SEC16 in COPII coat dynamics at ER exit sites

2015 ◽  
Vol 43 (1) ◽  
pp. 97-103 ◽  
Author(s):  
Joep Sprangers ◽  
Catherine Rabouille
Keyword(s):  
Endoplasmic Reticulum ◽  
Secretory Pathway ◽  
Protein Transport ◽  
Functional Organization ◽  
Protein Export ◽  
Coated Vesicles ◽  
Loss Of Function ◽  
Exact Function ◽  
Er Exit Sites ◽  
Secretory Capacity

Protein export from the endoplasmic reticulum (ER), the first step in protein transport through the secretory pathway, is mediated by coatomer protein II (COPII)-coated vesicles at ER exit sites. COPII coat assembly on the ER is well understood and the conserved large hydrophilic protein Sec16 clearly has a role to play in COPII coat dynamics. Sec16 localizes to ER exit sites, its loss of function impairs their functional organization in all species where it has been studied, and it interacts with COPII coat subunits. However, its exact function in COPII dynamics is debated, as Sec16 is proposed to act as a scaffold to recruit COPII components and as a device to regulate the Sar1 activity in uncoating, in such a way that the coat is released only when the vesicle is fully formed and loaded with cargo. Furthermore, Sec16 has been shown to respond to nutrient signalling, thus coupling environmental stimuli to secretory capacity.

The yeast SLY gene products, suppressors of defects in the essential GTP-binding Ypt1 protein, may act in endoplasmic reticulum-to-Golgi transport

1991 ◽  
Vol 11 (6) ◽  
pp. 2980-2993
Author(s):  
R Ossig ◽  
C Dascher ◽  
H H Trepte ◽  
H D Schmitt ◽  
D Gallwitz
Keyword(s):  
Endoplasmic Reticulum ◽  
Secretory Pathway ◽  
Protein Transport ◽  
Single Copy ◽  
Integral Membrane Protein ◽  
Carboxypeptidase Y ◽  
Null Mutant ◽  
Yeast Saccharomyces Cerevisiae ◽  
Golgi Transport ◽  
Gtp Binding

It has been shown previously that defects in the essential GTP-binding protein, Ypt1p, lead to a block in protein transport from the endoplasmic reticulum (ER) to the Golgi apparatus in the yeast Saccharomyces cerevisiae. Here we report that four newly discovered suppressors of YPT1 deletion (SLY1-20, SLY2, SLY12, and SLY41) to a varying degree restore ER-to-Golgi transport defects in cells lacking Ypt1p. These suppressors also partially complement the sec21-1 and sec22-3 mutants which lead to a defect early in the secretory pathway. Sly1p-depleted cells, as well as a conditional lethal sly2 null mutant at nonpermissive temperatures, accumulate ER membranes and core-glycosylated invertase and carboxypeptidase Y. The sly2 null mutant under restrictive conditions (37 degrees C) can be rescued by the multicopy suppressor SLY12 and the single-copy suppressor SLY1-20, indicating that these three SLY genes functionally interact. Sly2p is shown to be an integral membrane protein.

scholarly journals A stress assembly that confers cell viability by preserving ERES components during amino-acid starvation

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Margarita Zacharogianni ◽  
Angelica Aguilera-Gomez ◽  
Tineke Veenendaal ◽  
Jan Smout ◽  
Catherine Rabouille
Keyword(s):  
Amino Acid ◽  
Cell Viability ◽  
Secretory Pathway ◽  
Protein Transport ◽  
Liquid Droplet ◽  
Protein Translation ◽  
Amino Acid Starvation ◽  
Early Secretory Pathway ◽  
Er Exit Sites ◽  
Nutritional Restriction

Nutritional restriction leads to protein translation attenuation that results in the storage and degradation of free mRNAs in cytoplasmic assemblies. In this study, we show in Drosophila S2 cells that amino-acid starvation also leads to the inhibition of another major anabolic pathway, the protein transport through the secretory pathway, and to the formation of a novel reversible non-membrane bound stress assembly, the Sec body that incorporates components of the ER exit sites. Sec body formation does not depend on membrane traffic in the early secretory pathway, yet requires both Sec23 and Sec24AB. Sec bodies have liquid droplet-like properties, and they act as a protective reservoir for ERES components to rebuild a functional secretory pathway after re-addition of amino-acids acting as a part of a survival mechanism. Taken together, we propose that the formation of these structures is a novel stress response mechanism to provide cell viability during and after nutrient stress.

