scholarly journals Vesicular and uncoated Rab1-dependent cargo carriers facilitate ER to Golgi transport

2020 ◽  
Vol 133 (14) ◽  
pp. jcs239814 ◽  
Author(s):  
Laura M. Westrate ◽  
Melissa J. Hoyer ◽  
Michael J. Nash ◽  
Gia K. Voeltz
Keyword(s):  
Endoplasmic Reticulum ◽  
De Novo ◽  
Coated Vesicle ◽  
First Person ◽  
Coat Proteins ◽  
Animal Cells ◽  
Golgi Transport ◽  
Er Exit Sites ◽  
Copii Vesicles ◽  
Export System

ABSTRACTSecretory cargo is recognized, concentrated and trafficked from endoplasmic reticulum (ER) exit sites (ERES) to the Golgi. Cargo export from the ER begins when a series of highly conserved COPII coat proteins accumulate at the ER and regulate the formation of cargo-loaded COPII vesicles. In animal cells, capturing live de novo cargo trafficking past this point is challenging; it has been difficult to discriminate whether cargo is trafficked to the Golgi in a COPII-coated vesicle. Here, we describe a recently developed live-cell cargo export system that can be synchronously released from ERES to illustrate de novo trafficking in animal cells. We found that components of the COPII coat remain associated with the ERES while cargo is extruded into COPII-uncoated, non-ER associated, Rab1 (herein referring to Rab1a or Rab1b)-dependent carriers. Our data suggest that, in animal cells, COPII coat components remain stably associated with the ER at exit sites to generate a specialized compartment, but once cargo is sorted and organized, Rab1 labels these export carriers and facilitates efficient forward trafficking.This article has an associated First Person interview with the first author of the paper.

scholarly journals Disruption of endoplasmic reticulum to Golgi transport leads to the accumulation of large aggregates containing beta-COP in pancreatic acinar cells.

1993 ◽  
Vol 4 (4) ◽  
pp. 413-424 ◽  
Author(s):  
L C Hendricks ◽  
M McCaffery ◽  
G E Palade ◽  
M G Farquhar
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Complex ◽  
Brefeldin A ◽  
Acinar Cells ◽  
Atp Depletion ◽  
Pancreatic Acinar Cells ◽  
Coat Proteins ◽  
Golgi Membranes ◽  
Golgi Transport ◽  
Transport Vesicles

When transport between the rough endoplasmic reticulum (ER) and Golgi complex is blocked by Brefeldin A (BFA) treatment or ATP depletion, the Golgi apparatus and associated transport vesicles undergo a dramatic reorganization. Because recent studies suggest that coat proteins such as beta-COP play an important role in the maintenance of the Golgi complex, we have used immunocytochemistry to determine the distribution of beta-COP in pancreatic acinar cells (PAC) in which ER to Golgi transport was blocked by BFA treatment or ATP depletion. In controls, beta-COP was associated with Golgi cisternae and transport vesicles as expected. Upon BFA treatment, PAC Golgi cisternae are dismantled and replaced by clusters of remnant vesicles surrounded by typical ER transitional elements that are generally assumed to represent the exit site of vesicular carriers for ER to Golgi transport. In BFA-treated PAC, beta-COP was concentrated in large (0.5-1.0 micron) aggregates closely associated with remnant Golgi membranes. In addition to typical ER transitional elements, we detected a new type of transitional element that consists of specialized regions of rough ER (RER) with ribosome-free ends that touched or extended into the beta-COP containing aggregates. In ATP-depleted PAC, beta-COP was not detected on Golgi membranes but was concentrated in similar large aggregates found on the cis side of the Golgi stacks. The data indicate that upon arrest of ER to Golgi transport by either BFA treatment or energy depletion, beta-COP dissociates from PAC Golgi membranes and accumulates as large aggregates closely associated with specialized ER elements. The latter may correspond to either the site of entry or exit for vesicles recycling between the Golgi and the RER.

scholarly journals ER exit sites are physical and functional core autophagosome biogenesis components

2013 ◽  
Vol 24 (18) ◽  
pp. 2918-2931 ◽  
Author(s):  
Martin Graef ◽  
Jonathan R. Friedman ◽  
Christopher Graham ◽  
Mohan Babu ◽  
Jodi Nunnari
Keyword(s):  
Endoplasmic Reticulum ◽  
Stress Response ◽  
De Novo ◽  
Double Membrane ◽  
Hierarchical Assembly ◽  
Transport Vesicles ◽  
Stress Response Pathway ◽  
Er Exit Sites ◽  
Functional Analyses

