Biology subjects

Olsen, D.

Publications and source records attributed to Olsen, D..

7 recordsLinked to original sources

bioRxiv2026

Dual plasmepsin IX and X inhibitors are refractory to development of resistance

Artemisinin-based combination therapies (ACTs) remain the cornerstone of malaria treatment, but emerging resistance threatens their efficacy. The potential for the development of drug resistance against plasmepsin X (PMX)-selective inhibitors and dual plasmepsin IX/X (PMIX/X) inhibitors was investigated in Plasmodium falciparum. A series of PMX-selective (WM4, WM76, WM92) and PMIX/X dual inhibitors (WM382, WM09, WM42) were characterised for potency against parasite growth and enzyme inhibition. In vitro selection experiments showed that all compounds had a high barrier to resistance, although parasites with reduced sensitivity to PMX-selective inhibitors could still be selected. Resistance mechanisms involved pmx gene amplification and point mutations (D245N, S315P, S359P, I363L) that alter inhibitor binding. Recombinant expression and Michaelis-Menten kinetics demonstrated that these mutations impair drug binding whilst preserving PMX catalytic function. Reverse genetics confirmed that introducing these mutations into the pmx gene resulted in decreased potency of the inhibitors. In this study, resistance to the PMIX/X dual inhibitors evaluated here could not be selected, despite prolonged selection pressure. Antimalarial Resistome Barcoding (AReBar) assays confirmed the absence of pre-existing resistance to either inhibitor class. Critically, PMIX/X dual inhibitors maintained efficacy against parasites with decreased sensitivity to PMX-selective compounds. These findings demonstrate that dual PMIX/X inhibitors present a substantially higher barrier to resistance than PMX-selective inhibitors, informing antimalarial drug development strategies and highlighting dual-target inhibition as a promising approach to mitigate resistance risks.

microbiology↗

bioRxiv2025

Fifteen-year microbiome survey of endangered killer whales (Orcinus orca) reveals declining diversity and population differences

The endangered Southern Resident killer whale (Orcinus orca) (SRKW) population is burdened by multiple anthropogenic stressors with limited non-invasive approaches for health surveillance. The gut microbiome is interconnected with host physiology and can be characterized using remotely collected fecal samples, creating unique opportunities to integrate environmental and individualized host-associated features of health. In this study, we used fecal samples collected over a 15-year period (2005-2019) from 77% of the living, wild SRKW population (56 individuals, 1-17 time points per individual), as well as fecal samples from the conspecific Northern and Alaska Resident killer whale populations, to characterize distal gut microbiota structure and genomic composition. SRKW microbiotas were individualized and distinct from those of the nearby Northern and Alaska Resident populations, both of which exhibit consistently higher fecundity and survivorship. During the study period, SRKW fecal microbiota species richness declined, despite stability over periods of time less than or equal to 1 year. Several potential bacterial pathogens, such as Fusobacterium spp., achieved dominance in the fecal microbiotas of SRKW individuals sampled within 6 months of death. These findings demonstrate the feasibility and value of harnessing non-invasively collected fecal samples and microbiome profiles for longitudinal killer whale health surveillance.

microbiology↗

bioRxiv2025

Reshaping the progranulin/sortilin interaction for targeted degradation of extracellular proteins

Targeted protein degradation (TPD) using PROteolysis TArgeting Chimeras (PROTACs) is a rapidly emerging therapeutic strategy for difficult-to-drug cytosolic proteins. PROTACs are heterobifunctional small molecules that bridge the target with an E3 ubiquitin ligase, destining it for degradation by the proteasome. They have the potential to be orally available and to act catalytically, switching the pharmacology from occupancy-driven to event-driven (1-3). Here we present a strategy for targeted degradation of extracellular proteins by reshaping the interaction between the broadly expressed lysosome sorting receptor sortilin and its ligand progranulin for engineering SORtilin-based lysosome TArgeting Chimeras (SORTACs). SORTACs induce ternary complex formation with the target and sortilin, followed by endocytosis and lysosomal degradation. SORTAC activity can be genetically encoded as demonstrated by converting an IgG binding nanobody to an IgG degrading nanobody or by chemical conjugation, enabling single step conversion of therapeutic antibodies from binding their target to driving its degradation. Importantly, using structure-based design, we generated small molecule SORTACs against the inflammatory cytokine TNFa with nanomolar range potency and with physicochemical properties like PROTACs. Our results demonstrate that SORTACs constitute a versatile and highly modular platform for rapid generation of degraders of in theory any extracellular target and with the potential to have wide impact in drug discovery.

biochemistry↗

bioRxiv2024

The diverse diet of southern Alaska resident killer whales changes across spatiotemporally distinct foraging aggregations

