In vivo CRISPR screening identifies geranylgeranyl diphosphate as a pancreatic cancer tumor growth dependency.

Cancer cells must maintain lipid supplies for their proliferation and do so by upregulating lipogenic gene programs. The sterol regulatory element-binding proteins (SREBPs) act as modulators of lipid homeostasis by acting as transcriptional activators of genes required for fatty acid and cholesterol synthesis and uptake. SREBPs have been recognized as chemotherapeutic targets in multiple cancers, however it is not well understood which SREBP target genes are essential for tumorigenesis. Using parallel in vitro and in vivo CRISPR knockout screens, we identified terpenoid backbone biosynthesis genes as essential for pancreatic ductal adenocarcinoma (PDAC) tumor development. Specifically, we identified the non-sterol isoprenoid product of the mevalonate pathway, geranylgeranyl diphosphate (GGPP), as an essential lipid for tumor growth. Mechanistically, we observed that restricting mevalonate pathway activity using statins and SREBP inhibitors synergistically induced apoptosis and caused disruptions in small G protein prenylation that have pleiotropic effects on cellular signaling pathways. Finally, we demonstrated that geranylgeranyl diphosphate synthase 1 ( GGPS1 ) knockdown significantly reduces tumor burden in an orthotopic xenograft mouse model. These findings indicate that PDAC tumors selectively require GGPP over other lipids such as cholesterol and fatty acids and that this is a targetable vulnerability of pancreatic cancer cells.

SREBP-dependent regulation of lipid homeostasis is required for progression and growth of pancreatic ductal adenocarcinoma.

Metabolic reprogramming is a necessary component of oncogenesis and cancer progression that solid tumors undergo when their growth outstrips local nutrient supply. The supply of lipids such as cholesterol and fatty acids is required for continued tumor cell proliferation, and oncogenic mutations stimulate de novo lipogenesis to support tumor growth. Sterol regulatory element-binding protein (SREBP) transcription factors control cellular lipid homeostasis by activating genes required for lipid synthesis and uptake. SREBPs have been implicated in the progression of multiple cancers, including brain, breast, colon, liver, and prostate. However, the role the SREBP pathway and its central regulator SREBP cleavage activating protein (SCAP) in pancreatic ductal adenocarcinoma (PDAC) has not been studied in detail. Here, we demonstrated that pancreas-specific knockout of Scap has no effect on mouse pancreas development or function, allowing for examination of the role for Scap in the murine KPC model of PDAC. Notably, heterozygous loss of Scap prolonged survival in KPC mice, and homozygous loss of Scap impaired PDAC tumor progression. Using subcutaneous and orthotopic xenograft models, we showed that S CAP is required for human PDAC tumor growth. Mechanistically, chemical or genetic inhibition of the SREBP pathway prevented PDAC cell growth under low serum conditions due to a lack of lipid supply. Highlighting the clinical importance of this pathway, the SREBP pathway is broadly required for cancer cell growth, SREBP target genes are upregulated in human PDAC tumors, and increased expression of SREBP targets genes is associated with poor survival in PDAC patients. Collectively, these results demonstrate that SCAP and the SREBP pathway activity are essential for PDAC cell and tumor growth in vitro and in vivo , identifying SCAP as a potential therapeutic target for PDAC. SIGNIFICANCE: Our findings demonstrate that SREBP pathway activation is a critical part of the metabolic reprogramming that occurs in PDAC development and progression. Therefore, targeting the SREBP pathway has significant therapeutic potential.

Accessory subunit NDUFB4 participates in mitochondrial complex I supercomplex formation.

