by nonstructural proteins 14 (nsp14) and 10 (nsp10). Previous studies suggested that inactivation of the ExoN catalytic site in severe acute respiratory syndrome CoV 2 (SARS-CoV-2) is lethal, leaving unresolved whether the virus can tolerate impaired proofreading activity. Here, we investigated the functional requirement for ExoN in SARS-CoV-2 replication by combining a continuous fluorescence-based biochemical assay with an optimized single-bacmid reverse genetics system. Mutational analysis of residues involved in RNA binding or catalysis revealed graded effects on ExoN activity in vitro. Alanine substitution of Lys9, a residue positioned near the RNA-binding interface, did not reduce ExoN activity, whereas charge reversal at this position (K9E) impaired activity more strongly than alanine substitutions of the catalytic motif I residues D90 and E92 (D90A/E92A). Correspondingly, recombinant SARS-CoV-2 carrying K9A was readily recovered, whereas the D90A/E92A mutant was recovered only after an extended delay and K9E could not be rescued despite repeated attempts. The D90A/E92A mutant exhibited reduced replication while maintaining the engineered ExoN substitutions during serial passage. Deep sequencing of viral populations revealed a marked increase in genome-wide sequence variation in the D90A/E92A mutant, demonstrating a stable mutator phenotype. Together, these findings indicate that SARS-CoV-2 can tolerate substantial impairment of ExoN activity but depends on a minimal activity threshold for viability. This system provides a platform for defining how SARS-CoV-2 proofreading controls genome stability, viral fitness, and sensitivity to antiviral strategies that exploit reduced replication fidelity. ImportanceCoronaviruses have unusually large RNA genomes because they encode a proofreading enzyme that removes copying errors during replication. It has been unclear whether SARS-CoV-2 can survive when this proofreading function is strongly weakened, because earlier studies suggested that loss of the enzymes catalytic activity is lethal. We show that SARS-CoV-2 can tolerate substantial impairment of proofreading, but only when residual exonuclease activity remains above a minimal threshold. A virus with impaired proofreading replicates less efficiently and accumulates mutations across its genome, whereas a more severe defect prevents virus recovery. These findings clarify how coronavirus proofreading balances genome stability with viral fitness and provide a useful system for studying how reduced replication fidelity affects viral evolution, antiviral sensitivity, and attenuation. Defining this activity threshold may also help guide antiviral strategies that target coronavirus proofreading.

microbiology↗

bioRxiv2026

Multispecific nanobody degraders co-deplete membrane receptors and enable targeted delivery of diverse payloads

Targeting membrane receptors underlies the success of antibody-drug conjugates (ADCs), yet single-receptor formats can be limited by heterogeneous expression, compensatory signaling, and variable internalization. Here we developed Multivalent Interchangeable Nanobody Degradation System (MINDS), a modular nanobody-Fc chassis that co-engages multiple membrane receptors, promotes their lysosomal co-depletion, and enables delivery of diverse intracellular payloads. As a proof of concept, we generated Tritazumab, a trispecific nanobody-Fc targeting three oncogenic receptors EGFR, cMET, and TfR1. Tritazumab incorporates a high-affinity, non-transferrin-competing anti-TfR1 nanobody that drives efficient uptake and lysosomal trafficking, enabling coordinated depletion of all three receptors. Across non-small cell lung cancer models, Tritazumab achieved rapid and sustained multi-receptor surface loss with picomolar degradation potency, reaching near-maximal depletion within approximately 1.5 hours. Conjugation of Tritazumab to MMAE preserved receptor binding and produced substantially greater antiproliferative activity and improved tumor selectivity relative to clinical ADCs in matched cell models, along with potent in vivo tumor growth inhibition and acceptable tolerability in a xenograft model. Extending the platform beyond cytotoxic payloads, a BRD4 molecular glue conjugate improved the selectivity window by > 100-fold and showed marked in vivo efficacy, while an EZH2-targeting PROTAC conjugate achieved an approximately 1,000-fold increase in intracellular degradation potency relative to the free PROTAC. These findings establish MINDS as a modular multispecific degrader-payload platform that integrates receptor co-depletion to enhance anticancer selectivity and efficacy.

cancer biology↗

bioRxiv2026

Septin-mediated coupling of protein import and division during chloroplast evolution

