Pharmacological inhibition of the integrated stress response accelerates disease progression in an amyotrophic lateral sclerosis mouse model.

BACKGROUND AND PURPOSE: The integrated stress response (ISR) regulates translation in response to diverse stresses. ISR activation has been documented in amyotrophic lateral sclerosis (ALS) patients and ALS experimental models. In experimental models, both ISR stimulation and inhibition prevented ALS neurodegeneration; however, which mode of ISR regulation would work in patients is still debated. We previously demonstrated that the ISR modulator ISRIB (Integrated Stress Response InhiBitor, an eIF2B activator) enhances survival of neurons expressing the ALS neurotoxic allele SOD1 G93A. Here, we tested the effect of two ISRIB-like eIF2B activators (2BAct and PRXS571) in the disease progression of transgenic SOD1G93A mice. EXPERIMENTAL APPROACH: After biochemical characterization in primary neurons, SOD1G93A mice were treated with 2BAct and PRXS571. Muscle denervation of vulnerable motor units was monitored with a longitudinal electromyographic test. We used a clinical score to document disease onset and progression; force loss was determined with the hanging wire motor test. Motor neuronal survival was assessed by immunohistochemistry. KEY RESULTS: In primary neurons, 2BAct and PRXS571 relieve the ISR-imposed translational inhibition while maintaining high ATF4 levels. Electromyographic recordings evidenced an earlier and more dramatic muscle denervation in treated SOD1G93A mice that correlated with a decrease in motor neuron survival. Both compounds anticipated disease onset and shortened survival time. CONCLUSION AND IMPLICATIONS: 2BAct and PRXS571 anticipate disease onset, aggravating muscle denervation and motor neuronal death of SOD1G93A mice. This study reveals that the ISR works as a neuroprotective pathway in ALS motor neurons and reveals the toxicity that eIF2B activators may display in ALS patients.

Stabilization of 14-3-3 protein-protein interactions with Fusicoccin-A decreases alpha-synuclein dependent cell-autonomous death in neuronal and mouse models.

Synucleinopathies are a group of neurodegenerative diseases without effective treatment characterized by the abnormal aggregation of alpha-synuclein (aSyn) protein. Changes in levels or in the amino acid sequence of aSyn (by duplication/triplication of the aSyn gene or point mutations in the encoding region) cause familial cases of synucleinopathies. However, the specific molecular mechanisms of aSyn-dependent toxicity remain unclear. Increased aSyn protein levels or pathological mutations may favor abnormal protein-protein interactions (PPIs) that could either promote neuronal death or belong to a coping response program against neurotoxicity. Therefore, the identification and modulation of aSyn-dependent PPIs can provide new therapeutic targets for these diseases. To identify aSyn-dependent PPIs we performed a proximity biotinylation assay based on the promiscuous biotinylase BioID2. When expressed as a fusion protein, BioID2 biotinylates by proximity stable and transient interacting partners, allowing their identification by streptavidin affinity purification and mass spectrometry. The aSyn interactome was analyzed using BioID2-tagged wild-type (WT) and pathological mutant E46K aSyn versions in HEK293 cells. We found the 14-3-3 epsilon isoform as a common protein interactor for WT and E46K aSyn. 14-3-3 epsilon correlates with aSyn protein levels in brain regions of a transgenic mouse model overexpressing WT human aSyn. Using a neuronal model in which aSyn cell-autonomous toxicity is quantitatively scored by longitudinal survival analysis, we found that stabilization of 14-3-3 protein-proteins interactions with Fusicoccin-A (FC-A) decreases aSyn-dependent toxicity. Furthermore, FC-A treatment protects dopaminergic neuronal somas in the substantia nigra of a Parkinson's disease mouse model. Based on these results, we propose that the stabilization of 14-3-3 epsilon interaction with aSyn might reduce aSyn toxicity, and highlight FC-A as a potential therapeutic compound for synucleinopathies.

The Role and Therapeutic Potential of the Integrated Stress Response in Amyotrophic Lateral Sclerosis.

In amyotrophic lateral sclerosis (ALS) patients, loss of cellular homeostasis within cortical and spinal cord motor neurons triggers the activation of the integrated stress response (ISR), an intracellular signaling pathway that remodels translation and promotes a gene expression program aimed at coping with stress. Beyond its neuroprotective role, under regimes of chronic or excessive stress, ISR can also promote cell/neuronal death. Given the two-edged sword nature of ISR, many experimental attempts have tried to establish the therapeutic potential of ISR enhancement or inhibition in ALS. This review discusses the complex interplay between ISR and disease progression in different models of ALS, as well as the opportunities and limitations of ISR modulation in the hard quest to find an effective therapy for ALS.

