Biology subjects

Benns, H. J.

Publications and source records attributed to Benns, H. J..

5 recordsLinked to original sources

bioRxiv2021

An extracellular redox signal triggers calcium release and impacts the asexual development of Toxoplasma gondii

The ability of an organism to sense and respond to environmental redox fluctuations relies on a signaling network that is incompletely understood in apicomplexan parasites such as Toxoplasma gondii. The impact of changes in redox upon the development of this intracellular parasite is not known. Here, we provide a revised collection of 58 genes containing domains related to canonical antioxidant function, with their encoded proteins widely dispersed throughout different cellular compartments. We demonstrate that addition of exogenous H2O2 to human fibroblasts infected with T. gondii triggers a Ca2+ flux in the cytosol of intracellular parasites that can induce egress. In line with existing models, egress triggered by exogenous H2O2 is reliant upon both Calcium-Dependent Protein Kinase 3 and diacylglycerol kinases. Finally, we show that the overexpression a glutaredoxin-roGFP2 redox sensor fusion protein in the parasitophorous vacuole severely impacts parasite replication. These data highlight the rich redox network that exists in T. gondii, evidencing a link between extracellular redox and intracellular Ca2+ signaling that can culminate in parasite egress. Our findings also indicate that the redox potential of the intracellular environment contributes to normal parasite growth. Combined, our findings highlight the important role of redox as an unexplored regulator of parasite biology.

microbiology↗

bioRxiv2021

Prioritization of antimicrobial targets by CRISPR-based oligo recombineering

Nucleophilic amino acids are important in covalent drug development yet underutilized as antimicrobial targets. Over recent years, several chemoproteomic technologies have been developed to mine chemically-accessible residues via their intrinsic reactivity toward electrophilic probes. However, these approaches cannot discern which reactive sites contribute to protein function and should therefore be prioritized for drug discovery. To address this, we have developed a CRISPR-based Oligo Recombineering (CORe) platform to systematically prioritize reactive amino acids according to their contribution to protein function. Our approach directly couples protein sequence and function with biological fitness. Here, we profile the reactivity of >1,000 cysteines on ~700 proteins in the eukaryotic pathogen Toxoplasma gondii and prioritize functional sites using CORe. We competitively compared the fitness effect of 370 codon switches at 74 cysteines and identify functional sites in a diverse range of proteins. In our proof of concept, CORe performed >800 times faster than a standard genetic workflow. Reactive cysteines decorating the ribosome were found to be critical for parasite growth, with subsequent target-based screening validating the apicomplexan translation machinery as a target for covalent ligand development. CORe is system-agnostic, and supports expedient identification, functional prioritization, and rational targeting of reactive sites in a wide range of organisms and diseases.

microbiology↗

bioRxiv2020

Cellular barcoding of Toxoplasma reveals permissive host brain colonization

Molecular barcoding techniques have emerged as powerful tools to understand microbial pathogenesis. However, barcoding strategies have not been extended to protozoan parasites, which have unique genomic structures and virulence strategies compared to viral and bacterial pathogens. Here, we present a versatile CRISPR-based method to barcode protozoa, which we successfully apply to Toxoplasma gondii and Trypanosoma brucei. The murine brain is an important transmission niche for T. gondii, and brain persistence is a clinically untreatable feature of infection. The blood-brain barrier is expected to physically restrict parasite colonization of this niche, resulting in a selection bottleneck. Using libraries of barcoded T. gondii we evaluate shifts in the population structure from acute to chronic infection of mice. Contrary to expectation, most barcodes were present in the brain one-month post-intraperitoneal infection in both inbred CBA/J and outbred Swiss mice. Although parasite cyst number and barcode diversity declined over time, barcodes that represented a minor fraction of the inoculum could become a dominant population in the brain by three months post-infection. Together, these data establish the first, robust molecular barcoding approach for protozoa and evidence that the blood-brain barrier does not represent a major bottleneck to colonization by T. gondii.

microbiology↗

bioRxiv2020

CRISPR-TAPE: protein-centric CRISPR guide design for targeted proteome engineering

Rational molecular engineering of proteins with CRISPR-based approaches is challenged by the gene-centric nature of gRNA design tools. To address this, we have developed CRISPR-TAPE, a protein-centric gRNA design algorithm that allows users to target specific residues, or amino acid types within proteins. gRNA outputs can be customized to support maximal efficacy of homology-directed repair for engineering purposes, removing time consuming post-hoc curation, simplifying gRNA outputs, and reducing CPU times.

bioinformatics↗

bioRxiv2018

Dynamic regulation of the Trypanosoma brucei transferrin receptor in response to iron starvation is mediated via the 3UTR

The bloodstream form of the parasite Trypanosoma brucei obtains iron from its mammalian host by receptor-mediated endocytosis of host transferrin through its own unique transferrin receptor (TbTfR). Expression of TbTfR rapidly increases upon iron starvation by post-transcriptional regulation through a currently undefined mechanism that is distinct from the mammalian iron response system. We have created reporter cell lines by fusing the TbTfR 3'UTR or a control Aldolase 3UTR to reporter genes encoding GFP or firefly Luciferase, and inserted the fusions into a bloodstream form cell line at a tagged ribosomal RNA locus. Fusion of the TbTfR 3UTR is sufficient to significantly repress the expression of the reporter proteins under normal growth conditions. Under iron starvation conditions we observed upregulation of the TbTfR 3UTR fusions only, with a magnitude and timing consistent with that reported for upregulation of the TbTfR. We conclude that the dynamic regulation of the T. brucei transferrin receptor in response to iron starvation is mediated via its 3UTR, and that the effect is independent of genomic location.

cell biology↗