Mitochondrial electron transport chain complexes organize into supramolecular structures called respiratory supercomplexes (SCs). The role of respiratory SCs remains largely unconfirmed despite evidence supporting their necessity for mitochondrial respiratory function. The mechanisms underlying the formation of the I1III2IV1 "respirasome" SC are also not fully understood, further limiting insights into these processes in physiology and diseases, including neurodegeneration and metabolic syndromes. NDUFB4 is a complex I accessory subunit that contains residues that interact with the subunit UQCRC1 from complex III, suggesting that NDUFB4 is integral for I1III2IV1 respirasome integrity. Here, we introduced specific point mutations to Asn24 (N24) and Arg30 (R30) residues on NDUFB4 to decipher the role of I1III2-containing respiratory SCs in cellular metabolism while minimizing the functional consequences to complex I assembly. Our results demonstrate that NDUFB4 point mutations N24A and R30A impair I1III2IV1 respirasome assembly and reduce mitochondrial respiratory flux. Steady-state metabolomics also revealed a global decrease in citric acid cycle metabolites, affecting NADH-generating substrates. Taken together, our findings highlight an integral role of NDUFB4 in respirasome assembly and demonstrate the functional significance of SCs in regulating mammalian cell bioenergetics.

Erratum: Comparison of Cardiovascular Pathology in Animal Models of SARS-CoV-2 Infection: Recommendations Regarding Standardization of Research Methods.

This corrects the article DOI: 10.30802/AALAS-CM-22-000095
In the original article entitled "Comparison of CardiovascularPathology in Animal Models of SARS-CoV-2 Infection:Recommendations Regarding Standardization of ResearchMethods," published in Vol 73, Issue 1 (February 2023),the grant information appearing in the Acknowledgmentssection should read: We acknowledge training supportfrom the National Institutes of Health (T32 OD011089) forIAJ and SM.

Non-Invasive Ultrasound Assessment of Endometrial Cancer Progression in Pax8-Directed Deletion of the Tumor Suppressors Arid1a and Pten in Mice.

Uterine cancers can be studied in mice due to the ease of handling and genetic manipulation in these models. However, these studies are often limited to assessing pathology post-mortem in animals euthanized at multiple time points in different cohorts, which increases the number of mice needed for a study. Imaging mice in longitudinal studies can track the progression of disease in individual animals, reducing the number of mice needed. Advances in ultrasound technology have allowed for the detection of micrometer-level changes in tissues. Ultrasound has been used to study follicle maturation in ovaries and xenograft growth but has not been applied to morphological changes in the mouse uterus. This protocol examines the juxtaposition of pathology with in vivo imaging comparisons in an induced endometrial cancer mouse model. The features observed by ultrasound were consistent with the degree of change seen by gross pathology and histology. Ultrasound was found to be highly predictive of the observed pathology, supporting the incorporation of ultrasonography into longitudinal studies of uterine diseases such as cancer in mice.

α7 Nicotinic acetylcholine receptor potentiation downregulates chemotherapy-induced inflammatory overactivation by overlapping intracellular mechanisms.

We studied, using a combination of animal and cellular models, the glial mechanisms underlying the anti-neuropathic and anti-inflammatory properties of PAM-2 [(E)-3-furan-2-yl-N-p-tolyl-acrylamide], a positive allosteric modulator of α7 nicotinic acetylcholine receptors (nAChRs). In mice, PAM-2 decreased the inflammatory process induced by the combination of oxaliplatin (OXA), a chemotherapeutic agent, and interleukin-1ß (IL-1ß), a pro-inflammatory molecule. In the brain and spinal cord of treated animals, PAM-2 reduced pro-inflammatory cytokines/chemokines by mechanisms involving mRNA downregulation of factors in the toll-like receptor 4 (TLR4)/nuclear factor (NF)-κB pathway, and increased the precursor of brain-derived neurotrophic factor (proBDNF). To determine the molecular mechanisms underlying the anti-inflammatory activity of PAM-2, both human C20 microglia and normal human astrocytes (NHA) were used. The results showed that PAM-2-induced potentiation of glial α7 nAChRs decreases OXA/IL-1ß-induced overexpression of inflammatory molecules by different mechanisms, including mRNA downregulation of factors in the NF-κB pathway (in microglia and astrocyte) and ERK (only in microglia). The OXA/IL-1ß-mediated reduction in proBDNF was prevented by PAM-2 in microglia, but not in astrocytes. Our findings also indicate that OXA/IL-1ß-induced organic cation transporter 1 (OCT1) expression is decreased by PAM-2, suggesting that decreased OXA influx may be involved in the protective effects of PAM-2. The α7-selective antagonist methyllycaconitine blocked the most important effects mediated by PAM-2 at both animal and cellular levels, supporting a mechanism involving α7 nAChRs. In conclusion, glial α7 nAChR stimulation/potentiation downregulates neuroinflammatory targets, and thereby remains a promising therapeutic option for cancer chemotherapy-induced neuroinflammation and neuropathic pain.

