Biology subjects

Zuo, Z.

Publications and source records attributed to Zuo, Z..

At least 37 records · Page 2Linked to original sources

bioRxiv2023

CK2α-dependent regulation of Wnt activity governs white matter development and repair

Wnt signaling plays an essential role in developmental and regenerative myelination in the CNS. The Wnt signaling pathway is comprised of multiple regulatory layers; thus, how these processes are coordinated to orchestrate oligodendrocyte development remains unclear. Here we show CK2, a Wnt/{beta}-catenin signaling Ser/Thr kinase, phosphorylates Daam2, inhibiting its function and Wnt-activity during oligodendrocyte development. Intriguingly, we found Daam2 phosphorylation differentially impacts distinct stages of oligodendrocyte development, accelerating early differentiation followed by decelerating maturation and myelination. Application towards white matter injury revealed CK2-mediated Daam2 phosphorylation plays a protective role for developmental and behavioral recovery after neonatal hypoxia, while promoting myelin repair following adult demyelination. Together, our findings identify a novel regulatory node in the Wnt pathway that regulates oligodendrocyte development via protein phosphorylation-induced signaling complex instability and highlights a new biological mechanism for myelin restoration. SignificanceWnt signaling plays a vital role in OL development and has been implicated as an adverse event for myelin repair after white matter injury. Emerging studies have shed light on multi-modal roles of Wnt effectors in the OL lineage, but the underlying molecular mechanisms and modifiable targets in OL remyelination remain unclear. Using genetic mouse development and injury model systems, we delineate a novel stage-specific function of Daam2 in Wnt signaling and OL development via a S704/T7-5 phosphorylation mechanism, and determine a new role of the kinase CK2 in contributing to OL development. In-depth understanding of CK2-Daam2 pathway regulation will allow us to precisely modulate its activity in conjunction with Wnt signaling and harness its biology for white matter pathology.

neuroscience↗

bioRxiv2022

Understanding Vascular Endothelial Cell Behavior Using a Mechanical Strain Gradient Generated by an Electromagnetic Stretching Device

Cardiovascular diseases cause an estimated 17.9 million deaths globally each year (World Health Organization). Endothelial cells that line the vasculature and the endocardium are subjected to cyclic mechanical stretch. Deviation from physiological stretch can alter the endothelial function, having the risk of atherosclerosis and myocardial infarction. To understand the mechanical stretch effects, cell culture platforms that provide mechanical stretch have been developed. However, most of them have fixed strain and frequency, sometime not in the pathophysiological range. We thus developed a novel, electromagnetically driven, uniaxial stretching device, where cells were grown on a flexible polydimethylsiloxane (PDMS) membrane mounted onto a 3-D printed track. The strain of the membrane was readily controlled by tailoring the track design and the frequency was determined by electromagnetic actuation. Furthermore, the mechanical strain gradient was generated on a PDMS membrane with a tapered thickness. This strain gradient, ranging from 1.5% to 40%, covered both physiological and pathological vascular stretch ranges. When human vascular endothelial cells were subjected to the cyclic stretch, the cells exhibited strain-dependent cell and nuclear orientation and elongation perpendicular to the stretching direction, compared to the random cell and nuclear orientation under the static condition. However, the overstretching led to deviation from the aforementioned orientation and elongation, and impaired the tight junctions, leading to a leaky endothelium. This novel, versatile, cost-effective, pathophysiologically relevant stretching device provides a useful platform for advancement of vascular disease research and treatment.

bioengineering↗

bioRxiv2022

Exploring therapeutic strategies for Infantile Neuronal Axonal Dystrophy (INAD/PARK14)

Infantile Neuroaxonal Dystrophy (INAD) is caused by recessive variants in PLA2G6 and is a lethal pediatric neurodegenerative disorder. Loss of the Drosophila homolog of PLA2G6, leads to ceramide accumulation, lysosome expansion, and mitochondrial defects. Here, we report that ceramide metabolism, the endolysosomal pathway, and mitochondrial morphology are affected in INAD patient-derived neurons. We show that in INAD mouse models the same features are affected and that glucosylceramides are elevated in dopaminergic neurons and Purkinje cells, arguing that the neuropathological mechanisms are evolutionary conserved and that ceramides can be used as biomarkers. We tested 20 drugs that target these pathways and found that Ambroxol, Desipramine, Azoramide, and Genistein alleviate neurodegenerative phenotypes in INAD flies and INAD patient-derived NPCs. We also develop an AAV-based gene therapy approach that delays neurodegeneration and prolongs lifespan in an INAD mouse model. One Sentence SummaryCeramide accumulation, lysosomal expansion and mitochondrial defects are a root cause of INAD/PARK14.

