scholarly journals Vesicular Calcium Regulates Coat Retention, Fusogenicity, and Size of Pre-Golgi Intermediates

2010 ◽  
Vol 21 (6) ◽  
pp. 1033-1046 ◽  
Author(s):  
Marvin Bentley ◽  
Deborah C. Nycz ◽  
Ashwini Joglekar ◽  
Ismene Fertschai ◽  
Roland Malli ◽  
...  
Keyword(s):  
Secretory Pathway ◽  
Rat Kidney ◽  
Cyclopiazonic Acid ◽  
Early Secretory Pathway ◽  
Shell Protein ◽  
Ef Hand ◽  
Copii Vesicle ◽  
Normal Rat ◽  
And Function

The significance and extent of Ca2+ regulation of the biosynthetic secretory pathway have been difficult to establish, and our knowledge of regulatory relationships integrating Ca2+ with vesicle coats and function is rudimentary. Here, we investigated potential roles and mechanisms of luminal Ca2+ in the early secretory pathway. Specific depletion of luminal Ca2+ in living normal rat kidney cells using cyclopiazonic acid (CPA) resulted in the extreme expansion of vesicular tubular cluster (VTC) elements. Consistent with this, a suppressive role for vesicle-associated Ca2+ in COPII vesicle homotypic fusion was demonstrated in vitro using Ca2+ chelators. The EF-hand–containing protein apoptosis-linked gene 2 (ALG-2), previously implicated in the stabilization of sec31 at endoplasmic reticulum exit sites, inhibited COPII vesicle fusion in a Ca2+-requiring manner, suggesting that ALG-2 may be a sensor for the effects of vesicular Ca2+ on homotypic fusion. Immunoisolation established that Ca2+ chelation inhibits and ALG-2 specifically favors residual retention of the COPII outer shell protein sec31 on pre-Golgi fusion intermediates. We conclude that vesicle-associated Ca2+, acting through ALG-2, favors the retention of residual coat molecules that seem to suppress membrane fusion. We propose that in cells, these Ca2+-dependent mechanisms temporally regulate COPII vesicle interactions, VTC biogenesis, cargo sorting, and VTC maturation.

scholarly journals MIA3/TANGO1 enables efficient secretion by constraining COPII vesicle budding

2021 ◽  
Author(s):  
Janine McCaughey ◽  
Judith M. Mantell ◽  
Chris R. Neal ◽  
Kate Heesom ◽  
David J. Stephens
Keyword(s):  
Endoplasmic Reticulum ◽  
Light Microscopy ◽  
Secretory Pathway ◽  
Genome Engineering ◽  
High Volume ◽  
Vesicle Budding ◽  
Early Secretory Pathway ◽  
Copii Vesicle ◽  
Intermediate Compartment ◽  
Golgi Organization

AbstractComplex machinery is required to drive secretory cargo export from the endoplasmic reticulum. In vertebrates, this includes transport and Golgi organization protein 1 (TANGO1), encoded by the Mia3 gene. Here, using genome engineering of human cells light microscopy, secretion assays, and proteomics, we show loss of Mia3/TANGO1 results in formation of numerous vesicles and a loss of early secretory pathway integrity. This restricts secretion not only of large proteins like procollagens but of all types of secretory cargo. Our data shows that Mia3/TANGO1 constrains the propensity of COPII to form vesicles promoting instead the formation of the ER-Golgi intermediate compartment. Thus, Mia3/TANGO1 facilities the secretion of complex and high volume cargoes from vertebrate cells.

scholarly journals EFFECT OF COLLAGEN I GEL ON APOPTOSIS OF RAT HEPATIC STELLATE CELLS

2013 ◽  
Vol 56 (2) ◽  
pp. 73-79
Author(s):  
Lenka Bittnerová ◽  
Alena Jiroutová ◽  
Emil Rudolf ◽  
Martina Řezáčová ◽  
Jiří Kanta
Keyword(s):  
Hepatic Stellate Cells ◽  
Type I Collagen ◽  
Collagen Gel ◽  
Stellate Cells ◽  
Type I ◽  
Function Type ◽  
Fibrotic Liver ◽  
Normal Rat ◽  
And Function

Activated hepatic stellate cells (HSC) are a major source of fibrous proteins in cirrhotic liver. Inducing or accelerating their apoptosis is a potential way of liver fibrosis treatment. Extracellular matrix (ECM) surrounding cells in tissue affects their differentiation, migration, proliferation and function. Type I collagen is the main ECM component in fibrotic liver. We have examined how this protein modifies apoptosis of normal rat HSC induced by gliotoxin, cycloheximide and cytochalasin D in vitro and spontaneous apoptosis of HSC isolated from CCl4-damaged liver. We have found that type I collagen gel enhances HSC apoptosis regardless of the agent triggering this process.

