共查询到20条相似文献,搜索用时 15 毫秒
1.
A membrane preparation that contains proteins characteristic of the rough endoplasmic reticulum 总被引:1,自引:0,他引:1
A Amar-Costesec M Hortsch C Turu 《Biology of the cell / under the auspices of the European Cell Biology Organization》1988,62(3):281-288
We describe a procedure for disassembling rat liver rough microsomes, which allows the purification of the rough endoplasmic reticulum (ER) membrane. Membrane-bound ribosomes and adsorbed proteins are first detached by washing rough microsomes with 5 mM Na-pyrophosphate. In a second step, the vesicle membrane is opened by digitonin, with concomitant release of the luminal content. The purification is monitored at each step by electron microscopy, and by assaying chemical constituents (protein, phospholipid, RNA) and marker enzymes for the main subcellular organelles. The final membrane preparation is representative of the ER, since it contains 24.1% of the liver glucose 6-phosphatase with a relative specific activity of 14.2. Contaminants represent less than 5% of its protein content. SDS-polyacrylamide gel electrophoresis, followed by immunoblot analysis, reveals that the ribophorins I and II, two established markers of the rough (d) domain are still present in the final membrane preparation. It also contains the docking protein (or signal recognition particle receptor) and protein disulfide isomerase, and has conserved the functional capacity to remove co- and post-translationally the signal peptide of pre-secretory proteins. The membrane preparation is suitable for studies on the polypeptide composition of the d domain. 相似文献
2.
TorsinA is a membrane-associated enzyme in the endoplasmic reticulum (ER) lumen that is mutated in DYT1 dystonia. How it remains in the ER has been unclear. We report that a hydrophobic N-terminal domain (NTD) directs static retention of torsinA within the ER by excluding it from ER exit sites, as has been previously reported for short transmembrane domains (TMDs). We show that despite the NTD's physicochemical similarity to TMDs, it does not traverse the membrane, defining torsinA as a lumenal monotopic membrane protein and requiring a new paradigm to explain retention. ER retention and membrane association are perturbed by a subset of nonconservative mutations to the NTD, suggesting that a helical structure with defined orientation in the membrane is required. TorsinA preferentially enriches in ER sheets, as might be expected for a lumenal monotopic membrane protein. We propose that the principle of membrane-based protein sorting extends to monotopic membrane proteins, and identify other proteins including the monotopic lumenal enzyme cyclooxygenase 1 (prostaglandin H synthase 1) that share this mechanism of retention with torsinA. 相似文献
3.
Prinz WA Grzyb L Veenhuis M Kahana JA Silver PA Rapoport TA 《The Journal of cell biology》2000,150(3):461-474
We find that the peripheral ER in Saccharomyces cerevisiae forms a dynamic network of interconnecting membrane tubules throughout the cell cycle, similar to the ER in higher eukaryotes. Maintenance of this network does not require microtubule or actin filaments, but its dynamic behavior is largely dependent on the actin cytoskeleton. We isolated three conditional mutants that disrupt peripheral ER structure. One has a mutation in a component of the COPI coat complex, which is required for vesicle budding. This mutant has a partial defect in ER segregation into daughter cells and disorganized ER in mother cells. A similar phenotype was found in other mutants with defects in vesicular trafficking between ER and Golgi complex, but not in mutants blocked at later steps in the secretory pathway. The other two mutants found in the screen have defects in the signal recognition particle (SRP) receptor. This receptor, along with SRP, targets ribosome-nascent chain complexes to the ER membrane for protein translocation. A conditional mutation in SRP also disrupts ER structure, but other mutants with translocation defects do not. We also demonstrate that, both in wild-type and mutant cells, the ER and mitochondria partially coalign, and that mutations that disrupt ER structure also affect mitochondrial structure. Our data suggest that both trafficking between the ER and Golgi complex and ribosome targeting are important for maintaining ER structure, and that proper ER structure may be required to maintain mitochondrial structure. 相似文献
4.
5.
