Biology subjects

Roland, A.

Publications and source records attributed to Roland, A..

8 recordsLinked to original sources

bioRxiv2026

Direct observation of ATP-driven ubiquitin chain handling by Cdc48

Cdc48 (p97 or VCP in metazoans) targets polyubiquitin to selectively disassemble and degrade proteins. Cdc48 is believed to move along the ubiquitin chain towards linked proteins, but this has not been directly observed. By following single molecules in time, we find that the polypeptide branch points of ubiquitin chains are repeatedly inserted and rejected from the Cdc48 pore in ATP-driven manner, in bursts lasting up to seconds. This non-processive mode either ends by terminal substrate rejection, or advances to processive action, which drives ubiquitin unfolding in two steps, branch point translocation, and the extrusion of ubiquitin and linked protein as polypeptide loops in trans. Final retrograde movement can bring polypeptide segments back to cis. Our results establish the dynamics of ubiquitin chain handling by Cdc48, reveal key hallmarks of kinetic proofreading. We speculate that Cdc48 translocation may play a role in ubiquitin chain selection.

biophysics↗

bioRxiv2025

Cultivating microbial communities from the serpentinite-hosted Prony Bay Hydrothermal Field on different carbon sources in hydrogen-fed bioreactors

The primary source of carbon is one of the most fundamental questions regarding the development of microbial communities in serpentinite-hosted systems. The hydration of ultramafic rock to serpentinites generates hydrogen and creates hyper-alkaline conditions that deplete the environment of dissolved inorganic carbon. Metagenomic studies suggest that serpentinite-hosted microbial communities depend on the local redissolution of bicarbonate as well as on small organic molecules produced by abiotic reactions associated with serpentinization. To test these hypotheses, microbial consortia collected from the Prony Bay hydrothermal field were grown under anoxic conditions in hydrogen-fed bioreactors using bicarbonate, formate, acetate, or glycine as the sole carbon source. In contrast to glycine, the other three carbon substrates allowed the growth of microbial consortia characterized by significant enrichment of individual taxa. Surprisingly, these taxa were dominated by microbial genera characterized as aerobic rather than anaerobic as expected. We propose that an intricate feedback loop between autotrophic and heterotrophic foundation species facilitates the establishment of serpentinite-hosted shallow subsurface ecosystems. Bicarbonate-fixing Meiothermus and Hydrogenophaga, as well as formate-fixing Meiothermus, Thioalkalimicrobium, and possibly a novel genotype of Roseibaca might produce organic compounds for heterotrophs at the first trophic level. In addition, the base of the trophic network may include heterotrophic Roseibaca, Acetoanaerobium, and Meiothermus species producing CO2 from acetate for a more diverse community of autotrophs. The cultivated archaeal community is expected to recycle CH4 and CO2 between Methanomicrobiales and Methanosarcinales with putative Woesearchaeales symbionts.

microbiology↗

bioRxiv2024

Septo-hypothalamic regulation of binge-like alcohol consumption by the nociceptin system.

High intensity alcohol drinking during binge episodes overwhelmingly contributes to the socioeconomic burden created by Alcohol Use Disorders (AUD). Novel interventions are needed to add to the current therapeutic toolkit and nociceptin receptor (NOP) antagonists have shown promise in reducing heavy drinking days in patients with an AUD. However, an endogenous locus of nociceptin peptide and discrete sites of NOP action underlying this effect remains understudied. Here we show that the lateral septum (LS), a region contributing to binge drinking, is enriched in neurons expressing mRNA coding for the nociceptin peptide (Pnoc). Pnoc-expressing neurons of the LS (LSPnoc) are tuned to stimuli associated with negative valence and display increased excitability during withdrawal from binge-like alcohol drinking. LSPnoc activation was found to have aversive qualities and also potentiates binge-like drinking behavior, suggesting a convergence of circuitry that promotes aversion and drives alcohol consumption. Viral mediated tracing and functional assessment of LSPnoc projection fields revealed GABAergic synapses locally within the LS, and downstream within the lateral hypothalamus (LH) and supramammillary nucleus (SuM). Genetic deletion of NOP from the LS attenuated binge-like alcohol intake in male mice while NOP deletion from the LH and SuM decrease alcohol intake in females. Together, these findings are the first to demonstrate an endogenous population of nociceptin-expressing neurons that contributes to alcohol consumption and identifies sex-dependent modulation of alcohol drinking by NOP.

