[26] Use of sec mutants to define intermediates in protein transport from endoplasmic reticulum

1992 ◽  
pp. 267-286 ◽  
Author(s):  
Michael F. Rexach ◽  
Randy W. Schekman
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Transport

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 Myosin Motors and Not Actin Comets Are Mediators of the Actin-based Golgi-to-Endoplasmic Reticulum Protein Transport

2003 ◽  
Vol 14 (2) ◽  
pp. 445-459 ◽  
Author(s):  
Juan M. Durán ◽  
Ferran Valderrama ◽  
Susana Castel ◽  
Juana Magdalena ◽  
Mónica Tomás ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Complex ◽  
Light Chain ◽  
Shiga Toxin ◽  
Actin Filaments ◽  
Protein Transport ◽  
Myosin Ii ◽  
Nonmuscle Myosin ◽  
Nonmuscle Myosin Ii ◽  
Myosin Motors

We have previously reported that actin filaments are involved in protein transport from the Golgi complex to the endoplasmic reticulum. Herein, we examined whether myosin motors or actin comets mediate this transport. To address this issue we have used, on one hand, a combination of specific inhibitors such as 2,3-butanedione monoxime (BDM) and 1-[5-isoquinoline sulfonyl]-2-methyl piperazine (ML7), which inhibit myosin and the phosphorylation of myosin II by the myosin light chain kinase, respectively; and a mutant of the nonmuscle myosin II regulatory light chain, which cannot be phosphorylated (MRLC2AA). On the other hand, actin comet tails were induced by the overexpression of phosphatidylinositol phosphate 5-kinase. Cells treated with BDM/ML7 or those that express the MRLC2AA mutant revealed a significant reduction in the brefeldin A (BFA)-induced fusion of Golgi enzymes with the endoplasmic reticulum (ER). This delay was not caused by an alteration in the formation of the BFA-induced tubules from the Golgi complex. In addition, the Shiga toxin fragment B transport from the Golgi complex to the ER was also altered. This impairment in the retrograde protein transport was not due to depletion of intracellular calcium stores or to the activation of Rho kinase. Neither the reassembly of the Golgi complex after BFA removal nor VSV-G transport from ER to the Golgi was altered in cells treated with BDM/ML7 or expressing MRLC2AA. Finally, transport carriers containing Shiga toxin did not move into the cytosol at the tips of comet tails of polymerizing actin. Collectively, the results indicate that 1) myosin motors move to transport carriers from the Golgi complex to the ER along actin filaments; 2) nonmuscle myosin II mediates in this process; and 3) actin comets are not involved in retrograde transport.

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.

Homocysteine inhibits von Willebrand factor processing and secretion by preventing transport from the endoplasmic reticulum

Blood ◽  
1993 ◽  
Vol 81 (3) ◽  
pp. 683-689 ◽  
Author(s):  
SR Lentz ◽  
JE Sadler
Keyword(s):  
Endothelial Cells ◽  
Endoplasmic Reticulum ◽  
Endothelial Cell ◽  
Von Willebrand Factor ◽  
Protein Transport ◽  
Cell Protein ◽  
Carboxyl Terminal ◽  
Insulinoma Cells ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract Intracellular protein transport in endothelial cells is selectively inhibited by homocysteine, a thiol amino acid associated with both thrombosis and atherosclerosis. In a previous study, homocysteine decreased cell surface expression of the surface transmembrane glycoprotein thrombomodulin without decreasing secretion of another endothelial cell protein, plasminogen activator inhibitor-1. To define further the effects of homocysteine on protein transport, we examined the processing and secretion of the multimeric glycoprotein von Willebrand factor (vWF) in human umbilical vein endothelial cells. Incubation with 2 mmol/L homocysteine resulted in complete loss of vWF multimers and prevented asparagine-linked oligosaccharide maturation, propeptide cleavage, and secretion; these effects are consistent with impaired exit from the endoplasmic reticulum (ER). Dimerization was only partially inhibited, suggesting that homocysteine causes retention of provWF in the ER without preventing dimer formation. In pulse-chase incubations, intracellular provWF was degraded before exiting the ER in homocysteine-treated cells. Homocysteine also inhibited the processing and secretion of a carboxyl-terminal truncation mutant of human provWF expressed in rat insulinoma cells, indicating that retention in the endoplasmic reticulum can be mediated by regions of provWF apart from the carboxyl-terminal 20-Kd segment. These results suggest that retention of secretory proteins in the ER is regulated by redox mechanisms and imply that the intracellular transport of multiple endothelial cell proteins may be altered in patients with homocystinuria.

scholarly journals Okadaic Acid Induces Selective Arrest of Protein Transport in the Rough Endoplasmic Reticulum and Prevents Export into COPII-Coated Structures

1998 ◽  
Vol 18 (2) ◽  
pp. 1125-1135 ◽  
Author(s):  
James G. Pryde ◽  
Theodora Farmaki ◽  
John M. Lucocq
Keyword(s):  
Endoplasmic Reticulum ◽  
G Protein ◽  
Okadaic Acid ◽  
Protein Transport ◽  
Subcellular Fractionation ◽  
Cell Fractionation ◽  
Membrane Structures ◽  
Golgi Stack ◽  
Aluminium Fluoride ◽  
Quantitative Immunoelectron Microscopy

ABSTRACT Quantitative immunoelectron microscopy and subcellular fractionation established the site of endoplasmic reticulum (ER)-Golgi transport arrest induced by the phosphatase inhibitor okadaic acid (OA). OA induced the disappearance of transitional element tubules and accumulation of the anterograde-transported Chandipura (CHP) virus G protein only in the rough ER (RER) and not at more distal sites. The block was specific to the early part of the anterograde pathway, because CHP virus G protein that accumulated in the intermediate compartment (IC) at 15°C could gain access to Golgi stack enzymes. OA also induced RER accumulation of the IC protein p53/p58 via an IC-RER recycling pathway which was resistant to OA and inhibited by the G protein activator aluminium fluoride. The role of COPII coats in OA transport block was investigated by using immunofluorescence and cell fractionation. In untreated cells the COPII coat protein sec 13p colocalized with p53/p58 in Golgi-IC structures of the juxtanuclear region and peripheral cytoplasm. During OA treatment, p53/p58 accumulated in the RER but was excluded from sec 13p-containing membrane structures. Taken together our data indicate that OA induces an early defect in RER export which acts to prevent entry into COPII-coated structures of the IC region.

Glycan-Mediated Protein Transport from the Endoplasmic Reticulum

Sugar Chains ◽  
2014 ◽  
pp. 21-34
Author(s):  
Morihisa Fujita ◽  
Xiao-Dong Gao ◽  
Taroh Kinoshita
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Transport

scholarly journals Structural basis for coupling protein transport and N-glycosylation at the mammalian endoplasmic reticulum

Science ◽  
2018 ◽  
Vol 360 (6385) ◽  
pp. 215-219 ◽  
Author(s):  
Katharina Braunger ◽  
Stefan Pfeffer ◽  
Shiteshu Shrimal ◽  
Reid Gilmore ◽  
Otto Berninghausen ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Transport ◽  
Structural Basis ◽  
Coupling Protein

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.

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