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Peng J, Alam S, Radhakrishnan K, Mariappan M, Rudolph MG, May C, Dierks T, von Figura K, Schmidt B. Eukaryotic formylglycine-generating enzyme catalyses a monooxygenase type of reaction. FEBS J 2015; 282:3262-74. [DOI: 10.1111/febs.13347] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Revised: 06/03/2015] [Accepted: 06/11/2015] [Indexed: 01/24/2023]
Affiliation(s)
- Jianhe Peng
- Department of Cellular Biochemistry; University of Göttingen; Germany
| | - Sarfaraz Alam
- Department of Cellular Biochemistry; University of Göttingen; Germany
| | - Karthikeyan Radhakrishnan
- Department of Cellular Biochemistry; University of Göttingen; Germany
- Department of Chemistry, Biochemistry I; Bielefeld University; Germany
| | | | | | - Caroline May
- Department of Medical Proteomics/Bioanalytics; Medizinisches Proteom-Center; Ruhr-University Bochum; Germany
| | - Thomas Dierks
- Department of Chemistry, Biochemistry I; Bielefeld University; Germany
| | - Kurt von Figura
- Department of Cellular Biochemistry; University of Göttingen; Germany
| | - Bernhard Schmidt
- Department of Cellular Biochemistry; University of Göttingen; Germany
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Kalus I, Salmen B, Viebahn C, von Figura K, Schmitz D, D'Hooge R, Dierks T. Differential involvement of the extracellular 6-O-endosulfatases Sulf1 and Sulf2 in brain development and neuronal and behavioural plasticity. J Cell Mol Med 2010; 13:4505-21. [PMID: 20394677 PMCID: PMC4515066 DOI: 10.1111/j.1582-4934.2008.00558.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The extracellular sulfatases Sulf1 and Sulf2 remove specific 6-O-sulfate groups from heparan sulfate, thereby modulating numerous signalling pathways underlying development and homeostasis. In vitro data have suggested that the two enzymes show functional redundancy. To elucidate their in vivo functions and to further address the question of a putative redundancy, we have generated Sulf1- and Sulf2-deficient mice. Phenotypic analysis of these animals revealed higher embryonic lethality of Sulf2 knockout mice, which can be associated with neuroanatomical malformations during embryogenesis. Sulf1 seems not to be essential for developmental or postnatal viability, as mice deficient in this sulfatase show no overt phenotype. However, neurite outgrowth deficits were observed in hippocampal and cerebellar neurons of both mutant mouse lines, suggesting that not only Sulf2 but also Sulf1 function plays a role in the developing nervous system. Behavioural analysis revealed differential deficits with regard to cage activity and spatial learning for Sulf1- and Sulf2-deficient mouse lines. In addition, Sulf1-specific deficits were shown for synaptic plasticity in the CA1 region of the hippocampus, associated with a reduced spine density. These results reveal that Sulf1 and Sulf2 fulfil non-redundant functions in vivo in the development and maintenance of the murine nervous system.
