Biology subjects

Nguyen, K.

Publications and source records attributed to Nguyen, K..

At least 55 records · Page 3Linked to original sources

bioRxiv2024

Directed evolution of the multicopper oxidase laccase for cell surface proximity labeling and electron microscopy

Enzymes that oxidize aromatic substrates have shown utility in a range of cell-based technologies including live cell proximity labeling (PL) and electron microscopy (EM), but are associated with drawbacks such as the need for toxic H2O2. Here, we explore laccases as a novel enzyme class for PL and EM in mammalian cells. LaccID, generated via 11 rounds of directed evolution from an ancestral fungal laccase, catalyzes the one-electron oxidation of diverse aromatic substrates using O2 instead of toxic H2O2, and exhibits activity selective to the surface plasma membrane of both living and fixed cells. We show that LaccID can be used with mass spectrometry-based proteomics to map the changing surface composition of T cells that engage with tumor cells via antigen-specific T cell receptors. In addition, we use LaccID as a genetically-encodable tag for EM visualization of cell surface features in mammalian cell culture and in the fly brain. Our study paves the way for future cell-based applications of LaccID.

biochemistry↗

bioRxiv2024

Stimulus history, not expectation, drives sensory prediction errors in mammalian cortex

Hierarchical predictive coding (HPC) models have recently flourished in neuroscience1-9. Feedforward and feedback processing are at the heart of HPC models. Previous experimental studies using fMRI, EEG/MEG, and LFP9-11 do not reliably resolve feedback modulation from local computations and feedforward outputs. Here, using open-science8, multi-species, multi-area, high-density12, laminar neurophysiology13, we empirically test whether hierarchical predictive coding is a key component shaping cortical processing of visual stimuli. To isolate visual information processing and eliminate motor/reward confounders9-11, we use a no-report task. Our task leveraged so-called global oddballs (GO) as unpredictable, deviant stimuli that circumvent low-level adaptation. We examined their responses relative to local oddballs (LO) that we habituated into highly predictable priors. Four surprising findings in this dataset challenge many existing hierarchical predictive coding models. First, GO responses were exclusive to higher-order, more cognitive areas rather than early-to-mid visual cortex. Second, inhibitory interneuron-targeted optogenetics in primates and mice and waveform shape analysis in primates revealed no evidence that predictive suppression was implemented via these interneurons. Third, highly predictable LO responses dominated in over 50% of all neurons, including in higher-order cortex, which should have anticipated them, indicating limited evidence for predictive suppression. Lastly, prediction error responses evoked by GOs did not evoke feedforward processing. These results reveal circuit dynamics that govern how prediction shapes visual processing, motivating more neurally constrained predictive processing models.

neuroscience↗

bioRxiv2024

Cryo-EM visualizes multiple steps of dynein activation pathway

Cytoplasmic dynein-1 (dynein) is an essential molecular motor controlled in part by autoinhibition. We recently identified a structure of partially autoinhibited dynein bound to Lis1, a key dynein regulator mutated in the neurodevelopmental disease lissencephaly. This structure provides an intermediate state in dyneins activation pathway; however, other structural information is needed to fully explain Lis1 function in dynein activation. Here, we used cryo-EM and samples incubated with ATP for different times to reveal novel conformations that we propose represent intermediate states in the dyneins activation pathway. We solved sixteen high-resolution structures, including seven distinct dynein and dynein-Lis1 structures from the same sample. Our data also support a model in which Lis1 relieves dynein autoinhibition by increasing its basal ATP hydrolysis rate and promoting conformations compatible with complex assembly and motility. Together, this analysis advances our understanding of dynein activation and the contribution of Lis1 to this process.

biophysics↗

bioRxiv2024

Mutant p53 Exploits Enhancers to Elevate Immunosuppressive Chemokine Expression and Impair Immune Checkpoint Inhibitors in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer without effective treatments. It is characterized by activating KRAS mutations and p53 alterations. However, how these mutations dysregulate cancer-cell-intrinsic gene programs to influence the immune landscape of the tumor microenvironment (TME) remains poorly understood. Here, we show that p53R172H establishes an immunosuppressive TME, diminishes the efficacy of immune checkpoint inhibitors (ICIs), and enhances tumor growth. Our findings reveal that the upregulation of the immunosuppressive chemokine Cxcl1 mediates these pro-tumorigenic functions of p53R172H. Mechanistically, we show that p53R172H associates with the distal enhancers of the Cxcl1 gene, increasing enhancer activity and Cxcl1 expression. p53R172H occupies these enhancers in an NF-{kappa}B-pathway-dependent manner, suggesting NF-{kappa}Bs role in recruiting p53R172H to the Cxcl1 enhancers. Our work uncovers how a common mutation in a tumor-suppressor transcription factor appropriates enhancers, stimulating chemokine expression and establishing an immunosuppressive TME that diminishes ICI efficacy in PDAC. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=100 SRC="FIGDIR/small/609802v1_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@b2354dorg.highwire.dtl.DTLVardef@1c96300org.highwire.dtl.DTLVardef@829f26org.highwire.dtl.DTLVardef@19e7d2e_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2024

