In vivo mapping of tissue- and subcellular-specific proteomes in Caenorhabditis elegans
Multicellular organisms are composed of tissues that have distinct functions requiring specialized proteomes. To define the proteome of a live animal with tissue and subcellular resolution, we adapted a localized proteomics technology for use in the multicellular model organism Caenorhabditis elegans. This approach couples tissue- and location-specific expression of the enzyme ascorbate peroxidase (APX), which facilitates proximity-based protein labeling in vivo, and quantitative proteomics to identify tissue- and subcellular-restricted proteomes. We identified and localized over 3000 proteins from strains of C. elegans expressing APX in either the nucleus or cytoplasm of the intestine, epidermis, body wall muscle, or pharyngeal muscle. We also identified several hundred proteins that were specifically localized to one of the four tissues analyzed or specifically localized to the cytoplasm or the nucleus. This approach resulted in the identification of both previously characterized and unknown nuclear and cytoplasmic proteins. Further, we confirmed the tissue- and subcellular-specific localization of a subset of identified proteins using GFP-tagging and fluorescence microscopy, validating our in vivo proximity-based proteomics technique. Together, these results demonstrate a new approach that enables the tissue- and subcellular-specific identification and quantification of proteins within a live animal.