A Covalent Chemical Probe for nsP2 Cysteine Protease with Antialphaviral Activity and Proteome-wide Selectivity.

RA-0003022 () was identified as a high-quality covalent chemical probe for nsP2 cysteine protease (nsP2pro). Isoxazole covalently captured the active site C478 and inactivated the enzyme with a / ratio of 6000 Ms. A negative control analog RA-0025453 () retained the covalent warhead but demonstrated >100-fold decrease in enzyme inhibition.

Lethal COVID-19 associates with RAAS-induced inflammation for multiple organ damage including mediastinal lymph nodes.

Lethal COVID-19 outcomes are attributed to classic cytokine storm. We revisit this using RNA sequencing of nasopharyngeal and 40 autopsy samples from patients dying of SARS-CoV-2. Subsets of the 100 top-upregulated genes in nasal swabs are upregulated in the heart, lung, kidney, and liver, but not mediastinal lymph nodes.

Hepatovirus translation requires PDGFA-associated protein 1, an eIF4E-binding protein regulating endoplasmic reticulum stress responses.

The overexpression and misfolding of viral proteins in the endoplasmic reticulum (ER) may cause cellular stress, thereby inducing a cytoprotective, proteostatic host response involving phosphorylation of eukaryotic translation initiation factor 2 subunit alpha (eIF2α). Here, we show that hepatitis A virus, a positive-strand RNA virus responsible for infectious hepatitis, adopts a stress-resistant, eIF2α-independent mechanism of translation to ensure the synthesis of viral proteins within the infected liver. Cap-independent translation directed by the hepatovirus internal ribosome entry site and productive hepatovirus infection of mice both require platelet-derived growth factor subunit A (PDGFA)-associated protein 1 (PDAP1), a small phosphoprotein of unknown function with eIF4E-binding activity.

Protein phosphatase 1 suppresses PKR/EIF2α signaling during human cytomegalovirus infection.

Human cytomegalovirus (HCMV) is a ubiquitous pathogen that infects the majority of the world's population. Lytic HCMV replication in immunocompromised individuals or neonates can lead to severe disease in multiple organ systems and even death. The establishment of lytic replication is driven by the first viral proteins expressed upon infection, the immediate early proteins, which play a key role in creating an intracellular environment conducive to virus replication.

The Human Cytomegalovirus vGPCR UL33 is Essential for Efficient Lytic Replication in Epithelial Cells.

Human cytomegalovirus (HCMV) is a β-herpesvirus which is ubiquitous in the human population. HCMV has the largest genome of all known human herpesviruses, and thus encodes a large array of proteins that affect pathogenesis in different cell types. Given the large genome and the ability of HCMV to replicate in a range of cells, investigators have begun to identify viral proteins required for cell type-specific replication.

Strategic Fluorination to Achieve a Potent, Selective, Metabolically Stable, and Orally Bioavailable Inhibitor of CSNK2.

The host kinase casein kinase 2 (CSNK2) has been proposed to be an antiviral target against β-coronaviral infection. To pharmacologically validate CSNK2 as a drug target in vivo, potent and selective CSNK2 inhibitors with good pharmacokinetic properties are required. Inhibitors based on the pyrazolo[1,5-]pyrimidine scaffold possess outstanding potency and selectivity for CSNK2, but bioavailability and metabolic stability are often challenging.

Structure Activity of β-Amidomethyl Vinyl Sulfones as Covalent Inhibitors of nsP2 Cysteine Protease with Antialphavirus Activity.

Despite their widespread impact on human health, there are no approved drugs for combating alphavirus infections. The heterocyclic β-aminomethyl vinyl sulfone RA-0002034 () is a potent irreversible covalent inhibitor of the alphavirus nsP2 cysteine protease with broad-spectrum antiviral activity. Analogs of that varied each of the three regions of the molecule were synthesized to establish structure-activity relationships for the inhibition of (CHIKV) nsP2 protease and viral replication.

Sub-genomic flaviviral RNA elements increase the stability and abundance of recombinant AAV vector transcripts.

