scholarly journals Analyzing mRNA Localization to the Endoplasmic Reticulum via Cell Fractionation

2011 ◽  
pp. 301-321 ◽  
Author(s):  
Sujatha Jagannathan ◽  
Christine Nwosu ◽  
Christopher V. Nicchitta
Keyword(s):  
Endoplasmic Reticulum ◽  
Mrna Localization ◽  
Cell Fractionation

A simple biochemical approach to quantitate rough endoplasmic reticulum

1995 ◽  
Vol 268 (2) ◽  
pp. C308-C316 ◽  
Author(s):  
A. K. Rajasekaran ◽  
S. A. Langhans-Rajasekaran ◽  
R. M. Gould ◽  
E. Rodriguez-Boulan ◽  
T. Morimoto
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Line ◽  
Rough Endoplasmic Reticulum ◽  
Cell Membranes ◽  
Fold Increase ◽  
Sucrose Density Gradient ◽  
Total Cell ◽  
Cell Fractionation ◽  
Cell Line Hela ◽  
Membrane Bound

In this report we demonstrate that the changes in size of the rough endoplasmic reticulum (RER) can be determined by quantifying the membrane-bound ribosomal population separated by cell fractionation and sucrose density gradient analysis. Total cell membranes, rather than microsomes, were used as the source of membrane-bound ribosomes to eliminate potential losses during the preparation of microsomes. Bound ribosomes were assayed after quantitative release and recovery from total cell membranes using puromycin in the presence of high-salt buffer. Using this analysis, we demonstrate a 4.2-fold increase in RER in estrogen-treated male Xenopus laevis liver. Furthermore, we show that the ratio of the distribution of free to membrane-bound ribosomes in a nonsecretory cell line (HeLa) was 3.3, while this ratio in a secretory cell line (AR42J) was 1.2, indicating that cells active in secretion contain more RER. We suggest that this biochemical technique provides a simpler assay to detect changes in the size of the RER.

scholarly journals CReP mediates selective translation initiation at the endoplasmic reticulum

2020 ◽  
Vol 6 (23) ◽  
pp. eaba0745 ◽  
Author(s):  
Jonathan P. Kastan ◽  
Elena Y. Dobrikova ◽  
Jeffrey D. Bryant ◽  
Matthias Gromeier
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Synthesis ◽  
Translation Initiation ◽  
Stress Responses ◽  
Spatial Organization ◽  
Acute Stress ◽  
Cell Fractionation ◽  
Local Protein Synthesis ◽  
Eif2α Phosphorylation ◽  
Selective Translation

Eukaryotic protein synthesis control at multiple levels allows for dynamic, selective responses to diverse conditions, but spatial organization of translation initiation machinery as a regulatory principle has remained largely unexplored. Here we report on a role of constitutive repressor of eIF2α phosphorylation (CReP) in translation of poliovirus and the endoplasmic reticulum (ER)–resident chaperone binding immunoglobulin protein (BiP) at the ER. Functional, proximity-dependent labeling and cell fractionation studies revealed that CReP, through binding eIF2α, anchors translation initiation machinery at the ER and enables local protein synthesis in this compartment. This ER site was protected from the suppression of cytoplasmic protein synthesis by acute stress responses, e.g., phosphorylation of eIF2α(S51) or mTOR blockade. We propose that partitioning of translation initiation machinery at the ER enables cells to maintain active translation during stress conditions associated with global protein synthesis suppression.

scholarly journals Influenza virus hemagglutinin trimers and monomers maintain distinct biochemical modifications and intracellular distribution in brefeldin A-treated cells.