scholarly journals Pathogenic Effects of Impaired Retrieval between the Endoplasmic Reticulum and Golgi Complex

2019 ◽  
Vol 20 (22) ◽  
pp. 5614 ◽  
Author(s):  
Hiroshi Kokubun ◽  
Hisayo Jin ◽  
Tomohiko Aoe
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Complex ◽  
Secretory Pathway ◽  
Protein Transport ◽  
Receptor Activation ◽  
Toxic Substances ◽  
Bidirectional Transport ◽  
The Unfolded Protein Response ◽  
Kdel Receptor ◽  
Kdel Sequence

Cellular activities, such as growth and secretion, are dependent on correct protein folding and intracellular protein transport. Injury, like ischemia, malnutrition, and invasion of toxic substances, affect the folding environment in the endoplasmic reticulum (ER). The ER senses this information, following which cells adapt their response to varied situations through the unfolded protein response. Activation of the KDEL receptor, resulting from the secretion from the ER of chaperones containing the KDEL sequence, plays an important role in this adaptation. The KDEL receptor was initially shown to be necessary for the retention of KDEL sequence-containing proteins in the ER. However, it has become clear that the activated KDEL receptor also regulates bidirectional transport between the ER and the Golgi complex, as well as from the Golgi to the secretory pathway. In addition, it has been suggested that the signal for KDEL receptor activation may also affect several other cellular activities. In this review, we discuss KDEL receptor-mediated bidirectional transport and signaling and describe disease models and human diseases related to KDEL receptor dysfunction.

scholarly journals Two Endoplasmic Reticulum (ER) Membrane Proteins That Facilitate ER-to-Golgi Transport of Glycosylphosphatidylinositol-anchored Proteins

1999 ◽  
Vol 10 (4) ◽  
pp. 1043-1059 ◽  
Author(s):  
Wolfgang P. Barz ◽  
Peter Walter
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Surface ◽  
Secretory Pathway ◽  
Protein Transport ◽  
Protein Translocation ◽  
Sequence Similarity ◽  
Surface Proteins ◽  
Golgi Transport ◽  
Er Membrane

Many eukaryotic cell surface proteins are anchored in the lipid bilayer through glycosylphosphatidylinositol (GPI). GPI anchors are covalently attached in the endoplasmic reticulum (ER). The modified proteins are then transported through the secretory pathway to the cell surface. We have identified two genes inSaccharomyces cerevisiae, LAG1 and a novel gene termed DGT1 (for “delayed GPI-anchored protein transport”), encoding structurally related proteins with multiple membrane-spanning domains. Both proteins are localized to the ER, as demonstrated by immunofluorescence microscopy. Deletion of either gene caused no detectable phenotype, whereas lag1Δ dgt1Δ cells displayed growth defects and a significant delay in ER-to-Golgi transport of GPI-anchored proteins, suggesting thatLAG1 and DGT1 encode functionally redundant or overlapping proteins. The rate of GPI anchor attachment was not affected, nor was the transport rate of several non–GPI-anchored proteins. Consistent with a role of Lag1p and Dgt1p in GPI-anchored protein transport, lag1Δ dgt1Δ cells deposit abnormal, multilayered cell walls. Both proteins have significant sequence similarity to TRAM, a mammalian membrane protein thought to be involved in protein translocation across the ER membrane. In vivo translocation studies, however, did not detect any defects in protein translocation in lag1Δ dgt1Δcells, suggesting that neither yeast gene plays a role in this process. Instead, we propose that Lag1p and Dgt1p facilitate efficient ER-to-Golgi transport of GPI-anchored proteins.

scholarly journals Requirement for Neo1p in Retrograde Transport from the Golgi Complex to the Endoplasmic Reticulum

2003 ◽  
Vol 14 (12) ◽  
pp. 4971-4983 ◽  
Author(s):  
Zhaolin Hua ◽  
Todd R. Graham
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Complex ◽  
Secretory Pathway ◽  
Protein Transport ◽  
Retrograde Transport ◽  
Transport Pathway ◽  
Transport Defect ◽  
Copii Vesicles ◽  
P Type ◽  
Adp Ribosylation Factor