neuroscience↗

bioRxiv2022

mRNA decapping machinery targets LBD3/ASL9 transcripts to allow developmental changes in Arabidopsis

Multicellular organisms perceive and transduce multiple cues to optimize development. Key transcription factors drive developmental changes, but RNA processing also contributes to tissue development. Here, we report that multiple decapping deficient mutants share developmental defects in apical hook, primary and lateral root growth. More specifically, LATERAL ORGAN BOUNDARIES DOMAIN 3 (LBD3)/ASYMMETRIC LEAVES 2-LIKE 9 (ASL9) transcripts accumulate in decapping deficient plants and can be found in complexes with decapping components. Accumulation of ASL9 inhibits apical hook, primary root growth and lateral root formation. Interestingly, exogenous auxin application restores lateral roots formation in both ASL9 over-expressors and mRNA decay-deficient mutants. Likewise, mutations in the cytokinin transcription factors type-B ARABIDOPSIS RESPONSE REGULATORS (B-ARRs) ARR10 and ARR12 restore the developmental defects caused by over-accumulation of capped ASL9 transcript upon ASL9 overexpression. Most importantly, loss-of-function of asl9 partially restores apical hook and lateral root formation in decapping deficient mutants. Thus, the mRNA decay machinery directly targets ASL9 transcripts for decay, possibly to interfere with cytokinin/auxin responses, during development.

developmental biology↗

bioRxiv2022

PAT mRNA decapping factors function specifically and redundantly during development in Arabidopsis

Evolutionarily conserved PAT1 proteins activate mRNA decay through binding mRNA and recruiting decapping enzymes and other factors hence optimize transcriptional reprogramming during development. Here, we generated multiple mutants of pat1 (Protein Associated with Topoisomerase II), path1 and path2 and inspected their growth and leaf morphology phenotype. pat triple mutants exhibit extreme stunted growth and all mutants with pat1 exhibit leaf serration while mutants with pat1 and path1 all display short petioles. All 3 PATs can be found localized to Prossessing Bodies (PBs) upon auxin treatment and RNA-seq analysis indicate that all 3 PATs redundantly regulate auxin responses. Moreover, shade avoidance and NAC genes are misregulated in pat1path1 double and pat triple mutants suggesting PAT1 and PATH1 function in petiole elongation and leaf patterning. In conclusion, PAT proteins exhibit both specific and overlapping functions during different stages of plant growth and our observations underpin the importance of the mRNA decay machinery for proper development.

plant biology↗

bioRxiv2022

Transcriptome-wide profiling of acute stress induced changes in ribosome occupancy level using external standards

Acute cellular stress is known to induce a global reduction in protein translation through suppression of cap dependent translation. However, selective translation in response to acute stress has been shown to play important roles in regulating the stress response. An accurate transcriptome-wide profile of acute cellular stress-induced translational changes has been challenging to obtain. Commonly used data normalization methods, such as quantile normalization, operate based on the assumption that any systematic shifts are artifacts introduced from experimental procedures. Consequently, if applied to profiling acute cellular stress-induced protein translation changes, these methods are expected to produce biased estimates. To address this issue, here we designed, generated, and evaluated a panel of 16 oligomers to serve as external standards for ribosome profiling studies. Using Sodium Arsenite treatment-induced oxidative stress in lymphoblastoid cell lines as a model system, we applied spike-in oligomers as external standards based on quantifications of monosomal RNA extracted from each sample. We found our spike-in oligomers to display a linear correlation between the observed and the expected, with small but significant ratio compression at the lower concentration range, and span the expected quantitative range in the observed data, which covers 97 % of the quantitated endogenous genes. We found popular global scaling normalization approaches to introduce both high levels of false positives and false negatives in differential expression analysis. Using the expected fold changes constructed from spike-in external controls, we found in our dataset that TMM normalization produced 87.5% false positives when a P value cutoff of 0.1 is used (i.e. 10% expected false positive rate)% and on average produced a systematic shift of fold change by 3.25 fold. These results highlight the consequences of applying global scaling approaches to conditions that clearly violate their key assumptions. As an alternative, we found using spike-in quantifications as control genes in RUVg normalization recapitulated the expected stress induced global reduction of translation and resulted in little, if any, systematic shifts in spike-in constructed true positives. Finally, using spike-in constructed true positives and true negatives, we explored alternative normalization approaches for acute cellular stress response ribo-seq studies. We found that a simple approach that quantile normalized data from control and treated samples separately, which we termed respective quantile normalization, produced expected results in spike-in quantification, and resulted in little, if any, systematic bias on fold change in endogenous genes. Additionally, we found that under certain parameters, using endogenous control genes for RUVg normalization best recapitulate the expected. Our results clearly demonstrated the utility of our spike-in oligomers, both for constructing expected results as controls and for data normalization. Our exploration of different normalization approaches highlights the issues in applying global scaling normalization when key assumptions are clearly not met. We show that a respective quantile normalization approach or normalization with endogenous control genes are viable options worth considering as more generalizable approaches for stress response ribo-seq studies. This conclusion is likely applicable to other types of studies that involve global shifts in expression profiles between comparison groups of interests.