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Affiliation(s)
- Ina Kalus
- Department of Chemistry, Biochemistry I, Bielefeld University, Bielefeld, Germany
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Dierks T, Schlotawa L, Frese MA, Radhakrishnan K, von Figura K, Schmidt B. Molecular basis of multiple sulfatase deficiency, mucolipidosis II/III and Niemann–Pick C1 disease — Lysosomal storage disorders caused by defects of non-lysosomal proteins. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research 2009; 1793:710-25. [DOI: 10.1016/j.bbamcr.2008.11.015] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2008] [Revised: 11/11/2008] [Accepted: 11/24/2008] [Indexed: 12/11/2022]
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Chapuy B, Tikkanen R, Mühlhausen C, Wenzel D, von Figura K, Höning S. AP-1 and AP-3 Mediate Sorting of Melanosomal and Lysosomal Membrane Proteins into Distinct Post-Golgi Trafficking Pathways. Traffic 2008; 9:1157-72. [DOI: 10.1111/j.1600-0854.2008.00745.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Mariappan M, Radhakrishnan K, Dierks T, Schmidt B, von Figura K. ERp44 Mediates a Thiol-independent Retention of Formylglycine-generating Enzyme in the Endoplasmic Reticulum. J Biol Chem 2008; 283:6375-83. [DOI: 10.1074/jbc.m709171200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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Mariappan M, Gande SL, Radhakrishnan K, Schmidt B, Dierks T, von Figura K. The non-catalytic N-terminal extension of formylglycine-generating enzyme is required for its biological activity and retention in the endoplasmic reticulum. J Biol Chem 2008; 283:11556-64. [PMID: 18305113 DOI: 10.1074/jbc.m707858200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Formylglycine-generating enzyme (FGE) catalyzes the oxidation of a specific cysteine residue in nascent sulfatase polypeptides to formylglycine (FGly). This FGly is part of the active site of all sulfatases and is required for their catalytic activity. Here we demonstrate that residues 34-68 constitute an N-terminal extension of the FGE catalytic core that is dispensable for in vitro enzymatic activity of FGE but is required for its in vivo activity in the endoplasmic reticulum (ER), i.e. for generation of FGly residues in nascent sulfatases. In addition, this extension is needed for the retention of FGE in the ER. Fusing a KDEL retention signal to the C terminus of FGE is sufficient to mediate retention of an N-terminally truncated FGE but not sufficient to restore its biological activity. Fusion of FGE residues 1-88 to secretory proteins resulted in ER retention of the fusion protein. Moreover, when fused to the paralog of FGE (pFGE), which itself lacks FGly-generating activity, the FGE extension (residues 34-88) of this hybrid construct led to partial restoration of the biological activity of co-expressed N-terminally truncated FGE. Within the FGE N-terminal extension cysteine 52 is critical for the biological activity. We postulate that this N-terminal region of FGE mediates the interaction with an ER component to be identified and that this interaction is required for both the generation of FGly residues in nascent sulfatase polypeptides and for retention of FGE in the ER.
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Affiliation(s)
- Malaiyalam Mariappan
- Zentrum für Biochemie und Molekulare Zellbiologie, Abteilung Biochemie II, Universität Göttingen, Heinrich-Düker-Weg 12, 37073 Göttingen, Germany
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Gande SL, Mariappan M, Schmidt B, Pringle TH, von Figura K, Dierks T. Paralog of the formylglycine-generating enzyme--retention in the endoplasmic reticulum by canonical and noncanonical signals. FEBS J 2008; 275:1118-30. [PMID: 18266766 DOI: 10.1111/j.1742-4658.2008.06271.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Formylglycine-generating enzyme (FGE) catalyzes in newly synthesized sulfatases the oxidation of a specific cysteine residue to formylglycine, which is the catalytic residue required for sulfate ester hydrolysis. This post-translational modification occurs in the endoplasmic reticulum (ER), and is an essential step in the biogenesis of this enzyme family. A paralog of FGE (pFGE) also localizes to the ER. It shares many properties with FGE, but lacks formylglycine-generating activity. There is evidence that FGE and pFGE act in concert, possibly by forming complexes with sulfatases and one another. Here we show that human pFGE, but not FGE, is retained in the ER through its C-terminal tetrapeptide PGEL, a noncanonical variant of the classic KDEL ER-retention signal. Surprisingly, PGEL, although having two nonconsensus residues (PG), confers efficient ER retention when fused to a secretory protein. Inducible coexpression of pFGE at different levels in FGE-expressing cells did not significantly influence the kinetics of FGE secretion, suggesting that pFGE is not a retention factor for FGE in vivo. PGEL is accessible at the surface of the pFGE structure. It is found in 21 mammalian species with available pFGE sequences. Other species carry either canonical signals (eight mammals and 26 nonmammals) or different noncanonical variants (six mammals and six nonmammals). Among the latter, SGEL was tested and found to also confer ER retention. Although evolutionarily conserved for mammalian pFGE, the PGEL signal is found only in one further human protein entering the ER. Its consequences for KDEL receptor-mediated ER retrieval and benefit for pFGE functionality remain to be fully resolved.
