title: 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.
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia.
authors.forename: Andrea
authors.initials: A
authors.lastname: Bugarcic
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhe
authors.forename: Markus C
authors.initials: MC
authors.lastname: Kerr
authors.forename: John
authors.initials: J
authors.lastname: Griffin
authors.forename: Brett M
authors.initials: BM
authors.lastname: Collins
authors.forename: Rohan D
authors.initials: RD
authors.lastname: Teasdale
mesh_terms: D002402:Cathepsin D / Q000378:metabolism; D011992:Endosomes / Q000235:genetics / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D011485:Protein Binding; D021122:Protein Subunits; D021381:Protein Transport; D017527:Receptor, IGF Type 2; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000378:metabolism; D021601:trans-Golgi Network / Q000235:genetics / Q000378:metabolism*
chemical_list: C429024:GOLPH3 protein, human; D020690:GTPase-Activating Proteins; D008565:Membrane Proteins; D021122:Protein Subunits; D017527:Receptor, IGF Type 2; D018160:Receptors, Cytoplasmic and Nuclear; C543487:TBC1D5 protein, human; C498296:VPS26A protein, human; D033921:Vesicular Transport Proteins; C034304:cation-dependent mannose-6-phosphate receptor; C533922:CTSD protein, human; D002402:Cathepsin D; D020691:rab GTP-Binding Proteins