Transthyretin (TTR) is a kinetically stable protein in the bloodstream, cerebrospinal fluid, and in the eye, whose aggregation causes a prominent human amyloid disease, TTR amyloidosis (ATTR). Dissociation of the wild-type TTR tetramer into metastable dimers is rate-limiting for aggregation at acidic pH and unfolding in denaturant solutions at neutral pH. However, this “canonical dimer” pathway of denaturation is not the only one accessible under conditions possibly relevant to amyloid disease. At pH-values reached in the late endosome and lysosome (pH 4.0 to 5.0), as well as with perturbing mutations at neutral pH, a second denaturation pathway becomes accessible involving a more expanded transition state. This “alternative unfolding” pathway is evident via a characteristic switch to a steeper slope in the plot of the log-transformed unfolding rate constant vs. the urea concentration. Using mutations, we identify globally distributed locations in the protein that are sensitive to pathway-switching and correlate them with structural information. We show that flux along the alternative denaturation pathway becomes kinetically competitive in a subset of variants under mildly acidic conditions. A small-molecule kinetic stabilizer of TTR decreases flux along the canonical denaturation pathway, and exhibits reduced influence on denaturation by the alternative pathway. We present a “universal” plot allowing classification of TTR mutants to either pathway, and suggest a mechanism by which the two pathways operate. We speculate that the existence of an alternative unfolding pathway could allow for rapid protein degradation and turnover of kinetically stable TTR under acidic conditions in the autolysosome.
Pulsatile actomyosin networks emerge as a widespread mechanism driving tissue morphogenesis. Compared with myosin-II pulses, F-actin pulses are largely unexplored. By studying Drosophila oogenesis, we report that basal pulsatile actomyosin networks consist of F-actin bundle and meshwork architectures, implicating the existence of different F-actin microstructures and corresponding nucleators. Here, Rac1 and the Scar/WAVE-Arp2/3 complex (branched F-actin nucleator), exhibiting constant levels, are necessary to support F-actin pulsation, whereas pulses of Dia (unbranched F-actin nucleator) trigger F-actin pulsation. The pulsatile F-actin networks recruit the F-actin turnover regulator cofilin, thus generating cofilin pulses. Cofilin at relatively low concentration can cooperate with F-actin nucleators to amplify F-actin and enhance its pulsation, while cofilin at relatively high concentration might trigger the F-actin disassembly to attenuate its pulsation. These two different effects of cofilin on F-actin pulsation were confirmed by Zdk-cofilin optogenetics. Rac1 signaling, Dia, and cofilin are also crucial for F-actin pulses in border cell migration. Our findings thus reveal a coordinated regulation of F-actin pulses conferring actomyosin contractility in morphogenesis and cell migration.
Poxviruses have evolved robust immunoevasion strategies to facilitate replication in the cytosol. We previously reported that like several RNA viruses, vaccinia virus replication is impaired in the absence of the host cap-binding translation repressor protein 4EHP (eIF4E2), implicating the latter in host antiviral defense regulation and immunosuppression. Here, we show that the vaccinia virus-encoded K3L protein interacts with 4EHP via its obligatory binding partner GIGYF2 to increase the stability of the 4EHP/GIGYF2 complex. Consequently, K3L bolsters 4EHP/GIGYF2-mediated mRNA translation repression. Thus, we demonstrate that a 4EHP/GIGYF2-mediated mechanism is exploited by and conserved among RNA and DNA viruses as a potential immunoevasion strategy. Our findings document a 4EHP/GIGYF2-dependent stringent regulation of infection by poxviruses, a clinically important family of viruses that are employed as vaccine vectors and in oncolytic viral therapy.
The human walking step is initiated by a distinctive heel-strike. Our closest living relatives, the African apes, are among the few other animals that are also thought to heel-strike. Qualitative similarities between human and African ape heel-strikes have been invoked in theories about the origins of hominin bipedalism, but some quantitative data suggest possible interspecies differences in foot-strike mechanics that hint at more complex evolutionary scenarios. However, these data are currently too sparse to fully characterize these differences or understand their functional consequences for hominin evolution. To address these gaps, we collected detailed three-dimensional marker-based kinematic and ground reaction force data in humans and in chimpanzees walking bipedally and quadrupedally. We found that chimpanzees used 2.4 to 8.6 times greater ranges of foot-strike angles than humans and often did not heel-strike. Statistical models revealed a possible explanation for this finding, showing that in both chimpanzees and humans, heel-striking is associated with high impact peak forces and loading rates. We also found that humans expend 26 to 41% more metabolic energy when they contact the ground with the distal foot before the heel, indicating an important adaptive trade-off: Heel-striking lowers the energetic cost of bipedal walking but increases potentially damaging impact loading rates. These results suggest that early hominins with primitive lower limb anatomy faced a choice between high impacts and relatively uneconomical walking, either of which likely constrained their terrestrial mobility. The later evolution of larger heels and lower limb joints enabled safe, economical heel-striking and greater daily ranging.
