scholarly journals A putative zinc finger protein, Saccharomyces cerevisiae Vps18p, affects late Golgi functions required for vacuolar protein sorting and efficient alpha-factor prohormone maturation.

1991 ◽  
Vol 11 (12) ◽  
pp. 5813-5824 ◽  
Author(s):  
J S Robinson ◽  
T R Graham ◽  
S D Emr
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Zinc Finger ◽  
Zinc Finger Protein ◽  
Protein Sorting ◽  
Carboxypeptidase Y ◽  
Temperature Sensitive ◽  
Vacuolar Protein Sorting ◽  
Cell Biol ◽  
Alpha Factor ◽  
Vacuolar Protein

Saccharomyces cerevisiae strains carrying vps18 mutations are defective in the sorting and transport of vacuolar enzymes. The precursor forms of these proteins are missorted and secreted from the mutant cells. Most vps18 mutants are temperature sensitive for growth and are defective in vacuole biogenesis; no structure resembling a normal vacuole is seen. A plasmid complementing the temperature-sensitive growth defect of strains carrying the vps18-4 allele was isolated from a centromere-based yeast genomic library. Integrative mapping experiments indicated that the 26-kb insert in this plasmid was derived from the VPS18 locus. A 4-kb minimal complementing fragment contains a single long open reading frame predicted to encode a 918-amino-acid hydrophilic protein. Comparison of the VPS18 sequence with the PEP3 sequence reported in the accompanying paper (R. A. Preston, H. F. Manolson, K. Becherer, E. Weidenhammer, D. Kirkpatrick, R. Wright, and E. W. Jones, Mol. Cell. Biol. 11:5801-5812, 1991) shows that the two genes are identical. Disruption of the VPS18/PEP3 gene (vps18 delta 1::TRP1) is not lethal but results in the same vacuolar protein sorting and growth defects exhibited by the original temperature-sensitive vps18 alleles. In addition, vps18 delta 1::TRP1 MAT alpha strains exhibit a defect in the Kex2p-dependent processing of the secreted pheromone alpha-factor. This finding suggests that vps18 mutations alter the function of a late Golgi compartment which contains Kex2p and in which vacuolar proteins are thought to be sorted from proteins destined for the cell surface. The Vps18p sequence contains a cysteine-rich, zinc finger-like motif at the COOH terminus. A mutant in which the first cysteine of this motif was changed to serine results in a temperature-conditional carboxypeptidase Y sorting defect shortly after a shift to nonpermissive conditions. We identified a similar cysteine-rich motif near the COOH terminus of another Vps protein, the Vps11/Pep5/End1 protein. Preston et al. (Mol. Cell. Biol. 11:5801-5812, 1991) present evidence that the Vps18/Pep3 protein colocalizes with the Vps11/Pep5 protein to the cytosolic face of the vacuolar membrane. Together with the similar phenotypes exhibited by both vps11 and vps18 mutants, this finding suggests that they may function at a common step during vacuolar protein sorting and that the integrity of their zinc finger motifs may be required for this function.

scholarly journals A putative zinc finger protein, Saccharomyces cerevisiae Vps18p, affects late Golgi functions required for vacuolar protein sorting and efficient alpha-factor prohormone maturation

1991 ◽  
Vol 11 (12) ◽  
pp. 5813-5824
Author(s):  
J S Robinson ◽  
T R Graham ◽  
S D Emr
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Zinc Finger ◽  
Zinc Finger Protein ◽  
Protein Sorting ◽  
Carboxypeptidase Y ◽  
Temperature Sensitive ◽  
Vacuolar Protein Sorting ◽  
Cell Biol ◽  
Alpha Factor ◽  
Vacuolar Protein

