Large-scale Pan-cancer Cell Line Screening Identifies Actionable and Effective Drug Combinations.

Oncology drug combinations can improve therapeutic responses and increase treatment options for patients. The number of possible combinations is vast and responses can be context-specific. Systematic screens can identify clinically relevant, actionable combinations in defined patient subtypes. We present data for 109 anticancer drug combinations from AstraZeneca's oncology small molecule portfolio screened in 755 pan-cancer cell lines. Combinations were screened in a 7 × 7 concentration matrix, with more than 4 million measurements of sensitivity, producing an exceptionally data-rich resource. We implement a new approach using combination Emax (viability effect) and highest single agent (HSA) to assess combination benefit. We designed a clinical translatability workflow to identify combinations with clearly defined patient populations, rationale for tolerability based on tumor type and combination-specific "emergent" biomarkers, and exposures relevant to clinical doses. We describe three actionable combinations in defined cancer types, confirmed in vitro and in vivo, with a focus on hematologic cancers and apoptotic targets. SIGNIFICANCE: We present the largest cancer drug combination screen published to date with 7 × 7 concentration response matrices for 109 combinations in more than 750 cell lines, complemented by multi-omics predictors of response and identification of "emergent" combination biomarkers. We prioritize hits to optimize clinical translatability, and experimentally validate novel combination hypotheses. This article is featured in Selected Articles from This Issue, p. 695.

Experiences of Successful PrEP Uptake Among Adolescent Sexual Minority Men in the United States: A Qualitative Exploration.

Male adolescent sexual minorities are at elevated risk of HIV acquisition yet demonstrate low rates of PrEP uptake. Understanding the experiences of adolescents who have successfully accessed PrEP may inform ways to best support adolescents seeking PrEP. Adolescent sexual minorities (N = 100) who reported utilizing PrEP responded to open-ended items asking about their initial PrEP experiences and advice for others. Qualitative analysis suggested that adolescents' ability to access PrEP is influenced by managing parental involvement and seeking culturally competent health care providers. Additionally, they reported how the benefits and drawbacks of taking PrEP played a role in their PrEP use. Findings suggest that educational PrEP interventions targeted at this population could improve uptake by incorporating discussions on side effects and mental health benefits associated with PrEP use. Structural interventions are warranted that improve adolescents' ability to seek sexual health care independently and make room for parental involvement when adolescents could benefit from their support.

Preclinical Characterization of AZD9574, a Blood-Brain Barrier Penetrant Inhibitor of PARP1.

PURPOSE: We evaluated the properties and activity of AZD9574, a blood-brain barrier (BBB) penetrant selective inhibitor of PARP1, and assessed its efficacy and safety alone and in combination with temozolomide (TMZ) in preclinical models. EXPERIMENTAL DESIGN: AZD9574 was interrogated in vitro for selectivity, PARylation inhibition, PARP-DNA trapping, the ability to cross the BBB, and the potential to inhibit cancer cell proliferation. In vivo efficacy was determined using subcutaneous as well as intracranial mouse xenograft models. Mouse, rat, and monkey were used to assess AZD9574 BBB penetration and rat models were used to evaluate potential hematotoxicity for AZD9574 monotherapy and the TMZ combination. RESULTS: AZD9574 demonstrated PARP1-selectivity in fluorescence anisotropy, PARylation, and PARP-DNA trapping assays and in vivo experiments demonstrated BBB penetration. AZD9574 showed potent single agent efficacy in preclinical models with homologous recombination repair deficiency in vitro and in vivo. In an O6-methylguanine-DNA methyltransferase (MGMT)-methylated orthotopic glioma model, AZD9574 in combination with TMZ was superior in extending the survival of tumor-bearing mice compared with TMZ alone. CONCLUSIONS: The combination of three key features-PARP1 selectivity, PARP1 trapping profile, and high central nervous system penetration in a single molecule-supports the development of AZD9574 as the best-in-class PARP inhibitor for the treatment of primary and secondary brain tumors. As documented by in vitro and in vivo studies, AZD9574 shows robust anticancer efficacy as a single agent as well as in combination with TMZ. AZD9574 is currently in a phase I trial (NCT05417594). See related commentary by Lynce and Lin, p. 1217.

Social Support-Seeking Strategies on Social Media at the Intersection of Lesbian, Gay, Bisexual, Transgender, and Queer Identity, Race, and Ethnicity: Insights for Intervention From a Qualitative Study.