genomics↗

bioRxiv2022

Neural Dynamics of Interoceptive Attention and Awareness: A Within-Participant fMRI Study

Interoception, the representation of the bodys internal state, serves as a foundation for emotion, motivation, and wellbeing. Yet despite its centrality in human experience, the neural mechanisms of interoception are poorly understood. The Interoceptive/Exteroceptive Attention Task (IEAT) is a novel neuroimaging paradigm that compares behavioral tracking of the respiratory cycle (Active Interoception) to tracking of a visual stimulus (Active Exteroception). Twenty-two healthy participants completed the IEAT during two separate scanning sessions (N = 44) as part of a randomized control trial of Mindful Awareness in Body-oriented Therapy (MABT). Compared to Exteroception, Interoception deactivated somatomotor and prefrontal regions. Greater interoceptive sensibility (MAIA scale) predicted sparing from deactivation along the anterior cingulate cortex (ACC) and left-lateralized language regions. The right insula--typically described as a primary interoceptive cortex--was only implicated by its further deactivation during an exogenously paced respiration condition (Active Matching). Psychophysiological interaction analysis characterized Active Interoception as promoting greater ACC connectivity with lateral frontal and parietal regions commonly referred to as the Dorsal Attention Network. Interoception of the breath may therefore involve reduced cortical activity but greater connectivity, with greater sensibility sparing cortical inhibition within well-characterized attentional networks. In contrast to a literature that relates detection of liminal signals such as the heartbeat to anterior insula activity, attention towards accessible body sensations such as the breath may lead to a low activity, high connectivity state in which sensory signals from the body may be better discerned. Significance StatementInteroception, the representation of the bodys internal state, is poorly understood compared to the external senses, with existing neuroimaging studies failing to match task difficulty between interoceptive and exteroceptive tasks. The present study used a novel fMRI task to compare interoceptive and exteroceptive attention, and how this distinction was moderated by self-reported interoceptive awareness. The results implicate three novel interoceptive mechanisms: interoception reduces cortical activity while increasing connectivity, wherein awareness is linked to preserved activation of the brains salience network and left-lateralized language regions. These findings characterize interoception as a lower activity state in which awareness depends upon the ability to notice and report on body signals typically obscured by the processing of exteroceptive information and other forms of cognition.

neuroscience↗

bioRxiv2022

A therapeutically targetable NOTCH1-SIRT1-KAT7 axis in T-cell Leukemia

T-cell Acute Lymphoblastic Leukemia (T-ALL) is a NOTCH1-driven disease in need of novel therapies. Here, we identify a NOTCH1-SIRT1-KAT7 link as a therapeutic vulnerability in T-ALL, in which SIRT1 is overexpressed downstream of a novel NOTCH1-bound enhancer. SIRT1 loss impairs leukemia generation, while SIRT1 overexpression accelerates leukemia and confers resistance to NOTCH1 inhibition in a deacetylase-dependent manner. Moreover, secondary SIRT1 loss extends survival and synergizes with NOTCH1 inhibition. Global acetyl-proteomics upon SIRT1 loss uncovered hyperacetylation of KAT7 and BRD1, subunits of a histone acetyltransferase complex targeting H4K12. Metabolic and gene expression profiling revealed a metabolic crisis together with a transcriptional signature resembling KAT7 deletion. Consistently, SIRT1 loss resulted in reduced H4K12ac, and overexpression of a non-acetylatable KAT7 mutant partly rescued SIRT1 loss-induced proliferation defects. The newly unveiled NOTCH1-SIRT1-KAT7 axis uncovers novel therapeutic targets in T-ALL and reveals a circular feedback mechanism balancing deacetylase/acetyltransferase activation with potentially broad relevance in cancer. Statement of significanceWe identified a novel axis in T-ALL whereby NOTCH1 activates SIRT1 through an enhancer region, and SIRT1 deacetylates and activates KAT7. Targeting SIRT1 shows antileukemic effects, partly mediated by KAT7 inactivation. Our results identify novel therapeutic targets and uncover a rheostat mechanism between deacetylase/acetyltransferase activities with potentially broader cancer relevance.

