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  • Rockefeller University Press  (7)
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  • Rockefeller University Press  (7)
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  • 1
    Online Resource
    Online Resource
    Rockefeller University Press ; 1989
    In:  The Journal of cell biology Vol. 109, No. 1 ( 1989-07-01), p. 61-72
    In: The Journal of cell biology, Rockefeller University Press, Vol. 109, No. 1 ( 1989-07-01), p. 61-72
    Abstract: Brefeldin A (BFA) has been reported to block protein transport from the ER and cause disassembly of the Golgi complex. We have examined the effects of BFA on the transport and processing of the vesicular stomatitis virus G protein, a model integral membrane protein. Delivery of G protein to the cell surface was reversibly blocked by 6 micrograms/ml BFA. Pulse-label experiments revealed that in the presence of BFA, G protein became completely resistant to endoglycosidase H digestion. Addition of sialic acid, a trans-Golgi event, was not observed. Despite processing by cis- and medial Golgi enzymes, G protein was localized by indirect immunofluorescence to a reticular distribution characteristic of the ER. By preventing transport of G protein from the ER with the metabolic inhibitor carbonyl cyanide m-chlorophenylhydrazone or by use of the temperature-sensitive mutant ts045, which is restricted to the ER at 40 degrees C, we showed that processing of G protein occurred in the ER and was not due to retention of newly synthesized Golgi enzymes. Rather, redistribution of preexisting cis and medial Golgi enzymes to the ER occurred as soon as 2.5 min after addition of BFA, and was complete by 10-15 min. Delivery of Golgi enzymes to the ER was energy dependent and occurred only at temperatures greater than or equal to 20 degrees C. BFA also induced retrograde transport of G protein from the medial Golgi to the ER. Golgi enzymes were completely recovered from the ER 10 min after removal of BFA. These findings demonstrate that BFA induces retrograde transport of both resident and itinerant Golgi proteins to the ER in a fully reversible manner.
    Type of Medium: Online Resource
    ISSN: 0021-9525 , 1540-8140
    RVK:
    Language: English
    Publisher: Rockefeller University Press
    Publication Date: 1989
    detail.hit.zdb_id: 1421310-2
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Rockefeller University Press ; 1987
    In:  The Journal of cell biology Vol. 105, No. 5 ( 1987-11-01), p. 1957-1969
    In: The Journal of cell biology, Rockefeller University Press, Vol. 105, No. 5 ( 1987-11-01), p. 1957-1969
    Abstract: We have characterized the process by which the vesicular stomatitis virus (VSV) G protein acquires its final oligomeric structure using density-gradient centrifugation in mildly acidic sucrose gradients. The mature wild-type VSV G protein is a noncovalently associated trimer. Trimers are assembled from newly synthesized G monomers with a t1/2 of 6-8 min. To localize the site of trimerization and to correlate trimer formation with steps in transport between the endoplasmic reticulum (ER) and Golgi complex, we examined the kinetics of assembly of the temperature-sensitive mutant VSV strain, ts045. At the nonpermissive temperature (39 degrees C), ts045 G protein is not transported from the ER. The phenotypic defect that inhibited export from the ER at the nonpermissive temperature was found to be the accumulation of ts045 G protein in an aggregate. After being shifted to the permissive temperature (32 degrees C), the ts045 G protein aggregate rapidly dissociated (t1/2 less than 1 min) to monomeric G protein which subsequently trimerized with the same kinetics as the wild-type G protein. Only trimers were transported to the Golgi complex. Kinetic studies, as well as the finding that trimerization occurred under conditions which block ER to Golgi transport (at both 15 and 4 degrees C), showed that trimers were formed in the ER. Depletion of cellular ATP inhibited both the dissociation of the aggregated intermediate of ts045 G protein as well as the formation of stable trimers. The results indicate that oligomerization of G protein occurs in several steps, is sensitive to cellular ATP, and is required for transport from the ER.
