scholarly journals The translocation, folding, assembly and redox-dependent degradation of secretory and membrane proteins in semi-permeabilized mammalian cells

1995 ◽  
Vol 307 (3) ◽  
pp. 679-687 ◽  
Author(s):  
R Wilson ◽  
A J Allen ◽  
J Oliver ◽  
J L Brookman ◽  
S High ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Intact Cell ◽  
Cell System ◽  
In Vitro Translation ◽  
Tissue Type ◽  
Translation System ◽  
Secretory Proteins ◽  
Permeabilized Cell ◽  
Permeabilized Cells

We describe here a semi-permeabilized cell-system which reconstitutes the efficient synthesis, translocation, folding, assembly and degradation of membrane and secretory proteins. Cells grown in culture were treated with the detergent digitonin which selectively permeabilized the plasma membrane leaving the cellular organelles, such as the endoplasmic reticulum (ER) and trans-Golgi network intact. These permeabilized cells were added to an in vitro translation system, either wheatgerm or reticulocyte lysate, supplemented with RNA coding for either membrane or secretory proteins. Efficient translocation and modification of proteins by these cells was demonstrated by protease protection, photocross-linking of nascent chains to components of the translocation apparatus and by post-translational modifications such as glycosylation or hydroxylation. A comparison was made between the ability of semi-permeabilized cells and microsomal vesicles to fold and assemble proteins. The results show that the intact ER within these cells can assemble proteins much more efficiently than vesicularized ER. Furthermore, the semi-permeabilized cells carried out the redox-dependent degradation of tissue-type plasminogen activator. This system has all the advantages of conventional cell-free systems, including speed and, importantly, the ability to manipulate the components of the assay, while retaining intracellular organelles and, therefore, allowing cellular processes to occur as they would in the intact cell.

scholarly journals Calnexin and calreticulin bind to enzymically active tissue-type plasminogen activator during biosynthesis and are not required for folding to the native conformation

1997 ◽  
Vol 328 (1) ◽  
pp. 113-119 ◽  
Author(s):  
Simon ALLEN ◽  
J. Neil BULLEID
Keyword(s):  
Plasminogen Activator ◽  
Intact Cell ◽  
In Vitro Translation ◽  
Tissue Type ◽  
Translation System ◽  
Native Conformation ◽  
Tissue Type Plasminogen Activator ◽  
Permeabilized Cells ◽  
Type Plasminogen Activator

The roles of the endoplasmic-reticulum lectins calnexin and calreticulin in the folding of tissue-type plasminogen activator (tPA) have been investigated using an in vitro translation system that reconstitutes these processes as they would occur in the intact cell. Using co-immunoprecipitation of newly synthesized tPA with antibodies to calnexin and calreticulin, it was demonstrated that the interaction of tPA with both lectins was dependent upon tPA glycosylation and glucosidase trimming. When tPA was synthesized in the presence of semi-permeabilized cells under conditions preventing complex formation with calnexin and calreticulin, the translation product had a specific plasminogenolytic activity identical with that when synthesized under conditions permitting interactions with both lectins. Furthermore, complexes of tPA bound to calnexin and calreticulin were shown to be enzymically active. These results demonstrate that calnexin and calreticulin can form a stable interaction with correctly folded tPA; however, such interactions are not required for the synthesis of enzymically active tPA.

scholarly journals An efficient in vitro translation system from mammalian cells lacking the translational inhibition caused by eIF2 phosphorylation

RNA ◽  
2008 ◽  
Vol 14 (3) ◽  
pp. 593-602 ◽  
Author(s):  
V. V. Zeenko ◽  
C. Wang ◽  
M. Majumder ◽  
A. A. Komar ◽  
M. D. Snider ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
In Vitro Translation ◽  
Translation System ◽  
Translational Inhibition ◽  
Eif2 Phosphorylation

Structural and functional similarities between the central eukaryotic initiation factor (eIF)4A-binding domain of mammalian eIF4G and the eIF4A-binding domain of yeast eIF4G

2001 ◽  
Vol 355 (1) ◽  
pp. 223-230 ◽  
Author(s):  
Diana DOMINGUEZ ◽  
Elisabeth KISLIG ◽  
Michael ALTMANN ◽  
Hans TRACHSEL
Keyword(s):  
Amino Acid ◽  
Binding Site ◽  
Mammalian Cells ◽  
Amino Acid Level ◽  
Binding Domain ◽  
In Vitro Translation ◽  
Initiation Factor ◽  
Translation System ◽  
Eukaryotic Initiation Factor

