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Szabo Z, Thayer JR, Reusch D, Agroskin Y, Viner R, Rohrer J, Patil SP, Krawitzky M, Huhmer A, Avdalovic N, Khan SH, Liu Y, Pohl C. High Performance Anion Exchange and Hydrophilic Interaction Liquid Chromatography Approaches for Comprehensive Mass Spectrometry-Based Characterization of the N-Glycome of a Recombinant Human Erythropoietin. J Proteome Res 2018; 17:1559-1574. [DOI: 10.1021/acs.jproteome.7b00862] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Zoltan Szabo
- ThermoFisher Scientific, 1228 Titan Way, Sunnyvale, California 94088, United States
| | - James R. Thayer
- ThermoFisher Scientific, 1228 Titan Way, Sunnyvale, California 94088, United States
| | - Dietmar Reusch
- Roche Diagnostics GmbH, 2 Nonnenwald, Penzberg 82377, Germany
| | - Yury Agroskin
- ThermoFisher Scientific, 1228 Titan Way, Sunnyvale, California 94088, United States
| | - Rosa Viner
- ThermoFisher Scientific, 355 River Oaks Parkway, San Jose, California 95134, United States
| | - Jeff Rohrer
- ThermoFisher Scientific, 1214 Oakmead Parkway, Sunnyvale, California 94085, United States
| | - Sachin P. Patil
- ThermoFisher Scientific, 1214 Oakmead Parkway, Sunnyvale, California 94085, United States
| | - Michael Krawitzky
- ThermoFisher Scientific, 355 River Oaks Parkway, San Jose, California 95134, United States
| | - Andreas Huhmer
- ThermoFisher Scientific, 355 River Oaks Parkway, San Jose, California 95134, United States
| | - Nebojsa Avdalovic
- ThermoFisher Scientific, 1228 Titan Way, Sunnyvale, California 94088, United States
| | - Shaheer H. Khan
- ThermoFisher Scientific, 180 Oyster Point Blvd, South San Francisco, California 94080, United States
| | - Yan Liu
- ThermoFisher Scientific, 1228 Titan Way, Sunnyvale, California 94088, United States
| | - Christopher Pohl
- ThermoFisher Scientific, 1228 Titan Way, Sunnyvale, California 94088, United States
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2
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Gupta GS. P-Type Lectins: Cation-Dependent Mannose-6-Phosphate Receptor. ANIMAL LECTINS: FORM, FUNCTION AND CLINICAL APPLICATIONS 2012. [PMCID: PMC7121444 DOI: 10.1007/978-3-7091-1065-2_3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In eukaryotic cells, post-translational modification of secreted proteins and intracellular protein transport between organelles are ubiquitous features. One of the most studied systems is the N-linked glycosylation pathway in the synthesis of secreted glycoproteins (Schrag et al. 2003). The N-linked glycoproteins are subjected to diverse modifications and are transported through ER and Golgi apparatus to their final destinations in- and outside the cell. Incorporation of cargo glycoproteins into transport vesicles is mediated by transmembrane cargo receptors, which have been identified as intracellular lectins. For example, mannose 6-phosphate receptors (Ghosh et al. 2003) function as a cargo receptor for lysosomal proteins in the trans-Golgi network, whereas ERGIC-53 (Zhang et al. 2003) and its yeast orthologs Emp46/47p (Sato and Nakano 2002) are transport lectins for glycoproteins that are transported out of ER.
