scholarly journals p125A exists as part of the mammalian Sec13/Sec31 COPII subcomplex to facilitate ER-Golgi transport

2010 ◽  
Vol 190 (3) ◽  
pp. 331-345 ◽  
Author(s):  
Yan Shan Ong ◽  
Bor Luen Tang ◽  
Li Shen Loo ◽  
Wanjin Hong
Keyword(s):  
Endoplasmic Reticulum ◽  
Coat Protein ◽  
Mammalian Cells ◽  
Ternary Complex ◽  
Gel Filtration ◽  
Terminal Region ◽  
Protein Export ◽  
Interacting Protein ◽  
Golgi Transport ◽  
Er Export

Coat protein II (COPII)–mediated export from the endoplasmic reticulum (ER) involves sequential recruitment of COPII complex components, including the Sar1 GTPase, the Sec23/Sec24 subcomplex, and the Sec13/Sec31 subcomplex. p125A was originally identified as a Sec23A-interacting protein. Here we demonstrate that p125A also interacts with the C-terminal region of Sec31A. The Sec31A-interacting domain of p125A is between residues 260–600, and is therefore a distinct domain from that required for interaction with Sec23A. Gel filtration and immunodepletion studies suggest that the majority of cytosolic p125A exists as a ternary complex with the Sec13/Sec31A subcomplex, suggesting that Sec 13, Sec31A, and p125A exist in the cytosol primarily as preassembled Sec13/Sec31A/p125A heterohexamers. Golgi morphology and protein export from the ER were affected in p125A-silenced cells. Our results suggest that p125A is part of the Sec13/Sec31A subcomplex and facilitates ER export in mammalian cells.

scholarly journals Nm23H2 Facilitates Coat Protein Complex II Assembly and Endoplasmic Reticulum Export in Mammalian Cells

2005 ◽  
Vol 16 (2) ◽  
pp. 835-848 ◽  
Author(s):  
Lori Kapetanovich ◽  
Cassandra Baughman ◽  
Tina H. Lee
Keyword(s):  
Endoplasmic Reticulum ◽  
Coat Protein ◽  
Protein Complex ◽  
Mammalian Cells ◽  
Complex Ii ◽  
Permeabilized Cells ◽  
Er Export ◽  
Coat Protein Complex

The cytosolic coat protein complex II (COPII) mediates vesicle formation from the endoplasmic reticulum (ER) and is essential for ER-to-Golgi trafficking. The minimal machinery for COPII assembly is well established. However, additional factors may regulate the process in mammalian cells. Here, a morphological COPII assembly assay using purified COPII proteins and digitonin-permeabilized cells has been applied to demonstrate a role for a novel component of the COPII assembly pathway. The factor was purified and identified by mass spectrometry as Nm23H2, one of eight isoforms of nucleoside diphosphate kinase in mammalian cells. Importantly, recombinant Nm23H2, as well as a catalytically inactive version, promoted COPII assembly in vitro, suggesting a noncatalytic role for Nm23H2. Consistent with a function for Nm23H2 in ER export, Nm23H2 localized to a reticular network that also stained for the ER marker calnexin. Finally, an in vivo role for Nm23H2 in COPII assembly was confirmed by isoform-specific knockdown of Nm23H2 by using short interfering RNA. Knockdown of Nm23H2, but not its most closely related isoform Nm23H1, resulted in diminished COPII assembly at steady state and reduced kinetics of ER export. These results strongly suggest a previously unappreciated role for Nm23H2 in mammalian ER export.

Microsome-Based Assay for Analysis of Endoplasmic Reticulum to Golgi Transport in Mammalian Cells

Cell Biology ◽  
2006 ◽  
pp. 209-214 ◽  
Author(s):  
H PLUTNER ◽  
C GURKAN ◽  
X WANG ◽  
P LAPOINTE ◽  
W BALCH
Keyword(s):  
Endoplasmic Reticulum ◽  
Mammalian Cells ◽  
Golgi Transport

scholarly journals GOLGI TRANSPORT 1B Regulates Protein Export from the Endoplasmic Reticulum in Rice Endosperm Cells

2016 ◽  
Vol 28 (11) ◽  
pp. 2850-2865 ◽  
Author(s):  
Yihua Wang ◽  
Feng Liu ◽  
Yulong Ren ◽  
Yunlong Wang ◽  
Xi Liu ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Export ◽  
Rice Endosperm ◽  
Golgi Transport

The role of microtubules in transport between the endoplasmic reticulum and Golgi apparatus in mammalian cells.