1991 ◽  
Vol 2 (7) ◽  
pp. 549-563 ◽  
Author(s):  
G Russ ◽  
J R Bennink ◽  
T Bächi ◽  
J W Yewdell
Keyword(s):  
Endoplasmic Reticulum ◽  
Influenza Virus ◽  
Monoclonal Antibodies ◽  
Golgi Complex ◽  
Brefeldin A ◽  
Retrograde Transport ◽  
Cell Fractionation ◽  
Influenza Virus Hemagglutinin ◽  
Infected Cells ◽  
Vesicular Compartment

Brefeldin A (BFA) induces the retrograde transport of proteins from the Golgi complex (GC) to the endoplasmic reticulum (ER). It is uncertain, however, whether the drug completely merges the ER with post-ER compartments, or whether some of their elements remain physically and functionally distinct. We investigated this question by the use of monoclonal antibodies specific for monomers and trimers of the influenza virus hemagglutinin (HA). In untreated influenza virus-infected cells, monomers and trimers almost exclusively partition into the ER and GC, respectively. In BFA-treated cells, both monomers and trimers are detected in the ER by immunofluorescence. Cell fractionation experiments indicate, however, that whereas HA monomers synthesized in the presence of BFA reside predominantly in vesicles with a characteristic density of the ER, HA trimers are primarily located in lighter vesicles characteristic of post-ER compartments. Biochemical experiments confirm that in BFA-treated cells, trimers are more extensively modified than monomers by GC-associated enzymes. Additional immunofluorescence experiments reveal that in BFA-treated cells, HA monomers can exist in an ER subcompartment less accessible to trimers and, conversely, that trimers are present in a vesicular compartment less accessible to monomers. These findings favor the existence of a post-ER compartment for which communication with the ER is maintained in the presence of BFA and suggest that trimers cycle between this compartment and the ER, but have access to only a portion of the ER.

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.

scholarly journals Oleic acid promotes the activation and translocation of phosphatidate phosphohydrolase from the cytosol to particulate fractions of isolated rat hepatocytes

1984 ◽  
Vol 219 (3) ◽  
pp. 911-916 ◽  
Author(s):  
C Cascales ◽  
E H Mangiapane ◽  
D N Brindley
Keyword(s):  
Fatty Acids ◽  
Endoplasmic Reticulum ◽  
Oleic Acid ◽  
Microsomal Fraction ◽  
Rat Hepatocytes ◽  
Total Activity ◽  
Cell Fractionation ◽  
Isolated Rat Hepatocytes ◽  
Phosphatidate Phosphohydrolase ◽  
Isolated Rat

The incubation of hepatocytes with 1-4mM-oleate increased the total activity of phosphatidate phosphohydrolase that was measured in the presence of Mg2+ to about 2-fold. This was accompanied by an increase in the proportion of the enzyme that was isolated with the particulate fractions. Conversely, the addition of up to 4mM-oleate decreased the recovery of phosphatidate phosphohydrolase in the cytosolic fraction from about 70% to 3% when hepatocytes were lysed with digitonin. Most of the increase in the membrane-associated phosphohydrolase activity was isolated after cell fractionation in the microsomal fraction that was enriched with the endoplasmic-reticulum marker arylesterase. It is proposed that the translocation of phosphatidate phosphohydrolase facilitates the increased synthesis of triacylglycerols in the liver when it is presented with an increased supply of fatty acids.

scholarly journals The fates of chicken nuclear lamin proteins during mitosis: evidence for a reversible redistribution of lamin B2 between inner nuclear membrane and elements of the endoplasmic reticulum.

1988 ◽  
Vol 107 (2) ◽  
pp. 397-406 ◽  
Author(s):  
R Stick ◽  
B Angres ◽  
C F Lehner ◽  
E A Nigg
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Membrane ◽  
Membrane Vesicles ◽  
Soluble Form ◽  
Lamin A ◽  
Cell Fractionation ◽  
Lamin B ◽  
Inner Nuclear Membrane ◽  
Nuclear Lamin ◽  
Mitotic Cells

