Biology subjects

Szulc, B.

Publications and source records attributed to Szulc, B..

8 recordsLinked to original sources

bioRxiv2026

Spinal microglia are dispensable for the development of opioid-induced hyperalgesia

Adverse side effects of chronic opioid use, including analgesic tolerance, opioid-induced hyperalgesia, and addiction, are serious clinical challenges for pain management and opioid deprescribing. Microglia have been implicated in the development of these adverse effects, but the extent to which opioids alter microglia and the mechanisms behind opioid effects on microglia are poorly understood. We performed morphological and single-cell transcriptomic analysis on spinal microglia from opioid-withdrawn and saline-treated mice, and found that while morphological changes recapitulated prior reports, transcriptomic changes in these cells were modest. Furthermore, peripherally, but not centrally, restricted opioid administration was sufficient to induce both hyperalgesia and microglial morphological changes in mice. Finally, complete loss of microglia in Csf1r{Delta}{Delta}FIRE mice did not prevent the development of opioid-induced hyperalgesia, analgesic tolerance, and somatic withdrawal symptoms. These data argue against any microglial involvement in the development of these phenomena.

neuroscience↗

bioRxiv2025

Conserved and Lineage-Specific Roles of KEA-Mediated Ion Homeostasis in Chlamydomonas

In Arabidopsis thaliana, seamless plastid gene expression and development depend on finely balanced ion homeostasis across the inner envelope (IE) membrane, maintained by the K/H antiporters AtKEA1/2. To assess whether these functions are retained across mono- and polyplastidic representatives of the green lineage, we studied CrKEA1, the sole IE KEA homolog in the unicellular alga Chlamydomonas reinhardtii. Using CRISPR/Cas9, we generated a Cr-kea1 knockout mutant that exhibits impaired photoautotrophic growth, chloroplast deformation, and photoinhibition. Transcriptomics revealed strong induction of ribosome biogenesis genes and reduced abundance of transcripts associated with cell and plastid division. Further RNA analyses confirmed defects in stromal rRNA maturation of Cr-kea1, paralleling observations from Arabidopsis kea1kea2 mutants. Expression of CrKEA1 in Arabidopsis rescued growth and rRNA maturation in At-kea1kea2, demonstrating functional continuity after the ancient divergence between the two lineages. Cross-species transcriptomic comparisons further revealed that IE KEA loss elicits both shared and species-specific transcriptional responses: PhANG repression was conserved between algae and plants, whereas activation of the chloroplast unfolded protein response (cpUPR) and reduced expression of genes tied to cell-cycle and plastid fission occurred only in Chlamydomonas. Single-cell time-lapse imaging confirmed that Cr-kea1 exhibits an increased frequency of aberrant cytokinesis, unequal division, and division failure. Our findings demonstrate that while IE KEA transporters fulfill conserved roles in maintaining the conditions for plastid gene expression, their integration into broader cellular networks has diverged between unicellular chlorophytes and embryophytes (land plants). This underscores a lineage-dependent tuning of plastid-nucleus communication shaped by organismal complexity and plastid number. One-sentence summaryDisruption of KEA-mediated chloroplast ion homeostasis in Chlamydomonas reinhardtii reveals conserved and lineage-specific control of plastid rRNA processing and cell cycle progression.

plant biology↗

bioRxiv2023

Probing the physiological role of the plastid outer-envelope membrane using the oemiR plasmid collection

Plastids are the site of complex biochemical pathways, most prominently photosynthesis. The organelle evolved through endosymbiosis with a cyanobacterium, which is exemplified by the outer envelope (OE) membrane that harbors more than 40 proteins in Arabidopsis. Their evolutionary conservation indicates high significance for plant cell function. While a few proteins are well-studied as part of the protein translocon complex the majority of OE protein (OEP) functions is unclear. Gaining a deeper functional understanding has been complicated by the lack of observable loss-of-function mutant phenotypes, which is often rooted in functional genetic redundancy. Therefore, we designed OE-specific artificial micro RNAs (oemiRs) capable of downregulating transcripts from several loci simultaneously. We successfully tested oemiR function by performing a proof-of-concept screen for pale and cold-sensitive mutants. An in-depth analysis of pale mutant alleles deficient in the translocon component TOC75 using proteomics provided new insights into putative compensatory import pathways. The cold stress screen not only recapitulated three previously known phenotypes of cold-sensitive mutants, but also identified four mutants of additional oemiR OE loci. Altogether our study revealed a role of the OE to tolerate cold conditions and showcasts the power of the oemiR collection to research the significance of OEPs.

plant biology↗

bioRxiv2022

Hotspots for snake fungal disease across Europe are maintained by host and pathogen identity

1. Infectious diseases are influenced by interactions between host and pathogen, and are rarely homogenous across the landscape. Areas with elevated pathogen prevalence maintain a high force of infection, can facilitate pathogen spread to new regions, and may indicate areas with impacts on host populations. However, isolating the ecological processes that result in increases in infection prevalence and intensity remains a challenge. 2. Here we elucidate the contribution of pathogen clade and host species in disease hotspots of Ophidiomyces ophidiicola, the pathogen that causes snake fungal disease, in 21 species of snakes infected with multiple pathogen strains across 10 countries in Europe. 3. We found isolated areas of disease hotspots in a landscape where infections were otherwise low. O. ophidiicola clade had important effects on transmission, and areas with multiple pathogen clades had higher host infection prevalence. Snake species identity further influenced infection, with most positive detections coming from the Natrix genus. Most species present in the community only experienced increased levels of infection when multiple strains were present. However, one species, N. tessellata, appeared highly susceptible, having increased infection prevalence regardless of pathogen strain, indicating that this species may be important in pathogen maintenance. 4. Our results suggest that both host and pathogen identity are essential components contributing to increased pathogen prevalence. More broadly, our findings indicate that coevolutionary relationships between hosts and pathogens may be key mechanisms explaining variation in landscape patterns of disease.