Chloroplast biogenesis depends on both protein import and organelle division, yet how their coordination emerged during evolution remains unclear. Here, we show that the single septin SEP1 links these pathways in the green alga Chlamydomonas reinhardtii. SEP1 forms a filamentous network on the chloroplast envelope during interphase and reorganizes into a ring at the chloroplast division site during cytokinesis. Loss of SEP1 selectively impairs import of chloroplast-division proteins and causes mispositioning of the division ring, without impairing bulk chloroplast protein import. SEP1 physically associates with outer-envelope TOC GTPases through evolutionarily related GTPase domains. Phylogenetic analysis places TOC GTPases within an algal septin-derived clade, and heterologous expression of SEP1 in land plants, in which septins are absent, shows conservation of its chloroplast targeting and TOC binding. Together, these findings identify septins as coordinators of plastid protein import and division and suggest that this coupling emerged early in chloroplast evolution.

cell biology↗

bioRxiv2026

ChiMER: Integrating chromatin architecture into splicing graphs for chimeric enhancer RNAs detection

MotivationEnhancer-derived RNAs (eRNAs) and their fusion with protein-coding genes represent a crucial yet understudied layer of transcriptional regulation. eRNAs are typically expressed at low levels, which makes fusion events difficult to detect with conventional fusion detection tools. In addition, these tools are not designed to capture fusion transcripts arising from spatial proximity between distal regulatory elements and gene loci. Reads spanning such regions are also frequently filtered as mapping artifacts. As a result, computational approaches for systematically identifying spatially mediated enhancer-exon fusion transcripts remain lacking. MethodsWe developed ChiMER, a graph-based framework for detecting ChiMeric Enhancer RNAs from short-read RNA-seq data. ChiMER constructs splice graphs with chromatin contact information to introduce enhancer-exon edges and uses graph alignment to search for potential transcriptional paths. A ranking-based scoring module then prioritizes high-confidence events. Evaluations on simulated and real RNA-seq datasets show that ChiMER achieves higher sensitivity than conventional linear fusion detection methods while maintaining low false-positive rates. ResultsApplied to cancer cell line RNA-seq datasets, ChiMER identified multiple enhancer-exon chimeric transcripts, several associated with super-enhancer regions. Multi-omics analysis further shows that fusion transcripts occur in transcriptionally active regulatory environments and frequently coincide with strong R-loop signals, suggesting a potential role of RNA-DNA hybrid structures in facilitating long-range transcriptional joining events. Availabilityhttps://github.com/Candlelight-XYJ/ChiMER Contactyujia.xiang@outlook.com, xielinhai@ncpsb.org.cn

bioinformatics↗

bioRxiv2026

Prophylactic Lipoxin A4 Attenuates Clostridioides difficile Infection by Augmenting Epithelial Barrier and Resolving Inflammation

Clostridioides difficile infection (CDI) is a leading healthcare-associated diarrhea with high recurrence rates, partially due to antibiotic-induced dysbiosis and dysregulated host inflammation. Specialized pro-resolving mediators (SPMs), such as Lipoxin A4 (LXA4), offer promise in controlling excessive inflammation and promoting tissue repair, yet their role in CDI remains unexplored. Here, we developed a compact, gas-tight gut-on-a-chip (GOC) system that reconciles the anaerobic requirements of C. difficile with the oxic needs of human intestinal epithelium, enabling physiologically relevant co-culture within a standard incubator. A CDI in vitro model was established based on this GOC system. Using the model, we demonstrated that prophylactic administration of LXA4 significantly preserved epithelial barrier integrity, attenuated pro-inflammatory cytokine secretion (IL-8 and IFN-{gamma}), and reduced bacterial colonization. Transcriptomic analysis revealed that LXA4 pretreatment upregulated genes involved in cell junction organization while downregulated immune activation pathways. These protective effects were validated in a murine CDI model, where LXA4 pretreatment reduced weight loss, pathological damage, and fecal bacterial burden. Furthermore, prophylactic administration of LXA4 synergized with vancomycin treatment further enhanced antibiotic efficacy while allowing a 50% dose reduction without compromising therapeutic outcomes. Our study establishes a robust approach for CDI research and highlights the prophylactic and adjuvant potential of inflammation-resolving strategies, offering a novel approach to mitigate CDI incidence and improve treatment outcomes.

bioengineering↗

bioRxiv2026

Selective targeting of type II tRNAs underlies SLFN14-mediated translational repression and its dysregulation by thrombocytopenia-linked mutations