Neo1p from Saccharomyces cerevisiae is an essential P-type ATPase and potential aminophospholipid translocase (flippase) in the Drs2p family. We have previously implicated Drs2p in protein transport steps in the late secretory pathway requiring ADP-ribosylation factor (ARF) and clathrin. Here, we present evidence that epitope-tagged Neo1p localizes to the endoplasmic reticulum (ER) and Golgi complex and is required for a retrograde transport pathway between these organelles. Using conditional alleles of NEO1, we find that loss of Neo1p function causes cargo-specific defects in anterograde protein transport early in the secretory pathway and perturbs glycosylation in the Golgi complex. Rer1-GFP, a protein that cycles between the ER and Golgi complex in COPI and COPII vesicles, is mislocalized to the vacuole in neo1-ts at the nonpermissive temperature. These phenotypes suggest that the anterograde protein transport defect is a secondary consequence of a defect in a COPI-dependent retrograde pathway. We propose that loss of lipid asymmetry in the cis Golgi perturbs retrograde protein transport to the ER.

scholarly journals The yeast SLY gene products, suppressors of defects in the essential GTP-binding Ypt1 protein, may act in endoplasmic reticulum-to-Golgi transport.

1991 ◽  
Vol 11 (6) ◽  
pp. 2980-2993 ◽  
Author(s):  
R Ossig ◽  
C Dascher ◽  
H H Trepte ◽  
H D Schmitt ◽  
D Gallwitz
Keyword(s):  
Endoplasmic Reticulum ◽  
Secretory Pathway ◽  
Protein Transport ◽  
Single Copy ◽  
Integral Membrane Protein ◽  
Carboxypeptidase Y ◽  
Null Mutant ◽  
Yeast Saccharomyces Cerevisiae ◽  
Golgi Transport ◽  
Gtp Binding

It has been shown previously that defects in the essential GTP-binding protein, Ypt1p, lead to a block in protein transport from the endoplasmic reticulum (ER) to the Golgi apparatus in the yeast Saccharomyces cerevisiae. Here we report that four newly discovered suppressors of YPT1 deletion (SLY1-20, SLY2, SLY12, and SLY41) to a varying degree restore ER-to-Golgi transport defects in cells lacking Ypt1p. These suppressors also partially complement the sec21-1 and sec22-3 mutants which lead to a defect early in the secretory pathway. Sly1p-depleted cells, as well as a conditional lethal sly2 null mutant at nonpermissive temperatures, accumulate ER membranes and core-glycosylated invertase and carboxypeptidase Y. The sly2 null mutant under restrictive conditions (37 degrees C) can be rescued by the multicopy suppressor SLY12 and the single-copy suppressor SLY1-20, indicating that these three SLY genes functionally interact. Sly2p is shown to be an integral membrane protein.

scholarly journals An in vitro vesicle formation assay reveals cargo clients and factors that mediate vesicular trafficking

2021 ◽  
Vol 118 (35) ◽  
pp. e2101287118
Author(s):  
Yan Huang ◽  
Haidi Yin ◽  
Baiying Li ◽  
Qian Wu ◽  
Yang Liu ◽  
...  
Keyword(s):  
Secretory Pathway ◽  
Molecular Mechanisms ◽  
Protein Transport ◽  
Vesicular Trafficking ◽  
Vesicle Formation ◽  
Dependent Manner ◽  
Vitro Assay ◽  
Cargo Proteins ◽  
Er Exit Sites