Saccharomyces cerevisiae strains carrying vps18 mutations are defective in the sorting and transport of vacuolar enzymes. The precursor forms of these proteins are missorted and secreted from the mutant cells. Most vps18 mutants are temperature sensitive for growth and are defective in vacuole biogenesis; no structure resembling a normal vacuole is seen. A plasmid complementing the temperature-sensitive growth defect of strains carrying the vps18-4 allele was isolated from a centromere-based yeast genomic library. Integrative mapping experiments indicated that the 26-kb insert in this plasmid was derived from the VPS18 locus. A 4-kb minimal complementing fragment contains a single long open reading frame predicted to encode a 918-amino-acid hydrophilic protein. Comparison of the VPS18 sequence with the PEP3 sequence reported in the accompanying paper (R. A. Preston, H. F. Manolson, K. Becherer, E. Weidenhammer, D. Kirkpatrick, R. Wright, and E. W. Jones, Mol. Cell. Biol. 11:5801-5812, 1991) shows that the two genes are identical. Disruption of the VPS18/PEP3 gene (vps18 delta 1::TRP1) is not lethal but results in the same vacuolar protein sorting and growth defects exhibited by the original temperature-sensitive vps18 alleles. In addition, vps18 delta 1::TRP1 MAT alpha strains exhibit a defect in the Kex2p-dependent processing of the secreted pheromone alpha-factor. This finding suggests that vps18 mutations alter the function of a late Golgi compartment which contains Kex2p and in which vacuolar proteins are thought to be sorted from proteins destined for the cell surface. The Vps18p sequence contains a cysteine-rich, zinc finger-like motif at the COOH terminus. A mutant in which the first cysteine of this motif was changed to serine results in a temperature-conditional carboxypeptidase Y sorting defect shortly after a shift to nonpermissive conditions. We identified a similar cysteine-rich motif near the COOH terminus of another Vps protein, the Vps11/Pep5/End1 protein. Preston et al. (Mol. Cell. Biol. 11:5801-5812, 1991) present evidence that the Vps18/Pep3 protein colocalizes with the Vps11/Pep5 protein to the cytosolic face of the vacuolar membrane. Together with the similar phenotypes exhibited by both vps11 and vps18 mutants, this finding suggests that they may function at a common step during vacuolar protein sorting and that the integrity of their zinc finger motifs may be required for this function.

scholarly journals A yeast protein related to a mammalian Ras-binding protein, Vps9p, is required for localization of vacuolar proteins.

1996 ◽  
Vol 16 (5) ◽  
pp. 2369-2377 ◽  
Author(s):  
C G Burd ◽  
P A Mustol ◽  
P V Schu ◽  
S D Emr
Keyword(s):  
Intracellular Transport ◽  
Protein Sorting ◽  
Growth Defect ◽  
Carboxypeptidase Y ◽  
Rab Gtpase ◽  
Temperature Sensitive ◽  
Electron Microscopic ◽  
Yeast Saccharomyces Cerevisiae ◽  
Vacuolar Protein Sorting ◽  
Vacuolar Protein

In the yeast Saccharomyces cerevisiae, mutations in vacuolar protein sorting (VPS) genes result in secretion of proteins normally localized to the vacuole. Characterization of the VPS pathway has provided considerable insight into mechanisms of protein sorting and vesicle-mediated intracellular transport. We have cloned VPS9 by complementation of the vacuolar protein sorting defect of vps9 cells, characterized its gene product, and investigated its role in vacuolar protein sorting. Cells with a vps9 disruption exhibit severe vacuolar protein sorting defects and a temperature-sensitive growth defect at 38 degrees C. Electron microscopic examination of delta vps9 cells revealed the appearance of novel reticular membrane structures as well as an accumulation of 40- to 50-nm-diameter vesicles, suggesting that Vps9p may be required for the consumption of transport vesicles containing vacuolar protein precursors. A temperature-conditional allele of vps9 was constructed and used to investigate the function of Vps9p. Immediately upon shifting of temperature-conditional vps9 cells to the nonpermissive temperature, newly synthesized carboxypeptidase Y was secreted, indicating that Vps9p function is directly required in the VPS pathway. Antibodies raised against Vps9p immunoprecipitate a rare 52-kDa protein that fractionates with cytosolic proteins following cell lysis and centrifugation. Analysis of the VPS9 DNA sequence predicts that Vps9p is related to human proteins that bind Ras and negatively regulate Ras-mediated signaling. We term the related regions of Vps9p and these Ras-binding proteins a GTPase binding homology domain and suggest that it defines a family of proteins that bind monomeric GTPases. Vps9p may bind and serve as an effector of a rab GTPase, like Vps2lp, required for vacuolar protein sorting.

