Transcription factor protein interactomes reveal genetic determinants in heart disease.

Congenital heart disease (CHD) is present in 1% of live births, yet identification of causal mutations remains challenging. We hypothesized that genetic determinants for CHDs may lie in the protein interactomes of transcription factors whose mutations cause CHDs. Defining the interactomes of two transcription factors haplo-insufficient in CHD, GATA4 and TBX5, within human cardiac progenitors, and integrating the results with nearly 9,000 exomes from proband-parent trios revealed an enrichment of de novo missense variants associated with CHD within the interactomes. Scoring variants of interactome members based on residue, gene, and proband features identified likely CHD-causing genes, including the epigenetic reader GLYR1. GLYR1 and GATA4 widely co-occupied and co-activated cardiac developmental genes, and the identified GLYR1 missense variant disrupted interaction with GATA4, impairing in vitro and in vivo function in mice. This integrative proteomic and genetic approach provides a framework for prioritizing and interrogating genetic variants in heart disease.

Inhibition of CRISPR-Cas9 with Bacteriophage Proteins.

Bacterial CRISPR-Cas systems utilize sequence-specific RNA-guided nucleases to defend against bacteriophage infection. As a countermeasure, numerous phages are known that produce proteins to block the function of class 1 CRISPR-Cas systems. However, currently no proteins are known to inhibit the widely used class 2 CRISPR-Cas9 system. To find these inhibitors, we searched cas9-containing bacterial genomes for the co-existence of a CRISPR spacer and its target, a potential indicator for CRISPR inhibition. This analysis led to the discovery of four unique type II-A CRISPR-Cas9 inhibitor proteins encoded by Listeria monocytogenes prophages. More than half of L. monocytogenes strains with cas9 contain at least one prophage-encoded inhibitor, suggesting widespread CRISPR-Cas9 inactivation. Two of these inhibitors also blocked the widely used Streptococcus pyogenes Cas9 when assayed in Escherichia coli and human cells. These natural Cas9-specific "anti-CRISPRs" present tools that can be used to regulate the genome engineering activities of CRISPR-Cas9.

The RNA Exosome Syncs IAV-RNAPII Transcription to Promote Viral Ribogenesis and Infectivity.

The nuclear RNA exosome is an essential multi-subunit complex that controls RNA homeostasis. Congenital mutations in RNA exosome genes are associated with neurodegenerative diseases. Little is known about the role of the RNA exosome in the cellular response to pathogens. Here, using NGS and human and mouse genetics, we show that influenza A virus (IAV) ribogenesis and growth are suppressed by impaired RNA exosome activity. Mechanistically, the nuclear RNA exosome coordinates the initial steps of viral transcription with RNAPII at host promoters. The viral polymerase complex co-opts the nuclear RNA exosome complex and cellular RNAs en route to 3' end degradation. Exosome deficiency uncouples chromatin targeting of the viral polymerase complex and the formation of cellular:viral RNA hybrids, which are essential RNA intermediates that license transcription of antisense genomic viral RNAs. Our results suggest that evolutionary arms races have shaped the cellular RNA quality control machinery.

A SARS-CoV-2 protein interaction map reveals targets for drug repurposing.

A newly described coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is the causative agent of coronavirus disease 2019 (COVID-19), has infected over 2.3 million people, led to the death of more than 160,000 individuals and caused worldwide social and economic disruption1,2. There are no antiviral drugs with proven clinical efficacy for the treatment of COVID-19, nor are there any vaccines that prevent infection with SARS-CoV-2, and efforts to develop drugs and vaccines are hampered by the limited knowledge of the molecular details of how SARS-CoV-2 infects cells. Here we cloned, tagged and expressed 26 of the 29 SARS-CoV-2 proteins in human cells and identified the human proteins that physically associated with each of the SARS-CoV-2 proteins using affinity-purification mass spectrometry, identifying 332 high-confidence protein-protein interactions between SARS-CoV-2 and human proteins. Among these, we identify 66 druggable human proteins or host factors targeted by 69 compounds (of which, 29 drugs are approved by the US Food and Drug Administration, 12 are in clinical trials and 28 are preclinical compounds). We screened a subset of these in multiple viral assays and found two sets of pharmacological agents that displayed antiviral activity: inhibitors of mRNA translation and predicted regulators of the sigma-1 and sigma-2 receptors. Further studies of these host-factor-targeting agents, including their combination with drugs that directly target viral enzymes, could lead to a therapeutic regimen to treat COVID-19.