Music is widely utilized to support recovery from stress, yet the precise neural mechanisms driving this therapeutic effect remain poorly understood. Crucially, it has been unclear whether music provides unique neurobiological benefits or simply acts as a general, relaxing auditory stimulus. Here, we demonstrate that music selectively facilitates multisystem recovery from acute stress—enhancing positive mood (PM) and accelerating autonomic stabilization (electrodermal activity and heart rate)—significantly outperforming an active natural sound control. Using functional MRI and dynamic causal modeling, we revealed the network architecture underlying this advantage. Compared to natural sounds, music drives a distinct reorganization of stress-regulation networks, establishing a directional, causal pathway from the auditory cortex to the insula and thalamus. On a faster timescale, dynamic functional connectivity reveals that this network reconfiguration is actively governed by musical structure: moment-to-moment fluctuations in perceived musical tension track transient shifts from stress-network engagement to neural downregulation. Furthermore, these music-specific connectivity changes are directly associated with improvements in PM. Together, these findings identify a temporally evolving mechanism by which the brain’s processing of structured musical sequences acts as a dynamic regulatory driver, reconfiguring neural architectures to restore psychological and physiological homeostasis.
Despite the plethora of knowledge about the benefits of meiotic recombination and numerous theoretical studies examining how recombination rates evolve, there is a general lack of empirical support and consensus across species. To fill this knowledge gap, we characterized the evolution of recombination landscape in maize during its domestication from teosinte and related the observed changes to established theoretical frameworks. Through examining recombination in experimental populations of maize and teosinte and the population genomics approach of identifying historical recombination events using ancestral recombination graph inference to generate saturated maize and teosinte recombination maps, we found that during domestication, maize experienced a 12% increase in its genome-wide recombination rate. Furthermore, maize evolved higher recombination rates on the long arms of chromosomes in regions closer to centromeres, where recombination is generally very low. The repatterning of crossover events came from changes in global crossover positioning rather than alterations in cis-acting chromatin factors. Consequently, we found evidence of selection acting on trans-acting recombination modifiers affecting crossover interference and controlling the interference-dependent class I crossover pathway. We show that CO repatterning was likely beneficial for maize fitness, as significant recombination rate increases were predominantly in gene-rich regions, which harbor domestication-related variation. This work suggests genomic and mechanistic processes leading to the evolution of meiotic recombination landscape in response to directional selection pressure and provides evidence for the evolutionary advantage of recombination.
In multiple sclerosis (MS), spontaneous remyelination occurs in early disease; however, this process becomes inefficient over time, resulting in sustained neurodegeneration and clinical deterioration. It is known that global tumor necrosis factor receptor 2 (TNFR2) deletion in experimental autoimmune encephalomyelitis (EAE), the murine MS model, causes a severe nonremitting disease; however, the underlying mechanism is poorly understood. Here, through bulk and single nucleus RNA sequencing, we identify endothelial TNFR2 deletion as the driver of nonremitting disease, as it is sufficient to drive a severe nonremitting phenotype that closely mirrors global TNFR2 loss. Remyelination failure upon endothelial cell-specific TNFR2 ablation was also detected at the Cuprizone model of remyelination confirming its dominant role in central nervous system (CNS) repair. Notably, this effect was independent of immune cell influx or vascular permeability changes but associated with fibronectin overexpression and accumulation in demyelinating lesions. Fibronectin accumulation led to the sequestering of oligodendrocyte progenitor cells (OPCs) at the demyelination areas and prevented myelin repair. Therapeutically, systemic fibronectin inhibition restored regeneration and clinical remission, as well as prevented OPC accumulation at lesions, providing strong preclinical evidence for fibronectin-targeting therapies in MS and other demyelinating disorders. These findings establish endothelial cells as key regulators of the parenchymal environment permissive to remyelination and open avenues for MS treatment strategies focused on vascular-driven CNS regeneration.