Unlabelled: Many viruses have evolved structured RNA elements that can influence transcript abundance and translational efficiency, and help evade host immune factors by hijacking cellular machinery during replication. Here, we evaluated the functional impact of sub-genomic flaviviral RNAs (sfRNAs) known to stall exoribonuclease activity, by incorporating these elements into recombinant adeno-associated viral (AAV) genome cassettes. Specifically, sfRNAs from Dengue, Zika, Japanese Encephalitis, Yellow Fever, Murray Valley Encephalitis, and West Nile viruses increased transcript stability and transgene expression compared to a conventional woodchuck hepatitis virus element (WPRE).

More than an Amide Bioisostere: Discovery of 1,2,4-Triazole-containing Pyrazolo[1,5-]pyrimidine Host CSNK2 Inhibitors for Combatting β-Coronavirus Replication.

The pyrazolo[1,5-]pyrimidine scaffold is a promising scaffold to develop potent and selective CSNK2 inhibitors with antiviral activity against β-coronaviruses. Herein, we describe the discovery of a 1,2,4-triazole group to substitute a key amide group for CSNK2 binding present in many potent pyrazolo[1,5-]pyrimidine inhibitors. Crystallographic evidence demonstrates that the 1,2,4-triazole replaces the amide in forming key hydrogen bonds with Lys68 and a water molecule buried in the ATP-binding pocket.

A 44-Nucleotide Region in the Chikungunya Virus 3' UTR Dictates Viral Fitness in Disparate Host Cells.

We previously reported that deletion of a 44-nucleotide element in the 3' untranslated region (UTR) of the Chikungunya virus (CHIKV) genome enhances the virulence of CHIKV infection in mice. Here, we find that while this 44-nucleotide deletion enhances CHIKV fitness in murine embryonic fibroblasts in a manner independent of the type I interferon response, the same mutation decreases viral fitness in C6/36 mosquito cells. Further, the fitness advantage conferred by the UTR deletion in mammalian cells is maintained in vivo in a mouse model of CHIKV dissemination.

Structure Activity of β-Amidomethyl Vinyl Sulfones as Covalent Inhibitors of nsP2 Cysteine Protease with Anti-alphavirus Activity.

Despite their widespread impact on human health there are no approved drugs for combating alphavirus infections. The heterocyclic β-aminomethyl vinyl sulfone RA-0002034 () is a potent irreversible covalent inhibitor of the alphavirus nsP2 cysteine protease with broad spectrum antiviral activity. Analogs of that varied each of three regions of the molecule were synthesized to establish structure-activity relationships for inhibition of (CHIKV) nsP2 protease and viral replication.

mTOR signaling is required for phagocyte free radical production, GLUT1 expression, and control of infection.

Mammalian target of rapamycin (mTOR) is a key regulator of metabolism in the mammalian cell. Here, we show the essential role for mTOR signaling in the immune response to bacterial infection. Inhibition of mTOR during infection with revealed that mTOR signaling is required for bactericidal free radical production by phagocytes.

Discovery of a cell-active chikungunya virus nsP2 protease inhibitor using a covalent fragment-based screening approach.

Unlabelled: Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that has been responsible for numerous large-scale outbreaks in the last twenty years. Currently, there are no FDA-approved therapeutics for any alphavirus infection. CHIKV non-structural protein 2 (nsP2), which contains a cysteine protease domain, is essential for viral replication, making it an attractive target for a drug discovery campaign.

Synthesis of 5-Benzylamino and 5-Alkylamino-Substituted Pyrimido[4,5-c]quinoline Derivatives as CSNK2A Inhibitors with Antiviral Activity.

A series of 5-benzylamine-substituted pyrimido[4,5-c]quinoline derivatives of the CSNK2A chemical probe SGC-CK2-2 were synthesized with the goal of improving kinase inhibitor cellular potency and antiviral phenotypic activity while maintaining aqueous solubility. Among the range of analogs, those bearing electron-withdrawing ( and ) or donating () substituents on the benzyl ring as well as introduction of non-aromatic groups such as the cyclohexylmethyl () were shown to maintain CSNK2A activity. The CSNK2A activity was also retained with -methylation of SGC-CK2-2, but α-methyl substitution of the benzyl substituent led to a 10-fold reduction in potency.

