Biology subjects

Barrett, N.

Publications and source records attributed to Barrett, N..

7 recordsLinked to original sources

bioRxiv2026

Endocytosis and Compartmentalized Intracellular Signaling of the Prostaglandin Receptor EP4 Mediate Pain

Prostaglandin E2 (PGE2) is recognized as a major mediator of inflammatory pain. However, the intracellular signaling mechanisms by which PGE2 mediates pain remain unclear. Here, we show that pain-like responses evoked by PGE2 in dorsal root ganglion (DRG) nociceptors are mediated by internalization and compartmentalized signaling of the EP4 receptor. The EP4-selective agonist L-902,688 induced immediate nocifensive behavior and prolonged mechanical allodynia in mice and sensitized isolated DRG nociceptors. Pharmacological inhibition of clathrin- and dynamin-mediated endocytosis (using pitstop2 and dyngo4a) and siRNA knockdown of Dnm1 prevented EP4-induced nociception and sensitization, implicating receptor trafficking in pain signaling. Using genetically-encoded biosensors, we monitored EP4 trafficking and downstream signaling within subcellular compartments of HEK293 cells. PGE2 stimulated dynamin- and {beta}-arrestin-dependent EP4 trafficking from the plasma membrane to early, late and recycling endosomes and Golgi apparatus, and mobilized intracellular EP4 pools from the endoplasmic reticulum. PGE2 induced the assembly of EP4, G proteins and {beta}-arrestin signaling complexes in endosomes and the Golgi apparatus. Inhibition of EP4 endocytosis suppressed intracellular cAMP production and ERK activation. Our findings reveal that EP4-mediated nociceptive signaling originates from intracellular compartments and suggest that modulating EP4 internalization and subcellular signaling dynamics could offer a novel strategy for inflammatory pain management.

cell biology↗

bioRxiv2025

Soluble SORL1 in cerebrospinal fluid as a marker for functional impact of rare SORL1 variants.

BackgroundAs part of the retromer, sortilin-related receptor (SORL1) sorts cargo proteins away from the endosome to the trans-Golgi network or to the cell surface, where SORL1 is cleaved into sSORL1 and shed into the interstitial fluid and CSF. SORL1s cargo includes APP and A{beta}, which may explain why protein-truncating genetic variants (PTVs) in SORL1 are observed almost exclusively in Alzheimers Disease (AD) patients, and that rare, predicted pathogenic missense variants have been associated with a 10-fold increased risk of AD. However, functional evidence supporting variant pathogenicity is warranted. Here we investigated whether soluble SORL1 (sSORL1) concentrations in cerebrospinal fluid (CSF) offer a potential in vivo biomarker to support impaired SORL1 function in variant carriers. MethodsUsing an ELISA assay for SORL1 (ABCAM), we determined sSORL1 concentrations in CSF from 218 participants of the Alzheimer Dementia Cohort (ADC) (54% females). We compared sSORL1 in CSF derived from 90 carriers of diverse SORL1 variants with concentrations observed in 78 SORL1-WT AD patients, and 50 SORL1-WT controls for whom CSF-pTau-181, CSF-tTau, CSF-A{beta}42 concentrations were available. In a subset of 36 individuals, we used Western blotting (WB) to validate sSORL1 concentrations as determined by ELISA. ResultsCSF-sSORL1 concentrations did not differ between SORL1-WT AD patients and controls. While CSF-sSORL1 did not correlate with CSF-A{beta}42 concentrations in SORL1-WT AD patients (p=0.62), it correlated with sCSF-ptau-181 (p=9.7x10-6). The mean CSF-sSORL1 concentration in the SORL1 WT AD cases and controls was 466 pg/ml, with wide variance (SD = 133). Comparatively, concentrations were significantly lower in PTV carriers (260 pg/ml, p=3.2x10-7) and in carriers of predicted damaging SORL1 missense variants (323 pg/ml, p=2.4x10-7). CSF-sSORL1 concentrations measured by ELISA correlated strongly with concentrations estimated by WB ({rho}=0.552; p=5.0x10-4). ConclusionCSF-sSORL1 increases with CSF-ptau, suggesting that increased SORL1-retromer activity may serve to rescue cellular stress associated with AD-related processes. However, impairing SORL1 genetic variants may preclude SORL1 trafficking to the cell surface, as supported by lower CSF-sSORL1 protein concentrations in carriers. While further refinements are necessary, we present first evidence for the applicability of ELISA-based quantification of sSORL1 in CSF to evaluate the functional impact of rare SORL1 variants.