cancer biology↗

bioRxiv2022

From motif to function:Inferring the functions of long zinc finger proteins through combinatorial selection

C2H2 zinc finger proteins (ZFPs) comprise of the largest group of DNA-binding proteins in human genome, and many of them contain long, tandem array of fingers, making the motif discovery, prediction of in vivo cis-regulatory elements (CREs), and understanding their functions particularly challenging. Previous work established that due to the dependent recognition between sub-motifs, the simple, additive recognition model impedes motif discovery and compromises our understanding about how ZFPs work. This work uses ZFP3, a 13-finger long ZFP with no known function, as case example to address the reverse question---given the full-length motif learned through in vitro experiments, like Spec-seq and HT-SELEX, how to reliably identify its in vivo cis-regulatory elements (CREs) and further predict this genes functions. Through sorting of all possible sites within the ChIP-seq peaks with similar predicted binding energy into groups and comparing the aggregate ChIP-seq signals between groups, it is evident that either its full-length or individual sub-motif alone fails to correctly identify all high-affinity specific sites without false-positives, thus it is necessary to revise current algorithm, and use both the core and upstream motifs as separate components to improve the prediction accuracy. Furthermore, significant number of regulatory elements of ZFP3 are found to be proximal to genes associated with microtubules organization and ciliogenesis, which coincides with the fact that ZFP3 is specifically upregulated in multiple ciliated cells. At last, local chromatin accessibility and active chromatin marks like H3K27ac are found to positively associate with the differential binding of ZFP3 between tested cell lines. Overall, this work establishes a novel "From motif to function" strategy for long ZFPs, and the data analysis workflows are implemented through R package TFCookbook for reuse onto other ZFPs.

bioinformatics↗

bioRxiv2022

TIGER: A Web Portal of Tumor Immunotherapy Gene Expression Resource

Immunotherapy is a promising cancer treatment method, but only a few patients benefit from it. Developing new immunotherapy strategies and effective biomarkers of response and resistance is urgent. Recent high-throughput bulk and single-cell gene expression profiling technologies have generated valuable resources in these regards. However, these resources are not well organized and systematic analysis is difficult. Here, we present TIGER, a tumor immunotherapy gene expression resource, which contains bulk transcriptome data of 1508 tumor samples with immunotherapy clinical outcome and 11,057 tumor/normal samples without immunotherapy clinical outcome, as well as single-cell transcriptome data of 2,116,945 immune cells of 655 samples. TIGER provides many useful modules to analyze the collected data and user-provided data. Using the resource in TIGER, we identified a tumor enriched subset of CD4+ T cells. Melanoma patients with higher signature score of this subset have significantly better response and survival under immunotherapy. We believe that TIGER will be helpful for understanding anti-tumor immunity mechanisms and discovering effective biomarkers. TIGER is freely accessible at http://tiger.canceromics.org/.

bioinformatics↗

bioRxiv2021

An expanded toolkit for Drosophila gene tagging using synthesized homology donor constructs for CRISPR mediated homologous recombination

Previously, we described a large collection of Drosophila strains that each carry an artificial exon containing a T2AGAL4 cassette inserted in an intron of a target gene based on CRISPR-mediated homologous recombination (Lee et al., 2018). These alleles permit numerous applications and have proven to be very useful. Initially, the homologous recombination-based donor constructs had long homology arms (>500 bps) to promote precise integration of large constructs (>5kb). Recently, we showed that in vivo linearization of the donor constructs enables insertion of large artificial exons in introns using short homology arms (100-200 bps) (Kanca et al., 2019a). Shorter homology arms make it feasible to commercially synthesize homology donors and minimize the cloning steps for donor construct generation. Unfortunately, about 50% of Drosophila genes lack suitable coding introns for integration of artificial exons. Here, we report the development of new set of constructs that allow the replacement of the coding region of genes that lack suitable introns with a KozakGAL4 cassette, generating a knock-out/knock-in allele that expresses GAL4 similarly as the targeted gene. We also developed custom vector backbones to further facilitate and improve transgenesis. Synthesis of homology donor constructs in custom plasmid backbones that contain the target gene sgRNA obviates the need to inject a separate sgRNA plasmid and significantly increases the transgenesis efficiency. These upgrades will enable the targeting of nearly every fly gene, regardless of exon-intron structure, with a 70-80% success rate.

