Cell Stress and Chaperones

Hibernation consists of bouts of torpor, characterized by profound decreases in metabolism and body temperature (Tb), alternated with periods of euthermia called interbout arousals, during which normal metabolism and Tb resume. Seasonal hibernators accumulate DNA strand breaks during torpor, which are repaired during arousal. Here, we assess dynamics of DNA damage and repair during serial daily torpor in mice induced by 30% calorie restriction (CR) and investigate the effects of metabolic challenge on DNA repair. Serial daily torpor induced by CR in C57/BL6J mice of both sexes housed at 20{degrees}C lasts 6-12 hours. Like seasonal hibernators, DNA damage increases in CR-induced torpor and is repaired in the subsequent euthermic period, as evidenced by comet assay and {gamma}H2AX accumulation. To metabolically challenge animals, ambient temperature (Ta) was lowered to 4{degrees}C, since torpid mice defend a Tb of around 20{degrees}C or higher. Despite inducing a significant metabolic challenge, housing of torpid mice at 4{degrees}C does not increase DNA damage compared to 20{degrees}C housing. However, reducing Ta to 4{degrees}C during euthermia inhibits DNA repair. Interestingly, p21 levels increase in mice exposed to 4{degrees}C, indicating cell-cycle inhibition during exposure to 4{degrees}C. Thus, 30% CR induces daily cycles of torpor-induced DNA damage and euthermia-associated DNA repair in mice, and exposure to a Ta of 4{degrees}C during arousal inhibits DNA repair mounting a cell cycle inhibition response. Thus, the torpor-arousal cycle may be a contributing factor to the lifespan extension benefits of CR in mice, promoting genomic integrity and thereby cellular and tissue health.

Heatstroke is a life-threatening condition in which heat-shock and unfolded-protein responses are strongly activated but fail to prevent proteostasis disruption and severe cellular injury. Whether post-transcriptional regulation contributes to this mismatch remains unknown. We integrated small RNA sequencing with mRNA profiling in peripheral blood mononuclear cells from patients with classical heatstroke and matched heat-exposed controls recruited during the Hajj pilgrimage. mRNA profiling was performed in 19 cases and 19 controls, and miRNA sequencing in 17 cases and 16 controls from the same cohort. Differentially expressed miRNAs were integrated with 4,462 differentially expressed mRNAs using high-confidence inverse-expression miRNA-mRNA pairs. Twenty-six miRNAs mapped to 376 mRNA targets, forming 414 regulatory pairs and two opposing programmes. Programme A, comprising 16 downregulated miRNAs, was associated with activation of PI3K-mTOR, NRF2 oxidative stress and HIF-1 signalling, consistent with stress-survival signalling. Programme B, comprising 10 upregulated miRNAs, was associated with suppression of stress-granule components and fatty-acid {beta}-oxidation genes, consistent with impaired protein quality control and reduced metabolic flexibility. miR-92a-3p emerged as a central regulatory node, and its target PIK3R3 connected 9 of the 10 enriched pathways. These findings suggest a post-transcriptional regulatory layer that could contribute to the limited protection afforded by activated stress defences in human heatstroke.

Cold environments pose substantial metabolic challenges to ectothermic organisms. In amphibians, such as the African clawed frog (Xenopus laevis), exposure to cold temperatures induces pronounced hyperglycemia; however, the molecular mechanisms underlying this response remain unclear. This study investigated the metabolic responses of the liver to cold exposure using transcriptome analysis. Adult frogs were subjected to a temperature of 5{degrees}C for five days, and their liver transcriptome was subsequently analyzed using RNA sequencing. Cold exposure significantly elevated blood glucose levels. Transcriptome analysis revealed extensive alterations in gene expression, including the upregulation of key gluconeogenesis-related genes. Notably, genes involved in FOXO1 signaling exhibited coordinated changes, with increased expression of foxo1 and its regulator prmt1 (arginine methyltransferase) and decreased expression of mdm2 (E3 ubiquitin ligase), suggesting that the phosphorylation of FOXO1 may be suppressed. Consistent with these findings, the expression of gluconeogenic genes (g6pc1 and pck1) was elevated, whereas the glycolytic gene gck was downregulated, indicating a shift towards glucose production. In addition to carbohydrate metabolism, genes involved in lipid and cholesterol metabolism, particularly fatty acid desaturases (scd and fads2), were also upregulated, suggesting that the remodeling of membrane lipid composition may occur under cold conditions. Furthermore, genes related to antioxidant and redox pathways, including those involved in the detoxification of reactive oxygen species and iron sequestration, were induced, indicating enhanced redox regulation. Collectively, these results demonstrate that cold exposure induces coordinated metabolic remodeling in the liver of X. laevis, characterized by enhanced gluconeogenesis, lipid remodeling, and robust redox regulation. SUMMARY STATEMENTCold exposure drives coordinated hepatic metabolic reprogramming in Xenopus laevis, elevating gluconeogenesis, modifying lipid composition, and strengthening antioxidant defenses through integrated transcriptional responses that support survival under a low-temperature environment.