The Convention on Biological Diversity’s ambitious target to “effectively conserve” 30% of the world’s oceans in protected areas by 2030 risks being undermined by a primary focus on total area protected rather than realized conservation outcomes. Area-based assessments can overstate success because few marine protected areas (MPAs) possess strong restrictions and high compliance. Here, we estimate the extent that conservation outcomes are realized across the global MPA network for shallow reefs using standardized fish survey data. We first compare observed fish biomass from 552 surveyed MPA zones in temperate and tropical seas to modeled counterfactuals in the absence of protection, then extend these findings across the global network using key MPA attributes and predictive models. We estimate that at best, a quarter of the global MPA network is likely delivering meaningful conservation outcomes, with effectiveness strongly contingent upon the level of compliance with fishing restrictions. If shallow reef responses are representative of other marine ecosystems, then <2% of the ocean is effectively protected, compared to 9.8% presently reported. The unsupported assumption that MPA designation and management attributes directly translates to tangible biodiversity outcomes has apparently resulted in pervasive overestimation of conservation achievement. Critically, long-term success of MPAs will require further research, informed governance, and improved strategic policies that focus on the intricate mechanisms underlying compliance with mandated area restrictions.
Obstacles to translation elongation stall ribosomes and allow deleterious proteins to accumulate, which threatens cellular health. Cells recognize and clear stalled ribosomes via several interrelated pathways, although the mechanisms by which cells distinguish stalled from normally elongating ribosomes and mount an appropriate response are incompletely understood. While recent work highlights how ribosome collisions help cells to recognize stalled ribosomes, how other factors contribute to detection remains unclear. Here, we report a requirement for the translational factor eIF5A in the mRNA decay response to ribosomal stalling, i.e., No-Go mRNA Decay (NGD). We identified the Caenorhabditis elegans polyamine transporter, catp-6 , via a forward genetic screen as a factor required for NGD. During our mechanistic dissection of the catp-6 phenotype, we uncovered a role for cellular polyamines and the translation elongation factor eIF5A in NGD, and we show this requirement is conserved from C. elegans to Saccharomyces cerevisiae . Our analyses support the idea that cells use eIF5A to identify ribosomal stalls and execute NGD and uncover a molecular function for a core protein synthesis factor in limiting expression from stall-inducing mRNAs. Our work offers insight into how cells identify and remove problematic mRNAs from the translational pool. Our work also raises the possibility that dysregulated mRNA decay is an unrecognized pathophysiology associated with polyaminopathies and eIF5A disorders, of relevance to varied neurodegenerative and aging phenotypes and efforts to pharmacologically inhibit eIF5A.
The Fc region of immunoglobulin E (IgE-Fc) is an important therapeutic target due to the antibody's critical role in allergic disorders through interactions with high-affinity (FcεRI) and low-affinity (CD23) receptors. IgE-Fc is known to be conformationally flexible, undergoing large-scale structural changes that modulate receptor binding and downstream biological functions. The mechanistic basis for how ligands induce these allosteric changes is not fully understood. In this study, we investigate structure-function relationships of IgE by characterizing four closely related anti-IgE-Fc Fab fragments with highly conserved sequences that recognize a shared epitope at the base of the Cε2 domain. Despite their sequence similarity, these Fabs exhibit markedly different binding characteristics, stoichiometries, and functional activities. Furthermore, the crystal structures of these four Fab complexes reveal that the bound IgE-Fc adopts a wide range of conformations. These structural differences directly dictate the functional outcomes, ranging from conformations that facilitate FcεRI binding to those that prevent or destabilize receptor interaction. Our findings demonstrate that highly similar antibodies binding to the same epitope on a protein that exhibits significant conformational plasticity can elicit distinct and divergent functional outcomes. This work challenges the conventional antibody discovery paradigm, i.e., "same epitope, same functional outcome," and highlights the importance of accounting for both the target's structural flexibility and the resulting functional diversity within antibody selection strategies. This is especially critical when targeting dynamic proteins where allosteric mechanisms are fundamental to function.
