Biology subjects

Ott, M.

Publications and source records attributed to Ott, M..

At least 55 records · Page 3Linked to original sources

bioRxiv2022

SIRT5 is a proviral factor that interacts with SARS-CoV-2 Nsp14 protein

SARS-CoV-2 non-structural protein Nsp14 is a highly conserved enzyme necessary for viral replication. Nsp14 forms a stable complex with non-structural protein Nsp10 and exhibits exoribonuclease and N7-methyltransferase activities. Protein-interactome studies identified human sirtuin 5 (SIRT5) as a putative binding partner of Nsp14. SIRT5 is an NAD-dependent protein deacylase critical for cellular metabolism that removes succinyl and malonyl groups from lysine residues. Here we investigated the nature of this interaction and the role of SIRT5 during SARS-CoV-2 infection. We showed that SIRT5 stably interacts with Nsp14, but not with Nsp10, suggesting that SIRT5 and Nsp10 are parts of separate complexes. We found that SIRT5 catalytic domain is necessary for the interaction with Nsp14, but that Nsp14 does not appear to be directly deacylated by SIRT5. Furthermore, knock-out of SIRT5 or treatment with specific SIRT5 inhibitors reduced SARS-CoV-2 viral levels in cell-culture experiments. SIRT5 knock-out cells expressed higher basal levels of innate immunity markers and mounted a stronger antiviral response. Our results indicate that SIRT5 is a proviral factor necessary for efficient viral replication, which opens novel avenues for therapeutic interventions.

microbiology↗

bioRxiv2021

Viral E Protein Neutralizes BET Protein-Mediated Post-Entry Antagonism of SARS-CoV-2

Inhibitors of Bromodomain and Extra-terminal domain (BET) proteins are possible anti-SARS-CoV-2 prophylactics as they downregulate angiotensin-converting enzyme 2 (ACE2). Here, we show that BET proteins should not be inactivated therapeutically as they are critical antiviral factors at the post-entry level. Knockouts of BRD3 or BRD4 in cells overexpressing ACE2 exacerbate SARS-CoV-2 infection; the same is observed when cells with endogenous ACE2 expression are treated with BET inhibitors during infection, and not before. Viral replication and mortality are also enhanced in BET inhibitor-treated mice overexpressing ACE2. BET inactivation suppresses interferon production induced by SARS-CoV-2, a process phenocopied by the envelope (E) protein previously identified as a possible "histone mimetic." E protein, in an acetylated form, directly binds the second bromodomain of BRD4. Our data support a model where SARS-CoV-2 E protein evolved to antagonize interferon responses via BET protein inhibition; this neutralization should not be further enhanced with BET inhibitor treatment.

molecular biology↗

bioRxiv2021

Hepatitis C Virus Infects and Perturbs Liver Stem Cells

Hepatitis C virus (HCV) is the leading cause of death from liver disease. How HCV infection causes lasting liver damage and increases cancer risk beyond viral clearance remains unclear. We identify bipotent liver stem cells as novel targets for HCV infection, and their erroneous differentiation as the potential cause of impaired liver regeneration and cancer development. We show 3D organoids generated from liver stem cells from actively HCV-infected individuals carry replicating virus and maintain low-grade infection over months. Organoids can be infected with a primary HCV isolate. Virus-inclusive single-cell RNA-sequencing uncovered extensive transcriptional reprogramming in HCV+ cells supporting hepatocytic differentiation, cancer stem cell development and viral replication while stem cell proliferation and interferon signaling are disrupted. Our data adds a pathogenesis factor - infection of liver stem cells - to the biology of HCV infection that explains persistent liver damage and enhanced cancer risk through an altered stem cell state.

microbiology↗

bioRxiv2021

The prion and HSP104 modulate cytochrome c oxidase deficiency caused by deletion of COX12

Cytochrome c oxidase is a pivotal enzyme of the mitochondrial respiratory chain, which sustains bioenergetics of eukaryotic cells. Cox12, a peripheral subunit of cytochrome c oxidase, is required for full activity of the enzyme, but its exact function is unknown. Here, experimental evolution of a Saccharomyces cerevisiae {Delta}cox12 strain for ~300 generations allowed to restore the activity of cytochrome c oxidase. In one population, the enhanced bioenergetics was caused by a A375V mutation in the AAA+ disaggregase Hsp104. Deletion or overexpression of Hsp104 also increased respiration of the {Delta}cox12 ancestor strain. This beneficial effect of Hsp104 was related to the loss of the [PSI+] prion, which forms cytosolic amyloid aggregates of the Sup35 protein. Overall, our data demonstrate that cytosolic aggregation of a prion impairs the mitochondrial metabolism of cells defective for Cox12. These findings identify a new functional connection between cytosolic proteostasis and biogenesis of the mitochondrial respiratory chain.