Redox balance is central to aerobic metabolism, yet acute heat stress can destabilize this balance by increasing metabolic rates and shifting the balance of critical electron carriers such as NADH. In early Drosophila melanogaster embryos, maintaining redox balance is particularly critical as embryos undergo a developmental redox shift and rely on oxidative phosphorylation to power nuclear divisions. Here, we assayed six isofemale D. melanogaster lines from temperate (Vermont, USA; France; Japan) and tropical (St. Kitts; Ghana; India) climates to assess metabolic responses to heat in heat-sensitive versus heat-tolerant embryos. We used untargeted LC--MS to measure 33 metabolites and the major redox couples (NADH/NAD+, NADPH/NADP+, and GSH/GSSG) at 25{degrees}C and after a 32{degrees}C heat shock. In all embryos, heat shock induced shared shifts in metabolic profiles, with increases in nucleotide monophosphates (e.g., AMP, CMP, and GMP) and amino acids (e.g., alanine, glutamic acid, serine). In contrast, redox metabolites diverged by region: heat-sensitive temperate embryos shifted toward a more oxidized state (46.6% decrease in NADH/NAD+ ratio and 4-fold increase in oxidized glutathione), while heat-tolerant tropical embryos maintained glutathione balance and increased the NADH/NAD+ ratio by 52.9%, indicating a more reduced state. These patterns are consistent with higher NADH oxidation and greater oxidative stress (inferred from oxidized glutathione) in the temperate embryos, versus better maintenance of redox balance in tropical embryos. Together, our results suggest that maintaining redox balance is a key determinant of acute heat tolerance, and healthy development overall, during early embryogenesis.

The exposure to environmental stressors early in life can shape organisms to express more tolerant phenotypes to the same conditions during adulthood, a process called developmental plasticity. However, this acquired acclimation ability might depend on the intensity of the stimulus perceived later in life. Here, we took advantage of a purple sea urchin Paracentrotus lividus population developed at abnormally high sea temperature in the proximity of a power plant to test the limits of their developmentally acquired plasticity to increased water temperature. We simulated two marine heatwaves, a category I (moderate) and IV (extreme), and exposed the power plant population as well as a naive population developed in natural sea conditions. We measured their respiration rate and molecular responses to these two heatwaves. Regardless of the population of origin, sea urchins exposed to heatwaves showed higher oxygen consumption, indicating an increase in metabolic rates. At the molecular level, the biggest difference between the two populations was found following the moderate heatwave. Compared to the developmentally acclimated sea urchins, the naive population expressed genes coding for proteins with stress response, chromatin remodeling and RNA splicing functions, while suppressing immune response, revealing that developmental exposures can aid in priming the responses of adults to moderate temperature increases. However, a stronger heatwave leveled the differences between the two populations, with sea urchins from both locations expressing genes involved in proteostasis and detoxification. Nevertheless, regardless of the simulated marine heatwave intensity, sea urchins from the naive population always showed enrichment of the spliceosome pathway compared to power plant urchins, which activated immune response genes instead, reflecting fundamentally different thermal stress-coping strategies shaped by their developmental environments. Overall, our results demonstrate the critical yet context-dependent role of developmental plasticity in shaping the resilience of marine ectotherms to climate change.

