title: SNX-1 and RME-8 oppose the assembly of HGRS-1/ESCRT-0 degradative microdomains on endosomes.
abstract: After endocytosis, transmembrane cargo reaches endosomes, where it encounters complexes dedicated to opposing functions: recycling and degradation. Microdomains containing endosomal sorting complexes required for transport (ESCRT)-0 component Hrs [hepatocyte growth factor-regulated tyrosine kinase substrate (HGRS-1) in Caenorhabditis elegans] mediate cargo degradation, concentrating ubiquitinated cargo and organizing the activities of ESCRT. At the same time, retromer associated sorting nexin one (SNX-1) and its binding partner, J-domain protein RME-8, sort cargo away from degradation, promoting cargo recycling to the Golgi. Thus, we hypothesized that there could be important regulatory interactions between retromer and ESCRT that balance degradative and recycling functions. Taking advantage of the naturally large endosomes of the C. elegans coelomocyte, we visualized complementary ESCRT-0 and RME-8/SNX-1 microdomains in vivo and assayed the ability of retromer and ESCRT microdomains to regulate one another. We found in snx-1(0) and rme-8(ts) mutants increased endosomal coverage and intensity of HGRS-1-labeled microdomains, as well as increased total levels of HGRS-1 bound to membranes. These effects are specific to SNX-1 and RME-8, as loss of other retromer components SNX-3 and vacuolar protein sorting-associated protein 35 (VPS-35) did not affect HGRS-1 microdomains. Additionally, knockdown of hgrs-1 had little to no effect on SNX-1 and RME-8 microdomains, suggesting directionality to the interaction. Separation of the functionally distinct ESCRT-0 and SNX-1/RME-8 microdomains was also compromised in the absence of RME-8 and SNX-1, a phenomenon we observed to be conserved, as depletion of Snx1 and Snx2 in HeLa cells also led to greater overlap of Rme-8 and Hrs on endosomes.
authors.affiliation: Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, NJ 08854.
authors.forename: Anne
authors.initials: A
authors.lastname: Norris
authors.affiliation: Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08854.
authors.forename: Prasad
authors.initials: P
authors.lastname: Tammineni
authors.affiliation: Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, NJ 08854.
authors.forename: Simon
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, NJ 08854.
authors.forename: Julianne
authors.initials: J
authors.lastname: Gerdes
authors.affiliation: Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, NJ 08854.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Murr
authors.affiliation: Department of Cell Biology and Neuroscience, W. M. Keck Center for Collaborative Neuroscience, Rutgers University, Piscataway, NJ 08854.
authors.forename: Kelvin Y
authors.initials: KY
authors.lastname: Kwan
authors.affiliation: Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08854.
authors.forename: Qian
authors.initials: Q
authors.lastname: Cai
authors.affiliation: Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, NJ 08854; grant@biology.rutgers.edu.
authors.forename: Barth D
authors.initials: BD
authors.lastname: Grant
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D056827:Endosomal Sorting Complexes Required for Transport / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011992:Endosomes / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D006367:HeLa Cells; D006801:Humans; D018832:Molecular Chaperones; D010750:Phosphoproteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D054730:Protein Interaction Domains and Motifs; D021381:Protein Transport; D059748:Proteolysis; D034741:RNA, Small Interfering / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D058305:Sorting Nexins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D029742:Caenorhabditis elegans Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D018832:Molecular Chaperones; D010750:Phosphoproteins; C439316:RME-8 protein, C elegans; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; C545103:SNX-1 protein, C elegans; C513978:SNX1 protein, human; C513979:SNX2 protein, human; D058305:Sorting Nexins; C096164:hepatocyte growth factor-regulated tyrosine kinase substrate
keywords: Hrs; RME-8; SNX-1; clathrin; endosome