Schlafens (SLFNs) are interferon-inducible regulators of RNA metabolism and cell fate. SLFN14 is a ribosome-associated endoribonuclease whose pathogenic variants cause autosomal dominant inherited thrombocytopenia (IT), but the underlying disease mechanism has been unclear. We show that SLFN14 represses global protein synthesis through selective cleavage of type II tRNAs. IT-linked mutations alter RNA substrate specificity, enhancing degradation of type II tRNAs while reducing rRNA cleavage. This shift promotes ribosome stalling at codons decoded by type II tRNAs, triggering global translational arrest, stress signaling, and cell death. These findings define the molecular basis of SLFN14-associated thrombocytopenia and highlight selective tRNA targeting as a mechanism regulating translation and cell fate.

molecular biology↗

bioRxiv2026

Structural Mechanisms of SAMD9 Autoinhibition and Pathogenic Dysregulation

SAMD9 and SAMD9L (SAMD9/9L) are large cytosolic proteins essential for hematopoietic homeostasis and antiviral defense1-3. Germline gain-of-function (GoF) mutations in SAMD9/9L cause severe multisystem disorders and predisposition to leukemia, yet the mechanisms that regulate SAMD9/9L activity and how pathogenic mutations disrupt these processes, remain poorly understood. Here, we determine cryo-electron microscopy structures of human SAMD9 in multiple conformational and oligomeric states. We show that SAMD9 predominantly adopts a closed, autoinhibited conformation stabilized by a central ATP-bound nucleotide-binding oligomerization domain (NOD) and an extensive network of intramolecular interactions. Recurrent patient-derived GoF mutations localize to and destabilize these intramolecular interfaces, and restoring the disrupted interactions through compensatory mutations reinstates autoinhibition. We further identify low-abundance asymmetric SAMD9 dimers in which one protomer undergoes large conformational changes and establishes intermolecular interactions that are essential for SAMD9 activation. Together, these findings define the structural basis of SAMD9 autoinhibition and explain how human GoF mutations subvert this regulatory mechanism to drive disease.

biophysics↗

bioRxiv2025

Multivalent Nanobodies for Potent and Broad Neutralization of Staphylococcus aureus Toxins

Staphylococcus aureus is a leading cause of lethal bacteremia and pneumonia, which are driven by potent virulence factors such as T-cell superantigens and alpha hemolysin. S. aureus has among the highest rates of antibiotic resistance, yet no vaccines or alternative therapies are available despite decades of research. Here, we developed a repertoire of potent, high affinity nanobodies (Nbs) targeting key toxins in S. aureus infection, including superantigens (SAgs) SEB, SEC, TSST-1, and Hla. Comprehensive cryo-EM and AlphaFold3 analyses of these Nbs, which were elicited with clinical cocktail vaccines, revealed diverse neutralizing epitopes and mechanisms that provide strategic insights for immunotherapy and vaccine design. Guided by these findings, we engineered highly stable, multivalent, and multifunctional Nb constructs. These constructs included an aerosolizable trimeric Nb with enhanced neuralization activity against Hla and SEC, and an ultrapotent decameric Nb-IgG-Fc fusion construct against a wide range of major toxins in S. aureus sepsis (SEB, SEC, TSST-1, and Hla). These multifunctional Nbs demonstrated promising protective activity in murine models of pneumonia and sepsis, underscoring their potential as versatile immunotherapies that address the complex virulence profiles of S. aureus. Our work lays a foundation for precision immunotherapies beyond current treatment options to combat complex bacterial infections with multiple virulence mechanisms. Significance statementS. aureus is among the most common, antibiotic-resistant, and deadly causes of bacterial infections. We developed nanobodies against clinically significant virulence factors in S. aureus sepsis and pneumonia, including superantigens (SAgs) SEB, SEC, and TSST-1 as well as pore forming toxin Hla. These nanobodies displayed complete and potent neutralization of each toxin, exploiting a wide variety neutralizing mechanisms. Structural investigation of these diverse neutralizing nanobodies, which were elicited in llamas using clinically investigated cocktail vaccines, highlighted the importance of disrupting SAg interaction with TCR or MHCII and potential flaws in targeting poorly neutralizing conserved SAg epitopes using vaccine cocktails. Nb leads against each toxin were combined in different multivalent configurations, including an aerosolizable trimeric Nb and a half-life extended decameric Nb IgG Fc fusion construct. This work highlights multivalent nanobodies as a comprehensive yet therapeutically precise drug platform that addresses the complex virulence profiles of bacterial infectious diseases.