Top predators influence ecological communities in part through the prey they consume, which they often track through cycles of seasonal and geographic abundance. Killer whales are top predators in the marine ecosystem. In the North Pacific, they have diverged into three distinct lineages with different diets, of which the fish-eating type is most abundant. In this study, we examine the diet of the southern Alaska resident killer whale population across three major foraging aggregations. We take advantage of two unique sampling methods to reveal strong spatiotemporal patterns in diet from May through September. Chinook, chum, and coho salmon were each dominant in different locations and times, with substantial dietary contributions from Pacific halibut, arrowtooth flounder, and sablefish. The diverse, location-specific, and seasonal nature of the feeding habits of this marine top predator highlights the importance of diet sampling across broad spatiotemporal and population-level scales.

ecology↗

bioRxiv2024

Widespread parasite infections in living resident killer whales in the Northeast Pacific Ocean

Multiple populations of resident ecotype killer whales (Orcinus orca ater) inhabit the Northeast Pacific, but the southern resident killer whale (SRKW) population is the most at-risk. SRKWs were listed as endangered in the United States in 2005 and have since shown little sign of recovery. Several factors have been identified as key threats to this population, and previously published studies suggest the population may be energetically stressed. Underlying health risks, such as parasitism, may be contributing to this populations failure to recover, but little is known about parasite infections in living individuals from natural killer whale populations. To assess the prevalence of internal parasite infections in Northeastern Pacific killer whales, we examined scat from endangered SRKW (n = 25) compared to two conspecific populations of resident killer whales that are not in decline: northern resident (NRKW, n = 2) and southern Alaska resident killer whales (SARKW, n = 7), and one offshore killer whale (OKW, n = 1). We analyzed 35 fecal samples collected from 27 wild killer whales using both microscopic identification of parasite eggs and genetic detection of parasites through DNA metabarcoding. We used body condition indices derived from concurrent aerial photogrammetry to evaluate whether parasite infection status was associated with individual body condition. We found that most individuals sampled (94%) were positive for Anisakis spp. - a parasitic nematode known to inhabit the intestines of cetaceans. These infections were detected across populations, and were not correlated with body condition, based on limited paired data. These results suggest that Anisakis infection is widespread among resident killer whales of the Northeast Pacific. The widespread detections of Anisakis among the samples examined here emphasizes the need for further work to understand the potential health impacts of parasitic infections on individual killer whales, and potential synergistic effects with other environmental stressors.

ecology↗

bioRxiv2021

Loss of SORCS2 is associated with neuronal DNA double-strand breaks

SORCS2 is one of five proteins that constitute the Vps10p-domain receptor family. Members of this family play important roles in cellular processes linked to neuronal survival, differentiation and function. Genetic and functional studies implicate SORCS2 in cognitive function, as well as in neurodegenerative and psychiatric disorders. DNA damage and DNA repair deficits are linked to ageing and neurodegeneration, and transient neuronal DNA double-strand breaks (DSBs) also occur as a result of neuronal activity. Here, we report a novel role for SORCS2 in DSB formation. We show that SorCS2 loss is associated with elevated DSB levels in the mouse dentate gyrus and that knocking out SORCS2 in a human neuronal cell line increased Topoisomerase II{beta}-dependent DSB formation and reduced neuronal viability. Neuronal stimulation had no impact on levels of DNA breaks in vitro, suggesting that the observed differences may not be the result of aberrant neuronal activity in these cells. Our findings are consistent with studies linking the VPS10 receptors and DNA damage to neurodegenerative conditions.

neuroscience↗

bioRxiv2021

Identification of an inhibitory pocket in falcilysin bound by chloroquine provides a new avenue for malaria drug development

Despite their widespread use, our understanding of how many antiparasitic drugs work remains limited. We used mass-spectrometry based cellular thermal shift assay (MS-CETSA) to identify possible protein targets of several malaria drugs and drug candidates. We found that falcilysin (FLN) is a common target for several quinoline drugs including chloroquine and mefloquine, as well as drug candidates MK-4815, MMV000848 and MMV665806. At pH 7.5, these compounds all inhibit FLN proteolytic activity with IC50 values ranging from 1.6 to 67.9 {micro}M. Their interaction with FLN was systematically probed by isothermal titration calorimetry and X-ray crystallography, revealing a shared hydrophobic pocket in the catalytic chamber of the enzyme. Characterization of transgenic cell lines with depleted FLN expression demonstrated statistically significant increases in susceptibility towards chloroquine, mefloquine, MK-4815 and MMV000848. Taken together, our findings point to a multimodal mechanism of action for several commonly used anti-malaria drugs. Importantly, a common allosteric pocket of FLN appears amenable to inhibition, providing a structural basis to guide the development of novel drugs against malaria.

microbiology↗