Retromer revisited: Evolving roles for retromer in endosomal sorting

The highly conserved retromer complex has been linked to cargo retrieval from endosomes to the trans-Golgi network. In this issue, Kvainickas et al. (2017. J. Cell Biol. https://doi.org/10.1083/jcb.201702137) and Simonetti et al. (2017. J. Cell Biol. https://doi.org/10.1083/jcb.201703015) fundamentally question the current retromer model and demonstrate that in mammalian cells, the individual retromer subcomplexes have functionally diverged to organize multiple distinct sorting pathways.

Download Full-text

Ride the wave: Retrograde trafficking becomes Ca2+ dependent with BAIAP3

The Journal of Cell Biology ◽

10.1083/jcb.201706007 ◽

2017 ◽

Vol 216 (7) ◽

pp. 1887-1889 ◽

Cited By ~ 3

Author(s):

Jakob B. Sørensen

Keyword(s):

Angiogenesis Inhibitor ◽

Secretory Vesicle ◽

Vesicle Formation ◽

Retrograde Trafficking ◽

Trans Golgi Network ◽

Cell Biol ◽

Golgi Network

The functions of four of the five proteins in the mammalian uncoordinated-13 (Munc13) family have been identified as priming factors in SNARE-dependent exocytosis. In this issue, Zhang et al. (2017. J. Cell Biol. https://doi.org/10.1083/jcb.201702099) show that the fifth member, BAIAP3 (brain-specific angiogenesis inhibitor I–associated protein 3), acts in retrograde trafficking by returning secretory vesicle material to the trans-Golgi network. In its absence, secretory vesicle formation is impaired, leading to accumulation of immature vesicles, or lysosomal vesicle degradation.

Download Full-text

Syntaxin 11 is associated with SNAP-23 on late endosomes and the trans-Golgi network

Journal of Cell Science ◽

10.1242/jcs.112.6.845 ◽

1999 ◽

Vol 112 (6) ◽

pp. 845-854 ◽

Cited By ~ 7

Author(s):

A.C. Valdez ◽

J.P. Cabaniols ◽

M.J. Brown ◽

P.A. Roche

Keyword(s):

Mammalian Cells ◽

Protein Transport ◽

Transmembrane Domain ◽

Family Members ◽

Snare Proteins ◽

Trans Golgi Network ◽

Late Endosomes ◽

Syntaxin 11 ◽

Golgi Network

SNARE proteins are known to play a role in regulating intracellular protein transport between donor and target membranes. This docking and fusion process involves the interaction of specific vesicle-SNAREs (e.g. VAMP) with specific cognate target-SNAREs (e.g. syntaxin and SNAP-23). Using human SNAP-23 as the bait in a yeast two-hybrid screen of a human B-lymphocyte cDNA library, we have identified the 287-amino-acid SNARE protein syntaxin 11. Like other syntaxin family members, syntaxin 11 binds to the SNARE proteins VAMP and SNAP-23 in vitro and also exists in a complex with SNAP-23 in transfected HeLa cells and in native human B lymphocytes. Unlike other syntaxin family members, no obvious transmembrane domain is present in syntaxin 11. Nevertheless, syntaxin 11 is predominantly membrane-associated and colocalizes with the mannose 6-phosphate receptor on late endosomes and the trans-Golgi network. These data suggest that syntaxin 11 is a SNARE that acts to regulate protein transport between late endosomes and the trans-Golgi network in mammalian cells.

Download Full-text

The Retromer Coat Complex Coordinates Endosomal Sorting and Dynein-Mediated Transport, with Carrier Recognition by the trans-Golgi Network

Developmental Cell ◽

10.1016/j.devcel.2009.04.016 ◽

2009 ◽

Vol 17 (1) ◽

pp. 110-122 ◽

Cited By ~ 166

Author(s):

Thomas Wassmer ◽

Naomi Attar ◽

Martin Harterink ◽

Jan R.T. van Weering ◽

Colin J. Traer ◽

...

Keyword(s):

Endosomal Sorting ◽

Trans Golgi Network ◽

Golgi Network

Download Full-text

A computational model of PKD and CERT interactions at the trans-Golgi network of mammalian cells

BMC Systems Biology ◽

10.1186/s12918-015-0147-1 ◽

2015 ◽

Vol 9 (1) ◽

Cited By ~ 14

Author(s):

Patrick Weber ◽

Mariana Hornjik ◽

Monilola A Olayioye ◽

Angelika Hausser ◽

Nicole E Radde

Keyword(s):

Computational Model ◽

Mammalian Cells ◽

Trans Golgi Network ◽

Golgi Network

Download Full-text

GGA proteins: new players in the sorting game

Journal of Cell Science ◽

10.1242/jcs.114.19.3413 ◽

2001 ◽

Vol 114 (19) ◽

pp. 3413-3418 ◽

Cited By ~ 1

Author(s):

