Following endocytosis, receptors that are internalized to sorting endosomes (SE) are sorted to different pathways, in part by sorting nexin (SNX) proteins. Notably, SNX17 interacts with a multitude of receptors in a sequence-specific manner to regulate their recycling. However, the mechanisms by which SNX17-labeled vesicles that contain sorted receptors bud and undergo vesicular fission from the SE remain elusive. Recent studies suggest that a dynamin-homolog, Eps15 homology domain protein 1, catalyzes fission and releases endosome-derived vesicles for recycling to the plasma membrane. However, the mechanism by which EHD1 is coupled to various receptors and regulates their recycling remains unknown. Herein, we ... More
Following endocytosis, receptors that are internalized to sorting endosomes (SE) are sorted to different pathways, in part by sorting nexin (SNX) proteins. Notably, SNX17 interacts with a multitude of receptors in a sequence-specific manner to regulate their recycling. However, the mechanisms by which SNX17-labeled vesicles that contain sorted receptors bud and undergo vesicular fission from the SE remain elusive. Recent studies suggest that a dynamin-homolog, Eps15 homology domain protein 1, catalyzes fission and releases endosome-derived vesicles for recycling to the plasma membrane. However, the mechanism by which EHD1 is coupled to various receptors and regulates their recycling remains unknown. Herein, we sought to characterize the mechanism by which EHD1 couples with SNX17 to regulate the recycling of SNX17-interacting receptors. We hypothesized that SNX17 couples receptors to the EHD1 fission machinery in mammalian cells. Co-immunoprecipitation experiments and in vitro assays provided evidence that EHD1 and SNX17 directly interact. We also found that inducing internalization of a SNX17 cargo receptor, low density lipoprotein receptor related protein 1 (LRP1), led to recruitment of cytoplasmic EHD1 to endosomal membranes. Moreover, surface rendering and quantification of overlap volumes indicated that SNX17 and EHD1 partially co-localize on endosomes and that this overlap further increases upon LRP1 internalization. Additionally, SNX17-containing endosomes were larger in EHD1-depleted cells than in wild-type cells, suggesting that EHD1 depletion impairs SNX17-mediated endosomal fission. Our findings help clarify our current understanding of endocytic trafficking, providing significant additional insight into the process of endosomal fission and connecting the sorting and fission machineries.,Published under license by The American Society for Biochemistry and Molecular Biology, Inc.
