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Updated: Mar 8, 2026

The Microscopy-Based Assay to Study and Analyze the Recycling Endosomes using SNARE Trafficking
Published on: February 12, 2022
Retromer-driven membrane tubulation separates endosomal recycling from Rab7/Ypt7-dependent fusion
Latha Kallur Purushothaman1, Henning Arlt2, Anne Kuhlee3
1Department of Biology/Chemistry, Biochemistry Section, University of Osnabrück, 49076 Osnabrück, Germany.
Abstract:
Endosomes are the major protein-sorting hubs of the endocytic pathway. They sort proteins destined for degradation into internal vesicles while in parallel recycling receptors via tubular carriers back to the Golgi. Tubule formation depends on the Rab7/Ypt7-interacting retromer complex, consisting of the sorting nexin dimer (SNX-BAR) and the trimeric cargo selection complex (CSC). Fusion of mature endosomes with the lysosome-like vacuole also requires Rab7/Ypt7. Here we solve a major problem in understanding this dual function of endosomal Rab7/Ypt7, using a fully reconstituted system, including purified, full-length yeast SNX-BAR and CSC, whose overall structure we present. We reveal that the membrane-active SNX-BAR complex displaces Ypt7 from cargo-bound CSC during formation of recycling tubules. This explains how a single Rab can coordinate recycling and fusion on endosomes.
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