Cytoplasmic peptide:<i>N</i>‐glycanase (PNGase) in eukaryotic cells: occurrence, primary structure, and potential functions

Suzuki, Tadashi; Park, Hangil; Lennarz, William J.

doi:10.1096/fj.01-0889rev

Cited by 148 publications

(102 citation statements)

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“…There are two types of cytosolic deglycosylating enzymes that can generate free OSs from glycoproteins (7,8). One is ENGase described in this study, and the other is PNGase (peptide: N-glycanase), which releases a free glycan from glycoprotein͞ glycopeptide by cleaving the amide bond between the proximal GlcNAc residue and the side chain of an asparagine residue (35). Because the gene encoding PNGase (PNG1) has been identified (36), rapid progress regarding functional studies of cytoplasmic PNGase has been made (35).…”

Section: Discussionmentioning

confidence: 99%

“…One is ENGase described in this study, and the other is PNGase (peptide: N-glycanase), which releases a free glycan from glycoprotein͞ glycopeptide by cleaving the amide bond between the proximal GlcNAc residue and the side chain of an asparagine residue (35). Because the gene encoding PNGase (PNG1) has been identified (36), rapid progress regarding functional studies of cytoplasmic PNGase has been made (35). PNGase-mediated deglycosylation of glycoproteins has been observed in various organisms (35).…”

Section: Discussionmentioning

confidence: 99%

“…Because the gene encoding PNGase (PNG1) has been identified (36), rapid progress regarding functional studies of cytoplasmic PNGase has been made (35). PNGase-mediated deglycosylation of glycoproteins has been observed in various organisms (35). On the other hand, whether the cytosolic ENGase can work on glycoproteins in nature remains to be determined.…”

Section: Discussionmentioning

confidence: 99%

“…Although the sequential processing events of free OSs have been well characterized (15)(16)(17)(18)(19), the molecular nature of the enzyme͞transporters involved in this process has not been identified, with the exception of cytosolic PNGase (35). Because free OSs in the lumen of the ER can potentially interfere with the glycan-dependent protein quality control system in the ER (2-4), the rapid clearance of them from the lumen of the ER may be of great importance.…”

Section: Discussionmentioning

confidence: 99%

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Endo-β- N -acetylglucosaminidase, an enzyme involved in processing of free oligosaccharides in the cytosol

Suzuki

Yano

Sugimoto

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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126

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Formation of oligosaccharides occurs both in the cytosol and in the lumen of the endoplasmic reticulum (ER). Luminal oligosaccharides are transported into the cytosol to ensure that they do not interfere with proper functioning of the glycan-dependent quality control machinery in the lumen of the ER for newly synthesized glycoproteins. Once in the cytosol, free oligosaccharides are catabolized, possibly to maximize the reutilization of the component sugars. An endo-␤-N-acetylglucosaminidase (ENGase) is a key enzyme involved in the processing of free oligosaccharides in the cytosol. This enzyme activity has been widely described in animal cells, but the gene encoding this enzyme activity has not been reported. Here, we report the identification of the gene encoding human cytosolic ENGase. After 11 steps, the enzyme was purified 150,000-fold to homogeneity from hen oviduct, and several internal amino acid sequences were analyzed. Based on the internal sequence and examination of expressed sequence tag (EST) databases, we identified the human orthologue of the purified protein.The human protein consists of 743 aa and has no apparent signal sequence, supporting the idea that this enzyme is localized in the cytosol. By expressing the cDNA of the putative human ENGase in COS-7 cells, the enzyme activity in the soluble fraction was enhanced 100-fold over the basal level, confirming that the human gene identified indeed encodes for ENGase. Careful gene database surveys revealed the occurrence of ENGase homologues in Drosophila melanogaster, Caenorhabditis elegans, and Arabidopsis thaliana, indicating the broad occurrence of ENGase in higher eukaryotes. This gene was expressed in a variety of human tissues, suggesting that this enzyme is involved in basic biological processes in eukaryotic cells.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Endo-β- N -acetylglucosaminidase, an enzyme involved in processing of free oligosaccharides in the cytosol

Suzuki

Yano

Sugimoto

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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126