Autophagy is a central homeostasis and stress response pathway conserved in all eukaryotes. One hallmark of autophagy is the de novo formation of autophagosomes. These double-membrane vesicular structures form around and deliver cargo for degradation by the vacuole/lysosome. Where and how autophagosomes form are outstanding questions. Here we show, using proteomic, cytological, and functional analyses, that autophagosomes are spatially, physically, and functionally linked to endoplasmic reticulum exit sites (ERES), which are specialized regions of the endoplasmic reticulum where COPII transport vesicles are generated. Our data demonstrate that ERES are core autophagosomal biogenesis components whose function is required for the hierarchical assembly of the autophagy machinery immediately downstream of the Atg1 kinase complex at phagophore assembly sites.

scholarly journals TANGO1/cTAGE5 receptor as a polyvalent template for assembly of large COPII coats

2016 ◽  
Vol 113 (36) ◽  
pp. 10061-10066 ◽  
Author(s):  
Wenfu Ma ◽  
Jonathan Goldberg
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Coat Protein ◽  
Biochemical Analysis ◽  
Coat Proteins ◽  
Outer Coat ◽  
Receptor Molecule ◽  
X Ray ◽  
Er Exit Sites ◽  
Multiple Copies

The supramolecular cargo procollagen is loaded into coat protein complex II (COPII)-coated carriers at endoplasmic reticulum (ER) exit sites by the receptor molecule TANGO1/cTAGE5. Electron microscopy studies have identified a tubular carrier of suitable dimensions that is molded by a distinctive helical array of the COPII inner coat protein Sec23/24•Sar1; the helical arrangement is absent from canonical COPII-coated small vesicles. In this study, we combined X-ray crystallographic and biochemical analysis to characterize the association of TANGO1/cTAGE5 with COPII proteins. The affinity for Sec23 is concentrated in the proline-rich domains (PRDs) of TANGO1 and cTAGE5, but Sec23 recognizes merely a PPP motif. The PRDs contain repeated PPP motifs separated by proline-rich linkers, so a single TANGO1/cTAGE5 receptor can bind multiple copies of coat protein in a close-packed array. We propose that TANGO1/cTAGE5 promotes the accretion of inner coat proteins to the helical lattice. Furthermore, we show that PPP motifs in the outer coat protein Sec31 also bind to Sec23, suggesting that stepwise COPII coat assembly will ultimately displace TANGO1/cTAGE5 and compartmentalize its operation to the base of the growing COPII tubule.

scholarly journals LTK is an ER-resident receptor tyrosine kinase that regulates secretion

2019 ◽  
Author(s):  
Federica G. Centonze ◽  
Veronika Reiterer ◽  
Karsten Nalbach ◽  
Kota Saito ◽  
Krzysztof Pawlowski ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Tyrosine Kinase ◽  
Signaling Pathways ◽  
Receptor Tyrosine Kinase ◽  
Secretory Proteins ◽  
Golgi Transport ◽  
Er Exit Sites ◽  
Local Signaling ◽  
Er Export ◽  
Pharmacologic Inhibition

AbstractThe endoplasmic reticulum (ER) is a key regulator of cellular proteostasis because it controls folding, sorting and degradation of secretory proteins. Much has been learned about how environmentally triggered signaling pathways regulate ER function, but only little is known about local signaling at the ER. The identification of ER-resident signaling molecules will help gain a deeper understanding of the regulation of ER function and thus of proteostasis. Here, we show that leukocyte tyrosine kinase (LTK) is an ER-resident receptor tyrosine kinase. Depletion of LTK as well as its pharmacologic inhibition reduces the number of ER exit sites and slows ER-to-Golgi transport. Furthermore, we show that LTK interacts with and phosphorylates Sec12. Expression of a phosphoablating mutant of Sec12 reduces the efficiency of ER export. Thus, LTK-to-Sec12 signaling represents the first example of an ER-resident signaling module the potential to regulate proteostasis.

scholarly journals Uncoating of COPII from ER exit site membranes precedes cargo accumulation and membrane fission

2019 ◽  
Author(s):  
Olga Shomron ◽  
Inbar Nevo-Yassaf ◽  
Tamar Aviad ◽  
Yakey Yaffe ◽  
Eitan Erez Zahavi ◽  
...  
Keyword(s):  
Secretory Pathway ◽  
Membrane Vesicles ◽  
Coat Proteins ◽  
Direct Transfer ◽  
Exit Site ◽  
Membrane Fission ◽  
Golgi Transport ◽  
Er Exit Sites ◽  
Genetic Perturbations