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Affiliation(s)
- G. S. Gupta
- Department of Biophysics, Punjab University, Chandigarh, India
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3
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Olson LJ, Zhang J, Lee YC, Dahms NM, Kim JJ. Structural basis for recognition of phosphorylated high mannose oligosaccharides by the cation-dependent mannose 6-phosphate receptor. J Biol Chem 1999; 274:29889-96. [PMID: 10514470 DOI: 10.1074/jbc.274.42.29889] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mannose 6-phosphate receptors (MPRs) play an important role in the targeting of newly synthesized soluble acid hydrolases to the lysosome in higher eukaryotic cells. These acid hydrolases carry mannose 6-phosphate recognition markers on their N-linked oligosaccharides that are recognized by two distinct MPRs: the cation-dependent mannose 6-phosphate receptor and the insulin-like growth factor II/cation-independent mannose 6-phosphate receptor. Although much has been learned about the MPRs, it is unclear how these receptors interact with the highly diverse population of lysosomal enzymes. It is known that the terminal mannose 6-phosphate is essential for receptor binding. However, the results from several studies using synthetic oligosaccharides indicate that the binding site encompasses at least two sugars of the oligosaccharide. We now report the structure of the soluble extracytoplasmic domain of a glycosylation-deficient form of the bovine cation-dependent mannose 6-phosphate receptor complexed to pentamannosyl phosphate. This construct consists of the amino-terminal 154 amino acids (excluding the signal sequence) with glutamine substituted for asparagine at positions 31, 57, 68, and 87. The binding site of the receptor encompasses the phosphate group plus three of the five mannose rings of pentamannosyl phosphate. Receptor specificity for mannose arises from protein contacts with the 2-hydroxyl on the terminal mannose ring adjacent to the phosphate group. Glycosidic linkage preference originates from the minimization of unfavorable interactions between the ligand and receptor.
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Affiliation(s)
- L J Olson
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
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4
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Vignon F, Rochefort H. Interactions of pro-cathepsin D and IGF-II on the mannose-6-phosphate/IGF-II receptor. Breast Cancer Res Treat 1992; 22:47-57. [PMID: 1421424 DOI: 10.1007/bf01833333] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The mannose-6-phosphate (Man-6P)/IGF-II receptor is a multifunctional receptor which binds with a high affinity on distinct sites two strikingly different classes of ligands: IGF-II, and Man-6P bearing molecules such as lysosomal enzymes or other biologically relevant ligands (TGF beta precursor, EGF receptor, proliferin...). Binding of each ligand on its cognate site is severely decreased in the presence of the other type of ligand, thus revealing that the two distinct sites are strongly interacting (steric hindrance, conformational change). Any imbalance in ligands and receptor concentration in various pathological situations (transformation, tumor, altered hormonal levels...) is thus likely to perturb their associated biological functions in the targeting and routing of lysosomal enzymes or Man-6P ligands or in the autocrine/paracrine IGF-II--induced cellular responses.
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Affiliation(s)
- F Vignon
- INSERM Unit 148 on "Hormones and Cancer", Montpellier, France
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5
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Affiliation(s)
- T Sato
- Laboratory of Materials Science of Polymers, Department of Polymer Chemistry, Kyoto University, Japan
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6
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Ohya Y, Kobayashi H, Ouchi T. Design of poly(α-malic acid) -5fu-saccharide conjugate exhibiting antitumor activity. ACTA ACUST UNITED AC 1991. [DOI: 10.1016/0923-1137(91)90159-l] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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7
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Tomoda H, Ohsumi Y, Ichikawa Y, Srivastava OP, Kishimoto Y, Lee YC. Binding specificity of D-mannose 6-phosphate receptor of rabbit alveolar macrophages. Carbohydr Res 1991; 213:37-46. [PMID: 1657389 DOI: 10.1016/s0008-6215(00)90596-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The existence of terminal D-mannosyl 6-phosphate groups (Man-6-P) was required (for an inhibitor) to exert a strong inhibitory potency against the binding of bovine serum albumin (BSA) conjugated with 17 molecules of penta-D-mannose 6-phosphate [(M5P)17-BSA] to the Man-6-P receptor in rabbit alveolar macrophages. In addition, the underlying oligosaccharide structures, such as linkage mode between the nonreducing sugar group and the penultimate sugar residue, and the length of sugar chain also affected the inhibitory potency in this system. In general, the oligosaccharides with an alpha-(1----2)-linked Man-6-P unit gave stronger inhibitory potencies than those with an alpha-(1----3)- or alpha-(1----6)-linked Man-6-P unit. Trisaccharides containing a terminal Man-6-P group were more potent inhibitors than disaccharides. A synthetic, branched, and divalent ligand, which does not have a penultimate sugar residue, gave about the same level of inhibitory potency as Man-6-P itself. The "cluster effect" was observed in this system, i.e., as the number of Man-6-P units conjugated to BSA [(Man-6-P)5,5,8, and 46-BSA] increased, the stronger inhibitory potencies were observed with decreasing I50 values of 1.93, 1.36, and 0.0345 microM, respectively. Synthetic divalent oligosaccharides also showed higher inhibitory potencies than the corresponding monovalent oligosaccharides.