scholarly journals Synthetic Genetic Interactions With Temperature-Sensitive Clathrin in Saccharomyces cerevisiae: Roles for Synaptojanin-Like Inp53p and Dynamin-Related Vps1p in Clathrin-Dependent Protein Sorting at the trans-Golgi Network

Genetics ◽  
2000 ◽  
Vol 154 (1) ◽  
pp. 83-97
Author(s):  
Eric S Bensen ◽  
Giancarlo Costaguta ◽  
Gregory S Payne
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Molecular Mechanisms ◽  
Protein Transport ◽  
Protein Sorting ◽  
Genetic Interactions ◽  
Carboxypeptidase Y ◽  
Temperature Sensitive ◽  
Trans Golgi Network ◽  
Vacuolar Protein ◽  
Golgi Network

Abstract Clathrin is involved in selective protein transport at the Golgi apparatus and the plasma membrane. To further understand the molecular mechanisms underlying clathrin-mediated protein transport pathways, we initiated a genetic screen for mutations that display synthetic growth defects when combined with a temperature-sensitive allele of the clathrin heavy chain gene (chc1-521) in Saccharomyces cerevisiae. Mutations, when present in cells with wild-type clathrin, were analyzed for effects on mating pheromone α-factor precursor maturation and sorting of the vacuolar protein carboxypeptidase Y as measures of protein sorting at the yeast trans-Golgi network (TGN) compartment. By these criteria, two classes of mutants were obtained, those with and those without defects in protein sorting at the TGN. One mutant with unaltered protein sorting at the TGN contains a mutation in PTC1, a type 2c serine/threonine phosphatase with widespread influences. The collection of mutants displaying TGN sorting defects includes members with mutations in previously identified vacuolar protein sorting genes (VPS), including the dynamin family member VPS1. Striking genetic interactions were observed by combining temperature-sensitive alleles of CHC1 and VPS1, supporting the model that Vps1p is involved in clathrin-mediated vesicle formation at the TGN. Also in the spectrum of mutants with TGN sorting defects are isolates with mutations in the following: RIC1, encoding a product originally proposed to participate in ribosome biogenesis; LUV1, encoding a product potentially involved in vacuole and microtubule organization; and INP53, encoding a synaptojanin-like inositol polyphosphate 5-phosphatase. Disruption of INP53, but not the related INP51 and INP52 genes, resulted in α-factor maturation defects and exacerbated α-factor maturation defects when combined with chc1-521. Our findings implicate a wide variety of proteins in clathrin-dependent processes and provide evidence for the selective involvement of Inp53p in clathrin-mediated protein sorting at the TGN.

scholarly journals A subset of yeast vacuolar protein sorting mutants is blocked in one branch of the exocytic pathway

2002 ◽  
Vol 156 (2) ◽  
pp. 271-286 ◽  
Author(s):  
Edina Harsay ◽  
Randy Schekman
Keyword(s):  
Protein Sorting ◽  
Carboxypeptidase Y ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Vacuolar Protein Sorting ◽  
Sorting Receptor ◽  
Gradient Fractionation ◽  
Vacuolar Protein ◽  
Exocytic Pathway ◽  
Dense Vesicles

