Biology subjects

Spengler, K.

Publications and source records attributed to Spengler, K..

6 recordsLinked to original sources

bioRxiv2026

Comprehensive study on ferredoxin isoforms in the cyanobacterium Synechocystis sp. PCC 6803

Ferredoxins are central to cellular metabolism by mediating electron flow in energy conversion reactions. The focus of this study was to systematically examine twelve ferredoxin and ferredoxin-like proteins from Synechocystis sp. PCC 6803 to identify their properties, activities, and functions in electron transfer. Using electron paramagnetic resonance spectroscopy, we detected cluster types consistent with major ferredoxin families including plant-type [2Fe-2S], adrenodoxin, thioredoxin, and bacterial-type [4Fe- 4S] ferredoxins. In addition, we found that the ssr3184 ferredoxin-like protein exchanged between a [3Fe-4S] or a [4Fe-4S] cluster, pointing to a possible functional change in response to changes in oxygen or cellular redox poise. Electrochemical measurements demonstrated that these ferredoxins constitute a broad potential window, from -243 mV to -520 mV vs SHE. Investigations on their capacity to support electron-transfer focused on reactions with two major redox hubs: Photosystem I and pyruvate:ferredoxin oxidoreductase and included testing of binding interactions with nitrite reductase. Expression profiling under multiple environmental conditions was also used to predict function and revealed distinct regulatory patterns. Collectively, these findings identified a group of core ferredoxins that directly support photosynthetic electron transfer, and more specialized ones that may serve other functions. In summary, Synechocystis utilizes a suite of ferredoxins to maintain cellular redox homeostasis under dynamic environmental conditions.

biochemistry↗

bioRxiv2025

NanTex enables computational multiplexing and phenotyping of organelles across super-resolution modalities

Super-resolution microscopy (SRM) enables nanoscale visualization of cellular organelles but remains constrained by spectral overlap, labeling requirements, and temporal offsets in multicolor imaging. We present NanTex, a deep learning framework that introduces nanotexture as a universal descriptor of subcellular organization and achieves probabilistic demixing of multiple organelles from single-channel SRM images. Unlike segmentation methods that enforce exclusivity, NanTex preserves overlapping morphologies, enabling faithful reconstruction even in crowded regions. Trained on small curated datasets with augmentation, NanTex generalized across SMLM, MINFLUX, STED, SIM, and live-cell Airyscan, with modality-specific retraining where necessary. Demonstrated on cytoskeletal, endomembrane, and metabolic organelles, NanTex achieved high-fidelity reconstructions and extended uniquely to live-cell imaging, where it eliminated temporal misalignment and enabled quantitative tracking of vesicle-like ER subdomains. Notably, NanTex enables quantitative dynamic readouts directly from single-channel live-cell data, revealing and tracking hidden subdomains in real time without the need for additional labels. Beyond multiplexing, NanTex supported computational phenotyping by distinguishing structurally distinct yet molecularly identical populations, exemplified by nocodazole-induced microtubule depolymerization and its glyoxal-mediated modulation. Together, these results establish nanotexture as a paradigm-shifting descriptor for organelle identity and position NanTex as a modality-agnostic, label-efficient, and live-cell-ready strategy for quantitative nanoscale biology. Significance StatementNanTex reframes multiplexing as texture-based demixing, introducing nanotexture as a universal fingerprint of organelle identity. By enabling quantitative, label-efficient reconstructions across SRM modalities and live-cell phenotyping, including vesicle tracking from single-channel data, NanTex opens a path to studying organelle remodeling and disease progression with unprecedented fidelity across SRM modalities.

biophysics↗

bioRxiv2024

Polyamines sustain epithelial regeneration in aged intestines by modulating protein homeostasis

Aging hampers the regenerative potential of intestinal epithelium across species including humans, yet the underlying causes remain elusive. Here, using proteomic and metabolomic profiling of intestinal tissues together with functional assays, we characterized the temporal dynamics of regeneration following injury induced by 5-fluorouracil, a commonly used chemotherapeutic agent. Comparison of regeneration dynamics in mice of different ages revealed the emergence of a proteostasis stress signature and increased levels of polyamines following injury exclusively in old epithelia. Mechanistically, we show that delayed regeneration is an intrinsic feature of aged epithelial cells that display reduced protein synthesis and accumulation of ubiquitylated proteins. Notably, dietary restriction followed by re-feeding prior to injury increases polyamine pathway activation, enhances protein synthesis, and restores the regenerative capacity of aged intestines. Our findings highlight promising epithelial targets for interventions aimed at tackling the decline in tissue repair mechanisms associated with aging.