Live imaging of the co-translational recruitment of XBP1 mRNA to the ER and its processing by diffuse, non-polarized IRE1α.

Endoplasmic reticulum (ER) to nucleus homeostatic signaling, known as the unfolded protein response (UPR), relies on the non-canonical splicing of XBP1 mRNA. The molecular switch that initiates splicing is the oligomerization of the ER stress sensor and UPR endonuclease IRE1α (inositol-requiring enzyme 1 alpha). While IRE1α can form large clusters that have been proposed to function as XBP1 processing centers on the ER, the actual oligomeric state of active IRE1α complexes as well as the targeting mechanism that recruits XBP1 to IRE1α oligomers remains unknown. Here, we have developed a single-molecule imaging approach to monitor the recruitment of individual XBP1 transcripts to the ER surface. Using this methodology, we confirmed that stable ER association of unspliced XBP1 mRNA is established through HR2 (hydrophobic region 2)-dependent targeting and relies on active translation. In addition, we show that IRE1α-catalyzed splicing mobilizes XBP1 mRNA from the ER membrane in response to ER stress. Surprisingly, we find that XBP1 transcripts are not recruited into large IRE1α clusters, which are only observed upon overexpression of fluorescently tagged IRE1α during ER stress. Our findings support a model where ribosome-engaged, immobilized XBP1 mRNA is processed by small IRE1α assemblies that could be dynamically recruited for processing of mRNA transcripts on the ER.

Lessons From Mass-Testing for Coronavirus Disease 2019 in Long-Term Care Facilities for the Elderly in San Francisco.

Coronavirus disease 2019 can cause significant mortality in the elderly in long-term care facilities (LTCF). We describe 4 LTCF outbreaks where mass testing identified a high proportion of asymptomatic infections (4%-41% in healthcare workers and 20%-75% in residents), indicating that symptom-based screening alone is insufficient for monitoring for COVID-19 transmission.

Crisis Decision-Making at the Speed of COVID-19: Field Report on Issuing the First Regional Shelter-in-Place Orders in the United States.

CONTEXT: In March, 2020, the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causal agent of coronavirus disease 2019 (COVID-19), was spreading in the Bay Area, especially in Santa Clara County, causing increases in cases, hospitalizations, and deaths. PROGRAM: The Association of Bay Area Health Officials (ABAHO) represents 13 Bay Area health jurisdictions. IMPLEMENTATION: On March 15, 2020, the local health officers of 7 ABAHO members (counties of Alameda, Contra Costa, Marin, San Francisco, San Mateo, and Santa Clara and the city of Berkeley) decided to issue legal orders on March 16 for 6.7 million residents to shelter in place to prevent the spread of SARS-CoV-2, the causal agent of COVID-19. The Bay Area was the first region in the United States to shelter in place, and within days, other regions in the United States followed. EVALUATION: Subsequent comparative analyses have confirmed that acting early in issuing shelter-in-place orders prevented a large number of cases, hospitalizations, and deaths in the Bay Area throughout the United States. The quality of a decision-in this case, for crisis decision making-cannot be judged by the outcome. A good decision can have a bad outcome, and a bad decision can have a good outcome. The quality of a decision depends only on the quality of the decision-making process at the time the decision was made. DISCUSSION: In this Field Report, we review how we made this collective decision. With the benefit of hindsight and reflection, we recount our story through the lens of public health legal authority, meta-leadership, and decision intelligence. Our purpose is to improve the crisis decision-making skills of public health officials by improving how we make high-stakes decisions each day in our continuing fight to contain the SARS-CoV-2 pandemic, to save lives, and to eliminate COVID-19 racial/ethnic inequities.

Linking the Expression of Therapeutic Genes to Unfolded Protein Response: A New Option for Anti-Hepatitis B Virus Gene Therapy.