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Affiliation(s)
- Santosh Lakshmi Gande
- Zentrum für Biochemie und Molekulare Zellbiologie, Abteilung Biochemie II, Universität Göttingen, Germany
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Hellbusch CC, Sperandio M, Frommhold D, Yakubenia S, Wild MK, Popovici D, Vestweber D, Gröne HJ, von Figura K, Lübke T, Körner C. Golgi GDP-fucose Transporter-deficient Mice Mimic Congenital Disorder of Glycosylation IIc/Leukocyte Adhesion Deficiency II. J Biol Chem 2007; 282:10762-72. [PMID: 17276979 DOI: 10.1074/jbc.m700314200] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Modification of glycoproteins by the attachment of fucose residues is widely distributed in nature. The importance of fucosylation has recently been underlined by identification of the monogenetic inherited human disease "congenital disorder of glycosylation IIc," also termed "leukocyte adhesion deficiency II." Due to defective Golgi GDP-fucose transporter (SLC35C1) activity, patients show a hypofucosylation of glycoproteins and present clinically with mental and growth retardation, persistent leukocytosis, and severe infections. To investigate effects induced by the loss of fucosylated structures in different organs, we generated a mouse model for the disease by inactivating the Golgi GDP-transporter gene (Slc35c1). Lectin binding studies revealed a tremendous reduction of fucosylated glycoconjugates in tissues and isolated cells from Slc35c1(-/-) mice. Fucose treatment of cells from different organs led to partial normalization of the fucosylation state of glycoproteins, thereby indicating an alternative GDP-fucose transport mechanism. Slc35c1-deficient mice presented with severe growth retardation, elevated postnatal mortality rate, dilatation of lung alveoles, and hypocellular lymph nodes. In vitro and in vivo leukocyte adhesion and rolling assays revealed a severe impairment of P-, E-, and L-selectin ligand function. The diversity of these phenotypic aspects demonstrates the broad general impact of fucosylation in the mammalian organism.
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Affiliation(s)
- Christina C Hellbusch
- Department of Pediatrics, Division of Inborn Metabolic Diseases, Section of Neonatology, University Children's Hospital, Im Neuenheimer Feld 153, 69120 Heidelberg, Germany
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Affiliation(s)
- Kurt von Figura
- Department of Biochemistry, University of Göttingen, Göttingen, Germany.
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Schlotawa L, Steinfeld R, Figura KV, Dierks T, Gärtner J. Molecular analysis ofSUMF1 mutations: stability and residual activity of mutant formylglycine-generating enzyme determine disease severity in multiple sulfatase deficiency. Hum Mutat 2007; 29:205. [DOI: 10.1002/humu.9515] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Lamanna W, Baldwin R, Padva M, Kalus I, ten Dam G, van Kuppevelt T, Gallagher J, von Figura K, Dierks T, Merry C. Heparan sulfate 6-O-endosulfatases: discrete in vivo activities and functional co-operativity. Biochem J 2006; 400:63-73. [PMID: 16901266 PMCID: PMC1635445 DOI: 10.1042/bj20060848] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
HS (heparan sulfate) is essential for normal embryonic development. This requirement is due to the obligatory role for HS in the signalling pathways of many growth factors and morphogens that bind to sulfated domains in the HS polymer chain. The sulfation patterning of HS is determined by a complex interplay of Golgi-located N- and O-sulfotransferases which sulfate the heparan precursor and cell surface endosulfatases that selectively remove 6-O-sulfates from mature HS chains. In the present study we generated single or double knock-out mice for the two murine endosulfatases mSulf1 and mSulf2. Detailed structural analysis of HS from mSulf1-/- fibroblasts showed a striking increase in 6-O-sulfation, which was not seen in mSulf2-/- HS. Intriguingly, the level of 6-O-sulfation in the double mSulf1-/-/2-/- HS was significantly higher than that observed in the mSulf1-/- counterpart. These data imply that mSulf1 and mSulf2 are functionally co-operative. Unlike their avian orthologues, mammalian Sulf activities are not restricted to the highly sulfated S-domains of HS. Mitogenesis assays with FGF2 (fibroblast growth factor 2) revealed that Sulf activity decreases the activating potential of newly-synthesized HS, suggesting an important role for these enzymes in cell growth regulation in embryonic and adult tissues.