In chicken, three structurally distinct nuclear lamin proteins have been described. According to their migration on two-dimensional gels, these proteins have been designated as lamins A, B1, and B2. To investigate the functional relationship between chicken lamins and their mammalian counterparts, we have examined here the state of individual chicken lamin proteins during mitosis. Current models proposing functional specializations of mammalian lamin subtypes are in fact largely based on the observation that during mitosis mammalian lamin B remains associated with membrane vesicles, whereas lamins A and C become freely soluble. Cell fractionation experiments combined with immunoblotting show that during mitosis both chicken lamins B1 and B2 remain associated with membranes, whereas lamin A exists in a soluble form. In situ immunoelectron microscopy carried out on mitotic cells also reveals membrane association of lamin B2, whereas the distribution of lamin A is random. From these results we conclude that both chicken lamins B1 and B2 may functionally resemble mammalian lamin B. Interestingly, immunolabeling of mitotic cells revealed an association of lamin B2 with extended membrane cisternae that resembled elements of the endoplasmic reticulum. Quantitatively, we found that all large endoplasmic reticulum-like membranes present in metaphase cells were decorated with lamin B2-specific antibodies. Given that labeling of these mitotic membranes was lower than labeling of interphase nuclear envelopes, it appears likely that during mitotic disassembly and reassembly of the nuclear envelope lamin B2 may reversibly distribute between the inner nuclear membrane and the endoplasmic reticulum.

scholarly journals Characterization of a gene product (Sec53p) required for protein assembly in the yeast endoplasmic reticulum.

1985 ◽  
Vol 101 (6) ◽  
pp. 2374-2382 ◽  
Author(s):  
M Bernstein ◽  
W Hoffmann ◽  
G Ammerer ◽  
R Schekman
Keyword(s):  
Endoplasmic Reticulum ◽  
Gene Fusion ◽  
Protein Assembly ◽  
Open Reading Frame ◽  
Cell Fractionation ◽  
Multicopy Plasmid ◽  
Wild Type ◽  
Cytosol Fraction ◽  
Reading Frame

SEC53, a gene that is required for completion of assembly of proteins in the endoplasmic reticulum in yeast, has been cloned, sequenced, and the product localized by cell fractionation. Complementation of a sec53 mutation is achieved with unique plasmids from genomic or cDNA expression banks. These inserts contain the authentic gene, a cloned copy of which integrates at the sec53 locus. An open reading frame in the insert predicts a 29-kD protein with no significant hydrophobic character. This prediction is confirmed by detection of a 28-kD protein overproduced in cells that carry SEC53 on a multicopy plasmid. To follow Sec53p more directly, a LacZ-SEC53 gene fusion has been constructed which allows the isolation of a hybrid protein for use in production of antibody. With such an antibody, quantitative immune decoration has shown that the sec53-6 mutation decreases the level of Sec53p at 37 degrees C, while levels comparable to wild-type are seen at 24 degrees C. An eightfold overproduction of Sec53p accompanies transformation of cells with a multicopy plasmid containing SEC53. Cell fractionation, performed with conditions that preserve the lumenal content of the endoplasmic reticulum (ER), shows Sec53p highly enriched in the cytosol fraction. We suggest that Sec53p acts indirectly to facilitate assembly in the ER, possibly by interacting with a stable ER component, or by providing a small molecule, other than an oligosaccharide precursor, necessary for the assembly event.

scholarly journals ER-misfolded proteins become sequestered with mitochondria and impair mitochondrial function

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Adrián Cortés Sanchón ◽  
Harshitha Santhosh Kumar ◽  
Matilde Mantovani ◽  
Ivan Osinnii ◽  
José María Mateos ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Synthesis ◽  
Mitochondrial Dysfunction ◽  
Mitochondrial Function ◽  
Human Disease ◽  
Misfolded Proteins ◽  
Cell Fractionation ◽  
Pathological Features

AbstractProteostasis is a challenge for cellular organisms, as all known protein synthesis machineries are error-prone. Here we show by cell fractionation and microscopy studies that misfolded proteins formed in the endoplasmic reticulum can become associated with and partly transported into mitochondria, resulting in impaired mitochondrial function. Blocking the endoplasmic reticulum-mitochondria encounter structure (ERMES), but not the mitochondrial sorting and assembly machinery (SAM) or the mitochondrial surveillance pathway components Msp1 and Vms1, abrogated mitochondrial sequestration of ER-misfolded proteins. We term this mitochondria-associated proteostatic mechanism for ER-misfolded proteins ERAMS (ER-associated mitochondrial sequestration). We testify to the relevance of this pathway by using mutant α-1-antitrypsin as an example of a human disease-related misfolded ER protein, and we hypothesize that ERAMS plays a role in pathological features such as mitochondrial dysfunction.