Tight control of transgene expression is key to ensure the efficacy of a wide range of gene therapy interventions, in which the magnitude and duration of gene expression have to be adjusted to therapeutic needs, thereby limiting secondary effects. The development of upgraded strategies to link transgene expression to pathological stress episodes is an unmet need in gene therapy. Here, we propose an expression strategy that associates transgene expression to an intracellular stress coping mechanism, the unfolded protein response. Specifically, we harnessed the cis elements required to sustain the noncanonical splicing of X-box binding protein 1 (XBP1) messenger RNA (mRNA) in response to the dysfunction of the endoplasmic reticulum (ER), a situation commonly known as ER stress, to drive the expression of heterologous genes. Since ER stress features a wide variety of pathological conditions, including viral infections, cancer, or metabolic disorders, this new expression module stimulates the synthesis of therapeutic genes as a response to cellular damage, and ensures their expression only when necessary. Validation of this inducible expression system was performed in vitro and in vivo, and its potential to limit/inhibit viral infections has been shown in proof-of principle experiments.

Erratum: Bridging the gap between research, policy, and practice: Lessons learned from academic-public partnerships in the CTSA network - CORRIGENDUM.

[This corrects the article DOI: 10.1017/cts.2020.23.].

Maturation of NAA20 Aminoterminal End Is Essential to Assemble NatB N-Terminal Acetyltransferase Complex.

Protein lifespan is regulated by co-translational modification by several enzymes, including methionine aminopeptidases and N-alpha-aminoterminal acetyltransferases. The NatB enzymatic complex is an N-terminal acetyltransferase constituted by two subunits, NAA20 and NAA25, whose interaction is necessary to avoid NAA20 catalytic subunit degradation. We found that deletion of the first five amino acids of hNAA20 or fusion of a peptide to its amino terminal end abolishes its interaction with hNAA25. Substitution of the second residue of hNAA20 with amino acids with small, uncharged side-chains allows NatB enzymatic complex formation. However, replacement by residues with large or charged side-chains interferes with its hNAA25 interaction, limiting functional NatB complex formation. Comparison of NAA20 eukaryotic sequences showed that the residue following the initial methionine, an amino acid with a small uncharged side-chain, has been evolutionarily conserved. We have confirmed the relevance of second amino acid characteristics of NAA20 in NatB enzymatic complex formation in Drosophila melanogaster. Moreover, we have evidenced the significance of NAA20 second residue in Saccharomyces cerevisiae using different NAA20 versions to reconstitute NatB formation in a yNAA20-KO yeast strain. The requirement in humans and in fruit flies of an amino acid with a small uncharged side-chain following the initial methionine of NAA20 suggests that methionine aminopeptidase action may be necessary for the NAA20 and NAA25 interaction. We showed that inhibition of MetAP2 expression blocked hNatB enzymatic complex formation by retaining the initial methionine of NAA20. Therefore, NatB-mediated protein N-terminal acetylation is dependent on methionine aminopeptidase, providing a regulatory mechanism for protein N-terminal maturation.

Bridging the gap between research, policy, and practice: Lessons learned from academic-public partnerships in the CTSA network.

A primary barrier to translation of clinical research discoveries into care delivery and population health is the lack of sustainable infrastructure bringing researchers, policymakers, practitioners, and communities together to reduce silos in knowledge and action. As National Institutes of Health's (NIH) mechanism to advance translational research, Clinical and Translational Science Award (CTSA) awardees are uniquely positioned to bridge this gap. Delivering on this promise requires sustained collaboration and alignment between research institutions and public health and healthcare programs and services. We describe the collaboration of seven CTSA hubs with city, county, and state healthcare and public health organizations striving to realize this vision together. Partnership representatives convened monthly to identify key components, common and unique themes, and barriers in academic-public collaborations. All partnerships aligned the activities of the CTSA programs with the needs of the city/county/state partners, by sharing resources, responding to real-time policy questions and training needs, promoting best practices, and advancing community-engaged research, and dissemination and implementation science to narrow the knowledge-to-practice gap. Barriers included competing priorities, differing timelines, bureaucratic hurdles, and unstable funding. Academic-public health/health system partnerships represent a unique and underutilized model with potential to enhance community and population health.

TNF-alpha inhibition ameliorates HDV-induced liver damage in a mouse model of acute severe infection.

