Proteolytic Function of GPI‐Anchored Plasma Membrane Protease Yps1p in the Yeast Vacuole and Golgi

Sievi, Eeva; Suntio, Taina; Makarow, Marja

doi:10.1034/j.1600-0854.2001.21205.x

Cited by 33 publications

(24 citation statements)

References 51 publications

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“…In order to test these assertions, we constructed a reporter plasmid with lacZ fused to the intergenic region 5Ј to YPS1 and examined the expression of YPS1 under conditions that either cause cell wall stress, require cell wall remodeling, or increase expression of the inducible subunit of 1,3-␤-glucan synthase, FKS2 (67). Consistent with the findings of Ash et al (2) and Sievi et al (58), expression of YPS1 was extremely low at 25°C but increased fourfold upon shift to 37°C in YPD (Table 6). Treatment of wild-type cells with zymolyase, a 1,3-␤-glucanase-containing enzyme preparation, increased YPS1 expression sevenfold.…”

Section: Resultssupporting

confidence: 71%

“…Because the yapsins are GPI-linked proteins, they have two possible localizations: the plasma membrane and the cell wall (30). YPS1, -2, -3, and -6 all have C-terminal sequence motifs consistent with plasma membrane localization (18,23), and in the cases of Yps1p and Yps2p, such localization has been confirmed experimentally (2,32,58). On the other hand, the C-terminal motif in YPS7 is suggestive of a cell wall-localized GPI protein (23).…”

Section: Discussionmentioning

confidence: 89%

“…Supporting the notion that YPS1 is induced during periods of cell wall stress, quantitative immunoblotting experiments have shown that Yps1p is increased 12-fold when cells are shifted from 24°C to 37°C (2). Similarly, Yps1p could not be detected by immunofluorescence at 24°C, but robust plasma membranelocalized fluorescence was evident at 37°C (58). Additionally, a recent genome-wide screen for mutants resistant to killer toxin, and, therefore, involved in 1,6-␤-glucan-related processes, identified the yps7⌬ mutant (51).…”

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confidence: 74%

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Yapsins Are a Family of Aspartyl Proteases Required for Cell Wall Integrity in Saccharomyces cerevisiae

et al. 2005

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The yeast cell wall is a crucial extracellular organelle that protects the cell from lysis during environmental stress and morphogenesis. Here, we demonstrate that the yapsin family of five glycosylphosphatidylinositollinked aspartyl proteases is required for cell wall integrity in Saccharomyces cerevisiae. Yapsin null mutants show hypersensitivity to cell wall perturbation, and both the yps1⌬2⌬ mutant and the quintuple yapsin mutant (5yps⌬) undergo osmoremedial cell lysis at 37°C. The cell walls of both 5yps⌬ and yps1⌬2⌬ mutants have decreased amounts of 1,3-and 1,6-␤-glucan. Although there is decreased incorporation of both 1,3-and 1,6-␤-glucan in the 5yps⌬ mutant in vivo, in vitro specific activity of both 1,3-and 1,6-␤-glucan synthesis is similar to wild type, indicating that the yapsins affect processes downstream of glucan synthesis and that the yapsins may be involved in the incorporation or retention of cell wall glucan. Presumably as a response to the significant alterations in cell wall composition, the cell wall integrity mitogen-activated kinase signaling cascade (PKC1-MPK pathway) is basally active in 5yps⌬. YPS1 expression is induced during cell wall stress and remodeling in a PKC1-MPK1-dependent manner, indicating that Yps1p is a direct, and important, output of the cell wall integrity response. The Candida albicans (SAP9) and Candida glabrata (CgYPS1) homologues of YPS1 complement the phenotypes of the yps1⌬ mutant. Taken together, these data indicate that the yapsins play an important role in glucan homeostasis in S. cerevisiae and that yapsin homologues may play a similar role in the pathogenic yeasts C. albicans and C. glabrata.The yapsins are a family of five glycosylphosphatidylinositol (GPI)-linked aspartyl proteases (YPS1 to -3, -6, and -7) in Saccharomyces cerevisiae that have homologues in other fungi such as Candida albicans (43), Candida glabrata (16), and Aspergillus oryzae (36). The founding members of this family, YPS1 and -2 (17, 32), were identified as suppressors of null mutations in KEX2, a trans-Golgi network-localized serine protease that processes secretory proteins such as pro-␣-factor and the exoglucanase Exg1p (3, 53). The remaining three yapsins were subsequently identified by sequence homology following completion of the S. cerevisiae genome sequence (47). Like Kex2p, three of the yapsins (Yps1p, -2p, and -3p) cleave proteins and peptides C terminal to basic residues, both in vivo and in vitro (8, 33). Although Kex2p is exquisitely selective for Lys-Arg pairs (53), the yapsins cleave C terminal to monobasic sites containing either Lys or Arg (33, 48). In vivo, Yps1p cleaves human mammalian prohormones such as ACTH and CCK (8) and both Yps1p and Yps2p display secretase-like activity toward ␤-amyloid precursor protein that is expressed in yeast (34,66). To date, however, no yeast substrates have been identified; moreover, the physiologic function of the yapsins in S. cerevisiae has been unclear.Previously reported work from this laboratory showed that the yapsin double nul...

