Biology subjects

Clark, E. H.

Publications and source records attributed to Clark, E. H..

4 recordsLinked to original sources

bioRxiv2025

Genomic Characterization of a Locally Transmitted Leishmania mexicana Isolate from Texas

Cutaneous leishmaniasis (CL) is caused by Leishmania species transmitted by sand flies. Although considered a neglected tropical disease, growing evidence indicates that local transmission can occur in subtropical, higher-resource regions where sand fly vectors are present, including the southern United States. Here, we report the first whole-genome sequence of Leishmania mexicana from an autochthonous U.S. case--a 3-year-old boy from Ellis County, Texas, with no travel history. Genomic DNA was extracted from a skin biopsy specimen and sequenced using Illumina technology. Phylogenomic analysis based on nuclear and mitochondrial SNPs confirmed the isolate as L. mexicana, clustering with other members of the L. mexicana complex. The parasite exhibited a predominantly disomic karyotype, with chromosome 30 displaying trisomy. We identified 172 genes with significant copy number variations, including genes involved in ubiquitination, nucleic acid metabolism, and protein translation. Additionally, 53,964 SNPs were detected, over 22,000 of which were predicted to have moderate or high functional impact, affecting genes linked to host-pathogen interactions, metabolic pathways, and signal transduction. This study provides the first genomic characterization of a locally acquired L. mexicana strain in the U.S. and underscores the value of molecular surveillance and increased clinical awareness of leishmaniasis in subtropical regions where competent vectors are present.

microbiology↗

bioRxiv2022

High-content phenotypic screen to identify small molecule enhancers of parkin-dependent ubiquitination and mitophagy

Mitochondrial dysfunction and aberrant mitochondrial homeostasis are key aspects of Parkinsons disease (PD) pathophysiology. Mutations in PINK1 and Parkin proteins lead to autosomal recessive PD, suggesting that defective mitochondrial clearance via mitophagy is key in PD etiology. Accelerating the identification and/or removal of dysfunctional mitochondria could therefore provide a disease-modifying approach to treatment. To that end, we performed a high-content phenotypic screen (HCS) of ~125,000 small molecules to identify compounds that positively modulate mitochondrial accumulation of the PINK1-Parkin-dependent mitophagy initiation marker p-Ser65-Ub in Parkin haploinsufficiency (Parkin +/R275W) human fibroblasts. Following confirmatory counter-screening and orthogonal assays, we selected compounds of interest that enhance mitophagy-related biochemical and functional endpoints in patient-derived fibroblasts. Identification of inhibitors of the ubiquitin-specific peptidase and negative regulator of mitophagy USP30 within our hits further validated our approach. The compounds identified provide a novel starting point for further investigation and optimisation.

cell biology↗

bioRxiv2021

Investigation of USP30 inhibition to enhance Parkin-mediated mitophagy: tools and approaches

Mitochondrial dysfunction is implicated in Parkinson disease (PD). Mutations in Parkin, an E3 ubiquitin ligase, can cause juvenile-onset Parkinsonism probably through impairment of mitophagy. Inhibition of the de-ubiquitinating enzyme USP30 may counter this effect to enhance mitophagy. Using different tools and cellular approaches, we wanted to independently confirm this claimed role for USP30. Pharmacological characterization of additional tool compounds that selectively inhibit USP30 are reported. The consequence of USP30 inhibition by these compounds, siRNA knockdown and overexpression of dominant-negative USP30 in the mitophagy pathway in different disease-relevant cellular models was explored. Knockdown and inhibition of USP30 showed increased p-Ser65-ubiquitin levels and mitophagy in neuronal cell models. Furthermore, patient-derived fibroblasts carrying pathogenic mutations in Parkin showed reduced p-Ser65-ubiquitin levels compared to wild-type cells, levels that could be restored using either USP30 inhibitor or dominant-negative USP30 expression. Our data provide additional support for USP30 inhibition as a regulator of the mitophagy pathway.

neuroscience↗

bioRxiv2017

Effects Of Curcumin Nanoformulations On Cellular Function In Niemann-Pick Disease Type C Astrocytes

Niemann-Pick disease type C1 (NPC disease) is a neurodegenerative multi-lipid lysosomal storage disease caused by mutations in the NPC1 gene presenting with reduced lysosomal Ca2+ signalling and inhibited late endosome-lysosome transport. Elevating cytosolic Ca2+ levels in NPC cells has been shown to reduce lysosomal lipid storage. Treating Npc1-/- mice with the Ca2+ modulator curcumin led to reduced lipid storage, improved life expectancy and function. These studies led to reported utilisation of curcumin supplements by NPC disease families despite there being no clinical evidence of benefit and a report indicating no benefit of nanoformulated curcumin in Npc1-/- mice. The aim of this study was to determine whether various commercially available curcumin nanoformulations were capable of reproducing the findings obtained with unformulated pharmaceutical grade curcumin. We compared seven curcumin nanoformulations in Npc1-/- mouse astrocytes. All the nanoformulations elevate cytosolic Ca2+ levels but only two lowered lysosomal lipid storage. Importantly, some caused elevations in NPC lysosomal storage and/or decreased cellular viability. Although this is an in vitro study, our findings suggest that care should be taken when contemplating the use of curcumin supplements for NPC disease.

pharmacology and toxicology↗