Biology subjects

O'Brien, S. L.

Publications and source records attributed to O'Brien, S. L..

5 recordsLinked to original sources

bioRxiv2026

Toward welfare indicators: leg condition and aversive stimuli modulate defensive behavior in Opilones

The history of invertebrate use in research and their growing use in managed settings highlight the need for validated behavioral indicators of welfare, yet these remain poorly understood across taxa. The arachnid group Opiliones (harvestmen or daddy long-legs) is an ideal group for identifying welfare indicators, given their well-characterized defensive behavior, including the common strategy of leg autotomy. The goal of this project was to identify candidate behavioral welfare indicators for Prionostemma sp. 1 in the Neotropical rainforest. We brought field-collected individuals with different leg conditions to the lab and briefly exposed them to an aversive stimulus (a gentle squeeze and release) paired with an assigned substrate (either rock or sand). A rewarding stimulus (food) was provided on the alternate substrate. We found no evidence of preference for roosting on the substrate associated with the rewarding stimulus, nor avoidance of the substrate associated with the aversive stimulus. Thus, evidence for associative learning was not supported. Additionally, substrate use did not differ based on leg condition (intact, missing 1-2 legs, or missing sensory legs). After an aversive stimulus, fleeing was consistently the most common response throughout 5 days. In contrast, the frequency of bobbing increased while the frequency of escaping decreased over trials. Individuals with all legs tended to escape more often than those missing legs, but neither the number nor the type of missing legs substantially improved predictions of behavioral responses. Overall, fleeing and bobbing may serve as behavioral indicators of negative welfare states, whereas the observed absence of exploratory tapping following the aversive stimulus suggests that this behavior may indicate neutral or positive welfare states. As one of the first investigations of welfare indicators in wild arachnids, this study provides novel insights into how defensive behaviors and physical condition may inform assessments of invertebrate welfare, laying the groundwork for future validation of behavioral indicators.

animal behavior and cognition↗

bioRxiv2026

Lactate promotes IL-8 secretion in human alveolar macrophages through GPR132 and lipid metabolic reprogramming

Alveolar macrophages are the primary lung immune cell. They play a crucial role in both maintenance of tissue homeostasis and the initiation of inflammation, secreting multiple immune mediators including the chemokine interleukin-8 (IL-8). Inflammatory settings are often characterised by tissue hypoxia, increased glycolytic rates and lactate secretion, yet how lactate influences alveolar macrophage function remains unclear. Here we investigated how lactate, once considered a waste-product, shapes alveolar macrophage function. To do so, primary human alveolar macrophages (hAMs) and a combination of flow cytometry, ELISA/Luminex, western blot, light microscopy, bioluminescence resonance energy transfer (BRET) and analysis of publicly available datasets were used to understand the role of lactate in lung pathological environments. We demonstrate that hAMs sense extracellular lactate via the expression of different lactate transporters (e.g. MCT1, MCT4) and receptors (i.e. GPR132). Lactate treatment of hAMs increased IL-8 secretion in a MCT1-dependent manner. Lipid metabolism and lipid droplet formation, as well as direct lactate-driven GPR132 signalling were required for lactate-dependent IL-8 release. Our findings uncover a previously unrecognised dual mechanism by which lactate orchestrates immune regulation in hAMs. Specifically, lactate-driven IL-8 production requires two distinct lactate-driven processes: uptake via MCT1, which reprograms lipid metabolism, and signaling through the lactate receptor GPR132. This functional integration of lactate transport and receptor-mediated signaling provides new mechanistic insight into lactates role in hAM biology and highlights potential targets for therapeutic intervention.

immunology↗

bioRxiv2024

Exploring human rare disease variants from a multidimensional perspective illuminates receptor - G protein coupling diversity

G protein-coupled receptors (GPCRs) are transmembrane proteins capable of detecting signals as diverse as odours, neurotransmitters, and hormones. Upon activation, receptor signalling converges onto four G protein subtypes to regulate intracellular responses. Therefore, variation in a single G protein gene can potentially impact the function of numerous receptors. In this work, we have performed a multidimensional study of rare disease mutations in Gs, a prototypical G protein. By integrating data from 3D structures, GPCR / G protein functional pairings, transcriptomics, biophysics, and molecular dynamics with systems pharmacology modelling, our results reveal why mutations impairing receptor / Gs coupling result in highly specific context-based signalling defects. Furthermore, we show that mutations leading to the same rare disease can alter different signal transduction steps, highlighting the importance of patient-specific treatment strategies. By closely dissecting G protein coupling, our study provides a blueprint to interrogate GPCR pathway signalling diversity in different (patho)physiological contexts.

systems biology↗

bioRxiv2023

A new paradigm of intracrine free fatty acid receptor 4 signaling at lipid droplets

G protein-coupled receptors (GPCRs), once thought to be active exclusively at the plasma membrane, have been shown to signal from multiple intracellular membrane compartments, including endosomes and the Golgi. However, the potential occurrence and functional relevance of intracellular signaling for the emerging family of metabolite-sensing GPCRs is largely unknown. Here, we used live-cell imaging, bioluminescence resonance energy transfer (BRET) measurements, and functional readouts to investigate signal compartmentalization of the free fatty acid receptor 4 (FFA4), a prototypical metabolite-sensing GPCR that is activated by medium- and long-chain free fatty acids (FFAs). Unexpectedly, we show that FFA4 largely resides on intracellular membranes that are intimately associated with lipid droplets in adipocytes. Upon lipolysis induction, the released FFAs rapidly bind to and activate this intracellular pool of FFA4, leading to local Gi/o coupling and inhibition of cAMP production in the vicinity of lipid droplets. This provides a spatiotemporally confined negative feedback mechanism allowing individual lipid droplets to rapidly adjust their lipolysis rate. Our results reveal a novel intracrine signaling modality by a prototypical metabolite-sensing GPCR and identify a new lipid-droplet-associated signaling hub implicated in the rapid regulation of lipid metabolism, with important implications for adipocyte physiology and pharmacology.

pharmacology and toxicology↗

bioRxiv2022

Single-molecule analysis of receptor-beta-arrestin interactions in living cells

{beta}-arrestin plays a key role in G protein-coupled receptor (GPCR) signaling and desensitization. Despite recent structural advances, the mechanisms that govern receptor-{beta}-arrestin interactions at the plasma membrane of living cells remain elusive. Here, we combine single-molecule microscopy with molecular dynamics simulations to dissect the complex sequence of events involved in {beta}-arrestin interactions with both receptors and the lipid bilayer. In contrast to the currently widely accepted model, we show that {beta}-arrestin spontaneously inserts into the lipid bilayer and transiently interacts with receptors via lateral diffusion on the plasma membrane. Moreover, we show that following receptor interaction, the plasma membrane stabilizes {beta}-arrestin in a membrane-bound, active-like conformation, allowing it to diffuse to clathrin coated pits separately from the activating receptor. These results challenge our current understanding of {beta}-arrestin function at the plasma membrane, revealing a new critical role for {beta}-arrestin pre-association with the lipid bilayer in facilitating its interactions with receptors and subsequent activation.

cell biology↗