The importance of trimming reactions on asparagine-linked oligosaccharides for protein quality control

Roth, Jürgen; Zuber, Christian; Guhl, Bruno; Fan, Jing‐Yu; Ziak, Martin

doi:10.1007/s00418-001-0365-z

Cited by 28 publications

(23 citation statements)

References 102 publications

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“…The endoplasmic reticulum (ER) represents a site of quality control of glycoprotein folding. 1,2 Misfolded glycoproteins are recognized and retained by the concerted action of chaperones, lectins, and modifying enzymes such as UDP-glucose:glycoprotein glucosyltransferase and glucosidase II. 3 Glycoproteins failing to achieve their correct conformation might become retrotranslocated to the cytosol 4 and degraded by the ubiquitin-proteasome pathway, a process referred to as ER-associated protein degradation.…”

Section: Mutations In the Water Channel Aquaporin-2 (Aqp2) Can Cause mentioning

confidence: 99%

“…The following antibodies were used: affinity-purified rabbit polyclonal anti-rat AQP2 antibody raised against a synthetic peptide comprising the carboxy terminal residues 254 to 271 of rat AQP2 cross-reactive with human AQP2 (Alomone Labs, Jerusalem, Israel); mouse monoclonal anti-Golgi mannosidase II antibody (Babco, Richmond, CA); mouse monoclonal anti-lysosomal associated membrane protein 1 (LAMP1, clone 1D4B; RDI, Flanders, NJ); Alexa 488-conjugated (Fab) 2 …”

Section: Reagents and Antibodiesmentioning

confidence: 99%

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The Proteasome Is Involved in the Degradation of Different Aquaporin-2 Mutants Causing Nephrogenic Diabetes Insipidus

Hirano

Zuber

Roth

et al. 2003

The American Journal of Pathology

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Mutations in the water channel aquaporin-2 (AQP2) can cause congenital nephrogenic diabetes insipidus. To reveal the possible involvement of the protein quality control system in processing AQP2 mutants, we created an in vitro system of clone 9 hepatocytes stably expressing endoplasmic reticulum-retained T126M AQP2 and misrouted E258K AQP2 as well as wild-type AQP2 and studied their biosynthesis, degradation, and intracellular distribution. Mutant and wild-type AQP2 were synthesized as 29-kd nonglycosylated and 32-kd core-glycosylated forms in the endoplasmic reticulum. The wild-type AQP2 had a t 1/2 of 4.6 hours. Remarkable differences in the degradation kinetics were observed for the glycosylated and nonglycosylated T126M AQP2 (t 1/2 ‫؍‬ 2.0 hours versus 0.9 hours). Moreover, their degradation was depending on proteasomal activity as demonstrated in inhibition studies. Degradation of E258K AQP2 also occurred rapidly (t 1/2 ‫؍‬ 1.8 hours) but in a proteasome-and lysosome-dependent manner. By triple confocal immunofluorescence microscopy misrouting of E258K to lysosomes via the Golgi apparatus could be demonstrated. Notwithstanding the differences in degradation kinetics and subcellular distribution such as endoplasmic reticulum-retention and misrouting to lysosomes, both T126M and E258K AQP2 were efficiently degraded. This implies the involvement of different protein quality control processes in the processing of these AQP2 mutants. The endoplasmic reticulum (ER) represents a site of quality control of glycoprotein folding. 1,2 Misfolded glycoproteins are recognized and retained by the concerted action of chaperones, lectins, and modifying enzymes such as UDP-glucose:glycoprotein glucosyltransferase and glucosidase II. 3 Glycoproteins failing to achieve their correct conformation might become retrotranslocated to the cytosol 4 and degraded by the ubiquitin-proteasome pathway, a process referred to as ER-associated protein degradation. [5][6][7] Quality control of protein folding is of importance in congenital diseases caused by point mutations that result in the synthesis of misfolded glycoproteins. 8 Mutations in the water channel aquaporin-2 (AQP2) can cause nephrogenic diabetes insipidus (NDI), in which patients are unable to concentrate urine in response to the anti-diuretic hormone arginine-vasopressin. 9 -11 If not corrected, this defect results in a deregulated whole-body water homeostasis that is accompanied by various symptoms of dehydration. 12 AQP2 belongs to the large family of AQPs, 13,14 and is a 29-kd polytope membrane protein that contains a single N-glycosylation site and two phosphorylation sites, and is present in the principal cells of renal collecting ducts. 15,16 In states of hypernatremia or hypovolemia, translocation of phosphorylated AQP2 homotetramers from vesicles to the apical plasma membrane of the principal cells is triggered by a signal transduction cascade induced by arginine-vasopressin. 16 -18 Alike to normal human kidney, 19 wild-type (wt) AQP2, when expressed in Xenopus ooc...