2005 ◽  
Vol 72 ◽  
pp. 1-13 ◽  
Author(s):  
Krysten J. Palmer ◽  
Peter Watson ◽  
David J. Stephens
Keyword(s):  
Endoplasmic Reticulum ◽  
Mammalian Cells ◽  
Secretory Pathway ◽  
Motor Proteins ◽  
Microtubule Cytoskeleton ◽  
Early Secretory Pathway ◽  
Golgi Transport ◽  
Intracellular Compartments ◽  
Retrograde Traffic

The organization of intracellular compartments and the transfer of components between them are central to the correct functioning of mammalian cells. Proteins and lipids are transferred between compartments by the formation, movement and subsequent specific fusion of transport intermediates. These vesicles and membrane clusters must be coupled to the cytoskeleton and to motor proteins that drive motility. Anterograde ER (endoplasmic reticulum)-to-Golgi transport, and the converse step of retrograde traffic from the Golgi to the ER, are now known to involve coupling of membranes to the microtubule cytoskeleton. Here we shall discuss our current understanding of the mechanisms that link membrane traffic in the early secretory pathway to the microtubule cytoskeleton in mammalian cells. Recent data have also provided molecular detail of functional co-ordination of motor proteins to specify directionality, as well as mechanisms for regulating motor activity by protein phosphorylation.

Regulation of ER-associated degradation via p97/VCP-interacting motif

2008 ◽  
Vol 36 (5) ◽  
pp. 818-822 ◽  
Author(s):  
Petek Ballar ◽  
Shengyun Fang
Keyword(s):  
Endoplasmic Reticulum ◽  
Ubiquitin Ligase ◽  
Terminal Region ◽  
Misfolded Proteins ◽  
Interacting Protein ◽  
Aaa Atpase ◽  
Endoplasmic Reticulum Associated Degradation ◽  
Er Membrane

p97/VCP (valosin-containing protein) is a cytosolic AAA (ATPase associated with various cellular activities) essential for retrotranslocation of misfolded proteins during ERAD [ER (endoplasmic reticulum)-associated degradation]. gp78, an ERAD ubiquitin ligase, is one of the p97/VCP recruitment proteins localized to the ER membrane. A newly identified VIM (p97/VCP-interacting motif) in gp78 has brought about novel insights into mechanisms of ERAD, such as the presence of a p97/VCP-dependent but Ufd1-independent retrotranslocation during gp78-mediated ERAD. Additionally, SVIP (small p97/VCP-interacting protein), which contains a VIM in its N-terminal region, negatively regulates ERAD by uncoupling p97/VCP and Derlin1 from gp78. Thus SVIP may protect cells from damage by extravagant ERAD.

scholarly journals Cholera Toxin Is Exported from Microsomes by the Sec61p Complex

2000 ◽  
Vol 148 (6) ◽  
pp. 1203-1212 ◽  
Author(s):  
Anton Schmitz ◽  
Helga Herrgen ◽  
Alexandra Winkeler ◽  
Volker Herzog
Keyword(s):  
Endoplasmic Reticulum ◽  
Cholera Toxin ◽  
De Novo ◽  
Bacterial Toxins ◽  
Protein Export ◽  
In Vitro Translation ◽  
Unknown Mechanism ◽  
A Cell ◽  
Er Export

After endocytosis cholera toxin is transported to the endoplasmic reticulum (ER), from where its A1 subunit (CTA1) is assumed to be transferred to the cytosol by an as-yet unknown mechanism. Here, export of CTA1 from the ER to the cytosol was investigated in a cell-free assay using either microsomes loaded with CTA1 by in vitro translation or reconstituted microsomes containing CTA1 purified from V. cholerae. Export of CTA1 from the microsomes was time- and adenosine triphosphate–dependent and required lumenal ER proteins. By coimmunoprecipitation CTA1 was shown to be associated during export with the Sec61p complex, which mediates import of proteins into the ER. Export of CTA1 was inhibited when the Sec61p complexes were blocked by nascent polypeptides arrested during import, demonstrating that the export of CTA1 depended on translocation-competent Sec61p complexes. Export of CTA1 from the reconstituted microsomes indicated the de novo insertion of the toxin into the Sec61p complex from the lumenal side. Our results suggest that Sec61p complex–mediated protein export from the ER is not restricted to ER-associated protein degradation but is also used by bacterial toxins, enabling their entry into the cytosol of the target cell.

scholarly journals The Sar1 Gtpase Coordinates Biosynthetic Cargo Selection with Endoplasmic Reticulum Export Site Assembly

2001 ◽  
Vol 152 (1) ◽  
pp. 213-230 ◽  
Author(s):  
Meir Aridor ◽  
Kenneth N. Fish ◽  
Sergei Bannykh ◽  
Jacques Weissman ◽  
Theresa H. Roberts ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Small Gtpase ◽  
Live Cells ◽  
Tubular Structures ◽  
Golgi Transport ◽  
Er Export