microbiology↗

bioRxiv2025

Plasma Ficolins Enable Liver Macrophages to Capture Blood-Borne Bacteria by Recognizing Capsular Polysaccharides

Ficolins are evolutionarily conserved glycan-binding lectins in plasma or on cell membranes of immune cells, yet their physiological functions remain to be defined. Here we demonstrate that plasma ficolins drives the capture of diverse encapsulated bacteria in the blood circulation by the liver resident macrophages (Kupffer cells). Ficolin-activated immunity in the liver sinusoids provides swift and sterilizing immunity in mice. Mice lacking ficolin-A (the only plasma ficolin) became hypersusceptible to the blood infections of the ficolin-A-recognizable bacterial serotypes. Mechanistically, plasma ficolins activate complement C3 on bacterial surfaces by pattern recognition of acetylated monosaccharides on polysaccharide capsules, and thereby deliver the opsonized bacteria to C3 receptors on Kupffer cells for phagocytic elimination. These findings reveal that plasma ficolins serve as pattern-recognition receptors that are essential for maintaining the bloodstream sterile.

microbiology↗

bioRxiv2025

Blood originates in hypoblasts during embryonic development

Blood is essential for oxygen supply throughout life. The emergence of blood in the human embryo remains poorly understood. Our study leverages multiple stem cell embryo models and advanced lineage barcoding to unveil that hypoblast, originally regarded as forming the yolk sac wall, is heterogeneous and contributes to CDX2+ extraembryonic mesoderm, followed by hemoglobin+ cells as the first blood cells. CDX2 marks the hypoblast-to-hemoglobin+ cell trajectory that functionally sustains oxygen levels in embryo models. These hemoglobin+ cells molecularly and functionally resemble phagocytes. We show that the erythro-core regulatory network is poised in hypoblasts, and its boost endows erythropoiesis to both hypoblasts and phagocytes. Hypoblasts are the origin of the first blood in humans and non-human primates, providing a conceptual framework that earlier blood generation than expected fills the gap in the establishment of circulation. Further, the hypoblast is a place where primates may repurpose the phagocyte program to carry oxygen throughout embryos. HighlightsO_LIBarcode-traced hypoblast fate in human embryo models; C_LIO_LIThe first blood comes from the hypoblast that contributes to hemoglobin+ phagocyte-like cells; C_LIO_LICDX2 marks hypoblast blood that sustains oxygen supply in embryos before heart formation; C_LIO_LIErythro-core regulatory network endows erythropoiesis to human hypoblasts and phagocytes. C_LI

developmental biology↗

bioRxiv2025

A functional map of CDK-drug interactions at single amino acid resolution

Proteins that drive or support human disease phenotypes are attractive molecular targets for precision therapy, yet most are nominated by knockout studies and then targeted with drugs that inhibit core catalytic pockets. These strategies cannot resolve which residues are essential, whether non-catalytic sites offer better selectivity or potency, or identify on-target resistance mechanisms. We introduce a framework that integrates precision genome editing, mechanistically diverse therapeutics, and computational sequence-structure-function analysis to map protein essentiality and potential druggability at single amino acid resolution. Applying this framework across 9 cyclin-dependent kinases (CDKs) and 15 cancer therapeutics--including ATP-competitive inhibitors, PROTACs, and molecular glue degraders--we identify shared and CDK-specific residues critical for cell fitness and drug response, including known resistance mutations and dozens of new variants. The resulting functional maps resolve residue- and mechanism-specific differences in the resistance spectra among agents targeting the same protein. We show that this iterative strategy can also uncover higher order interactions by performing intra- and extragenic epistasis screens to identify residues that mediate on-target and within-family cell fitness and drug resistance. Finally, we find evidence of novel CDK6 mutations in breast cancer patients and concordance between experimental and clinical correlates of response to CDK4/6 inhibitors. By mapping residue-level essentiality and forecasting therapy resistance mutations, target-drug interaction maps could inform clinical treatment and guide design of more selective therapeutic molecules.

cancer biology↗

bioRxiv2025

Absolute quantification of TCA cycle intermediates in mouse ocular tissues reveals distinct tissue- and sex-specific mitochondrial metabolism

