Biology subjects

Geddes-McAlister, J.

Publications and source records attributed to Geddes-McAlister, J..

At least 19 recordsLinked to original sources

bioRxiv2026

Mapping virulence-associated protein interaction networks reveals regulators of thermotolerance in Cryptococcus neoformans

Protein-protein interactions (PPIs) influence critical biological processes in pathogenic microorganisms, such as the human fungal pathogen, Cryptococcus neoformans. Fungal thermotolerance and stress response pathways are key virulence determinants that directly impact pathogen adaptation and survival and the infection process. To establish a comprehensive baseline of PPIs in C. neoformans and explore these interactions to infer functional roles for uncharacterized proteins, we applied size exclusion chromatography coupled with mass spectrometry to the secreted and cellular proteomes of the fungi. As a result, 216 and 1699 unique proteins were identified across 24 secretome and proteome fractions, respectively. The predicted secretome networks included expected proteins associated with vesicles and virulence, indicating a role in extracellular defense. Whereas the cryptococcal proteome highlighted interactions among proteins with defined roles in fungal virulence for protein stability and thermotolerance, including two previously uncharacterized proteins, CNAG_00287 and CNAG_05199, putatively involved in complex formation with heat-shock proteins (HSP). Based on sequence and structure homology, we propose that CNAG_00287 is a tetratricopeptide repeat-containing co-chaperone that modulates Hsp 70 activity and CNAG_05199 functions as a Hsp70. We validated the thermotolerance role of CNAG_00287 in heat-related stress, as its absence significantly impaired fungal growth in nutrient-limited media at 37 {degrees}C. Together, this work resolves virulence-associated PPIs within C. neoformans and reveals new molecular regulators of thermotolerance that underpin fungal pathogenicity.

microbiology↗

bioRxiv2026

Adaptive Focused Acoustics-integrated proteome profiling of macrophages uncovers low abundant proteins associated with immune homeostasis, inflammatory response, and transport

Efficient and reproducible protein extraction is a critical step in mass spectrometry-based proteomics workflows, particularly for complex host-pathogen systems where low-abundance immune-associated proteins are difficult to detect. Probe sonication methods used for cell lysis requiring mitigation of excessive heat generation, to prevent degradation of biologically important proteins, while also limiting throughput and potentially introducing sample-to-sample variability. In this study, we evaluated adaptive focused acoustics (AFA) technology as an alternative approach for macrophage lysis and protein extraction and digestion within a standard proteomics workflow coupled with mass spectrometry. We observed that AFA technology reduced hands-on processing times and overall workflow timelines and single-sample AFA technology improves proteome coverage, dynamic range, and reproducibility. We also evaluated multiplexed AFA technology for lysis, and we observed an exclusive macrophage proteome and influence on replicate reproducibility and dynamic range detection for low abundant proteins. Moreover, multiplexed AFA technology for macrophage lysis and digestion further increased protein identifications, replicate reproducibility, and dynamic range. Considering the AFA-exclusive proteome, 86 proteins were detected across all AFA-based lysis and digestion methods, including low-abundance proteins associated with macrophage homeostasis, inflammatory response, and transport. Together, these findings demonstrate that AFA technology enhances reproducibility, throughput, and proteome depth for macrophage protein extraction while enabling the detection of biologically relevant low-abundance immune-associated proteins. These improvements provide a strong foundation for future investigation of host-pathogen infection models, where pathogen-derived proteins remain challenging to detect within complex host proteomes.

immunology↗

bioRxiv2026

SbmA coordinates iron homeostasis and antimicrobial susceptibility in Klebsiella pneumoniae through phosphorylation-dependent regulation