Understanding Support for Municipal Political Parties: Evidence from Canada.

The province of Ontario, Canada, has a longstanding history of non-partisanship in municipal elections. In this distinctive context, we report results on citizen attitudes toward municipal partisanship using a survey of eligible voters in Canada's most populous province. Using a mixed-methods approach, we focus on three interrelated research questions. First, how much does citizen support for municipal parties depend on the type of party under consideration? Second, what reasons do citizens provide for their preference for either municipal political parties or independents? Finally, what are the correlates of support for municipal parties? We find little support for municipal political parties, and that many voters have sophisticated reasons for preferring either independents or parties. We also identify several factors associated with support for parties. These results provide an in-depth picture of attitudes on municipal partisanship in Ontario, and suggest that public opinion may provide an overlooked mechanism that maintains Ontario's non-partisanship.

Fab-based inhibitors reveal ubiquitin independent functions for HIV Vif neutralization of APOBEC3 restriction factors.

The lentiviral protein Viral Infectivity Factor (Vif) counteracts the antiviral effects of host APOBEC3 (A3) proteins and contributes to persistent HIV infection. Vif targets A3 restriction factors for ubiquitination and proteasomal degradation by recruiting them to a multi-protein ubiquitin E3 ligase complex. Here, we describe a degradation-independent mechanism of Vif-mediated antagonism that was revealed through detailed structure-function studies of antibody antigen-binding fragments (Fabs) to the Vif complex. Two Fabs were found to inhibit Vif-mediated A3 neutralization through distinct mechanisms: shielding A3 from ubiquitin transfer and blocking Vif E3 assembly. Combined biochemical, cell biological and structural studies reveal that disruption of Vif E3 assembly inhibited A3 ubiquitination but was not sufficient to restore its packaging into viral particles and antiviral activity. These observations establish that Vif can neutralize A3 family members in a degradation-independent manner. Additionally, this work highlights the potential of Fabs as functional probes, and illuminates how Vif uses a multi-pronged approach involving both degradation dependent and independent mechanisms to suppress A3 innate immunity.

Predicting the Transition to Chronic Pain 6 Months After an Emergency Department Visit for Acute Pain: A Prospective Cohort Study.

BACKGROUND: Acute pain can transition to chronic pain, a potentially debilitating illness. OBJECTIVE: We determined how often acute pain transitions to chronic pain among patients in the emergency department (ED) and whether persistent pain 1 week after the ED visit was associated with chronic pain. METHODS: An observational cohort study conducted in two EDs. We included adults with acute pain (≤10 days) if an oral opioid was prescribed. Exclusion criteria were recent opioid use and use of any analgesics regularly prior to onset of the pain. Research associates interviewed patients during the ED visit and 1 week and 6 months later. The primary outcome, chronic pain, was defined as pain on > 50% of days since ED discharge. We constructed logistic regression models to evaluate the association between persistent pain 1 week after an ED visit and chronic pain, while adjusting for demographic and treatment variables. RESULTS: During a 9-month period, we approached 733 patients for participation and enrolled 484; 450 of 484 (93%) provided 1-week outcomes data and 410 of 484 (85%) provided 6-month outcomes data. One week after the ED visit, 348 of 453 (77%; 95% confidence interval [CI] 73-80%) patients reported pain in the affected area. New-onset chronic pain at 6 months was reported by 110 of 408 (27%; 95% CI 23-31%) patients. Presence of pain 1 week after ED visit was associated with chronic pain (odds ratio 3.6; 95% CI 1.6-8.5). CONCLUSIONS: About one-quarter of ED patients with acute pain transition to chronic pain within 6 months. Persistence of pain 1 week after the ED visit can identify patients at risk of transition.

Myocardial AKT: the omnipresent nexus.