Brain-Engrafted Monocyte-derived Macrophages from Blood and Skull-Bone Marrow Exhibit Distinct Identities from Microglia

Microglia are thought to originate exclusively from primitive macrophage progenitors in the yolk sac (YS) and to persist throughout life without much contribution from definitive hematopoiesis. Here, using lineage tracing, pharmacological manipulation, and RNA-sequencing, we elucidated the presence and characteristics of monocyte-derived macrophages (MDMs) in the brain parenchyma at baseline and during microglia repopulation, and defined the core transcriptional signatures of brain-engrafted MDMs. Lineage tracing mouse models revealed that MDMs transiently express CD206 during brain engraftment as CD206+ microglia precursors in the YS. We found that brain-engrafted MDMs exhibit transcriptional and epigenetic characteristics akin to meningeal macrophages, likely due to environmental imprinting within the meningeal space. Utilizing parabiosis and skull transplantation, we demonstrated that monocytes from both peripheral blood and skull bone marrow can repopulate microglia-depleted brains. Our results reveal the heterogeneous origins and cellular dynamics of brain parenchymal macrophages at baseline and in models of microglia depletion.

immunology↗

bioRxiv2024

Environmental differences impact Acinetobacter baumannii phage isolation and infectivity

With the global rise of antimicrobial resistance, phage therapy is increasingly re-gaining traction as a strategy to treat bacterial infections. For phage therapy to be successful however, we first need to isolate appropriate candidate phages for both clinical and experimental research. Acinetobacter baumannii is an opportunistic pathogen known for its ability to rapidly evolve resistance to antibiotics, making it a prime target for phage therapy. Yet phage isolation is often hampered by A. baumanniis ability to rapidly switch between capsular states. Here, we report the discovery and structural characterisation of a novel lytic phage, Mystique. This phage was initially isolated against the wild-type AB5075: a commonly used clinical model strain against which no phage has previously been readily available for the capsulated form. When screening Mystique on 103 highly diverse isolates of A. baumannii, we found that it has a broad host range, being able to infect 85.4% of all tested strains when tested on bacterial lawns - a host range which expanded to 91.3% when tested in liquid culture. This variation between solid and liquid environments on phage infectivity was also observed for several other phages in our collection that were assumed unable to infect AB5075, and capsule negative mutants that initially seemed completely resistant to Mystique proved susceptible when assayed in liquid. Overall, through the discovery of a novel phage we demonstrate how environmental differences can drastically impact phage infectivity with important consequences for phage isolation and characterisation efforts. Author summaryBacterial infections caused by Acinetobacter baumannii are a major global health concern due to high antibiotic resistance, earning it a critical priority pathogen ranking by the WHO. Phage therapy is resurging as a treatment option, with some success against A. baumannii. However, the wild-type clinical model strain used to assess new therapies lacks an available phage, and isolating phages for A. baumannii is challenging due to its complex capsule. Here, we report the discovery of a novel lytic phage, Mystique, which exhibits a broad host range, infecting 94 out of 103 tested A. baumannii strains. We conducted genomic sequencing and structural analysis to fully characterise Mystique. Additionally, we found that the testing environment significantly impacts results; some phages that do not form plaques on bacterial lawns can still infect and amplify in liquid cultures of the same strain. Moreover, mutants resistant to Mystique based on plaque assays were susceptible in liquid culture assays. This work underscores the necessity of a multifaceted approach for phage isolation and characterisation, as traditional phage assays may not be sufficient for studying bacteria-phage dynamics in certain bacteria such as A. baumannii.