Small heat-shock proteins (sHSPs) are an ancient and diverse class of molecular chaperones, acting as a first line of defense against proteotoxic stresses. While the canonical sHSPs prevent uncontrollable aggregation of a broad range of non-native substrates, a subset of sHSPs do not exhibit this broad activity in vitro, and their functions in vivo are poorly understood. Interestingly, several such sHSPs are selectively expressed in muscle tissues, including by myogenic programs, indicating likely functional roles. We examined in vivo function of C. elegans HSP-12.6, which possesses no chaperone activity in vitro but regulates lifespan, and is developmentally induced in the muscles of long-lived dauer animals. We found that HSP-12.6 exhibits exceptional selectivity in protecting the muscle function against folding or assembly mutations in thick filament proteins, but not in thin filament or non-filament proteins. This reflected its exclusive chaperone-like binding to the healthy myosin-containing thick filaments, and to their aggregates. HSP-12.6 did not bind other muscle structures or aggregates, including those of thin filaments, and retained its selectivity to either healthy thick filaments or their aggregates when challenged with a toxic aggregation-prone polyQ protein. Our data establish HSP-12.6 as a highly-selective myoprotective chaperone, with client spectrum distinct from other sHSPs.

Protein homeostasis - i.e., proteostasis - is the biological process by which the qualitative and quantitative balance of the proteome is conducted, either by preserving functionally relevant proteins or by degrading unnecessary ones. Stress conditions can modulate cellular proteostasis in order to promote cytoprotection and preserve the viability of living organisms. Among the cellular pathways already described that can play an important role in preserving biological functions by modulating proteostasis are the heat shock response and the ribosome quality control pathways. In this work, we show that the Rqc1p protein is necessary for the thermoadaptation of S. cerevisiae to heat shock, as RQC1-deficient yeast is sensitive to elevated temperatures. In silico approaches - such as multiple sequence alignment, structural analysis, and molecular dynamics simulations - confirmed earlier predictions that Rqc1p shares characteristics with the bHLH family of proteins. We also verified, through computational prediction of sub-cellular localization, that S. cerevisiae Rqc1p contains nuclear localization signals, suggesting that this protein can potentially be translocated toward the nucleus, thereby broadening its current range of recognized biological functions in this organism. Also, analysis of yeast transcriptomes subjected to heat shock showed that Rqc1p mRNA levels do not fluctuate in response to heat shock, suggesting that cellular concentrations of Rqc1p are already at optimal levels to elicit a rapid and effective response during thermal stress in S. cerevisiae.

Mice housed at room temperature (RT, 25{degrees}C) experience chronic mild cold stress compared with those housed at thermoneutrality (TN, 30{degrees}C). We hypothesized that cold stress suppresses circadian transcript expression in peripheral tissues. RNA-seq of hearts, livers, and diaphragms collected every 4 hours over 48 hours in constant darkness identified mRNA transcripts exhibiting {approx}24-hour rhythms (REGs). TN produced tissue-specific changes in REG number, identity, and phase without altering core circadian clock transcript levels. Cardiac REGs increased 4-fold, diaphragm REGs 1.5-fold, and hepatic REG identity shifted substantially. GO analysis revealed coordinated reorganization of rhythmic metabolic programs in the heart and liver. These data demonstrate that ambient housing temperature has tissue-specific effects on the number, identity, and temporal organization of rhythmically expressed transcripts in the heart, liver, and diaphragm.