scholarly journals Selective recruitment of endoplasmic reticulum-targeted and cytosolic mRNAs into membrane-associated stress granules

2021 ◽  
Author(s):  
Jessica R Child ◽  
Qiang Chen ◽  
David W Reid ◽  
Sujatha Jagannathan ◽  
Christopher V Nicchitta
Keyword(s):  
Endoplasmic Reticulum ◽  
Translation Initiation ◽  
Nuclear Export ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Signal Sequence ◽  
Stress Granules ◽  
Cell Fractionation ◽  
Functional Link ◽  
Translational Inhibition

Stress granules (SGs) are membraneless organelles composed of mRNAs and RNA binding proteins which undergo assembly in response to stress-induced inactivation of translation initiation. The biochemical criteria for mRNA recruitment into SGs are largely unknown. In general, SG recruitment is limited to a subpopulation of a given mRNA species and RNA-seq analyses of purified SGs revealed that signal sequence-encoding (i.e. endoplasmic reticulum (ER)-targeted) transcripts are significantly under-represented, consistent with prior reports that ER-localized mRNAs are excluded from SGs. Using translational profiling, cell fractionation, and single molecule mRNA imaging, we examined SG biogenesis during the unfolded protein response (UPR) and report that UPR-elicited SG formation is gene selective. Combined immunofluorescence-smFISH studies demonstrated that UPR-induced mRNA granules co-localized with SG protein markers and were in close physical proximity to or directly associated with the ER membrane. mRNA recruitment into ER-associated SGs required stress-induced translational inhibition, though translational inhibition was not solely predictive of mRNA accumulation in SGs. SG formation in response to UPR activation or arsenite addition was blocked by the transcriptional inhibitors actinomycin D or triptolide, suggesting a functional link between gene transcriptional state and SG biogenesis. These data demonstrate that ER-targeted mRNAs can be recruited into SGs and identify the ER as a subcellular site of SG assembly. On the basis of the transcriptional inhibitor studies, we propose that newly transcribed mRNAs undergoing nuclear export during conditions of suppressed translation initiation are key substrates for SG biogenesis

scholarly journals mRNAs Encoding Polarity and Exocytosis Factors Are Cotransported with the Cortical Endoplasmic Reticulum to the Incipient Bud in Saccharomyces cerevisiae

2007 ◽  
Vol 27 (9) ◽  
pp. 3441-3455 ◽  
Author(s):  
Stella Aronov ◽  
Rita Gelin-Licht ◽  
Gadi Zipor ◽  
Liora Haim ◽  
Einat Safran ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Endoplasmic Reticulum ◽  
Nuclear Division ◽  
Mrna Localization ◽  
Dependent Manner ◽  
Protein Enrichment ◽  
Bud Emergence ◽  
Bud Site ◽  
Cortical Endoplasmic Reticulum ◽  
Asymmetrically Distributed

ABSTRACT Polarized growth in the budding yeast Saccharomyces cerevisiae depends upon the asymmetric localization and enrichment of polarity and secretion factors at the membrane prior to budding. We examined how these factors (i.e., Cdc42, Sec4, and Sro7) reach the bud site and found that their respective mRNAs localize to the tip of the incipient bud prior to nuclear division. Asymmetric mRNA localization depends upon factors that facilitate ASH1 mRNA localization (e.g., the 3′ untranslated region, She proteins 1 to 5, Puf6, actin cytoskeleton, and a physical association with She2). mRNA placement precedes protein enrichment and subsequent bud emergence, implying that mRNA localization contributes to polarization. Correspondingly, mRNAs encoding proteins which are not asymmetrically distributed (i.e., Snc1, Mso1, Tub1, Pex3, and Oxa1) are not polarized. Finally, mutations which affect cortical endoplasmic reticulum (ER) entry and anchoring in the bud (myo4Δ, sec3Δ, and srp101) also affect asymmetric mRNA localization. Bud-localized mRNAs, including ASH1, were found to cofractionate with ER microsomes in a She2- and Sec3-dependent manner; thus, asymmetric mRNA transport and cortical ER inheritance are connected processes in yeast.

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