microbiology↗

bioRxiv2024

Preventing trogocytosis by cathepsin B inhibition augments CAR T cell function

Chimeric antigen receptor (CAR) T cell therapy has shown remarkable efficacy in cancer treatment. Still, most patients receiving CAR T cells relapse within 5 years of treatment. CAR-mediated trogocytosis (CMT) is a potential tumor escape mechanism in which cell surface proteins transfer from tumor cells to CAR T cells. CMT results in the emergence of antigen-negative tumor cells, which can evade future CAR detection, and antigen-positive CAR T cells, which has been suggested to cause CAR T cell fratricide and exhaustion. Whether CMT indeed causes CAR T cell dysfunction and the molecular mechanisms conferring CMT remain unknown. Using a selective degrader of trogocytosed antigen in CAR T cells, we show that the presence of trogocytosed antigen on the CAR T cell surface directly causes CAR T cell fratricide and exhaustion. By performing a small molecule screening using a custom high throughput CMT-screening assay, we found that the cysteine protease cathepsin B is essential for CMT and that inhibition of cathepsin B is sufficient to prevent CAR T cell fratricide and exhaustion, leading to improved long-term CAR T cell persistence and anti-tumor activity. Our data demonstrate that it is feasible to separate CMT from cytotoxic activity, that CAR T cell persistence, a key factor associated with clinical CAR T cell efficacy, is directly linked to cathepsin B activity in CAR T cells, and that it is possible to improve CAR T cell function through selective inhibition of CMT. One sentence summary: CAR-mediated trogocytosis is mediated by the cysteine protease cathepsin B and directly causes CAR T cell exhaustion and fratricide. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=116 SRC="FIGDIR/small/598379v3_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@5c058dorg.highwire.dtl.DTLVardef@1707fa7org.highwire.dtl.DTLVardef@ccdff1org.highwire.dtl.DTLVardef@82800b_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2024

Eye movements reveal age differences in how arousal modulates saliency priority but not attention processing speed

The arousal-biased competition theory posits that inducing arousal increases attentional priority of salient stimuli while reducing priority of non-pertinent stimuli. However, unlike in young adults, older adults rarely exhibit shifts in priority under increased arousal, and prior studies have proposed different neural mechanisms to explain how arousal differentially modulates selective attention in older adults. Therefore, we investigated how the threat of unpredictable shock differentially modulates attentional control mechanisms in young and older adults by observing eye movements. Participants completed two oculomotor search tasks in which the salient distractor was typically captured by attention (singleton search) or proactively suppressed (feature search). We found that arousal did not modulate attentional priority for any stimulus among older adults nor affect the speed of attention processing in either age group. Furthermore, we observed that arousal modulated pupil sizes and found a correlation between evoked pupil responses and oculomotor function. Our findings suggest age differences in how the locus coeruleus-noradrenaline system interacts with neural networks of attention and oculomotor function. Highlights- Increased arousal modulates attention saliency priority but not processing speed - Older adults do not exhibit shifts in stimulus priority under elevated arousal - Proactive suppression of salient stimuli persists even during increased arousal - Threat of unpredictable shock increases pupil sizes and decreases evoked responses - Eye movements may be able to help assess locus coeruleus function

neuroscience↗

bioRxiv2024

Multi-Omics after O-GlcNAc Alteration Identifies Cellular Processes Working Synergistically to Promote Aneuploidy

Pharmacologic or genetic manipulation of O-GlcNAcylation, an intracellular, single sugar post-translational modification, are difficult to interpret due to the pleotropic nature of O-GlcNAc and the vast signaling pathways it regulates. To address this issue, we employed either OGT (O-GlcNAc transferase), OGA (O-GlcNAcase) liver knockouts, or pharmacological inhibition of OGA coupled with multi-Omics analysis and bioinformatics. We identified numerous genes, proteins, phospho-proteins, or metabolites that were either inversely or equivalently changed between conditions. Moreover, we identified pathways in OGT knockout samples associated with increased aneuploidy. To test and validate these pathways, we induced liver growth in OGT knockouts by partial hepatectomy. OGT knockout livers showed a robust aneuploidy phenotype with disruptions in mitosis, nutrient sensing, protein metabolism/amino acid metabolism, stress response, and HIPPO signaling demonstrating how OGT is essential in controlling aneuploidy pathways. Moreover, these data show how a multi-Omics platform can discern how OGT can synergistically fine-tune multiple cellular pathways.

cell biology↗

bioRxiv2024

A drug cocktail of rapamycin, acarbose, and phenylbutyrate enhances resilience to features of early-stage Alzheimer's disease in aging mice

