Biology subjects

Toth, G.

Publications and source records attributed to Toth, G..

7 recordsLinked to original sources

bioRxiv2025

Over four months of ethylene production: Unlocking the potential of solid-state photosynthetic cell factories

This study demonstrates the feasibility of employing solid-state photosynthetic cell factories (solid-state PCFs) as a proof-of-concept platform for long-term ethylene production using sodium bicarbonate as the carbon source. Solid-state PCFs were constructed by entrapping Synechocystis sp. PCC 6803 (efe mutant, strain S5), specifically engineered for ethylene biosynthesis, within TEMPO-oxidized cellulose nanofiber (TCNF) matrices. Two distinct formulations were tested: (i) Ca2+-PVA-TCNF, in which TCNF was crosslinked with Ca2+ and polyvinyl alcohol to produce hydrogel films approximately 200 m thick; and (ii) an all-polysaccharide-based Ca2+-MLG-TCNF formulation, in which TCNF was crosslinked with Ca2+ and mixed-linkage glucan. The latter films were fabricated using an osmotic dehydration approach, yielding mechanically robust, fully biodegradable structures with a thickness of approximately 2 mm. The integration of engineered cells with TCNF matrices created a biocatalytic system that improved the distribution of light, nutrients, and substrates to the cells, while facilitating ethylene separation, thereby supporting the fitness of immobilized cells and enhancing their metabolic performance. Using a custom-designed photobiofilm reactor optimized for semi-wet cultivation, the solid-state PCFs sustained ethylene production for over four months, representing the longest reported continuous ethylene production by cyanobacteria to date. Notably, the solid-state PCFs achieved up to a twofold increase in ethylene yield compared to the continuous-flow suspension culture. Importantly, the suspension-based system also represented the first demonstration of four-month ethylene production under continuous-flow operation. In addition, biodegradability assessments confirmed the environmental compatibility of the TCNF-based matrices, with the all-polysaccharide formulation being particularly advantageous due to its exclusively nature-based composition. Together, these results demonstrate the potential of solid-state PCFs as a scalable and sustainable platform for photosynthetic ethylene production.

bioengineering↗

bioRxiv2025

PIA SSN: Parallel Image Acquisition and Spatial Similarity Network for Tandem Mass Spectrometry Imaging

Unambiguous molecular annotations are essential to discern complex local biochemical processes in spatial biology. Here we present a scalable and broadly applicable platform for tandem mass spectrometry imaging (MS2I) that overcomes current limitations in annotation with MSI by integrating Parallel Image Acquisition (PIA) with a novel open-access computational framework, Spatial Similarity Networking (SSN). The PIA employs parallelized acquisition of untargeted MSI and targeted MS2I data using multiple inclusion lists to ensure spatially consistent and structure-resolved imaging of hundreds of molecular species in a single experiment. For molecular annotation, we have developed the SSN that complements PIA by leveraging spatial correlations among product ions through a graph-based analysis framework to enable confident molecular annotation even within highly complex MS2I datasets. Using this integrated approach, we successfully resolved and annotated 134 phospholipid isomers and isobars from mouse brain tissue and suggest confidence levels for annotation for the MSI community. Furthermore, we applied our platform to interrogate cholesterol metabolism in human multiple sclerosis brain tissue, achieving annotation of six novel brain-related oxysterols and revealing spatially correlated oxidation pathways linked to lesion severity. Together, PIA and SSN establish a new framework for large-scale, structure-specific mass spectrometry imaging, with broad implications for spatial metabolomics, lipidomics, and chemical pathology beyond current capabilities.

neuroscience↗

bioRxiv2023

17-Oxime ethers of oxidized ecdysteroid derivatives modulate oxidative stress in human brain endothelial cells and dose-dependently might protect or damage the blood-brain barrier

20-Hydroxyecdysone and several of its oxidized derivatives exert cytoprotective effect in mammals including ans. Inspired by this bioactivity of ecdysteroids, in the current study it was our aim to prepare a set of sidechainmodified derivatives and to evaluate their potential to protect the blood-brain barrier (BBB) from oxidative stress. Six novel ecdysteroids, including an oxime and five oxime ethers, were obtained through regioselective synthesis from a sidechain-cleaved calonysterone derivative 2 and fully characterized by comprehensive NMR techniques revealing their complete 1H and 13C signal assignments. Surprisingly, several compounds sensitized hCMEC/D3 brain microvascular endothelial cells to tert-butyl hydroperoxide (tBHP)-induced oxidative damage as recorded by impedance measurements. Compound 8, containing a benzyloxime ether moiety in its sidechain, was the only one that exerted a protective effect in a higher, 10 M dose, while at lower (10 M - 1 M) doses it promoted tBHP-induced cellular damage. Based on our results, 17-oxime ethers of oxidized ecdysteroids modulate oxidative stress of the BBB in a way that may point towards unexpected toxicity. Further studies are needed to evaluate any possible risk connected to dietary ecdysteroid consumption and CNS pathologies in which BBB damage plays an important role.

pharmacology and toxicology↗

bioRxiv2021

Flv3A facilitates O2 photoreduction and affects H2 photoproduction independently of Flv1A in diazotrophic Anabaena filaments

