<i>NPI1</i>, an essential yeast gene involved in induced degradation of Gap1 and Fur4 permeases, encodes the Rsp5 ubiquitin—protein ligase

Hein, Claudine; Springael, Jean–Yves; Volland, Christiane; Haguenauer‐Tsapis, Rosine; André, Brunó

doi:10.1111/j.1365-2958.1995.mmi_18010077.x

Cited by 320 publications

(342 citation statements)

References 37 publications

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“…The most suggestive evidence for a role of ubiquitination as a trigger of endocytosis has been gained from experiments on the ␣-pheromone receptor Ste2 (Hicke and Riezman, 1996). Additional evidence for a role of ubiquitination in endocytosis has been obtained for several other yeast plasma membrane proteins, including the a-factor receptor Ste3 (Roth and Davis, 1996), uracil permease (Fur4) (Galan et al, 1996), the general amino acid permease (Gap1; Hein et al, 1995), and the multidrug transporter Pdr5 (Egner and Kuchler, 1996). Ubiquitination has also been directly implicated in endocytosis and lysosomal degradation of the mammalian growth hormone receptor (Strous et al, 1996).…”

Section: Introductionmentioning

confidence: 90%

Uptake of the ATP-Binding Cassette (ABC) Transporter Ste6 into the Yeast Vacuole Is Blocked in the doa4 Mutant

Losko

Kopp

Kranz

et al. 2001

MBoC

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Previous experiments suggested that trafficking of the a-factor transporter Ste6 of Saccharomyces cerevisiae to the yeast vacuole is regulated by ubiquitination. To define the ubiquitinationdependent step in the trafficking pathway, we examined the intracellular localization of Ste6 in the ubiquitination-deficient doa4 mutant by immunofluorescence experiments, with a Ste6-green fluorescent protein fusion protein and by sucrose density gradient fractionation. We found that Ste6 accumulated at the vacuolar membrane in the doa4 mutant and not at the cell surface. Experiments with a doa4 pep4 double mutant showed that Ste6 uptake into the lumen of the vacuole is inhibited in the doa4 mutant. The uptake defect could be suppressed by expression of additional ubiquitin, indicating that it is primarily the result of a lowered ubiquitin level (and thus of reduced ubiquitination) and not the result of a deubiquitination defect. Based on our findings, we propose that ubiquitination of Ste6 or of a trafficking factor is required for Ste6 sorting into the multivesicular bodies pathway. In addition, we obtained evidence suggesting that Ste6 recycles between an internal compartment and the plasma membrane.

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Section: Introductionmentioning

confidence: 90%

Uptake of the ATP-Binding Cassette (ABC) Transporter Ste6 into the Yeast Vacuole Is Blocked in the doa4 Mutant

Losko

Kopp

Kranz

et al. 2001

MBoC

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“…Strains and Plasmids-S. cerevisiae strains used in this study include the following: JK9 -3da (MATa trp1 his4 leu2-3, 112 ura3-52 rme1 HMLa) (17) and isogenic mutant strains NC86 (doa4⌬::G418 R ), NC23 (doa1⌬::G418 R ), and NC227 (ubi4⌬::G418 R ); RH406 -2A (MAT␣ leu2 trp1 ura3 bar1) and isogenic lcb1 temperature-sensitive strain RH614 -2C (lcb1-100) (18); 27061 (MATa ura3 trp1) and isogenic npi1 strain 27064 (npi1) (19) Ub-myc) and its ubiquitin mutant plasmids, pTer10 (KRR Ub-myc), pTer11 (RKR Ub-myc), pTer12 (RRK Ub-myc), and pTer13 (RRR Ubmyc) (24).…”

Section: Methodsmentioning

confidence: 99%

“…The ACT1 mRNA is shown as a loading control. B and C, Fur4 immunoblotting was performed with an npi1 ubiquitin ligase mutant strain and isogenic control strain (19) and doa4⌬ deubiquitinase mutant strain and isogenic control strain, JK9 -3d. Sensitivity to PHS was measured by streaking cells on yeast extract peptone dextrose (YPD)/ Tergitol medium (1% yeast extract, 2% peptone, 2% glucose, 2% agar, and 0.05% Tergitol, type NP-40), containing PHS or ethanol, with growth at 30°C for 2 days.…”

