Yet1p–Yet3p interacts with Scs2p–Opi1p to regulate ER localization of the Opi1p repressor

Wilson, Joshua D.; Thompson, Sarah L.; Barlowe, Charles

doi:10.1091/mbc.e10-07-0559

Cited by 18 publications

(20 citation statements)

References 55 publications

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“…The ability of opi1⌬ to suppress the inositol auxotrophy of the ulp2⌬ cells raised the possibility that the absence of Ulp2 prevents normal transcriptional induction of INO1 on medium lacking inositol. As a first test of this idea, we determined whether an increased dosage of the INO1 gene could enhance growth of ulp2⌬ cells grown in the absence of inositol (46). Indeed, substantial suppression of inositol auxotrophy in ulp2⌬ cells was observed (Fig.…”

Section: Resultsmentioning

confidence: 99%

Desumoylation of the Endoplasmic Reticulum Membrane VAP Family Protein Scs2 by Ulp1 and SUMO Regulation of the Inositol Synthesis Pathway

Felberbaum

Wilson

Cheng

et al. 2012

Molecular and Cellular Biology

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Posttranslational protein modification by the ubiquitin-like SUMO protein is critical to eukaryotic cell regulation, but much remains unknown regarding its operation and substrates. Here we report that specific mutations in the Saccharomyces cerevisiae Ulp1 SUMO protease, including its coiled-coil (CC) domain, lead to the accumulation of distinct sumoylated proteins in vivo. A prominent ϳ50-kDa sumoylated protein accumulates in a Ulp1 CC mutant. The protein was identified as Scs2, an endoplasmic reticulum (ER) membrane protein that regulates phosphatidylinositol synthesis and lipid trafficking. Mutation of lysine 180 of Scs2 abolishes its sumoylation. Notably, impairment of either cellular sumoylation or cellular desumoylation mechanisms inhibits cell growth in the absence of inositol and exacerbates the inositol auxotrophy caused by deletion of SCS2. Mutants lacking the Ulp2 SUMO protease are the most severely affected, and this defect was traced to the mutants' impaired ability to induce transcription of INO1, which encodes the rate-limiting enzyme of inositol biosynthesis. Conversely, inositol starvation induces a striking change in the profiles of total cellular SUMO conjugates. These results provide the first evidence of cross-regulation between the SUMO and inositol pathways, including the sumoylation of an ER membrane protein central to phospholipid synthesis and phosphoinositide signaling. The SUMO (small ubiquitin-related modifier) proteins are a family of protein modifiers conserved from the yeast Saccharomyces cerevisiae to humans. Modification of a protein by SUMO (sumoylation) has a variety of outcomes, including alterations of its localization, stability, or interaction with other molecules (18). Increasingly, SUMO is being identified as a key coordinator of protein interaction networks, and disruption to sumoylation has been linked to a variety of disorders, including many cancers and neurodegenerative diseases (25, 41).The yeast S. cerevisiae expresses a single SUMO protein called Smt3. Smt3 is synthesized as an inactive precursor; the three C-terminal residues are removed to yield mature Smt3, which terminates with a pair of Gly residues. Following precursor cleavage, Smt3 enters an enzymatic cascade involving a series of enzymes designated E1, E2, and E3. The heterodimeric E1-activating enzyme Uba2-Aos1 first forms a high-energy thioester bond with the C terminus of Smt3 (22). Activated Smt3 is then transferred to the active-site cysteine of the E2 enzyme Ubc9 (20), from which it is then conjugated to a lysine side chain in a substrate (21). Smt3-substrate conjugation is usually assisted by one of several E3 protein ligases (21, 50). Additional Smt3 proteins can be appended to previously conjugated Smt3 molecules, generating a polySUMO chain.Sumoylation is reversible, and substrates can be desumoylated by specific proteases, termed ubiquitin-like protein-specific proteases (ULPs) (10). S. cerevisiae has two SUMO proteases, Ulp1 and Ulp2, which cleave Smt3 from distinct sets of substrates (29,31...

