Biology subjects

Shalit, T.

Publications and source records attributed to Shalit, T..

5 recordsLinked to original sources

bioRxiv2026

Subtype-specific secretion of extracellular vesicles by LRRK2 and Rab GTPases under lysosomal stress

LRRK2, the Parkinsons disease-associated kinase, phosphorylates a subset of Rab GTPases and regulates membrane dynamics. We previously reported that lysosomal stress activates LRRK2 and thereby induces the exocytic secretion of lysosomal contents, but the detailed secretion mechanism remained unclear. Here we found that, under lysosomal stress, endolysosomal luminal and membrane components were secreted with extracellular vesicles (EVs) via LRRK2. Bis(monoacylglycerol)phosphate, an endolysosomal lipid and a urinary marker of LRRK2 activity, was similarly secreted via LRRK2, whereas CD9-positive EVs were not involved. Further dissection of the secreted EVs revealed that Alix-positive EVs were secreted via Rab8a as well as the ESCRT component VPS4, whereas LAMP1/cathepsin B-positive EVs were secreted via Rab10/Rab35, and SNARE proteins syntaxin 2 and VAMP8 regulated the secretion of both EV subtypes. These findings suggest a distinctive stress-induced secretory mechanism whereby LRRK2 facilitates the secretion of multiple EV subtypes by controlling Rab GTPases involved in each pathway.

cell biology↗

bioRxiv2026

Epithelial MHC II antigen presentation dynamically informs intestinal homeostasis and injury

The intestinal epithelium plays a pivotal role in balancing immune tolerance and inflammation, yet how it communicates tissue state to the adaptive immune system remains unclear. Here, we show that intestinal epithelial cells (IECs) encode tissue identity and injury into the major histocompatibility complex class II (MHC II) ligandome. We employed integrated single cell transcriptomics, quantitative proteomics, and high-depth in vivo immunopeptidomics to map the MHC class II self-peptidome of the mouse small intestine across epithelial and immune compartments. Mature enterocytes and intestinal stem cells (ISCs) emerged as the dominant epithelial antigen-presenting cells (APCs), displaying a compartmentalized repertoire of endogenous self-immunopeptides reflecting epithelial differentiation and function. Disruption of epithelial MHC II expression led to loss of antigenic compartmentalization, immune infiltration, extracellular matrix remodeling, and emergence of inflammation-associated immune ligands, demonstrating that epithelial MHC II is required to maintain homeostasis. Functionally, a subset of ISC-derived self-immunopeptides preferentially promotes regulatory CD4{square} T cell responses, linking epithelial antigen presentation and peripheral tolerance. During gut inflammation, the epithelial MHC II landscape shifted toward damage-associated antigens. Together, these findings establish epithelial MHC II presentation as a context-dependent tissue-immune communication system that promotes tolerance in homeostasis and alerts to tissue injury during inflammation.

immunology↗

bioRxiv2023

Circuit to target approach defines an autocrine myofibroblast loop that drives cardiac fibrosis

Fibrosis is a broad pathology of excessive scarring with substantial medical implications. The fibrotic scar is produced by myofibroblasts that interact with macrophages. Fibrosis is a complex process involving thousands of factors, therefore, to better understand fibrosis and develop new therapeutic approaches, it is necessary to simplify and clarify the underlying concepts. Recently, we described a mathematical model for a macrophage-myofibroblast cell circuit, predicting two types of fibrosis - hot fibrosis with abundant macrophages and myofibroblasts, and cold fibrosis dominated by myofibroblasts alone. To test these concepts and intervention strategies in a medically relevant system, we use a widely studied in-vivo injury model for fibrosis, myocardial infarction (MI). We show that cold fibrosis is the final outcome of MI in both mice and pigs and demonstrate that fibrosis can shift toward healing in regenerative settings. MI begind with an increase of myofibroblasts and macrophages, followed by macrophage decline leading to persistent cold fibrosis (only myofibroblasts). During this process, fibroblasts, unlike macrophages, acquire distinct fate changes. Using mathematical modeling we predict that targeting of the autocrine signal for myofibroblast division could block cold fibrosis. We identify TIMP1 as an autocrine cardiac myofibroblast growth factor in-vitro. Treatment of adult mice after MI with anti-TIMP1 antibodies reduces fibrosis in-vivo. This study shows the utility of the concepts of hot and cold fibrosis and the feasibility of our circuit-to-target approach to reduce fibrosis after acute cardiac injury by inhibiting the myofibroblast autocrine loop.