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Section: Mutations In the Water Channel Aquaporin-2 (Aqp2) Can Cause mentioning

confidence: 99%

Section: Reagents and Antibodiesmentioning

confidence: 99%

The Proteasome Is Involved in the Degradation of Different Aquaporin-2 Mutants Causing Nephrogenic Diabetes Insipidus

Hirano

Zuber

Roth

et al. 2003

The American Journal of Pathology

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“…It has been pointed out that addition of N-linked carbohydrate is often a necessary step to maintain protein solubility in the ER (19). Trimming of glucose residues is required for interaction of the nascent protein with the lectin-like ER chaperones calnexin (CNX) and calreticulin (CRT) (21)(22)(23). In cells treated with tunicamycin, an inhibitor of N-linked glycosylation, or with castanospermine (CST), an inhibitor of ER glucosidases, mostly inactive LPL is formed, and the inactive LPL protein is retained within the cells (13,14,24).…”

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confidence: 99%

Calreticulin Promotes Folding/Dimerization of Human Lipoprotein Lipase Expressed in Insect Cells (Sf21)

Zhang

Tate

et al. 2003

Journal of Biological Chemistry

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Lipoprotein lipase (LPL) is a non-covalent, homodimeric, N-glycosylated enzyme important for metabolism of blood lipids. LPL is regulated by yet unknown post-translational events affecting the levels of active dimers. On co-expression of LPL with human molecular chaperones, we found that calreticulin had the most pronounced effects on LPL activity, but calnexin was also effective. Calreticulin caused a 9-fold increase in active LPL, amounting to about 50% of the expressed LPL protein. The total expression of LPL protein was increased less than 20%, and the secretion rates for active and inactive LPL were not significantly changed by the chaperone. Thus, the main effect was an increased specific activity of LPL both in cells and media. Chromatography on heparin-Sepharose and sucrose density gradient centrifugation demonstrated that most of the inactive LPL was monomeric and that calreticulin promoted formation of active dimers. Higher oligomers of inactive LPL were present in cell extracts, but only monomers and dimers were secreted to the medium. Interaction between LPL and calreticulin was demonstrated, and the effect of the chaperone was prevented by castanospermine, an inhibitor of N-glycan glucose trimming. Our data indicate an important role of endoplasmic reticulum-based chaperones for the folding/ dimerization of LPL. Lipoprotein lipase (LPL)1 hydrolyzes triglycerides in the circulating plasma lipoproteins, such as chylomicrons and very low density lipoproteins (1-3). The enzyme is produced and secreted mainly by adipocytes and muscle cells, but it is also produced in other cells such as macrophages and certain neurons. LPL is transported by yet unclear mechanisms to the vascular endothelium, where it is attached to cell surfaces through interaction with heparan sulfate proteoglycans (HSPG). The products of lipolysis are taken up for storage or oxidation in adjacent tissues. In addition, LPL can mediate internalization of intact lipoproteins by bridging them to cell surface receptors like the LDL receptor-like protein or HSPG.LPL, along with pancreatic lipase, hepatic lipase (HL), and endothelial lipase, belongs to the gene family of mammalian triglyceride lipases (2, 4). The three-dimensional structure of LPL has not yet been determined. Based on homology with pancreatic lipase, it has been proposed that LPL has two structurally distinct regions, a larger N-terminal domain containing the active site and a smaller C-terminal domain with other important functions, such as binding to lipids, LDL receptorlike protein, and HSPG (5, 6).Catalytically active LPL is a non-covalent, homodimeric glycoprotein (7, 8). In the rough endoplasmic reticulum (ER), human LPL is co-translationally glycosylated at amino acid residues Asn 43 and Asn 359 . Studies using site-directed mutagenesis and inhibitors of transport between ER and Golgi have shown that core glycosylation at residue Asn 43 is necessary for activation and release of LPL from the ER, but glycosylation at Asn 359 is not necessary (9 -11). A number of studies...