Long-term winter dormancy in ectotherms (brumation) defines the annual cycle of many temperate-zone reptiles, yet the transcriptional regulation that supports survival across months of cold and aphagy remains poorly understood. We generated time-resolved transcriptomic profiles of liver and testis from male red-sided garter snakes (Thamnophis sirtalis parietalis) at five timepoints spanning the eight-month brumation cycle: pre-brumation, early, mid-, and late brumation, and post-arousal under continued aphagy. Time-course negative-binomial regression (maSigPro) followed by gene-set enrichment analysis identified 3,715 transcripts in liver and 5,828 in testis with significant temporal expression structure organized into five overarching temporal patterns: sustained downregulation, downregulation with post-arousal recovery, sustained upregulation, brumation-specific upregulation and cyclic modulation. Liver showed coordinated upregulation of fatty acid mobilization enzymes (ATGL, FOXO1, PPAR, CPT1A) and gluconeogenic regulators (CREBBP, PCK1) coincident with sustained low temperatures. Additionally, low temperature transcriptional activity was suggestive of a shift toward hepatic lipid mobilization and alanine-supported gluconeogenesis. Testis showed sustained suppression of meiosis, reproduction, and DNA-metabolism gene sets that did not fully recover at arousal consistent with this species dissociated reproductive pattern. Both tissues showed coordinated upregulation of stress-response pathways involving heat-shock proteins, HIF1 and a glutathione-based antioxidant defense. Interestingly, three vitellogenin transcripts and 17{beta}-hydroxysteroid dehydrogenases associated with estradiol-favoring steroid metabolism were upregulated in male liver during late brumation, which is not expected during natural physiology in adult males. Together these data support a framework in which temperature- and starvation-associated transcriptional programs contribute to survival of one of the longest, coldest brumations documented in a squamate. Summary statementA time-resolved transcriptomic analysis of liver and testis spanning eight months of winter brumation in Thamnophis sirtalis parietalis reveals gene expression patterns consistent with a temperature-associated shift toward hepatic lipid mobilization, sustained reproductive suppression, and vitellogenin response in males.

Heat shock protein 90 (HSP90) assists protein folding and maturation of many important signaling proteins. In various diseases, HSP90 clients contribute to aberrant signaling, and HSP90 inhibition is being explored as a potential therapeutic approach. Commonly researched HSP90 inhibitors target the ATP-binding pocket, thereby disrupting the ATP-induced closure of HSP90. Drugs disrupting the HSP90 ATPase cycle by targeting the closed state of the chaperone have not been developed. Here, we present de novo design and selection of protein binders interacting exclusively with the closed state HSP90. Two such binders, H2 and H4, were identified that feature a similar fold and comparable affinities for HSP90 but display different binding kinetics. The structures of the HSP90 complexes with H2 and H4 were determined by cryo-EM single particle analysis, and they revealed high accuracy of the BindCraft predictions. H2 and H4 compete with p23 at one but not both symmetrical p23 binding sites on HSP90. H2 expressed in HEK293T cells moderately elevated expression of HSP70 and had no effect on the HSP90 level, suggesting muted heat shock response. Overall, this study demonstrates that the de novo binders represent novel and promising tools to probe the potential utility of HSP90 inhibition by targeting its closed state.

Many marine invertebrates are characterized by broad and highly plastic thermal limits, though the dynamic molecular mechanisms that enable extended thermal acclimation remain poorly understood. A classic example is the green crab (Carcinus maenas), which is a prolific and damaging non-indigenous species. Using a 22-day thermal exposure to cold (5{degrees}C), ambient (13{degrees}C), or warm (30{degrees}C) temperatures, we characterized plastic shifts in C. maenas performance using respirometry and time-to-right. We then used untargeted metabolomics and lipidomics analysis of heart tissues from days 4 and 22 to identify the molecular mechanisms underpinning plastic responses over time. Crabs at 30{degrees}C exhibited higher oxygen consumption rates than counterparts at 5{degrees}C. Interestingly, oxygen consumption rate increased over time at both temperatures, indicating thermal plasticity of aerobic respiration. Temperature-dependent metabolic reprogramming was employed by crabs to sustain aerobic respiration across temperature. Catabolism of branched-chain amino acids was important for energy production at elevated temperatures, while catabolism of arginine may have sustained the minimal energy needs of crabs exhibiting metabolic depression at cold temperatures. Righting response was positively correlated with temperature, and did not exhibit any changes over time. Lipidome remodeling consistent with homeoviscous adaptation could have enabled motor activity across temperature. Higher abundances of saturated and monounsaturated lipids likely provided structural integrity to cell membranes at 30{degrees}C, while lower abundances of these compounds may have enabled membrane fluidity at 5{degrees}C. Our work demonstrates the importance of ongoing molecular reprogramming in long-term acclimation, even when whole-animal physiology remains relatively stable. Summary StatementThis study demonstrates how the highly invasive green crab regulates metabolite and lipid pathways over time to maintain physiological performance across different temperatures.

