Functional compartments of the yeast Golgi apparatus are defined by the sec7 mutation.

Franzusoff, Alex; Schekman, Randy

doi:10.1002/j.1460-2075.1989.tb08410.x

Cited by 236 publications

(203 citation statements)

References 57 publications

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“…The speed of GFP-Snc1p recycling was revealed most dramatically by continuous monitoring of individual cells of a sec14-3 strain, in which exit from the Golgi is blocked at high temperature (Novick et al, 1980;Franzusoff and Schekman, 1989). After a shift of the cells to 37°C, GFP-Snc1p moved from the cell surface to internal structures.…”

Section: Recycling Of Snc1pmentioning

confidence: 99%

Specific Retrieval of the Exocytic SNARE Snc1p from Early Yeast Endosomes

Lewis

Nichols

Prescianotto-Baschong

et al. 2000

MBoC

333

515

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Many endocytosed proteins in yeast travel to the vacuole, but some are recycled to the plasma membrane. We have investigated the recycling of chimeras containing green fluorescent protein (GFP) and the exocytic SNARE Snc1p. GFP-Snc1p moves from the cell surface to internal structures when Golgi function or exocytosis is blocked, suggesting continuous recycling via the Golgi. Internalization is mediated by a conserved cytoplasmic signal, whereas diversion from the vacuolar pathway requires sequences within and adjacent to the transmembrane domain. Delivery from the Golgi to the surface is also influenced by the transmembrane domain, but the requirements are much less specific. Recycling requires the syntaxins Tlg1p and Tlg2p but not Pep12p or proteins such as Vps4p and Vps5p that have been implicated in late endosome–Golgi traffic. Subtle changes to the recycling signal cause GFP-Snc1p to accumulate preferentially in punctate internal structures, although it continues to recycle to the surface. The internal GFP-Snc1p colocalizes with Tlg1p, and immunofluorescence and immunoelectron microscopy reveal structures that contain Tlg1p, Tlg2p, and Kex2p but lack Pep12p and Sec7p. We propose that these represent early endosomes in which sorting of Snc1p and late Golgi proteins occurs, and that transport can occur directly from them to the Golgi apparatus.

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Section: Recycling Of Snc1pmentioning

confidence: 99%

Specific Retrieval of the Exocytic SNARE Snc1p from Early Yeast Endosomes

Lewis

Nichols

Prescianotto-Baschong

et al. 2000

MBoC

333

515

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“…The SEC12 gene codes for a GDP/GTP exchange factor that is required for vesicle budding and exit from the ER (Barlowe and Schekman, 1993). Sec7 is a GDP/GTP exchange factor required for trafficking through the Golgi (Franzusoff and Schekman, 1989;Jackson and Casanova, 2000). Wild-type and mutant cells expressing GFP-Atg8 were grown at 24°C and then analyzed with a fluorescence microscope and successively transferred to a 37°C incubator.…”

Section: Both the Er And The Golgi Complex Are Involved In Pas Formatmentioning

confidence: 99%

Early Stages of the Secretory Pathway, but Not Endosomes, Are Required for Cvt Vesicle and Autophagosome Assembly inSaccharomyces cerevisiae