cell biology↗

bioRxiv2021

Liver Organoid and T Cell Coculture Models Cytotoxic T Cell Responses against Hepatitis C Virus

Hepatitis C virus (HCV) remains a global public health challenge with an estimated 71 million people chronically infected, with surges in new cases and no effective vaccine. New methods are needed to study the human immune response to HCV since in vivo animal models are limited and in vitro cancer cell models often show dysregulated immune and proliferative responses. Here we developed a CD8+ T cell and adult stem cell liver organoid system using a microfluidic chip to coculture 3D human liver organoids embedded in extracellular matrix with HLA-matched primary human T cells in suspension. We then employed automated phase contrast and immunofluorescence imaging to monitor T cell invasion and morphological changes in the liver organoids. This microfluidic coculture system supports targeted killing of liver organoids when pulsed with a peptide specific for HCV nonstructural protein 3 (NS3) (KLVALGINAV) in the presence of patient-derived CD8+ T cells specific for KLVALGINAV. This demonstrates the novel potential of the coculture system to molecularly study adaptive immune responses to HCV in an in vitro setting using primary human cells.

immunology↗

bioRxiv2021

Rapid assessment of SARS-CoV-2 evolved variants using virus-like particles

Newly evolved SARS-CoV-2 variants are driving ongoing outbreaks of COVID-19 around the world. Efforts to determine why these viral variants have improved fitness are limited to mutations in the viral spike (S) protein and viral entry steps using non-SARS-CoV-2 viral particles engineered to display S. Here we show that SARS-CoV-2 virus-like particles can package and deliver exogenous transcripts, enabling analysis of mutations within all structural proteins and rapid dissection of multiple steps in the viral life cycle. Identification of an RNA packaging sequence was critical for engineered transcripts to assemble together with SARS-CoV-2 structural proteins S, nucleocapsid (N), membrane (M) and envelope (E) into non-replicative SARS-CoV-2 virus-like particles (SC2-VLPs) that deliver these transcripts to ACE2- and TMPRSS2-expressing cells. Using SC2-VLPs, we tested the effect of 30 individual mutations within the S and N proteins on particle assembly and entry. While S mutations unexpectedly did not affect these steps, SC2-VLPs bearing any one of four N mutations found universally in more-transmissible viral variants (P199L, S202R, R203M and R203K) showed increased particle production and up to 10-fold more reporter transcript expression in receiver cells. Our study provides a platform for rapid testing of viral variants outside a biosafety level 3 setting and identifies viral N mutations and viral particle assembly as mechanisms to explain the increased spread of current viral variants, including Delta (N:R203M). One-Sentence SummaryR203M substitution within SARS-CoV-2 N, found in delta variant, improves RNA packaging into virus-like particles by 10-fold.

microbiology↗

bioRxiv2021

SARS-CoV-2 infection studies in lung organoids identify TSPAN8 as novel mediator

SARS coronavirus-2 (SARS-CoV-2) is causing a global pandemic with large variation in COVID-19 disease spectrum. SARS-CoV-2 infection requires host receptor ACE2 on lung epithelium, but epithelial underpinnings of variation are largely unknown. We capitalized on comprehensive organoid assays to report remarkable variation in SARS-CoV-2 infection rates of lung organoids from different subjects. Tropism is highest for TUBA- and MUC5AC-positive organoid cells, but levels of TUBA-, MUC5A-, or ACE2-positive cells do not predict infection rate. We identify surface molecule Tetraspanin 8 (TSPAN8) as novel mediator of SARS-CoV-2 infection, which is not downregulated by this specific virus. TSPAN8 levels, prior to infection, strongly correlate with infection rate and TSPAN8-blocking antibodies diminish SARS-CoV-2 infection. We propose TSPAN8 as novel functional biomarker and potential therapeutic target for COVID-19.

microbiology↗

bioRxiv2021

Sentinel cells enable genetic detection of SARS-CoV-2 Spike protein

The COVID-19 pandemic has demonstrated the need for exploring different diagnostic and therapeutic modalities to tackle future viral threats. In this vein, we propose the idea of sentinel cells, cellular biosensors capable of detecting viral antigens and responding to them with customizable responses. Using SARS-CoV-2 as a test case, we developed a live cell sensor (SARSNotch) using a de novo-designed protein binder against the SARS-CoV-2 Spike protein. SARSNotch is capable of driving custom genetically-encoded payloads in immortalized cell lines or in primary T lymphocytes in response to purified SARS-CoV-2 Spike or in the presence of Spike-expressing cells. Furthermore, SARSNotch is functional in a cellular system used in directed evolution platforms for development of better binders or therapeutics. In keeping with the rapid dissemination of scientific knowledge that has characterized the incredible scientific response to the ongoing pandemic, we extend an open invitation for others to make use of and improve SARSNotch sentinel cells in the hopes of unlocking the potential of the next generation of smart antiviral therapeutics.