Iron is an essential nutrient that underpins fundamental biological processes, yet its bioavailability is severely restricted during infection due to oxidation and host-mediated sequestration. In Gram-negative pathogens, such as Klebsiella pneumoniae, iron limitation imposes a critical selective pressure, necessitating tightly regulated acquisition systems to support growth, virulence, and survival. While canonical pathways for iron uptake are well characterized, regulatory mechanisms coordinating these processes remain incompletely understood. Here, we applied mass spectrometry-based phosphoproteomics to identify iron-responsive regulatory events associated with bacterial iron homeostasis. This approach revealed iron-dependent phosphorylation of SbmA, a conserved inner membrane transporter previously implicated in the uptake of antimicrobial peptides and related substrates. Functional characterization demonstrated that deletion of sbmA results in reduced intracellular iron levels and altered cellular morphology, supporting a role in iron acquisition. Complementary proteome mapping of {Delta}sbmA revealed compensatory production of siderophore receptors and TonB-dependent transport systems, further implicating SbmA in maintaining iron balance. Leveraging these findings, integration with high-throughput drug screening identified a compound that exploits SbmA-mediated transport to inhibit bacterial growth, highlighting its potential as a therapeutic entry point. Collectively, this work uncovers a previously unrecognized role for SbmA in iron homeostasis and demonstrates the power of phosphoproteomics to identify condition-specific regulators of essential bacterial pathways. These findings position SbmA as a promising target for antimicrobial development in K. pneumoniae.

microbiology↗

bioRxiv2026

Iron-responsive phosphorylation of TolQ modulates cell envelope integrity and antibiotic susceptibility in Klebsiella pneumoniae

Klebsiella pneumoniae is an opportunistic bacterial pathogen associated with high morbidity and mortality, exacerbated by the rapid emergence of resistance to last-resort antibiotics, such as carbapenems. Adaptation to nutrient limitation, particularly fluctuations in metal availability, is critical for bacterial survival and virulence, yet the regulatory mechanisms coordinating these responses remain incompletely understood. Protein phosphorylation represents a key post-translational modification governing bacterial physiology and offers a promising avenue for identifying novel antimicrobial targets. Here, we applied mass spectrometry-based phosphoproteomics to define nutrient-responsive signaling networks in K. pneumoniae under varying iron and zinc conditions. This analysis identified iron-dependent phosphorylation of TolQ, a conserved inner membrane component of the Tol-Pal system that maintains cell envelope integrity. Structural modeling predicted that phosphorylation modulates TolQ-TolR conformation, suggesting a mechanism by which iron availability regulates Tol-Pal function. Functional characterization demonstrated that deletion of tolQ results in reduced bacterial viability, increased susceptibility to host immune clearance, and heightened sensitivity to antibiotic treatment. To further explore the therapeutic potential of this pathway, we integrated high-throughput compound screening with computational modeling and identified small molecules that phenocopy {Delta}tolQ. Collectively, these findings reveal a previously unrecognized link between iron availability and phosphoregulation of the Tol-Pal system and establish TolQ as a critical mediator of bacterial survival. This work highlights phosphoproteomics as a powerful strategy to uncover regulatory vulnerabilities and identify targets for antimicrobial development in drug-resistant pathogens.

microbiology↗

bioRxiv2026

Recently emerged Fusarium chemotypes reprogram wheat defence and detoxification networks during Fusarium head blight development

Fusarium head blight (FHB) is a major threat to global wheat production and food safety due to contamination with mycotoxins, such as deoxynivalenol (DON). The emergence of new mycotoxin chemotypes, including 7--hydroxy,15-deacetylcalonectrin (3ANX), presents an evolving challenge for disease management and resistance breeding. Here, we performed a field-based, systems-level proteome analysis of wheat infected with Fusarium graminearum strains belonging to the common 15ADON and recently emerged 15ADON/3ANX chemotypes. Across host and pathogen, we quantified more than 9,200 proteins, providing extensive coverage of infection-associated molecular responses. Infection with 15ADON/3ANX strains suppressed canonical wheat detoxification pathways while promoting structural and oxidative defence responses. Concurrently, the fungal proteome of 15ADON/3ANX-producing strains indicated altered mitochondrial ribosome function and alternative virulence strategies. Further investigation of the host-pathogen interface defined hub protein networks negatively regulating classical detoxification markers, suggesting coordinated regulation of host defence responses regardless of chemotype. Molecular responses were linked to field phenotypes by quantification of DON-3-glucoside/DON ratios and disease severity, defining positive correlations in 15ADON infections, which were abolished upon 15ADON/3ANX infection, indicating chemotype-specific evasion or suppression of host defenses. These findings demonstrate reprogramming of host-pathogen interaction networks and reveal molecular targets that may inform chemotype-aware breeding strategies to enhance crop resilience.