molecular biology↗

bioRxiv2021

Pyruvate:ferredoxin oxidoreductase and low abundant ferredoxins support aerobic photomixotrophic growth in cyanobacteria

The decarboxylation of pyruvate is a central reaction in the carbon metabolism of all organisms. Both the pyruvate:ferredoxin oxidoreductase (PFOR) and the pyruvate dehydrogenase (PDH) complex catalyze this reaction. Whereas PFOR reduces ferredoxin, the PDH complex utilizes NAD+. Anaerobes rely on PFOR, which was replaced during evolution by the PDH complex found in aerobes. Cyanobacteria possess both. Our data challenge the view that PFOR is exclusively utilized for fermentation. Instead, we show, that the cyanobacterial PFOR is stable in the presence of oxygen in vitro and is required for optimal photomixotrophic growth under aerobic conditions while the PDH complex is inactivated under the same conditions. We found that cells rely on a general shift from utilizing NAD(H)-dependent to ferredoxin-dependent enzymes under these conditions. The utilization of ferredoxins instead of NAD(H) saves a greater share of the Gibbs free energy, instead of wasting it as heat. This obviously simultaneously decelerates metabolic reactions as they operate closer to their thermodynamic equilibrium. It is common thought that during evolution, ferredoxins were replaced by NAD(P)H due to their higher stability in an oxidizing atmosphere. However, utilization of NAD(P)H could also have been favored due to a higher competitiveness because of an accelerated metabolism.

evolutionary biology↗

bioRxiv2020

Mapping sites of carboxymethyllysine modification on proteins reveals its consequences for proteostasis and cell proliferation

Posttranslational mechanisms play a key role in modifying the abundance and function of cellular proteins. Among these, modification by advanced glycation end products (AGEs) has been shown to accumulate during aging and age-associated diseases but specific protein targets and functional consequences remain largely unexplored. Here, we devised a proteomic strategy to identify specific sites of carboxymethyllysine (CML) modification, one of the most abundant AGEs. We identified over 1000 sites of CML modification in mouse and primary human cells treated with the glycating agent glyoxal. By using quantitative proteomics, we found that protein glycation triggers a proteotoxic response and directly affects the protein degradation machinery. We show that glyoxal induces cell cycle perturbation in primary endothelial cells and that CML modification reduces acetylation of tubulins and impairs microtubule dynamics. Our data demonstrate the relevance of AGE modification for cellular function and pinpoint specific protein networks that might become compromised during aging. HighlightsO_LIA peptide enrichment strategy allows mapping of CML modification in cells and tissues C_LIO_LICML modification competes with ubiquitination or acetylation of lysines C_LIO_LIGlyoxal treatment destabilizes the 26S proteasome C_LIO_LIGlyoxal arrests cell cycle and impairs microtubule dynamics via altering the tubulin code C_LI

biochemistry↗

bioRxiv2018

Untargeted Mass Spectrometry-Based Metabolomics Tracks Molecular Changes in Raw and Processed Foods and Beverages

A major aspect of our daily lives is the need to acquire, store and prepare our food. Storage and preparation can have drastic effects on the compositional chemistry of our foods, but we have a limited understanding of the temporal nature of processes such as storage, spoilage, fermentation and brewing on the chemistry of the foods we eat. Here, we performed a temporal analysis of the chemical changes in foods during common household preparations using untargeted mass spectrometry and novel data analysis approaches. Common treatments of foods such as home fermentation of yogurt, brewing of tea, spoilage of meats and ripening of tomatoes altered the chemical makeup through time, through both chemical and biological processes. For example, brewing tea altered its composition by increasing the diversity of molecules, but this change was halted after 4 min of brewing. The results indicate that this is largely due to differential extraction of the material from the tea and not modification of the molecules during the brewing process. This is in contrast to the preparation of yogurt from milk, spoilage of meat and the ripening of tomatoes where biological transformations directly altered the foods molecular composition. Comprehensive assessment of chemical changes using multivariate statistics showed the varied impacts of the different food treatments, while analysis of individual chemical changes show specific alterations of chemical families in the different food types. The methods developed here represent novel approaches to studying the changes in food chemistry that can reveal global alterations in chemical profiles and specific transformations at the chemical level.\n\nO_LSTHighlightsC_LSTO_LIWe created a reference data set for tomato, milk to yogurt, tea, coffee, turkey and beef.\nC_LIO_LIWe show that normal preparation and handling affects the molecular make-up.\nC_LIO_LITea preparation is largely driven by differential extraction.\nC_LIO_LIFormation of yogurt involves chemical transformations.\nC_LIO_LIThe majority of meat molecules are not altered in 5 days at room temperature.\nC_LI

biochemistry↗