    Type of Medium: Online Resource
    ISSN: 0021-9525 , 1540-8140
    RVK:
    Language: English
    Publisher: Rockefeller University Press
    Publication Date: 1987
    detail.hit.zdb_id: 1421310-2
    SSG: 12
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  • 3
    Online Resource
    Online Resource
    Rockefeller University Press ; 1993
    In:  The Journal of cell biology Vol. 121, No. 3 ( 1993-05-01), p. 521-541
    In: The Journal of cell biology, Rockefeller University Press, Vol. 121, No. 3 ( 1993-05-01), p. 521-541
    Abstract: Vaccinia virus, the prototype of the Poxviridae, is a large DNA virus which replicates in the cytoplasm of the host cell. The assembly pathway of vaccinia virus displays several unique features, such as the production of two structurally distinct, infectious forms. One of these, termed intracellular naked virus (INV), remains cells associated while the other, termed extracellular enveloped virus (EEV), is released from the cell. In addition, it has long been believed that INVs acquire their lipid envelopes by a unique example of de novo membrane biogenesis. To examine the structure and assembly of vaccinia virus we have used immunoelectron microscopy using antibodies to proteins of different subcellular compartments as well as a phospholipid analysis of purified INV and EEV. Our data are not consistent with the de novo model of viral membrane synthesis but rather argue that the vaccinia virus DNA becomes enwrapped by a membrane cisterna derived from the intermediate compartment between the ER and the Golgi stacks, thus acquiring two membranes in one step. Phospholipid analysis of purified INV supports its derivation from an early biosynthetic compartment. This unique assembly process is repeated once more when the INV becomes enwrapped by an additional membrane cisterna, in agreement with earlier reports. The available data suggest that after fusion between the outer envelope and the plasma membrane, mature EEV is released from the cell.
    Type of Medium: Online Resource
    ISSN: 0021-9525 , 1540-8140
    RVK:
    Language: English
    Publisher: Rockefeller University Press
    Publication Date: 1993
    detail.hit.zdb_id: 1421310-2
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    Rockefeller University Press ; 1988
    In:  The Journal of cell biology Vol. 106, No. 3 ( 1988-03-01), p. 629-639
    In: The Journal of cell biology, Rockefeller University Press, Vol. 106, No. 3 ( 1988-03-01), p. 629-639
    Abstract: The influenza virus hemagglutinin (HA) is a well-characterized integral membrane glycoprotein composed of three identical subunits. We have analyzed the formation of mixed trimers in cells expressing two different HA gene products. The results show efficient and essentially random assembly of functional hybrid trimers provided that the HAs are from the same HA subtype. Trimerization is thus a posttranslational event, and subunits are recruited randomly from a common pool of monomers in the endoplasmic reticulum. Mixed trimers were not observed between HAs derived from different subtypes, indicating that the trimerization event is sequence specific. Mixed trimers containing mutant subunits were, moreover, used to establish that the acid-induced conformational change involved in the membrane fusion activity of HA is a highly cooperative event.
    Type of Medium: Online Resource
    ISSN: 0021-9525 , 1540-8140
    RVK:
    Language: English
    Publisher: Rockefeller University Press
    Publication Date: 1988
    detail.hit.zdb_id: 1421310-2
    SSG: 12
    Location Call Number Limitation Availability
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  • 5
    Online Resource
    Online Resource
    Rockefeller University Press ; 1986
    In:  The Journal of cell biology Vol. 103, No. 4 ( 1986-10-01), p. 1179-1191
    In: The Journal of cell biology, Rockefeller University Press, Vol. 103, No. 4 ( 1986-10-01), p. 1179-1191
    Abstract: The hemagglutinin (HA) of influenza virus is a homotrimeric integral membrane glycoprotein. It is cotranslationally inserted into the endoplasmic reticulum as a precursor called HA0 and transported to the cell surface via the Golgi complex. We have, in this study, investigated the kinetics and cellular location of the assembly reaction that results in HA0 trimerization. Three independent criteria were used for determining the formation of quaternary structure: the appearance of an epitope recognized by trimer-specific monoclonal antibodies; the acquisition of trypsin resistance, a characteristic of trimers; and the formation of stable complexes which cosedimented with the mature HA0 trimer (9S20,w) in sucrose gradients containing Triton X-100. The results showed that oligomer formation is a posttranslational event, occurring with a half time of approximately 7.5 min after completion of synthesis. Assembly occurs in the endoplasmic reticulum, followed almost immediately by transport to the Golgi complex. A stabilization event in trimer structure occurs when HA0 leaves the Golgi complex or reaches the plasma membrane. Approximately 10% of the newly synthesized HA0 formed aberrant trimers which were not transported from the endoplasmic reticulum to the Golgi complex or the plasma membrane. Taken together the results suggested that formation of correctly folded quaternary structure constitutes a key event regulating the transport of the protein out of the endoplasmic reticulum. Further changes in subunit interactions occur as the trimers move along the secretory pathway.