ecology↗

bioRxiv2021

The solute carrier MFSD1 decreases β1 integrins activation status and thus tumor metastasis

Solute carriers are increasingly recognized as participating in a plethora of pathologies, including cancer. We describe here the involvement of the orphan solute carrier MFSD1 in the regulation of tumor cell migration. Loss of MFSD1 enabled higher levels of metastasis in a mouse model. We identified an increased migratory potential in MFSD1-/- tumor cells which was mediated by increased focal adhesion turn-over, reduced stability of mature inactive {beta}1 integrin, and the resulting increased integrin activation index. We show that MFSD1 promoted recycling to the cell surface of endocytosed inactive {beta}1 integrin and thereby protected {beta}1 integrin from proteolytic degradation; this led to dampening of the integrin activation index. Furthermore, down-regulation of MFSD1 expression was observed during early steps of tumorigenesis and higher MFSD1 expression levels correlate with a better cancer patient prognosis. In sum, we describe a requirement for endolysosomal MFSD1 in efficient {beta}1 integrin recycling to suppress tumor spread.

cancer biology↗

bioRxiv2021

Biophysical and proteomic analyses suggest functions of Pseudomonas syringae pv tomato DC3000 extracellular vesicles in bacterial growth during plant infection

Vesiculation is a process employed by Gram-negative bacteria to release extracellular vesicles (EVs) into the environment. Bacterial EVs contain molecular cargo from the donor bacterium and play important roles in bacterial survival and growth. Here, we describe EV production in plant-pathogenic Pseudomonas syringae pv. tomato DC3000 (Pto DC3000), the causal agent of bacterial speck disease. Cultured Pto DC3000 exhibited EV structures both on the cell surface and in the vicinity of bacterial cells, observed as outer membrane vesicle (OMV) release. We used in-solution trypsin digestion coupled to mass spectrometry to identify 369 proteins enriched in EVs recovered from cultured Pto DC3000. The predicted localization profile of EV proteins supports the production of EVs also in the form of outer-inner-membrane vesicles (OIMVs). EV production varied slightly between bacterial lifestyles and also occurred in planta. The potential contribution of EVs to Pto DC3000 plant infection was assessed using plant treatments and bioinformatic analysis of the EV-enriched proteins. While these results identify immunogenic activities of the EVs, they also point at roles for EVs in bacterial defences and nutrient acquisition by Pto DC3000.

plant biology↗

bioRxiv2021

Missing the sweet spot: one of the two N-glycans on human Gb3/CD77 synthase curtails its activity

N-glycosylation is a ubiquitous posttranslational modification that may influence folding, subcellular localization, secretion, solubility and oligomerization of proteins. In this study, we examined the effects of N-glycans on the activity of human Gb3/CD77 synthase, which catalyzes the synthesis of glycosphingolipids with terminal Gal1[->]4Gal (Gb3 and the P1 antigen) and Gal1[->]4GalNAc disaccharides (the NOR antigen). The human Gb3/CD77 synthase contains two occupied N-glycosylation sites at positions N121 and N203. Intriguingly, we found that while the N-glycan at N203 is essential for activity and correct subcellular localization, the N-glycan at N121 is dispensable and its absence did not reduce, but, surprisingly, even increased the activity of the enzyme. The fully N-glycosylated human Gb3/CD77 synthase and its glycoform missing the N121 glycan correctly localized in the Golgi, whereas a glycoform without the N203 site partially mislocalized in the endoplasmic reticulum. A double mutein missing both N-glycans was inactive and accumulated in the endoplasmic reticulum. Our results suggest that the decreased specific activity of human Gb3/CD77 synthase glycovariants results from their improper subcellular localization and, to a smaller degree, a decrease in enzyme solubility. Taken together, our findings show that the two N-glycans of human Gb3/CD77 synthase have opposing effects on its properties, revealing a dual nature of N-glycosylation and potentially a novel regulatory mechanism controlling the biological activity of proteins.

biochemistry↗

bioRxiv2018

Correct CYFIP1 dosage is essential for synaptic inhibition and the excitatory/inhibitory balance.

Altered excitatory/inhibitory balance is implicated in neuropsychiatric disorders but the genetic aetiology of this is still poorly understood. Copy number variations in CYFIP1 are associated with autism, schizophrenia and intellectual disability but the role of CYFIP1 in regulating synaptic inhibition or excitatory/inhibitory balance remains unclear. We show, CYFIP1, and its paralogue CYFIP2, are enriched at inhibitory postsynaptic sites. While upregulation of CYFIP1 or CYFIP2 increased excitatory synapse number and the frequency of miniature excitatory postsynaptic currents (mEPSCs), it had the opposite effect at inhibitory synapses, decreasing their size and the amplitude of miniature inhibitory postsynaptic currents (mIPSCs). Contrary to CYFIP1 upregulation, its loss in vivo, upon conditional knockout in neocortical principal cells, increased expression of postsynaptic GABAA receptor {beta}2/3-subunits and neuroligin 3 and enhanced synaptic inhibition. Thus, CYFIP1 dosage can bi-directionally impact inhibitory synaptic structure and function, potentially leading to altered excitatory/inhibitory balance and circuit dysfunction in CYFIP1-associated neurodevelopmental disorders.

neuroscience↗