Specific RNA structures in the 5' untranslated region of the human cytomegalovirus major immediate early transcript are critical for efficient virus replication.

Human cytomegalovirus (HCMV) requires the robust expression of two immediate early proteins, IE1 and IE2, immediately upon infection to suppress the antiviral response and promote viral gene expression. While transcriptional control of IE1 and IE2 has been extensively studied, the role of post-transcriptional regulation of IE1 and IE2 expression is relatively unexplored. We previously found that the shared major immediate early 5' untranslated region (MIE 5' UTR) of the mature IE1 and IE2 transcripts plays a critical role in facilitating the translation of the IE1 and IE2 mRNAs.

Optimization of 3-Cyano-7-cyclopropylamino-pyrazolo[1,5-]pyrimidines toward the Development of an In Vivo Chemical Probe for CSNK2A.

3-Cyano-7-cyclopropylamino-pyrazolo[1,5-]pyrimidines, including the chemical probe SGC-CK2-1, are potent and selective inhibitors of CSNK2A in cells but have limited utility in animal models due to their poor pharmacokinetic properties. While developing analogues with reduced intrinsic clearance and the potential for sustained exposure in mice, we discovered that phase II conjugation by GST enzymes was a major metabolic transformation in hepatocytes. A protocol for codosing with ethacrynic acid, a covalent reversible GST inhibitor, was developed to improve the exposure of analogue in mice.

Non-canonical function of histone methyltransferase G9a in the translational regulation of chronic inflammation.

We report a novel translation-regulatory function of G9a, a histone methyltransferase and well-understood transcriptional repressor, in promoting hyperinflammation and lymphopenia; two hallmarks of endotoxin tolerance (ET)-associated chronic inflammatory complications. Using multiple approaches, we demonstrate that G9a interacts with multiple translation regulators during ET, particularly the N6-methyladenosine (mA) RNA methyltransferase METTL3, to co-upregulate expression of certain mA-modified mRNAs that encode immune-checkpoint and anti-inflammatory proteins. Mechanistically, G9a promotes mA methyltransferase activity of METTL3 at translational/post-translational level by regulating its expression, its methylation, and its cytosolic localization during ET.

Human cytomegalovirus attenuates AKT activity by destabilizing insulin receptor substrate proteins.

Human cytomegalovirus (HCMV) requires inactivation of AKT to efficiently replicate, yet how AKT is shut off during HCMV infection has remained unclear. We show that UL38, an HCMV protein that activates mTORC1, is necessary and sufficient to destabilize insulin receptor substrate 1 (IRS1), a model insulin receptor substrate (IRS) protein. Degradation of IRS proteins in settings of excessive mTORC1 activity is an important mechanism for insulin resistance.

Investigation of the Host Kinome Response to Coronavirus Infection Reveals PI3K/mTOR Inhibitors as Betacoronavirus Antivirals.

Host kinases play essential roles in the host cell cycle, innate immune signaling, the stress response to viral infection, and inflammation. Previous work has demonstrated that coronaviruses specifically target kinase cascades to subvert host cell responses to infection and rely upon host kinase activity to phosphorylate viral proteins to enhance replication. Given the number of kinase inhibitors that are already FDA approved to treat cancers, fibrosis, and other human disease, they represent an attractive class of compounds to repurpose for host-targeted therapies against emerging coronavirus infections.

Praemonitus praemunitus: can we forecast and prepare for future viral disease outbreaks?

Understanding the origins of past and present viral epidemics is critical in preparing for future outbreaks. Many viruses, including SARS-CoV-2, have led to significant consequences not only due to their virulence, but also because we were unprepared for their emergence. We need to learn from large amounts of data accumulated from well-studied, past pandemics and employ modern informatics and therapeutic development technologies to forecast future pandemics and help minimize their potential impacts.