neuroscience↗

bioRxiv2025

Assessing predictive accuracy of species abundance models in dynamic systems

Cascading human pressures and environmental change are affecting the natural dynamics of animal populations. Forecasting population abundances from time-series data provides an important avenue for testing competing ecological theories, and for supporting conservation planning and sustainable use, yet changing system dynamics may lead to erroneous predictions. Predictions from a model fitted and tested on historical system dynamics may become irrelevant if system dynamics change. Here we describe methods to test forecast skill in a rapidly changing system where model parameters are likely to be non-stationary. We presented two ways to split time-series into training and test datasets so that training data were: 1) contemporary to the testing data ( modern split), and 2) not contemporary to the testing data ( legacy split). As a case-study, we use animal abundance data from a 30-year time-series from a global warming hotspot. We tested our approach on four temperate reef species with different temporal trends. The case-study and simulation tests confirmed larger forecast errors in legacy split when compared to the modern split. We found that the legacy split had errors that could be more than for times larger for a species that had a rapid collapse in abundance and non-stationary population dynamics. As expected for the species with rapid collapse, the legacy split estimated much higher forecast error than the modern split. Our approach is applicable to a large range of species and systems, including fisheries and threatened species population monitoring, where rapidly changing environments present threats to both the species and management efficacy. Accumulated lessons from across species and systems should shed light on critical generalities that precede broader ecosystem change.

ecology↗

bioRxiv2024

Leukaemia cell intrinsic and extrinsic factors cooperate to facilitate the survival and proliferation of KMT2A-rearranged B-ALL in the CNS niche.

Infant B-cell acute lymphoblastic leukaemia (B-ALL) is a rare, aggressive entity characterised by KMT2A rearrangements and poor outcomes. One of the unique features of KMT2A-rearranged infant ALL that contributes to these poor outcomes is a particularly high rate of central nervous system (CNS) involvement. There is a broad lack of understanding regarding the molecular processes and immune environment in CNS ALL. This hinders the development of targeted therapies for CNS ALL, which is increasingly essential given the potentially reduced efficacy of current immunotherapies in this specialised environment. In this study, we used an immune-competent KMT2A-AFF1+ infant B-ALL murine model to explore the cell-intrinsic and cell-extrinsic mechanisms that underpin this clinically significant complication. We show novel functional impacts on leukaemia propagating cells following exposure to the CNS niche which results in unique leukaemia repopulation dynamics. Transcriptomic and immune cell profiling by niche showed differences in the immune microenvironment between the CNS and bone marrow niches. The CNS niche demonstrates supressed T cell and macrophage activity which may be part of a wider CNS niche-specific immune escape mechanism. Our transcriptomic comparisons by niche also led us to explore the role of PI3K pathway activation in the propagation of leukaemia cells within the CNS niche. We identify miR-93 as a possible master regulator of this process. The importance of miR-93 is emphasised as it is shown to be upregulated in CNS leukaemia cells across multiple murine KMT2A-AFF1 B-ALL model systems and in primary KMT2A-AFF1 B-ALL patient samples. We conclude by showing impaired CNS engraftment of leukaemia cells upon miR-93 knockdown, cementing its importance in CNS leukaemia biology and opening up new CNS-specific therapeutic opportunities.

cancer biology↗

bioRxiv2023

A microRNA expression signature in infant t(4;11) MLL-AF4+ BCP-ALL uncovers novel therapeutic targets

