Biology subjects

Bird, L. E.

Publications and source records attributed to Bird, L. E..

3 recordsLinked to original sources

bioRxiv2025

Host cyclophilin-mediated maturation of an obligate intracellular bacterial surface virulence factor

Adaptation of obligate intracellular bacteria to the eukaryotic cytoplasm creates dependencies on host factors that comprise unique infection mechanisms and vulnerabilities compared to facultative intracellular species. Here, we identify the peptidylprolyl isomerase cyclophilin A (PPIA/CypA) as a convergent host dependency in obligate intracellular bacterial pathogens. Using a host-directed functional genetic screen in the emerging tick-borne pathogen Rickettsia parkeri, we find that PPIA promotes infection and actin-based motility through an unprecedented inter-kingdom surface protein maturation event that facilitates transmembrane translocation of the actin-nucleating virulence factor Sca2. PPIA is required for efficient R. parkeri infection across human and tick cells, and pharmacological inhibition of PPIA phenocopies the loss of Sca2 in vitro and in vivo. This dependency extends to Chlamydia trachomatis and Orientia tsutsugamushi but appears absent in multiple facultative intracellular species. Targeting of host PPIA may thus represent a shared infection dependency across obligate intracellular bacterial pathogens with unmet therapeutic needs.

microbiology↗

bioRxiv2025

Intralysosomal pathogens differentially influence the proteolytic potential of their niche

Avoiding lysosomal degradation is vital to the success of intracellular pathogens. The Gram-negative bacterium Coxiella burnetii and protozoan parasites of the Leishmania genus are unique in being able to replicate within the mature phagolysosomal compartment of host cells, though the exact mechanisms utilised to withstand this hostile environment are not clearly defined. We recently reported that C. burnetii removes the lysosomal protease cathepsin B during infection of mammalian cells. Here, we aimed to determine if this virulence strategy was also employed by the intralysosomal pathogen, Leishmania mexicana. In contrast to C. burnetii, decreases in the activity of specific cathepsins were not detected in L. mexicana-infected host cells as determined using immunoblotting and protease activity-based probes. Co-infection of THP-1 macrophage-like cells with both pathogens resulted in a proteolytic and secretory phenotype consistent with C. burnetii infection, suggesting that C. burnetii-induced remodelling of the lysosome is not influenced by L. mexicana. The host cell proteome and secretome of L. mexicana infected cells was defined using mass spectrometry. This confirmed that, unlike C. burnetii, L. mexicana does not induce increased abundance of lysosomal proteins either intracellularly or in the extracellular milieu. Collectively, this study reveals that although C. burnetii and L. mexicana reside in a phagolysosomal intracellular niche, they employ divergent mechanisms to survive within this hostile compartment.

microbiology↗

bioRxiv2020

What are we missing by using hydrophilic enrichment? Improving bacterial glycoproteome coverage using total proteome and FAIMS analysis.

Hydrophilic Interaction Liquid Chromatography (HILIC) glycopeptide enrichment is an indispensable tool for the high-throughput characterisation of glycoproteomes. Despite its utility, HILIC enrichment is associated with a number of short comings including requiring large amounts of starting material, potentially introducing chemical artefacts such as formylation, and biasing/under-sampling specific classes of glycopeptides. Here we investigate HILIC enrichment independent approaches for the study of bacterial glycoproteomes. Using three Burkholderia species (B. cenocepacia, B. dolosa and B. ubonensis) we demonstrate that short aliphatic O-linked glycopeptides are typically absent from HILIC enrichments yet are readily identified in whole proteome samples. Using Field Asymmetric Waveform IMS (FAIMS) fractionation we show that at low compensation voltages (CVs) short aliphatic glycopeptides can be enriched from complex samples providing an alternative means to identify glycopeptides recalcitrant to hydrophilic based enrichment. Combining whole proteome and FAIMS analysis we show that the observable glycoproteome of these Burkholderia species is at least 30% larger than initially thought. Excitingly, the ability to enrich glycopeptides using FAIMS appears generally applicable, with the N-linked glycopeptides of Campylobacter fetus subsp. fetus also enrichable at low FAIMS CVs. Taken together, these results demonstrate that FAIMS provides an alternative means to access glycopeptides and is a valuable tool for glycoproteomic analysis.

microbiology↗