Vps26A and Vps26B Subunits Define Distinct Retromer Complexes

Abstract

The trimeric Vps29-Vps35-Vps26 sub-complex of retromer mediates retrograde transport of transmembrane proteins from endosomes to the trans-Golgi network. Our group has recently identified a Vps26 paralogue, Vps26B, which is able to suppress the expression of Vps26A when exogenously expressed in mammalian cells and defines a distinct retromer complex (Vps26B-retromer) in vivo and in vitro. In this study, we use HEK293 cells stably expressing either Vps26A-myc or Vps26B-myc to address the role of retromer cargo transport and subcellular localization of the two core retromer complexes as defined by the two mammalian-specific Vps26 paralogues. Vps26B-retromer, like Vps26A-retromer, associates with TBC1D5 and GOLPH3. In contrast, no interaction between Vps26B-retromer and cation-independent mannose 6-phosphate receptor (CI-M6PR) was detected, leading to a degradation of this receptor and an increase in cathepsin D secretion. Colocalization of Vps26 paralogues with different endosomally located Rab proteins shows prolonged association of Vps26B-retromer with maturing endosomes relative to Vps26A-retromer. Interestingly, the cycling of CI-M6PR is restored upon deletion of the variable Vps26B C-terminal region indicating that this region is directly responsible for the differential function of the two paralogues. In summary, we show that the two distinct retromer complexes defined by different Vps26 paralogues are not functionally equivalent and that the Vps26B C-terminal region can control cargo selection of the Vps26B-retromer.

A unique PDZ domain and arrestin-like fold interaction reveals mechanistic details of endocytic recycling by SNX27-retromer

“…In contrast, suppression of the unique core retromer subunit VPS35 resulted in a similar degree of GLUT1 rerouting to late endosomes/lysosomes as SNX27 suppression. These observations suggest redundancy between VPS26A and VPS26B proteins in endosome-to-plasma membrane recycling, in contrast to the previous finding that VPS26A-retromer can mediate endosome-to-Golgi trafficking of the mannose-6-phosphate receptor, but VPS26B retromer cannot (28). Confirming this redundancy, when both VPS26A and VPS26B…”

The retromer complex – endosomal protein recycling and beyond

“…Both forms comprise arrestin-like folds suggesting that both might be able to recognise cargo proteins. Recent evidence has shown that the endosome-to-Golgi retrieval of CIMPR requires Vps26a but not Vps26b, revealing that they exert a preference for different cargoes (Bugarcic et al, 2011). Additionally, Vps26a and Vps26b might operate at distinct points in the endocytic pathway, although confirmation of this finding will require simultaneous determination of the localisation of both proteins at their endogenous expression levels.…”

Parkinson Disease-linked Vps35 R524W Mutation Impairs the Endosomal Association of Retromer and Induces α-Synuclein Aggregation

“…Previous reports mapped the interaction between retromer and the cytosolic tail of the CI-M6PR to amino acids 500 -693 of the Vps35 subunit (11). Given the location of the point mutations on the Vps35 in relation to the Vps29 and the cargo-interacting domain within Vps35, the interaction of retromer with CI-M6PR, modulation of soluble lysosomal enzyme delivery, relative co-localization, and kinetics of retrograde trafficking were analyzed as described previously (10,11,17). Vps35 P316S-containing retromer was found to co-precipitate the M6PR at levels identical to that of the wild-type retromer, whereas Vps35 R524W displayed decreased levels of M6PR (ranging from 15 to 60% less precipitant than Vps35 WT levels) (Fig.…”

“…HeLa cells were co-transfected with CD8-CI-M6PR to monitor the retrograde delivery of internalized antibodies to the TGN using a well established antibody uptake assay (10). Cells were incubated on ice with anti-CD8 antibody and chased at 37°C for up to 30 min.…”