neuroscience↗

bioRxiv2023

Acute and chronic alcohol modulation of extended amygdala calcium dynamics

The central amygdala (CeA) and bed nucleus of the stria terminalis (BNST) are reciprocally connected nodes of the extended amygdala thought to play an important role in alcohol consumption. Studies of immediate-early genes indicate that BNST and CeA are acutely activated following alcohol drinking and may signal alcohol reward in nondependent drinkers, while increased stress signaling in the extended amygdala following chronic alcohol exposure drives increased drinking via negative reinforcement. However, the temporal dynamics of neuronal activation in these regions during drinking behavior are poorly understood. In this study, we used fiber photometry and the genetically encoded calcium sensor GCaMP6s to assess acute changes in neuronal activity during alcohol consumption in BNST and CeA before and after a chronic drinking paradigm. Activity was examined in the pan-neuronal population and separately in dynorphinergic neurons. BNST and CeA showed increased pan-neuronal activity during acute consumption of alcohol and other fluid tastants of positive and negative valence, as well as highly palatable chow. Responses were greatest during initial consummatory bouts and decreased in amplitude with repeated consumption of the same tastant, suggesting modulation by stimulus novelty. Dynorphin neurons showed similar consumption-associated calcium increases in both regions. Following three weeks of continuous alcohol access (CA), calcium increases in dynorphin neurons during drinking were maintained, but pan-neuronal activity and BNST-CeA coherence were altered in a sex-specific manner. These results indicate that BNST and CeA, and dynorphin neurons specifically, are engaged during drinking behavior, and activity dynamics are influenced by stimulus novelty and chronic alcohol.

neuroscience↗

bioRxiv2023

Corticotropin Releasing Factor in the Bed Nucleus of the Stria Terminalis modulates the behavioral consequences of unpredictable threat

Fear responses to perceived danger are critical for survival, as they prompt the individual to respond to threats and avoid harm. However, excessive fear can impede normal biological processes and become harmful. This study investigates the neural mechanisms underlying two distinct forms of fear--phasic and sustained--in male and female mice, with a focus on the bed nucleus of the stria terminalis (BNST) and corticotropin-releasing factor (CRF) signaling. Phasic fear is characterized by immediate responses to clear threats, while sustained fear is driven by ambiguous or uncertain cues and persists longer. Using rodent models, we found that sustained fear, modeled by partial fear conditioning, induced greater arousal and BNST activity in males, especially during ambiguous threat cues. In contrast, females exhibited reduced BNST and BNSTCRF activity, highlighting significant sex differences in fear learning and expression. Additionally, CRF is crucial for appropriate fear response in females, as CRF knockdown led to increased fear responses, but had no effect in males. These sex-specific differences could help inform the development of targeted treatments for anxiety and trauma-related disorders, which disproportionately affect women.

neuroscience↗

bioRxiv2022

Diurnality shapes the visual opsin genes of colorful Neotropical frogs

Amphibians are ideal for studying visual system evolution because their biphasic (aquatic and terrestrial) life history and ecological diversity expose them to a broad range of visual conditions. Here we evaluate signatures of selection on visual opsin genes across Neotropical anurans and focus on three diurnal clades that are well-known for the concurrence of conspicuous colors and chemical defense (i.e., aposematism): poison frogs (Dendrobatidae), Harlequin toads (Bufonidae: Atelopus), and pumpkin toadlets (Brachycephalidae: Brachycephalus). We found evidence of positive selection on 44 amino acid sites in LWS, SWS1, SWS2, and RH1 opsin genes, of which one in LWS and two in RH1 have been previously identified as spectral tuning sites in other vertebrates. Given that anurans have mostly nocturnal habits, the patterns of selection revealed new sites that might be important in spectral tuning for frogs, potentially for adaptation to diurnal habits and for color-based intraspecific communication. Furthermore, we provide evidence that SWS2, normally expressed in rod cells in amphibians, has likely been lost in the ancestor of Dendrobatidae, suggesting that under low-light levels, dendrobatids have inferior wavelength discrimination compared to other frogs. This loss might follow the origin of diurnal activity in dendrobatids and could have implications for their chemical ecology, biodiversity, and behavior. Our analyses show that assessments of opsin diversification in understudied groups could expand our understanding of the role of sensory system evolution in ecological adaptation.

