Faculty Opinions recommendation of The organization of engaged and quiescent translocons in the endoplasmic reticulum of mammalian cells.

2004 ◽  
Author(s):  
Karin Romisch
Keyword(s):  
Endoplasmic Reticulum ◽  
Mammalian Cells

Use of Uranium-Labeled Antibodies for Electron Microscopic Localization of Various Antigens in Mammalian Cells

1967 ◽  
Vol 25 ◽  
pp. 136-137
Author(s):  
J. P. Petrali ◽  
E. J. Donati ◽  
L. A. Sternberger
Keyword(s):  
Endoplasmic Reticulum ◽  
Hela Cells ◽  
Mammalian Cells ◽  
Specific Antiserum ◽  
Electron Microscopic ◽  
E Coli ◽  
Cytoplasmic Membranes ◽  
Viral Progeny ◽  
Ultrathin Sections ◽  
Electron Microscopic Localization

Specific contrast is conferred to subcellular antigen by applying purified antibodies, exhaustively labeled with uranium under immunospecific protection, to ultrathin sections. Use of Seligman’s principle of bridging osmium to metal via thiocarbohydrazide (TCH) intensifies specific contrast. Ultrathin sections of osmium-fixed materials were stained on the grid by application of 1) thiosemicarbazide (TSC), 2) unlabeled specific antiserum, 3) uranium-labeled anti-antibody and 4) TCH followed by reosmication. Antigens to be localized consisted of vaccinia antigen in infected HeLa cells, lysozyme in monocytes of patients with monocytic or monomyelocytic leukemia, and fibrinogen in the platelets of these leukemic patients. Control sections were stained with non-specific antiserum (E. coli).In the vaccinia-HeLa system, antigen was localized from 1 to 3 hours following infection, and was confined to degrading virus, the inner walls of numerous organelles, and other structures in cytoplasmic foci. Surrounding architecture and cellular mitochondria were unstained. 8 to 14 hours after infection, antigen was localized on the outer walls of the viral progeny, on cytoplasmic membranes, and free in the cytoplasm. Staining of endoplasmic reticulum was intense and focal early, and weak and diffuse late in infection.

TMCC3 localizes at the three-way junctions for the proper tubular network of the endoplasmic reticulum

2019 ◽  
Vol 476 (21) ◽  
pp. 3241-3260
Author(s):  
Sindhu Wisesa ◽  
Yasunori Yamamoto ◽  
Toshiaki Sakisaka
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Proteins ◽  
Membrane Protein ◽  
Mammalian Cells ◽  
Coiled Coil ◽  
Transmembrane Domains ◽  
Domain Family ◽  
Coiled Coil Domain ◽  
U2os Cells ◽  
Er Membrane

The tubular network of the endoplasmic reticulum (ER) is formed by connecting ER tubules through three-way junctions. Two classes of the conserved ER membrane proteins, atlastins and lunapark, have been shown to reside at the three-way junctions so far and be involved in the generation and stabilization of the three-way junctions. In this study, we report TMCC3 (transmembrane and coiled-coil domain family 3), a member of the TEX28 family, as another ER membrane protein that resides at the three-way junctions in mammalian cells. When the TEX28 family members were transfected into U2OS cells, TMCC3 specifically localized at the three-way junctions in the peripheral ER. TMCC3 bound to atlastins through the C-terminal transmembrane domains. A TMCC3 mutant lacking the N-terminal coiled-coil domain abolished localization to the three-way junctions, suggesting that TMCC3 localized independently of binding to atlastins. TMCC3 knockdown caused a decrease in the number of three-way junctions and expansion of ER sheets, leading to a reduction of the tubular ER network in U2OS cells. The TMCC3 knockdown phenotype was partially rescued by the overexpression of atlastin-2, suggesting that TMCC3 knockdown would decrease the activity of atlastins. These results indicate that TMCC3 localizes at the three-way junctions for the proper tubular ER network.

Oxidative protein folding in the mammalian endoplasmic reticulum

2004 ◽  
Vol 32 (5) ◽  
pp. 655-658 ◽  
Author(s):  
C.E. Jessop ◽  
S. Chakravarthi ◽  
R.H. Watkins ◽  
N.J. Bulleid
Keyword(s):  
Endoplasmic Reticulum ◽  
Mammalian Cells ◽  
Redox State ◽  
Structure And Function ◽  
Reduced Form ◽  
Secretory Proteins ◽  
Oxidative Protein Folding ◽  
Disulphide Bonds ◽  
And Function ◽  
Substrate Proteins

Native disulphide bonds are essential for the structure and function of many membrane and secretory proteins. Disulphide bonds are formed, reduced and isomerized in the endoplasmic reticulum of mammalian cells by a family of oxidoreductases, which includes protein disulphide isomerase (PDI), ERp57, ERp72, P5 and PDIR. This review will discuss how these enzymes are maintained in either an oxidized redox state that allows them to form disulphide bonds in substrate proteins or a reduced form that allows them to perform isomerization and reduction reactions, how these opposing pathways may co-exist within the same compartment and why so many oxidoreductases exist when PDI alone can perform all three of these functions.

scholarly journals Rab1b regulates vesicular transport between the endoplasmic reticulum and successive Golgi compartments.

