Heme-containing peroxidases are important components of innate immunity. Many of them functionally associate with NADPH oxidase (NOX)/dual oxidase (DUOX) enzymes by using the hydrogen peroxide they generate in downstream reactions. Caenorhabditis elegans encodes for several heme peroxidases, and in a previous study we identified the ShkT-containing peroxidase, SKPO-1, as necessary for pathogen resistance. Here, we demonstrated that another peroxidase, HPX-2 ( H eme- P ero X idase 2), is required for resistance against some, but not all pathogens. Tissue specific RNA interference (RNAi) revealed that HPX-2 functionally localizes to the hypodermis of the worm. In congruence with this observation, hpx-2 mutant animals possessed a weaker cuticle structure, indicated by higher permeability to a DNA dye, but exhibited no obvious morphological defects. In addition, fluorescent labeling of HPX-2 revealed its expression in the pharynx, an organ in which BLI-3 is also present. Interestingly, loss of HPX-2 increased intestinal colonization of E . faecalis , suggesting its role in the pharynx may limit intestinal colonization. Moreover, disruption of a catalytic residue in the peroxidase domain of HPX-2 resulted in decreased survival on E . faecalis , indicating its peroxidase activity is required for pathogen resistance. Finally, RNA-seq analysis of an hpx-2 mutant revealed changes in genes encoding for cuticle structural components under the non-pathogenic conditions. Under pathogenic conditions, genes involved in infection response were differentially regulated to a greater degree, likely due to increased microbial burden. In conclusion, the characterization of the heme-peroxidase, HPX-2, revealed that it contributes to C . elegans pathogen resistance through a role in generating cuticle material in the hypodermis and pharynx. Author summary Reactive oxygen species (ROS) production by the host tissues is one of the first lines of defense when microbial infection occurs. ROS has been shown to be involved in multiple protective pathways in innate immunity. However, given the complexity of mammalian systems, the exact manner in which ROS are used for host defense remains incompletely understood. In this study, we use Caenorhabditis elegans as a simplified model system to decipher the protective functions of ROS in innate immunity. We describe a peroxidase, HPX-2, that protects C . elegans from multiple infectious microbes by strengthening barrier tissue. This finding brings insight into the mechanisms by which peroxidases utilizes ROS to contribute to innate immunity. With infectious diseases being one of the most important causes of morbidity and mortality around the world, understanding ROS production and its function in pathogen resistance will provide us with important information in developing new therapies against pathogens.
【초록키워드】 therapy, Infectious diseases, Innate immunity, Infection, oxygen, Infectious disease, DNA, Morphological, survival, pathogen, heme, morbidity, RNA interference, pathway, ROS, Pathogens, morbidity and mortality, mutant, hydrogen peroxide, information, expression, mechanism, function, reactive oxygen species, Protective, RNAi, NADPH oxidase, microbe, host defense, Disruption, microbial, Caenorhabditis elegans, peroxidase, hydrogen, peroxidases, observation, characterization, Reactions, tissue, enzyme, Author, residue, domain, complexity, pharynx, pathogenic, fluorescent, previous study, component, NADPH, organ, ROS production, Defense, RNA-seq analysis, elegans, hypodermis, microbial infection, worm, ENCODE, downstream, mammalian, labeling, Host, limit, intestinal, PROTECT, greater, shown, involved, indicated, addition, required, generate, exhibited, changes in, contribute, demonstrated, cause, regulated, conditions, elegan, Caenorhabditis elegan, genes encoding, catalytic, host tissue, 【제목키워드】 pathogen, Caenorhabditis elegans, peroxidase, PROTECT, Caenorhabditis elegan,