Theory suggests sexual selection will enhance population viability by purging deleterious alleles. However, direct genomic evidence for this fundamental idea is scarce and contradictory. We combined long-term experimental evolution with whole-genome resequencing to directly test how sexual selection affects mutation load, genomic divergence, and extinction risk in small populations (maximum N e = 40) of Tribolium castaneum . After 156 generations, populations evolving under strong sexual selection carried substantially fewer deleterious alleles than populations under weak sexual selection, based on both individual-level estimates of missense and nonsense variants and population-level R xy analyses, indicating more efficient purging of deleterious alleles. In contrast, nucleotide diversity and runs of homozygosity were similar across treatments, indicating that purging acted most strongly on deleterious variation, and that reduced mutation load in these small populations under strong sexual selection was not explained by demographic effects. Importantly, population-level mutation load estimates best explained extinction risk under inbreeding, directly linking sexual selection to purging and population viability. Genome scans of high and low sexual selection populations revealed peaks of divergence, which included genes involved in courtship, sex discrimination, and seminal fluid proteins. Our results provide direct genomic evidence that sexual selection can reduce mutation load without eroding standing genetic diversity and thus adaptive potential, while driving adaptive divergence in reproductive traits. This beneficial purging may help explain the widespread prevalence of sexual reproduction in nature despite inherent costs and have important ramifications as to how we manage populations of conservation concern.
The Patescibacteriota, also known as the Candidate Phyla Radiation (CPR), represent a large lineage of ultrasmall bacteria with highly reduced genomes and obligate dependence on bacterial hosts. Although genomic analyses have revealed CRISPR-Cas and restriction-modification systems in many CPR genomes, no cognate bacteriophages (phages) have been isolated, leaving CPR-phage interactions unexplored. Nanosynbacter lyticus TM7x, the first cultivated CPR bacterium, grows episymbiotically on its host, Schaalia odontolytica XH001, in the human oral microbiome. Here, we identify Xhp1, an inducible prophage of XH001 that is preferentially activated during episymbiosis with TM7x. Released Xhp1 particles infect prophage-free XH001 via distinct strategies determined by host growth mode, establishing lysogeny under planktonic conditions but driving lytic infection during surface-associated growth. Xhp1 also binds efficiently to TM7x and exhibits limited infection under the conditions tested, indicating direct phage-CPR interactions. Importantly, TM7x modulates Xhp1 availability in a spatially dependent manner. In planktonic culture, free-floating TM7x reduces lysogenic conversion of XH001ΔXhp1, consistent with TM7x acting as a phage sink that lowers effective phage concentration. In contrast, during surface-associated growth, TM7x increases XH001ΔXhp1 susceptibility to lytic infection, likely by locally concentrating phage particles within a constrained niche. These results demonstrate that CPR bacteria can regulate viral encounter rates through spatial organization. In spatially structured environments such as oral biofilms, such modulation may shape infection dynamics and community structure. Together, this work characterizes the first CPR-targeting phage and reveals a an important role for phages in CPR-host bacteria interactions.
Karrikins (KARs) are a class of butenolide molecules discovered in smoke hypothesized to mimic an undiscovered plant hormone, KAI2 ligand (KL). KAR/KL signaling regulates germination, seedling development, stress tolerance, and symbiotic interactions with soil microbes, among other traits. KAR/KL signaling is initiated by KARRIKIN INSENSITIVE2 (KAI2), an ɑ/β-hydrolase related to the strigolactone enzyme-receptor DWARF14 (D14). Activated KAI2 forms protein-protein interactions that trigger proteasomal degradation of a transcriptional regulator, SUPPRESSOR OF MAX2 1 (SMAX1), initiating changes in gene expression. D14-LIKE2 (DLK2), an ancient paralog of KAI2 and D14, is a prominent transcriptional marker of KAR/KL signaling in many plants that has uncertain function. We find that DLK2 forms a negative feedback loop that attenuates KAR/KL signaling in Arabidopsis thaliana. This mechanism complements that of KARRIKIN UPREGULATED F-BOX1 (KUF1), which putatively restricts KAR/KL metabolism through targeted protein degradation. Loss-of-function mutations of DLK2 show little effect alone, but synthetically enhance the constitutive KAR/KL responses of kuf1 seedlings. Overexpression of DLK2 proteins from several plants increases the abundance of a SMAX1 ratiometric reporter. DLK2 does not require nuclear localization to protect SMAX1, suggesting its function is independent of interactions with SMAX1 or its transcriptional regulator partners. DLK2 hydrolyzes a profluorescent, desmethyl butenolide reporter molecule that is putatively analogous to KL. We hypothesize that DLK2 catabolizes KAI2 ligand(s) without participating in KAR/KL signaling directly. This functional antagonism could have evolved after KAI2 gene duplication through subfunctionalizing mutations that disrupted protein-protein interactions while preserving enzymatic activity.