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“…A likely candidate for a cytosolic glycosidase is the peptide N:glycanase (PNGase) implicated in ERAD, which cleaves Nglycan chains from misfolded glycoproteins en route to proteasomal degradation (Suzuki et al, 2002). To test whether PNGase was involved in removing the N-glycan from cytosolic HMG 350 -HA, cells that were treated with ALLN and sterols to promote HMG 350 -HA deglycosylation were incubated, in addition, with increasing concentrations of Z-VADfmk.…”

Section: Deglycosylation Of Dislocated Hmg 350 -Ha Is Stimulated By Smentioning

confidence: 99%

Dislocation of HMG-CoA Reductase and Insig-1, Two Polytopic Endoplasmic Reticulum Proteins, En Route to Proteasomal Degradation

Leichner

Avner

Harats

et al. 2009

MBoC

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The endoplasmic reticulum (ER) glycoprotein HMG-CoA reductase (HMGR) catalyzes the rate-limiting step in sterols biosynthesis. Mammalian HMGR is ubiquitinated and degraded by the proteasome when sterols accumulate in cells, representing the best example for metabolically controlled ER-associated degradation (ERAD). This regulated degradation involves the short-lived ER protein Insig-1. Here, we investigated the dislocation of these ERAD substrates to the cytosol en route to proteasomal degradation. We show that the tagged HMGR membrane region, HMG 350 INTRODUCTIONA key mechanism for maintaining cholesterol homeostasis in mammalian cells involves modulating the stability of 3-hydroxy-3-methylglutaryl CoA reductase (HMGR). This enzyme catalyzes the rate-limiting step in the mevalonate (MVA) pathway in which essential sterols and nonsterol isoprenoids are synthesized (Goldstein and Brown, 1990). In cells deprived of sterols and/or MVA-derived isoprenoids, HMGR is a fairly stable protein that turns over with a half-life of 10 -14 h. Conversely, in cells replenished with MVA pathway products, HMGR degradation is accelerated severalfold and its half-life drops to 1-4 h (Faust et al., 1982;Edwards et al., 1983;Sinensky and Logel, 1983), reflecting one of the highly regulated processes that prevent accumulation of these metabolites to toxic levels.Similar to other proteins of the MVA pathway (Horton et al., 2002), HMGR is controlled also at the transcriptional level by the sterol regulatory element-binding protein (SREBP)-2, which binds to the promoter of the HMGR gene and activates transcription when demands for MVA-derived products increase (Osborne et al., 1985;Vallett et al., 1996). Like its closely related SREBP-1a and SREBP-1c factors, SREBP-2 is synthesized as a large endoplasmic reticulum (ER)-bound precursor whose transcription activation domain must be released from the membrane to function in the nucleus. On increased demand for MVA-derived metabolites, the SREBP precursor is transported by COP-II vesicles to the Golgi, where it is sequentially cleaved at two sites by resident site-1 and site-2 proteases. The liberated transcriptionally active domain enters the nucleus and stimulates the transcription of target genes, including HMGR (Sakai et al., 1996;Nohturfft et al., 1998aNohturfft et al., , 2000. When sterols are abundant and demand for MVA-derived products declines, the transport of the SREBP precursor out from the ER is prevented and transcription ceases (Nohturfft et al., 1999(Nohturfft et al., , 2000. This metabolically regulated traffic of the SREBP precursors critically depends on SREBP cleavage-activating protein (SCAP), a membrane protein with eight transmembranes spans (TMs), which tightly associates with the SREBP precursors and enables the packaging of both proteins in the COP-II vesicles and their transport from the ER to the Golgi Sakai et al., 1997;Nohturfft et al., 1998b Feramisco et al., 2004). This sterol-stimulated binding to Insig(s) masks the transport signal in SCAP and abrogates i...

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Metabolism

Boden¹,

Scapa²,

Kanno³

et al. 2007

Textbook of Hepatology

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Cytoplasmic peptide:N‐glycanase (PNGase) in eukaryotic cells: occurrence, primary structure, and potential functions

Cited by 148 publications

References 75 publications

Endo-β- N -acetylglucosaminidase, an enzyme involved in processing of free oligosaccharides in the cytosol

Endo-β- N -acetylglucosaminidase, an enzyme involved in processing of free oligosaccharides in the cytosol

Dislocation of HMG-CoA Reductase and Insig-1, Two Polytopic Endoplasmic Reticulum Proteins, En Route to Proteasomal Degradation

Metabolism

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