One of the greatest examples of integrated signal transduction is revealed by examination of effects mediated by AKT kinase in myocardial biology. Positioned at the intersection of multiple afferent and efferent signals, AKT exemplifies a molecular sensing node that coordinates dynamic responses of the cell in literally every aspect of biological responses. The balanced and nuanced nature of homeostatic signaling is particularly essential within the myocardial context, where regulation of survival, energy production, contractility, and response to pathological stress all flow through the nexus of AKT activation or repression. Equally important, the loss of regulated AKT activity is primarily the cause or consequence of pathological conditions leading to remodeling of the heart and eventual decompensation. This review presents an overview compendium of the complex world of myocardial AKT biology gleaned from more than a decade of research. Summarization of the widespread influence that AKT exerts upon myocardial responses leaves no doubt that the participation of AKT in molecular signaling will need to be reckoned with as a seemingly omnipresent regulator of myocardial molecular biological responses.

Optimal electrostatic interactions between substrate and protein are essential for radical chemistry in ornithine 4,5-aminomutase.

Ornithine 4,5-aminomutase (OAM) from Clostridium sticklandii is an adenosylcobalamin (AdoCbl) and pyridoxal 5'-phosphate (PLP)-dependent enzyme that catalyzes a 1,2-amino shift, interconverting d-ornithine and 2S, 4R-diaminopentanoate. The reaction occurs via a radical-based mechanism whereby a PLP-bound substrate radical undergoes intramolecular isomerization via an azacyclopropylcarbinyl radical intermediate. Herein, we investigated the catalytic role of active site residues that form non-covalent interactions with PLP and/or substrate, d-ornithine. Kinetic analyses revealed that residues that form salt bridges to the α-carboxylate (R297) or the α-amine (E81) of d-ornithine are most critical for OAM activity as conservative substitutions of these residues results in a 300-600-fold reduction in catalytic turnover and a more pronounced 1000- to 14,000-fold decrease in catalytic efficiency. In contrast, mutating residues that solely interact with the PLP cofactor led to more modest decreases (10-60-fold) in kcat and kcat/Km. All but one variant (S162A) elicited an increase in the kinetic isotope effect on kcat and kcat/Km with d,l-ornithine-3,3,4,4,5,5-d6 as the substrate, which indicates that hydrogen atom abstraction is more rate determining. Electron paramagnetic resonance spectra of the variants reveal that while the substitutions decrease the extent of CoC bond homolysis, they do not affect the structural integrity of the active site. Our experimental results, discussed in context with published computational work, suggests that the protonation state of the PLP cofactor has less of a role in radical-mediated chemistry compared to electrostatic interactions between the substrate and protein.

Differential regulation of cellular senescence and differentiation by prolyl isomerase Pin1 in cardiac progenitor cells.

Autologous c-kit(+) cardiac progenitor cells (CPCs) are currently used in the clinic to treat heart disease. CPC-based regeneration may be further augmented by better understanding molecular mechanisms of endogenous cardiac repair and enhancement of pro-survival signaling pathways that antagonize senescence while also increasing differentiation. The prolyl isomerase Pin1 regulates multiple signaling cascades by modulating protein folding and thereby activity and stability of phosphoproteins. In this study, we examine the heretofore unexplored role of Pin1 in CPCs. Pin1 is expressed in CPCs in vitro and in vivo and is associated with increased proliferation. Pin1 is required for cell cycle progression and loss of Pin1 causes cell cycle arrest in the G1 phase in CPCs, concomitantly associated with decreased expression of Cyclins D and B and increased expression of cell cycle inhibitors p53 and retinoblastoma (Rb). Pin1 deletion increases cellular senescence but not differentiation or cell death of CPCs. Pin1 is required for endogenous CPC response as Pin1 knock-out mice have a reduced number of proliferating CPCs after ischemic challenge. Pin1 overexpression also impairs proliferation and causes G2/M phase cell cycle arrest with concurrent down-regulation of Cyclin B, p53, and Rb. Additionally, Pin1 overexpression inhibits replicative senescence, increases differentiation, and inhibits cell death of CPCs, indicating that cell cycle arrest caused by Pin1 overexpression is a consequence of differentiation and not senescence or cell death. In conclusion, Pin1 has pleiotropic roles in CPCs and may be a molecular target to promote survival, enhance repair, improve differentiation, and antagonize senescence.

