Alveolar macrophage- derived extracellular vesicles inhibit endosomal fusion of influenza virus

Alveolar macrophages (AMs) and epithelial cells (ECs) are the lone resident lung cells positioned to respond to pathogens at early stages of infection. Extracellular vesicles (EVs) are important vectors of paracrine signaling implicated in a range of (patho)physiologic contexts. Here we demonstrate that AMs, but not ECs, constitutively secrete paracrine activity localized to EVs which inhibits influenza infection of ECs in vitro and in vivo. AMs exposed to cigarette smoke extract lost the inhibitory activity of their secreted EVs. Influenza strains varied in their susceptibility to inhibition by AM- EVs. Only those exhibiting early endosomal escape and high pH of fusion were inhibited via a reduction in endosomal pH. By contrast, strains exhibiting later endosomal escape and lower fusion pH proved resistant to inhibition. These results extend our understanding of how resident AMs participate in host defense and have broader implications in the defense and treatment of pathogens internalized within endosomes.SynopsisExtracellular vesicles are emerging as homeostatic vectors, but poorly understood in influenza infection. Here, alveolar macrophage- derived extracellular vesicles inhibit influenza- endosome fusion in a strain- specific, and pH- dependent manner.Following initial infection of epithelial cells, the influenza virus traffics within host cell endosomes which undergo progressive acidification.Prior to gaining entry into the nucleus for its replication, influenza virus must fuse with endosome membranes- an event initiated at a strain- specific pH.Alveolar macrophages secrete extracellular vesicles which, when internalized by epithelial cells, lead to accelerated acidification of endosomes.Infection of epithelial cells by influenza strains which preferentially fuse with endosome membranes at high pH is inhibited by extracellular vesicles. Infection by influenza strains which fuse at low pH is unaffected by extracellular vesicles.Extracellular vesicles secreted from alveolar macrophages can promote acidification of endosomes in influenza virus- infected epithelial cells to inhibit viral replication.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156477/5/embj2020105057-sup-0002-EVFigs.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156477/4/embj2020105057_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156477/3/embj2020105057.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156477/2/embj2020105057-sup-0001-Appendix.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156477/1/embj2020105057.reviewer_comments.pd

α-amanitin resistance in Drosophila melanogaster: A genome-wide association approach

© This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication. We investigated the mechanisms of mushroom toxin resistance in the Drosophila Genetic Reference Panel (DGRP) fly lines, using genome-wide association studies (GWAS). While Drosophila melanogaster avoids mushrooms in nature, some lines are surprisingly resistant to α-amanitin-a toxin found solely in mushrooms. This resistance may represent a preadaptation, which might enable this species to invade the mushroom niche in the future. Although our previous microarray study had strongly suggested that pesticide-metabolizing detoxification genes confer α-amanitin resistance in a Taiwanese D. melanogaster line Ama-KTT, none of the traditional detoxification genes were among the top candidate genes resulting from the GWAS in the current study. Instead, we identified Megalin, Tequila, and widerborst as candidate genes underlying the α-amanitin resistance phenotype in the North American DGRP lines, all three of which are connected to the Target of Rapamycin (TOR) pathway. Both widerborst and Tequila are upstream regulators of TOR, and TOR is a key regulator of autophagy and Megalin-mediated endocytosis. We suggest that endocytosis and autophagy of α-amanitin, followed by lysosomal degradation of the toxin, is one of the mechanisms that confer α-amanitin resistance in the DGRP lines

Candidate genes resulting from the 180-line GWAS on 2.0 μg/g and the 37-line GWAS.

<p>Candidate genes resulting from the 180-line GWAS on 2.0 μg/g and the 37-line GWAS.</p

Larval viability variation in the DGRP lines in response to α-amanitin.

<p>The y-axis shows individual viability values, while the x-axis represents the individual DGRP lines. The lines are sorted from lowest α-amanitin resistance (left) to highest α-amanitin resistance (right). The error bars represent the standard error of the mean (SEM). A) 180 lines tested on 0.2 μg/g α-amanitin. (Individual line numbers are not shown but can be found in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0173162#pone.0173162.s001" target="_blank">S1 Table</a>). The y-axis represents the average number of flies hatched from 10 larvae placed on toxic food. B) 180 lines tested on 2.0 μg/g α-amanitin. (Individual line numbers are not shown but can be can be found in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0173162#pone.0173162.s001" target="_blank">S1 Table</a>). The y-axis represents the average hatch counts out of 10 larvae placed on toxic food. C). The y-axis represents the LC₅₀ values of the 37-line subset. The line numbers are shown on the x-axis.</p

Manhattan plots for the three GWAS.

<p>A) 37-line GWAS using LC₅₀ values, B) 180-line GWAS on 2.0 μg/g α-amanitin, C) 180-line GWAS on 0.2 μg/g α-amanitin. Selected significant gene names are printed on the top right of the corresponding dots in the graphs.</p