Biology subjects

Turek, M.

Publications and source records attributed to Turek, M..

7 recordsLinked to original sources

bioRxiv2026

In vivo analysis of UNC-23 reveals residues critical for BAG2 domain function

BAG2 is a co-chaperone that regulates Hsp70 activity and plays key roles in protein homeostasis and disease, yet the residue-level determinants of its stability and function remain poorly defined. Here, we use the Caenorhabditis elegans BAG2 homolog UNC-23 as an in vivo model to dissect these mechanisms. A forward genetic screen identified a missense mutation, UNC-23C403Y, that causes muscle deterioration without affecting developmental timing. Sequence and structural analyses revealed that C403 is highly evolutionarily conserved and located within a structurally conserved BAG domain. Furthermore, to systematically identify residues critical for protein stability, we combined evolutionary conservation with in silico stability predictions and tested selected substitutions in vivo. Despite strong conservation and predicted destabilization, most generated mutations were phenotypically silent, with only UNC-23F416A producing a severe defect, revealing the limited predictive power of current approaches and a high tolerance of the BAG domain to perturbations. Comparative structural analysis further showed that, although the BAG domain architecture is conserved, its core stabilization relies on distinct interactions in invertebrates and vertebrates. Together, our results identify and refine residues contributing to UNC-23/BAG2 function, improving the current understanding of the BAG domain, and demonstrate that its architecture is maintained through distinct stabilizing interactions across evolution.

cell biology↗

bioRxiv2025

Mitochondrial redox homeostasis links organellar stress surveillance to germline and somatic integrity in Caenorhabditis elegans

Mitochondrial redox homeostasis is essential for cellular metabolism and organismal development. To investigate the consequences of disrupting redox homeostasis in this organelle in a metazoan organism, we generated a double mutant lacking mitochondrial glutathione reductase (gsr-1a) and thioredoxin reductase (trxr-2) genes in Caenorhabditis elegans. While gsr-1a or trxr-2 single mutants are phenotypically normal, double gsr-1a trxr-2 mutants displayed small body size, gonadal migration defects, reduced brood size, and prolonged egg-laying period, without developmental delay or lethality. Transcriptomic analysis revealed strong induction of ATFS-1-dependent stress and detoxification genes. Consistent with this, gsr-1a trxr-2 worms exhibited constitutive ATFS-1 nuclear localization and robust Phsp-6::gfp expression. Triple gsr-1a trxr-2; atfs-1 mutants were nonviable, demonstrating that unfolded protein response (UPRmt) activation is essential under mitochondrial redox stress. Despite the induction of a stress response at the transcriptional level, gsr-1a trxr-2 double mutants were not more resistant to oxidative or pathogen stressors. Moreover, these mutants maintained normal respiration, ATP and ROS production while displaying altered mitochondrial morphology in a tissue-specific manner, independent of mitophagy genes but dependent on mitochondrial fission or fusion machinery. Functionally, gsr-1a trxr-2 mutants showed impaired motility, reduced calcium uptake upon carbachol stimulation, enhanced hypodermal wound repair, and decreased fertilization efficiency associated with lower muscle exopher production. Overall, our data show that simultaneous loss of mitochondrial GSR-1a and TRXR-2 compromises growth, fertility and muscle performance and triggers a constitutive ATFS-1-dependent UPRmt that sustains viability revealing mitochondrial redox control as a core determinant of organismal proteostasis. HighlightsO_LIgsr-1a or trxr-2 single mutants have no overt phenotypes. C_LIO_LIgsr-1a trxr-2 double mutants are viable but show small size, gonad migration defects and reduced progeny. C_LIO_LILoss of both reductases in mitochondria triggers a constitutive ATFS-1-dependent UPRmt. C_LIO_LIATFS-1 is essential for gsr-1a trxr-2 worms survival. C_LIO_LIgsr-1a trxr-2 animals remodel mitochondrial morphology in a tissue-specific manner. C_LIO_LIgsr-1a trxr-2 double mutants exhibit impaired muscle and sperm function but enhanced wound healing. C_LI Graphical abstract (to be incorporated)

genetics↗

bioRxiv2024

Pathogen threat proximity shapes host extracellular vesicle production in pre-infection response

Extracellular vesicles (EVs) play a crucial role in immune responses, yet it remains unclear whether pathogen metabolites alone can stimulate EV production prior to infection. Using Caenorhabditis elegans, we investigate this question through the lens of exophers - large, evolutionarily conserved EVs known to enhance proteostasis, extend lifespan, and improve reproductive fitness. Our study uncovers distinct regulatory mechanisms driving EV production in response to pathogen-derived volatile metabolites and non-volatile secretome, providing insights into host-pathogen signaling before physical interaction. We reveal a sophisticated network that adjusts EV production based on pathogen proximity: non-volatile secretome (including tripeptide Ile-Pro-Pro), signaling an immediate threat, activate immune-dependent EV pathways, while volatile metabolites, forewarning potential danger, initiate immunity-independent exopher production. Both responses rely on sensory neurons, with ASK, ADL, and AWC neurons playing central roles in each, and additional input from ASI, AWB, and ASH neurons specifically enhancing non-volatile secretome-induced EV production. Downstream signal integration is mediated by a circuit involving the RMG hub and AIB/AIA interneurons, with the AIB-specific NPR-9 receptor playing a critical role. Molecularly, we identified multiple GPCRs, including SRI-19, SRI-36/39, and SRR-6, as crucial for the non-volatile response, and revealed that SRR-6 functions in the intestine to regulate muscle exopher production, demonstrating a novel gut-muscle signaling axis. Notably, exposure to volatile pathogen metabolites significantly boosts offspring fitness during infection in SRI-19-dependent manner, albeit at the cost of maternal survival when conditions are being harsher. Thus, our study shows that C. elegans distinguishes pathogen proximity through compound types, activating EV-dependent physiological responses tailored to either immediate or anticipated threats to optimize survival across generations.