Cells employ a bevy of transcriptional and post-translational stress responses to tolerate the burden of misfolded proteins induced by stress. In particular, the heat shock response facilitates the upregulation of molecular chaperones and protein remodeling factors that mediate proteostasis in response to accumulated misfolded proteins in the nucleus and cytosol. However, in response to stress neurons struggle to induce a canonical heat shock response, highlighting our poor understanding of how neurons maintain proteostasis. Specifically, the ability of post-mitotic respiring cells to regulate the heat shock response in comparison to their rapidly dividing, predominantly glycolytic counterparts has been under-studied. In this study, we employ yeast models that are easily manipulated to generate energy via glycolysis or mitochondrial respiration by changing the carbon source in the media. Using this model, we demonstrate that Hsf1 activity, the heat shock response and proteostasis are impaired in respiring cells. Interestingly, our data show that reduced Hsf1 activity regulates viability of respiring cells, with respiring cells poorly tolerating constitutively activated Hsf1. Finally, we describe alternative post-translational programming of the molecular chaperones Hsp70 and Hsp104 that plausibly enables respiring cells to mediate proteostasis despite a dampened heat shock response. Our findings offer new insights into possible proteostatic strategies employed by cells in different metabolic conditions.

Many insects enter diapause, a programmed state of developmental arrest that enables survival under adverse environmental conditions. In Drosophila melanogaster Meigen, 1830, diapause is characterized by reproductive arrest and reduced intestinal growth, accompanied by suppressed intestinal stem cell (ISC) activity. Juvenile Hormone (JH) promotes ISC proliferation under favorable conditions, but its capacity to modulate stem cell dynamics during cold-induced diapause remains unclear. Here, we investigated whether JH signaling can reactivate midgut remodeling in adult females maintained at 11. At this temperature, flies exhibited pronounced gut atrophy and elevated Phospho-histone H3 (PH3+) cell abundance, consistent with temperature-dependent G2/M phase arrest JH treatment significantly increased the proportion of Delta-positive progenitor cells in the anterior (R2) and posterior (R5) midgut regions at both 11 and 25, demonstrating that JH acts as a conserved mitogen for the ISC pool irrespective of thermal environment. A trend toward reduced PH3+ accumulation in the posterior midgut following JH treatment (p = 0.061) suggests possible facilitation of mitotic exit, though this effect did not reach statistical significance. Despite cellular-level changes, JH treatment did not restore overall gut size, indicating that the 72-84 hour exposure window was insufficient for subsequent tissue hypertrophy. Additionally, we identified a recurrent cold-induced pathology of gut distension, provisionally termed Lumen Obstruction Syndrome (LOS), which was independent of JH signaling. These findings reveal an uncoupling of JH-driven stem cell expansion from gross organ growth under diapause conditions, highlighting the selective sensitivity of the ISC compartment to endocrine signaling during environmental stress.

The deepest ocean is one of the most extreme environments for life on our planet, combining near-freezing temperatures, low oxygen levels, and hydrostatic pressures reaching 111 MPa (1100 atm). Extreme pressures are predicted to alter many aspects of biology, including the physical properties of biological hydrogels, protein structure, and the solubility of gases in water. How organisms have adapted to live in these conditions is poorly understood. Studying these organisms in situ is difficult and requires specialized deep-sea equipment capable of withstanding the extreme pressure; raising these organisms in captivity is also challenging due to their extreme habitat requirements. Given these difficulties in studying deep-sea organisms, we set out to identify the problems shallow-dwelling organisms face due to increased pressure. These can provide insights into how organisms tolerate life in the deepest parts of the ocean. This project aims to take embryos of the shallow-dwelling aquatic organism Xenopus laevis, determine how surface-dwelling organisms fail under high hydrostatic pressure, and identify a means to survive this deadly pressure. We have designed a system to expose different embryonic stages of X. laevis to high pressures and observe its effects. After identifying the limits of survivability, we sought to understand how these embryos can acclimate to changing pressures. Comparative RNA-seq and cross-species analyses revealed a conserved, pressure-induced transcriptional response across phyla, with the heat shock pathway among the most strongly activated. Pre-activation of this pathway via prior pressure or other stressors enhances survival under otherwise lethal hydrostatic conditions.

