GGA proteins: new players in the sorting game

2001 ◽  
Vol 114 (19) ◽  
pp. 3413-3418 ◽  
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.

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

1993 ◽  
Vol 106 (3) ◽  
pp. 789-802 ◽  
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.

scholarly journals Arf1 orchestrates Rab GTPase conversion at the trans-Golgi network

2021 ◽  
pp. mbc.E20-10-0664
Author(s):  
Laura L. Thomas ◽  
Carolyn M. Highland ◽  
J. Christopher Fromme
Keyword(s):  
Membrane Trafficking ◽  
Rab Gtpase ◽  
Rab Gtpases ◽  
Membrane Domains ◽  
Trans Golgi Network ◽  
Important Regulator ◽  
And Function ◽  
Golgi Network ◽  
New Evidence

Rab family GTPases are key organizers of membrane trafficking and function as markers of organelle identity. Accordingly, Rab GTPases often occupy specific membrane domains and mechanisms exist to prevent the inappropriate mixing of distinct Rab domains. The yeast Golgi complex can be divided into two broad Rab domains: Ypt1 (Rab1) and Ypt6 (Rab6) are present at the early/medial Golgi and sharply transition to Ypt31/32 (Rab11) at the late Golgi/ trans-Golgi network (TGN). This Rab conversion has been attributed to GAP cascades in which Ypt31/32 recruits the Rab-GAPs Gyp1 and Gyp6 to inactivate Ypt1 and Ypt6, respectively. Here we report that Rab transition at the TGN involves additional layers of regulation. We provide new evidence confirming the TRAPPII complex as an important regulator of Ypt6 inactivation and uncover an unexpected role of the Arf1 GTPase in recruiting Gyp1 to drive Ypt1 inactivation at the TGN. Given its established role in directly recruiting TRAPPII to the TGN, Arf1 is therefore a master regulator of Rab conversion on maturing Golgi compartments.

scholarly journals Formation of secretory vesicles in permeabilized cells: a salt extract from yeast membranes promotes budding of nascent secretory vesicles from the trans-Golgi network of endocrine cells

1996 ◽  
Vol 314 (3) ◽  
pp. 723-726 ◽  
Author(s):  
Wai Lam W. LING ◽  
Dennis SHIELDS
Keyword(s):  
Mammalian Cells ◽  
Endocrine Cells ◽  
Secretory Vesicle ◽  
Gh3 Cells ◽  
Vesicle Formation ◽  
Secretory Vesicles ◽  
Vesicle Budding ◽  
Trans Golgi Network ◽  
Golgi Network ◽  
Salt Extract

The mechanism of secretory-vesicle formation from the trans-Golgi network (TGN) of endocrine cells is poorly understood. To identify cytosolic activities that facilitate the formation and fission of nascent secretory vesicles, we treated permeabilized pituitary GH3 cells with high salt to remove endogenous budding factors. Using this cell preparation, secretory-vesicle budding from the TGN required addition of exogenous cytosol and energy. Mammalian cytosols (GH3 cells and bovine brain) promoted post-TGN vesicle formation. Most significantly, a salt extract of membranes from the yeast Saccharomyces cerevisiae, a cell lacking a regulated secretory pathway, stimulated secretory vesicle budding in the absence of mammalian cytosolic factors. These results demonstrate that the factors which promote secretory-vesicle release from the TGN are conserved between yeast and mammalian cells.

scholarly journals The secretion inhibitor Exo2 perturbs trafficking of Shiga toxin between endosomes and the trans-Golgi network

2008 ◽  
Vol 414 (3) ◽  
pp. 471-484 ◽  
Author(s):  
Robert A. Spooner ◽  
Peter Watson ◽  
Daniel C. Smith ◽  
Frédéric Boal ◽  
Mohammed Amessou ◽  
...  
Keyword(s):  
Cholera Toxin ◽  
Membrane Trafficking ◽  
Shiga Toxin ◽  
Mammalian Cells ◽  
Brefeldin A ◽  
Anterograde Transport ◽  
Trans Golgi Network ◽  
Molecule Inhibitor ◽  
Early Endosomes ◽  
Golgi Network

The small-molecule inhibitor Exo2 {4-hydroxy-3-methoxy-(5,6,7,8-tetrahydrol[1]benzothieno[2,3-d]pyrimidin-4-yl)hydraz-one benzaldehyde} has been reported to disrupt the Golgi apparatus completely and to stimulate Golgi–ER (endoplasmic reticulum) fusion in mammalian cells, akin to the well-characterized fungal toxin BFA (brefeldin A). It has also been reported that Exo2 does not affect the integrity of the TGN (trans-Golgi network), or the direct retrograde trafficking of the glycolipid-binding cholera toxin from the TGN to the ER lumen. We have examined the effects of BFA and Exo2, and found that both compounds are indistinguishable in their inhibition of anterograde transport and that both reagents significantly disrupt the morphology of the TGN in HeLa and in BS-C-1 cells. However, Exo2, unlike BFA, does not induce tubulation and merging of the TGN and endosomal compartments. Furthermore, and in contrast with its effects on cholera toxin, Exo2 significantly perturbs the delivery of Shiga toxin to the ER. Together, these results suggest that the likely target(s) of Exo2 operate at the level of the TGN, the Golgi and a subset of early endosomes, and thus Exo2 provides a more selective tool than BFA for examining membrane trafficking in mammalian cells.

scholarly journals Cargo sorting zones in the trans-Golgi network visualized by super-resolution confocal live imaging microscopy in plants