    Type of Medium: Online Resource
    ISSN: 0021-9525 , 1540-8140
    RVK:
    Language: English
    Publisher: Rockefeller University Press
    Publication Date: 1986
    detail.hit.zdb_id: 1421310-2
    SSG: 12
    Location Call Number Limitation Availability
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  • 6
    Online Resource
    Online Resource
    Rockefeller University Press ; 1988
    In:  The Journal of cell biology Vol. 107, No. 1 ( 1988-07-01), p. 89-99
    In: The Journal of cell biology, Rockefeller University Press, Vol. 107, No. 1 ( 1988-07-01), p. 89-99
    Abstract: The vesicular stomatitis virus glycoprotein (G protein) is an integral membrane protein which assembles into noncovalently associated trimers before transport from the endoplasmic reticulum. In this study we have examined the folding and oligomeric assembly of twelve mutant G proteins with alterations in the cytoplasmic, transmembrane, or ectodomains. Through the use of conformation-specific antibodies, we found that newly synthesized G protein folded into a conformation similar to the mature form within 1-3 min of synthesis and before trimer formation. Mutant proteins not capable of undergoing correct initial folding did not trimerize, were not transported, and were found in large aggregates. They had, as a rule, mutations in the ectodomain, including several with altered glycosylation patterns. In contrast, mutations in the cytoplasmic domain generally had little effect on folding and trimerization. These mutant proteins, whose ectodomains were identical to the wild-type by several assays, were either transported to the cell surface slowly or not at all. We concluded that while correct ectodomain folding and trimer formation are prerequisites for transport, they alone are not sufficient. The results suggest that the cytoplasmic domain of the wild-type protein may facilitate rapid, efficient transport from the ER, which can be easily affected or eliminated by tail mutations that do not detectably affect the ectodomain.
    Type of Medium: Online Resource
    ISSN: 0021-9525 , 1540-8140
    RVK:
    Language: English
    Publisher: Rockefeller University Press
    Publication Date: 1988
    detail.hit.zdb_id: 1421310-2
    SSG: 12
    Location Call Number Limitation Availability
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  • 7
    Online Resource
    Online Resource
    Rockefeller University Press ; 1986
    In:  The Journal of cell biology Vol. 102, No. 1 ( 1986-01-01), p. 11-23
    In: The Journal of cell biology, Rockefeller University Press, Vol. 102, No. 1 ( 1986-01-01), p. 11-23
    Abstract: Oligonucleotide-directed mutagenesis of a cDNA encoding the hemagglutinin of influenza virus has been used to introduce single base changes into the sequence that codes for the conserved apolar "fusion peptide" at the amino-terminus of the HA2 subunit. The mutant sequences replaced the wild-type gene in SV40-HA recombinant virus vectors, and the altered HA proteins were expressed in simian cells. Three mutants have been constructed that introduce single, nonconservative amino acid changes in the fusion peptide, and three fusion phenotypes were observed: substitution of glutamic acid for the glycine residue at the amino-terminus of HA2 abolished all fusion activity; substitution of glutamic acid for the glycine residue at position 4 in HA2 raised the threshold pH and decreased the efficiency of fusion; and, finally, extension of the hydrophobic stretch by replacement of the glutamic acid at position 11 with glycine yielded a mutant protein that induced fusion of erythrocytes with cells with the same efficiency and pH profile as the wild-type protein. However, the ability of this mutant to induce polykaryon formation was greatly impaired. Nevertheless, all the mutant proteins underwent a pH-dependent conformational change and bound to liposomes. These results are discussed in terms of the mechanism of HA-induced membrane fusion.
    Type of Medium: Online Resource
    ISSN: 0021-9525 , 1540-8140
    RVK:
    Language: English
    Publisher: Rockefeller University Press
    Publication Date: 1986
    detail.hit.zdb_id: 1421310-2
    SSG: 12
    Location Call Number Limitation Availability
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