ß-Adrenergic regulation of cardiac progenitor cell death versus survival and proliferation.

RATIONALE: Short-term ß-adrenergic stimulation promotes contractility in response to stress but is ultimately detrimental in the failing heart because of accrual of cardiomyocyte death. Endogenous cardiac progenitor cell (CPC) activation may partially offset cardiomyocyte losses, but consequences of long-term ß-adrenergic drive on CPC survival and proliferation are unknown. OBJECTIVE: We sought to determine the relationship between ß-adrenergic activity and regulation of CPC function. METHODS AND RESULTS: Mouse and human CPCs express only ß2 adrenergic receptor (ß2-AR) in conjunction with stem cell marker c-kit. Activation of ß2-AR signaling promotes proliferation associated with increased AKT, extracellular signal-regulated kinase 1/2, and endothelial NO synthase phosphorylation, upregulation of cyclin D1, and decreased levels of G protein-coupled receptor kinase 2. Conversely, silencing of ß2-AR expression or treatment with ß2-antagonist ICI 118, 551 impairs CPC proliferation and survival. ß1-AR expression in CPC is induced by differentiation stimuli, sensitizing CPC to isoproterenol-induced cell death that is abrogated by metoprolol. Efficacy of ß1-AR blockade by metoprolol to increase CPC survival and proliferation was confirmed in vivo by adoptive transfer of CPC into failing mouse myocardium. CONCLUSIONS: ß-adrenergic stimulation promotes expansion and survival of CPCs through ß2-AR, but acquisition of ß1-AR on commitment to the myocyte lineage results in loss of CPCs and early myocyte precursors.

Synthesis of a ß-CCT-lanthanide conjugate for binding the dopamine transporter.

The development of a ß-CCT-lanthanide conjugate that binds the dopamine transporter (DAT) with high affinity (K(d) = 303 nM) is described. Contrast agents such as the one described herein could be used as molecular probes to directly study the binding of small molecules to receptors such as DAT via MRI, PET or SPECT.

Nucleolar stress is an early response to myocardial damage involving nucleolar proteins nucleostemin and nucleophosmin.

Nucleolar stress, characterized by loss of nucleolar integrity, has not been described in the cardiac context. In addition to ribosome biogenesis, nucleoli are critical for control of cell proliferation and stress responses. Our group previously demonstrated induction of the nucleolar protein nucleostemin (NS) in response to cardiac pathological insult. NS interacts with nucleophosmin (NPM), a marker of nucleolar stress with cytoprotective properties. The dynamic behavior of NS and NPM reveal that nucleolar disruption is an early event associated with stress response in cardiac cells. Rapid translocation of NS and NPM to the nucleoplasm and suppression of new preribosomal RNA synthesis occurs in both neonatal rat cardiomyocytes (NRCM) and cardiac progenitor cells (CPC) upon exposure to doxorubicin or actinomycin D. Silencing of NS significantly increases cell death resulting from doxorubicin treatment in CPC, whereas NPM knockdown alone induces cell death. Overexpression of either NS or NPM significantly decreases caspase 8 activity in cultured cardiomyocytes challenged with doxorubicin. The presence of altered nucleolar structures resulting from myocardial infarction in mice supports the model of nucleolar stress as a general response to pathological injury. Collectively, these findings serve as the initial description of myocardial nucleolar stress and establish the postulate that nucleoli acts as sensors of stress, regulating the cellular response to pathological insults.

Comprehensive Characterization of Commercial Reverse Osmosis Membranes through High-Temperature Cross-Flow Filtration.