SummaryCOPII and COPI are considered to be analogous sets of vesicle coat protein heterocomplexes. Coupled to cargo selection, they mediate the formation of membrane vesicles translocating in opposite directions to differ rent destinations within the secretory pathway. Here, live cell and electron microscopy provided evidence for a different localization and mode of function of the COPII coat during protein export from the endoplasmic reticulum (ER). Pharmaceutical and genetic perturbations of ER-Golgi transport were used to demonstrate that COPII is recruited to membranes defining the boundary of ER-ER Exit Sites (ERES) where it facilitates selective cargo concentration. Uncoating of COPII membranes precedes cargo accumulation and fission of Golgi-bound carriers. Moreover, we report what may be direct transfer of cargo to the Golgi apparatus from Golgi-associated BFA sensitive ERESs. Finally, in ldlF cells the stably expressed functional ε-COPI-EYFP labeled both ERESs and anterograde carriers. These findings change our understanding of the role of coat proteins in ER to Golgi transport.

scholarly journals TANGO1 and SEC12 are co-packaged with procollagen I to facilitate the generation of large COPII carriers

2018 ◽  
Author(s):  
Lin Yuan ◽  
Samuel J Kenny ◽  
Juliet Hemmati ◽  
Ke Xu ◽  
Randy Schekman
Keyword(s):  
Endoplasmic Reticulum ◽  
Coated Vesicles ◽  
Initiation Factor ◽  
Interacting Protein ◽  
Transport Vesicles ◽  
Er Exit Sites ◽  
Copii Vesicles ◽  
Er Membrane

AbstractLarge COPII-coated vesicles serve to convey the large cargo procollagen I (PC1) from the endoplasmic reticulum (ER). The link between large cargo in the lumen of the ER and modulation of the COPII machinery remains unresolved. TANGO1 is required for procollagen (PC) secretion and interacts with PC and COPII on opposite sides of the ER membrane, but evidence suggests that TANGO1 is retained in the ER, and not included in normal size (<100nm) COPII vesicles. Here we show that TANGO1 is exported out of the ER in large COPII-coated PC1 carriers, and retrieved back to the ER by the retrograde coat, COPI, mediated by the C-terminal RDEL retrieval sequence of HSP47. TANGO1 is known to target the COPII initiation factor SEC12 to ER exit sites through an interacting protein, cTAGE5. SEC12 is important for the growth of COPII vesicles, but it is not sorted into small budded vesicles. We found both cTAGE5 and SEC12 were exported with TANGO1 in large COPII carriers. In contrast to its exclusion from small transport vesicles, SEC12 was particularly enriched around ER membranes and large COPII carriers that contained PC1. We constructed a split GFP system to recapitulate the targeting of SEC12 to PC1 via the luminal domain of TANGO1. The minimal targeting system enriched SEC12 around PC1 and generated large PC1 carriers. We conclude that TANGO1, cTAGE5, and SEC12 are co-packed with PC1 into COPII carriers to increase the size of COPII thus ensuring the capture of large cargo.

scholarly journals COPII collar defines the boundary between ER and ER exit site and does not coat cargo containers

2021 ◽  
Vol 220 (6) ◽  
Author(s):  
Olga Shomron ◽  
Inbar Nevo-Yassaf ◽  
Tamar Aviad ◽  
Yakey Yaffe ◽  
Eitan Erez Zahavi ◽  
...  
Keyword(s):  
Secretory Pathway ◽  
Membrane Vesicles ◽  
Living Cells ◽  
Protein Export ◽  
Coat Proteins ◽  
Exit Site ◽  
Golgi Transport ◽  
Selection Processes ◽  
Er Exit Sites ◽  
Genetic Perturbations

COPII and COPI mediate the formation of membrane vesicles translocating in opposite directions within the secretory pathway. Live-cell and electron microscopy revealed a novel mode of function for COPII during cargo export from the ER. COPII is recruited to membranes defining the boundary between the ER and ER exit sites, facilitating selective cargo concentration. Using direct observation of living cells, we monitored cargo selection processes, accumulation, and fission of COPII-free ERES membranes. CRISPR/Cas12a tagging, the RUSH system, and pharmaceutical and genetic perturbations of ER-Golgi transport demonstrated that the COPII coat remains bound to the ER–ERES boundary during protein export. Manipulation of the cargo-binding domain in COPII Sec24B prohibits cargo accumulation in ERES. These findings suggest a role for COPII in selecting and concentrating exported cargo rather than coating Golgi-bound carriers. These findings transform our understanding of coat proteins’ role in ER-to-Golgi transport.

scholarly journals Sorting of GPI-anchored proteins into ER exit sites by p24 proteins is dependent on remodeled GPI

2011 ◽  
Vol 194 (1) ◽  
pp. 61-75 ◽  
Author(s):  
Morihisa Fujita ◽  
Reika Watanabe ◽  
Nina Jaensch ◽  
Maria Romanova-Michaelides ◽  
Tadashi Satoh ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Coat Protein ◽  
Posttranslational Modification ◽  
Protein Complex ◽  
Er Exit Sites ◽  
Ph Dependent ◽  
Copii Vesicles ◽  
Attachment Proteins ◽  
Acidic Compartments ◽  
P24 Proteins