Comparison of Cardiovascular Pathology In Animal Models of SARS-CoV-2 Infection: Recommendations Regarding Standardization of Research Methods.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged as the viral pathogen that led to the global COVID-19 pandemic that began in late 2019. Because SARS-CoV-2 primarily causes a respiratory disease, much research conducted to date has focused on the respiratory system. However, SARS-CoV-2 infection also affects other organ systems, including the cardiovascular system. In this critical analysis of published data, we evaluate the evidence of cardiovascular pathology in human patients and animals. Overall, we find that the presence or absence of cardiovascular pathology is reported infrequently in both human autopsy studies and animal models of SARS-CoV-2 infection. Moreover, in those studies that have reported cardiovascular pathology, we identified issues in their design and execution that reduce confidence in the conclusions regarding SARS-CoV-2 infection as a cause of significant cardiovascular pathology. Throughout this overview, we expand on these limitations and provide recommendations to ensure a high level of scientific rigor and reproducibility.

Anti-inflammatory effects of ß-FNA are sex-dependent in a pre-clinical model of LPS-induced inflammation.

BACKGROUND: Inflammation is present in neurological and peripheral disorders. Thus, targeting inflammation has emerged as a viable option for treating these disorders. Previous work indicated pretreatment with beta-funaltrexamine (ß-FNA), a selective mu-opioid receptor (MOR) antagonist, inhibited inflammatory signaling in vitro in human astroglial cells, as well as lipopolysaccharide (LPS)-induced neuroinflammation and sickness-like-behavior in mice. This study explores the protective effects of ß-FNA when treatment occurs 10 h after LPS administration and is the first-ever investigation of the sex-dependent effects of ß-FNA on LPS-induced inflammation in the brain and peripheral tissues, including the intestines. RESULTS: Male and female C57BL/6J mice were administered LPS followed by treatment with ß-FNA-immediately or 10 h post-LPS. Sickness- and anxiety-like behavior were assessed using an open-field test and an elevated-plus-maze test, followed by the collection of whole brain, hippocampus, prefrontal cortex, cerebellum/brain stem, plasma, spleen, liver, large intestine (colon), proximal small intestine, and distal small intestine. Levels of inflammatory chemokines/cytokines (interferon γ-induced-protein, IP-10 (CXCL10); monocyte-chemotactic-protein 1, MCP-1 (CCL2); interleukin-6, IL-6; interleukin-1ß, IL-1ß; and tumor necrosis factor-alpha, TNF-α) in tissues were measured using an enzyme-linked immunosorbent assay. Western blot analysis was used to assess nuclear factor-kappa B (NF-κB) expression. There were sex-dependent differences in LPS-induced inflammation across brain regions and peripheral tissues. Overall, LPS-induced CXCL10, CCL2, TNF-α, and NF-κB were most effectively downregulated by ß-FNA; and ß-FNA effects differed across brain regions, peripheral tissues, timing of the dose, and in some instances, in a sex-dependent manner. ß-FNA reduced LPS-induced anxiety-like behavior most effectively in female mice. CONCLUSION: These findings provide novel insights into the sex-dependent anti-inflammatory effects of ß-FNA and advance this agent as a potential therapeutic option for reducing both neuroinflammation an intestinal inflammation.