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Affiliation(s)
- H Tomoda
- Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218
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8
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Ichikawa Y, Lee YC. Synthesis of a branched glycopeptide derivative containing terminal D-mannose 6-phosphate residues. Carbohydr Res 1990; 198:235-46. [PMID: 2379187 DOI: 10.1016/0008-6215(90)84295-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
A branched glycopeptide derivative incorporating two D-mannose 6-phosphate residues was prepared by coupling 6-aminohexyl 6-O-[bis(2,2,2-trichloroethoxy)phosphinyl]-alpha-D-mannopyranoside with N-acetyl-L-tyrosyl-L-aspart-oyldi-L-alanine followed by reductive deprotection of the phosphate group.
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Affiliation(s)
- Y Ichikawa
- Department of Biology, McCollum-Pratt Institute, Johns Hopkins University, Baltimore, Maryland 21218
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9
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Tanaka Y, Yano S, Okada K, Ishikawa T, Himeno M, Kato K. Lysosomal acid phosphatase is transported via endosomes to lysosomes. Biochem Biophys Res Commun 1990; 166:1176-82. [PMID: 1689571 DOI: 10.1016/0006-291x(90)90990-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Involvement of endosomes in transport of newly synthesized acid phosphatase to lysosomes was investigated using the Golgi fraction (GF1 + 2), enriched in endosomes. The Golgi fraction (GF1 + 2) was prepared from the livers of rats given [35S]methionine and asialofetuin conjugated-horseradish peroxidase (HRP). Newly synthesized acid phosphatase in the endosomes containing internalized asialofetuin-HRP was measured as a loss of the detectable labeled enzyme after 3,3'-diaminobenzidine (DAB) and H2O2 reaction, due to formation of insoluble polymers which reduce protein antigenicity. With this procedure, acid phosphatase was all but undetectable in the Golgi fraction. Thus, newly synthesized acid phosphatase is apparently transported to lysosomes by endosomes.
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Affiliation(s)
- Y Tanaka
- Department of Physiological Chemistry, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
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10
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Himeno M, Fujita H, Noguchi Y, Kono A, Kato K. Isolation and sequencing of a cDNA clone encoding acid phosphatase in rat liver lysosomes. Biochem Biophys Res Commun 1989; 162:1044-53. [PMID: 2764916 DOI: 10.1016/0006-291x(89)90779-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A full length cDNA for acid phosphatase in rat liver lysosomes was isolated and sequenced. The predicted amino acid sequence comprises 423 residues (48,332 Da). A putative signal peptide of 30 residues is followed by the NH2-terminal sequence of lysosomal acid phosphatase (45,096 Da). The deduced NH2-terminal 18-residue sequence is identical with that determined directly for acid phosphatases purified from the rat liver lysosomal membranes. The primary structure deduced for acid phosphatase contains 9 potential N-glycosylation sites and a hydrophobic region which could function as a transmembrane domain. It exhibits 89% and 67% sequence similarities in amino acids and nucleic acids, respectively, to human lysosomal acid phosphatase. The amino acid sequence of the putative transmembrane segment shows a complete similarity to that of the human enzyme. Northern blot hybridization analysis identified a single species of acid phosphatase mRNA (2.2 kbp in length) in rat liver.