Infants and children with MLL-AF4+ leukemia have an urgent need for more efficient and less aggressive therapy. In this study, we studied three microRNAs that are downregulated in MLL-AF4+ B-cell precursor acute lymphoblastic leukemia (BCP-ALL): miR-194, miR-99b and miR-125a-5p. When overexpressed, all three microRNAs impaired the survival of MLL-AF4+ leukemic blasts and the maintenance of MLL-AF4+ BCP-ALL. We identified microRNA target genes responsible for this phenotype that are upregulated in MLL-AF4+ BCP-ALL: CA5B, PPP3CA and PPP2R5C. Using CRISPR-Cas9 and specific inhibitors, we confirmed that CA5B, PPP3CA and PPP2R5C downregulation/inhibition severely compromised the proliferation and survival of MLL-AF4+ leukemic blasts. Importantly, CA5B, PPP3CA and PP2A inhibition by acetazolamide, tacrolimus and LB-100, respectively, showed high toxicity towards MLL-AF4+ leukemic blasts and reduced leukemia burden in vivo. This study highlights how the unique microRNA expression signature of patients with MLL-AF4+ BCP-ALL can be used to uncover novel therapeutic avenues and accelerate drug repurposing. Statement of significanceThere is an urgent need to identify novel therapeutic avenues for patients with MLL-AF4+ BCP-ALL that are more effective and less aggressive. This study identified three clinically available drugs (acetazolamide, tacrolimus and LB-100) with high and selective toxicity towards MLL-AF4+ leukemic cells.

cancer biology↗

bioRxiv2022

Type 2 Inflammation Drives an Airway Basal Stem Cell Program Through Insulin Receptor Substrate Signaling

BackgroundChronic rhinosinusitis with nasal polyposis (CRSwNP) is a type 2 (T2) inflammatory disease associated with an increased number of airway basal epithelial cells (BCs). Recent studies have identified transcriptionally distinct BCs, but functional data are lacking and the molecular pathways that support or inhibit human BC proliferation and differentiation are largely unknown. ObjectiveTo determine the role of T2 cytokines in regulating airway BCs MethodsSingle cell and bulk RNA-sequencing of sinus and lung airway epithelial cells was analyzed. Human sinus BCs were stimulated with IL-4 and IL-13 in the presence and absence of IL4R inhibitors. Confocal analysis of human sinus tissue and murine airway was performed. Murine BC subsets were sorted for RNA sequencing and functional assays. Fate labeling was performed in a murine model of tracheal injury and repair. ResultsHere we find two subsets of BCs in human and murine respiratory mucosa distinguished by the expression of BC adhesion molecule (BCAM). BCAM expression identifies airway stem cells among P63+KRT5+NGFR+ BCs. In the sinonasal mucosa, BCAMhi BCs expressing TSLP, IL33, CCL26, and the canonical BC transcription factor TP63 are increased in patients with CRSwNP. In cultured BCs, IL-4/13 increases expression of BCAM and TP63 through an Insulin Receptor Substrate (IRS)-dependent signaling pathway that is increased in CRSwNP. ConclusionsThese findings establish BCAM as a marker of airway stem cells among the BC pool and demonstrate that airway epithelial remodeling in T2 inflammation extends beyond goblet cell metaplasia to the support of a BC stem state poised to perpetuate inflammation. CAPSULE SUMMARYType 2 cytokines drive an airway stem cell program through IRS signaling KEY MESSAGESO_LITwo subsets of airway BCs have distinct transcriptional signatures and function C_LIO_LIHigh levels of BCAM expression mark the earliest BC progenitor C_LIO_LIIL-4 and IL-13 upregulate BCAM and P63 in an IRS-dependent fashion which prevents BC differentiation to secretory epithelial cells C_LIO_LIBCAMhi BCs are increased in CRSwNP C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=176 SRC="FIGDIR/small/512129v1_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@16e78e8org.highwire.dtl.DTLVardef@1c40393org.highwire.dtl.DTLVardef@1c6bc4aorg.highwire.dtl.DTLVardef@73b9db_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2020

The physical form of microbial ligands bypasses the need for dendritic cell migration to stimulate adaptive immunity

A central paradigm of immunology is that the innate immune system first detects infectious agents in peripheral tissues, shortly after a pathogen has breached an epithelial barrier. This detection event is mediated by pattern recognition receptors in phagocytes, which then migrate to draining lymph nodes (dLNs), where information of a microbial encounter is conveyed to T and B lymphocytes to generate adaptive immunity. Through the study of fungal moieties, we present data that challenge this model. We found that soluble fungal polysaccharides are immunosilent in the periphery, but become potent immunogens in the dLN. These ligands completely bypass the need of phagocyte migration and, instead, directly activate an immune response that is most similar to those that typify viral infections. These data establish a class of microbial products that violate a central tenet of the immunological lexicon and illustrate that the physical form (not just the chemical structure) impacts innate and adaptive immunity.

immunology↗