systems biology↗

bioRxiv2026

A structure-guided pipeline yields peptide inhibitors that disarm fungal peptidase-driven virulence and resistance

Fungal infections are a major global health challenge, with current antifungal therapies limited by toxicity, cost, and resistance. For Cryptococcus neoformans, key virulence factors that initiate and sustain infection are regulated by fungal peptidases to produce a polysaccharide capsule, promote immune evasion, and support antifungal resistance. These peptidases represent promising targets for antivirulent therapeutic strategies. Here, we developed a computational pipeline to predict and design peptide- and protein-based inhibitors against cryptococcal peptidases. Specifically, we targeted three virulence-associated peptidases: Rim13 (cysteine), May1 (aspartic), and CnMpr1 (metallo). Cysteine peptidase inhibition decreased capsule/cell size ratios without impeding fungal growth and reduced fungal survival within macrophages. Similarly, aspartic peptidase inhibition enhanced fungal clearance within alveolar macrophages and disrupted biofilm formation with additive effects towards fluconazole susceptibility in resistant strains. Additionally, metallopeptidase inhibition through catalytic zinc chelation and blocked substrate binding led to enhanced enzymatic inhibition and reduced in vitro blood-brain barrier crossing. Moreover, an in vivo larval model assessing inhibitor efficacy produced additive effects with fluconazole and lacked host cell cytotoxicity and fungicidal properties, reinforcing anti-virulence mechanisms and therapeutic potential while limiting the evolution of resistance. Further, global proteome profiling of inhibitor treated cells defined a mechanism of cell wall disruption, impeding fungal virulence. Taken together, the designed peptidase inhibitors exhibited potent antifungal activity without harming mammalian cells, establishing a predictive framework for rational scaffold design of next-generation antifungals that disarm the pathogen enabling immune-mediated clearance.

microbiology↗

bioRxiv2026

A fungal effector targets the chloroplast to support biotrophy by balancing disease and plant health

Fungal pathogens are responsible for substantial crop losses worldwide. There is a pressing need to develop crops with improved disease resistance, especially given that climate change and human activities are exacerbating crop diseases. Our understanding of the molecular mechanisms by which fungi cause disease is incomplete. To address this limitation, we employed proteomics to identify candidate effector proteins from the pathogenic fungus Ustilago maydis that co-purified with the chloroplasts of maize host plants during infection. We specifically characterized the role of one putative chloroplast-associated effector, UmPce3, using heterologous expression in the non-host plant Arabidopsis thaliana. We discovered that UmPce3 interacts with the chloroplast DEAD-box RNA helicase, AtRH3. Phenotypes associated with the expression of UmPce3 in Arabidopsis mirrored those of plants with impaired AtRH3 function and included interference with chloroplast assembly, an impact on photosynthesis, and altered resistance to biotic and abiotic stresses. Support for RH3 as a bona fide effector target was obtained by identifying parallel phenotypic influences of UmPce3 in maize and by demonstrating an interaction between UmPce3 and maize ZmRH3b, an ortholog of AtRh3. Notably, UmPce3 contributes to biotrophy by promoting the virulence of U. maydis on maize seedlings and dampening virulence in plants challenged with salinity as an abiotic stress. Overall, this work highlights the chloroplast as a target of fungal pathogenesis and identifies RH3 as a potential hub for pathogen manipulation of organelle function to balance fungal proliferation and host health in support of biotrophy. Short summaryThe chloroplast plays a key role in plant immunity, in addition to its central contributions to photosynthesis, metabolism, and tolerance of abiotic stresses. The effector UmPce3 of the maize pathogen Ustilago maydis targets the DEAD-box RNA helicase RH3 in host plants to manipulate chloroplast function and enhance fungal pathogenesis. Unexpectedly, UmPce3 also influences host tolerance to salt stress thereby balancing the plant response to biotic and abiotic stressors in support of biotrophic development.