ObjectiveN-acetylcysteine (NAC) is a clinically available antioxidant with potential applications in trauma-induced hypermetabolic states, including burn injury and crush syndrome. However, its effects on heat-stressed skeletal muscle cells remain incompletely characterized. This study conducted a secondary analysis of a publicly available dataset to quantify NACs protective effects against heat-stress-induced cellular damage. MethodsWe re-analyzed a publicly available dataset (Lu J, 2024, Mendeley Data, doi:10.17632/wffrtcgbnx.1) containing 21 observations across three conditions: Control (n=3), Heat Stress only (HS, n=3), and HS with NAC at five doses (0.5-8.0 mM, n=3 per dose). The primary outcome was the protective ratio [(HS+NAC - HS) / (Control - HS)], where 1.0 indicates complete protection. Statistical analyses included one-way ANOVA, post-hoc t-tests with Bonferroni correction, Cohens d effect sizes, and bootstrap confidence intervals. ResultsHeat stress significantly reduced cell viability by 56.3% (Control: 100.0 {+/-} 12.2 vs HS: 43.7 {+/-} 5.1; t(4)=7.37, p=0.002, Cohens d=6.02). NAC demonstrated a biphasic dose-response with maximal protection at 2.0 mM (66.7 {+/-} 14.4), yielding a protective ratio of 0.409 (95% CI: 0.146-0.675), representing 40.9% protection against heat stress damage. The comparison between HS and HS+NAC (2.0 mM) showed a large effect size (Cohens d = 2.12) but did not reach statistical significance (p = 0.060) due to the small sample size. One-way ANOVA confirmed overall group differences (F(2,18)=32.39, p<0.001, 2=0.783). ConclusionsNAC provides partial protection against heat stress-induced skeletal muscle cell damage at 2.0 mM, with a large effect size suggesting clinical relevance despite limited statistical power. These preliminary findings support further investigation of NAC as an adjunct therapy in trauma-induced hypermetabolic states. All analysis code is provided for reproducibility.

The naked mole rat is an evolutionary outlier among mammals, exhibiting extreme longevity, cancer resistance, hypoxia tolerance, pain insensitivity, eusociality, poikilothermy and other distinctive physiological traits, most of which likely resulted from its adaptation to highly adverse subterranean habitat. Despite accumulating data, the genetic and molecular basis underlying these traits remain poorly understood. Through analyses of 18 distinct protein attributes and allied datasets across hystricomorphs, myomorphs, carnivores, and primates, we observed lineage-specific evolutionary divergence in intrinsic protein disorder in the naked mole rat. The disorder turnover exhibited functional dichotomy. The gain of disorder preferentially associated with proteostasis, immune regulation, neurodevelopment, skeletal growth and tumour suppressive properties, while loss of disorder modulated mostly the cardiac development. The proteins that gained disorder in NMR exhibited lower degradation rates, consistent with stabilization through phase-separation, while the proteins losing disorder show pronounced divergence in gene expression. The disorder turnover was primarily driven by indels affecting functional regions including Pfam domains, ANCHOR-predicted binding sites, short linear motifs, stress induced modifications of Tyr, Met, and Cys residues. Notably, the gained disordered regions were inferred to be redox-sensitive, aligning to exceptional stress tolerance in naked mole rats. Collectively, our results highlight an unusual and previously overlooked large-scale proteome remodelling that drives the molecular evolution of extraordinary traits of naked mole rat. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=169 SRC="FIGDIR/small/720964v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@644d1dorg.highwire.dtl.DTLVardef@102c9e4org.highwire.dtl.DTLVardef@14c770org.highwire.dtl.DTLVardef@31bc5e_HPS_FORMAT_FIGEXP M_FIG C_FIG

