1. SNX-3 mediates retromer-independent tubular endosomal recycling by opposing EEA-1-facilitated trafficking.
- Author
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Tian Y, Kang Q, Shi X, Wang Y, Zhang N, Ye H, Xu Q, Xu T, and Zhang R
- Subjects
- ADP-Ribosylation Factor 6, ADP-Ribosylation Factors metabolism, Animals, Biological Transport, Caenorhabditis elegans cytology, Caenorhabditis elegans metabolism, Caenorhabditis elegans Proteins metabolism, Cell Membrane metabolism, Endosomal Sorting Complexes Required for Transport genetics, Endosomal Sorting Complexes Required for Transport metabolism, Epithelial Cells cytology, Gene Expression Regulation, HeLa Cells, Humans, Intestines cytology, Lysosomes metabolism, Phosphatidylinositol Phosphates metabolism, Protein Isoforms genetics, Protein Isoforms metabolism, Proteolysis, Signal Transduction, Sorting Nexins deficiency, Vesicular Transport Proteins metabolism, ADP-Ribosylation Factors genetics, Caenorhabditis elegans genetics, Caenorhabditis elegans Proteins genetics, Endosomes metabolism, Epithelial Cells metabolism, Sorting Nexins genetics, Vesicular Transport Proteins genetics
- Abstract
Early endosomes are the sorting hub on the endocytic pathway, wherein sorting nexins (SNXs) play important roles for formation of the distinct membranous microdomains with different sorting functions. Tubular endosomes mediate the recycling of clathrin-independent endocytic (CIE) cargoes back toward the plasma membrane. However, the molecular mechanism underlying the tubule formation is still poorly understood. Here we screened the effect on the ARF-6-associated CIE recycling endosomal tubules for all the SNX members in Caenorhabditis elegans (C. elegans). We identified SNX-3 as an essential factor for generation of the recycling tubules. The loss of SNX-3 abolishes the interconnected tubules in the intestine of C. elegans. Consequently, the surface and total protein levels of the recycling CIE protein hTAC are strongly decreased. Unexpectedly, depletion of the retromer components VPS-26/-29/-35 has no similar effect, implying that the retromer trimer is dispensable in this process. We determined that hTAC is captured by the ESCRT complex and transported into the lysosome for rapid degradation in snx-3 mutants. Interestingly, EEA-1 is increasingly recruited on early endosomes and localized to the hTAC-containing structures in snx-3 mutant intestines. We also showed that SNX3 and EEA1 compete with each other for binding to phosphatidylinositol-3-phosphate enriching early endosomes in Hela cells. Our data demonstrate for the first time that PX domain-only C. elegans SNX-3 organizes the tubular endosomes for efficient recycling and retrieves the CIE cargo away from the maturing sorting endosomes by competing with EEA-1 for binding to the early endosomes. However, our results call into question how SNX-3 couples the cargo capture and membrane remodeling in the absence of the retromer trimer complex., Competing Interests: The authors have declared that no competing interests exist.
- Published
- 2021
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