Monoubiquitination Is Sufficient To Signal Internalization of the Maltose Transporter in
            <i>Saccharomyces cerevisiae</i>

Lucero, Pilar; Peñalver, Élida; Vela, Laura; Lagunas, Rosario

doi:10.1128/jb.182.1.241-243.2000

Cited by 41 publications

(33 citation statements)

References 26 publications

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“…7) are monoubiquitinated, rather than that a single lysine residue carries a branched multiubiquitin chain. Mono-ubiquitination has been shown to be sufficient for internalization of yeast membrane proteins, such as Ste2p, a G protein-coupled receptor (45), or the maltose transporter, a protein with 12 transmembrane segments (46). Also, ubiquitin conjugation has been shown to promote endocytosis in the absence of any other internalization signal (47).…”

Section: Ubiquitination Of the ␣1 Glyr: A Targeting Signal For Internmentioning

confidence: 99%

Ubiquitination Precedes Internalization and Proteolytic Cleavage of Plasma Membrane-bound Glycine Receptors

Büttner¹,

Sadtler²,

Leyendecker³

et al. 2001

Journal of Biological Chemistry

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The inhibitory glycine receptor (GlyR) in developing spinal neurones is internalized efficiently upon antagonist inhibition. Here we used surface labeling combined with affinity purification to show that homopentameric ␣1 GlyRs generated in Xenopus oocytes are proteolytically nicked into fragments of 35 and 13 kDa upon prolonged incubation. Nicked GlyRs do not exist at the cell surface, indicating that proteolysis occurs exclusively in the endocytotic pathway. Consistent with this interpretation, elevation of the lysosomal pH, but not the proteasome inhibitor lactacystin, prevents GlyR cleavage. Prior to internalization, ␣1 GlyRs are conjugated extensively with ubiquitin in the plasma membrane. Our results are consistent with ubiquitination regulating the endocytosis and subsequent proteolysis of GlyRs residing in the plasma membrane. Ubiquitin-conjugating enzymes thus may have a crucial role in synaptic plasticity by determining postsynaptic receptor numbers.The efficiency of synaptic transmission depends critically on a dense packing of neurotransmitter receptors in the postsynaptic membrane. At fast synapses, ligand-gated ion channels (LGICs) 1 mediate the postsynaptic response. Different lines of evidence indicate that the distribution and density of LGICs in the plasma membrane are regulated tightly. In differentiating muscle fibers, the formation of a densely packed postsynaptic matrix of nicotinic acetylcholine receptors (nAChRs) at the developing motor endplate requires restriction of gene expression to subsynaptic nuclei, efficient internalization and degradation of extrasynaptic receptors, synaptic clustering by rapsyn, and slowing of the turnover of synaptically accumulated nAChRs (1, 2). Inversely, muscle denervation (2) or blockade of neurotransmission by ␣-bungarotoxin (3) causes a loss of nAChRs from the postsynaptic membrane because of an increased rate of protein turnover (4). Because nAChR degradation occurs only after internalization and lysosomal targeting of the receptor protein (4, 5

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Section: Ubiquitination Of the ␣1 Glyr: A Targeting Signal For Internmentioning

confidence: 99%

Ubiquitination Precedes Internalization and Proteolytic Cleavage of Plasma Membrane-bound Glycine Receptors

Büttner¹,

Sadtler²,

Leyendecker³

et al. 2001

Journal of Biological Chemistry

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“…This result is in contrast to other reports (19,20), where overexpressed Myc and x-ray-induced p53 formed multiubiquitin conjugates in a ladder-like fashion. Monoubiquitination has been reported to target membrane-bound proteins for endocytosis, leading to eventual degradation in vacuoles (21,22). However, it is unlikely that Gts1p is degraded in vacuoles, since the protein is located in the supernatant of the cell lysate and the degradation is inhibited by the proteasome inhibitor MG132.…”

Section: Discussionmentioning

confidence: 99%

Regulation of the Gts1p Level by the Ubiquitination System to Maintain Metabolic Oscillations in the Continuous Culture of Yeast

Saito

Mitsui

Hamada

et al. 2002

Journal of Biological Chemistry

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Yeast cells exhibit sustained ultradian oscillations of energy metabolism in coupling with cell cycle and stress resistance oscillations in continuous culture. We have reported that the rhythmic expression of Gts1p is important for the maintenance of ultradian rhythms. Structurally, Gts1p contains sequence motifs similar to N-degron and the ubiquitin association domain, raising the possibility that the Gts1p level is regulated by degradation via ubiquitination. When the lysine residue at the putative ubiquitination site of the N-degron was substituted with arginine, both the protein level and half-life of mutant Gts1p increased. During continuous culture, the protein level of the mutant Gts1p was elevated and did not fluctuate, leading to the disappearance of metabolic oscillation within a day. Furthermore, using three Gts1ps containing mutations in the ubiquitin association domain, we showed that the lower the binding activity of the mutant Gts1ps for polyubiquitin in vitro, the higher the protein level in vivo. Expression of the mutant Gts1ps in the continuous culture resulted in an increase in Gts1p and early loss of the oscillation. Therefore, Gts1p is degraded through conjugation with ubiquitin, and the UBA domain promoted the degradation of ubiquitinated Gts1p, causing a fluctuation in protein level, which is required for the maintenance of metabolic oscillations.In an open system using a bioreactor, yeast cells exhibit sustained ultradian oscillations of energy metabolism in a continuous (chemostat) culture under aerobic and glucose-limited conditions (1-4). The energy metabolism pathway has been proven to be an autogenous oscillator under extreme nonequilibrium energy conditions according to the theory of "dissipative structures" established by Prigogine and others (5-7). In brief, the metabolic pathway oscillates autonomously under the primary control of phosphofructokinase, transferring energy from glucose to NADH, which acts as the feed-forward activator, and then from NADH to ATP, which acts as the feedback inhibitor. After ATP as an inhibitor is consumed as fuel for various ATPases, glucose again begins to enter the glycolytic pathway. The oscillations are detectable as a periodic change in the factors involved in energy metabolism such as dissolved oxygen (DO) 1 levels, CO 2 production, glucose and ethanol concentrations, and amounts of storage carbohydrates. DO oscillation is due to the periodic change between respiratory and respiro-fermentative phases in which oxygen demands are relatively high and low, respectively. DO oscillations arise spontaneously in concert with cell division and are dependent on a high cell density (ϳ5 ϫ 10 8 cells/ml), regulating the cell density throughout the oscillation (8). We have reported that cellular responses to various stress conditions, such as heat, oxidative agents, and cytotoxic compounds, are regulated in concert with metabolic oscillation (8) and that the coupling 2 was disrupted by inactivation of the GTS1 gene (9). Furthermore, we suggested that the rhy...