Circadian regulation of proteostasis, a key determinant of muscle health, remains poorly understood. Here, we identified DNAJB6, an Hsp40 (DnaJ) co-chaperone, as a substrate of the circadian E3 ligase FBXL21. FBXL21 mediated the ubiquitination-dependent proteasomal degradation of both DNAJB6 and its client proteins including Desmin; causative mutations of DNAJB6 in myopathies, however, rendered resistance to FBXL21-directed degradation. Fbxl21 KO C2C12 cells displayed aberrant accumulation of Desmin, and showed aggravated cytoplasmic accumulation of TDP-43, another DNAJB6 client protein, in heat shock response. Under timed exercise as a physiological stressor, WT mice displayed robust diurnal rhythms in the levels of stress granule markers (G3BP1 and FUS) and TDP-43 as a function of exercise timing. In contrast, the Fbxl21 hypomorph Psttm mutant mice showed elevated expression of these proteins without exercise, which was exacerbated under exercise-induced stress conditions; importantly, these abnormalities were rescued by skeletal muscle-specific FBXL21 expression. Our study elucidates a novel diurnal regulatory mechanism of skeletal muscle proteostasis via FBXL21 as a chaperone-linked E3 ligase, highlighting the FBXL21-DNAJB6 axis as a potential therapeutic target for myopathies.

Mass coral bleaching events, driven by rising ocean temperatures, are pushing reef ecosystems toward collapse on a global scale. Because oxidative stress is an early driver of coral bleaching, strategies that enhance coral antioxidant defenses may improve coral resilience under thermal stress. Here, we tested a targeted antioxidant supplementation designed to enhance oxidative stress regulation in three representative Red Sea scleractinian coral species subjected to a thermal challenge. While responses varied among species and physiological metrics, supplemented corals consistently maintained higher photophysiological performance under heat stress. In Stylophora pistillata, antioxidant supplementation was associated with enhanced catalase activity, maintenance of glutathione redox homeostasis, and lower intracellular reactive oxygen species levels. In contrast, non-fed corals exhibited oxidative imbalance, increased lipid peroxidation, and impaired photophysiological recovery, while corals receiving a non-enriched heterotrophic diet showed an intermediate response characterized by increased catalase activity but persistent glutathione oxidation and elevated ROS during recovery. Together, the dietary treatments revealed a gradient in oxidative regulation, ranging from insufficient antioxidant protection in autotrophic corals to enhanced oxidative homeostasis in antioxidant-supplemented corals. Our findings demonstrate the potential of targeted nutritional antioxidant supplementation to enhance coral oxidative regulation and physiological performance under elevated temperatures, highlighting a promising complementary approach for coral conservation and restoration efforts.

NRF1 is a key mediator of the proteasome recovery pathway, yet its regulation by ER-resident factors is not fully elucidated. Here, we demonstrate that selenoproteins SELS and SELK are critical regulators for NRF1 protein dynamics. SELS stabilizes NRF1, while SELK induces its insolubilization. Their deficiency leads to a hyper-accumulation and increased nuclear localization of NRF1 under proteasome inhibition condition. This results in an augmented transcriptional response of proteasome subunits. These results indicate that SELS and SELK cooperatively gate NRF1 activity by controlling its retrotranslocation and solubility, highlighting a novel layer of selenoprotein-mediated quality control in the proteostasis network.

Climate change-induced heatwaves threaten ectotherms, whose physiology is tightly coupled to ambient temperature. Vulnerability assessments often rely on data from one or a few populations, implicitly assuming uniform thermal sensitivity across species genetic diversity. Quantifying such variation is especially important for traits with wider ecological consequences; our focus here is on immune function, which shapes disease dynamics. We addressed this knowledge gap using ten clonal lineages of the New Zealand snail Potamopyrgus antipodarum exposed to ambient (17{degrees}C) or heatwave conditions (27{degrees}C) for 4 or 8 days. We measured two complementary innate immune traits: general phenoloxidase-like (PO-like) activity, which integrates the activity of multiple phenoloxidase enzymes, and laccase activity, which targets a specific PO enzyme subclass important in mollusc immunity. Heat exposure suppressed both traits, but patterns differed across clones. While PO-like activity declined uniformly, laccase activity showed substantial among-clone variation in heatwave responses at day 4, though these differences converged by day 8. Heat-induced immune suppression is thus trait-specific, depends on genetic background, and varies with exposure duration. Together, these results demonstrate that studies limited to a single genotype, population, or timepoint risk miscalculating species-level vulnerability.