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Section: Resultsmentioning

confidence: 99%

Desumoylation of the Endoplasmic Reticulum Membrane VAP Family Protein Scs2 by Ulp1 and SUMO Regulation of the Inositol Synthesis Pathway

Felberbaum

Wilson

Cheng

et al. 2012

Molecular and Cellular Biology

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“…1). In addition, we constructed and tested a diploid strain, OPI1 ffat /OPI1, to determine whether the OPI1 ffat mutation was dominant or recessive in terms of its growth in the presence and absence of inositol and choline at 30 from the native promoter of OPI1 and contribute proportionately to the phenotype of the diploid.…”

Section: The Scs2⌬ and Opi1mentioning

confidence: 99%

“…Both scs2⌬ and opi1⌬ mutants exhibit complex, pleiotropic phenotypes, related to lipid metabolism and gene regulation (19,(27)(28)(29)(30). The yeast SCS2 gene was originally isolated as a high copy suppressor of choline sensitivity (39), a phenotype associated with an uncharacterized dominant mutation, CSE1 (31).…”

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confidence: 99%

Interaction between repressor Opi1p and ER membrane protein Scs2p facilitates transit of phosphatidic acid from the ER to mitochondria and is essential for INO1 gene expression in the presence of choline

Gaspar¹,

Chang²,

Jesch

et al. 2017

Journal of Biological Chemistry

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In the yeast Saccharomyces cerevisiae, the Opi1p repressor controls the expression of INO1 via the Opi1p/Ino2p-Ino4p regulatory circuit. Inositol depletion favors Opi1p interaction with both Scs2p and phosphatidic acid at the endoplasmic reticulum (ER) membrane. Inositol supplementation, however, favors the translocation of Opi1p from the ER into the nucleus, where it interacts with the Ino2p-Ino4p complex, attenuating transcription of INO1. A strain devoid of Scs2p (scs2⌬) and a mutant, OPI1FFAT, lacking the ability to interact with Scs2p were utilized to examine the specific role(s) of the Opi1p-Scs2p interaction in the regulation of INO1 expression and overall lipid metabolism. Loss of the Opi1p-Scs2p interaction reduced INO1 expression and conferred inositol auxotrophy. Moreover, inositol depletion in strains lacking this interaction resulted in Opi1p being localized to sites of lipid droplet formation, coincident with increased synthesis of triacylglycerol. Supplementation of choline to inositol-depleted growth medium led to decreased TAG synthesis in all three strains. However, in strains lacking the Opi1p-Scs2p interaction, Opi1p remained in the nucleus, preventing expression of INO1. These data support the conclusion that a specific pool of phosphatidic acid, associated with lipid droplet formation in the perinuclear ER, is responsible for the initial rapid exit of Opi1p from the nucleus to the ER and is required for INO1 expression in the presence of choline. Moreover, the mitochondria-specific phospholipid, cardiolipin, was significantly reduced in both strains compromised for Opi1p-Scs2p interaction, indicating that this interaction is required for the transfer of phosphatidic acid from the ER to the mitochondria for cardiolipin synthesis.

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“…4B and data not shown). Studies in yeast suggested that the yeast homolog of BAP31-BAP29, the Yet1-Yet3 complex, interacts with yeast VAP-Scs2; therefore, these interactions are evolutionarily conserved (29). Overall, our analysis and recently published MS data highlighted two main groups of VAPB-MSP (direct or indirect)-binding proteins, one composed of components of the UPR and a cluster of ERAD and cytosolic protein degradation machinery (ATF6, FAF1, VCP, BAP31, and Derlin-1).…”

Section: Vapb Interactions With Erad Componentsmentioning

confidence: 99%

“…Opi1 regulates Ino1 activity, a key element in phospholipid synthesis. Scs2 also interacts with the ER-localized proteostasis regulators Yet1p-Yet3p (29). The relation between VAP, UPR, and proteostasis regulation is conserved in mammals.…”

mentioning

confidence: 99%

VAMP-associated Proteins (VAP) as Receptors That Couple Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Proteostasis with Lipid Homeostasis

Ernst

Shome

et al. 2016

Journal of Biological Chemistry

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Yet1p–Yet3p interacts with Scs2p–Opi1p to regulate ER localization of the Opi1p repressor

Abstract: A major phospholipid regulatory circuit in yeast is controlled by Scs2p, an ER membrane protein that binds the transcriptional repressor protein Opi1p. Here we show that the Yet1p–Yet3p complex acts in derepression of INO1 through physical association with Scs2p–Opi1p.

Cited by 18 publications

References 55 publications

Desumoylation of the Endoplasmic Reticulum Membrane VAP Family Protein Scs2 by Ulp1 and SUMO Regulation of the Inositol Synthesis Pathway

Desumoylation of the Endoplasmic Reticulum Membrane VAP Family Protein Scs2 by Ulp1 and SUMO Regulation of the Inositol Synthesis Pathway

Interaction between repressor Opi1p and ER membrane protein Scs2p facilitates transit of phosphatidic acid from the ER to mitochondria and is essential for INO1 gene expression in the presence of choline

VAMP-associated Proteins (VAP) as Receptors That Couple Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Proteostasis with Lipid Homeostasis

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