Section: Fig 3 Phs Induces Fur4 Degradation Via Ubiquitin-dependentmentioning

confidence: 99%

Sphingolipids Signal Heat Stress-induced Ubiquitin-dependent Proteolysis

Chung¹,

Jenkins²,

Hannun³

et al. 2000

Journal of Biological Chemistry

113

106

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Sphingolipids are essential eukaryotic membrane lipids that are structurally and metabolically conserved through evolution. Sphingolipids have also been proposed to regulate eukaryotic stress responses as novel second messengers. Here we show that, in Saccharomyces cerevisiae, phytosphingosine, a putative sphingolipid second messenger, mediates heat stress signaling and activates ubiquitin-dependent proteolysis via the endocytosis vacuolar degradation and 26 S proteasome pathways. Inactivation of serine palmitoyltransferase, a key enzyme in generating endogenous phytosphingosine, prevents proteolysis during heat stress. Addition of phytosphingosine bypasses the requirement for serine palmitoyltransferase and restores proteolysis. Phytosphingosine-induced proteolysis requires multiubiquitin chain formation through the stress-responsive lysine 63 residue of ubiquitin. We propose that heat stress increases phytosphingosine and activates ubiquitin-dependent proteolysis.Sphingolipids are complex lipids containing a sphingoid base, which is a long chain amino base. Sphingolipids comprise indispensable structural components of all known eukaryotic plasma membranes and also regulate signal transduction elements including protein kinase C (1). Sphingosine, ceramide, sphingosine 1-phosphate, and other sphingolipid derivatives are also known to play central roles in apoptosis, cellular senescence, cell cycle regulation, inflammation, tumor development, and intracellular calcium mobilization (2)(3)(4).Despite the growing number of cellular functions regulated by sphingolipids and their derivatives, the molecular mechanisms by which these regulatory functions are executed in mammalian cells are poorly understood (5-7). Being ubiquitous and essential components of eukaryotic plasma membranes, sphingolipids are evolutionarily conserved from yeast to humans (8, 9). The yeast Saccharomyces cerevisiae has several advantages as a model system to study sphingolipid-mediated cellular regulation. First, the basic structure and metabolism of sphingolipids are conserved between yeast and mammals, and yet yeast has only three major species of sphingolipids, whereas mammalian cells may contain more than 300 distinct molecular species (10). Second, yeast is a genetically tractable organism whose genome has been completely sequenced (11). Lastly, many yeast genes encoding sphingolipid biosynthetic and metabolic enzymes have been recently identified (12). The controlled expression of these genes can be exploited to modulate intracellular levels of certain sphingolipids and their derivatives.The LCB1 and LCB2 genes encode serine palmitoyltransferase, which catalyzes the first committed step in yeast sphingolipid biosynthesis, the condensation of L-serine and palmitoyl-CoA to produce 3-ketodihydrosphingosine (KDS) 1 (13,14). Recently, heat stress was shown to increase cellular levels of sphingoid bases (dihydrosphingosine (DHS) and phytosphingosine (PHS)) and ceramides with little effect on the levels of complex sphingolipids (15,16). This in...

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“…Among the substrates for Rsp5-mediated ubiquitylation are the copper transporter Ctr1p (Liu et al, 2007), the zinc transporter Zrt1p (Gitan and Eide, 2000), the general amino acid permease Gap1p (Hein et al, 1995), the uracil permease Fur4p (Galan et al, 1996;Blondel et al, 2004), and the tryptophan permease Tat2p (Beck et al, 1999). Rsp5 is encoded by an essential gene, so we investigated the localization of Ftr1-GFP by epifluorescence microscopy in two different rsp5 strains that each contain a point mutation within the Rsp5 catalytic HECT domain (rsp5-1 and rsp5-smm1; Fisk and Yaffe, 1999), and in control cells expressing a wild-type copy of RSP5.…”