plant biology↗

bioRxiv2026

Systematic Infectome-Phenome Profiling Reveals Cryptococcal Infection-Associated Proteins Driving Immune System Remodeling and Immunization Potential

Mortality and morbidity associated with invasive fungal infections continue to rise, driven by the emergence of new pathogens, increasing antifungal resistance, and expanding immunocompromised populations. Despite this growing threat, fungal biology lacks scalable, unbiased strategies to link infection-responsive fungal proteins to functional outcomes that drive virulence and immune modulation. Here, we present an integrated infectome-phenome discovery platform that combines high resolution mass spectrometry-based proteomics with systematic phenotypic profiling to globally interrogate Cryptococcus neoformans-macrophage interactions. This approach reveals coordinated host immune suppression alongside complementary fungal virulence programs and enables the unbiased prioritization of infection-associated fungal proteins. Systematic phenome fingerprinting of candidate mutant strains resolves two functional classes of putative therapeutic relevance: antifungal and antivirulence, with in vitro characterizations corroborated with a murine model of cryptococcosis. Prioritization of a conserved, previously uncharacterized virulence-associated protein, CipC, uncovers altered extracellular vesicle composition and enhanced antigenic properties. Immunization with CipC-derived vesicles elicits a robust and diversified host immune response, implicating fungal extracellular vesicles in immune remodeling and host priming. Together, these findings establish a broadly applicable framework for systematically identifying and functionally characterizing fungal drivers of infection for therapeutic and immunological target discovery with relevance across diverse human fungal pathogens.

microbiology↗

bioRxiv2025

Mycotoxin-driven proteome remodeling reveals limited activation of Triticum aestivum responses to emerging chemotypes integrated with fungal modulation of ergosterols

Fusarium head blight (FHB), mainly caused by Fusarium graminearum, is a globally important wheat disease reducing yield and grain quality. The pathogen produces mycotoxins deoxynivalenol (DON), 3-acetyl DON (3ADON), 15-acetyl DON (15ADON), and nivalenol (NIV), which threaten food and feed safety. During the past 15 years, surveillance has identified nove trichothecenes 3ANX and NX, which show increased virulence compared to DON. In this study, we investigated the effects of 15ADON/3ANX chemotype on both wheat and F. graminearum proteomes to identify proteins and pathways responsive to the emerging mycotoxin chemotype. We defined a core wheat proteome across all strains (15ADON- and 15ADON/3ANX-producing, and untreated controls) to explore changes in protein abundance associated with defense response, grain development, and reduced photosynthesis upon infection. Conversely, we identified 32 wheat proteins exclusively produced in the presence of 15ADON/3ANX strains, providing further insight into chemotype-specific responses of wheat. Additionally, assessment from the fungal perspective, reported 119 proteins exclusive to the 15ADON/3ANX strains, including those associated with virulence and mycotoxin production. Lastly, investigation of strain-specific proteome changes showed a significant reduction in mycotoxin protective mechanisms in wheat upon exposure to two 15ADON/3ANX strains, as well as a novel connection between elevated ergosterol biosynthesis and 15ADON/3ANX producing strains. Together, our study characterizes distinct protein production profiles in wheat and F. graminearum in response to 3ANX and provides evidence that these molecular changes influence fungal virulence and host defense responses.

plant biology↗

bioRxiv2025

Global proteomic analysis of Cryptococcus neoformans clinical strains reveals significant differences between latent and lethal infection

