Biology subjects

Manetsch, R.

Publications and source records attributed to Manetsch, R..

6 recordsLinked to original sources

bioRxiv2026

GAT1508, a selective neuronal GIRK1/2 activator, exhibits superior antiepileptic efficacy and synergizes with cannabidiol

G protein-gated inwardly rectifying potassium (GIRK; Kir3) channels are key regulators of neuronal excitability and represent promising therapeutic targets for epilepsy. Here, we characterize GAT1508, a urea-based small-molecule activator selectively targeting neuronal GIRK1/2 heterotetramers, and compare its efficacy with previously described urea compounds ML297 and GiGA1. In a pentylenetetrazole (PTZ)-induced seizure model, GAT1508 demonstrated robust antiseizure activity, outperforming both ML297 and GiGA1 and achieving efficacy comparable to valproic acid. Electrophysiological studies using two-electrode voltage clamp in Xenopus oocytes revealed that GAT1508, unlike ML297 and GiGA1, selectively activates GIRK1/2 channels without significant activation of cardiac GIRK1/4 channels, suggesting reduced risk of cardiovascular side effects. Structural and computational analyses indicate that enhanced stabilization of GAT1508 compared to ML297 within the GIRK1/2 binding pocket promotes both ion permeation and channel gating through coordinated interactions with key residues. Furthermore, GAT1508, like the two other urea drugs, exhibited synergistic activation of GIRK channels when combined with G{beta}{gamma}-mediated pathways and significantly potentiated the antiseizure effects of cannabidiol (CBD) in both hippocampal slice recordings and in vivo seizure models. These findings establish GAT1508 as a potent and selective GIRK1/2 activator and support a novel combination therapeutic strategy for epilepsy based on convergent GIRK channel modulation.

pharmacology and toxicology↗

bioRxiv2026

Legacy 4(1H)-quinolone scaffolds activity against acute and chronic Toxoplasma gondii infection

Toxoplasma gondii is a protozoan parasite capable of infecting most warm-blooded animals, including humans, and can cause severe disease in immunocompromised individuals and the developing fetus. Current treatments for toxoplasmosis are effective only against the acute stage of infection and have limited or no activity against the latent bradyzoite stage found within tissue cysts. The mitochondrion of T. gondii is a validated drug target, and the clinically used drug atovaquone acts by inhibiting the mitochondrial electron transport chain (ETC) at the coenzyme Q:cytochrome c oxidoreductase (bc1 complex). In this study, we evaluate two legacy 4(1H)-quinolones: ICI 56,780 and WR 243246, previously shown to inhibit the Plasmodium falciparum bc1 complex, for their efficacy against T. gondii. Both compounds inhibit tachyzoite growth with low-nanomolar EC values and disrupt parasite mitochondrial function by blocking cytochrome c reduction and collapsing the mitochondrial membrane potential. Notably, ICI 56,780 protects mice from lethal infection with type I RH tachyzoites. Importantly, ICI 56,780 also exhibits potent activity against chronic-stage parasites, reducing cyst size and bradyzoite viability in vitro and showing low-nanomolar EC values against in vivo-derived bradyzoites. In mice chronically infected with T. gondii, treatment with ICI 56,780 significantly decreases brain cyst burden. Although these 4(1H)-quinolones display some pharmacokinetic limitations, our findings highlight their potential as promising chemotypes active against both acute and chronic stages of T. gondii and provide a framework for future medicinal chemistry efforts to improve drug-like properties while preserving or enhancing anti-bradyzoite activity.

microbiology↗

bioRxiv2021

Protein crosslinking as a therapeutic strategy for SOD1-related ALS

Mutations in the gene encoding Cu-Zn superoxide dismutase 1 (SOD1) cause a subset of familial amyotrophic lateral sclerosis (fALS). One effect of these mutations is that SOD1, which is normally a stable dimer, dissociates into toxic monomers. Considerable research efforts have been devoted to developing compounds that stabilize the dimer of fALS SOD1 variants, but these have not yet resulted in an approved drug. We demonstrate that a cyclic thiosulfinate cross-linker can stabilize prevalent disease-causing SOD1 variants. The degree of stabilization afforded by cyclic thiosulfinates (up to 24 {degrees}C) is unprecedented. We show this compound works rapidly in vivo with a half-life of ~3 days. The efficacy, low toxicity, and pharmacodynamics of cross-linker mediated stabilization make it a promising therapeutic approach for SOD1-related fALS. Significance statementCyclic thiosulfinate S-XL6 enables the kinetic stabilization of ALS-associated SOD1 variants, in vivo.

neuroscience↗

bioRxiv2021

Profiling the in vitro and in vivo activity of streptothricin-F against carbapenem-resistant Enterobacterales: a historic scaffold with a novel mechanism of action