Ion channel biogenesis involves an intricate interplay between subunit folding and assembly. Channel stoichiometries vary and give rise to diverse functions, which impacts on neuronal signalling. AMPA glutamate receptor (AMPAR) assembly is modulated by RNA processing. Here, we provide mechanistic insight into this process. First, we show that a single alternatively spliced residue within the ligand-binding domain alters AMPAR secretion from the ER. Local contacts differ between Leu758 of the GluR2-flop splice form as compared with the flip-specific Val758, which is transmitted globally to alter resensitization kinetics. Detailed biochemical and functional analysis of mutants suggest that AMPARs sample the gating cascade prior to ER export. Irreversibly locking the receptor within various states of the cascade severely attenuates ER transit. Alternative RNA processing by contrast, shifts equilibria between transition states reversibly and thereby modulates secretion kinetics. These data reveal how RNA processing tunes AMPAR biogenesis, and imply that gating transitions in the ER determine iGluR secretory traffic. 相似文献
6.
Summary We have developed a novel, “in situ” translation system derived from cultured cells that are subject to mild detergent extraction.
By using a low concentration of nonionic detergent to gently permeabilize cells while they remain adherent to a substrate,
cytoskeletal frameworks are obtained that are devoid of membraneous barriers yet retain much the same topological arrangement
of mRNA, ribosomes and cytostructure that exists “in vivo”. Data indicate that when these cytoskeletal frameworks are supported
by a ribosome-depleted, nuclease-treated, reticulocyte lysate supernatant, they are capable of resuming translation of their
attached polysomes for at least 40 minutes. Emulsion autoradiography of ongoing protein synthesis demonstrates that protein
synthetic activity is ubiquitous throughout the population of extracted cells, and not confined to a less well-extracted subset.
Computer-assisted, two-dimensional gel analysis reveals that the pattern of proteins produced by such extracted cells is approximately
70% coincident with that produced by unextracted cells, including proteins of molecular weight as great as 200 kilodaltons.
Furthermore, a continued increase in intensity of almost all proteins during the first 40 minutes of translation suggests
that translational re-initiation, in addition to polysome run-off, is also taking place. Collectively, these findings indicate
that much of the translational machinery remains both intact and competant in this cytoskeletal-based translation system.
As such, this system should prove extremely useful in identifying molecular factors operant during certain types of translation
control and in further examining the role played by the cytoskeleton in regulating gene expression.
This work was supported by grants from the American Cancer Society (#NP-683) and from the University of Connecticut Health
Center Research Foundation. 相似文献
7.
Nogalska A Engel WK McFerrin J Kokame K Komano H Askanas V 《Journal of neurochemistry》2006,96(5):1491-1499
Herp is a stress-response protein localized in the endoplasmic reticulum (ER) membrane. Herp was proposed to improve ER-folding, decrease ER protein load, and participate in ER-associated degradation (ERAD). Intra-muscle-fiber ubiquitinated multiprotein-aggregates containing, among other proteins, either amyloid-beta (Abeta) or phosphorylated tau are characteristic of sporadic inclusion-body myositis (s-IBM). ER stress and proteasome inhibition appear to play a role in s-IBM pathogenesis. We have now studied Herp in s-IBM muscle fibers and in ER-stress-induced or proteasome-inhibited cultured human muscle fibers. In s-IBM muscle fibers: (i) Herp was strongly immunoreactive in the form of aggregates, which co-localized with Abeta, GRP78, and beta2 proteasome subunit; (ii) Herp mRNA and protein were increased. In ER-stress-induced cultured human muscle fibers: (i) Herp immunoreactivity was diffusely increased; (ii) Herp mRNA and protein were increased. In proteasome-inhibited cultured human muscle fibers: (i) Herp immunoreactivity was in the form of aggregates; (ii) Herp protein was increased, but its mRNA was not. Accordingly, in s-IBM muscle fibers: (i) increase of Herp might be due to both ER-stress and proteasome inhibition; (ii) co-localization of Herp with Abeta, proteasome, and ER-chaperone GRP78 could reflect its possible role in processing and degradation of cytotoxic proteins in ER. 相似文献
8.