Developing thermally stable reverse osmosis membranes is a potential game-changer in high-temperature water treatment. In this work, the performance of three commercial reverse osmosis membranes was evaluated with a series of high-temperature filtrations. The membranes were tested with different filtration methodologies: long-term operation, cyclic tests, controlled stepwise temperature increment, and permeability tests. The morphological and physiochemical characterizations were performed to study the impact of high-temperature filtration on the membranes' chemical composition and morphological characteristics. An increase in the temperature deteriorated the membrane performance in terms of water flux and salt rejection. Flux decline at high temperatures was recognized as the primary concern for high-temperature filtrations, restricting the applications of commercial membranes for long-term operations. This research provides valuable insights for researchers aiming to thoroughly characterize reverse osmosis membranes at high temperatures.

CRISPR-Cas9 screen of E3 ubiquitin ligases identifies TRAF2 and UHRF1 as regulators of HIV latency in primary human T cells.

During HIV infection of CD4+ T cells, ubiquitin pathways are essential to viral replication and host innate immune response; however, the role of specific E3 ubiquitin ligases is not well understood. Proteomics analyses identified 116 single-subunit E3 ubiquitin ligases expressed in activated primary human CD4+ T cells. Using a CRISPR-based arrayed spreading infectivity assay, we systematically knocked out 116 E3s from activated primary CD4+ T cells and infected them with NL4-3 GFP reporter HIV-1. We found 10 E3s significantly positively or negatively affected HIV infection in activated primary CD4+ T cells, including UHRF1 (pro-viral) and TRAF2 (anti-viral). Furthermore, deletion of either TRAF2 or UHRF1 in three JLat models of latency spontaneously increased HIV transcription. To verify this effect, we developed a CRISPR-compatible resting primary human CD4+ T cell model of latency. Using this system, we found that deletion of TRAF2 or UHRF1 initiated latency reactivation and increased virus production from primary human resting CD4+ T cells, suggesting these two E3s represent promising targets for future HIV latency reversal strategies. IMPORTANCE: HIV, the virus that causes AIDS, heavily relies on the machinery of human cells to infect and replicate. Our study focuses on the host cell's ubiquitination system which is crucial for numerous cellular processes. Many pathogens, including HIV, exploit this system to enhance their own replication and survival. E3 proteins are part of the ubiquitination pathway that are useful drug targets for host-directed therapies. We interrogated the 116 E3s found in human immune cells known as CD4+ T cells, since these are the target cells infected by HIV. Using CRISPR, a gene-editing tool, we individually removed each of these enzymes and observed the impact on HIV infection in human CD4+ T cells isolated from healthy donors. We discovered that 10 of the E3 enzymes had a significant effect on HIV infection. Two of them, TRAF2 and UHRF1, modulated HIV activity within the cells and triggered an increased release of HIV from previously dormant or "latent" cells in a new primary T cell assay. This finding could guide strategies to perturb hidden HIV reservoirs, a major hurdle to curing HIV. Our study offers insights into HIV-host interactions, identifies new factors that influence HIV infection in immune cells, and introduces a novel methodology for studying HIV infection and latency in human immune cells.

The multi-lineage transcription factor ISL1 controls cardiomyocyte cell fate through interaction with NKX2.5.

Congenital heart disease often arises from perturbations of transcription factors (TFs) that guide cardiac development. ISLET1 (ISL1) is a TF that influences early cardiac cell fate, as well as differentiation of other cell types including motor neuron progenitors (MNPs) and pancreatic islet cells. While lineage specificity of ISL1 function is likely achieved through combinatorial interactions, its essential cardiac interacting partners are unknown. By assaying ISL1 genomic occupancy in human induced pluripotent stem cell-derived cardiac progenitors (CPs) or MNPs and leveraging the deep learning approach BPNet, we identified motifs of other TFs that predicted ISL1 occupancy in each lineage, with NKX2.5 and GATA motifs being most closely associated to ISL1 in CPs. Experimentally, nearly two-thirds of ISL1-bound loci were co-occupied by NKX2.5 and/or GATA4. Removal of NKX2.5 from CPs led to widespread ISL1 redistribution, and overexpression of NKX2.5 in MNPs led to ISL1 occupancy of CP-specific loci. These results reveal how ISL1 guides lineage choices through a combinatorial code that dictates genomic occupancy and transcription.

Proteomic and genetic analyses of influenza A viruses identify pan-viral host targets.