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Affiliation(s)
- William C. Lamanna
- *Department of Chemistry, Biochemistry I, Bielefeld University, Universitätsstrasse 25, 33615 Bielefeld, Germany
- †Department of Biochemistry II, University of Goettingen, Heinrich-Düker-Weg 12, 37073 Goettingen, Germany
| | - Rebecca J. Baldwin
- ‡University of Manchester and Cancer Research UK Department of Medical Oncology, Christie Hospital NHS Trust, Manchester M20 4BX, U.K
| | - Michael Padva
- †Department of Biochemistry II, University of Goettingen, Heinrich-Düker-Weg 12, 37073 Goettingen, Germany
| | - Ina Kalus
- *Department of Chemistry, Biochemistry I, Bielefeld University, Universitätsstrasse 25, 33615 Bielefeld, Germany
| | - Gerdy ten Dam
- §Department Biochemistry 280, Nijmegen Center for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Toin H. van Kuppevelt
- §Department Biochemistry 280, Nijmegen Center for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - John T. Gallagher
- ‡University of Manchester and Cancer Research UK Department of Medical Oncology, Christie Hospital NHS Trust, Manchester M20 4BX, U.K
| | - Kurt von Figura
- †Department of Biochemistry II, University of Goettingen, Heinrich-Düker-Weg 12, 37073 Goettingen, Germany
| | - Thomas Dierks
- *Department of Chemistry, Biochemistry I, Bielefeld University, Universitätsstrasse 25, 33615 Bielefeld, Germany
- To whom correspondence should be addressed (email or )
| | - Catherine L. R. Merry
- ‡University of Manchester and Cancer Research UK Department of Medical Oncology, Christie Hospital NHS Trust, Manchester M20 4BX, U.K
- To whom correspondence should be addressed (email or )
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Deuschl F, Kollmann K, von Figura K, Lübke T. Molecular characterization of the hypothetical 66.3-kDa protein in mouse: Lysosomal targeting, glycosylation, processing and tissue distribution. FEBS Lett 2006; 580:5747-52. [PMID: 17007843 DOI: 10.1016/j.febslet.2006.09.029] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2006] [Revised: 09/06/2006] [Accepted: 09/14/2006] [Indexed: 10/24/2022]
Abstract
Recently, we and others identified the 66.3-kDa protein as one of several putative novel lysosomal matrix proteins by analyzing mannose 6-phosphate receptors binding proteins [Kollmann K., Mutenda K.E., Balleininger M., Eckermann E., von Figura K., Schmidt B., Lübke T. (2005) Identification of novel lysosomal matrix proteins by proteome analysis. Proteomics 5(15), 3966-3678, Sleat D.E., Lackland H., Wang Y., Sohar I., Xiao G., Li H., Lobel P. (2005) The human brain mannose 6-phosphate glycoproteome: a complex mixture composed of multiple isoforms of many soluble lysosomal proteins. Proteomics. 5(6), 1520-1532]. Here, we describe the expression of the mouse 66.3-kDa protein in HT1080 cells in which it is synthesized as a precursor of about 75kDa and subsequently processed by limited proteolysis to mature polypeptides accumulating in the lysosomal compartment. The lysosomal localisation of the endogenous 66.3-kDa protein was verified by indirect immunofluorescence in mouse embryonic fibroblasts and by subcellular fractionation of tyloxapol-filled mouse liver lysosomes. Northern blot analysis reveals high transcriptional levels in testis, liver and kidney, whereas Western blot analysis shows high protein levels in brain, heart, lung and spleen. Interestingly, in mouse the endogenous 66.3-kDa protein is processed in a highly tissue-dependent manner to mature forms.