The model heterocyst-forming filamentous cyanobacterium, Anabaena sp. PCC 7120 (Anabaena) represents multicellular organisms capable of simultaneously performing oxygenic photosynthesis in vegetative cells and the O2-sensitive N2-fixation inside the heterocysts. The flavodiiron proteins (FDPs) have been shown to participate in photoprotection of photosynthesis by driving excess electrons to O2 (Mehler-like reaction). Here, we addressed the physiological relevance of the vegetative cell-specific Flv1A and Flv3A on the bioenergetic processes occurring in diazotrophic Anabaena under variable CO2. We demonstrate that both Flv1A and Flv3A are required for proper induction of the Mehler-like reaction upon a sudden increase in light intensity, which is likely important for the activation of carbon-concentrating mechanisms (CCM) and CO2 fixation. Under ambient CO2 diazotrophic conditions, Flv3A is capable of mediating moderate O2 photoreduction, independently of Flv1A, but in coordination with Flv2 and Flv4. Strikingly, the lack of Flv3A resulted in strong downregulation of the heterocyst-specific uptake hydrogenase, which led to enhanced H2 photoproduction under both oxic and micro-oxic conditions. These results reveal a novel regulatory network between the Mehler-like reaction and the diazotrophic metabolism, which is of great interest for future biotechnological applications.

plant biology↗

bioRxiv2020

Age-Associated Insolubility of Parkin in Human Midbrain is Linked to Redox Balance and Sequestration of Reactive Dopamine Metabolites

The mechanisms by which parkin protects the adult human brain from Parkinson disease remain incompletely understood. We hypothesized that parkin cysteines participate in redox reactions, which are reflected in its posttranslational modifications. We found that in human control brain, including the S. nigra, parkin is largely insoluble after age 40 years, which is linked to its oxidation, e.g., at Cys95 and Cys253. In mice, oxidative stress increases posttranslational modifications at parkin cysteines and reduces its solubility. Oxidation of recombinant parkin also promotes insolubility and aggregate formation, but in parallel, lowers hydrogen peroxide (H2O2). This thiol-based redox activity is diminished by parkin point mutants, e.g., p.C431F and p.G328E. Intriguingly, in parkin-deficient human brain H2O2 concentrations are elevated. In prkn-null mice, H2O2 levels are dysregulated under oxidative stress conditions, such as acutely by MPTP-toxin exposure or chronically due to a second genetic hit. In dopamine toxicity studies, wild-type parkin, but not disease-linked mutants, protects human dopaminergic M17 cells, in part through lowering H2O2. Parkin also neutralizes reactive, electrophilic dopamine metabolites via adduct formation, which occurs foremost at primate-specific Cys95. Further, wild-type but not p.C95A-mutant parkin augments melanin formation. In sections of normal, adult human midbrain, parkin specifically co-localizes with neuromelanin pigment, frequently within LAMP-3/CD63+ lysosomes. We conclude that oxidative modifications of parkin cysteines are associated with protective outcomes, which include the reduction of H2O2, conjugation of reactive dopamine metabolites, sequestration of radicals within insoluble aggregates, and increased melanin formation. The loss of these redox effects may augment oxidative stress in dopamine producing neurons of mutant PRKN allele carriers, thereby contributing to neurodegeneration.

neuroscience↗

bioRxiv2020

Oxidative Modifications of Parkin Underlie its Selective Neuroprotection in Adult Human Brain

The mechanisms by which Parkinson disease-linked parkin confers neuroprotection of human dopamine cells remain elusive. We hypothesized that its cysteines mediate multiple anti-oxidant effects in the midbrain. By studying >60 control specimens, we found that in adult human brain - but not in skeletal muscle- parkin is mostly aggregated and insoluble due to oxidative modifications, such as at C253. In vitro, parkins oxidation directly reduces hydrogen peroxide (H2O2) to water. In parkin-deficient human brain, H2O2 concentrations are elevated. In dopamine toxicity studies, wild-type parkin -but not disease-associated mutants-prevents neural death by lowering H2O2 and sequestering radicals within insoluble aggregates. Parkin conjugates dopamine metabolites at the human-specific residue C95 and augments melanin formation in vitro. Using epitope-mapped antibodies, we found that in adult Substantia nigra neurons parkin localizes to neuromelanin within LAMP-3/CD63-positive lysosomes. We conclude that parkins own oxidation, previously considered a loss-of-function event, underlies three neuroprotective effects in adult midbrain: its cysteines participate in H2O2 reduction, dopamine radical conjugation and the formation of neuromelanin.

neuroscience↗

bioRxiv2019

Novel Small Molecules Targeting the Intrinsically Disordered Structural Ensemble of α-Synuclein Protect Against Diverse α-Synuclein Mediated Dysfunctions

The over-expression and aggregation of -synuclein (Syn) are linked to the onset and pathology of Parkinsons disease. Native monomeric Syn exists in an intrinsically disordered ensemble of interconverting conformations, which has made its therapeutic targeting by small molecules highly challenging. Nonetheless, here we successfully target the monomeric structural ensemble of Syn and thereby identify novel drug-like small molecules that impact multiple pathogenic processes. Using a surface plasmon resonance high-throughput screen, in which monomeric Syn is incubated with microchips arrayed with tethered compounds, we identified novel Syn interacting drug-like compounds. Because these small molecules could impact a variety of Syn forms present in the ensemble, we tested representative hits for impact on multiple Syn malfunctions in vitro and in cells including aggregation and perturbation of vesicular dynamics. We thereby identified a compound that inhibits Syn misfolding and is neuroprotective, multiple compounds that restore phagocytosis impaired by Syn overexpression, and a compound blocking cellular transmission of Syn. Our studies demonstrate that drug-like small molecules that interact with native Syn can impact a variety of its pathological processes. Thus, targeting the intrinsically disordered ensemble of Syn offers a unique approach to the development of small molecule research tools and therapeutics for Parkinsons disease.

neuroscience↗