Exocytic vesicles that accumulate in a temperature-sensitive sec6 mutant at a restrictive temperature can be separated into at least two populations with different buoyant densities and unique cargo molecules. Using a sec6 mutant background to isolate vesicles, we have found that vacuolar protein sorting mutants that block an endosome-mediated route to the vacuole,including vps1, pep12, vps4, and a temperature-sensitive clathrin mutant, missort cargo normally transported by dense exocytic vesicles, such as invertase, into light exocytic vesicles, whereas transport of cargo specific to the light exocytic vesicles appears unaffected. Immunoisolation experiments confirm that missorting, rather than a changed property of the normally dense vesicles, is responsible for the altered density gradient fractionation profile. The vps41Δ and apl6Δmutants, which block transport of only the subset of vacuolar proteins that bypasses endosomes, sort exocytic cargo normally. Furthermore, avps10Δ sec6 mutant, which lacks the sorting receptor for carboxypeptidase Y (CPY), accumulates both invertase and CPY in dense vesicles. These results suggest that at least one branch of the yeast exocytic pathway transits through endosomes before reaching the cell surface. Consistent with this possibility, we show that immunoisolated clathrin-coated vesicles contain invertase.

scholarly journals Vesicle-mediated protein transport: regulatory interactions between the Vps15 protein kinase and the Vps34 PtdIns 3-kinase essential for protein sorting to the vacuole in yeast.

1995 ◽  
Vol 129 (2) ◽  
pp. 321-334 ◽  
Author(s):  
J H Stack ◽  
D B DeWald ◽  
K Takegawa ◽  
S D Emr
Keyword(s):  
Protein Kinase ◽  
Kinase Activity ◽  
Protein Sorting ◽  
Intracellular Localization ◽  
Kinase Domain ◽  
Carboxypeptidase Y ◽  
Temperature Sensitive ◽  
Nonpermissive Temperature ◽  
Vacuolar Protein Sorting ◽  
Vacuolar Protein

A membrane-associated complex composed of the Vps15 protein kinase and the Vps34 phosphatidylinositol 3-kinase (PtdIns 3-kinase) is essential for the delivery of proteins to the yeast vacuole. An active Vps15p is required for the recruitment of Vps34p to the membrane and subsequent stimulation of Vps34p PtdIns 3-kinase activity. Consistent with this, mutations altering highly conserved residues in the lipid kinase domain of Vps34p lead to a dominant-negative phenotype resulting from titration of activating Vps15 proteins. In contrast, catalytically inactive Vps15p mutants do not produce a dominant mutant phenotype because they are unable to associate with Vps34p in a wild-type manner. These data indicate that an intact Vps15p protein kinase domain is necessary for the association with and activation of Vps34p, and they demonstrate that a functional Vps15p-Vps34p complex is absolutely required for the efficient delivery of proteins to the vacuole. Analysis of a temperature-conditional allele of VPS15, in which a shift to the nonpermissive temperature leads to a decrease in cellular PtdIns(3)P levels, indicates that the loss of Vps15p function leads to a defect in activation of Vps34p. In addition, characterization of a temperature-sensitive allele of VPS34 demonstrates that inactivation of Vps34p leads to the immediate missorting of soluble vacuolar proteins (e.g., carboxypeptidase Y) without an apparent defect in the sorting of the vacuolar membrane protein alkaline phosphatase. This rapid block in vacuolar protein sorting appears to be the result of loss of PtdIns 3-kinase activity since cellular PtdIns(3)P levels decrease dramatically in vps34 temperature-sensitive mutant cells that have been incubated at the nonpermissive temperature. Finally, analysis of the defects in cellular PtdIns(3)P levels in various vps15 and vsp34 mutant strains has led to additional insights into the importance of PtdIns(3)P intracellular localization, as well as the roles of Vps15p and Vps34p in vacuolar protein sorting.