《Molecular membrane biology》2013,30(3):283-288
The entry of substrates into, and the export of glururonides from, the lumen of hepatic endoplasmic reticulum (ER) in vitro (sealed microsomes) has been measured using radioactivity-labelled materials and a rapid filtration assay. Analysis of liver microsomes from a jaundiced patient showed the accumulation of bilirubin glucuronides within the lumen of the ER. Further analysis of these hepatic microsomes revealed that newly synthesized 1-naphthol glucuronide could exit from the microsomes whereas billrubin glucuronide was accumulated within the microsomes. These results suggest the existence of mechanisms for the sorting of small molecules, destined for export through bile canalicular or basolateral plasma membranes, by ER. Furthermore, these sorting processes may be regulated by specific transporters within the ER. 相似文献
9.
10.
Summary The nuclear-associated endoplasmic reticulum of L-929 cells was found to contain the highest amount of labeled phosphatidylcholine
after a 60 min incubation with14C-choline. Radioactivity was otherwise distributed relatively evenly among other membrane-containing organelles (nuclei, mitochondria,
plasma membranes and endoplasmic reticulum membranes). During a 120 min chase following removal of isotope and addition of
cold choline chloride, there was a considerable reduction in labeled phosphatidylcholine in the NER and nuclei. The decrease
in radioactivity in these fractions was matched by an almost identical increase in the fraction containing mitochondria and
plasma membranes. Separation of mitochondria and plasma membranes by centrifugation on discontinuous gradients showed that14C-choline labeled phosphatidylcholine appeared most rapidly in the plasma membranes. The results indicate that phospholipid
molecules migrate within a short period of time from their site of synthesis in the NER to plasma membranes. 相似文献
11.
Summary Intracellular insulin-binding sites were directly traced in fixed monolayer cultures of a variety of cell types with the use of two fluorescent derivatives of insulin, viz. fluorescein isothiocyanate (FITC)-labelled and tetramethyl rhodamine isothiocyanate (TMRITC)-labelled insulin. Both derivatives retained the property of stimulating DNA synthesis in fibroblasts. Insulin-binding sites were found in the nuclear envelope, nucleoplasm, nucleoli, and in mitochondria and rough endoplasmic reticulum. The identity of these structures was established by concomitant studies on the same cell by means of phase contrast optics and immunocytochemical tracing with specific antibodies to nuclei, mitochondria, or ribosomes. Binding of insulin to the nuclear and cytoplasmic structures was rapid, reversible and saturable, temperature and pH-dependent, and inhibited by an excess of native, but not other, hormones. The staining reactions were sensitive to treatment by the nonionic detergents, NP-40 and TX-100, and to trypsin and pronase, but not to DNase and RNase, suggesting that the binding sites are protein in nature.Supported by a grant from the Anti-Cancer Council of Victoria. We thank Mrs. I. Burns for technical assistance, Dr. H.A. Ward and staff for preparation of the conjugated insulins, and Prof. R.C. Nairn for advice 相似文献
12.
Topology of molecular machines of the endoplasmic reticulum: a compilation of proteomics and cytological data 总被引:1,自引:0,他引:1
The endoplasmic reticulum (ER) is a key organelle of the secretion pathway involved in the synthesis of both proteins and
lipids destined for multiple sites within and without the cell. The ER functions to both co- and post-translationally modify
newly synthesized proteins and lipids and sort them for housekeeping within the ER and for transport to their sites of function
away from the ER. In addition, the ER is involved in the metabolism and degradation of specific xenobiotics and endogenous
biosynthetic products. A variety of proteomics studies have been reported on different subcompartments of the ER providing
an ER protein dictionary with new data being made available on many protein complexes of relevance to the biology of the ER
including the ribosome, the translocon, coatomer proteins, cytoskeletal proteins, folding proteins, the antigen-processing
machinery, signaling proteins and proteins involved in membrane traffic. This review examines proteomics and cytological data
in support of the presence of specific molecular machines at specific sites or subcompartments of the ER. 相似文献
13.