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Section: Resultssupporting

confidence: 71%

Section: Discussionmentioning

confidence: 89%

mentioning

confidence: 74%

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Yapsins Are a Family of Aspartyl Proteases Required for Cell Wall Integrity in Saccharomyces cerevisiae

et al. 2005

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“…This notion is supported by a recent biophysical study, which demonstrates that ergosterol is significantly more strongly domain-promoting than cholesterol (Xu et al, 2001). Moreover, in erg6⌬ mutants the GPI-anchored plasma membrane protease, Yps1p, is mistargeted to the vacuole, indicating that the precise structure of the sterol is important for raft function in vivo (Sievi et al, 2001).…”

Section: Raft Formation In the Elo3⌬ Erg6⌬ Double Mutantmentioning

confidence: 99%

A Specific Structural Requirement for Ergosterol in Long-chain Fatty Acid Synthesis Mutants Important for Maintaining Raft Domains in Yeast

Eisenkolb

Zenzmaier

Leitner

et al. 2002

MBoC

115

120

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Fungal sphingolipids contain ceramide with a very-long-chain fatty acid (C26). To investigate the physiological significance of the C26-substitution on this lipid, we performed a screen for mutants that are synthetically lethal with ELO3. Elo3p is a component of the ER-associated fatty acid elongase and is required for the final elongation cycle to produce C26 from C22/C24 fatty acids. elo3⌬ mutant cells thus contain C22/C24-instead of the natural C26-substituted ceramide. We now report that under these conditions, an otherwise nonessential, but also fungal-specific, structural modification of the major sterol of yeast, ergosterol, becomes essential, because mutations in ELO3 are synthetically lethal with mutations in ERG6. Erg6p catalyzes the methylation of carbon atom 24 in the aliphatic side chain of sterol. The lethality of an elo3⌬ erg6⌬ double mutant is rescued by supplementation with ergosterol but not with cholesterol, indicating a vital structural requirement for the ergosterol-specific methyl group. To characterize this structural requirement in more detail, we generated a strain that is temperature sensitive for the function of Erg6p in an elo3⌬ mutant background. Examination of raft association of the GPI-anchored Gas1p and plasma membrane ATPase, Pma1p, in the conditional elo3⌬ erg6 ts double mutant, revealed a specific defect of the mutant to maintain raft association of preexisting Pma1p. Interestingly, in an elo3⌬ mutant at 37°C, newly synthesized Pma1p failed to enter raft domains early in the biosynthetic pathway, and upon arrival at the plasma membrane was rerouted to the vacuole for degradation. These observations indicate that the C26 fatty acid substitution on lipids is important for establishing raft association of Pma1p and stabilizing the protein at the cell surface. Analysis of raft lipids in the conditional mutant strain revealed a selective enrichment of ergosterol in detergent-resistant membrane domains, indicating that specific structural determinants on both sterols and sphingolipids are required for their association into raft domains.

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“…It is likely that the properties of lipid rafts are altered by the ergosterol intermediates accumulated in erg6. Although the detergent-insolubility of GPI-anchored proteins indicates that lipid rafts are preserved in the erg6 mutant (Sievi et al, 2001;Umebayashi and Nakano, 2003), inappropriate ubiquitination would occur in such altered lipid rafts. Alternatively, polyubiquitination of Tat2p may occur in non-raft domains.…”

Section: Possible Cooperation Of Ubiquitin and Sterol In Protein Sortingmentioning

confidence: 99%

The Roles of Ubiquitin and Lipids in Protein Sorting along the Endocytic Pathway

Umebayashi

2003

Cell Struct. Funct.

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ABSTRACT. After cell surface receptors are internalized for endocytosis, they are accurately sorted in endosomes. Some are recycled to the plasma membrane and others are downregulated by delivery to lysosomes. Evidence is rapidly accumulating that ubiquitination of cargo proteins acts as a sorting signal during endocytosis. Sorting devices that recognize ubiquitin are distributed to various compartments, probably acting in a concerted manner. Cholesterol is enriched in the plasma membrane and endosomes, and is involved in protein sorting by forming microdomains called lipid rafts. Ubiquitin and cholesterol hold the key to control the endocytic sorting, and they are likely acting cooperatively.

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Proteolytic Function of GPI‐Anchored Plasma Membrane Protease Yps1p in the Yeast Vacuole and Golgi

Cited by 33 publications

References 51 publications

Yapsins Are a Family of Aspartyl Proteases Required for Cell Wall Integrity in Saccharomyces cerevisiae

Yapsins Are a Family of Aspartyl Proteases Required for Cell Wall Integrity in Saccharomyces cerevisiae

A Specific Structural Requirement for Ergosterol in Long-chain Fatty Acid Synthesis Mutants Important for Maintaining Raft Domains in Yeast

The Roles of Ubiquitin and Lipids in Protein Sorting along the Endocytic Pathway

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