The process of aging is defined by the breakdown of critical maintenance pathways leading to an accumulation of damage and its associated phenotypes. Aging affects many systems and is considered the greatest risk factor for a number of diseases. Therefore, interventions aimed at establishing resilience to aging should delay or prevent the onset of age-related diseases. Recent studies have shown a three-drug cocktail consisting of rapamycin, acarbose, and phenylbutyrate delayed the onset of physical, cognitive, and biological aging phenotypes in old mice. To test the ability of this drug cocktail to impact Alzheimers disease (AD), an adeno-associated-viral vector model of AD was created. Mice were fed the drug cocktail 2 months prior to injection and allowed 3 months for phenotypic development. Cognitive phenotypes were evaluated through a spatial navigation learning task. To quantify neuropathology, immunohistochemistry was performed for AD proteins and pathways of aging. Results suggested the drug cocktail was able to increase resilience to cognitive impairment, inflammation, and AD protein aggregation while enhancing autophagy and synaptic integrity, preferentially in female cohorts. In conclusion, female mice were more susceptible to the development of early stage AD neuropathology and learning impairment, and more responsive to treatment with the drug cocktail in comparison to male mice. Translationally, a model of AD where females are more susceptible would have greater value as women have a greater burden and incidence of disease compared to men. These findings validate past results and provide the rationale for further investigations into enhancing resilience to early-stage AD by enhancing resilience to aging.

pathology↗

bioRxiv2024

Stepwise neofunctionalization of the NF-κB family member c-Rel during vertebrate evolution

Adaptive immunity and the five vertebrate NF-{kappa}B/Rel family members first appeared in cartilaginous fish, suggesting that divergence and specialization within the NF-{kappa}B family helped facilitate the evolution of adaptive immunity. One specialized function of the NF-{kappa}B c-Rel protein in macrophages is the activation of Il12b, which encodes a key regulator of T-cell development. We found that c-Rel is a far more potent regulator of Il12b than of any other inducible genes in macrophages, with c-Rel regulation of Il12b dependent on its heightened intrinsic DNA-binding affinity. c-Rel homodimers regulate Il12b transcription in part via motifs with little resemblance to canonical NF-{kappa}B motifs. ChIP-seq experiments further defined distinct c-Rel DNA-binding preferences genome-wide, and X-ray crystallography of a c-Rel/RelA chimeric protein identified key amino acid changes that support the unique c-Rel properties. Unexpectedly, these changes, along with the c-Rel/RelA binding affinity differences, were largely restricted to mammalian species. Together, our findings reveal how a transcription factor family member can undergo a structural transition at a late stage of vertebrate evolution, resulting in an increased intrinsic DNA binding affinity and with clear functional consequences, presumably to support the increasing complexity of immune regulation.

immunology↗

bioRxiv2024

Heterozygosity for neurodevelopmental disorder-associated TRIO variants yields distinct deficits in behavior, neuronal development, and synaptic transmission in mice

Genetic variants in TRIO are associated with neurodevelopmental disorders (NDDs) including schizophrenia (SCZ), autism spectrum disorder (ASD) and intellectual disability. TRIO uses its two guanine nucleotide exchange factor (GEF) domains to activate GTPases (GEF1: Rac1 and RhoG; GEF2: RhoA) that control neuronal development and connectivity. It remains unclear how discrete TRIO variants differentially impact these neurodevelopmental events. Here, we investigate how heterozygosity for NDD-associated Trio variants - +/K1431M (ASD), +/K1918X (SCZ), and +/M2145T (bipolar disorder, BPD) - impact mouse behavior, brain development, and synapse structure and function. Heterozygosity for different Trio variants impacts motor, social, and cognitive behaviors in distinct ways that model clinical phenotypes in humans. Trio variants differentially impact head and brain size, with corresponding changes in dendritic arbors of motor cortex layer 5 pyramidal neurons (M1 L5 PNs). Although neuronal structure was only modestly altered in the Trio variant heterozygotes, we observe significant changes in synaptic function and plasticity. We also identified distinct changes in glutamate synaptic release in +/K1431M and +/M2145T cortico-cortical synapses. The TRIO K1431M GEF1 domain has impaired ability to promote GTP exchange on Rac1, but +/K1431M mice exhibit increased Rac1 activity, associated with increased levels of the Rac1 GEF Tiam1. Acute Rac1 inhibition with NSC23766 rescued glutamate release deficits in +/K1431M variant cortex. Our work reveals that discrete NDD-associated Trio variants yield overlapping but distinct phenotypes in mice, demonstrates an essential role for Trio in presynaptic glutamate release, and underscores the importance of studying the impact of variant heterozygosity in vivo.