Annette L. Boman

Keyword(s):

Membrane Trafficking ◽

Sequence Homology ◽

Mammalian Cells ◽

Gene Knockout ◽

Protein Domains ◽

Vesicle Formation ◽

Trans Golgi Network ◽

And Function ◽

Golgi Network ◽

Cargo Sorting

The GGA proteins are a novel family of proteins that were discovered nearly simultaneously by several labs studying very different aspects of membrane trafficking. Since then, several studies have described the GGA proteins and their functions in yeast and mammalian cells. Four protein domains are present in all GGA proteins, as defined by sequence homology and function. These different domains interact directly with ARF proteins, cargo and clathrin. Alteration of the levels of GGA proteins by gene knockout or overexpression affects specific trafficking events between the trans-Golgi network and endosomes. These data suggest that GGAs function as ARF-dependent, monomeric clathrin adaptors to facilitate cargo sorting and vesicle formation at the trans-Golgi network.

Download Full-text

The small GTP-binding protein rab6p is redistributed in the cytosol by brefeldin A

Journal of Cell Science ◽

10.1242/jcs.106.3.789 ◽

1993 ◽

Vol 106 (3) ◽

pp. 789-802 ◽

Cited By ~ 2

Author(s):

M. Roa ◽

V. Cornet ◽

C.Z. Yang ◽

B. Goud

Keyword(s):

Membrane Trafficking ◽

Mammalian Cells ◽

Brefeldin A ◽

Atp Depletion ◽

Cell Fractionation ◽

Microtubule Organizing Center ◽

Trans Golgi Network ◽

Gtp Binding ◽

Organizing Center ◽

Golgi Network

Rab6 protein belongs to the Sec4/Ypt/rab subfamily of small GTP-binding proteins involved in intracellular membrane trafficking in yeast and mammalian cells. Its localization both in medial and trans-Golgi network prompted us to study the effects of brefeldin A (BFA) on rab6p redistribution. By two techniques, indirect immunofluorescence and cell fractionation, we investigated the fate of rab6p and compared it to other Golgi or trans-Golgi network markers in BHK-21 and NIH-3T3 cells. BFA, at 5 micrograms/ml, induced redistribution of rab6p according to a biphasic process: during the first 10–15 minutes, tubulo-vesicular structures--colabelled with a bona fide medial Golgi marker called CTR 433--were observed; these structures were then replaced by punctate diffuse staining, which was stable for up to 3 hours. The 110 kDa peripheral membrane protein beta-COP was released much more rapidly from the Golgi membranes, whereas the trans-Golgi network marker TGN 38 relocated to the microtubule organizing center. The kinetics of reversion of BFA action on these antigens was also followed by immunofluorescence. Consistent with these results, rab6 antigen, originally found as 40% in the cytosolic versus 60% in the particulate (P 150,000 g) fraction, became almost entirely cytosolic; moreover, it partitioned in the aqueous phase of Triton X-114 whereas the membrane fraction was detergent-soluble. Rab6p did not become part of the coatomers after its BFA-induced release from Golgi structures. Three requirements seemed to be necessary for such a release: integrity of the microtubules, presence of energy, and a hypothetical trimeric G protein, as revealed by the respective roles of nocodazole, ATP depletion, and sensitivity to aluminium fluoride. Finally, we have shown that BFA does not prevent attachment of newly synthesized rab6p to membranes.

Download Full-text

Syntaxin 6 functions in trans-Golgi network vesicle trafficking.

Molecular Biology of the Cell ◽

10.1091/mbc.8.7.1261 ◽

1997 ◽

Vol 8 (7) ◽

pp. 1261-1271 ◽

Cited By ~ 205

Author(s):

J B Bock ◽

J Klumperman ◽

S Davanger ◽

R H Scheller

Keyword(s):

Mammalian Cells ◽

Vesicle Trafficking ◽

Adapter Protein ◽

Trans Golgi Network ◽

Golgi Region ◽

Coated Membranes ◽

Membrane Compartments ◽

Mammalian Homologue ◽

In Trans ◽

Golgi Network

The specific transfer of vesicles between organelles is critical in generating and maintaining the organization of membrane compartments within cells. Syntaxin 6 is a recently discovered member of the syntaxin family, whose constituents are required components of several vesicle trafficking pathways. To better understand the function of syntaxin 6, we generated a panel of monoclonal antibodies that specifically recognize different epitopes of the protein. Immunoelectron microscopy shows syntaxin 6 primarily on the trans-Golgi network (TGN), where is partially colocalizes with the TGN adapter protein AP-1 on clathrin-coated membranes. Additional label is present on small vesicles in the vicinity of endosome-like structures. Immunoprecipitation of syntaxin 6 revealed that it is present in a complex or complexes with alpha-soluble NSF attachment protein, vesicle-associated membrane protein 2, or cellubrevin and a mammalian homologue of VPS45, which is a member of the sec1 family implicated in Golgi to prevacuolar compartment trafficking in yeast. We show that mammalian VPS45 is found in multiple tissues, is partially membrane associated, and is enriched in the Golgi region. Converging lines of evidence suggest that syntaxin 6 mediates a TGN trafficking event, perhaps targeting to endosomes in mammalian cells.