Tim Brac 《Tissue & cell》1984,16(6):859-871
The distribution of microinjected ferritin, ranging in charge from anionic to highly cationic, has been used to indicate differences in surface charge on the rough endoplasmic reticulum and the Golgi complex of intact cells. Highly cationic ferritins (HCF)(HCF1, pI 7.9-9.1; HCF2, pI 8.5-9.4; and HCF3.pI 9.5-10.1) were mostly bound and caused swelling of the rough endoplasmic reticulum. Cationic ferritin (CF) (pI 7.0-8.0) and anionic ferritin (AF) (pI 4.0-4.4) caused no changes in morphology. The distribution of these ferritins in the cytoplasmic space varied with their charge. Significantly more CF was bound to surfaces than was found in the free cytoplasmic space. Conversely, there was significantly more AF in the free cytoplasmic space than close to surfaces. Therefore, the intracellular surfaces are negatively charged. Comparison of the structures in the secretory pathway showed no differences in ferritin binding to transition vesicles, rough endoplasmic reticulum, Golgi saccules or secretory vesicles. The Golgi complex beads are not distinguished by their charge. It is therefore unlikely that charge differences play a role in regulating membrane-membrane interactions in this region of the secretory pathway. 相似文献
14.
Exiting the endoplasmic reticulum 总被引:6,自引:2,他引:4
Vesicular transport from the endoplasmic reticulum (ER) to the Golgi complex constitutes the initial step in protein secretion. COPII-coated vesicles mediate the export of newly synthesized proteins from the ER, and this transport step is coupled with COPI-mediated retrograde traffic to form a transport circuit that supports the compositional asymmetry of the ER-Golgi system. Biochemical and structural studies have advanced our understanding of the mechanisms that control vesicle formation and cargo-protein capture. Recent work has highlighted the function of transitional ER regions in specifying the location of COPII budding. 相似文献
15.
Summary In the albino rabbit the sclera is composed of (a) collagen fibrils arranged in fibers, (b) interposed elastic fibers and (c) fibroblasts. The diameter of collagen fibrils and fibers increases from the internal toward the external surface of the sclera. In the same direction the number of elastic fibers and fibroblasts decreases. A peculiar structure is found in the rough surfaced endoplasmic reticulum of the fibroblasts in the innermost portions of the sclera. The nature of this structure is discussed.This investigation was supported by Deutsche Forschungsgemeinschaft Training Grant SP 102/1 and by Research to Prevent Blindness, Inc., 598 Madison Avenue, New York N.Y. 10022. 相似文献
16.
Kevin J. Eckelbarger 《Tissue & cell》1982,14(2):289-295
Peculiar undulating cisternae of endoplasmic reticulum have been observed in the spermatids of the opisthobranch mollusc Spurilla neapolitana. Analysis of sections suggests that these arrays of ER might be a multilamellar structure consisting of paired cytomembranes molded into parallel, conical elevations with hexagonal bases. The structure is associated most frequently with the Golgi complex of the spermatid but its function is unknown. Other reports of similar arrays of ER in both plant and animal cells are discussed and compared with those of Spurilla spermatids. 相似文献
17.
Dogic D Dubois A de Chassey B Lefkir Y Letourneur F 《European journal of cell biology》2001,80(2):151-155
Studies on the ERGIC-53 KKAA signal have revealed a new mechanism for static retention of mammalian proteins in the endoplasmic reticulum (Andersson, H., Kappeler, F., Hauri, H. P. (1999): Protein targeting to endoplasmic reticulum by dilysine signals involves direct retention in addition to retrieval. J. Biol. Chem. 274,15080 - 15084). To test if this mechanism was conserved in yeast, the ERGIC-53 KKAA signal was transferred on two different yeast reporter proteins. Making use of a genetic assay, we demonstrate that this signal induces COPI-dependent ER retrieval. ER retention of KKAA-tagged proteins was impaired in yeast mutants affected in COPI subunits. Furthermore, biochemical analysis of post-ER carbohydrate modifications detected on reporter proteins indicated that KKAA-tagged proteins recycle continuously within early compartments of the secretory pathway. Therefore in yeast, the KKAA signal might only function as a classical dilysine ER retrieval signal. 相似文献
18.