Section: Constitutive Endocytic Recycling Of Fet3-ftr1 In Degradativementioning

confidence: 99%

Opposing Activities of the Snx3-Retromer Complex and ESCRT Proteins Mediate Regulated Cargo Sorting at a Common Endosome

Strochlic

Schmiedekamp

Lee

et al. 2008

MBoC

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Endocytosed proteins are either delivered to the lysosome to be degraded or are exported from the endosomal system and delivered to other organelles. Sorting of the Saccharomyces cerevisiae reductive iron transporter, composed of the Fet3 and Ftr1 proteins, in the endosomal system is regulated by available iron; in iron-starved cells, Fet3-Ftr1 is sorted by Snx3/Grd19 and retromer into a recycling pathway that delivers it back to the plasma membrane, but when starved cells are exposed to iron, Fet3-Ftr1 is targeted to the lysosome-like vacuole and is degraded. We report that iron-induced endocytosis of Fet3-Ftr1 is independent of Fet3-Ftr1 ubiquitylation, and after endocytosis, degradation of Fet3-Ftr1 is mediated by the multivesicular body (MVB) sorting pathway. In mutant cells lacking any component of the ESCRT protein-dependent MVB sorting machinery, the Rsp5 ubiquitin ligase, or in wild-type cells expressing Fet3-Ftr1 lacking cytosolic lysyl ubiquitin acceptor sites, Fet3-Ftr1 is constitutively sorted into the recycling pathway independent of iron status. In the presence and absence of iron, Fet3-Ftr1 transits an endosomal compartment where a subunit of the MVB sorting receptor (Vps27), Snx3/Grd19, and retromer proteins colocalize. We propose that this endosome is where Rsp5 ubiquitylates Fet3-Ftr1 and where the recycling and degradative pathways diverge. INTRODUCTIONThe endocytic pathway is initiated with the internalization of protein and lipid cargo from the plasma membrane. After endocytosis, internalized molecules transit through the endosomal system, a network of interconnected organelles that process and sort cargo molecules back to the plasma membrane, to other organelles, or to lysosomes for degradation. In mammalian cells, early endosomes are pleiomorphic organelles composed of vacuolar domains that contain lumenal vesicles and tubular domains that lead into and emanate from the vacuolar portion. This distinct architecture has functional significance. The tubular elements of the organelle are regions where the majority of internalized plasma membrane proteins and lipids are exported and recycled from the endosomal system via bulk flow and cargo-specific processes (Mayor et al., 1993;Maxfield and McGraw, 2004;Bonifacino and Rojas, 2006). Cargo proteins that are not exported are delivered to lysosomes and many of these are degraded. This occurs via an active, signal-mediated event in which these proteins are targeted to the vacuolar region of the endosome where they are incorporated into vesicles that bud from the limiting membrane into the lumen of the organelle (Piper and Katzmann, 2007). During endosome maturation lumenal vesicles accrue until fusion of the late endosome with the lysosome results in degradation of these vesicles and their contents. A central sorting function of the endosomal system is thus to segregate cargo to be exported from the endosome from cargo to be degraded via lysosomal proteolysis.The core components of the recycling (retrograde) and degradative sorting pathways have be...

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NPI1, an essential yeast gene involved in induced degradation of Gap1 and Fur4 permeases, encodes the Rsp5 ubiquitin—protein ligase

Cited by 320 publications

References 37 publications

Uptake of the ATP-Binding Cassette (ABC) Transporter Ste6 into the Yeast Vacuole Is Blocked in the doa4 Mutant

Uptake of the ATP-Binding Cassette (ABC) Transporter Ste6 into the Yeast Vacuole Is Blocked in the doa4 Mutant

Sphingolipids Signal Heat Stress-induced Ubiquitin-dependent Proteolysis

Opposing Activities of the Snx3-Retromer Complex and ESCRT Proteins Mediate Regulated Cargo Sorting at a Common Endosome

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