Download Full-text

Retromer retrieves the Wilson disease protein ATP7B from endolysosomes in a copper-dependent manner

Journal of Cell Science ◽

10.1242/jcs.246819 ◽

2020 ◽

Vol 133 (24) ◽

pp. jcs246819 ◽

Cited By ~ 1

Author(s):

Santanu Das ◽

Saptarshi Maji ◽

Ruturaj ◽

Indira Bhattacharya ◽

Tanusree Saha ◽

...

Keyword(s):

Wilson Disease ◽

Dependent Manner ◽

Copper Transporter ◽

Copper Chelation ◽

Trans Golgi Network ◽

Wilson Disease Protein ◽

Retromer Complex ◽

High Copper ◽

Disease Protein ◽

Golgi Network

ABSTRACTThe Wilson disease protein, ATP7B maintains copper (herein referring to the Cu+ ion) homeostasis in the liver. ATP7B traffics from trans-Golgi network to endolysosomes to export excess copper. Regulation of ATP7B trafficking to and from endolysosomes is not well understood. We investigated the fate of ATP7B after copper export. At high copper levels, ATP7B traffics primarily to acidic, active hydrolase (cathepsin-B)-positive endolysosomes and, upon subsequent copper chelation, returns to the trans-Golgi network (TGN). At high copper, ATP7B colocalizes with endolysosomal markers and with a core member of retromer complex, VPS35. Knocking down VPS35 did not abrogate the copper export function of ATP7B or its copper-responsive anterograde trafficking to vesicles; rather upon subsequent copper chelation, ATP7B failed to relocalize to the TGN, which was rescued by overexpressing wild-type VPS35. Overexpressing mutants of the retromer complex-associated proteins Rab7A and COMMD1 yielded a similar non-recycling phenotype of ATP7B. At high copper, VPS35 and ATP7B are juxtaposed on the same endolysosome and form a large complex that is stabilized by in vivo photoamino acid labeling and UV-crosslinking. We demonstrate that retromer regulates endolysosome to TGN trafficking of copper transporter ATP7B in a manner that is dependent upon intracellular copper.

Download Full-text

Interchangeable but Essential Functions of SNX1 and SNX2 in the Association of Retromer with Endosomes and the Trafficking of Mannose 6-Phosphate Receptors

Molecular and Cellular Biology ◽

10.1128/mcb.00156-06 ◽

2006 ◽

Vol 27 (3) ◽

pp. 1112-1124 ◽

Cited By ~ 140

Author(s):

Raul Rojas ◽

Satoshi Kametaka ◽

Carol R. Haft ◽

Juan S. Bonifacino

Keyword(s):

Mammalian Cells ◽

Human Cell Line ◽

Sorting Nexin ◽

Retromer Complex ◽

Cell Line Hela ◽

Endosomal Membranes ◽

Mannose 6 Phosphate ◽

And Function ◽

Golgi Network ◽

Functional Analyses

ABSTRACT The retromer is a cytosolic/peripheral membrane protein complex that mediates the retrieval of the cation-independent mannose 6-phosphate receptor from endosomes to the trans-Golgi network (TGN) in mammalian cells. Previous studies showed that the mammalian retromer comprises three proteins, named Vps26, Vps29, and Vps35, plus the sorting nexin, SNX1. There is conflicting evidence, however, as to whether a homologous sorting nexin, SNX2, is truly a component of the retromer. In addition, the nature of the subunit interactions and assembly of the mammalian retromer complex are poorly understood. We have addressed these issues by performing biochemical and functional analyses of endogenous retromers in the human cell line HeLa. We found that the mammalian retromer complex consists of two autonomously assembling subcomplexes, namely, a Vps26-Vps29-Vps35 obligate heterotrimer and a SNX1/2 alternative heterodimer or homodimer. The association of Vps26-Vps29-Vps35 with endosomes requires the presence of either SNX1 or SNX2, whereas SNX1/2 can be recruited to endosomes independently of Vps26-Vps29-Vps35. We also found that the presence of either SNX1 or SNX2 is essential for the retrieval of the cation-independent mannose 6-phosphate receptor to the TGN. These observations indicate that the mammalian retromer complex assembles by sequential association of SNX1/2 and Vps26-Vps29-Vps35 subcomplexes on endosomal membranes and that SNX1 and SNX2 play interchangeable but essential roles in retromer structure and function.

Download Full-text