To predict the outcomes of disseminated fungal disease, a deeper understanding of host-pathogen interactions at the site of infection is needed to identify targets for clinical intervention and diagnostic development. Cryptococcus neoformans is the causative agent of cryptococcosis, the largest infectious killer of individuals living with HIV. Cryptococcal infection begins in the lungs, with loss of immunological control leading to disseminated central nervous system disease and death. Using advanced mass spectrometry-based proteomic techniques, in vivo infection models, and patient-derived clinical strains, we explored the proteomic profiles of C. neoformans infections related to differences in strain virulence. Our findings reveal that non-lethal latent infection produces a proteomic response that differs significantly from the response caused by lethal infections, and that the proteomic profiles of typical and hypervirulent infections are markedly similar despite differences in time-to-death. Overall, the mouse pulmonary proteomic response in latent infection is defined by enrichment of proteins and pathways involved in extracellular matrix organization, cell adhesion, and structural changes, while the lethal infection is dominated by host-defense, translation, and metabolic processes. These results provide clinically relevant information on how infections caused by different Cryptococcus strains may produce significantly different outcomes. We also identified abundant fungal proteins that could be future drug targets in latent and lethal cryptococcal infection. IMPORTANCECryptococcus neoformans is a fungal pathogen that causes substantial morbidity and mortality in immunocompromised individuals. The initial infection begins in the lungs after exposure to inhaled spores after which local immune cells respond by either killing or containing the fungal cells. Immunosuppression weakens the immune system and allows fungal cells in the lungs to escape through the circulatory system and invade the central nervous system and cause fatal disease. However, differences between fungal strains influence the severity of disease manifestation. Our group has previously described genetic differences that contribute to strain-specific disease manifestations. In this study, we expanded our analysis to investigate the proteomic differences between strains of C. neoformans to identify candidate proteins and pathways that contribute to disease manifestation. We found that latent infection differs significantly from lethal disease from both the host and pathogen proteomic perspectives and have identified several fungal protein targets for future study.

microbiology↗

bioRxiv2025

Spatiotemporal dynamics of cryptococcal infection reveal novel immune modulatory mechanisms and antifungal targets

The threat and incidence of fungal diseases are increasing, as is the severity and mortality rates associated with these infections. New strategies to combat fungal infections are urgently needed to overcome rising rates of resistance and the emergence of new pathogens. To promote invasion within a host, fungi use highly adapted and regulated virulence factors, and, in turn, the host adopts an active and dynamic immune response to suppress infection. Understanding the interplay between these processes is crucial to move fungal disease management and treatment forward and improve global health outcomes. Within the present study, we tackle these challenges using state-of-the-art mass spectrometry instrumentation to explore proteome remodeling during active infection of Cryptococcus neoformans at an unprecedented depth with spatiotemporal resolution. Our prioritization of three host organs (i.e., lungs, brain, spleen) critical to initiation, progression, and response of disease discovers tissue-specific remodeling across time. Within the lungs, we revealed early and sustained activation of the host immune response integrated with characterization of a promising new antifungal target, and we propose the discovery of a competitive inhibitor for functional target disruption. Within the brain, proteome remodeling aligns with disease progression, and we define a new mechanistic role for haptoglobin in fungal cell modulation, as well as showcasing an adaptive survival response of C. neoformans within an hypoxic environment. Within the spleen, we reveal new dynamics of immune system activation upon cryptococcal infection. Overall, we provide the deepest integrated view of cryptococcal disease dynamics across temporal and spatial scales, revealing unrecognized mechanisms of host immunity and fungal pathogenesis that offer new avenues for targeted therapeutic intervention and disease management.

microbiology↗

bioRxiv2025

Whole blood proteome dynamics defines predictive diagnostic and prognostic signatures of cryptococcal infection

