Mahoney, J. P. | bioRxiv Science

bioRxiv2025

Discovery and Characterization of a Hydroxypyridone-3-carboxamide Analog as an Antiviral Lead against Orthopoxviruses

Orthopoxviruses remain a persistent global health concern due to the ongoing circulation of mpox, the possibility of the re-emergence of smallpox, and the threats posed by many poxviruses that infect animals and/or humans. The limited availability of antiviral drugs, the unproven efficacy in humans, and the emergence of resistant mutants underscore the need for new and better therapeutics. In this study, we identify and characterize ZW-2038, a hydroxypyridone-3-carboxamide analog, as an antiviral compound against vaccinia virus (VACV), monkeypox virus (MPXV), and cowpox virus (CPXV). Discovered through a focused in-house small-molecule screen, ZW-2038 exhibited low micromolar potency and high selectivity in primary human fibroblasts. The compound also reduced viral replication under physiomimetic conditions including human and monkey intestinal organoids (enteroids) and ex vivo mouse lung tissue models. Mechanistically, ZW-2038 suppresses VACV DNA replication and downstream post-replicative gene expression, albeit without inhibiting MPXV resolvase (Mpr) in vitro. These findings, along with in vitro safety profiling and mice pharmacokinetics studies, characterize ZW-2038 as a promising yet suboptimal antiviral lead against orthopoxviruses warranting future development.

microbiology↗

bioRxiv2024

The co-receptor Tspan12 directly captures Norrin to promote ligand-specific β-catenin signaling

Wnt/{beta}-catenin signaling directs animal development and tissue renewal in a tightly controlled, cell- and tissue- specific manner. In the mammalian central nervous system, the atypical ligand Norrin controls angiogenesis and maintenance of the blood-brain barrier and blood-retina barrier through the Wnt/{beta}-catenin pathway. Like Wnt, Norrin activates signaling by binding and heterodimerizing the receptors Frizzled (Fzd) and Low-density lipoprotein receptor-related protein 5 or 6 (LRP5/6), leading to membrane recruitment of the intracellular transducer Dishevelled (Dvl) and ultimately stabilizing the transcriptional coactivator {beta}-catenin. Unlike Wnt, the cystine-knot ligand Norrin only signals through Fzd4 and additionally requires the co-receptor Tetraspanin12 (Tspan12); however, the mechanism underlying Tspan12-mediated signal enhancement is unclear. It has been proposed that Tspan12 integrates into the Norrin-Fzd4 complex to enhance Norrin-Fzd4 affinity or otherwise allosterically modulate Fzd4 signaling. Here, we measure direct, high-affinity binding between purified Norrin and Tspan12 in a lipid environment and use AlphaFold models to interrogate this interaction interface. We find that Tspan12 and Fzd4 can simultaneously bind Norrin and that a pre-formed Tspan12/Fzd4 heterodimer, as well as cells co-expressing Tspan12 and Fzd4, more efficiently capture low concentrations of Norrin than Fzd4 alone. We also show that Tspan12 competes with both heparan sulfate proteoglycans and LRP6 for Norrin binding and that Tspan12 does not impact Fzd4-Dvl affinity in the presence or absence of Norrin. Our findings suggest that Tspan12 does not allosterically enhance Fzd4 binding to Norrin or Dvl, but instead functions to directly capture Norrin upstream of signaling.

biochemistry↗