Two homologous zinc finger genes identified by multicopy suppression in a SNF1 protein kinase mutant of Saccharomyces cerevisiae

1993 ◽  
Vol 13 (7) ◽  
pp. 3872-3881
Author(s):  
F Estruch ◽  
M Carlson
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Kinase ◽  
Zinc Finger ◽  
Zinc Finger Protein ◽  
Wilms Tumor ◽  
Temperature Sensitive ◽  
Carbon Utilization ◽  
Functional Roles ◽  
Multicopy Suppressor ◽  
Finger Protein

The MSN2 gene was selected as a multicopy suppressor in a temperature-sensitive SNF1 protein kinase mutant of Saccharomyces cerevisiae. MSN2 encodes a Cys2His2 zinc finger protein related to the yeast MIG1 repressor and to mammalian early growth response and Wilms' tumor zinc finger proteins. Deletion of MSN2 caused no phenotype. A second similar zinc finger gene, MSN4, was isolated, and deletion of both genes caused phenotypic defects related to carbon utilization. Overexpression of the zinc finger regions was deleterious to growth. LexA-MSN2 and LexA-MSN4 fusion proteins functioned as strong transcriptional activators when bound to DNA. Functional roles of this zinc finger protein family are discussed.

scholarly journals Protein sorting in Saccharomyces cerevisiae: isolation of mutants defective in the delivery and processing of multiple vacuolar hydrolases.

1988 ◽  
Vol 8 (11) ◽  
pp. 4936-4948 ◽  
Author(s):  
J S Robinson ◽  
D J Klionsky ◽  
L M Banta ◽  
S D Emr
Keyword(s):  
Cell Surface ◽  
Protein Sorting ◽  
Vacuolar Membrane ◽  
Temperature Sensitive ◽  
Vacuolar Protein Sorting ◽  
Proteinase A ◽  
Complementation Groups ◽  
The Right ◽  
Vacuolar Protein ◽  
Mutant Cells

Using a selection for spontaneous mutants that mislocalize a vacuolar carboxypeptidase Y (CPY)-invertase fusion protein to the cell surface, we identified vacuolar protein targeting (vpt) mutants in 25 new vpt complementation groups. Additional alleles in each of the eight previously identified vpt complementation groups (vpt1 through vpt8) were also obtained. Representative alleles from each of the 33 vpt complementation groups (vpt1 through vpt33) were shown to exhibit defects in the sorting and processing of several native vacuolar proteins, including the soluble hydrolases CPY, proteinase A, and proteinase B. Of the 33 complementation groups, 19 were found to contain mutant alleles that led to extreme defects. In these mutants, CPY accumulated in its Golgi complex-modified precursor form which was secreted by the mutant cells. Normal protein secretion appeared to be unaffected in the vpt mutants. The lack of significant leakage of cytosolic markers from the vpt mutant cells indicated that the vacuolar protein-sorting defects associated with these mutants do not result from cell lysis. In addition, the observation that the precursor rather than the mature forms of CPY, proteinase A, proteinase B were secreted from the vpt mutants was consistent with the fact that mislocalization occurred at a stage after Golgi complex-specific modification, but before final vacuolar sorting of these enzymes. Vacuolar membrane protein sorting appeared to be unaffected in the majority of the vpt mutants. However, a subset of the vpt mutants (vpt11, vpt16, vpt18, and vpt33) was found to exhibit defects in the sorting of a vacuolar membrane marker enzyme, alpha-mannosidase. Up to 50% of the alpha-mannosidase enzyme activity was found to be mislocalized to the cell surface in these vpt mutants. Seven of the vpt complementation groups (vpt3, vpt11, vpt15, vpt16, vpt18, vpt29, and vpt33) contained alleles that led to a conditional lethal phenotype; the mutants were temperature sensitive for vegetative cell growth. This temperature-sensitive phenotype has been shown to be recessive and to cosegregate with the vacuolar protein-sorting defect in each case. Tetrad analysis showed that vpt3 mapped to the right arm of chromosome XV and that vpt15 mapped to the right arm of chromosome II. Intercrosses with other mutants that exhibited defects in vacuolar protein sorting or function (vpl, sec, pep, and end mutants) revealed several overlaps among these different sets of genes. Together, these data indicate that more than 50 gene products are involved, directly or indirectly, in the process of vacuolar protein sorting.

scholarly journals A sorting nexin-1 homologue, Vps5p, forms a complex with Vps17p and is required for recycling the vacuolar protein-sorting receptor.