The fidelity of protein transport in the secretory pathway relies on the accurate sorting of proteins to their correct destinations. To deepen our understanding of the underlying molecular mechanisms, it is important to develop a robust approach to systematically reveal cargo proteins that depend on specific sorting machinery to be enriched into transport vesicles. Here, we used an in vitro assay that reconstitutes packaging of human cargo proteins into vesicles to quantify cargo capture. Quantitative mass spectrometry (MS) analyses of the isolated vesicles revealed cytosolic proteins that are associated with vesicle membranes in a GTP-dependent manner. We found that two of them, FAM84B (also known as LRAT domain containing 2 or LRATD2) and PRRC1, contain proline-rich domains and regulate anterograde trafficking. Further analyses revealed that PRRC1 is recruited to endoplasmic reticulum (ER) exit sites, interacts with the inner COPII coat, and its absence increases membrane association of COPII. In addition, we uncovered cargo proteins that depend on GTP hydrolysis to be captured into vesicles. Comparing control cells with cells depleted of the cargo receptors, SURF4 or ERGIC53, we revealed specific clients of each of these two export adaptors. Our results indicate that the vesicle formation assay in combination with quantitative MS analysis is a robust and powerful tool to uncover novel factors that mediate vesicular trafficking and to uncover cargo clients of specific cellular factors.

scholarly journals Transmembrane domain–dependent partitioning of membrane proteins within the endoplasmic reticulum

2008 ◽  
Vol 181 (1) ◽  
pp. 105-118 ◽  
Author(s):  
Paolo Ronchi ◽  
Sara Colombo ◽  
Maura Francolini ◽  
Nica Borgese
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Membrane Proteins ◽  
Secretory Pathway ◽  
Transmembrane Domain ◽  
Fluorescent Proteins ◽  
Lipid Interactions ◽  
Er Exit Sites ◽  
Physicochemical Features ◽  
Er Membrane

The length and hydrophobicity of the transmembrane domain (TMD) play an important role in the sorting of membrane proteins within the secretory pathway; however, the relative contributions of protein–protein and protein–lipid interactions to this phenomenon are currently not understood. To investigate the mechanism of TMD-dependent sorting, we used the following two C tail–anchored fluorescent proteins (FPs), which differ only in TMD length: FP-17, which is anchored to the endoplasmic reticulum (ER) membrane by 17 uncharged residues, and FP-22, which is driven to the plasma membrane by its 22-residue-long TMD. Before export of FP-22, the two constructs, although freely diffusible, were seen to distribute differently between ER tubules and sheets. Analyses in temperature-blocked cells revealed that FP-17 is excluded from ER exit sites, whereas FP-22 is recruited to them, although it remains freely exchangeable with the surrounding reticulum. Thus, physicochemical features of the TMD influence sorting of membrane proteins both within the ER and at the ER–Golgi boundary by simple receptor-independent mechanisms based on partitioning.

scholarly journals A membrane glycoprotein, Sec12p, required for protein transport from the endoplasmic reticulum to the Golgi apparatus in yeast.

1988 ◽  
Vol 107 (3) ◽  
pp. 851-863 ◽  
Author(s):  
A Nakano ◽  
D Brada ◽  
R Schekman
Keyword(s):  
Amino Acids ◽  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Membrane Fraction ◽  
Secretory Pathway ◽  
Protein Transport ◽  
Genomic Library ◽  
Membrane Glycoprotein ◽  
Mobility Shift ◽  
Cloned Gene

SEC12, a gene that is required for secretory, membrane, and vacuolar proteins to be transported from the endoplasmic reticulum to the Golgi apparatus, has been cloned from a genomic library by complementation of a sec12 ts mutation. Genetic analysis has shown that the cloned gene integrates at the SEC12 locus and that a null mutation at the locus is lethal. The DNA sequence predicts a protein of 471 amino acids containing a hydrophobic stretch of 19 amino acids near the COOH terminus. To characterize the gene product (Sec12p) in detail, a lacZ-SEC12 gene fusion has been constructed and a polyclonal antibody raised against the hybrid protein. The antibody recognizes Sec12p as a approximately 70-kD protein that sediments in a mixed membrane fraction that includes endoplasmic reticulum. Sec12p is not removed from the membrane fraction by treatment at high pH and high salt and is not degraded by exogenous protease unless detergent is present. Glycosylation of Sec12p during biogenesis is indicated by an electrophoretic mobility shift of the protein that is influenced by tunicamycin and by imposition of an independent secretory pathway block. We suggest that Sec12p is an integral membrane glycoprotein with a prominent domain that faces the cytoplasm where it functions to promote protein transport to the Golgi apparatus. In the process of transport, Sec12p itself may migrate to the Golgi apparatus and function in subsequent transport events.

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