Structural analysis of the SARS-CoV-2 methyltransferase complex involved in RNA cap creation bound to sinefungin

SARS-CoV-2 expresses a 2′-O RNA methyltransferase (MTase) that is involved in the viral RNA cap formation and therefore a target for antiviral therapy. Here the authors provide the structure of nsp10-nsp16 with the panMTase inhibitor sinefungin and report that the development of MTase inhibitor therapies that target multiple coronoaviruses is feasible

Rational design of highly potent SARS-CoV-2 nsp14 methyltransferase inhibitors

The search for new drugs against COVID-19 and its causative agent, SARS-CoV-2, is one of the major trends in current medicinal chemistry. Targeting capping machinery could be one of therapeutic concepts based on a unique mechanism of action. Viral RNA cap synthesis involves two methylation steps, the first of which is mediated by the nsp14 protein. Here, we rationally designed and synthesized a series of compounds capable of binding to both the S-adenosyl-L-methionine and the RNA binding site of SARS-CoV-2 nsp14 7-N methyltransferase. These hybrid molecules exerted excellent potency, high selectivity towards various human methyltransferases, they are nontoxic and highly cell permeable. Despite the outstanding activity against the enzyme, our compounds showed poor antiviral performance in vitro. This suggests that the activity of this viral methyltransferase is mainly associated with immune response. Our compounds represent unique tools to further explore the role of the SARS-CoV-2 nsp14 methyltransferase in viral replication

Membrane-depolarizing channel blockers induce selective glioma cell death by impairing nutrient transport and unfolded protein/amino acid responses.

Glioma-initiating cells (GIC) are considered the underlying cause of recurrences of aggressive glioblastomas, replenishing the tumor population and undermining the efficacy of conventional chemotherapy. Here we report the discovery that inhibiting T-type voltage-gated Ca2+ and KCa channels can effectively induce selective cell death of GIC and increase host survival in an orthotopic mouse model of human glioma. At present, the precise cellular pathways affected by the drugs affecting these channels are unknown. However, using cell-based assays and integrated proteomics, phosphoproteomics, and transcriptomics analyses, we identified the downstreamsignaling events these drugs affect. Changes in plasma membrane depolarization and elevated intracellular Na+, which compromised Na+-dependent nutrient transport, were documented. Deficits in nutrient deficit acted in turn to trigger the unfolded protein response and the amino acid response, leading ultimately to nutrient starvation and GIC cell death. Our results suggest new therapeutic targets to attack aggressive gliomas

PI(3,4)P2-mediated cytokinetic abscission prevents early senescence and cataract formation

Cytokinetic membrane abscission is a spatially and temporally regulated process that requires ESCRT (endosomal sorting complexes required for transport)-–dependent control of membrane remodeling at the midbody, a subcellular organelle that defines the cleavage site. Alteration of ESCRT function can lead to cataract, but the underlying mechanism and its relation to cytokinesis are unclear. We found a lens-specific cytokinetic process that required phosphatidylinositol-4-phosphate 3-kinase catalytic subunit type 2α (PI3K-C2α), its lipid product PI(3,4)P2 (phosphatidylinositol 3,4-bisphosphate), and the PI(3,4)P2-–binding ESCRT-II subunit VPS36 (vacuolar protein-sorting-–associated protein 36). Loss of each of these components led to impaired cytokinesis, triggering premature senescence in the lens of fish, mice, and humans. Thus, an evolutionarily conserved pathway underlies the cell type-–specific control of cytokinesis that helps to prevent early onset cataract by protecting from senescence