Bioorthogonal Metabolic Labeling Utilizing Protein Biosynthesis for Dynamic Visualization of Nonenveloped Enterovirus 71 Infection

Inhibition of lysosome-tethered Ragulator-Rag-3D complex restricts the replication of Enterovirus 71 and Coxsackie A16

Enterovirus 71 (EV71) and Coxsackie A16 (CVA16) are two major causative agents of hand, foot, and mouth disease (HFMD) in young children. However, the mechanisms regulating the replication and pathogenesis of EV71/CVA16 remain incompletely understood. We performed a genome-wide CRISPR-Cas9 knockout screen and identified Ragulator as a mediator of EV71-induced apoptosis and pyroptosis. The Ragulator-Rag complex is required for EV71 and CVA16 replication. Upon infection, the Ragulator-Rag complex recruits viral 3D protein to the lysosomal surface through the interaction between 3D and RagB. Disruption of the lysosome-tethered Ragulator-Rag-3D complex significantly impairs the replication of EV71/CVA16. We discovered a novel EV71 inhibitor, ZHSI-1, which interacts with 3D and significantly reduces the lysosomal tethering of 3D. ZHSI-1 treatment significantly represses replication of EV71/CVA16 as well as virus-induced pyroptosis associated with viral pathogenesis. Importantly, ZHSI-1 treatment effectively protects against EV71 infection in neonatal and young mice. Thus, our study indicates that targeting lysosome-tethered Ragulator-Rag-3D may be an effective therapeutic strategy for HFMD.

MAVS-Based Reporter Systems for Real-Time Imaging of EV71 Infection and Antiviral Testing

Enterovirus consists of a variety of viruses that could cause a wide range of illness in human. The pathogenesis of these viruses remains incompletely understood and no specific treatment is available. Better methods to study enterovirus infection in live cells will help us better understand the pathogenesis of these viruses and might contribute to antiviral development. Here in this study, we developed fluorescent cell-based reporter systems that allow sensitive distinction of individual cells infected with enterovirus 71 (EV71). More importantly, these systems could be easily used for live-cell imaging by monitoring viral-induced fluorescence translocation after EV71 infection. We further demonstrated that these reporter systems could be used to study other enterovirus-mediated MAVS cleavage and they are sensitive for antiviral activity testing. Therefore, integration of these reporters with modern image-based analysis has the potential to generate new insights into enterovirus infection and facilitate antiviral development.

An Engineered Escherichia coli Strain with Synthetic Metabolism for in-Cell Production of Translationally Active Methionine Derivatives

In the last decades, it has become clear that the canonical amino acid repertoire codified by the universal genetic code is not up to the needs of emerging biotechnologies. For this reason, extensive genetic code re-engineering is essential to expand the scope of ribosomal protein translation, leading to reprogrammed microbial cells equipped with an alternative biochemical alphabet to be exploited as potential factories for biotechnological purposes. The prerequisite for this to happen is a continuous intracellular supply of noncanonical amino acids through synthetic metabolism from simple and cheap precursors. We have engineered an Escherichia coli bacterial system that fulfills these requirements through reconfiguration of the methionine biosynthetic pathway and the introduction of an exogenous direct trans-sulfuration pathway. Our metabolic scheme operates in vivo, rescuing intermediates from core cell metabolism and combining them with small bio-orthogonal compounds. Our reprogrammed E. coli strain is capable of the in-cell production of l-azidohomoalanine, which is directly incorporated into proteins in response to methionine codons. We thereby constructed a prototype suitable for economic, versatile, green sustainable chemistry, pushing towards enzyme chemistry and biotechnology-based production.

Dual-Mode Fluorescence and Magnetic Resonance Imaging by Perylene Diimide-Based Gd-Containing Magnetic Ionic Liquids

Bioimaging plays a key role in the diagnosis/treatment of diseases and in scientific research studies. Compared with single imaging techniques, dual-mode and multimode imaging techniques facilitate high accuracy. In this work, a perylene diimide (PDI)-based Gd-containing magnetic ionic liquid, Per-6-Diimi[Gd(NO₃)₄], is reported for dual-modal imaging, in which a Gd(III) complex was used for magnetic resonance imaging (MRI), while PDI was used for fluorescence imaging. Because of the difference in the biological microenvironment, there is a switch between dispersed and aggregated states of Per-6-Diimi[Gd(NO₃)₄] molecules in hydrophobic and hydrophilic media. When it was in the aqueous solution, the intensive π-π interaction of PDI cores made Per-6-Diimi[Gd(NO₃)₄] aggregates to form particles. The paramagnetic nanoparticles ensure prolonging the rotational correlation time, which results in a strong enhancement of MRI with a longitude relaxation coefficient of 14.94 mM^-1 s^-1. In an in vivo MRI experiment, the tumor site is imaged by MRI through the enhanced permeability and retention effect. However, when the molecule is present on the hydrophobic membrane of the cells, the dispersed Per-6-Diimi[Gd(NO₃)₄] showed good fluorescence imaging capabilities due to the high fluorescence quantum yield of PDI. Thus, the fluorescence imaging of cells can be carried out. Moreover, ex vivo fluorescence imaging of organs is performed after MRI. Per-6-Diimi[Gd(NO₃)₄] is enriched in the liver, kidneys, and tumors.