Across the globe, fungi are impacting the lives of millions of people through the development of infections ranging from superficial to systemic with limited treatment options. To effectively combat fungal disease, rapid and reliable diagnostic methods are required, including current methodologies using antigen detection, culturing, microscopy, and molecular tools. However, the flexibility of these platforms to diagnose infection using non-invasive methods and predict the outcome of disease are limited. In this study, we apply state-of-the-art mass spectrometry-based proteomics to perform dual perspective (i.e., host and pathogen) profiling of cryptococcal infection. Whole blood collected over a temporal scale following murine model challenged with the human fungal pathogen, Cryptococcus neoformans, detected >3,000 host proteins and 160 fungal proteins. From the host perspective, temporal regulation of known immune-associated proteins, including eosinophil peroxidase and lipocalin-2, along with suppression of lipoproteins, demonstrated infection- and time-dependent host remodeling. Conversely, from the pathogen perspective, known and putative virulence-associated proteins were detected, including proteins associated with fungal extracellular vesicles and host immune modulation. We also observed and validated a new mechanism of immune system response to C. neoformans through modulation of haptoglobin. Further, we assessed the predictive power of dual perspective proteome profiling toward prognostics of cryptococcal infection and report a previously undisclosed integration among virulence factor production, immune system modulation, and individual model survival. Together, our findings pose novel biomarkers of cryptococcal infection from whole blood and highlight the potential of personal proteome profiles to determine the prognosis of cryptococcal infection, a new parameter in fungal disease management.

microbiology↗

bioRxiv2024

ProteoPlotter: an executable proteomics visualization tool compatible with Perseus

Mass spectrometry-based proteomics experiments produce complex datasets requiring robust statistical testing and effective visualization tools to ensure meaningful conclusions are drawn. The publicly-available proteomics data analysis platform, Perseus, is extensively used to perform such tasks, but opportunities to enhance visualization tools and promote accessibility of the data exist. In this study, we developed ProteoPlotter, a user-friendly, executable tool to complement Perseus for visualization of proteomics datasets. ProteoPlotter is built on the Shiny framework for R programming and enables illustration of multi-dimensional proteomics data. ProteoPlotter provides mapping of one-dimensional enrichment analyses, enhanced adaptability of volcano plots through incorporation of Gene Ontology terminology, visualization of 95% confidence intervals in principal component analysis plots using data ellipses, and customizable features. ProteoPlotter is designed for intuitive use by biological and computational researchers alike, providing descriptive instructions (i.e., Help Guide) for preparing and uploading Perseus output files. Herein, we demonstrate the application of ProteoPlotter towards microbial proteome remodeling under altered nutrient conditions and highlight the diversity of visualizations enabled with the platform for improved biological characterization. Through its comprehensive data visualization capabilities, linked to the power of Perseus data handling and statistical analyses, ProteoPlotter facilitates a deeper understanding of proteomics data to drive new biological discoveries.

bioinformatics↗

bioRxiv2023

Soybean-SCN duel: Novel insight into Soybean's Resistant Responses to Heterodera glycines

Soybean cyst nematodes (SCN, Heterodera glycines Ichinohe) are a significant threat to soybean production globally, causing severe yield losses and necessitating the development of effective strategies to combat this devastating nematode disease. This study presents dual RNA-seq analyses of the three most common SCN-resistant lines (Plant Introduction (PI) 437654, 548402, and 88788) and the susceptible line Lee74 against the SCN HG type 1.2.5.7 to identify the mechanisms of resistance and virulence genes involved in resistance breakdown. Transcriptomic and pathway analyses reveal the activation of the phenylpropanoid pathway, MAPK signaling pathway, plant hormone signal transduction, and secondary metabolite pathways in the resistance mechanisms. PI 437654, which exhibited robust resistance (female index, FI=0%), demonstrated unique gene expression associated with cell wall reinforcement, oxidative enzymes, ROS scavengers, and Ca+2 sensors governing the salicylic acid (SA) biosynthesis process, indicating its key defense mechanism. Moreover, using different hosts with varying levels of immunity and a susceptible line provided insights into SCN pathogenesis and how H. glycine overcomes different layers of host immunity by modulating its virulence genes. This research provides novel insights into the molecular mechanisms underlying soybean-SCN interactions and identifies potential targets for developing strategies to manage this devastating nematode disease.

plant biology↗

bioRxiv2023

Resolving the temporal splenic proteome during fungal infection for discovery of putative dual perspective biomarker signatures