synthetic biology↗

bioRxiv2021

Tropism of SARS-CoV-2 for Developing Human Cortical Astrocytes

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) readily infects a variety of cell types impacting the function of vital organ systems, with particularly severe impact on respiratory function. It proves fatal for one percent of those infected. Neurological symptoms, which range in severity, accompany a significant proportion of COVID-19 cases, indicating a potential vulnerability of neural cell types. To assess whether human cortical cells can be directly infected by SARS-CoV-2, we utilized primary human cortical tissue and stem cell-derived cortical organoids. We find significant and predominant infection in cortical astrocytes in both primary and organoid cultures, with minimal infection of other cortical populations. Infected astrocytes had a corresponding increase in reactivity characteristics, growth factor signaling, and cellular stress. Although human cortical cells, including astrocytes, have minimal ACE2 expression, we find high levels of alternative coronavirus receptors in infected astrocytes, including DPP4 and CD147. Inhibition of DPP4 reduced infection and decreased expression of the cell stress marker, ARCN1. We find tropism of SARS-CoV-2 for human astrocytes mediated by DPP4, resulting in reactive gliosis-type injury.

neuroscience↗

bioRxiv2021

Novel RT-ddPCR assays for determining the transcriptional profile of SARS-CoV-2

The exact mechanism of coronavirus replication and transcription is not fully understood; however, a hallmark of coronavirus transcription is the generation of negative-sense RNA intermediates that serve as the templates for the synthesis of positive-sense genomic RNA (gRNA) and an array of subgenomic mRNAs (sgRNAs) encompassing sequences arising from discontinuous transcription. Existing PCR-based diagnostic assays for SAR-CoV-2 are qualitative or semi-quantitative and do not provide the resolution needed to assess the complex transcription dynamics of SARS-CoV-2 over the course of infection. We developed and validated a novel panel of specially designed SARS-CoV-2 ddPCR-based assays to map the viral transcription profile. Application of these assays to clinically relevant samples will enhance our understanding of SARS-CoV-2 replication and transcription and may also inform the development of improved diagnostic tools and therapeutics. HighlightsO_LIWe developed a novel panel of 7 quantitative RT-ddPCRs assays for SARS-Cov-2 C_LIO_LIOur panel targets nongenic and genic regions in genomic and subgenomic RNAs C_LIO_LIAll assays detect 1-10 copies and are linear over 3-4 orders of magnitude C_LIO_LIAll assays correlated with the clinical Abbott SARS-CoV-2 Viral Load Assay C_LIO_LIClinical samples showed higher copy numbers for targets at the 3 end of the genome C_LI

microbiology↗

bioRxiv2020

Screening a library of FDA-approved and bioactive compounds for antiviral activity against SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), has emerged as a major global health threat. The COVID-19 pandemic has resulted in over 80 million cases and 1.7 million deaths to date while the number of cases continues to rise. With limited therapeutic options, the identification of safe and effective therapeutics is urgently needed. The repurposing of known clinical compounds holds the potential for rapid identification of drugs effective against SARS-CoV-2. Here we utilized a library of FDA-approved and well-studied preclinical and clinical compounds to screen for antivirals against SARS-CoV-2 in human pulmonary epithelial cells. We identified 13 compounds that exhibit potent antiviral activity across multiple orthogonal assays. Hits include known antivirals, compounds with anti-inflammatory activity, and compounds targeting host pathways such as kinases and proteases critical for SARS-CoV-2 replication. We identified seven compounds not previously reported to have activity against SARS-CoV-2, including B02, a human RAD51 inhibitor. We further demonstrated that B02 exhibits synergy with remdesivir, the only antiviral approved by the FDA to treat COVID-19, highlighting the potential for combination therapy. Taken together, our comparative compound screening strategy highlights the potential of drug repurposing screens to identify novel starting points for development of effective antiviral mono- or combination therapies to treat COVID-19.

microbiology↗

bioRxiv2020

Zika Virus Infection Prevents Host mRNA Nuclear Export by Disrupting UPF1 Function