Anti-inflammatory actions of ß-funaltrexamine in a mouse model of lipopolysaccharide-induced inflammation.

Neuroinflammation is involved in a wide range of brain disorders, thus there is great interest in identifying novel anti-inflammatory agents to include in therapeutic strategies. Our previous in vitro studies revealed that beta-funaltrexamine (ß-FNA), a well-characterized selective mu-opioid receptor (MOR) antagonist, inhibits inflammatory signaling in human astroglial cells, albeit through an apparent MOR-independent mechanism. We also previously determined that lipopolysaccharide (LPS)-induced sickness behavior and neuroinflammation in mice are prevented by pretreatment with ß-FNA. Herein we investigated the temporal importance of ß-FNA treatment in this pre-clinical model of LPS-induced neuroinflammation. Adult, male C57BL/6J mice were administered an i.p. injection of LPS followed by treatment (i.p. injection) with ß-FNA immediately or 4 h post-LPS. Sickness behavior was assessed using an open-field test, followed by assessment of inflammatory signaling in the brain, spleen, and plasma. Levels of inflammatory chemokines/cytokines (interferon γ-induced protein, CXCL10; monocyte chemotactic protein 1, CCL2; and interleukin-6, IL-6) in tissues were measured using an enzyme-linked immunosorbent assay and nuclear factor-kappa B (NFκB), p38 mitogen activated kinase (p38 MAPK), and glial fibrillary acidic protein (GFAP) expression were measured by western blot. LPS-induced sickness behavior and chemokine expression were inhibited more effectively when ß-FNA treatment occurred immediately after LPS administration, as opposed to 4 h post-LPS; and ß-FNA-mediated effects were time-dependent as evidenced by inhibition at 24 h, but not at 8 h. The inhibitory effects of ß-FNA on chemokine expression were more evident in the brain versus the spleen or plasma. LPS-induced NFκB-p65 and p38 MAPK expression in the brain and spleen were inhibited at 8 and 24 h post-LPS. These findings extend our understanding of the anti-inflammatory effects of ß-FNA and warrant further investigation into its therapeutic potential.

Impact of Referring Team Characteristics on Inpatient Palliative Care Consultation Rate at a Comprehensive Cancer Center.

Background: No prior study addresses the impact of admitting team characteristics on inpatient palliative care (PC) consultation rate in cancer patients. Understanding consultation rate differences among admitting service types may reveal PC access disparities for patients who would benefit from consultation. Aim: To determine the impact of admitting service characteristics (teaching vs. nonteaching and surgical vs. medical) on inpatient PC consultation rates. Methods: A six-month cross-sectional study was performed at an academic comprehensive cancer center. Inpatient PC consultations and follow-up visits were compared to total admissions by admitting service category. Results: Five thousand six hundred ninety-seven admissions resulted in 710 new PC consultations and 2494 follow-up visits. Patients admitted to medical services had highest odds of PC consultation, while data for teaching services were mixed. There was no difference in follow-up visits. Conclusions: Significant differences between medical and surgical service PC consultation rates may indicate specialty PC access disparities solely based on their admitting service.

Parallel Optimization of Potency and Pharmacokinetics Leading to the Discovery of a Pyrrole Carboxamide ERK5 Kinase Domain Inhibitor.

The nonclassical extracellular signal-related kinase 5 (ERK5) mitogen-activated protein kinase pathway has been implicated in increased cellular proliferation, migration, survival, and angiogenesis; hence, ERK5 inhibition may be an attractive approach for cancer treatment. However, the development of selective ERK5 inhibitors has been challenging. Previously, we described the development of a pyrrole carboxamide high-throughput screening hit into a selective, submicromolar inhibitor of ERK5 kinase activity. Improvement in the ERK5 potency was necessary for the identification of a tool ERK5 inhibitor for target validation studies. Herein, we describe the optimization of this series to identify nanomolar pyrrole carboxamide inhibitors of ERK5 incorporating a basic center, which suffered from poor oral bioavailability. Parallel optimization of potency and in vitro pharmacokinetic parameters led to the identification of a nonbasic pyrazole analogue with an optimal balance of ERK5 inhibition and oral exposure.

