Biology subjects

Ecsedi, P.

Publications and source records attributed to Ecsedi, P..

3 recordsLinked to original sources

bioRxiv2026

SSB1 links stress granule regulation to cellular stress responses and renal ischemia-reperfusion injury

Mammalian single-stranded DNA binding protein 1 (SSB1) has been established as an essential component of genome stability in both human cells and mice. Moreover, SSB1 was recently implicated in cytoplasmic stress response by its involvement in Ras GTPase-activating protein-binding protein 1 (G3BP1)-containing cytoplasmic stress granules (SGs) upon various forms of stress. Here, we generated and analyzed human cellular knockout and rodent ischemia-reperfusion (I/R) models to define SSB1s roles in cytoplasmic stress response. Analysis of wild-type as well as SSB1 and G3BP1 knockout human retinal pigment epithelial (RPE-1) cells shows stress-specific incorporation of SSB1 into SGs and a negative regulator role for SSB1 in SG dynamics under sublethal stress conditions. We find that SSB1 knockout measurably increases cellular sensitivity to oxidative stress but does not alter cell proliferation following mild acute stress. Moreover, we detect SSB1 efflux from the nucleus upon stress that is dependent upon the presence of G3BP1 in a stress-specific manner. In addition, using mouse and rat models we observe significant upregulation and robust cytoplasmic granulation of SSB1 upon renal ischemia-reperfusion stress, establishing SSB1s involvement in complex organismal stress response in vivo. Together, our data demonstrate active involvement of SSB1 in cytoplasmic response to cellular stress and acute kidney injury, with implications for targeting stress response functions in cancerous versus non-cancerous contexts. HIGHLIGHTSO_LISSB1 is incorporated into cytoplasmic stress granules and negatively regulates stress granule assembly under sublethal stress conditions C_LIO_LISSB1 shows stress- and G3BP1-dependent nuclear efflux C_LIO_LISSB1 is upregulated and undergoes apical granulation in renal epithelial cells during renal ischemia-reperfusion injury C_LI

cell biology↗

bioRxiv2025

Phase transition drives bacterial single-stranded DNA binding (SSB) protein mobilization during stress response and metabolic adaptation

Single-stranded DNA-binding proteins (SSBs) are ubiquitous factors of genome metabolism, recently recognized for their ability to undergo liquid-liquid phase separation (LLPS). While Escherichia coli SSB (EcSSB) has emerged as a model for bacterial LLPS in vitro, its phase behavior and functional dynamics in vivo have remained largely unexplored. Here, we define the subcellular organization of EcSSB under diverse physiological and stress conditions using super-resolution microscopy coupled with newly developed image analysis tools. We show that EcSSB forms dynamic intracellular assemblies during exponential growth, which partially dissolve in response to DNA damage, oxidative stress, antibiotic exposure, and metabolic adaptation. In contrast, these dynamic reorganizations are attenuated in stationary phase cells. Moreover, we show that EcSSB foci exhibit limited overlap with nucleoid regions under stress-free conditions, whereas stress induction is accompanied by increased DNA association. These in vivo observations are consistent with stress- and growth-phase dependent modulation of EcSSB organization and together with biophysical characterization of EcSSB condensation in vitro suggest a role for LLPS-based dynamic storage and mobilization in response to physiological demands. Our work provides a quantitative framework for analyzing the cellular organization of bacterial proteins and the spatial regulation of genome maintenance factors in changing environments. This knowledge may also support future strategies targeting SSB organization pathways for antimicrobial development.

biochemistry↗

bioRxiv2019

High throughput competitive fluorescence polarization assay reveals functionalredundancy in the S100 protein family

The calcium-binding, vertebrate-specific S100 protein family consists of 20 paralogs in humans (referred as the S100ome), with several clinically important members. To assess their interactome, high-throughput, systematic analysis is indispensable, which allows one to get not only qualitative but quantitative insight into their protein-protein interactions (PPIs). We have chosen an unbiased assay, fluorescence polarization (FP) that revealed a partial functional redundancy when the complete S100ome (n=20) was tested against numerous model partners (n=13). Based on their specificity, the S100ome can be grouped into two distinct classes: promiscuous and orphan. In the first group, members bound to several ligands (>4-5) with comparable high affinity, while in the second one, the paralogs bound only one partner weakly, or no ligand was identified (orphan). Our results demonstrate that in vitro FP assays are highly suitable for quantitative ligand binding studies of selected protein families. Moreover, we provide evidence that PPI-based phenotypic characterization can complement the information obtained from the sequence-based phylogenetic analysis of the S100ome, an evolutionary young protein family.\n\nAuthor summaryFunctional similarity among a protein family can be essential in order to understand proteomic data, to find biomarkers, or in inhibitor design. Proteins with similar functions can compensate the loss-of-function of the others, their expression can co-vary under pathological conditions, and simultaneous targeting can lead to better results in the clinics. To investigate this property one can use sequence-based approaches. However, this path can be difficult. In the case of the vertebrate specific, evolutionary young, S100 family, phylogenetic approaches lead to ambiguous results. To overcome this problem, we applied a high-throughput biochemical approach to experimentally measure the binding affinities of a large number of S100 interactions. We performed unbiased fluorescence polarization assay, involving the complete human S100ome (20 paralogs) and 13 known interaction partners. We used this measured 20x13 (260) protein-protein interaction array to reveal the functional relationships within the family. Our work provide a general framework for studies focusing on phenotype-based domain classification.

biochemistry↗