Cargo selection and export from the endoplasmic reticulum is mediated by the COPII coat machinery that includes the small GTPase Sar1 and the Sec23/24 and Sec13/31 complexes. We have analyzed the sequential events regulated by purified Sar1 and COPII coat complexes during synchronized export of cargo from the ER in vitro. We find that activation of Sar1 alone, in the absence of other cytosolic components, leads to the formation of ER-derived tubular domains that resemble ER transitional elements that initiate cargo selection. These Sar1-generated tubular domains were shown to be transient, functional intermediates in ER to Golgi transport in vitro. By following cargo export in live cells, we show that ER export in vivo is also characterized by the formation of dynamic tubular structures. Our results demonstrate an unanticipated and novel role for Sar1 in linking cargo selection with ER morphogenesis through the generation of transitional tubular ER export sites.

scholarly journals Golgi Inheritance in Mammalian Cells Is Mediated through Endoplasmic Reticulum Export Activities

2006 ◽  
Vol 17 (2) ◽  
pp. 990-1005 ◽  
Author(s):  
Nihal Altan-Bonnet ◽  
Rachid Sougrat ◽  
Wei Liu ◽  
Erik L. Snapp ◽  
Theresa Ward ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Mammalian Cells ◽  
Live Cell Imaging ◽  
Cell Imaging ◽  
Transmembrane Proteins ◽  
Temperature Sensitive ◽  
Golgi Membranes ◽  
Sequential Inactivation ◽  
Er Export ◽  
Microscopy Techniques

Golgi inheritance during mammalian cell division occurs through the disassembly, partitioning, and reassembly of Golgi membranes. The mechanisms responsible for these processes are poorly understood. To address these mechanisms, we have examined the identity and dynamics of Golgi proteins within mitotic membranes using live cell imaging and electron microscopy techniques. Mitotic Golgi fragments, seen in prometaphase and telophase, were found to localize adjacent to endoplasmic reticulum (ER) export domains, and resident Golgi transmembrane proteins cycled rapidly into and out of these fragments. Golgi proteins within mitotic Golgi haze—seen during metaphase—were found to redistribute with ER markers into fragments when the ER was fragmented by ionomycin treatment. The temperature-sensitive misfolding mutant ts045VSVG protein, when localized to the Golgi at the start of mitosis, became trapped in the ER at the end of mitosis in cells shifted to 40°C. Finally, reporters for Arf1 and Sar1 activity revealed that Arf1 and Sar1 undergo sequential inactivation during mitotic Golgi breakdown and sequential reactivation upon Golgi reassembly at the end of mitosis. Together, these findings support a model of mitotic Golgi inheritance that involves inhibition and subsequent reactivation of cellular activities controlling the cycling of Golgi components into and out of the ER.

scholarly journals RINT-1 Regulates the Localization and Entry of ZW10 to the Syntaxin 18 Complex

2006 ◽  
Vol 17 (6) ◽  
pp. 2780-2788 ◽  
Author(s):  
Kohei Arasaki ◽  
May Taniguchi ◽  
Katsuko Tani ◽  
Mitsuo Tagaya
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Trafficking ◽  
Protein Transport ◽  
Snare Complex ◽  
Checkpoint Control ◽  
Interacting Protein ◽  
Golgi Transport ◽  
Radiation Induced ◽  
And Function

RINT-1 was first identified as a Rad50-interacting protein that participates in radiation-induced G2/M checkpoint control. We have recently reported that RINT-1, together with the dynamitin-interacting protein ZW10 and others, is associated with syntaxin 18, an endoplasmic reticulum (ER)-localized SNARE involved in membrane trafficking between the ER and Golgi. To address the role of RINT-1 in membrane trafficking, we examined the effects of overexpression and knockdown of RINT-1 on Golgi morphology and protein transport from the ER. Overexpression of the N-terminal region of RINT-1, which is responsible for the interaction with ZW10, caused redistribution of ZW10. Concomitantly, ER-to-Golgi transport was blocked and the Golgi was dispersed. Knockdown of RINT-1 also disrupted membrane trafficking between the ER and Golgi. Notably, silencing of RINT-1 resulted in a reduction in the amount of ZW10 associated with syntaxin 18, concomitant with ZW10 redistribution. In contrast, no redistribution or release of RINT-1 from the syntaxin 18 complex was observed when ZW10 expression was reduced. These results taken together suggest that RINT-1 coordinates the localization and function of ZW10 by serving as a link between ZW10 and the SNARE complex comprising syntaxin 18.

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