Progesterone receptor membrane component 1 (PGRMC1) binds and stabilizes cytochromes P450 through a heme-independent mechanism.

Progesterone receptor membrane component 1 (PGRMC1) is a heme-binding protein implicated in a wide range of cellular functions. We previously showed that PGRMC1 binds to cytochromes P450 in yeast and mammalian cells and supports their activity. Recently, the paralog PGRMC2 was shown to function as a heme chaperone. The extent of PGRMC1 function in cytochrome P450 biology and whether PGRMC1 is also a heme chaperone are unknown. Here, we examined the function of Pgrmc1 in mouse liver using a knockout model and found that Pgrmc1 binds and stabilizes a broad range of cytochromes P450 in a heme-independent manner. Proteomic and transcriptomic studies demonstrated that Pgrmc1 binds more than 13 cytochromes P450 and supports maintenance of cytochrome P450 protein levels posttranscriptionally. In vitro assays confirmed that Pgrmc1 KO livers exhibit reduced cytochrome P450 activity consistent with reduced enzyme levels. Mechanistic studies in cultured cells demonstrated that PGRMC1 stabilizes cytochromes P450 and that binding and stabilization do not require PGRMC1 binding to heme. Importantly, Pgrmc1-dependent stabilization of cytochromes P450 is physiologically relevant, as Pgrmc1 deletion protected mice from acetaminophen-induced liver injury. Finally, evaluation of Y113F mutant Pgrmc1, which lacks the axial heme iron-coordinating hydroxyl group, revealed that proper iron coordination is not required for heme binding, but is required for binding to ferrochelatase, the final enzyme in heme biosynthesis. PGRMC1 was recently identified as the causative mutation in X-linked isolated pediatric cataract formation. Together, these results demonstrate a heme-independent function for PGRMC1 in cytochrome P450 stability that may underlie clinical phenotypes.

Work Characteristics, Body Mass Index, and Risk of Obesity: The National Quality of Work Life Survey.

OBJECTIVES: To examine work characteristics in relation to body mass index (BMI) and risk of obesity. METHODS: We analyzed data from 1150 participants working 20+ h week-1 from the 2014 National NIOSH Quality of Work Life Survey, based on a representative sample of US workers. We used multiple linear regression for BMI and multiple logistic regression for obesity to estimate associations with 19 different work characteristics plus one set of occupational categories controlling for age, gender, race/ethnicity, education, marital status, job physical exertion, and television watching. RESULTS: We found significant positive linear associations between BMI and night shift (versus day shift) schedule (B = 2.28, P = 0.008) and blue-collar (versus management/professional) work (B = 1.75, P = 0.008). Night shift schedule [odds ratio (OR) = 2.19, P = 0.029], sales/office work (OR = 1.55, P = 0.040), and blue-collar work (OR = 2.63, P = 0.006) were associated with increased risk of obesity versus 'healthy weight'. No other statistically significant associations between work characteristics and BMI or obesity were observed. CONCLUSIONS: Night shift schedule and blue-collar work were related to increased BMI and obesity risk in US workers in 2014. Identifying risk factors in blue-collar work and redesigning jobs to reduce those risk factors, and reducing night shift work, could play a role in reducing the prevalence of obesity in the USA.

Identification of a novel orally bioavailable ERK5 inhibitor with selectivity over p38α and BRD4.