Fungal pathogens are emerging threats to global health with the rise of incidence associated with climate change and increased geographical distribution; factors also influencing host susceptibility to infection. Accurate detection and diagnosis of fungal infections is paramount to offer rapid and effective therapeutic options. For improved diagnostics, the discovery and development of protein biomarkers presents a promising avenue; however, this approach requires a priori knowledge of infection hallmarks. To uncover putative novel biomarkers of disease, profiling of the host immune response and pathogen virulence factor production is indispensable. In this study, we use mass spectrometry-based proteomics to resolve the temporal proteome of Cryptococcus neoformans infection of the spleen following a murine model of infection. Dual perspective proteome profiling defines global remodeling of the host over a time course of infection, confirming activation of immune associated proteins in response to fungal invasion. Conversely, pathogen proteomes detect well-characterized C. neoformans virulence determinants, along with novel mapped patterns of pathogenesis during the progression of disease. Together, our innovative systematic approach confirms immune protection against fungal pathogens and explores the discovery of putative biomarker signatures from complementary biological systems to monitor the presence and progression of cryptococcal disease.

microbiology↗

bioRxiv2023

Integration of homeostatic and adaptive oxidative responses by a putative co-chaperone, Wos2, drives fungal virulence in cryptococcosis

The increasing prevalence of invasive fungal pathogens are dramatically changing the clinical landscape of infectious diseases and are an imminent burden to public health that lack the resources (i.e., robust antifungals) to tackle this threat. Specifically, the human opportunistic pathogen, Cryptococcus neoformans, expresses elaborate virulence mechanisms and is equipped with sophisticated adaptation strategies to survive in harsh host environments. In this study, we extensively characterize Wos2, an Hsp90 co-chaperone homologue, featuring bilateral functioning for both cryptococcal adaptation and virulence strategies. Here, we evaluated the proteome and secretome signatures of Wos2 in enriched and infection-mimicking conditions to reveal a Wos2-dependent regulation of oxidative stress response. The wos2{Delta} strain reports defective intracellular and extracellular antioxidant protection systems measurable through a decreased abundance of critical antioxidant enzymes and reduced growth in the presence of peroxide stress. Additional Wos2-associated stress phenotypes were observed upon fungal challenge with heat shock, osmotic, and cell wall stressors. We demonstrate the importance of Wos2 for C. neoformans intracellular lifestyle during in vitro macrophage infection and provide evidence for wos2{Delta} reduced phagosomal replication levels. Accordingly, wos2{Delta} featured significantly reduced virulence in a murine model of cryptococcosis. Our study highlights a vulnerable point in the fungal chaperone network that offers a powerful druggable opportunity to interfere with both virulence and fitness. Author SummaryThe global impact of fungal pathogens, both emerging and emerged, is undeniable and the alarming increase in antifungal resistance rates hampers our ability to protect the global population from deadly infections. For cryptococcal infections, a limited arsenal of antifungals and resistance demands alternative therapeutic strategies, including an anti-virulence approach, which disarms the pathogen of critical virulence factors, empowering the host to remove the pathogen and clear the infection. To this end, we apply state-of-the-art mass spectrometry-based proteomics to interrogate the impact of a recently defined novel co-chaperone, Wos2, towards cryptococcal virulence using in vitro and in vivo models of infection. We defined global proteome and secretome remodeling driven by the protein and uncovered a novel role in modulating the fungal oxidative stress response. Complementation of the proteome findings with in vitro infectivity assays demonstrated a protective role for Wos2 within the macrophage phagosome, influencing fungal replication and survival. These results underscore differential cryptococcal survivability and weakened patterns of dissemination in the absence of wos2. Overall, our study establishes Wos2 as an important contributor to fungal pathogenesis and warrants further research into critical proteins within global stress response networks as potential druggable targets to reduce fungal virulence and clear the infection.

microbiology↗

bioRxiv2022

The ER protein translocation channel subunit Sbh1 controls virulence of Cryptococcus neoformans