BACKGROUND: Lesbian, gay, bisexual, transgender, and queer (LGBTQ+) individuals experience a disproportionately higher prevalence of mental health challenges when compared to their heterosexual and cisgender counterparts. Moreover, they exhibit increased engagement with social media platforms relative to their peers. Understanding the intersectional dynamics of their identities is crucial in elucidating effective and safe approaches to garnering social support through social media channels. This exploration holds significance for informing future research endeavors and shaping targeted interventions to address the unique mental health needs of LGBTQ+ individuals. OBJECTIVE: The purpose of this study was to explore the strategies used by Black, Hispanic, and non-Hispanic White LGBTQ+ young adults to acquire social support from social media. The study aimed to examine how these strategies may differ by race and ethnicity. METHODS: We conducted semistructured interviews with LGBTQ+ young adults aged between 18 and 30 years recruited in the United States from social media. Of 52 participants, 12 (23%) were Black, 12 (23%) were Hispanic, and 28 (54%) were non-Hispanic White. Thematic analysis was used to analyze the collected data. RESULTS: The analysis uncovered both divergent and convergent strategies among participants of different races and ethnicities. Black and Hispanic young adults exhibited a preference for connecting with individuals who shared similar identities, seeking safety and tailored advice. Conversely, non-Hispanic White participants demonstrated minimal preference for identity-based advice. Seeking support from anonymous sources emerged as a strategy to avoid unwanted disclosure among Hispanic participants. Furthermore, all participants emphasized the importance of content filtering with family members to cultivate positive and supportive social media experiences. CONCLUSIONS: This study sheds light on the strategies used by LGBTQ+ individuals of different racial and ethnic backgrounds to seek social support from social media platforms. The findings underscore the importance of considering race and ethnicity when examining social support-seeking behaviors on social media in LGBTQ+ populations. The identified strategies provide valuable insights for the development of interventions that aim to leverage social support from social media to benefit the mental health of Black, Hispanic, and non-Hispanic White LGBTQ+ young adults.

New Zealanders with low back pain seeking health care: a retrospective descriptive analysis of Accident Compensation Corporation-funded low back pain healthcare service usage.

Introduction Most New Zealanders experience low back pain (LBP) at least once throughout their lifetime and many seek help from the large range of health providers in primary care. Accident Compensation Corporation (ACC) funds a significant proportion of those claims, but which services are they funding and what are the costs? Method This was a retrospective audit and descriptive analysis of ACC-funded, non-public hospital healthcare service use by people with LBP in New Zealand (NZ). Outcome measures were the healthcare services accessed by people with ACC-funded LBP,the claims (all occurrences for a service that has generated a payment/year), single contact (with a service), and costs (NZ$) for services between 2009 and 2020. Results The number of claims for services were 129 000 for physiotherapy, 105 000 for general practitioner and 59 000 for radiology services. Per single contact, elective surgery and radiology services were the most expensive. During 2009-2020, there were 3.3 million ACC claims for LBP with a total cost of NZ$4 billion. Over this time, there was an increase in claims, costs and single contacts. Costs decreased slightly during 2010 due to changes in healthcare funding and in 2020 due to the COVID-19 pandemic. Discussion Consumers have considerable choice in where they access health care for ACC-funded LBP services. This study shows the services they use most frequently and the cost to NZ for those services. These data can inform service planning for ACC-funded LBP health care in NZ.

Effects of internalised racism and internalised homophobia on sexual behaviours among black gay and bisexual men in the USA: a systematic review protocol.

INTRODUCTION: Black gay and bisexual men are overburdened by HIV in the USA. While the socioecological model has been applied to understand potential mechanisms of HIV acquisition among black gay and bisexual men, there is mixed evidence on the impact of internalised stigma on HIV risk among this population. This systematic review protocol paper outlines the systematic review being conducted to determine the relationship between internalised racism, internalised homophobia and engagement in sexual behaviour, which puts individuals at risk for HIV infection. METHODS AND ANALYSIS: For the review, we will conduct a systematic review of the literature, summarise and critique published scholarly literature on the associations between forms of internalised stigma and sexual behaviours among black gay and bisexual men. We will conduct a systematic search of published qualitative and quantitative research studies published during and after 1993. The searches will be conducted in Ovid Medline, Ovid APA PsycInfo and EBSCO SocINDEX databases. Studies will be included if they were conducted in the USA, with samples that comprised African American/black cisgender gay, bisexual, queer and other men who have sex with men, measured internalised racism and/or internalised homophobia, and assessed sexual behaviour risk for HIV acquisition. ETHICS AND DISSEMINATION: No ethical approval will be required for this review. We will report our findings using the guidelines outlined by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Findings of this review may offer new opportunities to study internalised mechanisms impacting outcomes and to identify research gaps and spur additional queries in the group most disproportionately impacted by HIV.