The translation eukaryotic initiation factor (eIF)4G of the yeast Saccharomyces cerevisiae interacts with the RNA helicase eIF4A (a member of the DEAD-box protein family; where DEAD corresponds to Asp-Glu-Ala-Asp) through a C-terminal domain in eIF4G (amino acids 542–883). Mammalian eIF4G has two interaction domains for eIF4A, a central domain and a domain close to the C-terminus. This raises the question of whether eIF4A binding to eIF4G is conserved between yeast and mammalian cells or whether it is different. We isolated eIF4G1 mutants defective in eIF4A binding and showed that these mutants are strongly impaired in translation and growth. Extracts from mutants displaying a temperature-sensitive phenotype for growth have low in vitro translation activity, which can be restored by addition of the purified eIF4G1–eIF4E complex, but not by eIF4E alone. Analysis of mutant eIF4G542–883 proteins defective in eIF4A binding shows that the interaction of yeast eIF4A with eIF4G1 depends on amino acid motifs that are conserved between the yeast eIF4A-binding site and the central eIF4A-binding domain of mammalian eIF4G. We show that mammalian eIF4A binds tightly to yeast eIF4G1 and, furthermore, that mutant yeast eIF4G542–883 proteins, which do not bind yeast eIF4A, do not interact with mammalian eIF4A. Despite the conservation of the eIF4A-binding site in eIF4G and the strong sequence conservation between yeast and mammalian eIF4A (66% identity; 82% similarity at the amino acid level) mammalian eIF4A does not substitute for the yeast factor in vivo and is not functional in a yeast in vitro translation system.

Docking of chromaffin granules—A necessary step in exocytosis?

1987 ◽  
Vol 7 (4) ◽  
pp. 269-279 ◽  
Author(s):  
Theo Schäfer ◽  
Urs O. Karli ◽  
Felix E. Schweizer ◽  
Max M. Burger
Keyword(s):  
Plasma Membrane ◽  
Chromaffin Cells ◽  
Cell Types ◽  
Cell System ◽  
Secretory Vesicles ◽  
Chromaffin Granules ◽  
Permeabilized Cell ◽  
Permeabilized Cells ◽  
Pc 12 Cells

Putative docking of secretory vesicles comprising recognition of and attachment to future fusion sites in the plasma membrane has been investigated in chromaffin cells of the bovine adrenal medulla and in rat phaeochromocytoma (PC 12) cells. Upon permeabilization with digitonin, secretion can be stimulated in both cell types by indreasing the free Ca2+-concentration to μM levels. Secretory activity can be elicited up to 1 hr after starting permeabilization and despite the loss of soluble cytoplasmic components indicating a stable attachment of granules to the plasma membrane awaiting the trigger for fusion. Docked granules can be observed in the electron microscope in permeabilized PC 12 cells which contain a large proportion of their granules aligned underneath the plasma membrane. The population of putatively docked granules in chromaffin cells cannot be as readily discerned due to the dispersal of granules throughout the cytoplasm. Further experiments comparing PC 12 and chromaffin cells suggest that active docking but not transport of granules can still be performed by permeabilized cells in the presence of Ca2+: a short (2 min) pulse of Ca2+ in PC 12 cells leads to the secretion of almost all releasable hormone over a 15 min observation period whereas, in chromaffin cells, with only a small proportion of granules docked, withdrawal of Ca2+ leads to an immediate halt in secretion. Transport of chromaffin granules from the Golgi to the plasma membrane docking sites seems to depend on a mechanism sensitive to permeabilization. This is shown by the difference in the amount of hormone released from the two permeabilized cell types, reflecting the contrast in the proportion of granules docked to the plasma membrane in PC 12 or chromaffin cells. Neither docking nor the docked state are influenced by cytochalasine B or colchicine. The permeabilized cell system is a valuable technique for the in vitro study of interaction between secretory vesicles and their target membrane.

scholarly journals PLA2 activity is required for nuclear shrinkage in caspase-independent cell death

2003 ◽  
Vol 163 (6) ◽  
pp. 1219-1230 ◽  
Author(s):  
Koei Shinzawa ◽  
Yoshihide Tsujimoto
Keyword(s):  
Cell Death ◽  
Morphological Changes ◽  
Chromatin Condensation ◽  
Cell System ◽  
Hypoxic Cell ◽  
Pla2 Activity ◽  
Permeabilized Cell ◽  
In Vitro System ◽  
Permeabilized Cells

Apoptosis is defined on the basis of morphological changes like nuclear fragmentation and chromatin condensation, which are dependent on caspases. Many forms of caspase-independent cell death have been reported, but the mechanisms are still poorly understood. We found that hypoxic cell death was independent of caspases and was associated with significant nuclear shrinkage. Neither Bcl-2 nor Apaf-1 deficiency prevented hypoxic nuclear shrinkage. To understand the molecular mechanism of the nuclear shrinkage, we developed an in vitro system using permeabilized cells, which allowed us to purify a novel member of the phospholipase A2 (PLA2) family that induced nuclear shrinkage. Purified PLA2 induced nuclear shrinkage in our permeabilized cell system. PLA2 inhibitors prevented hypoxic nuclear shrinkage in cells and cell death. Hypoxia caused elevation of PLA2 activity and translocation of intracellular PLA2s to the nucleus. Knockdown of the Ca2+-independent PLA2 delayed nuclear shrinkage and cell death. These results indicate that Ca2+-independent PLA2 is crucial for a caspase-independent cell death signaling pathway leading to nuclear shrinkage.