Peter Verani
Nada Pipan 《Biology of the cell / under the auspices of the European Cell Biology Organization》1995,83(1):69-76
Summary— Zebrafish hepatocytes respond to stimulation with estradiol 17β (E2) with an extreme enlargement of the endomembrane system, especially the endoplasmic reticulum (ER), and when stimulation is stopped with a rapid degradation of enlarged endomembranes. Two pathways for degradation of ER were studied: a) the autophagy which was evaluated by stereological measurement; and b) the activity of cytosolic phospholipase B (PL-B) measured by a titration method. After a 30-day treatment with E2 a six-fold increase of the surface density of ER was accompanied by an increase of both autophagy and PL-B activity. 2 days after stopping the stimulation with E2 the ER vesiculated and its surface density decreased to the half value. Interestingly, at the same time autophagic vacuoles (AV) almost disappeared from hepatocytes, while the activity of PL-B reached its maximum at which it persisted for a further 4 days. After 4–6 days without E2 the cistern of ER became flattened again and new AVs reappeared. The data suggest that the regulation mechanisms of endomembrane degradation by PL-B and autophagy do not depend on each other and also that the appearance of AV is strongly related to the shape of ER. 相似文献
19.
Catherine Amaya Christopher J.F. Cameron Swapnil C. Devarkar Sebastian J.H. Seager Mark B. Gerstein Yong Xiong Christian Schlieker 《The Journal of biological chemistry》2021,297(2)
The endoplasmic reticulum (ER) is a membrane-bound organelle responsible for protein folding, lipid synthesis, and calcium homeostasis. Maintenance of ER structural integrity is crucial for proper function, but much remains to be learned about the molecular players involved. To identify proteins that support the structure of the ER, we performed a proteomic screen and identified nodal modulator (NOMO), a widely conserved type I transmembrane protein of unknown function, with three nearly identical orthologs specified in the human genome. We found that overexpression of NOMO1 imposes a sheet morphology on the ER, whereas depletion of NOMO1 and its orthologs causes a collapse of ER morphology concomitant with the formation of membrane-delineated holes in the ER network positive for the lysosomal marker lysosomal-associated protein 1. In addition, the levels of key players of autophagy including microtubule-associated protein light chain 3 and autophagy cargo receptor p62/sequestosome 1 strongly increase upon NOMO depletion. In vitro reconstitution of NOMO1 revealed a “beads on a string” structure likely representing consecutive immunoglobulin-like domains. Extending NOMO1 by insertion of additional immunoglobulin folds results in a correlative increase in the ER intermembrane distance. Based on these observations and a genetic epistasis analysis including the known ER-shaping proteins Atlastin2 and Climp63, we propose a role for NOMO1 in the functional network of ER-shaping proteins. 相似文献
20.
Expression of the canine 180-kDa ribosome receptor p180 in yeast induces the synthesis of RER, and increases the mRNAs of secretory pathway proteins, and protein secretion. To assess whether p180 is a master regulator of cell secretion in mammalian cells, we stably expressed red fluorescent forms of the human p180 variants p180DeltaR (no tandem repeats), p180R (26 repeats), and full-length p180FR (54 repeats) containing different lengths of the tandem repeat ribosome-binding domain in rat pancreatic RINm5F islet beta-cells. All three fluorescent p180 variants localized exclusively to the RER. Cells transfected with p180R were filled with ribosome-studded karmellae, whereas p180DeltaR and p180FR transfectants contained only increased amounts of mostly smooth ER. Unlike in yeast, over-expression of p180R failed to increase the secretory pathway proteins calnexin, SEC61beta, and calreticulin, or ribosome biogenesis. The data suggest that alternative splicing of the p180 tandem repeat domain is a means of regulating the ribosome-binding activity of p180, and potentially the secretory activity of the cell. However, p180 is not a master regulator of mammalian cell secretion as it does not concomitantly trigger the synthesis of protein machinery required to enhance protein synthesis and cell secretion. 相似文献