Illuminating cellular structure and function in the early secretory pathway by multispectral 3D imaging in living cells

2000 ◽  
Author(s):  
Jens Rietdorf ◽  
David J. Stephens ◽  
Anthony Squire ◽  
Jeremy Simpson ◽  
David T. Shima ◽  
...  
Keyword(s):  
Cellular Structure ◽  
3D Imaging ◽  
Secretory Pathway ◽  
Living Cells ◽  
Structure And Function ◽  
Early Secretory Pathway ◽  
And Function

scholarly journals A role for Yip1p in COPII vesicle biogenesis

2003 ◽  
Vol 163 (1) ◽  
pp. 57-69 ◽  
Author(s):  
Matthew Heidtman ◽  
Catherine Z. Chen ◽  
Ruth N. Collins ◽  
Charles Barlowe
Keyword(s):  
Secretory Pathway ◽  
Protein Transport ◽  
Genetic Interaction ◽  
Temperature Sensitive ◽  
Rab Gtpases ◽  
Direct Role ◽  
Interacting Protein ◽  
Copii Vesicle ◽  
Vesicle Biogenesis

Yeast Ypt1p-interacting protein (Yip1p) belongs to a conserved family of transmembrane proteins that interact with Rab GTPases. We encountered Yip1p as a constituent of ER-derived transport vesicles, leading us to hypothesize a direct role for this protein in transport through the early secretory pathway. Using a cell-free assay that recapitulates protein transport from the ER to the Golgi complex, we find that affinity-purified antibodies directed against the hydrophilic amino terminus of Yip1p potently inhibit transport. Surprisingly, inhibition is specific to the COPII-dependent budding stage. In support of this in vitro observation, strains bearing the temperature-sensitive yip1-4 allele accumulate ER membranes at a nonpermissive temperature, with no apparent accumulation of vesicle intermediates. Genetic interaction analyses of the yip1-4 mutation corroborate a function in ER budding. Finally, ordering experiments show that preincubation of ER membranes with COPII proteins decreases sensitivity to anti-Yip1p antibodies, indicating an early requirement for Yip1p in vesicle formation. We propose that Yip1p has a previously unappreciated role in COPII vesicle biogenesis.

scholarly journals Erv14p Directs a Transmembrane Secretory Protein into COPII-coated Transport Vesicles

2002 ◽  
Vol 13 (3) ◽  
pp. 880-891 ◽  
Author(s):  
Jacqueline Powers ◽  
Charles Barlowe
Keyword(s):  
Endoplasmic Reticulum ◽  
Secretory Pathway ◽  
Integral Membrane Protein ◽  
Secretory Protein ◽  
Conserved Residues ◽  
Early Secretory Pathway ◽  
Transport Vesicles ◽  
Copii Vesicle ◽  
Copii Vesicles ◽  
Selection Of

Erv14p is a conserved integral membrane protein that traffics in COPII-coated vesicles and localizes to the early secretory pathway in yeast. Deletion of ERV14 causes a defect in polarized growth because Axl2p, a transmembrane secretory protein, accumulates in the endoplasmic reticulum and is not delivered to its site of function on the cell surface. Herein, we show that Erv14p is required for selection of Axl2p into COPII vesicles and for efficient formation of these vesicles. Erv14p binds to subunits of the COPII coat and binding depends on conserved residues in a cytoplasmically exposed loop domain of Erv14p. When mutations are introduced into this loop, an Erv14p-Axl2p complex accumulates in the endoplasmic reticulum, suggesting that Erv14p links Axl2p to the COPII coat. Based on these results and further genetic experiments, we propose Erv14p coordinates COPII vesicle formation with incorporation of specific secretory cargo.