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“…A number of intracellular defects observed in the npi2/doa4 mutant cells, including strongly impaired proteolysis of some plasma membrane proteins, can be overcome at least partially by restoration of normal intracellular ubiquitin levels (11,30,50,53). Based on this knowledge, we overexpressed ubiquitin in wild-type and npi2/doa4 cells transformed with a multicopy plasmid bearing the ubiquitin gene under the control of the copper-inducible CUP1 promoter.…”

Section: Resultsmentioning

confidence: 99%

Glucose-Induced Monoubiquitination of the Saccharomyces cerevisiae Galactose Transporter Is Sufficient To Signal Its Internalization

Horák

Wolf

2001

J Bacteriol

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In Saccharomyces cerevisiae, the addition of glucose to cells growing on galactose induces internalization of the galactose transporter Gal2p and its subsequent proteolysis in the vacuole. Here we report that the essential step in Gal2p down-regulation is its ubiquitination through the Ubc1p-Ubc4p-Ubc5p triad of ubiquitinconjugating enzymes and Npi1/Rsp5p ubiquitin-protein ligase. Moreover, Gal2p appears to be stabilized in mutant cells defective in the ubiquitin-hydrolase Npi2p/Doa4p, and the mutant phenotype can be reversed by overexpression of ubiquitin. An analysis of the fate of Gal2p in cells overexpressing wild-type ubiquitin as well as its variants incompetent to form polyubiquitin chains showed that monoubiquitination of Gal2p is sufficient to signal internalization of the protein into the endocytic pathway.The covalent linkage of ubiquitin to a variety of eukaryotic proteins targets them for degradation. This process involves sequential transfer of the ubiquitin moiety to specific lysine residues of substrate proteins via an E1-E2-E3 enzyme (ubiquitin-activating enzyme, ubiquitin-conjugating enzyme, and ubiquitin-protein ligase) thioester cascade and culminates in formation of an isopeptide bond between the C-terminal glycine of ubiquitin and the ⑀-amino group of lysine(s) on the substrate protein. Specificity in substrate recognition resides largely at the level of E3Јs, and an additional degree of combinatorial specificity probably results from specific E2-E3 interactions. Attachment of ubiquitin to substrate proteins has distinct mechanistic roles in two completely different intracellular proteolytic pathways. Ubiquitination of short-lived cytosolic and nuclear proteins, as well as proteins that undergo endoplasmic reticulum-associated degradation, marks them for hydrolysis by the multicatalytic, multisubunit protease, the 26S proteasome (15,18,20,37,38). For most of the 26S proteasome substrates, the attachment of a polyubiquitin chain in which at least four ubiquitin molecules must be linked by amide bonds between Lys48 of ubiquitin molecules and the C-terminal carboxyl group of the next following ubiquitin facilitates their binding to the proteasome (15,20,37,54). Ubiquitination of many plasma membrane receptors and nutrient transporters, however, signals their internalization into the endocytic pathway and subsequent proteolysis in the vacuole (5,16,43). For all short-lived plasma membrane proteins examined to date, a single ubiquitin moiety or a very short ubiquitin chain appears to suffice to trigger their endocytotic uptake. These plasma membrane proteins are often internalized constitutively. Modulation of the rate of their internalization, induced by a change in nutrient availability, usually from less desirable nitrogen or carbon sources or starvation conditions to preferred sources or rich medium, by binding of their own substrates, or by cell stress, plays the primary role in controlling nutrient uptake (21). Because the ubiquitin itself is a long-lived protein in the yeast Saccharomyces...

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Monoubiquitination Is Sufficient To Signal Internalization of the Maltose Transporter in Saccharomyces cerevisiae

Cited by 41 publications

References 26 publications

Ubiquitination Precedes Internalization and Proteolytic Cleavage of Plasma Membrane-bound Glycine Receptors

Ubiquitination Precedes Internalization and Proteolytic Cleavage of Plasma Membrane-bound Glycine Receptors

Regulation of the Gts1p Level by the Ubiquitination System to Maintain Metabolic Oscillations in the Continuous Culture of Yeast

Glucose-Induced Monoubiquitination of the Saccharomyces cerevisiae Galactose Transporter Is Sufficient To Signal Its Internalization

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