Influenza A Virus (IAV) is a recurring respiratory virus with limited availability of antiviral therapies. Understanding host proteins essential for IAV infection can identify targets for alternative host-directed therapies (HDTs). Using affinity purification-mass spectrometry and global phosphoproteomic and protein abundance analyses using three IAV strains (pH1N1, H3N2, H5N1) in three human cell types (A549, NHBE, THP-1), we map 332 IAV-human protein-protein interactions and identify 13 IAV-modulated kinases. Whole exome sequencing of patients who experienced severe influenza reveals several genes, including scaffold protein AHNAK, with predicted loss-of-function variants that are also identified in our proteomic analyses. Of our identified host factors, 54 significantly alter IAV infection upon siRNA knockdown, and two factors, AHNAK and coatomer subunit COPB1, are also essential for productive infection by SARS-CoV-2. Finally, 16 compounds targeting our identified host factors suppress IAV replication, with two targeting CDK2 and FLT3 showing pan-antiviral activity across influenza and coronavirus families. This study provides a comprehensive network model of IAV infection in human cells, identifying functional host targets for pan-viral HDT.

Pim-1 kinase protects mitochondrial integrity in cardiomyocytes.

RATIONALE: Cardioprotective signaling mediates antiapoptotic actions through multiple mechanisms including maintenance of mitochondrial integrity. Pim-1 kinase is an essential downstream effector of AKT-mediated cardioprotection but the mechanistic basis for maintenance of mitochondrial integrity by Pim-1 remains unexplored. This study details antiapoptotic actions responsible for enhanced cell survival in cardiomyocytes with elevated Pim-1 activity. OBJECTIVE: The purpose of this study is to demonstrate that the cardioprotective kinase Pim-1 acts to inhibit cell death by preserving mitochondrial integrity in cardiomyocytes. METHODS AND RESULTS: A combination of biochemical, molecular, and microscopic analyses demonstrate beneficial effects of Pim-1 on mitochondrial integrity. Pim-1 protein level increases in the mitochondrial fraction with a corresponding decrease in the cytosolic fraction of myocardial lysates from hearts subjected to 30 minutes of ischemia followed by 30 minutes of reperfusion. Cardiac-specific overexpression of Pim-1 results in higher levels of antiapoptotic Bcl-X(L) and Bcl-2 compared to samples from normal hearts. In response to oxidative stress challenge, Pim-1 preserves the inner mitochondrial membrane potential. Ultrastructure of the mitochondria is maintained by Pim-1 activity, which prevents swelling induced by calcium overload. Finally, mitochondria isolated from hearts created with cardiac-specific overexpression of Pim-1 show inhibition of cytochrome c release triggered by a truncated form of proapoptotic Bid. CONCLUSION: Cardioprotective action of Pim-1 kinase includes preservation of mitochondrial integrity during cardiomyopathic challenge conditions, thereby raising the potential for Pim-1 kinase activation as a therapeutic interventional approach to inhibit cell death by antagonizing proapoptotic Bcl-2 family members that regulate the intrinsic apoptotic pathway.

A functional map of HIV-host interactions in primary human T cells.

Human Immunodeficiency Virus (HIV) relies on host molecular machinery for replication. Systematic attempts to genetically or biochemically define these host factors have yielded hundreds of candidates, but few have been functionally validated in primary cells. Here, we target 426 genes previously implicated in the HIV lifecycle through protein interaction studies for CRISPR-Cas9-mediated knock-out in primary human CD4+ T cells in order to systematically assess their functional roles in HIV replication. We achieve efficient knockout (>50% of alleles) in 364 of the targeted genes and identify 86 candidate host factors that alter HIV infection. 47 of these factors validate by multiplex gene editing in independent donors, including 23 factors with restrictive activity. Both gene editing efficiencies and HIV-1 phenotypes are highly concordant among independent donors. Importantly, over half of these factors have not been previously described to play a functional role in HIV replication, providing numerous novel avenues for understanding HIV biology. These data further suggest that host-pathogen protein-protein interaction datasets offer an enriched source of candidates for functional host factor discovery and provide an improved understanding of the mechanics of HIV replication in primary T cells.