Glycosylphosphatidylinositol (GPI) anchoring of proteins is a posttranslational modification occurring in the endoplasmic reticulum (ER). After GPI attachment, proteins are transported by coat protein complex II (COPII)-coated vesicles from the ER. Because GPI-anchored proteins (GPI-APs) are localized in the lumen, they cannot interact with cytosolic COPII components directly. Receptors that link GPI-APs to COPII are thought to be involved in efficient packaging of GPI-APs into vesicles; however, mechanisms of GPI-AP sorting are not well understood. Here we describe two remodeling reactions for GPI anchors, mediated by PGAP1 and PGAP5, which were required for sorting of GPI-APs to ER exit sites. The p24 family of proteins recognized the remodeled GPI-APs and sorted them into COPII vesicles. Association of p24 proteins with GPI-APs was pH dependent, which suggests that they bind in the ER and dissociate in post-ER acidic compartments. Our results indicate that p24 complexes act as cargo receptors for correctly remodeled GPI-APs to be sorted into COPII vesicles.

scholarly journals TANGO1 and SEC12 are copackaged with procollagen I to facilitate the generation of large COPII carriers

2018 ◽  
Vol 115 (52) ◽  
pp. E12255-E12264 ◽  
Author(s):  
Lin Yuan ◽  
Samuel J. Kenny ◽  
Juliet Hemmati ◽  
Ke Xu ◽  
Randy Schekman
Keyword(s):  
Endoplasmic Reticulum ◽  
Coat Protein ◽  
Protein Complex ◽  
Coated Vesicles ◽  
Initiation Factor ◽  
Interacting Protein ◽  
Complex Ii ◽  
Transport Vesicles ◽  
Er Exit Sites ◽  
Copii Vesicles

Large coat protein complex II (COPII)-coated vesicles serve to convey the large cargo procollagen I (PC1) from the endoplasmic reticulum (ER). The link between large cargo in the lumen of the ER and modulation of the COPII machinery remains unresolved. TANGO1 is required for PC secretion and interacts with PC and COPII on opposite sides of the ER membrane, but evidence suggests that TANGO1 is retained in the ER, and not included in normal size (<100 nm) COPII vesicles. Here we show that TANGO1 is exported out of the ER in large COPII-coated PC1 carriers, and retrieved back to the ER by the retrograde coat, COPI, mediated by the C-terminal RDEL retrieval sequence of HSP47. TANGO1 is known to target the COPII initiation factor SEC12 to ER exit sites through an interacting protein, cTAGE5. SEC12 is important for the growth of COPII vesicles, but it is not sorted into small budded vesicles. We found both cTAGE5 and SEC12 were exported with TANGO1 in large COPII carriers. In contrast to its exclusion from small transport vesicles, SEC12 was particularly enriched around ER membranes and large COPII carriers that contained PC1. We constructed a split GFP system to recapitulate the targeting of SEC12 to PC1 via the luminal domain of TANGO1. The minimal targeting system enriched SEC12 around PC1 and generated large PC1 carriers. We conclude that TANGO1, cTAGE5, and SEC12 are copacked with PC1 into COPII carriers to increase the size of COPII, thus ensuring the capture of large cargo.

scholarly journals LTK is an ER-resident receptor tyrosine kinase that regulates secretion

2019 ◽  
Vol 218 (8) ◽  
pp. 2470-2480 ◽  
Author(s):  
Federica G. Centonze ◽  
Veronika Reiterer ◽  
Karsten Nalbach ◽  
Kota Saito ◽  
Krzysztof Pawlowski ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Tyrosine Kinase ◽  
Signaling Pathways ◽  
Receptor Tyrosine Kinase ◽  
Secretory Proteins ◽  
Golgi Transport ◽  
Er Exit Sites ◽  
Local Signaling ◽  
Er Export ◽  
Pharmacologic Inhibition

The endoplasmic reticulum (ER) is a key regulator of cellular proteostasis because it controls folding, sorting, and degradation of secretory proteins. Much has been learned about how environmentally triggered signaling pathways regulate ER function, but only little is known about local signaling at the ER. The identification of ER-resident signaling molecules will help gain a deeper understanding of the regulation of ER function and thus of proteostasis. Here, we show that leukocyte tyrosine kinase (LTK) is an ER-resident receptor tyrosine kinase. Depletion of LTK as well as its pharmacologic inhibition reduces the number of ER exit sites and slows ER-to-Golgi transport. Furthermore, we show that LTK interacts with and phosphorylates Sec12. Expression of a phosphoablating mutant of Sec12 reduces the efficiency of ER export. Thus, LTK-to-Sec12 signaling represents the first example of an ER-resident signaling module with the potential to regulate proteostasis.

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