Biology subjects

Lodge, J.

Publications and source records attributed to Lodge, J..

4 recordsLinked to original sources

bioRxiv2026

Molecular Architecture of Cryptococcus Cell Walls Reveals Species-Specific Chitosan-Dependent Remodeling

Cryptococcus neoformans and Cryptococcus gattii are fungal pathogens that cause life-threatening infections, including cryptococcal meningitis. A distinctive feature of the cryptococcal cell wall is the extensive deacetylation of chitin to chitosan, a modification that is essential for virulence but whose structural role in cell-wall organization remains poorly understood. Here, we analyzed the cell walls of wild-type strains of both species and their avirulent chitosan-deficient mutants, which serve as vaccine candidates. Loss of chitosan disrupted cell morphology and altered cell-wall ultrastructure, with more pronounced defects in C. neoformans. Solid-state NMR revealed that aggregated -1,3-glucans form the principal rigid domain of the cell wall in both species and are closely associated with chitin microfibrils, whereas surrounding {beta}-glucans and mannoproteins constitute a more dynamic matrix. Chitosan modulates hydration and flexibility, and its loss increases chitin exposure and triggers species-specific remodeling of the polysaccharide network. In C. neoformans, chitosan depletion increased -1,3-glucan content and reduced {beta}-glucan levels, whereas C. gattii selectively lost one -1,3-glucan subtype while maintaining {beta}-glucan levels. Although capsule production remained intact, chitosan deficiency altered glucuronoxylomannan linkage patterns and mannoprotein composition. These findings reveal how chitosan organizes cryptococcal cell-wall architecture and highlight distinct structural adaptation strategies among pathogenic Cryptococcus species.

biochemistry↗

bioRxiv2024

Immunological correlates of protection mediated by a whole organism Cryptococcus neoformans vaccine deficient in chitosan

The global burden of infections due to the pathogenic fungus Cryptococcus is substantial in persons with low CD4+ T cell counts. Previously, we deleted three chitin deacetylase genes from C. neoformans to create a chitosan-deficient, avirulent strain, designated cda1{Delta}2{Delta}3{Delta} which, when used as a vaccine, protected mice from challenge with virulent C. neoformans strain KN99. Here, we explored the immunological basis for protection. Vaccine-mediated protection was maintained in mice lacking B cells or CD8+ T cells. In contrast, protection was lost in mice lacking /{beta} T cells or CD4+ T cells. Moreover, CD4+ T cells from vaccinated mice conferred protection upon adoptive transfer to naive mice. Importantly, while monoclonal antibody-mediated depletion of CD4+ T cells just prior to vaccination resulted in complete loss of protection, significant protection was retained in mice depleted of CD4+ T cells after vaccination, but prior to challenge. Vaccine-mediated protection was lost in mice genetically deficient in IFN{gamma}, TNF, or IL-23p19. A robust influx of leukocytes and IFN{gamma}- and TNF-expressing CD4+ T cells was seen in the lungs of vaccinated and challenged mice. Finally, a higher level of IFN{gamma} production by lung cells stimulated ex vivo correlated with lower fungal burden in the lungs. Thus, while B cells and CD8+ T cells are dispensable, IFN{gamma} and CD4+ T cells have overlapping roles in generating protective immunity prior to cda1{Delta}2{Delta}3{Delta} vaccination. However, once vaccinated, protection becomes less dependent on CD4+ T cells, suggesting a strategy for vaccinating HIV+ persons prior to loss of CD4+ T cells. ImportanceThe fungus Cryptococcus neoformans is responsible for >100,000 deaths annually, mostly in persons with impaired CD4+ T cell function such as AIDS. There are no approved human vaccines. We previously created a genetically engineered avirulent strain of C. neoformans, designated cda1{Delta}2{Delta}3{Delta}. When used as a vaccine, cda1{Delta}2{Delta}3{Delta} protects mice against a subsequent challenge with a virulent C. neoformans strain. Here, we defined components of the immune system responsible for vaccine-mediated protection. We found that while B cells and CD8+ T cells were dispensible, protection was lost in mice genetically deficient in CD4+ T cells, and the cytokines IFN{gamma}, TNF, or IL-23. A robust influx of cytokine-producing CD4+ T cells was seen in the lungs of vaccinated mice following infection. Importantly, protection was retained in mice depleted of CD4+ T cells following vaccination, suggesting a strategy to protect persons who are at risk for future CD4+ T cell dysfunction.

immunology↗

bioRxiv2021

3D Structure Determination of Protein Complexes using Matrix-Landing Mass Spectrometry

Native mass spectrometry (MS) is an emerging technology that can provide complementary data to electron microscopy (EM) for protein structure characterization. Beyond the ability to provide mass measurements of gas-phase biomolecular ions, MS instruments offer the ability to purify, select, and precisely control the spatial location of these ions. Here we present a modified Orbitrap MS system capable of depositing a native MS ion beam onto EM grids. We further describe use of a chemical landing matrix that both preserves and protects the structural integrity of the deposited particles. With this system we obtained the first 3D reconstructed structure of gas-phase, deposited biomolecular ions - the 800 KDa protein complex GroEL. These data provide direct evidence that non-covalent protein complexes can indeed retain their condensed-phase structures following ionization and vaporization. Finally, we describe how further developments of this technology could pave the way to an integrated MS-EM technology with promise to provide improved cryo-EM sample preparation over conventional plunge-freezing techniques.

molecular biology↗

bioRxiv2018

The monothiol glutaredoxin Grx4 interacts with the Cryptococcus iron regulator Cir1 and regulates iron homeostasis and virulence in the Cryptococcus neoformans

The acquisition of iron and the maintenance of iron homeostasis are important aspects of the virulence in the pathogenic fungus Cryptococcus neoformans. In this study, we identified the monothiol glutaredoxin Grx4 as a binding partner of Cir1, a master regulator of iron-responsive genes and virulence factor elaboration in C. neoformans. Monothiol glutaredoxins are important regulators of iron homeostasis because of their conserved roles in [2Fe-2S] cluster sensing and trafficking. We confirmed that Grx4 binds Cir1 and demonstrated that iron repletion promotes the relocalization of Grx4 from the nucleus to the cytoplasm. Nuclear retention is partially dependent on Cir1 and also influenced by treatment with the proteasome inhibitor bortezomib. Cir1 remains in the nucleus in both iron replete and iron limiting conditions. We also found that a grx4{Delta} mutant displayed iron-related phenotypes similar to those of a cir1{Delta} mutant, including poor growth upon iron deprivation. Importantly, a grx4{Delta} mutant was avirulent in mice, a phenotype consistent with observed defects in the key virulence determinants, capsule and melanin, and poor growth at 37{degrees}C. A comparative transcriptome analysis of a grx4{Delta} mutant and the WT strain in low iron and iron-replete conditions confirmed a central role for Grx4 in iron homeostasis. Dysregulation of iron-related metabolism was consistent with grx4{Delta} mutant phenotypes related to oxidative stress, mitochondrial function, and DNA repair. Overall, the phenotypes of the grx4{Delta} mutant and the RNA-Seq analysis support the hypothesis that Grx4 functions as a sensor of iron levels, in part through an interaction with Cir1, to extensively regulate iron homeostasis and contribute to virulence.

microbiology↗