scholarly journals Casein Kinase I Regulates Membrane Binding by ARF GAP1

2002 ◽  
Vol 13 (8) ◽  
pp. 2559-2570 ◽  
Author(s):  
Sidney Yu ◽  
Michael G. Roth
Keyword(s):  
Amino Acid ◽  
Secretory Pathway ◽  
Protein Transport ◽  
Membrane Binding ◽  
Casein Kinase ◽  
Protein Domain ◽  
Amino Terminal ◽  
Early Secretory Pathway

ARF GAP1, a 415-amino acid GTPase activating protein (GAP) for ADP-ribosylation factor (ARF) contains an amino-terminal 115-amino acid catalytic domain and no other recognizable features. Amino acids 203–334 of ARF GAP1 were sufficient to target a GFP-fusion protein to Golgi membranes in vivo. When overexpressed in COS-1 cells, this protein domain inhibited protein transport between the ER and Golgi and, in vitro, competed with the full-length ARF GAP1 for binding to membranes. Membrane binding by ARF GAP1 in vitro was increased by a factor in cytosol and this increase was inhibited by IC261, an inhibitor selective for casein kinase Iδ (CKIδ), or when cytosol was treated with antibody to CKIδ. The noncatalytic domain of ARF GAP1 was phosphorylated both in vivo and in vitro by CKI. IC261 blocked membrane binding by ARF GAP1 in vivo and inhibited protein transport in the early secretory pathway. Overexpression of a catalytically inactive CKIδ also inhibited the binding of ARF GAP1 to membranes and interfered with protein transport. Thus, a CKI isoform is required for protein traffic through the early secretory pathway and can modulate the amount of ARF GAP1 that can bind to membranes.

scholarly journals Bacterial Outer Membrane Ushers Contain Distinct Targeting and Assembly Domains for Pilus Biogenesis

2002 ◽  
Vol 184 (22) ◽  
pp. 6260-6269 ◽  
Author(s):  
David G. Thanassi ◽  
Christos Stathopoulos ◽  
Karen Dodson ◽  
Dominik Geiger ◽  
Scott J. Hultgren
Keyword(s):  
Outer Membrane ◽  
Secretory Pathway ◽  
Terminal Branch ◽  
C Terminus ◽  
Type 1 Pili ◽  
Pilus Biogenesis ◽  
And Function

ABSTRACT Biogenesis of a superfamily of surface structures by gram-negative bacteria requires the chaperone/usher pathway, a terminal branch of the general secretory pathway. In this pathway a periplasmic chaperone works together with an outer membrane usher to direct substrate folding, assembly, and secretion to the cell surface. We analyzed the structure and function of the PapC usher required for P pilus biogenesis by uropathogenic Escherichia coli. Structural analysis indicated PapC folds as a β-barrel with short extracellular loops and extensive periplasmic domains. Several periplasmic regions were localized, including two domains containing conserved cysteine pairs. Functional analysis of deletion mutants revealed that the PapC C terminus was not required for insertion of the usher into the outer membrane or for proper folding. The usher C terminus was not necessary for interaction with chaperone-subunit complexes in vitro but was required for pilus biogenesis in vivo. Interestingly, coexpression of PapC C-terminal truncation mutants with the chromosomal fim gene cluster coding for type 1 pili allowed P pilus biogenesis in vivo. These studies suggest that chaperone-subunit complexes target an N-terminal domain of the usher and that subunit assembly into pili depends on a subsequent function provided by the usher C terminus.

scholarly journals Early secretory pathway localization and lack of processing for hepatitis E virus replication protein pORF1

2013 ◽  
Vol 94 (4) ◽  
pp. 807-816 ◽  
Author(s):  
Julia Perttilä ◽  
Pirjo Spuul ◽  
Tero Ahola
Keyword(s):  
Hepatitis E Virus ◽  
Secretory Pathway ◽  
Hepatitis E ◽  
Proteolytic Processing ◽  
Full Length ◽  
Replication Protein ◽  
Positive Strand ◽  
Early Secretory Pathway ◽  
Positive Strand Rna