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“…The presence of glucosidase II, UGGT and calreticulin in pre-Golgi intermediate compartments (Roth et al, 2002;Zuber et al, 2001) suggests that other compartments of the secretory pathway may also have a role in correct folding and quality control (Roth et al, 2002). In addition, endomannosidase, which localizes to the intermediate compartment and has substrate specificity for Glc 1 -2 Man 9 GlcNAc 2 like glucosidase II, can also act on Glc 3 Man 9 GlcNAc 2 unlike glucosidase II, thus providing an alternative glucosidase II independent pathway (Zuber et al, 2000).…”

Section: Retention Retrieval and Er-associated Degradationmentioning

confidence: 99%

“…In addition, endomannosidase, which localizes to the intermediate compartment and has substrate specificity for Glc 1 -2 Man 9 GlcNAc 2 like glucosidase II, can also act on Glc 3 Man 9 GlcNAc 2 unlike glucosidase II, thus providing an alternative glucosidase II independent pathway (Zuber et al, 2000). However, in contrast to glucosidase II, endomannosidase can also remove the Glc 1 Man residues from monoglucosylated oligosaccharides with trimmed mannose chains (for example, Glc 1 Man 5-8 GlcNAc 2 -structures), suggesting a role for this enzyme in quality control (Roth et al, 2002;Spiro et al, 1996). It is proposed that misfolded Man 8 -glycoproteins may be released from calreticulin in the intermediate compartment by the action of endomannosidase before their degradation (Zuber et al, 2000).…”

Section: Retention Retrieval and Er-associated Degradationmentioning

confidence: 99%

The ER Glycoprotein Quality Control System

Dejgaard

Nicolay²,

Taheri³

et al. 2004

Current Issues in Molecular Biology

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The endoplasmic reticulum (ER) is the major site for folding and sorting of newly synthesized secretory cargo proteins. One central regulator of this process is the quality control machinery, which retains and ultimately disposes of misfolded secretory proteins before they can exit the ER. The ER quality control process is highly effective and mutations in cargo molecules are linked to a variety of diseases. In mammalian cells, a large number of secretory proteins, whether membrane bound or soluble, are asparagine (N)-glycosylated. Recent attention has focused on a sugar transferase, UDP-Glucose: glycoprotein glucosyl transferase (UGGT), which is now recognized as a constituent of the ER quality control machinery. UGGT is capable of sensing the folding state of glycoproteins and attaches a single glucose residue to the Man 9 GlcNAc 2 glycan of incompletely folded or misfolded glycoproteins. This enables misfolded glycoproteins to rebind calnexin and reenter productive folding cycles. Prolonging the time of glucose addition on misfolded glycoproteins ultimately results in either the proper folding of the glycoprotein or its presentation to an ER associated degradation machinery.

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The importance of trimming reactions on asparagine-linked oligosaccharides for protein quality control

Cited by 28 publications

References 102 publications

The Proteasome Is Involved in the Degradation of Different Aquaporin-2 Mutants Causing Nephrogenic Diabetes Insipidus

The Proteasome Is Involved in the Degradation of Different Aquaporin-2 Mutants Causing Nephrogenic Diabetes Insipidus

Calreticulin Promotes Folding/Dimerization of Human Lipoprotein Lipase Expressed in Insect Cells (Sf21)

The ER Glycoprotein Quality Control System

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