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yutaro Shimizu ◽  
Junpei Takagi ◽  
Emi Ito ◽  
Yoko Ito ◽  
Kazuo Ebine ◽  
...  
Keyword(s):  
Membrane Trafficking ◽  
High Speed ◽  
Super Resolution ◽  
Adaptor Protein ◽  
Transport Proteins ◽  
3D Localization ◽  
Golgi Network ◽  
Distinct Distribution ◽  
Vacuolar Trafficking ◽  
Cargo Sorting

AbstractThe trans-Golgi network (TGN) has been known as a key platform to sort and transport proteins to their final destinations in post-Golgi membrane trafficking. However, how the TGN sorts proteins with different destinies still remains elusive. Here, we examined 3D localization and 4D dynamics of TGN-localized proteins of Arabidopsis thaliana that are involved in either secretory or vacuolar trafficking from the TGN, by a multicolor high-speed and high-resolution spinning-disk confocal microscopy approach that we developed. We demonstrate that TGN-localized proteins exhibit spatially and temporally distinct distribution. VAMP721 (R-SNARE), AP (adaptor protein complex)−1, and clathrin which are involved in secretory trafficking compose an exclusive subregion, whereas VAMP727 (R-SNARE) and AP-4 involved in vacuolar trafficking compose another subregion on the same TGN. Based on these findings, we propose that the single TGN has at least two subregions, or “zones”, responsible for distinct cargo sorting: the secretory-trafficking zone and the vacuolar-trafficking zone.

scholarly journals ADP-Ribosylation Factor (ARF) Interaction Is Not Sufficient for Yeast GGA Protein Function or Localization

2002 ◽  
Vol 13 (9) ◽  
pp. 3078-3095 ◽  
Author(s):  
Annette L. Boman ◽  
Paul D. Salo ◽  
Melissa J. Hauglund ◽  
Nicole L. Strand ◽  
Shelly J. Rensink ◽  
...  
Keyword(s):  
Membrane Trafficking ◽  
Mammalian Cells ◽  
Fluorescent Protein ◽  
Protein Localization ◽  
Carboxypeptidase Y ◽  
Minor Role ◽  
Temperature Sensitive ◽  
Adp Ribosylation ◽  
And Function ◽  
Adp Ribosylation Factor

Golgi-localized γ-ear homology domain, ADP-ribosylation factor (ARF)-binding proteins (GGAs) facilitate distinct steps of post-Golgi traffic. Human and yeast GGA proteins are only ∼25% identical, but all GGA proteins have four similar domains based on function and sequence homology. GGA proteins are most conserved in the region that interacts with ARF proteins. To analyze the role of ARF in GGA protein localization and function, we performed mutational analyses of both human and yeast GGAs. To our surprise, yeast and human GGAs differ in their requirement for ARF interaction. We describe a point mutation in both yeast and mammalian GGA proteins that eliminates binding to ARFs. In mammalian cells, this mutation disrupts the localization of human GGA proteins. Yeast Gga function was studied using an assay for carboxypeptidase Y missorting and synthetic temperature-sensitive lethality between GGAs andVPS27. Based on these assays, we conclude that non-Arf-binding yeast Gga mutants can function normally in membrane trafficking. Using green fluorescent protein-tagged Gga1p, we show that Arf interaction is not required for Gga localization to the Golgi. Truncation analysis of Gga1p and Gga2p suggests that the N-terminal VHS domain and C-terminal hinge and ear domains play significant roles in yeast Gga protein localization and function. Together, our data suggest that yeast Gga proteins function to assemble a protein complex at the late Golgi to initiate proper sorting and transport of specific cargo. Whereas mammalian GGAs must interact with ARF to localize to and function at the Golgi, interaction between yeast Ggas and Arf plays a minor role in Gga localization and function.

scholarly journals HID-1 controls formation of large dense core vesicles by influencing cargo sorting and trans-Golgi network acidification

2017 ◽  
Vol 28 (26) ◽  
pp. 3870-3880 ◽  
Author(s):  
Blake H. Hummer ◽  
Noah F. de Leeuw ◽  
Christian Burns ◽  
Lan Chen ◽  
Matthew S. Joens ◽  
...  
Keyword(s):  
Biochemical Properties ◽  
Neuroendocrine Cells ◽  
Dense Core ◽  
Core Formation ◽  
Dense Core Vesicles ◽  
Atpase Subunit ◽  
Trans Golgi Network ◽  
Large Dense Core Vesicles ◽  
Golgi Network ◽  
Cargo Sorting

Large dense core vesicles (LDCVs) mediate the regulated release of neuropeptides and peptide hormones. They form at the trans-Golgi network (TGN), where their soluble content aggregates to form a dense core, but the mechanisms controlling biogenesis are still not completely understood. Recent studies have implicated the peripheral membrane protein HID-1 in neuropeptide sorting and insulin secretion. Using CRISPR/Cas9, we generated HID-1 KO rat neuroendocrine cells, and we show that the absence of HID-1 results in specific defects in peptide hormone and monoamine storage and regulated secretion. Loss of HID-1 causes a reduction in the number of LDCVs and affects their morphology and biochemical properties, due to impaired cargo sorting and dense core formation. HID-1 KO cells also exhibit defects in TGN acidification together with mislocalization of the Golgi-enriched vacuolar H+-ATPase subunit isoform a2. We propose that HID-1 influences early steps in LDCV formation by controlling dense core formation at the TGN.

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

2017 ◽  
Vol 216 (7) ◽  
pp. 1887-1889 ◽  
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.

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