genetics↗

bioRxiv2021

Nasal BCG Exposure Accelerates Dural Lymphatics Development via Macrophages' Role in Newborn Mice

The dural lymphatics develop mainly during the first postnatal month. Lymphatics may be shaped by immune activation when bacterial infection happens. BCG, a strong immune activator, is widely injected to newborns. Moreover, human beings are nasally exposed in daily life to bacterial stimuli. These background prompted us to investigate whether neonatal BCG injection combined with nasally exposure exerts an influence on dural lymphatics develop. Here, mice received a single dose intracutaneous (i.c.) BCG injection immediately after birth followed by repeated nasal BCG challenge once a day (i.c./nasal group). These mice had an accelerated dural lymphatics growth and increased levels of several cytokines and VEGFR-3. Furthermore, macrophages were identified as a key mediator of these alterations. Mice that received mere one dose i.c. BCG injection showed no significant alterations in these indexes. Additionally, mere repeated nasal BCG challenge induced similar effects to i.c./nasal challenge but with a slighter extent. Taken together, these findings show that repeated nasal BCG vaccination accelerates dural lymphatics development in neonatal mice, especially in the presence of neonatal i.c. BCG injection.

neuroscience↗

bioRxiv2021

Low doses of the organic insecticide spinosad trigger lysosomal defects, ROS driven lipid dysregulation and neurodegeneration in flies

The plight of insect populations around the world and the threats it poses to agriculture and ecosystems has thrown insecticide use into the spotlight. Spinosad is an organic insecticide, considered less harmful to beneficial insects than synthetic insecticides, but its mode of action remains unclear. Using Drosophila, we show that low doses of spinosad reduce cholinergic response in neurons by antagonizing D6 nAChRs. D6 nAChRs are transported to lysosomes that become enlarged and accumulate upon spinosad treatment. Oxidative stress is initiated in the central nervous system, and spreads to midgut and disturbs lipid storage in metabolic tissues in a D6-dependent manner. Spinosad toxicity was ameliorated with the antioxidant N-Acetylcysteine amide (NACA). Chronic exposures lead to mitochondrial defects, severe neurodegeneration and blindness in adult animals. The many deleterious effects of low doses of this insecticide reported here point to an urgent need for rigorous investigation of its impacts on beneficial insects.

neuroscience↗

bioRxiv2021

dSCOPE: a software to detect sequences critical for liquid-liquid phase separation

Membrane based cells are the fundamental structure and function units of organisms, while evidences were increasing that liquid-liquid phase separation (LLPS) is associated with the formation of membraneless organelles, such as P-bodies, nucleoli and stress granules. Many studies have been undertaken to explore the functions of protein phase separation, but these studies lacked an effective tool to identify the sequence segments that critical for LLPS (SCOPEs). In this study, we presented a novel software called dSCOPE (http://dscope.omicsbio.info) to predict the SCOPEs. To develop the predictor, we curated experimentally identified sequence segments that can drive LLPS from published literature. Then sliding sequence window based physiological, biochemical, structural and coding features were integrated by random forest algorithm to perform prediction. Through rigorous evaluation, dSCOPE was demonstrated to achieve satisfactory performance. Furthermore, large-scale analysis of human proteome based on dSCOPE showed that the predicted SCOPEs enriched various protein post-translational modifications and cancer mutations, and the proteins which contain predicted SCOPEs enriched critical cellular signaling pathways. Taken together, dSCOPE precisely predicted the protein sequence segments critical for LLPS, with various helpful information visualized in the webserver to facilitate LLPS related research.

bioinformatics↗

bioRxiv2020

Integrative Analysis of Spatial and Single-Cell Transcriptomics Reveals Principles of Tissue Organization and Intercellular Communication in Mouse Olfactory Bulb