ObjectiveMitochondrial tricarboxylic acid (TCA) cycle is central to energy production and redox balance in the eye, which must sustain high metabolic activity to support vision. Retinal neurons, the retinal pigment epithelium (RPE), cornea, and lens each have distinct physiological roles and metabolic demands, yet the absolute concentrations of key TCA intermediates and their variation by tissue, sex, and time of day are not well-defined. MethodsTargeted gas chromatography-mass spectrometry was employed to quantify the absolute concentrations of TCA cycle metabolites in mouse ocular tissues collected at 10 AM and 2 PM to capture diurnal variations. Key metabolite ratios were subsequently calculated to provide insight into TCA cycle dynamics across eye tissues. ResultsThe retina showed the highest concentrations of TCA metabolites among all ocular tissues, particularly succinate, citrate, and malate, consistent with its high energy demands. The RPE/choroid demonstrated well-balanced intermediates with the highest -ketoglutarate (-KG)/Isocitrate ratio, reflecting its efficient mitochondrial oxidation and reductive carboxylation. Corneal metabolism was featured by dominant malate, especially in females, suggesting a metabolic adaptation for redox regulation and oxidative stress defense. The lens had uniformly low metabolite levels except for succinate, indicating minimal mitochondrial activity under physiologically low oxygen conditions. Notably, both the cornea and lens showed significant sex-dependent and diurnal variations in TCA cycle intermediates. ConclusionThis study demonstrates distinct tissue-specific mitochondrial metabolism in the eye, reflecting the unique functional and biochemical demands of each tissue. These metabolic signatures may underlie their susceptibility to mitochondrial dysfunction in various ocular diseases.

biochemistry↗

bioRxiv2025

Gene Therapy Rescues Cone Function in an All-cone Retina Mouse Model for Blue Cone Monochromacy with the Most Common C203R Missense Mutation

Blue cone monochromacy (BCM) is an X-linked cone dystrophy characterized by loss of long- (L) and medium-wavelength (M) cone function. A common cause is the C203R missense mutation, which occurs in both OPN1LW and OPN1MW, or in hybrid OPN1LW/OPN1MW opsin genes. Because BCM primarily affects foveal cones, we generated Opn1mwC198R/Opn1sw-/-/Nrl-/- (C198RAC) mice carrying the murine equivalent of the human C203R mutation on an all-cone retinal background. C198RAC mice exhibited absent photopic ERG responses and significantly shortened cone outer segments, recapitulating foveal cone deficits in BCM. Metabolomic profiling further revealed altered retinal metabolism, including reduced cGMP and elevated oxidative stress-related metabolites. To evaluate therapy, we delivered AAV8-Y733F expressing human L-opsin (OPN1LW) cDNA under the cone-specific PR2.1 promoter at 1 and 5 months of age. Treatment restored cone function, regenerated outer segment structures, and provided rescue for at least 5 months post-injection in both early- and late-treatment groups. These results demonstrate that densely packed cones expressing only the C198R mutant opsin remain viable targets for gene therapy. Together, this study establishes the C198RAC mouse as a cone-rich model of BCM and provides compelling preclinical evidence that AAV-mediated gene augmentation can restore cone structure and function, supporting the feasibility of gene therapy for BCM.

molecular biology↗

bioRxiv2025

One Thousand SARS-CoV-2 Antibody Structures Reveal Convergent Binding and Near-Universal Immune Escape

Since the emergence of SARS-CoV-2, understanding how antibodies recognize and adapt to viral evolution has been central to vaccine and therapeutic developments. To date, over 1,100 SARS-CoV-2 antibody structures--16% of all known antibody-antigen complexes--have been resolved, marking the largest structural biology effort towards a single pathogen. Here, we present a comprehensive analysis of this landmark dataset to investigate the principles of antibody recognition and immune escape. Human immunoglobulins (IgGs) and camelid single-chain antibodies dominate the dataset, collectively mapping 99% of the receptor-binding domain surface. Despite remarkable sequence and conformational diversity, antibodies exhibit striking convergence in their paratope structures, revealing evolutionary constraints in epitope selection. Structural and functional analyses reveal near-universal immune escape of antibodies, including all clinical monoclonals, by advanced variants such as KP3.1.1. On average, over one-third of antibody epitope residues are mutated. These findings support pervasive immune escape, underscoring the need to effectively leverage multi-epitope targeting strategies to achieve durable immunity.

microbiology↗

bioRxiv2025

Programmed meiotic errors facilitate dichotomous sperm production in the silkworm, Bombyx mori