Capillary Assembly of Anisotropic Particles at Cylindrical Fluid-Fluid Interfaces.

The unique behavior of colloids at liquid interfaces provides exciting opportunities for engineering the assembly of colloidal particles into functional materials. The deformable nature of fluid-fluid interfaces means that we can use the interfacial curvature, in addition to particle properties, to direct self-assembly. To this end, we use a finite element method (Surface Evolver) to study the self-assembly of rod-shaped particles adsorbed at a simple curved fluid-fluid interface formed by a sessile liquid drop with cylindrical geometry. Specifically, we study the self-assembly of single and multiple rods as a function of drop curvature and particle properties such as shape (ellipsoid, cylinder, and spherocylinder), contact angle, aspect ratio, and chemical heterogeneity (homogeneous and triblock patchy). We find that the curved interface allows us to effectively control the orientation of the rods, allowing us to achieve parallel, perpendicular, or novel obliquely orientations with respect to the cylindrical drop. In addition, by tuning particle properties to achieve parallel alignment of the rods, we show that the cylindrical drop geometry favors tip-to-tip assembly of the rods, not just for cylinders, but also for ellipsoids and triblock patchy rods. Finally, for triblock patchy rods with larger contact line undulations, we can achieve strong spatial confinement of the rods transverse to the cylindrical drop due to the capillary repulsion between the contact line undulations of the particle and the pinned contact lines of the sessile drop. Our capillary assembly method allows us to manipulate the configuration of single and multiple rod-like particles and therefore offers a facile strategy for organizing such particles into useful functional materials.

Nucleolar Architecture Is Modulated by a Small Molecule, the Inositol Pyrophosphate 5-InsP7.

Inositol pyrophosphates (PP-InsPs); are a functionally diverse family of eukaryotic molecules that deploy a highly-specialized array of phosphate groups as a combinatorial cell-signaling code. One reductive strategy to derive a molecular-level understanding of the many actions of PP-InsPs is to individually characterize the proteins that bind them. Here, we describe an alternate approach that seeks a single, collective rationalization for PP-InsP binding to an entire group of proteins, i.e., the multiple nucleolar proteins previously reported to bind 5-InsP7 (5-diphospho-inositol-1,2,3,4,6-pentakisphosphate). Quantitative confocal imaging of the outer nucleolar granular region revealed its expansion when cellular 5-InsP7 levels were elevated by either (a) reducing the 5-InsP7 metabolism by a CRISPR-based knockout (KO) of either NUDT3 or PPIP5Ks; or (b), the heterologous expression of wild-type inositol hexakisphosphate kinase, i.e., IP6K2; separate expression of a kinase-dead IP6K2 mutant did not affect granular volume. Conversely, the nucleolar granular region in PPIP5K KO cells shrank back to the wild-type volume upon attenuating 5-InsP7 synthesis using either a pan-IP6K inhibitor or the siRNA-induced knockdown of IP6K1+IP6K2. Significantly, the inner fibrillar volume of the nucleolus was unaffected by 5-InsP7. We posit that 5-InsP7 acts as an 'electrostatic glue' that binds together positively charged surfaces on separate proteins, overcoming mutual protein-protein electrostatic repulsion the latter phenomenon is a known requirement for the assembly of a non-membranous biomolecular condensate.

Cryo-EM reveals the architecture of the PELP1-WDR18 molecular scaffold.

PELP1 (Proline-, Glutamic acid-, Leucine-rich protein 1) is a large scaffolding protein that functions in many cellular pathways including steroid receptor (SR) coactivation, heterochromatin maintenance, and ribosome biogenesis. PELP1 is a proto-oncogene whose expression is upregulated in many human cancers, but how the PELP1 scaffold coordinates its diverse cellular functions is poorly understood. Here we show that PELP1 serves as the central scaffold for the human Rix1 complex whose members include WDR18, TEX10, and SENP3. We reconstitute the mammalian Rix1 complex and identified a stable sub-complex comprised of the conserved PELP1 Rix1 domain and WDR18. We determine a 2.7 Å cryo-EM structure of the subcomplex revealing an interconnected tetrameric assembly and the architecture of PELP1's signaling motifs, including eleven LxxLL motifs previously implicated in SR signaling and coactivation of Estrogen Receptor alpha (ERα) mediated transcription. However, the structure shows that none of these motifs is in a conformation that would support SR binding. Together this work establishes that PELP1 scaffolds the Rix1 complex, and association with WDR18 may direct PELP1's activity away from SR coactivation.

