Identification of microsporidia host-exposed proteins reveals a repertoire of large paralogous gene families and rapidly evolving proteins
Pathogens use a variety of secreted and surface proteins to interact with and manipulate their hosts, but a systematic approach for identifying such proteins has been lacking. To identify these host-exposed proteins, we used spatially restricted enzymatic tagging followed by mass spectrometry analysis of C. elegans infected with two species of Nematocida microsporidia. We identified 82 microsporidia proteins inside of intestinal cells, including several pathogen proteins in the nucleus. These microsporidia proteins are enriched in targeting signals, are rapidly evolving, and belong to large, Nematocida-specific gene families. We also find that large, species-specific families are common throughout microsporidia species. Our data suggest that the use of a large number of rapidly evolving species-specific proteins represents a common strategy for these intracellular pathogens to interact with their hosts. The unbiased method described here for identifying potential pathogen effectors represents a powerful approach for the study of a broad range of pathogens.