The goal of meiosis is typically to produce haploid gametes (eggs or sperm). Failure to do so is catastrophic for fertility and offspring health. However, Lepidopteran (moths and butterflies) males produce two morphs of sperm: nucleated (eupyrene) sperm which fertilize the egg, and anucleated (apyrene) sperm, both of which are essential for fertilization. The meiotic differences in the two types of spermatogenesis have not been well characterized, and our knowledge of the molecular differences between eupyrene and apyrene spermatogenesis are extremely limited in all systems. The only factor identified as being required for apyrene spermatogenesis is Sex-lethal (Sxl). Here, we show through cytological analysis of early meiotic events that there are several key differences in the genesis of apyrene sperm and eupyrene sperm. Specifically, apyrene spermatocytes fail to condense and pair their chromosomes during meiotic prophase I. In addition, telomeres do not attach to the nuclear envelope. Due to these differences, full-length synaptonemal complex does not form. RNA sequencing of both eupyrene- and apyrene-producing testes revealed distinct changes in transcriptional programs, including down-regulation of a myriad of meiotic genes and cell cycle checkpoint factors during apyrene meiosis. By comparing wild-type and Sxl-knockout apyrene testes, we found that Sxl is not required for the changes in the expression of the meiotic genes but instead plays a role in checkpoint inactivation to allow this error-prone meiosis to proceed. Together, our findings reveal significant insights into two converging molecular pathways that promote the formation of dimorphic sperm in Lepidoptera.

genetics↗

bioRxiv2025

Salicylic Acid Engages Central Metabolic Regulators SnRK1 and TOR to Govern Immunity by Differential Phosphorylation of NPR1

Immunity is a delicate balance between combating infection and preserving the metabolic functions vital for host survival. However, the mechanisms by which immune responses are coordinated with cellular metabolism remain largely unknown. Here, we show that NONEXPRESSER OF PR GENES 1 (NPR1), the central plant immune regulator of salicylic acid (SA)-mediated defense responses, is controlled by a cascade of posttranslational modifications (PTMs) involving two master nutrient-sensing kinases. Under normal growth conditions, TARGET OF RAPAMYCIN (TOR) inhibits NPR1 through phosphorylation at Ser-55/59. During defense responses, elevated SA enhances SNF1-RELATED KINASE 1 (SnRK1) activity, which in turn inhibits TOR signaling and phosphorylates NPR1 at Ser-557. This phosphorylation event activates NPR1 and facilitates its subsequent PTMs. Together, our results reveal an integral role of SA (the active metabolite of aspirin) in controlling central metabolic regulators SnRK1 and TOR to coordinate immune responses and growth through antagonistic modifications of NPR1.

plant biology↗

bioRxiv2025

Divergent MIC of Clarithromycin and Azithromycin Against Clinical Isolates of Mycobacterium abscessus Complex

Current treatment guidelines for Mycobacterium abscessus complex (MAB) infections recommend macrolides (clarithromycin/CAM and azithromycin/AZM) as cornerstone therapies, considering them clinically interchangeable without distinction. This study evaluated the comparative in vitro activity of clarithromycin (CAM) and azithromycin (AZM) against 146 clinical isolates of Mycobacterium abscessus complex organisms. MIC distributions revealed significantly higher resistance to AZM (94.5% resistant at [≥]8 g/mL) compared to CAM (77.4% resistant at [≥]8 g/mL), with only 4.8% of isolates susceptible to both drugs. Notably, 26 strains (17.8% of total) showed AZM resistance despite being non-resistant to CAM (MIC <8 g/mL) among 146 clinical isolates. Among the 33 CAM-non-resistant isolates (including susceptible and intermediate strains), 78.8% (26/33) were AZM-resistant, demonstrating frequent discordance in susceptibility profiles. These findings contrast with current treatment guidelines that recommend using CAM and AZM interchangeably without distinction. Subspecies analysis showed three distinct susceptibility profiles: isolates susceptible to both antibiotics (n=3, M. massiliense), isolates resistant to both antibiotics (n=3, M. massiliense), and M. bolletii with CAM-susceptible/AZM-resistant phenotypes (n=2). This differential resistance pattern suggests that while both drugs face substantial resistance challenges, CAM retains meaningful activity against certain strains that are AZM-resistant-particularly in M. bolletii. These findings indicate that AZM and CAM should not be used interchangeably to treat MAB infections and emphasize the need to prioritize CAM over AZM in treatment regimens.

microbiology↗