Efficient Copper-Catalyzed Highly Stereoselective Synthesis of Unprotected C-Acyl Manno-, Rhamno- and Lyxopyranosides.

Due to their high stability towards enzymatic hydrolysis C-acyl glycosidic compounds are useful synthetic intermediates for potential candidates in drug discovery. Syntheses for C-acyl mannosides have remained scarce and usually employ donors obtained from lengthy syntheses. Furthermore, syntheses of unprotected C-acyl mannosides have not been reported so far, due to the incapability of the C-acyl mannoside motif with deprotection conditions for protective groups commonly used in carbohydrate chemistry. Herein, we report an efficient and highly α-selective four-step one-pot method for the synthesis of C-acyl α-d-manno-, l-rhamno- and d-lyxopyranosides from easily accessible persilylated monosaccharides and dithianes requiring only trace amounts of a copper source as catalyst and explain the crucial role of the catalyst by mechanistic studies. Furthermore, the C-acyl α-glycosides were easily isomerized to give rapid access to their ß-anomers.

Synchrony and idiosyncrasy in the gut microbiome of wild baboons.

Human gut microbial dynamics are highly individualized, making it challenging to link microbiota to health and to design universal microbiome therapies. This individuality is typically attributed to variation in host genetics, diets, environments and medications but it could also emerge from fundamental ecological forces that shape microbiota more generally. Here, we leverage extensive gut microbial time series from wild baboons-hosts who experience little interindividual dietary and environmental heterogeneity-to test whether gut microbial dynamics are synchronized across hosts or largely idiosyncratic. Despite their shared lifestyles, baboon microbiota were only weakly synchronized. The strongest synchrony occurred among baboons living in the same social group, probably because group members range over the same habitat and simultaneously encounter the same sources of food and water. However, this synchrony was modest compared to each host's personalized dynamics. In support, host-specific factors, especially host identity, explained, on average, more than three times the deviance in longitudinal dynamics compared to factors shared with social group members and ten times the deviance of factors shared across the host population. These results contribute to mounting evidence that highly idiosyncratic gut microbiomes are not an artefact of modern human environments and that synchronizing forces in the gut microbiome (for example, shared environments, diets and microbial dispersal) are not strong enough to overwhelm key drivers of microbiome personalization, such as host genetics, priority effects, horizontal gene transfer and functional redundancy.

Excessive energy expenditure due to acute physical restraint disrupts Drosophila motivational feeding response.

To study the behavior of Drosophila, it is often necessary to restrain and mount individual flies. This requires removal from food, additional handling, anesthesia, and physical restraint. We find a strong positive correlation between the length of time flies are mounted and their subsequent reflexive feeding response, where one hour of mounting is the approximate motivational equivalent to ten hours of fasting. In an attempt to explain this correlation, we rule out anesthesia side-effects, handling, additional fasting, and desiccation. We use respirometric and metabolic techniques coupled with behavioral video scoring to assess energy expenditure in mounted and free flies. We isolate a specific behavior capable of exerting large amounts of energy in mounted flies and identify it as an attempt to escape from restraint. We present a model where physical restraint leads to elevated activity and subsequent faster nutrient storage depletion among mounted flies. This ultimately further accelerates starvation and thus increases reflexive feeding response. In addition, we show that the consequences of the physical restraint profoundly alter aerobic activity, energy depletion, taste, and feeding behavior, and suggest that careful consideration is given to the time-sensitive nature of these highly significant effects when conducting behavioral, physiological or imaging experiments that require immobilization.

Genetic ancestry predicts male-female affiliation in a natural baboon hybrid zone.