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Affiliation(s)
- M Himeno
- Division of Physiological Chemistry, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
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11
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Tong PY, Gregory W, Kornfeld S. Ligand interactions of the cation-independent mannose 6-phosphate receptor. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)83136-2] [Citation(s) in RCA: 142] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
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12
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Dong JM, Prence EM, Sahagian GG. Mechanism for selective secretion of a lysosomal protease by transformed mouse fibroblasts. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)83244-6] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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13
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Dahms NM, Lobel P, Breitmeyer J, Chirgwin JM, Kornfeld S. 46 kd mannose 6-phosphate receptor: cloning, expression, and homology to the 215 kd mannose 6-phosphate receptor. Cell 1987; 50:181-92. [PMID: 2954652 DOI: 10.1016/0092-8674(87)90214-5] [Citation(s) in RCA: 126] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
We have isolated cDNA clones encoding the entire sequence of the bovine 46 kd cation-dependent mannose 6-phosphate (CD Man-6-P) receptor. Translation of CD Man-6-P receptor mRNA in Xenopus laevis oocytes results in a protein that binds specifically to phosphomannan-Sepharose, thus demonstrating that our cDNA clones encode a functional receptor. The deduced 279 amino acid sequence reveals a single polypeptide chain that contains a putative signal sequence and a transmembrane domain. Trypsin digestion of microsomal membranes containing the receptor and the location of the five potential N-linked glycosylation sites indicate that the receptor is a transmembrane protein with an extracytoplasmic amino terminus. This extracytoplasmic domain is homologous to the approximately 145 amino acid long repeating domains present in the 215 kd cation-independent Man-6-P receptor.
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14
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Hoflack B, Fujimoto K, Kornfeld S. The interaction of phosphorylated oligosaccharides and lysosomal enzymes with bovine liver cation-dependent mannose 6-phosphate receptor. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(19)75897-9] [Citation(s) in RCA: 69] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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15
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Donovan MJ, Hart NH. Cortical granule exocytosis is coupled with membrane retrieval in the egg of Brachydanio. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 1986; 237:391-405. [PMID: 3701295 DOI: 10.1002/jez.1402370312] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Activation of the teleost (Brachydanio) fish egg includes the exocytosis of cortical granules, the construction of a mosaic surface consisting of the unfertilized egg plasma membrane and the limiting membranes of the cortical granules, and the appearance of coated and smooth vesicles in the cytoplasm (Donovan and Hart, '82). Unfertilized and activated eggs were incubated in selected extracellular tracers to (1) determine experimentally if cortical granule exocytosis was coupled with the endocytosis of membrane during the cortical reaction, and (2) establish the intracellular pathway(s) by which internalized vesicles were processed. Unfertilized eggs incubated in dechlorinated tap water or Fish Ringer's solution containing either horseradish peroxidase (HRP; 10 mg/ml), native ferritin (12.5 mg/ml), or cationized ferritin (12.5 mg/ml) were activated as judged by cortical granule breakdown and elevation of the chorion. Cells treated with HRP and native ferritin exhibited a delay in cortical granule exocytosis when compared with water-activated eggs lacking the tracer. Each tracer was internalized through the formation of a coated vesicle from a coated pit. Since coated pits appeared to be topographically restricted to the perigranular membrane domain of the mosaic egg surface, their labeling, particularly with cationized ferritin, strongly suggested that the retrieved membrane was of cortical granule origin. Cationized ferritin and concanavalin A (Con A) coupled with either hemocyanin or ferritin labeled the surface of the unactivated egg and both domains of the mosaic egg surface. Transformation of the deep evacuated cortical granule crypt into later profiles of exocytosis was accompanied by increased Con A binding. Within activated egg cortices, HRP reaction product, native ferritin, and cationized ferritin were routinely localized in smooth vesicles, multivesicular bodies, and autophagic vacuoles. Occasionally, each tracer was found in small coated vesicles adjacent to the Golgi and within Golgi cisternae. The intracellular distribution of HRP, native ferritin, and cationized ferritin suggests that internalized membrane is primarily processed by organelles of the lysosomal compartment. A second and less significant pathway is the Golgi complex.