1991 ◽  
Vol 115 (1) ◽  
pp. 31-43 ◽  
Author(s):  
H Plutner ◽  
A D Cox ◽  
S Pind ◽  
R Khosravi-Far ◽  
J R Bourne ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Mammalian Cells ◽  
Essential Role ◽  
Secretory Pathway ◽  
Binding Protein ◽  
Vesicular Transport ◽  
Initial Step ◽  
Gtp Binding Protein ◽  
Gtp Binding ◽  
Golgi Compartment

We report an essential role for the ras-related small GTP-binding protein rab1b in vesicular transport in mammalian cells. mAbs detect rab1b in both the ER and Golgi compartments. Using an assay which reconstitutes transport between the ER and the cis-Golgi compartment, we find that rab1b is required during an initial step in export of protein from the ER. In addition, it is also required for transport of protein between successive cis- and medial-Golgi compartments. We suggest that rab1b may provide a common link between upstream and downstream components of the vesicular fission and fusion machinery functioning in early compartments of the secretory pathway.

scholarly journals Hierarchical regulation of mRNA partitioning between the cytoplasm and the endoplasmic reticulum of mammalian cells

2011 ◽  
Vol 22 (14) ◽  
pp. 2646-2658 ◽  
Author(s):  
Qiang Chen ◽  
Sujatha Jagannathan ◽  
David W. Reid ◽  
Tianli Zheng ◽  
Christopher V. Nicchitta
Keyword(s):  
Endoplasmic Reticulum ◽  
Mammalian Cells ◽  
Secretory Pathway ◽  
Signal Recognition Particle ◽  
Signal Recognition ◽  
Endomembrane System ◽  
Genomic Analyses ◽  
Specific Manner ◽  
Signal Encoding ◽  
Mrna Transcriptome

The mRNA transcriptome is currently thought to be partitioned between the cytosol and endoplasmic reticulum (ER) compartments by binary selection; mRNAs encoding cytosolic/nucleoplasmic proteins are translated on free ribosomes, and mRNAs encoding topogenic signal-bearing proteins are translated on ER-bound ribosomes, with ER localization being conferred by the signal-recognition particle pathway. In subgenomic and genomic analyses of subcellular mRNA partitioning, we report an overlapping subcellular distribution of cytosolic/nucleoplasmic and topogenic signal-encoding mRNAs, with mRNAs of both cohorts displaying noncanonical subcellular partitioning patterns. Unexpectedly, the topogenic signal-encoding mRNA transcriptome was observed to partition in a hierarchical, cohort-specific manner. mRNAs encoding resident proteins of the endomembrane system were clustered at high ER-enrichment values, whereas mRNAs encoding secretory pathway cargo were broadly represented on free and ER-bound ribosomes. Two distinct modes of mRNA association with the ER were identified. mRNAs encoding endomembrane-resident proteins were bound via direct, ribosome-independent interactions, whereas mRNAs encoding secretory cargo displayed predominantly ribosome-dependent modes of ER association. These data indicate that mRNAs are partitioned between the cytosol and ER compartments via a hierarchical system of intrinsic and encoded topogenic signals and identify mRNA cohort-restricted modes of mRNA association with the ER.

scholarly journals Miga-mediated endoplasmic reticulum–mitochondria contact sites regulate neuronal homeostasis

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Lingna Xu ◽  
Xi Wang ◽  
Jia Zhou ◽  
Yunyi Qiu ◽  
Weina Shang ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Mammalian Cells ◽  
Mitochondrial Dynamics ◽  
Molecular Organization ◽  
Lipid Transport ◽  
Cellular Processes ◽  
Contact Sites ◽  
Neuronal Homeostasis ◽  
Higher Eukaryotes ◽  
Lateral Sclerosis