Opposite-sex social relationships are important predictors of fitness in many animals, including several group-living mammals. Consequently, understanding sources of variance in the tendency to form opposite-sex relationships is important for understanding social evolution. Genetic contributions are of particular interest due to their importance in long-term evolutionary change, but little is known about genetic effects on male-female relationships in social mammals, especially outside of the mating context. Here, we investigate the effects of genetic ancestry on male-female affiliative behaviour in a hybrid zone between the yellow baboon, Papio cynocephalus, and the anubis baboon, Papio anubis, in a population in which male-female social bonds are known predictors of life span. We place our analysis within the context of other social and demographic predictors of affiliative behaviour in baboons. Genetic ancestry was the most consistent predictor of opposite-sex affiliative behaviour we observed, with the exception of strong effects of dominance rank. Our results show that increased anubis genetic ancestry is associated with a subtle, but significantly higher, probability of opposite-sex affiliative behaviour, in both males and females. Additionally, pairs of anubis-like males and anubis-like females were the most likely to socially affiliate, resulting in moderate assortativity in grooming and proximity behaviour as a function of genetic ancestry. Our findings indicate that opposite-sex affiliative behaviour partially diverged during baboon evolution to differentiate yellow and anubis baboons, despite overall similarities in their social structures and mating systems. Furthermore, they suggest that affiliative behaviour may simultaneously promote and constrain baboon admixture, through additive and assortative effects of ancestry, respectively.

Inhibition of Scavenger Receptor Class B Type 1 (SR-B1) Expression and Activity as a Potential Novel Target to Disrupt Cholesterol Availability in Castration-Resistant Prostate Cancer.

There have been several studies that have linked elevated scavenger receptor class b type 1 (SR-B1) expression and activity to the development and progression of castration-resistant prostate cancer (CRPC). SR-B1 facilitates the influx of cholesterol to the cell from lipoproteins in systemic circulation. This influx of cholesterol may be important for many cellular functions, including the synthesis of androgens. Castration-resistant prostate cancer tumors can synthesize androgens de novo to supplement the loss of exogenous sources often induced by androgen deprivation therapy. Silencing of SR-B1 may impact the ability of prostate cancer cells, particularly those of the castration-resistant state, to maintain the intracellular supply of androgens by removing a supply of cholesterol. SR-B1 expression is elevated in CRPC models and has been linked to poor survival of patients. The overarching belief has been that cholesterol modulation, through either synthesis or uptake inhibition, will impact essential signaling processes, impeding the proliferation of prostate cancer. The reduction in cellular cholesterol availability can impede prostate cancer proliferation through both decreased steroid synthesis and steroid-independent mechanisms, providing a potential therapeutic target for the treatment of prostate cancer. In this article, we discuss and highlight the work on SR-B1 as a potential novel drug target for CRPC management.

A systematic review of the engagement with social media-delivered interventions for improving health outcomes among sexual and gender minorities.

BACKGROUND: Sexual and gender minority (SGM) persons face a number of physical and mental health disparities closely linked to discrimination, social stigma, and victimization. Despite the acceptability and increasing number of digital health interventions focused on improving health outcomes among SGM people, there is a lack of reviews summarizing whether and how researchers assess engagement with social media-delivered health interventions for this group. OBJECTIVE: The objective of this systematic review was to synthesize and critique the evidence on evaluation of engagement with social media-delivered interventions for improving health outcomes among SGM persons. METHODS: We conducted a literature search for studies published between January 2003 and June 2020 using 4 electronic databases. Articles were included if they were peer-reviewed, in English language, assessed engagement with a social media-delivered health intervention for improving health outcomes among sexual and gender minorities. A minimum of two authors independently extracted data from each study using an a priori developed abstraction form. We assessed quality of data reporting using the CONSORT extension for pilot and feasibility studies and CONSORT statement parallel group randomized trials. RESULTS: We included 18 articles in the review; 15 were feasibility studies and 3 were efficacy or effectiveness randomized trials. The quality of data reporting varied considerably. The vast majority of articles focused on improving HIV-related outcomes among men who have sex with men. Only three studies recruited cisgender women and/or transgender persons. We found heterogeneity in how engagement was defined and assessed. Intervention usage from social media data was the most frequently used engagement measure. CONCLUSION: In addition to the heterogeneity in defining and assessing engagement, we found that the focus of assessment was often on measures of intervention usage only. More purposeful recruitment is needed to learn about whether, how, and why different SGM groups engage with social media-interventions. This leaves significant room for future research to expand evaluation criteria for cognitive and emotional aspects of intervention engagement in order to develop effective and tailored social media-delivered interventions for SGM people. Our findings also support the need for developing and testing social media-delivered interventions that focus on improving mental health and outcomes related to chronic health conditions among SGM persons.

The effects of dietary nitrate supplementation on endurance exercise performance and cardiorespiratory measures in healthy adults: a systematic review and meta-analysis.