neuroscience↗

bioRxiv2023

B Cells Promote T Cell Immunosenescence and Mammalian Aging Parameters

A dysregulated adaptive immune system is a key feature of aging, and is associated with age-related chronic diseases and mortality. Most notably, aging is linked to a loss in the diversity of the T cell repertoire and expansion of activated inflammatory age-related T cell subsets, though the main drivers of these processes are largely unknown. Here, we find that T cell aging is directly influenced by B cells. Using multiple models of B cell manipulation and single-cell omics, we find B cells to be a major cell type that is largely responsible for the age-related reduction of naive T cells, their associated differentiation towards pathogenic immunosenescent T cell subsets, and for the clonal restriction of their T cell receptor (TCR). Accordingly, we find that these pathogenic shifts can be therapeutically targeted via CD20 monoclonal antibody treatment. Mechanistically, we uncover a new role for insulin receptor signaling in influencing age-related B cell pathogenicity that in turn induces T cell dysfunction and a decline in healthspan parameters. These results establish B cells as a pivotal force contributing to age-associated adaptive immune dysfunction and healthspan outcomes, and suggest new modalities to manage aging and related multi-morbidity. One Sentence SummaryInsulin receptor signaling facilitates the induction of age associated B cell inflammatory changes, which drive phenotypic aging of the T cell compartment and adverse outcomes to mammalian healthspan parameters.

immunology↗

bioRxiv2023

Difference in Kernel Shape and Endocarp Anatomy Promote Dehiscence in Pistachio Endocarp

A fully split shell in pistachio (Pistacia vera) is a trait that is preferred by consumers and is a criterion in evaluating the grade of the pistachio nut. However, while the expanding kernel has been hypothesized to provide the physical force needed for shell split, the mechanisms that control shell split remains unknown. Furthermore, it is intriguing how the shell, or endocarp, splits at the suture ridge when there is no clear dehiscence zone. The objectives of this study were to 1) identify traits associated with dehiscence in fruit in the high split rate cultivar Golden Hills when compared to the lower split rate cultivar Kerman and determine the anatomical features associated with endocarp dehiscence at the suture region, and 2) examine the effect of kernel shape on endocarp dehiscence. We determined that despite of the fact that the pistachio endocarp is primarily composed of a single type of polylobate schlerenchyma cell, specialization of cell shape and size at the suture site results in smaller, more flattened cells. We report that there is a furrowing of the shell at the dorsal and apical suture site, where dehiscence initiates. This furrowing is not observed at the ventral suture site or in the indehiscent fruit of Pistacia atlantica, a species that has been used as rootstock for P. vera. In addition, the size of the kernel in the sagittal axis (the width) is strongly associated with higher split rate. Based on our results, a tentative model emerges where, in the absence of specialized cell types, cell shape modification can create an anatomically distinct region that is mechanically weak in the endocarp for the initiation of dehiscence, while the force from the width of the kernel is necessary for the shell split rate difference as observed in cultivars.

plant biology↗

bioRxiv2023

Labile assembly of a tardigrade protein induces biostasis

Tardigrades are microscopic animals that survive desiccation by inducing biostasis. To survive drying tardigrades rely on intrinsically disordered CAHS proteins that form gels. However, the sequence features and mechanisms underlying gel formation and the necessity of gelation for protection have not been demonstrated. Here we report a mechanism of gelation for CAHS D similar to that of intermediate filaments. We show that gelation restricts molecular motion, immobilizing and protecting labile material from the harmful effects of drying. In vivo, we observe that CAHS D forms fiber-like condensates during osmotic stress. Condensation of CAHS D improves survival of osmotically shocked cells through at least two mechanisms: reduction of cell volume change and reduction of metabolic activity. Importantly, condensation of CAHS D is reversible and metabolic rates return to control levels after CAHS condensates are resolved. This work provides insights into how tardigrades induce biostasis through the self-assembly of CAHS gels.

physiology↗

bioRxiv2023

Recurrent pattern completion drives the neocortical representation of sensory inference