The fungal pathogen Cryptococcus neoformans is distinguished by a cell wall-anchored polysaccharide capsule that is critical for virulence. Biogenesis of both cell wall and capsule relies on the secretory pathway. Protein secretion begins with polypeptide translocation across the endoplasmic reticulum (ER) membrane through a highly conserved channel formed by three proteins: Sec61, Sbh1, and Sss1. Sbh1, the most divergent, contains multiple phosphorylation sites, which may allow it to regulate entry into the secretory pathway in a species- and protein-specific manner. Absence of SBH1 causes a cell-wall defect in both Saccharomyces cerevisiae and C. neoformans, although other phenotypes differ. Notably, proteomic analysis showed that when cryptococci are grown in conditions that mimic aspects of the mammalian host environment (tissue culture medium, 37 {degrees}C, 5% CO2), a set of secretory and transmembrane proteins is upregulated in wild-type, but not in{Delta} sbh1 mutant cells. The Sbh1-dependent proteins show specific features of their ER targeting sequences that likely cause them to transit less efficiently into the secretory pathway. Many also act in cell-wall biogenesis, while several are known virulence factors; consistent with these observations, the C. neoformans {Delta}sbh1 mutant is avirulent in a mouse infection model. We conclude that, in the context of conditions encountered during infection, Sbh1 controls the entry of virulence factors into the secretory pathway of C. neoformans, and thereby regulates fungal pathogenicity. ImportanceCryptococcus neoformans is a yeast that causes almost 200,000 deaths worldwide each year, mainly of immunocompromised individuals. The surface structures of this pathogen, a protective cell wall surrounded by a polysaccharide capsule, are made and maintained by proteins that are synthesized inside the cell and travel outwards through the secretory pathway. A protein called Sbh1 is part of the machinery that determines which polypeptides enter this export pathway. We found that when Sbh1 is absent, both C. neoformans and the model yeast S. cerevisiae show cell wall defects. Lack of Sbh1 also changes the pattern of secretion of both transmembrane and soluble proteins, in a manner that depends on characteristics of their sequences. Notably, multiple proteins that are normally upregulated in conditions similar to those encountered during infection, including several needed for cryptococcal virulence, are no longer increased. Sbh1 thereby regulates the ability of this important pathogen to cause disease.

microbiology↗

bioRxiv2021

Dual perspective proteomics infectome profiling discovers Salmonella type III secretion system effector functions in macrophages

Intracellular bacterial pathogens have evolved sophisticated infection strategies, including the release and secretion of virulence factors to interfere with host cell functions and to perturb immune responses. For Salmonella enterica serovar Typhimurium (S. Typhimurium), the type III secretion systems encoded on Salmonella pathogenicity islands (SPI) 1 and 2 mediates invasion of the bacterium into innate immune cells and regulates bacterial replication and survival within the hostile environment of the host, respectively. Here, we explore the temporal and strain-specific dual perspective response of both the host and pathogen during cellular infection via quantitative proteomics. We report time- and pathogenicity island-specific expression and secretion of infection-associated proteins (i.e., SL1344_1263, SL1344_3112, SL1344_1563, and YnhG) and regulated immune response proteins in macrophage, including Cd86, Cd40, Casp4, C3, IL-1, and Cd69). Through intracellular macrophage and in vivo murine models of infection, we reveal a role in virulence for three of the bacterial proteins (SL1344_1263, SL1344_1563, and YnhG), defining their importance as novel T3SS effectors. We characterize the temporal intra- and extracellular production of the effectors and identify their interaction networks in host cells, representing inhibitory and stimulatory pathways mounted by invading bacterial pathogens. Author SummaryThe relationship between a host and pathogen is intricate, and regulation of the host immune response correlates with the progressive timing of infection and tailored responses to the pathogen. Relying on detection and quantification of protein-level changes using mass spectrometry-based proteomics, we explore the production of known and novel effectors by Salmonella during intracellular survival within macrophage. Our results portray a role for these effectors in bacterial virulence using an in vivo murine model of infection, and we define a dynamic network of interaction between the effectors and host proteins. These interactions reveal opportunity for drug design to disrupt modulation of the host by the invading bacterium as a new strategy for combatting infection. Our approach is dynamic and universal, with the power to alter therapeutic discovery against infectious diseases.

microbiology↗