BACKGROUND & AIMS: HDV infection induces the most severe form of human viral hepatitis. However, the specific reasons for the severity of the disease remain unknown. Recently, we developed an HDV replication mouse model in which, for the first time, liver damage was detected. METHODS: HDV and HBV replication-competent genomes and HDV antigens were delivered to mouse hepatocytes using adeno-associated vectors (AAVs). Aminotransferase elevation, liver histopathology, and hepatocyte death were evaluated and the immune infiltrate was characterized. Liver transcriptomic analysis was performed. Mice deficient for different cellular and molecular components of the immune system, as well as depletion and inhibition studies, were employed to elucidate the causes of HDV-mediated liver damage. RESULTS: AAV-mediated HBV/HDV coinfection caused hepatocyte necrosis and apoptosis. Activated T lymphocytes, natural killer cells, and proinflammatory macrophages accounted for the majority of the inflammatory infiltrate. However, depletion studies and the use of different knockout mice indicated that neither T cells, natural killer cells nor macrophages were necessary for HDV-induced liver damage. Transcriptomic analysis revealed a strong activation of type I and II interferon (IFN) and tumor necrosis factor (TNF)-α pathways in HBV/HDV-coinfected mice. While the absence of IFN signaling had no effect, the use of a TNF-α antagonist resulted in a significant reduction of HDV-associated liver injury. Furthermore, hepatic expression of HDAg resulted in the induction of severe liver damage, which was T cell- and TNF-α-independent. CONCLUSIONS: Both host (TNF-α) and viral (HDV antigens) factors play a relevant role in HDV-induced liver damage. Importantly, pharmacological inhibition of TNF-α may offer an attractive strategy to aid control of HDV-induced acute liver damage. LAY SUMMARY: Chronic hepatitis delta constitutes the most severe form of viral hepatitis. There is limited data on the mechanism involved in hepatitis delta virus (HDV)-induced liver pathology. Our data indicate that a cytokine (TNF-α) and HDV antigens play a relevant role in HDV-induced liver damage.

Proteostasis disturbances and endoplasmic reticulum stress contribute to polycystic liver disease: New therapeutic targets.

BACKGROUND & AIMS: Polycystic liver diseases (PLDs) are genetic disorders characterized by progressive development of multiple biliary cysts. Recently, novel PLD-causative genes, encoding for endoplasmic reticulum (ER)-resident proteins involved in protein biogenesis and transport, were identified. We hypothesized that aberrant proteostasis contributes to PLD pathogenesis, representing a potential therapeutic target. METHODS: ER stress was analysed at transcriptional (qPCR), proteomic (mass spectrometry), morphological (transmission electron microscopy, TEM) and functional (proteasome activity) levels in different PLD models. The effect of ER stress inhibitors [4-phenylbutyric acid (4-PBA)] and/or activators [tunicamycin (TM)] was tested in polycystic (PCK) rats and cystic cholangiocytes in vitro. RESULTS: The expression levels of unfolded protein response (UPR) components were upregulated in liver tissue from PLD patients and PCK rats, as well as in primary cultures of human and rat cystic cholangiocytes, compared to normal controls. Cystic cholangiocytes showed altered proteomic profiles, mainly related to proteostasis (ie synthesis, folding, trafficking and degradation of proteins), marked enlargement of the ER lumen (by TEM) and hyperactivation of the proteasome. Notably, chronic treatment of PCK rats with 4-PBA decreased liver weight, as well as both liver and cystic volumes, of animals under baseline conditions or after TM administration compared to controls. In vitro, 4-PBA downregulated the expression (mRNA) of UPR effectors, normalized proteomic profiles related to protein synthesis, folding, trafficking and degradation and reduced the proteasome hyperactivity in cystic cholangiocytes, reducing their hyperproliferation and apoptosis. CONCLUSIONS: Restoration of proteostasis in cystic cholangiocytes with 4-PBA halts hepatic cystogenesis, emerging as a novel therapeutic strategy.

Fine tuning of the unfolded protein response by ISRIB improves neuronal survival in a model of amyotrophic lateral sclerosis.

Loss of protein folding homeostasis features many of the most prevalent neurodegenerative disorders. As coping mechanism to folding stress within the endoplasmic reticulum (ER), the unfolded protein response (UPR) comprises a set of signaling mechanisms that initiate a gene expression program to restore proteostasis, or when stress is chronic or overwhelming promote neuronal death. This fate-defining capacity of the UPR has been proposed to play a key role in amyotrophic lateral sclerosis (ALS). However, the several genetic or pharmacological attempts to explore the therapeutic potential of UPR modulation have produced conflicting observations. In order to establish the precise relationship between UPR signaling and neuronal death in ALS, we have developed a neuronal model where the toxicity of a familial ALS-causing allele (mutant G93A SOD1) and UPR activation can be longitudinally monitored in single neurons over the process of neurodegeneration by automated microscopy. Using fluorescent UPR reporters we established the temporal and causal relationship between UPR and neuronal death by Cox regression models. Pharmacological inhibition of discrete UPR processes allowed us to establish the contribution of PERK (PKR-like ER kinase) and IRE1 (inositol-requiring enzyme-1) mechanisms to neuronal fate. Importantly, inhibition of PERK signaling with its downstream inhibitor ISRIB, but not with the direct PERK kinase inhibitor GSK2606414, significantly enhanced the survival of G93A SOD1-expressing neurons. Characterization of the inhibitory properties of both drugs under ER stress revealed that in neurons (but not in glial cells) ISRIB overruled only part of the translational program imposed by PERK, relieving the general inhibition of translation, but maintaining the privileged translation of ATF4 (activating transcription factor 4) messenger RNA. Surprisingly, the fine-tuning of the PERK output in G93A SOD1-expressing neurons led to a reduction of IRE1-dependent signaling. Together, our findings identify ISRIB-mediated translational reprogramming as a new potential ALS therapy.