evolutionary biology↗

bioRxiv2022

Alcohol dependence modifies brain networks activated during abstinence and reaccess: a c-fos-based analysis in mice

High-level alcohol consumption causes neuroplastic changes in the brain that lead to negative affective and somatic symptoms when alcohol is withdrawn, promoting relapse drinking. We have some understanding of these plastic changes in defined brain circuits and cell types, but unbiased approaches are needed to explore broader patterns of adaptations. Here, we employed whole-brain c-fos mapping and network analysis to assess how brain-wide patterns of neuronal activity are altered during acute alcohol abstinence and reaccess in a well-characterized model of alcohol dependence. Mice underwent four cycles of chronic intermittent ethanol vapor exposure (CIE) with alternating weeks of voluntary alcohol drinking, and a subset of mice underwent forced swim stress (FSS) prior to drinking sessions to further escalate alcohol consumption. After four CIE cycles, brains were collected from mice in each group either 24 hours (abstinence) or immediately following a one-hour period of alcohol reaccess. Brains from CIE mice during acute abstinence displayed widespread neuronal activation relative to those from AIR mice, independent of FSS, and this increase in c-fos was reversed by reaccess drinking. For network analysis, mice were then classified as high or low drinkers (HD or LD). We computed Pearson correlations for all pairs of brain regions and used graph theoretical methods to identify changes in network properties associated with high-drinking behavior. Network modularity, a measure of network segregation into communities, was increased in HD mice after alcohol reaccess relative to abstinence. Within-community strength and diversity measures were computed for each region and condition, and highly coactive regions were identified. One high-diversity region, the cortical amygdala (COA), was further interrogated using a chemogenetic approach. COA silencing in CIE mice reduced voluntary drinking, validating our network analysis and indicating that this region may play an important but underappreciated role in alcohol dependence.

neuroscience↗

bioRxiv2020

Weak catch bonds make strong networks

Molecular catch bonds are ubiquitous in biology and well-studied in the context of leukocyte extravasion1, cellular mechanosensing2,3, and urinary tract infection4. Unlike normal (slip) bonds, catch bonds strengthen under tension. The current paradigm is that this remarkable ability enables cells to increase their adhesion in fast fluid flows1,4, and hence provides strength-on-demand. Recently, cytoskeletal crosslinkers have been discovered that also display catch bonding5-8. It has been suggested that they strengthen cells, following the strength-on-demand paradigm9,10. However, catch bonds tend to be weaker compared to regular (slip) bonds because they have cryptic binding sites that are often inactive11-13. Therefore, the role of catch bonding in the cytoskeleton remains unclear. Here we reconstitute cytoskeletal actin networks to show that catch bonds render them both stronger and more deformable than slip bonds, even though the bonds themselves are weaker. We develop a model to show that weak binding allows the catch bonds to mitigate crack initiation by moving from low- to high-tension areas in response to mechanical loading. By contrast, slip bonds remain trapped in stress-free areas. We therefore propose that the mechanism of catch bonding is typified by dissociation-on-demand rather than strength-on-demand. Dissociation-on-demand can explain how both cytolinkers5-8,10,14,15 and adhesins1,2,4,12,16-20 exploit continuous redistribution to combine mechanical strength with the adaptability required for movement and proliferation21. Our findings provide a new perspective on diseases where catch bonding is compromised11,12 such as kidney focal segmental glomerulosclerosis22,23, caused by the -actinin-4 mutant studied here. Moreover, catch bonds provide a route towards creating life-like materials that combine strength with deformability24.

biophysics↗