Zika virus (ZIKV) is a mosquito-borne RNA virus that can infect fetuses in utero causing characteristic neurodevelopmental disorders including microcephaly. We previously showed that ZIKV infection downregulates expression of up-frameshift protein 1 (UPF1), a helicase/ATPase and central regulator of the nonsense-mediated mRNA decay pathway. Here, we identify a novel function of nuclear UPF1 in mRNA export. Using crosslinking immunoprecipitation of UPF1 followed by sequencing of associated transcripts as well as fluorescence in situ hybridization experiments, we find widespread mRNA accumulation in the nucleus of human neural progenitor cells (NPCs) upon ZIKV infection or UPF1 knockdown. Knockdown of FREM2, a top UPF1 target transcript encoding an extra-cellular matrix protein critical in fetal development, decreased expression of pluripotency markers and increased expressed neuronal differentiation in NPCs, consistent with the model that trapping FREM2 mRNA in the nucleus perturbs proper NPC function. Collectively, our data uncover a new posttranscriptional mechanism by which ZIKV "shuts off" host mRNA export via UPF1. As we find UPF1 linked to many neurodevelopment pathways, we propose that the lack of host mRNA export contributes to the neurodevelopmental defects associated with ZIKV infection.

microbiology↗

bioRxiv2020

Transcriptomics-based drug repositioning pipeline identifies therapeutic candidates for COVID-19

The novel SARS-CoV-2 virus emerged in December 2019 and has few effective treatments. We applied a computational drug repositioning pipeline to SARS-CoV-2 differential gene expression signatures derived from publicly available data. We utilized three independent published studies to acquire or generate lists of differentially expressed genes between control and SARS-CoV-2-infected samples. Using a rank-based pattern matching strategy based on the Kolmogorov-Smirnov Statistic, the signatures were queried against drug profiles from Connectivity Map (CMap). We validated sixteen of our top predicted hits in live SARS-CoV-2 antiviral assays in either Calu-3 or 293T-ACE2 cells. Validation experiments in human cell lines showed that 11 of the 16 compounds tested to date (including clofazimine, haloperidol and others) had measurable antiviral activity against SARS-CoV-2. These initial results are encouraging as we continue to work towards a further analysis of these predicted drugs as potential therapeutics for the treatment of COVID-19.

bioinformatics↗

bioRxiv2020

Functional genomic screens identify human host factors for SARS-CoV-2 and common cold coronaviruses

The Coronaviridae are a family of viruses that causes disease in humans ranging from mild respiratory infection to potentially lethal acute respiratory distress syndrome. Finding host factors that are common to multiple coronaviruses could facilitate the development of therapies to combat current and future coronavirus pandemics. Here, we conducted parallel genome-wide CRISPR screens in cells infected by SARS-CoV-2 as well as two seasonally circulating common cold coronaviruses, OC43 and 229E. This approach correctly identified the distinct viral entry factors ACE2 (for SARS-CoV-2), aminopeptidase N (for 229E) and glycosaminoglycans (for OC43). Additionally, we discovered phosphatidylinositol phosphate biosynthesis and cholesterol homeostasis as critical host pathways supporting infection by all three coronaviruses. By contrast, the lysosomal protein TMEM106B appeared unique to SARS-CoV-2 infection. Pharmacological inhibition of phosphatidylinositol phosphate biosynthesis and cholesterol homeostasis reduced replication of all three coronaviruses. These findings offer important insights for the understanding of the coronavirus life cycle as well as the potential development of host-directed therapies.

microbiology↗

bioRxiv2020

Polygenic mutations model the pleiotropic disease of Fanconi Anemia

Fanconi Anemia (FA) is a prototypic genetic disease signified by heterogeneous phenotypes including cancer, bone marrow failure, short stature, congenital abnormalities, infertility, sub-mendelian birth rate, genome instability and high cellular sensitivity to cancer therapeutics1-4. Clinical diagnosis is confirmed by identifying biallelic, homo- or hemizygous mutations in any one of twenty-three FANC genes1,5. Puzzlingly, inactivation of one single Fanc gene in mice fails to faithfully model the human disease manifestations6-8. We here delineate a preclinical Fanc mouse model with mutations in two genes, Fancd1/Brca2 and Fanco/Rad51c, that recapitulates the severity and heterogeneity of the human disease manifestations including death by cancer at young age. Surprisingly, these grave phenotypes cannot be explained by the sum of phenotypes seen in mice with single gene inactivation, which are unremarkable. In contrast to expectations from classic epistasis analysis of genetic pathways, the data instead reveal an unexpected functional synergism of polygenic Fanc mutations. Importantly in humans, whole exome sequencing uncovers that FANC co-mutation in addition to the identified inactivating FANC gene mutation is a frequent event in FA patients. Collectively, the data establish a concept of polygenic stress as an important contributor to disease manifestations, with implications for molecular diagnostics.