Extracellular regulated kinase 5 (ERK5) signalling has been implicated in driving a number of cellular phenotypes including endothelial cell angiogenesis and tumour cell motility. Novel ERK5 inhibitors were identified using high throughput screening, with a series of pyrrole-2-carboxamides substituted at the 4-position with an aroyl group being found to exhibit IC50 values in the micromolar range, but having no selectivity against p38α MAP kinase. Truncation of the N-substituent marginally enhanced potency (∼3-fold) against ERK5, but importantly attenuated inhibition of p38α. Systematic variation of the substituents on the aroyl group led to the selective inhibitor 4-(2-bromo-6-fluorobenzoyl)-N-(pyridin-3-yl)-1H-pyrrole-2-carboxamide (IC50 0.82 µM for ERK5; IC50 > 120 µM for p38α). The crystal structure (PDB 5O7I) of this compound in complex with ERK5 has been solved. This compound was orally bioavailable and inhibited bFGF-driven Matrigel plug angiogenesis and tumour xenograft growth. The selective ERK5 inhibitor described herein provides a lead for further development into a tool compound for more extensive studies seeking to examine the role of ERK5 signalling in cancer and other diseases.

Changes in work characteristics over 12 years: Findings from the 2002-2014 US National NIOSH Quality of Work Life Surveys.

OBJECTIVES: To assess changes in work characteristics, socioeconomic status inequalities in changes in work characteristics, and whether US workplaces are becoming more stressful. METHODS: We analyzed data from 5361 employed participants from the 2002, 2006, 2010, and 2014 NIOSH Quality of Work Life Surveys, based on representative samples of US workers. We used regression analyses to assess changes in job characteristics, adjusting for age, sex, race/ethnicity, education, work hours, and unemployment rate. For the regression analyses with continuous job characteristics, we created standardized variables allowing for the magnitude of changes to be directly compared between job characteristics. RESULTS: Over the period 2002-2014, we observed statistically significant increases in job strain (+0.09 standard deviations (SD), P = 0.02), low job control (+0.10 SD, P = 0.03), and work-family conflict (+0.15 SD, P = 0.001). No significant changes were observed for high job demand, low social support, and low reward. The largest increase in low job control was seen among service workers. CONCLUSIONS: The increase in two cardiovascular disease risk factors, job strain, and low job control, might partially explain the slowing of the decline in US heart disease and stroke mortality rates.

Murine obscurin and Obsl1 have functionally redundant roles in sarcolemmal integrity, sarcoplasmic reticulum organization, and muscle metabolism.

Biological roles of obscurin and its close homolog Obsl1 (obscurin-like 1) have been enigmatic. While obscurin is highly expressed in striated muscles, Obsl1 is found ubiquitously. Accordingly, obscurin mutations have been linked to myopathies, whereas mutations in Obsl1 result in 3M-growth syndrome. To further study unique and redundant functions of these closely related proteins, we generated and characterized Obsl1 knockouts. Global Obsl1 knockouts are embryonically lethal. In contrast, skeletal muscle-specific Obsl1 knockouts show a benign phenotype similar to obscurin knockouts. Only deletion of both proteins and removal of their functional redundancy revealed their roles for sarcolemmal stability and sarcoplasmic reticulum organization. To gain unbiased insights into changes to the muscle proteome, we analyzed tibialis anterior and soleus muscles by mass spectrometry, uncovering additional changes to the muscle metabolism. Our analyses suggest that all obscurin protein family members play functions for muscle membrane systems.

Binding to an Unusual Inactive Kinase Conformation by Highly Selective Inhibitors of Inositol-Requiring Enzyme 1α Kinase-Endoribonuclease.

A series of imidazo[1,2- b]pyridazin-8-amine kinase inhibitors were discovered to allosterically inhibit the endoribonuclease function of the dual kinase-endoribonuclease inositol-requiring enzyme 1α (IRE1α), a key component of the unfolded protein response in mammalian cells and a potential drug target in multiple human diseases. Inhibitor optimization gave compounds with high kinome selectivity that prevented endoplasmic reticulum stress-induced IRE1α oligomerization and phosphorylation, and inhibited endoribonuclease activity in human cells. X-ray crystallography showed the inhibitors to bind to a previously unreported and unusually disordered conformation of the IRE1α kinase domain that would be incompatible with back-to-back dimerization of the IRE1α protein and activation of the endoribonuclease function. These findings increase the repertoire of known IRE1α protein conformations and can guide the discovery of highly selective ligands for the IRE1α kinase site that allosterically inhibit the endoribonuclease.