When sensory information is incomplete or ambiguous, the brain relies on prior expectations to infer perceptual objects. Despite the centrality of this process to perception, the neural mechanism of sensory inference is not known. Illusory contours (ICs) are key tools to study sensory inference because they contain edges or objects that are implied only by their spatial context. Using cellular resolution, mesoscale two-photon calcium imaging and multi-Neuropixels recordings in the mouse visual cortex, we identified a sparse subset of neurons in the primary visual cortex (V1) and higher visual areas that respond emergently to ICs. We found that these highly selective IC-encoders mediate the neural representation of IC inference. Strikingly, selective activation of these neurons using two-photon holographic optogenetics was sufficient to recreate IC representation in the rest of the V1 network, in the absence of any visual stimulus. This outlines a model in which primary sensory cortex facilitates sensory inference by selectively strengthening input patterns that match prior expectations through local, recurrent circuitry. Our data thus suggest a clear computational purpose for recurrence in the generation of holistic percepts under sensory ambiguity. More generally, selective reinforcement of top-down predictions by pattern-completing recurrent circuits in lower sensory cortices may constitute a key step in sensory inference.

neuroscience↗

bioRxiv2023

Machine Learning Classification of Alzheimer's Disease Pathology Reveals Diffuse Amyloid as a Major Predictor of Cognitive Impairment in Human Hippocampal Subregions

Analyzing Alzheimers disease (AD) pathology within anatomical subregions is a significant challenge, often carried out by pathologists using a standardized, semi-quantitative approach. To augment traditional methods, a high-throughput, high-resolution pipeline was created to classify the distribution of AD pathology within hippocampal subregions. USC ADRC post-mortem tissue sections from 51 patients were stained with 4G8 for amyloid, Gallyas for neurofibrillary tangles (NFTs) and Iba1 for microglia. Machine learning (ML) techniques were utilized to identify and classify amyloid pathology (dense, diffuse and APP (amyloid precursor protein)), NFTs, neuritic plaques and microglia. These classifications were overlaid within manually segmented regions (aligned with the Allen Human Brain Atlas) to create detailed pathology maps. Cases were separated into low, intermediate, or high AD stages. Further data extraction enabled quantification of plaque size and pathology density alongside ApoE genotype, sex, and cognitive status. Our findings revealed that the increase in pathology burden across AD stages was driven mainly by diffuse amyloid. The pre and para-subiculum had the highest levels of diffuse amyloid while NFTs were highest in the A36 region in high AD cases. Moreover, different pathology types had distinct trajectories across disease stages. In a subset of AD cases, microglia were elevated in intermediate and high compared to low AD. Microglia also correlated with amyloid pathology in the Dentate Gyrus. The size of dense plaques, which may represent microglial function, was lower in ApoE4 carriers. In addition, individuals with memory impairment had higher levels of both dense and diffuse amyloid. Taken together, our findings integrating ML classification approaches with anatomical segmentation maps provide new insights on the complexity of disease pathology in AD progression. Specifically, we identified diffuse amyloid pathology as being a major driver of AD in our cohort, regions of interest and microglial responses that might advance AD diagnosis and treatment.

neuroscience↗

bioRxiv2023

Increased activity of IRE1 improves the clinical presentation of EAE

Activation of the ER stress sensor IRE1 contributes to neuronal development and is known to induce neuronal remodeling in vitro and in vivo. On the other hand, excessive IRE1 activity is often detrimental and may contribute to neurodegeneration. To determine the consequences of increased activation of IRE1, we used a mouse model expressing a C148S variant of IRE1 with increased and sustained activation. Surprisingly, the mutation did not affect the differentiation of highly secretory antibody-producing cells, but exhibited a strong protective effect in a mouse model of experimental autoimmune encephalomyelitis (EAE). Significant improvement in motor function was found in IRE1C148S mice with EAE relative to WT mice. Coincident with this improvement, there was reduced microgliosis in the spinal cord of IRE1C148S mice, with reduced expression of pro-inflammatory cytokine genes. This was accompanied by reduced axonal degeneration and enhanced CNPase levels, suggestiing improved myelin integrity. Interestingly, while the IRE1C148S mutation is expressed in all cells, the reduction in proinflammatory cytokines and in the activation of microglial activation marker IBA1, along with preservation of phagocytic gene expression, all point to microglia as the cell type contributing to the clinical improvement in IRE1C148S animals. Our data suggest that sustained increase in IRE1 activity can be protective in vivo, and that this protection is cell type and context dependent. Considering the overwhelming but conflicting evidence for the role of the ER stress in neurological diseases, a better understanding of the function of ER stress sensors in physiological contexts is clearly needed.

neuroscience↗