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16
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Baenziger JU. The role of glycosylation in protein recognition. Warner-Lambert Parke-Davis Award lecture. THE AMERICAN JOURNAL OF PATHOLOGY 1985; 121:382-91. [PMID: 3934981 PMCID: PMC1887917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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17
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Interaction of Dictyostelium discoideum lysosomal enzymes with the mammalian phosphomannosyl receptor. The importance of oligosaccharides which contain phosphodiesters. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(17)39430-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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18
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Gabel CA, Kornfeld S. Targeting of beta-glucuronidase to lysosomes in mannose 6-phosphate receptor-deficient MOPC 315 cells. J Cell Biol 1984; 99:296-305. [PMID: 6330127 PMCID: PMC2275628 DOI: 10.1083/jcb.99.1.296] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The murine plasma cell line MOPC 315 efficiently targets newly synthesized acid hydrolases to lysosomes in spite of a marked deficiency in the level of the mannose 6-phosphate receptor (Gabel, C., D. Goldberg, and S. Kornfeld, 1983, Proc. Natl. Acad. Sci. USA, 80:775-779). To better understand the routing of lysosomal enzymes in this cell line, pulse-chase experiments were performed with [2-3H]mannose and [35S]methionine followed by immunoprecipitation of beta-glucuronidase and IgA. By 3 h of chase, essentially all of the newly synthesized beta-glucuronidase had undergone proteolytic processing, suggesting that the molecules had reached lysosomes. At this time 30% of the pulse-labeled IgA was still intracellular. The oligosaccharides on the intracellular IgA were of the high mannose-type, while the secreted IgA contained processed, complex-type oligosaccharides. This indicates that the intracellular IgA was still in the endoplasmic reticulum or an early region of the Golgi complex when all of the beta-glucuronidase had reached lysosomes. Therefore, beta-glucuronidase and IgA must exit from the endoplasmic reticulum or the early Golgi complex at different rates, a finding that is inconsistent with bulk phase movement of these proteins from the endoplasmic reticulum to the trans Golgi complex. The addition of the ionophore monensin greatly slows the rate of IgA secretion from MOPC 315 cells and the molecules secreted have incompletely processed oligosaccharides. In contrast, monensin only slightly delays the transport of newly synthesized beta-glucuronidase to lysosomes and causes no significant alteration in the extent of oligosaccharide phosphorylation, a process that appears to occur in the early (cis) Golgi complex. However, the labeled beta-glucuronidase was deficient in sialylated, phosphorylated hybrid oligosaccharides whose biosynthesis requires the action of late stage oligosaccharide processing enzymes assumed to be localized in the trans Golgi complex.
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19
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Freeze HH, Yeh R, Miller AL, Kornfeld S. Structural analysis of the asparagine-linked oligosaccharides from three lysosomal enzymes of Dictyostelium discoideum. Evidence for an unusual acid-stable phosphodiester. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(17)43745-8] [Citation(s) in RCA: 93] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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20
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Fischer HD, Creek KE, Strisciuglio P, Sly WS. Comparative kinetics of phosphomannosyl receptor-mediated pinocytosis of fibroblast secretion acid hydrolases and glycopeptides prepared from them. J Cell Biochem 1983; 22:69-86. [PMID: 6323494 DOI: 10.1002/jcb.240220202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In a previous report we demonstrated that phosphorylated oligosaccharides isolated from acid hydrolases were subject to pinocytosis by phosphomannosyl receptors present on the cell surface of human fibroblasts [9]. However, limiting quantities of oligosaccharides precluded detailed comparison of the kinetics of pinocytosis of these phosphorylated oligosaccharides to those of the acid hydrolases from which they were derived. In this report we present studies comparing the kinetics of pinocytosis of acid hydrolases from NH4Cl-induced fibroblast secretions with those of concanavalin A-binding glycopeptides prepared from them by pronase digestion. The uptake of both secretion acid hydrolases and 125I-labeled glycopeptides was linear for at least 3 hr, saturable, inhibited competitively by mannose 6-phosphate, and destroyed by prior treatment of the ligand with alkaline phosphatase. The inhibition constants of excess unlabeled glycopeptide for the uptake of 125I-labeled glycopeptides (Ki of 1.5 X 10(-6) M) and for the uptake of secretion acid hydrolases (Ki of 2.2 X 10(-6) M) were remarkably similar. Furthermore, the Ki for mannose 6-phosphate inhibition of pinocytosis of glycopeptide uptake (3 X 10(-5) M) compares closely to that previously determined for the pinocytosis of intact "high-uptake" acid hydrolases (3-6 X 10(-5) M). "High-uptake" fractions of both ligands were prepared and quantified by affinity chromatography on immobilized phosphomannosyl receptors purified from bovine liver. Only 10% of the concanavalin A-binding glycopeptides bound to the immobilized phosphomannosyl receptors, while 80% of the acid hydrolases from which they were prepared bound and were eluted with 10 mM mannose 6-phosphate. However, the fraction of each type of ligand that binds to the immobilized phosphomannosyl receptors accounts for all the uptake activity of that ligand.
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