cancer biology↗

bioRxiv2020

SARS-CoV-2 infection of human iPSC-derived cardiac cells predicts novel cytopathic features in hearts of COVID-19 patients

Although COVID-19 causes cardiac dysfunction in up to 25% of patients, its pathogenesis remains unclear. Exposure of human iPSC-derived heart cells to SARS-CoV-2 revealed productive infection and robust transcriptomic and morphological signatures of damage, particularly in cardiomyocytes. Transcriptomic disruption of structural proteins corroborated adverse morphologic features, which included a distinct pattern of myofibrillar fragmentation and numerous iPSC-cardiomyocytes lacking nuclear DNA. Human autopsy specimens from COVID-19 patients displayed similar sarcomeric disruption, as well as cardiomyocytes without DNA staining. These striking cytopathic features provide new insights into SARS-CoV-2 induced cardiac damage, offer a platform for discovery of potential therapeutics, and raise serious concerns about the long-term consequences of COVID-19.

cell biology↗

bioRxiv2020

An ultra-high affinity synthetic nanobody blocks SARS-CoV-2 infection by locking Spike into an inactive conformation

Without an effective prophylactic solution, infections from SARS-CoV-2 continue to rise worldwide with devastating health and economic costs. SARS-CoV-2 gains entry into host cells via an interaction between its Spike protein and the host cell receptor angiotensin converting enzyme 2 (ACE2). Disruption of this interaction confers potent neutralization of viral entry, providing an avenue for vaccine design and for therapeutic antibodies. Here, we develop single-domain antibodies (nanobodies) that potently disrupt the interaction between the SARS-CoV-2 Spike and ACE2. By screening a yeast surface-displayed library of synthetic nanobody sequences, we identified a panel of nanobodies that bind to multiple epitopes on Spike and block ACE2 interaction via two distinct mechanisms. Cryogenic electron microscopy (cryo-EM) revealed that one exceptionally stable nanobody, Nb6, binds Spike in a fully inactive conformation with its receptor binding domains (RBDs) locked into their inaccessible down-state, incapable of binding ACE2. Affinity maturation and structure-guided design of multivalency yielded a trivalent nanobody, mNb6-tri, with femtomolar affinity for SARS-CoV-2 Spike and picomolar neutralization of SARS-CoV-2 infection. mNb6-tri retains stability and function after aerosolization, lyophilization, and heat treatment. These properties may enable aerosol-mediated delivery of this potent neutralizer directly to the airway epithelia, promising to yield a widely deployable, patient-friendly prophylactic and/or early infection therapeutic agent to stem the worst pandemic in a century.

biochemistry↗

bioRxiv2020

Immune landscape of a genetically-engineered murine model of glioma relative to human glioma by single-cell sequencing

BackgroundThis study focuses on the evaluation of intratumoral immune infiltrates of the Qk/trp53/Pten (QPP) triple-knockout mouse model of glioblastoma with the purpose of establishing its relevance compared to the human disease. This included an analysis at the single cell level, of immune cells composition in both spontaneous and implanted mouse tumors and of samples obtained from human tumor resections. MethodsWe analyzed a cohort of fifteen spontaneous QPP mice, nine implanted QPP mice and 10 glioma patients by standard immune profiling methods such as IHC. Of those, we analyzed three spontaneous QPP mice, three implanted QPP mice, and 10 glioma patients by single cell RNA sequencing. ResultsIn the QPP samples we identified a predominantly myeloid cell population of monocytes, macrophages, and microglia, with minor populations of T, B, and NK cells. When comparing spontaneous and implanted mouse samples, we found that there were more neutrophil, T and NKT cells in the implanted model. In human samples, most of the lymphoid and myeloid compartments were immunosuppressive. While the complexity of the myeloid cell populations is preserved between the QPP model and the human disease, we observed significantly more immune-stimulatory populations in the implanted mouse model. ConclusionsWe found that, despite differences at the subpopulation level, the immunosuppressive nature of the immune system in glioma, is recapitulated in our mouse model. Although we observed differences in the proportions of immune infiltrates derived from the spontaneous and implanted mouse models and in LGG compared to GBM, the major constituents are present in all cases and these differences may be caused by various etiological or pathogenic influences on tumor-immune interactions. Key PointsO_LINew GBM mouse model for immunotherapy C_LIO_LISingle cell profiling of the immune systems in human and mouse GBM C_LI

cancer biology↗