Biology subjects

Hanna-Rose, W.

Publications and source records attributed to Hanna-Rose, W..

3 recordsLinked to original sources

bioRxiv2021

The purine nucleoside phosphorylase pnp-1 regulates epithelial cell resistance to infection in C. elegans

Intestinal epithelial cells are subject to attack by a diverse array of microbes, including intracellular as well as extracellular pathogens. While defense in epithelial cells can be triggered by pattern recognition receptor-mediated detection of microbe-associated molecular patterns, there is much to be learned about how they sense infection via perturbations of host physiology, which often occur during infection. A recently described host defense response in the nematode C. elegans called the Intracellular Pathogen Response (IPR) can be triggered by infection with diverse natural intracellular pathogens, as well as by perturbations to protein homeostasis. From a forward genetic screen, we identified the C. elegans ortholog of purine nucleoside phosphorylase pnp-1 as a negative regulator of IPR gene expression, as well as a negative regulator of genes induced by extracellular pathogens. Accordingly, pnp-1 mutants have resistance to both intracellular and extracellular pathogens. Metabolomics analysis indicates that C. elegans pnp-1 likely has enzymatic activity similar to its human ortholog, serving to convert purine nucleosides into free bases. Classic genetic studies have shown how mutations in human purine nucleoside phosphorylase cause immunodeficiency due to T-cell dysfunction. Here we show that C. elegans pnp-1 acts in intestinal epithelial cells to regulate defense. Altogether, these results indicate that perturbations in purine metabolism are likely monitored as a cue to promote defense against epithelial infection in the nematode C. elegans. Author summaryAll life requires purine nucleotides. However, obligate intracellular pathogens are incapable of generating their own purine nucleotides and thus have evolved strategies to steal these nucleotides from host cells in order to support their growth and replication. Using the small roundworm C. elegans, we show that infection with natural obligate intracellular pathogens is impaired by loss of pnp-1, the C. elegans ortholog of the vertebrate purine nucleoside phosphorylase (PNP), which is an enzyme involved in salvaging purines. Loss of pnp-1 leads to altered levels of purine nucleotide precursors and increased expression of Intracellular Pathogen Response genes, which are induced by viral and fungal intracellular pathogens of C. elegans. In addition, we find that loss of pnp-1 increases resistance to extracellular pathogen infection and increases expression of genes involved in extracellular pathogen defense. Interestingly, studies from 1975 found that mutations in human PNP impair T-cell immunity, whereas our findings here indicate C. elegans pnp-1 regulates intestinal epithelial immunity. Overall, our work indicates that host purine homeostasis regulates resistance to both intracellular and extracellular pathogen infection.

immunology↗

bioRxiv2017

A Caenorhabditis elegans model of adenylosuccinate lyase deficiency reveals neuromuscular and reproductive phenotypes of distinct etiology

Inborn errors of purine metabolism are rare syndromes with an array of complex phenotypes in humans. One such disorder, adenylosuccinate lyase deficiency (ASLD), is caused by a decrease in the activity of the bi-functional purine biosynthetic enzyme, adenylosuccinate lyase (ADSL). Mutations in human ADSL cause epilepsy, muscle ataxia, and autistic-like symptoms. Although the genetic basis of ASLD syndrome is known, the molecular mechanisms driving phenotypic outcome are not. Here, we characterize neuromuscular and reproductive phenotypes associated with a deficiency of adsl-1 in Caenorhabditis elegans. Characterization of the neuromuscular phenotype reveals a disruption of cholinergic transmission affecting muscular contraction. Using genetics, pharmacological supplementation, and metabolite measurements, we correlate phenotypes with distinct metabolic perturbations. The neuromuscular defect is associated with a toxic accumulation of a purine biosynthetic intermediate whereas the reproductive defect can be ameliorated by purine supplementation, indicating differing molecular mechanisms behind the phenotypes of ASLD. Because purine metabolism is highly conserved in metazoans, we suggest that similar separable metabolic perturbations result in the varied symptoms in the human disorder and that a dual-approach therapeutic strategy may be beneficial.

genetics↗

bioRxiv2017

Mitochondrial sirtuins sir-2.2 and sir-2.3 regulate lifespan in C. elegans

Mitochondrial sirtuins regulate biochemical pathways and are emerging drug targets for metabolic and age-related diseases such as cancer, diabetes, and neurodegeneration. Yet, their functions remain unclear. Here, we uncover a novel physiological role for the C. elegans mitochondrial sirtuins, sir-2.2 and sir-2.3, in lifespan regulation. Using a genetic approach, we demonstrate that sir-2.2 and sir-2.3 mutants live 28-30% longer than controls when fed the normal lab diet of E. coli OP50. Interestingly, this effect is diet specific and is not observed when animals are fed the strain HT115, which is typically used for RNAi experiments. While decreased consumption of food is a known mechanism for lifespan extension, this does not account for the increased lifespan in the mitochondrial sirtuin mutants. sir-2.2 and sir-2.3 mutants display altered expression of genes involved in oxidative stress response, including increased expression of the mitochondrial superoxide dismutase sod-3 and decreased levels of catalases ctl-1 and ctl-2. Like their extended lifespan phenotype, these alterations in oxidative stress gene expression are diet dependent. The mitochondrial sirtuin mutants are more resistant to the lifespan extending effects of low levels of superoxide, suggesting that their increased lifespan involves a hormetic response. Our data suggest that sir-2.2 and sir-2.3 are not completely redundant in function and may possess overlapping yet distinct mechanisms for regulating oxidative stress response and lifespan.

genetics↗