Endoplasmic reticulum (ER)–mitochondria contact sites (ERMCSs) are crucial for multiple cellular processes such as calcium signaling, lipid transport, and mitochondrial dynamics. However, the molecular organization, functions, regulation of ERMCS, and the physiological roles of altered ERMCSs are not fully understood in higher eukaryotes. We found that Miga, a mitochondrion located protein, markedly increases ERMCSs and causes severe neurodegeneration upon overexpression in fly eyes. Miga interacts with an ER protein Vap33 through its FFAT-like motif and an amyotrophic lateral sclerosis (ALS) disease related Vap33 mutation considerably reduces its interaction with Miga. Multiple serine residues inside and near the Miga FFAT motif were phosphorylated, which is required for its interaction with Vap33 and Miga-mediated ERMCS formation. The interaction between Vap33 and Miga promoted further phosphorylation of upstream serine/threonine clusters, which fine-tuned Miga activity. Protein kinases CKI and CaMKII contribute to Miga hyperphosphorylation. MIGA2, encoded by the miga mammalian ortholog, has conserved functions in mammalian cells. We propose a model that shows Miga interacts with Vap33 to mediate ERMCSs and excessive ERMCSs lead to neurodegeneration.

scholarly journals Retrograde trafficking of Argonaute 2 acts as a rate-limiting step for de novo miRNP formation on endoplasmic reticulum–attached polysomes in mammalian cells

2020 ◽  
Vol 3 (2) ◽  
pp. e201800161 ◽  
Author(s):  
Mainak Bose ◽  
Susanta Chatterjee ◽  
Yogaditya Chakrabarty ◽  
Bahnisikha Barman ◽  
Suvendra N Bhattacharyya
Keyword(s):  
Endoplasmic Reticulum ◽  
Mammalian Cells ◽  
De Novo ◽  
Mirna Biogenesis ◽  
Argonaute 2 ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Cellular Context ◽  
Subcellular Compartmentalization ◽  
Rate Limiting

microRNAs are short regulatory RNAs in metazoan cells. Regulation of miRNA activity and abundance is evident in human cells where availability of target messages can influence miRNA biogenesis by augmenting the Dicer1-dependent processing of precursors to mature microRNAs. Requirement of subcellular compartmentalization of Ago2, the key component of miRNA repression machineries, for the controlled biogenesis of miRNPs is reported here. The process predominantly happens on the polysomes attached with the endoplasmic reticulum for which the subcellular Ago2 trafficking is found to be essential. Mitochondrial tethering of endoplasmic reticulum and its interaction with endosomes controls Ago2 availability. In cells with depolarized mitochondria, miRNA biogenesis gets impaired, which results in lowering of de novo–formed mature miRNA levels and accumulation of miRNA-free Ago2 on endosomes that fails to interact with Dicer1 and to traffic back to endoplasmic reticulum for de novo miRNA loading. Thus, mitochondria by sensing the cellular context regulates Ago2 trafficking at the subcellular level, which acts as a rate-limiting step in miRNA biogenesis process in mammalian cells.

scholarly journals Divergent Mitochondrial and Endoplasmic Reticulum Association of DMPK Splice Isoforms Depends on Unique Sequence Arrangements in Tail Anchors

2005 ◽  
Vol 25 (4) ◽  
pp. 1402-1414 ◽  
Author(s):  
René E. M. A. van Herpen ◽  
Ralph J. A. Oude Ophuis ◽  
Mietske Wijers ◽  
Miranda B. Bennink ◽  
Fons A. J. van de Loo ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Kinase ◽  
Myotonic Dystrophy ◽  
Mammalian Cells ◽  
Cell Types ◽  
Unique Sequence ◽  
Protein Isoforms ◽  
Mitochondrial Outer Membrane ◽  
Splice Isoforms ◽  
Triplet Repeat Expansion

ABSTRACT Myotonic dystrophy protein kinase (DMPK) is a Ser/Thr-type protein kinase with unknown function, originally identified as the product of the gene that is mutated by triplet repeat expansion in patients with myotonic dystrophy type 1 (DM1). Alternative splicing of DMPK transcripts results in multiple protein isoforms carrying distinct C termini. Here, we demonstrate by expressing individual DMPKs in various cell types, including C2C12 and DMPK −/− myoblast cells, that unique sequence arrangements in these tails control the specificity of anchoring into intracellular membranes. Mouse DMPK A and C were found to associate specifically with either the endoplasmic reticulum (ER) or the mitochondrial outer membrane, whereas the corresponding human DMPK A and C proteins both localized to mitochondria. Expression of mouse and human DMPK A—but not C—isoforms in mammalian cells caused clustering of ER or mitochondria. Membrane association of DMPK isoforms was resistant to alkaline conditions, and mutagenesis analysis showed that proper anchoring was differentially dependent on basic residues flanking putative transmembrane domains, demonstrating that DMPK tails form unique tail anchors. This work identifies DMPK as the first kinase in the class of tail-anchored proteins, with a possible role in organelle distribution and dynamics.

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