1997 ◽  
Vol 8 (8) ◽  
pp. 1529-1541 ◽  
Author(s):  
B F Horazdovsky ◽  
B A Davies ◽  
M N Seaman ◽  
S A McLaughlin ◽  
S Yoon ◽  
...  
Keyword(s):  
Gene Product ◽  
Protein Sorting ◽  
Carboxypeptidase Y ◽  
Vacuolar Protein Sorting ◽  
Sorting Nexin ◽  
Class B ◽  
Sorting Receptor ◽  
Vacuolar Protein ◽  
Mutant Cells ◽  
Sorting Nexin 1

A number of the Saccharomyces cerevisiae vacuolar protein-sorting (vps) mutants exhibit an altered vacuolar morphology. Unlike wild-type cells that contain 1-3 large vacuolar structures, the class B vps5 and vps17 mutant cells contain 10-20 smaller vacuole-like compartments. To explore the role of these VPS gene products in vacuole biogenesis, we cloned and sequenced VPS5 and characterized its protein products. The VPS5 gene is predicted to encode a very hydrophilic protein of 675 amino acids that shows significant sequence homology with mammalian sorting nexin-1. Polyclonal antiserum directed against the VPS5 gene product detects a single, cytoplasmic protein that is phosphorylated specifically on a serine residue(s). Subcellular fractionation studies indicate that Vps5p is associated peripherally with a dense membrane fraction distinct from Golgi, endosomal, and vacuolar membranes. This association was found to be dependent on the presence of another class B VPS gene product, Vps17p. Biochemical cross-linking studies demonstrated that Vps5p and Vps17p physically interact. Gene disruption experiments show that the VPS5 genes product is not essential for cell viability; however, cells carrying the null allele contain fragmented vacuoles and exhibit defects in vacuolar protein-sorting similar to vps17 null mutants. More than 95% of carboxypeptidase Y is secreted from these cells in its Golgi-modified p2 precursor form. Additionally, the Vps10p vacuolar protein-sorting receptor is mislocalized to the vacuole in vps5 mutant cells. On the basis of these and other observations, we propose that the Vps17p protein complex may participate in the intracellular trafficking of the Vps10p-sorting receptor, as well as other later-Golgi proteins.

scholarly journals Involvement of Specific COPI Subunits in Protein Sorting from the Late Endosome to the Vacuole in Yeast

2006 ◽  
Vol 27 (2) ◽  
pp. 526-540 ◽  
Author(s):  
Galina Gabriely ◽  
Rachel Kama ◽  
Jeffrey E. Gerst
Keyword(s):  
Mammalian Cells ◽  
Secretory Pathway ◽  
Protein Sorting ◽  
Multivesicular Body ◽  
Carboxypeptidase Y ◽  
Direct Role ◽  
Vacuolar Protein Sorting ◽  
Early Secretory Pathway ◽  
Physical Interactions ◽  
Vacuolar Protein

ABSTRACT Although COPI function on the early secretory pathway in eukaryotes is well established, earlier studies also proposed a nonconventional role for this coat complex in endocytosis in mammalian cells. Here we present results that suggest an involvement for specific COPI subunits in the late steps of endosomal protein sorting in Saccharomyces cerevisiae. First, we found that carboxypeptidase Y (CPY) was partially missorted to the cell surface in certain mutants of the COPIB subcomplex (COPIb; Sec27, Sec28, and possibly Sec33), which indicates an impairment in endosomal transport. Second, integral membrane proteins destined for the vacuolar lumen (i.e., carboxypeptidase S [CPS1]; Fur4, Ste2, and Ste3) accumulated at an aberrant late endosomal compartment in these mutants. The observed phenotypes for COPIb mutants resemble those of class E vacuolar protein sorting (vps) mutants that are impaired in multivesicular body (MVB) protein sorting and biogenesis. Third, we observed physical interactions and colocalization between COPIb subunits and an MVB-associated protein, Vps27. Together, our findings suggest that certain COPI subunits could have a direct role in vacuolar protein sorting to the MVB compartment.

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