The importance of naturally attenuated SARS-CoV-2in the fight against COVID-19.

The current SARS-CoV-2 pandemic is wreaking havoc throughout the world and has rapidly become a global health emergency. A central question concerning COVID-19 is why some individuals become sick and others not. Many have pointed already at variation in risk factors between individuals. However, the variable outcome of SARS-CoV-2 infections may, at least in part, be due also to differences between the viral subspecies with which individuals are infected. A more pertinent question is how we are to overcome the current pandemic. A vaccine against SARS-CoV-2 would offer significant relief, although vaccine developers have warned that design, testing and production of vaccines may take a year if not longer. Vaccines are based on a handful of different designs (i), but the earliest vaccines were based on the live, attenuated virus. As has been the case for other viruses during earlier pandemics, SARS-CoV-2 will mutate and may naturally attenuate over time (ii). What makes the current pandemic unique is that, thanks to state-of-the-art nucleic acid sequencing technologies, we can follow in detail how SARS-CoV-2 evolves while it spreads. We argue that knowledge of naturally emerging attenuated SARS-CoV-2 variants across the globe should be of key interest in our fight against the pandemic.

N-terminal acetylation mutants affect alpha-synuclein stability, protein levels and neuronal toxicity.

Alpha-synuclein (aSyn) protein levels are sufficient to drive Parkinson's disease (PD) and other synucleinopathies. Despite the biomedical/therapeutic potential of aSyn protein regulation, little is known about mechanisms that limit/control aSyn levels. Here, we investigate the role of a post-translational modification, N-terminal acetylation, in aSyn neurotoxicity. N-terminal acetylation occurs in all aSyn molecules and has been proposed to determine its lipid binding and aggregation capacities; however, its effect in aSyn stability/neurotoxicity has not been evaluated. We generated N-terminal mutants that alter or block physiological aSyn N-terminal acetylation in wild-type or pathological mutant E46K aSyn versions and confirmed N-terminal acetylation status by mass spectrometry. By optical pulse-labeling in living primary neurons we documented a reduced half-life and accumulation of aSyn N-terminal mutants. To analyze the effect of N-terminal acetylation mutants in neuronal toxicity we took advantage of a neuronal model where aSyn toxicity was scored by longitudinal survival analysis. Salient features of aSyn neurotoxicity were previously investigated with this approach. aSyn-dependent neuronal death was recapitulated either by higher aSyn protein levels in the case of WT aSyn, or by the combined effect of protein levels and enhanced neurotoxicity conveyed by the E46K mutation. aSyn N-terminal mutations decreased E46K aSyn-dependent neuronal death both by reducing protein levels and, importantly, by reducing the intrinsic E46K aSyn toxicity, being the D2P mutant the least toxic. Together, our results illustrate that the N-terminus determines, most likely through its acetylation, aSyn protein levels and toxicity, identifying this modification as a potential therapeutic target.

Recent advances in signal integration mechanisms in the unfolded protein response.

Since its discovery more than 25 years ago, great progress has been made in our understanding of the unfolded protein response (UPR), a homeostatic mechanism that adjusts endoplasmic reticulum (ER) function to satisfy the physiological demands of the cell. However, if ER homeostasis is unattainable, the UPR switches to drive cell death to remove defective cells in an effort to protect the health of the organism. This functional dichotomy places the UPR at the crossroads of the adaptation versus apoptosis decision. Here, we focus on new developments in UPR signaling mechanisms, in the interconnectivity among the signaling pathways that make up the UPR in higher eukaryotes, and in the coordination between the UPR and other fundamental cellular processes.