Hepatitis E virus (HEV) is a positive-strand RNA virus and a major causative agent of acute sporadic and epidemic hepatitis. HEV replication protein is encoded by ORF1 and contains the predicted domains of methyltransferase (MT), protease, macro domain, helicase (HEL) and polymerase (POL). In this study, the full-length protein pORF1 (1693 aa) and six truncated variants were expressed by in vitro translation and in human HeLa and hepatic Huh-7 cells by using several vector systems. The proteins were visualized by three specific antisera directed against the MT, HEL and POL domains. In vitro translation of full-length pORF1 yielded smaller quantities of two fragments. However, these fragments were not observed after pORF1 expression and pulse–chase studies in human cells, and their production was not dependent on the predicted protease domain in pORF1. The weight of evidence supports the proposition that pORF1 is not subjected to specific proteolytic processing, which is unusual among animal positive-strand RNA viruses but common for plant viruses. pORF1 was membrane associated in cells and localized to a perinuclear region, where it partially overlapped with localization of the endoplasmic reticulum (ER) marker BAP31 and was closely interspersed with staining of the ER–Golgi intermediate compartment marker protein ERGIC-53. Co-localization with BAP31 was enhanced by treatment with brefeldin A. Therefore, HEV may utilize modified early secretory pathway membranes for replication.

scholarly journals A Novel Group of Glutaredoxins in the cis-Golgi Critical for Oxidative Stress Resistance

2008 ◽  
Vol 19 (6) ◽  
pp. 2673-2680 ◽  
Author(s):  
Nikola Mesecke ◽  
Anne Spang ◽  
Marcel Deponte ◽  
Johannes M. Herrmann
Keyword(s):  
Disulfide Bonds ◽  
Secretory Pathway ◽  
Reduced Glutathione ◽  
General Role ◽  
Growth Defects ◽  
Early Secretory Pathway ◽  
Full Complement ◽  
Increased Sensitivity ◽  
Substrate Proteins

Glutaredoxins represent a ubiquitous family of proteins that catalyze the reduction of disulfide bonds in their substrate proteins by use of reduced glutathione. In an attempt to identify the full complement of glutaredoxins in baker's yeast, we found three so-far uncharacterized glutaredoxin-like proteins that we named Grx6, Grx7, and Grx8. Grx6 and Grx7 represent closely related monothiol glutaredoxins that are synthesized with N-terminal signal sequences. Both proteins are located in the cis-Golgi, thereby representing the first glutaredoxins found in a compartment of the secretory pathway. In contrast to formerly described monothiol glutaredoxins, Grx6 and Grx7, showed a high glutaredoxin activity in vitro. Grx6 and Grx7 overlap in their activity and deletion mutants lacking both proteins show growth defects and a strongly increased sensitivity toward oxidizing agents such as hydrogen peroxide or diamide. Our observations suggest that Grx6 and Grx7 do not play a general role in the oxidative folding of proteins in the early secretory pathway but rather counteract the oxidation of specific thiol groups in substrate proteins.

scholarly journals 3′-Untranslated regions of oxidative phosphorylation mRNAs function in vivo as enhancers of translation

2000 ◽  
Vol 352 (1) ◽  
pp. 109-115 ◽  
Author(s):  
Carlo M. Di LIEGRO ◽  
Marianna BELLAFIORE ◽  
José M. IZQUIERDO ◽  
Anja RANTANEN ◽  
José M. CUEZVA
Keyword(s):  
Oxidative Phosphorylation ◽  
Atp Synthase ◽  
Fluorescent Protein ◽  
Rat Kidney ◽  
In Vitro Translation ◽  
Mitochondrial Transcription Factor ◽  
Normal Rat ◽  
Green Fluorescent

Recent findings have indicated that the 3´-untranslated region (3´-UTR) of the mRNA encoding the β-catalytic subunit of the mitochondrial H+-ATP synthase has an in vitro translation-enhancing activity (TEA) [Izquierdo and Cuezva, Mol. Cell. Biol. (1997) 17, 5255–5268; Izquierdo and Cuezva, Biochem. J. (2000) 346, 849–855]. In the present work, we have expressed chimaeric plasmids that encode mRNA variants of green fluorescent protein in normal rat kidney and liver clone 9 cells to determine whether the 3´-UTRs of nuclear-encoded mRNAs involved in the biogenesis of mitochondria have an intrinsic TEA. TEA is found in the 3´-UTR of the mRNAs encoding the α- and β-subunits of the rat H+-ATP synthase complex, as well as in subunit IV of cytochrome c oxidase. No TEA is present in the 3´-UTR of the somatic mRNA encoding rat mitochondrial transcription factor A. Interestingly, the TEA of the 3´-UTR of mRNAs of oxidative phosphorylation is different, depending upon the cell type analysed. These data provide the first in vivo evidence of a novel cell-specific mechanism for the control of the translation of mRNAs required in mitochondrial function.

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