Intercellular communication and spatial organization of cells are two critical aspects of a tissues function. Understanding these aspects requires integrating data from single-cell RNA-Seq (scRNA-seq) and spatial transcriptomics (ST), the two cutting edge technologies that offer complementary insights into tissue composition, architecture, and function. Integrating these data types is non-trivial since they differ widely in the number of profiled genes and often do not share marker genes for given cell-types. We developed STANN, a neural network model that overcomes these methodological challenges. Given ST and scRNA-seq data of a tissue, STANN models cell-types in the scRNA-seq dataset from the genes that are profiled by both ST and scRNA-seq. The trained STANN model then assigns cell-types to the ST dataset. We apply STANN to assign cell-types in a recent ST dataset (SeqFISH+) of mouse olfactory bulb (MOB). Our analysis of STANNs assigned cell-types revealed principles of tissue architecture and intercellular communication at unprecedented detail. We find that cell-type compositions are disproportionate in the tissue, yet their relative proportions are spatially consistent within individual morphological layers. Surprisingly, within a morphological layer, there is a high spatial variation in cell-type colocalization patterns and intercellular communication mechanisms. Our analysis suggests that spatially localized gene regulatory networks may account for such variability in intercellular communication mechanisms.

systems biology↗

bioRxiv2020

Two neuronal peptides encoded from a single transcript regulate mitochondrial function in Drosophila

Naturally produced peptides (<100 amino acids) are important regulators of physiology, development, and metabolism. Recent studies have predicted that thousands of peptides may be translated from transcripts containing small open reading frames (smORFs). Here, we describe two peptides in Drosophila encoded by conserved smORFs, Sloth1 and Sloth2. These peptides are translated from the same bicistronic transcript and share sequence similarities, suggesting that they encode paralogs. Yet, Sloth1 and Sloth2 are not functionally redundant, and loss of either peptide causes animal lethality, reduced neuronal function, impaired mitochondrial function, and neurodegeneration. We provide evidence that Sloth1/2 are highly expressed in neurons, imported to mitochondria, and regulate mitochondrial complex III assembly. These results suggest that phenotypic analysis of smORF genes in Drosophila can provide a wealth of information on the biological functions of this poorly characterized class of genes.

genomics↗

bioRxiv2020

TFEB/Mitf links impaired nuclear import to autophagolysosomal dysfunction in C9-ALS

Disrupted nucleocytoplasmic transport (NCT) has been implicated in neurodegenerative disease pathogenesis; however, the mechanisms by which impaired NCT causes neurodegeneration remain unclear. In a Drosophila screen, we identified Ref(2)p/p62, a key regulator of autophagy, as a potent suppressor of neurodegeneration caused by the GGGGCC hexanucleotide repeat expansion (G4C2 HRE) in C9orf72 that causes amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). We found that p62 is increased and forms ubiquitinated aggregates due to decreased autophagic cargo degradation. Immunofluorescence and electron microscopy of Drosophila tissues demonstrate an accumulation of lysosome-like organelles that precedes neurodegeneration. These phenotypes are partially caused by cytoplasmic mislocalization of Mitf/TFEB, a key transcriptional regulator of autophagolysosomal function. Additionally, TFEB is mislocalized and downregulated in human cells expressing GGGGCC repeats and in C9-ALS patient motor cortex. Our data suggest that the C9orf72-HRE impairs Mitf/TFEB nuclear import, thereby disrupting autophagy and exacerbating proteostasis defects in C9-ALS/FTD.

cell biology↗

bioRxiv2020

Simeprevir suppresses SARS-CoV-2 replication and synergizes with remdesivir

The outbreak of coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a global threat to human health. Using a multidisciplinary approach, we identified and validated the hepatitis C virus (HCV) protease inhibitor simeprevir as an especially promising repurposable drug for treating COVID-19. Simeprevir potently reduces SARS-CoV-2 viral load by multiple orders of magnitude and synergizes with remdesivir in vitro. Mechanistically, we showed that simeprevir inhibits the main protease (Mpro) and unexpectedly the RNA-dependent RNA polymerase (RdRp). Our results thus reveal the viral protein targets of simeprevir, and provide preclinical rationale for the combination of simeprevir and remdesivir for the pharmacological management of COVID-19 patients. One Sentence SummaryDiscovery of simeprevir as a potent suppressor of SARS-CoV-2 viral replication that synergizes with remdesivir.

microbiology↗