Altered myocyte contractility and calcium homeostasis in alpha-myosin heavy chain point mutations linked to familial dilated cardiomyopathy.

Mutations in the human cardiac motor protein beta-myosin heavy chain (ßMHC) have been long recognized as a cause of familial hypertrophic cardiomyopathy. Recently, mutations (P830L and A1004S) in the less abundant but faster isoform alpha-myosin heavy chain (αMHC) have been linked to dilated cardiomyopathy (DCM). In this study, we sought to determine the cellular contractile phenotype associated with these point mutations. Ventricular myocytes were isolated from 2 month male Sprague Dawley rats. Cells were cultured in M199 media and infected with recombinant adenovirus containing the P830L or the A1004S mutant human αMHC at a MOI of 500 for 18 h. Uninfected cells (UI), human ßMHC (MOI 500, 18 h), and human αMHC (MOI 500, 18 h) were used as controls. Cells were loaded with fura-2 (1 µM, 15 min) after 48 h. Sarcomere shortening and calcium transients were recorded in CO2 buffered M199 media (36°±1 C) with and without 10 nM isoproterenol (Iso). The A1004S mutation resulted in decreased peak sarcomere shortening while P830L demonstrated near normal shortening kinetics at baseline. In the presence of Iso, the A1004S sarcomere shortening was identical to the ßMHC shortening while the P830L was identical to the αMHC control. All experimental groups had identical calcium transients. Despite a shared association with DCM, the P830L and A1004S αMHC mutations alter myocyte contractility in completely different ways while at the same preserving peak intracellular calcium.

High-Throughput Screening and Hit Validation of Extracellular-Related Kinase 5 (ERK5) Inhibitors.

The extracellular-related kinase 5 (ERK5) is a promising target for cancer therapy. A high-throughput screen was developed for ERK5, based on the IMAP FP progressive binding system, and used to identify hits from a library of 57 617 compounds. Four distinct chemical series were evident within the screening hits. Resynthesis and reassay of the hits demonstrated that one series did not return active compounds, whereas three series returned active hits. Structure-activity studies demonstrated that the 4-benzoylpyrrole-2-carboxamide pharmacophore had excellent potential for further development. The minimum kinase binding pharmacophore was identified, and key examples demonstrated good selectivity for ERK5 over p38α kinase.

SAMHD1 transcript upregulation during SIV infection of the central nervous system does not associate with reduced viral load.

Restriction of HIV-1 in myeloid-lineage cells is attributed in part to the nucleotidase activity of the SAM-domain and HD-domain containing protein (SAMHD1), which depletes free nucleotides, blocking reverse transcription. In the same cells, the Vpx protein of HIV-2 and most SIVs counteracts SAMHD1. Both Type I and II interferons may stimulate SAMHD1 transcription. The contributions of SAMHD1 to retroviral restriction in the central nervous system (CNS) have been the subject of limited study. We hypothesized that SAMHD1 would respond to interferon in the SIV-infected CNS but would not control virus due to SIV Vpx. Accordingly, we investigated SAMHD1 transcript abundance and association with the Type I interferon response in an SIV model. SAMHD1 transcript levels were IFN responsive, increasing during acute phase infection and decreasing during a more quiescent phase, but generally remaining elevated at all post-infection time points. In vitro, SAMHD1 transcript was abundant in macaque astrocytes and further induced by Type I interferon, while IFN produced a weaker response in the more permissive environment of the macrophage. We cannot rule out a contribution of SAMHD1 to retroviral restriction in relatively non-permissive CNS cell types. We encourage additional research in this area, particularly in the context of HIV-1 infection.