BACKGROUND: Nitrate supplementation is thought to improve performance in endurance sports. OBJECTIVE: To meta-analyze studies evaluating the effect of nitrate supplementation on endurance sports performance among adults. DATA SOURCES: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, Web of Science and CINAHL without language restrictions. METHODS: We included studies that: 1) compared nitrate supplementation with placebo; 2) enrolled adults engaging in an endurance-based activity; and 3) reported a performance measure or surrogate physiologic outcome. We evaluated risk of bias using the Cochrane Collaboration tool and pooled data with a random-effects model. We used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to evaluate confidence in estimates. RESULTS: We included 73 studies (n = 1061). Nitrate supplementation improved power output (MD 4.6 watts, P < 0.0001), time to exhaustion (MD 25.3 s, P < 0.00001), and distance travelled (MD 163.7 m, P = 0.03). We found no significant difference on perceived exertion, time trial performance and work done. Nitrate supplementation decreased VO2 (MD - 0.04 L/min, P < 0.00001) but had no significant effect on VO2max or blood lactate levels. CONCLUSION: The available evidence suggests that dietary nitrate supplementation benefits performance-related outcomes for endurance sports.

Gut microbiome heritability is nearly universal but environmentally contingent.

Relatives have more similar gut microbiomes than nonrelatives, but the degree to which this similarity results from shared genotypes versus shared environments has been controversial. Here, we leveraged 16,234 gut microbiome profiles, collected over 14 years from 585 wild baboons, to reveal that host genetic effects on the gut microbiome are nearly universal. Controlling for diet, age, and socioecological variation, 97% of microbiome phenotypes were significantly heritable, including several reported as heritable in humans. Heritability was typically low (mean = 0.068) but was systematically greater in the dry season, with low diet diversity, and in older hosts. We show that longitudinal profiles and large sample sizes are crucial to quantifying microbiome heritability, and indicate scope for selection on microbiome characteristics as a host phenotype.

Corrigendum: A Nanomule Peptide Carrier Delivers siRNA Across the Intact Blood-Brain Barrier to Attenuate Ischemic Stroke.

[This corrects the article DOI: 10.3389/fmolb.2021.611367.].

A Nanomule Peptide Carrier Delivers siRNA Across the Intact Blood-Brain Barrier to Attenuate Ischemic Stroke.

The blood-brain barrier (BBB) hinders the distribution of therapeutics intended for treatment of neuroinflammation (NI) of the central nervous system. A twelve-amino acid peptide that transcytoses the BBB, termed MTfp, was chemically conjugated to siRNA to create a novel peptide-oligonucleotide conjugate (POC), directed to downregulate NOX4, a gene thought responsible for oxidative stress in ischemic stroke. The MTfp-NOX4 POC has the ability to cross the intact BBB and knockdown NOX4 expression in the brain. Following induction of ischemic stroke, animals pretreated with the POC exhibited significantly smaller infarcts; accompanied by increased protection against neurological deterioration and improved recovery. The data demonstrates that the MTfp can act as a nanomule to facilitate BBB transcytosis of siRNAs; where the NOX-4 specific siRNA moiety can elicit effective therapeutic knockdown of a gene responsible for oxidative stress in the central nervous system. This study is the first to conclusively demonstrate both siRNA-carrier delivery and therapeutic efficacy in any CNS disease model where the BBB remains intact and thus offers new avenues for potential treatments of oxidative stress underlying neuroinflammation in a variety of neuropathologies that are currently refractory to existing therapies.

Cryo-EM structures of the SARS-CoV-2 endoribonuclease Nsp15 reveal insight into nuclease specificity and dynamics.

Nsp15, a uridine specific endoribonuclease conserved across coronaviruses, processes viral RNA to evade detection by host defense systems. Crystal structures of Nsp15 from different coronaviruses have shown a common hexameric assembly, yet how the enzyme recognizes and processes RNA remains poorly understood. Here we report a series of cryo-EM reconstructions of SARS-CoV-2 Nsp15, in both apo and UTP-bound states. The cryo-EM reconstructions, combined with biochemistry, mass spectrometry, and molecular dynamics, expose molecular details of how critical active site residues recognize uridine and facilitate catalysis of the phosphodiester bond. Mass spectrometry revealed the accumulation of cyclic phosphate cleavage products, while analysis of the apo and UTP-bound datasets revealed conformational dynamics not observed by crystal structures that are likely important to facilitate substrate recognition and regulate nuclease activity. Collectively, these findings advance understanding of how Nsp15 processes viral RNA and provide a structural framework for the development of new therapeutics.