Antibody-based immunotherapy targeting amyloid-β (Aβ) is a promising approach for Alzheimer's disease (AD). However, its efficacy is limited by rapid hepatic sequestration, complement activation, and liver dysfunction. In this study, we synthesized low-immunogenic 450-nm functionalized mesoporous silica nanoparticles (PEG-MSN-1F12) by conjugating the anti-Aβ42 monoclonal antibody 1F12 to polyethylene glycol-modified mesoporous silica nanoparticles to address these challenges. In APP/PS1 mice, intravenous PEG-MSN-1F12 administration markedly enhanced peripheral Aβ clearance, promoted intestinal excretion, reshaped gut microbiota, and alleviated intestinal inflammation, thus reducing AD-associated hepatic burden. Peripheral Aβ removal further led to decreased brain Aβ deposition, attenuated microglial activation, and improved cognition. These findings highlight that the use of particle size-engineered antibody-nanoparticle conjugates is a safe and effective strategy to overcome hepatic sequestration, augment Aβ clearance, and improve AD outcomes.
With global warming, rising atmospheric vapor pressure deficit (VPD) has emerged as a critical driver of vegetation productivity and the terrestrial carbon sink. Yet, the thresholds beyond which VPD constrains tree growth remain poorly quantified. Using 2,953 tree-ring sites and combining generalized additive models with threshold regression models, we demonstrate that growth-related VPD thresholds are widespread. Approximately 63% of the studied species groups exhibited identifiable thresholds, which were generally lower in cool, humid regions and higher in warm, dry environments. For the same tree species occurring under contrasting aridity conditions, thresholds also differed substantially. As VPD has risen, the proportion of sites exceeding these thresholds has increased rapidly since about 1970 and is projected to rise further under different emissions scenarios. Under SSP5-8.5 in particular, approximately 79.8% of the sites are projected to be exposed to VPD above their thresholds by the end of the century. Although potential upward threshold shifts associated with acclimation or adaptation could partly reduce future exceedance, this buffering effect becomes increasingly limited under stronger climate forcing. Without effective climate mitigation, rising VPD will increasingly exceed the tolerance thresholds of trees, placing more trees under sustained growth constraints and undermining terrestrial carbon sequestration.
Understanding the factors that regulate ecosystem processes, such as nutrient cycling, is increasingly important as global change accelerates the degradation and defaunation of ecosystems. In marine ecosystems, fish communities recycle and redistribute nutrients through excretion, directly influencing nutrient dynamics with implications for community dynamics and ecosystem function. The stability of consumer-mediated nutrient dynamics (CND) is threatened as global change disrupts species interactions, rewires food webs, and alters biogeochemical cycles. However, the stability of CND has rarely been quantified. While decades of research on primary producers show that biodiversity can buffer ecosystem functions against environmental variability, we know little about whether consumer diversity can have similar effects for CND. We estimated the temporal stability of nitrogen supply for marine fish communities using 146 time series, spanning ~25 y (1999-2023) and six long-term monitoring programs across coral reefs, mangrove creeks, seagrass beds, and kelp forests and representing ~1.5 million individual fishes. Across ecosystems, species richness strongly and positively predicted the temporal stability of CND, consistent with diversity-stability theory. However, richness was not the dominant driver within ecosystems. Instead, species asynchrony (i.e., variation in biomass fluctuations among multiple species) emerged as the strongest and most consistent predictor, with higher synchrony destabilizing CND. These findings extend biodiversity-stability theory to consumers and show that both biodiversity and dynamic community properties govern the stability of CND, with implications for conserving marine ecosystem function in the wake of global change.
Of the classic psychedelics, lysergic acid diethylamide (LSD) is perhaps the best-known, but its complex chemical architecture has limited synthetic investigations aimed at generating analogues with improved safety and efficacy profiles. Here, we systematically deconstruct the tetracyclic ergoline core of LSD to create 9 simplified ergoline analogues (i.e., ergologs) and evaluate them in pharmacological assays relevant to 5-HT2A, 5-HT2B, and 5-HT2C receptor function. Our work revealed the key molecular features and minimal pharmacophore of LSD necessary to produce maximal agonism of 5-HT2A receptors and hallucinogenic behavioral effects. Furthermore, we established strategies for reducing the hallucinogenic and cardiotoxic potential of LSD and identified UCD0094 and UCD0076 as ergologs with improved safety profiles. In stark contrast to LSD, UCD0076 exhibits preference for activating 5-HT2C receptors over other 5-HT2 receptors and produces antipsychotic-like properties in mouse behavioral assays.