scholarly journals Development of a tRNA-dependent in vitro translation system

RNA ◽  
2001 ◽  
Vol 7 (5) ◽  
pp. 765-773 ◽  
Author(s):  
RICHARD J. JACKSON ◽  
SAWSAN NAPTHINE ◽  
IAN BRIERLEY
Keyword(s):  
In Vitro Translation ◽  
Translation System

scholarly journals Arabidopsis Cell-free Extract, ACE, a New In Vitro Translation System Derived from Arabidopsis Callus Cultures

2012 ◽  
Vol 53 (3) ◽  
pp. 602-602
Author(s):  
K. Murota ◽  
Y. Hagiwara-Komoda ◽  
K. Komoda ◽  
H. Onouchi ◽  
M. Ishikawa ◽  
...  
Keyword(s):  
Callus Cultures ◽  
In Vitro Translation ◽  
Translation System ◽  
Cell Free Extract ◽  
Arabidopsis Callus

four-jointed is required for intermediate growth in the proximal-distal axis in Drosophila

Development ◽  
1995 ◽  
Vol 121 (9) ◽  
pp. 2767-2777 ◽  
Author(s):  
J.L. Villano ◽  
F.N. Katz
Keyword(s):  
Optic Lobe ◽  
Regional Growth ◽  
Positional Information ◽  
In Vitro Translation ◽  
Translation System ◽  
Regional Pattern ◽  
Microsomal Membranes ◽  
Position Sensitive ◽  
Coordination Function

Genes capable of translating positional information into regulated growth lie at the heart of morphogenesis, yet few genes with this function have been identified. Mutants in the Drosophila four-jointed (fj) gene show reduced growth and altered differentiation only within restricted sectors of the proximal-distal (PD) axis in the leg and wing, thus fj is a candidate for a gene with this coordination function. Consistent with a position-sensitive role, we show that fj is expressed in a regional pattern in the developing leg, wing, eye and optic lobe. The fj gene encodes a novel type II membrane glycoprotein. When the cDNA is translated in an in vitro translation system in the presence of exogenous microsomal membranes, the intralumenal portion of some of the molecules is cleaved, yielding a secreted C-terminal fragment. We propose that fj encodes a secreted signal that functions as a positive regulator of regional growth and differentiation along the PD axis of the imaginal discs.

scholarly journals A permeabilized cell system identifies the endoplasmic reticulum as a site of protein degradation.

1991 ◽  
Vol 115 (5) ◽  
pp. 1225-1236 ◽  
Author(s):  
F J Stafford ◽  
J S Bonifacino
Keyword(s):  
Protein Degradation ◽  
Secretory Pathway ◽  
Fibroblast Cell ◽  
Cell System ◽  
Current Evidence ◽  
Permeabilized Cell ◽  
Intact Cells ◽  
Permeabilized Cells ◽  
Streptolysin O ◽  
A Site

Analysis of the fate of a variety of newly synthesized proteins in the secretory pathway has provided evidence for the existence of a novel protein degradation system distinct from that of the lysosome. Although current evidence suggests that proteins degraded by this system are localized to a pre-Golgi compartment before degradation, the site of proteolysis has not been determined. A permeabilized cell system was developed to examine whether degradation by this pathway required transport out of the ER, and to define the biochemical characteristics of this process. Studies were performed on fibroblast cell lines expressing proteins known to be sensitive substrates for this degradative process, such as the chimeric integral membrane proteins, Tac-TCR alpha and Tac-TCR beta. By immunofluorescence microscopy, these proteins were found to be localized to the ER. Treatment with cycloheximide resulted in the progressive disappearance of intracellular staining without change in the ER localization of the chimeric proteins. Cells permeabilized with the pore-forming toxin streptolysin O were able to degrade these newly synthesized proteins. The protein degradation seen in permeabilized cells was representative of that seen in intact cells, as judged by the similar speed of degradation, substrate selectivity, temperature dependence, and involvement of free sulfhydryl groups. Degradation of these proteins in permeabilized cells took place in the absence of transport between the ER and the Golgi system. Moreover, degradation occurred in the absence of added ATP or cytosol, and in the presence of apyrase, GTP gamma S, or EDTA; i.e., under conditions which prevent transport of proteins out of the ER. The efficiency and selectivity of degradation of newly synthesized proteins were also conserved in an isolated ER fraction. These data indicate that the machinery responsible for pre-Golgi degradation of newly synthesized proteins exists within the ER itself, and can operate independent of exogenously added ATP and cytosolic factors.

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