physiology↗

bioRxiv2022

Pheromone-dependent olfaction bidirectionally regulates muscle extracellular vesicles formation

Extracellular vesicles (EVs) are involved in multiple biological processes; however, there is limited knowledge of the influence of environmental factors or other individuals in a population on EV-regulated systems. The largest evolutionarily conserved EVs, exophers, are a component of the C. elegans maternal somatic tissue resource management system induced by embryos developing in utero, and thus progeny of individuals with active exopher biogenesis (exophergenesis) appear to be privileged. Using this model, we investigated the inter-tissue and social regulatory mechanisms of exophergenesis. We found that the predominant male pheromone, ascr#10, increases exopher production in hermaphrodites via the G-protein-coupled receptor STR-173 in the ASK sensory neurons. In contrast, pheromones from other hermaphrodites in the population temper exophergenesis. Within the hermaphrodite, an increase in embryo accumulation drives pro-exopher signals, and the internal sensory neurons AQR, PQR, and URX play a central role in modulating exopher levels. This intricate process is regulated partly via the neuropeptides FLP-8 and FLP-21, which originate from the URX and AQR/PQR/URX neurons, respectively. Our results reveal a regulatory network integrating internal and external cues, including control of somatic EVs production by the nervous system in response to social signals.

physiology↗

bioRxiv2021

Cytosolic aggregation of mitochondrial proteins disrupts cellular homeostasis by stimulating other proteins aggregation

Mitochondria are organelles with their own genomes, but they rely on the import of nuclear-encoded proteins that are translated by cytosolic ribosomes. Therefore, it is important to understand whether failures in the mitochondrial uptake of these nuclear-encoded proteins can cause proteotoxic stress and identify response mechanisms that may counteract it. Here, we report that upon impairments in mitochondrial protein import, high-risk precursor and immature forms of mitochondrial proteins form aberrant deposits in the cytosol. These deposits then cause further cytosolic accumulation and consequently aggregation of other mitochondrial proteins and disease-related proteins, including -synuclein and amyloid {beta}. This aggregation triggers a cytosolic protein homeostasis imbalance that is accompanied by specific molecular chaperone responses at both the transcriptomic and protein levels. Altogether, our results provide evidence that mitochondrial dysfunction, specifically protein import defects, contributes to impairments in protein homeostasis, thus revealing a possible molecular mechanism by which mitochondria are involved in neurodegenerative diseases.

molecular biology↗

bioRxiv2020

Nutritional status and fecundity are synchronised by muscular exopheresis

Organismal functionality and reproduction depend on metabolic rewiring and balanced energy resources. However, the crosstalk between organismal homeostasis and fecundity, and the associated paracrine signaling mechanisms are still poorly understood. Using the Caenorhabditis elegans we discovered that large extracellular vesicles termed exophers, attributed in neurons and cardiomyocytes to the removal of damaged subcellular components, are released by body wall muscles to support embryonic growth. We found that exopher formation (exopheresis) is a non-cell autonomous process regulated by egg formation in the uterus. Our data suggest that exophers serve as transporters for muscle-generated yolk proteins used for nourishing and improving the growth rate of the next generation. We propose that the primary role of muscular exopheresis is to stimulate the reproductive capacity, thereby influencing the adaptation of worm populations to the current environmental conditions.

physiology↗

bioRxiv2019

A tripartite flip-flop sleep circuit switches sleep states

Sleep-active neurons depolarize during sleep to suppress wakefulness circuits. Wake-active wake-promoting neurons in turn shut down sleep-active neurons, thus forming a bipartite flip-flop switch. However, how sleep is switched on is unclear because it is not known how wakefulness is translated into sleep-active neuron depolarization when the system is set to sleep. Using optogenetics in C. elegans, we solved the presynaptic circuit for depolarization of the sleep-active RIS neuron during developmentally-regulated sleep, also known as lethargus. Surprisingly, we found that RIS activation requires neurons that have known roles in wakefulness and locomotion behavior. The RIM interneurons, which are active during and can induce reverse locomotion, play a complex role and can act as inhibitors of RIS when they are strongly depolarized and as activators of RIS when they are modestly depolarized. The PVC command interneurons, which are known to promote forward locomotion during wakefulness, act as major activators of RIS. The properties of these locomotion neurons are modulated during lethargus. The RIMs become less excitable. The PVCs become resistant to inhibition and have an increased capacity to activate RIS. Separate activation of neither the PVCs nor the RIMs appears to be sufficient for sleep induction; instead, our data suggests that they act in concert to activate RIS. Forward and reverse circuit activity is normally mutually exclusive. Our data suggest that RIS may be activated at the transition between forward and reverse locomotion states, perhaps when both reverse (including RIM) and forward (PVC) circuit activity overlaps. While RIS is not strongly activated outside of lethargus, altered activity of the locomotion interneurons during lethargus favors strong RIS activation and thus sleep. The control of sleep-active neurons by locomotion circuits suggests that sleep may have evolved from locomotion quiescence. The flip-flop sleep switch in C. elegans thus requires an additional component, wake-active sleep-promoting neurons that translate wakefulness into the depolarization of a sleep-active neuron when the worm is sleepy. Wake-active sleep-promoting circuits may also be required for sleep state switching in other animals including in mammals.

neuroscience↗