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.endosome | SNX-1 | RME-8 | Hrs | clathrin

Distinct effects on the dendritic arbor occur by microbead versus bath administration of brain-derived neurotrophic factor

“…with sequential-acquisition setting. Approximately ten images were taken in 1 μm sections from the top to the bottom of the beads [30,31]. Additionally, STORM/PALM was set up on an Olympus IX73 with an LED excitation light source as previously described [31].…”

“…Five thousand images were acquired for each field of view. Blinking events were identified by the change in fluorescence at individual pixels [31]. Centroid determination and image reconstruction were completed using QuickPALM [32].…”

Role of the endolysosomal system in Parkinson’s disease

“…Nigral Lewy bodies were also found to be co‐localized with RME‐8 (Vilarino‐Guell et al ). Unlike other DNAJC proteins implicated in PD, in vitro studies have revealed that the DNAJC13 mutation confers toxic gain‐of‐function, leading to E‐L cargo trafficking deficits (Norris et al ). The DNAJC13 mutation is also predicted to affect overall endosomal trafficking, even in the soma and postsynaptic compartment (Vilarino‐Guell et al ), unlike the synapse‐specific dysfunction predicted for auxilin.…”

Actin-dependent endosomal receptor recycling

“…The limiting membrane of endosomes is considered to comprise a patchwork of different functional protein-based and lipid-based domains. These include the aforementioned degradative subdomain, enriched with the components of the ESCRT machinery, and the retrieval subdomain, enriched with retromer and other cargoretrieval complexes [60][61][62]. The WASH complex is thought to contribute to the segregation between these two functional opposing subdomains by: i) structuring the retrieval subdomain through interaction with multiple cargo-selective elements and, ii) assembling a meshwork of branched filamentous actin to restrict the lateral mobility of these components and associated cargoes [3] (Figure 2).…”