Streptothricins are components of the natural product, nourseothricin; each containing identical streptolidine and gulosamine aminosugar moieties attached to varying numbers of linked {beta}-lysines. Nourseothricin was discovered by Waksman and colleagues in the early 1940s, generating intense interest because of excellent Gram-negative activity. However, the natural product mixture was associated with toxicity, and subsequent exploration was limited. Here, we establish the activity spectrum of nourseothricin and its main components, streptothricin-F (S-F, one lysine) and streptothricin D (S-D, three lysines), purified to homogeneity, against highly drug-resistant, carbapenem-resistant Enterobacterales (CRE). The MIC50 and MIC90 for S-F and S-D were 2 and 4 {micro}M, and 0.25 and 0.5 {micro}M, respectively. S-F and nourseothricin showed rapid, bactericidal activity. S-F and S-D both showed approximately 40-fold greater selectivity for prokaryotic than eukaryotic ribosomes in in vitro translation assays. There was >10-fold in vitro selectivity of S-F compared with S-D on LLC-PK1 and J774 cell lines. In vivo, delayed renal toxicity occurred at >10-fold higher doses of S-F compared with S-D. Substantial treatment effect of S-F in the murine thigh model was observed against the otherwise pandrug-resistant, NDM-1-expressing Klebsiella pneumoniae Nevada strain at dosing levels without observable or minimal toxicity. Resistance mutations obtained in single ribosomal operon E. coli identify novel interactions with 16S rRNA helix 34, i.e., C1504A and A1196G/C conferred high level resistance to nourseothricin. Based on promising, unique activity, we suggest that the streptothricin scaffold deserves further pre-clinical exploration as a potential therapeutic for the treatment of CRE and potentially other multidrug-resistant, gram-negative pathogens. IMPORTANCEStreptothricins are a historic class of antibiotics discovered by Waksman and colleagues in the 1940s. Toxicities associated with the streptothricin natural product mixture, also known as nourseothricin, discouraged further development. However, we found that a component of nourseothricin, streptothricin-F, retained potent activity against contemporary carbapenem-resistant Enterobacterales with significant selectivity in in vitro and in vivo assays. This included demonstration of rapid bactericidal activity in vitro and substantial therapeutic effect in the murine thigh model against a pandrug-resistant Klebsiella pneumoniae isolate at non-toxic concentrations. Through resistance mutation analysis, we identified helix 34 of 16S rRNA in the prokaryotic ribosome, and specifically bases C1054 and A1196, as critical for streptothricins activity. The mechanism of action is distinct from other known translation inhibitors. Based on promising and unique activity, we believe the streptothricin scaffold deserves further pre-clinical exploration as a potential therapeutic for the treatment of CRE and potentially other multidrug-resistant, Gram-negative pathogens.

microbiology↗

bioRxiv2020

Naegleria fowleri: protein structures to facilitate drug discovery for the deadly, pathogenic free-living amoeba

Naegleria fowleri is a pathogenic, thermophilic, free-living amoeba which causes primary amebic meningoencephalitis (PAM). Penetrating the olfactory mucosa, the brain-eating amoeba travels along the olfactory nerves, burrowing through the cribriform plate to its destination: the brains frontal lobes. The amoeba thrives in warm, freshwater environments, with peak infection rates in the summer months and has a mortality rate of approximately 97%. A major contributor to the pathogens high mortality is the lack of sensitivity of N. fowleri to current drug therapies, even in the face of combination-drug therapy. To enable rational drug discovery and design efforts we have pursued protein production and crystallography-based structure determination efforts for likely drug targets from N. fowleri. N. fowleri genes were selected if they had homology to drug targets listed in Drug Bank or were nominated by primary investigators engaged in N. fowleri research. In 2017, 178 N. fowleri protein targets were queued to the Seattle Structural Genomics Center of Infectious Disease (SSGCID) pipeline, and to date 89 soluble recombinant proteins and 19 unique target structures have been produced. Many of the new protein structures are potential drug targets and contain structural differences compared to their human homologs, which could allow for the development of pathogen-specific inhibitors. Five of the structures were analyzed in more detail, and four of five show promise that selective inhibitors of the active site could be found. The 19 solved crystal structures build a foundation for future work in combating this devastating disease by encouraging further investigation to stimulate drug discovery for this neglected pathogen.

molecular biology↗

bioRxiv2017

Mitochondrial heteroplasmy is responsible for Atovaquone drug resistance in Plasmodium falciparum

Malaria is the most significant parasitic disease affecting humans, with 212 million cases and 429,000 deaths in 2 0151, and resistance to existing drugs endangers the global malaria elimination campaign. Atovaquone (ATO) is a safe and potent antimalarial drug that acts on cytochrome b (cyt. b) of the mitochondrial electron transport chain (mtETC) in Plasmodium falciparum, yet treatment failures result in resistance-conferring SNPs in cyt. b. Herein we report that rather than the expected de novo selection of resistance, previously unknown mitochondrial diversity is the genetic mechanism responsible for resistance to ATO, and potentially other cyt. b targeted drugs. We found that P. falciparum harbors cryptic cyt. b. Y268S alleles in the multicopy ([~]22 copies) mitochondrial genome prior to drug treatment, a phenomenon known as mitochondrial heteroplasmy. Parasites with cryptic Y268S alleles readily evolve into highly resistant parasites with >95% Y268S copies under in vitro ATO selection. Further we uncovered high mitochondrial diversity in a global collection of 1279 genomes in which heteroplasmic polymorphisms were >3-fold more prevalent than homoplasmic SNPs. Moreover, significantly higher mitochondrial genome copy number was found in Asia (e.g., Cambodia) versus Africa (e.g., Ghana). Similarly, ATO drug selections in vitro induced >3-fold mitochondrial copy number increases in ATO resistant lines. Hidden mitochondrial diversity is a previously unknown mechanism of antimalarial drug resistance and characterization of mitochondrial heteroplasmy will be of paramount importance in combatting resistance to antimalarials targeting the electron transport chain.

cell biology↗