Biology subjects

Schertzberg, M. R.

Publications and source records attributed to Schertzberg, M. R..

4 recordsLinked to original sources

bioRxiv2023

Natural variation in expression of the mitochondrial flavoprotein WAH-1 alters response to cyanide in C. elegans

C. elegans is a free-living nematode that must adapt to a wide range of environments including both aerobic and anaerobic conditions. To survive in low oxygen, C. elegans can use an unusual form of anaerobic respiration that relies on rhodoquinone (RQ) as an alternative electron carrier. Parasitic nematodes like hookworm and whipworm also require rhodoquinone-dependent metabolism (RQDM) to survive in the highly anaerobic conditions in the human gut. Understanding how RQDM is regulated in C. elegans may thus identify new ways to combat these closely-related major human pathogens. We previously established a simple movement-based assay for RQDM in C. elegans. In this study, we tested a panel of wild-type isolates of C. elegans in our RQDM assay and find substantial variation in their ability to use RQDM. We carried out a genome-wide association study (GWAS) to identify loci that affect RQDM -- this identified a single major QTL on the right arm of Chromosome III. We used RNAi to test almost all genes within the QTL region for involvement in RQDM and found one gene, wah-1, that strongly modulates RQDM-dependent recovery in C. elegans. WAH-1 is a mitochondrial flavoprotein that affects the electron transport chain, consistent with a role in RQDM. We show that wah-1 expression varies between isolates due to major changes in wah-1 transcript structures and this correlates tightly with variation in RQDM. Finally, we show that there is similar complexity to wah-1 transcription in parasitic nematodes and that wah-1 transcript structures change as parasites shift from aerobic to anaerobic, RQ- requiring metabolism. We thus conclude that reduced wah-1 expression correlates with increased ability to survive in conditions where RQDM is essential.

molecular biology↗

bioRxiv2021

An intestinally secreted host factor limits bacterial colonization but promotes microsporidia invasion of C. elegans

Microsporidia are ubiquitous obligate intracellular pathogens of animals. These parasites often infect hosts through an oral route, but little is known about the function of host intestinal proteins that facilitate microsporidia invasion. To identify such factors necessary for infection by Nematocida parisii, a natural microsporidian pathogen of Caenorhabditis elegans, we performed a forward genetic screen to identify mutant animals that have a Fitness Advantage with Nematocida (Fawn). We isolated four fawn mutants that are resistant to Nematocida infection and contain mutations in T14E8.4, which we renamed aaim-1 (Antibacterial and Aids invasion by Microsporidia). Expression of AAIM-1 in the intestine of aaim-1 animals restores N. parisii infectivity and this rescue of infectivity is dependent upon AAIM-1 secretion. N. parisii spores in aaim-1 animals are improperly oriented in the intestinal lumen, leading to reduced levels of parasite invasion. Conversely, aaim-1 mutants display both increased colonization and susceptibility to the bacterial pathogen Pseudomonas aeruginosa and overexpression of AAIM-1 reduces P. aeruginosa colonization. Competitive fitness assays show that aaim-1 mutants are favoured in the presence of N. parisii but disadvantaged on P. aeruginosa compared to wild type animals. Together, this work demonstrates how microsporidia exploits a secreted protein to promote host invasion. Our results also suggest evolutionary trade-offs may exist to optimizing host defense against multiple classes of pathogens.

microbiology↗

bioRxiv2021

Identification of enzymes that are required for Rhodoquinone-dependent metabolism as targets for new species-specific inhibitors

Soil transmitted helminths (STHs) are major human pathogens that infect over a billion people. Resistance to current anthelmintics is rising and new drugs are needed. Here we combine multiple approaches to find druggable targets that are essential for RQ-dependent metabolism, an unusual form of anaerobic metabolism which STHs need to survive in their host. We identified 25 genes predicted to act in RQ-dependent metabolism from sensing hypoxia to RQ synthesis -- this includes components of the kynurenine pathway we previously showed to be essential for RQ synthesis (Del Borrello et al., 2019). We found 9 genes to be required -- since all have host orthologues, we used comparative genomics and structural modeling to identify those with helminth-specific active sites and found 4 such targets. These 4 high confidence targets open up the possibility of in silico screens to identify STH-specific inhibitors of these enzymes as new anthelmintics.

molecular biology↗

bioRxiv2020

Alternative splicing of COQ-2 determines the choice between ubiquinone and rhodoquinone biosynthesis in helminths

Parasitic helminths use two benzoquinones as electron carriers in the electron transport chain. In aerobic environments they use ubiquinone (UQ) but in anaerobic environments inside the host, they require rhodoquinone (RQ) and greatly increase RQ levels. The switch to RQ synthesis is driven by substrate selection by the polyprenyltransferase COQ-2 but the mechanisms underlying this substrate choice are unknown. We found that helminths make two coq-2 isoforms, coq-2a and coq-2e, by alternative splicing. COQ-2a is homologous to COQ2 from other eukaryotes but the COQ-2e-specific exon is only found in species that make RQ and its inclusion changes the enzyme core. We show COQ-2e is required for RQ synthesis and for survival in cyanide in C. elegans. Crucially, we see a switch from COQ-2a to COQ-2e as parasites transition into anaerobic environments. We conclude that under anaerobic conditions helminths switch from UQ to RQ synthesis via alternative splicing of coq-2.

molecular biology↗