systems biology↗

bioRxiv2022

Sexual deprivation induces a CRF independent stress response and decreases resistance to stressors in Drosophila via a subpopulation of Neuropeptide F receptor-expressing neurons

Living in a changing environment composed of other behaving animals entails both opportunities and challenges to obtain resources and mating partners. Actions that promote survival and reproduction are reinforced by the brain reward systems, whereas coping with the challenges associated with obtaining these rewards are mediated by stress response pathways. The activation of the latter can impair health and shorten lifespan. Although similar responses to social opportunity and challenge exist across the animal kingdom, little is known about the mechanisms that process reward and stress under different social conditions. Here, we studied the interplay between deprivation of sexual reward and stress response in Drosophila melanogaster and discovered that repeated failures to obtain sexual reward induces a frustration-like state that is characterized by increased arousal, persistent sexual motivation, and impaired ability to cope with starvation and oxidative stressors. We show that this increased arousal and sensitivity to starvation is mediated by disinhibition of neurons that express receptors for the fly homologue of neuropeptide Y (neuropeptide F, NPF). We furthermore demonstrate the existence of an anatomical overlap between stress and reward systems in the fly brain in the form of neurons that co-express receptors for NPF (NPFR) and the corticotropin-releasing factor (CRF)-like homologue Diuretic hormone 44 (Dh44), and that deprivation of sexual reward leads to translocation of forkhead box-subgroup O (FoxO) to the cytoplasm in these neurons. Nevertheless, the activity of Dh44 neurons alone does not mediate sensitivity to starvation and aroused behavior following sexual deprivation, instead, these responses are mediated by disinhibition of ~12-16 NPFR-expressing neurons via a dynamin-independent synaptic signaling mechanism, suggesting the existence of a NPFR mediated stress pathway which is Dh44-independent. This paves the path for using simple model organisms to dissect mechanisms behind anticipation of reward, and more specifically, to determine what happens when expectations to obtain natural and drug rewards are not met.

animal behavior and cognition↗

bioRxiv2018

Illuminating spatial A-to-I RNA editing signatures within the Drosophila brain

SummaryAdenosine-to-inosine (A-to-I) RNA editing, catalyzed by ADAR enzymes, is a ubiquitous mechanism that generates transcriptomic diversity. This process is particularly important for proper neuronal function; however, little is known about how RNA editing is dynamically regulated between the many functionally distinct neuronal populations of the brain. In this resource paper, we present a spatial RNA editing map in the Drosophila brain and show that different neuronal populations possess distinct RNA editing signatures. After purifying and sequencing RNA from genetically marked neuronal nuclei, we identified a large number of novel editing sites and compared editing levels in hundreds of transcripts across nine functionally different neuronal populations. We found distinct editing repertoires for each population, including novel sites in repeat regions of the transcriptome and differential editing in highly conserved and likely functional regions of transcripts that encode essential neuronal genes. These changes are site-specific and not driven by changes in Adar expression, suggesting a complex, targeted regulation of editing levels in key transcripts. This fine-tuning of the transcriptome between different neurons by RNA editing may account for functional differences between distinct populations in the brain.\n\nSignificance StatementA fundamental question in contemporary neuroscience is how the remarkable cellular diversity required for the intricate function of the nervous system is achieved. In this manuscript, we bridge the gap between a cellular machinery that is known to diversify the transcriptome and the existence of distinct neuronal populations that compose Drosophila brain. Adenosine-to-inosine (A-to-I) RNA-editing is a ubiquitous mechanism that generates transcriptomic diversity in cells by recoding certain adenosines within the pre-mRNA sequence into inosines. We present a spatial map of RNA editing across different neuronal populations in Drosophila brain. Each neuronal population has a distinct editing signature, with the majority of differential editing occurring in highly conserved regions of transcripts that encode ion channels and other essential neuronal genes.

neuroscience↗