Influenza A virus, being responsible for seasonal epidemics and reoccurring pandemics, represents a worldwide threat to public health. High mutation rates facilitate the generation of viral escape mutants, rendering vaccines and drugs directed against virus-encoded targets potentially ineffective. In contrast, targeting host cell determinants temporarily dispensable for the host but crucial for virus replication could prevent viral escape. Here we report the discovery of 287 human host cell genes influencing influenza A virus replication in a genome-wide RNA interference (RNAi) screen. Using an independent assay we confirmed 168 hits (59%) inhibiting either the endemic H1N1 (119 hits) or the current pandemic swine-origin (121 hits) influenza A virus strains, with an overlap of 60%. Notably, a subset of these common hits was also essential for replication of a highly pathogenic avian H5N1 strain. In-depth analyses of several factors provided insights into their infection stage relevance. Notably, SON DNA binding protein (SON) was found to be important for normal trafficking of influenza virions to late endosomes early in infection. We also show that a small molecule inhibitor of CDC-like kinase 1 (CLK1) reduces influenza virus replication by more than two orders of magnitude, an effect connected with impaired splicing of the viral M2 messenger RNA. Furthermore, influenza-virus-infected p27(-/-) (cyclin-dependent kinase inhibitor 1B; Cdkn1b) mice accumulated significantly lower viral titres in the lung, providing in vivo evidence for the importance of this gene. Thus, our results highlight the potency of genome-wide RNAi screening for the dissection of virus-host interactions and the identification of drug targets for a broad range of influenza viruses.
Mycobacterium avium, one of the closest relatives of Mycobacterium tuberculosis (MTB), offers an advantage in studying MTB because of its tuberculosis-like effect in humans and host immune tolerance. This study examined the antimycobacterial action of ursolic acid and its regulation in macrophages during infection. Colony-forming units of the bacteria were determined in the cell lysate of macrophages and in the supernatant. The effect of ursolic acid on macrophages during infection was determined by analyzing the phosphorylation of the mitogen-activated protein kinase signaling pathway and the concentrations of tumor necrosis factor-α, interleukin-1β, interleukin-6, and nitrite. The colony-forming units analysis demonstrated that ursolic acid reduced the presence of Mycobacterium avium both intracellularly (in macrophages) and extracellularly. It decreased the levels of tumor necrosis factor-α and interleukin-6 but increased the concentrations of interleukin-1β and nitrite during infection. It also inhibited the phosphorylation of ERK1/2 but phosphorylated the C-Jun N-terminal kinase signaling pathway. The antimycobacterial effect of ursolic acid correlated with its ability to regulate the activation of macrophages. This dual ability made the ursolic acid-related elimination of the mycobacteria more effective.
The purpose of this study was to analyze the inhibitory action of ursolic acid (UA) as an antitubercular agent by computational docking studies and molecular dynamics simulations. The effect of UA on the cell wall of Mycobacterium tuberculosis (MTB) was evaluated by using Scanning Electron Microscopy (SEM). UA was used as a ligand for molecular interaction and investigate its binding activities to a group of proteins involved in the growth of MTB and the biosynthesis of the cell wall. Computational docking analysis was performed by using autodock 4.2.6 based on scoring functions. UA binding was confirmed by 30 ns molecular dynamics simulation using gromacs 5.1.1. H37Rv sensitive strain and isoniazid-resistant strain were used in the SEM study. UA showed to have the optimum binding affinity to inhA (Two-trans-enoyl-ACP reductase enzyme involved in elongation of fatty acid) with the binding energy of -9.2 kcal/mol. The dynamic simulation showed that the UA-inhA complex relatively stable and found to establish hydrogen bond with Thr196 and Ile194. SEM analysis confirms that UA treatment in both sensitive strain and resistant strain affected the morphology cell wall of MTB. This result indicated that UA could be one of the potential ligands for the development of new antituberculosis drugs.
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