Reggiori

Wang

Nair

et al. 2004

MBoC

129

163

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The Cvt pathway is a biosynthetic transport route for a distinct subset of resident yeast vacuolar hydrolases, whereas macroautophagy is a nonspecific degradative mechanism that allows cell survival during starvation. Yet, these two vacuolar trafficking pathways share a number of identical molecular components and are morphologically very similar. For example, one of the hallmarks of both pathways is the formation of double-membrane cytosolic vesicles that sequester cargo before vacuolar delivery. The origin of the vesicle membrane has been controversial and various lines of evidence have implicated essentially all compartments of the endomembrane system. Despite the analogies between the Cvt pathway and autophagy, earlier work has suggested that the origin of the engulfing vesicle membranes is different; the endoplasmic reticulum is proposed to be required only for autophagy. In contrast, in this study we demonstrate that the endoplasmic reticulum and/or Golgi complex, but not endosomal compartments, play an important role for both yeast transport routes. Along these lines, we demonstrate that Berkeley bodies, a structure generated from the Golgi complex in sec7 cells, are immunolabeled with Atg8, a structural component of autophagosomes. Finally, we also show that none of the yeast t-SNAREs are located at the preautophagosomal structure, the presumed site of double-membrane vesicle formation. Based on our results, we propose two models for Cvt vesicle biogenesis. INTRODUCTIONThe lysosome/vacuole is the major cellular center for degradation, recycling, and storage of biological constituents. Several well-characterized transport routes are implicated in protein delivery to this organelle during normal growth conditions. These pathways are conserved among eukaryotic organisms, but work in the yeast Saccharomyces cerevisiae has had a major impact on their characterization and in the identification of the molecular machinery (Conibear and Stevens, 1998). The route called the alkaline phosphatase pathway provides a direct transport connection between the Golgi complex and the vacuole Piper et al., 1997). A second itinerary from the Golgi complex to the vacuole passes through the late endosome and is known as the carboxypeptidase Y pathway (Piper et al., 1995;Babst et al., 1998;Conibear and Stevens, 1998). These two pathways are required for the biogenesis and maintenance of vacuoles, whereas a third route, endocytosis, has a catabolic function. Endocytosis mediates the downregulation of plasma membrane proteins by delivering them via the late endosome to the vacuole for degradation (Hicke, 1999;Katzmann et al., 2002). Before reaching the late endosome, these proteins pass through the early endosome where some components are recycled back to the cell surface (Hicke et al., 1997;Prescianotto-Baschong and Riezman, 1998;Lewis et al., 2000). The carboxypeptidase Y pathway and endocytosis converge at the endosome where another route, the multivesicular body pathway, delivers both resident enzymes and substrates to the vac...

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“…Antibodies to a-1-3 and a-1-6 mannose linkages were a generous gift of R. Schekman (Berkeley) and have already been described (Franzusoff and Schekman, 1989). Affinity purified antibodies to Kar2p were a gift of B. Chaudhuri (Basel).…”

Section: Antiseramentioning

confidence: 99%

“…The latter mechanism would lead to Golgi-specific limited outer-chain glycosyl modification of the core glycosylated mutant proteins. These outer-chain glycosyl modifications occur in at least two distinct Golgi compartments (Franzusoff and Schekman, 1989 ;Graham and Emr, 1991). In the first Golgi compartment, a-l-6-mannosyl residues are added to the core glycosyls.…”

Section: Pra* and Cpy* Are Not A-1+6 Or A-1-+3 Mannosylatedmentioning

confidence: 99%

Analysis of two mutated vacuolar proteins reveals a degradation pathway in the endoplasmic reticulum or a related compartment of yeast

Finger

Knop

Wolf

1993

European Journal of Biochemistry

194

174

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The fate of a mutant form of each of the two yeast vacuolar enzymes proteinase yscA (PrA) and carboxypeptidase yscY (CPY) has been investigated. Both mutant proteins are rapidly degraded after entering the secretory pathway. Mutant PrA is deleted in 37 amino acids spanning the processing site region of the PrA pro‐peptide. The mutant enzyme shows no activity towards maturation of itself or other vacuolar hydrolases, a function of wild‐type PrA. Mutant CPY carries an Arg instead of a Gly residue in a highly conserved region, two positions distant from the active‐site Ser. In contrast to wild‐type CPY, the mutant form was quickly degraded by trypsin in vitro, indicating an altered structure. Using antisera specific for α‐1→6 and α‐1→3 outer‐chain mannose linkages, no Golgi‐specific carbohydrate modification could be detected on either mutant protein. Subcellular fractionation studies located both mutant enzymes in the endoplasmic reticulum. Degradation kinetics of both proteins show the same characteristics, indicating similar degradation pathways. The degradation process was shown to be independent of a functional sec18 gene product and takes place before Golgi‐specific carbohydrate modifications occur. The proteasome, the major proteolytic activity of the cytoplasm, is not involved in this degradation event. All degradation characteristics of the two mutant proteins are consistent with a degradation process within the endoplasmic reticulum (‘ER degradation’).

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Functional compartments of the yeast Golgi apparatus are defined by the sec7 mutation.

Cited by 236 publications

References 57 publications

Specific Retrieval of the Exocytic SNARE Snc1p from Early Yeast Endosomes

Specific Retrieval of the Exocytic SNARE Snc1p from Early Yeast Endosomes

Early Stages of the Secretory Pathway, but Not Endosomes, Are Required for Cvt Vesicle and Autophagosome Assembly inSaccharomyces cerevisiae

Analysis of two mutated vacuolar proteins reveals a degradation pathway in the endoplasmic reticulum or a related compartment of yeast

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