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Affiliation(s)
- Florian Deuschl
- Zentrum Biochemie und Molekulare Zellbiologie, Abteilung Biochemie II, Georg-August Universität Göttingen, Heinrich-Düker-Weg 12, D-37073Göttingen, Germany
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Thiel C, Lübke T, Matthijs G, von Figura K, Körner C. Targeted disruption of the mouse phosphomannomutase 2 gene causes early embryonic lethality. Mol Cell Biol 2006; 26:5615-20. [PMID: 16847317 PMCID: PMC1592760 DOI: 10.1128/mcb.02391-05] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mutations in the cytosolic enzyme phosphomannomutase 2 (PMM2), which catalyzes the conversion of mannose-6-phosphate to mannose-1-phosphate, cause the most common form of congenital disorders of glycosylation, termed CDG-Ia. It is an inherited multisystemic disease with severe neurological impairment. To study the pathophysiology of CDG-Ia and to investigate possible therapeutic approaches, we generated a mouse model for CDG-Ia by targeted disruption of the Pmm2 gene. Heterozygous mutant mice appeared normal in development, gross anatomy, and fertility. In contrast, embryos homozygous for the Pmm2-null allele were recovered in embryonic development at days 2.5 to 3.5. These results indicate that Pmm2 is essential for early development of mice. Mating experiments of heterozygous mice with wild-type mice could further show that transmission of the female Pmm2-null allele is impaired.
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Affiliation(s)
- Christian Thiel
- Universitaetskinderklinik Heidelberg, Abteilung I, Friedrich Karls Universitaet Heidelberg, Im Neuenheimer Feld 153, 69120 Heidelberg, Germany.
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Stypmann J, Janssen PML, Prestle J, Engelen MA, Kögler H, Lüllmann-Rauch R, Eckardt L, von Figura K, Landgrebe J, Mleczko A, Saftig P. LAMP-2 deficient mice show depressed cardiac contractile function without significant changes in calcium handling. Basic Res Cardiol 2006; 101:281-91. [PMID: 16604439 DOI: 10.1007/s00395-006-0591-6] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2003] [Accepted: 02/15/2006] [Indexed: 10/24/2022]
Abstract
OBJECTIVE Mutations in the highly glycosylated lysosome associated membrane protein-2 (LAMP-2) cause, as recently shown, familial Danon disease with mental retardation, mild myopathy and fatal cardiomyopathy. Extent and basis of the contractile dysfunction is not completely understood. METHODS In LAMP-2 deficient mice, we investigated cardiac function in vivo using Doppler-echocardiography and contractile function in vitro in isolated myocardial trabeculae. RESULTS LAMP-2 deficient mice displayed reduced ejection fraction (EF) (58.9+/-3.4 vs. 80.7+/-5.1%, P<0.05) and reduced cardiac output (8.3+/-3.1 vs. 14.7+/-3.6 ml/min, P<0.05) as compared to wild-type controls. Isolated multicellular muscle preparations from LAMP-2 deficient mice confirmed depressed force development (3.2+/-0.6 vs. 8.4+/-0.9 mN/mm2, P<0.01). All groups showed similar force-frequency behaviour when normalised to baseline force. Post-rest potentiation was significantly depressed at intervals>15 s in LAMP-2 deficient mice (P<0.05). Although attenuated in absolute force development, the normalised inotropic response to increased calcium and beta-adrenoreceptor stimulation was unaltered. Electron microscopic analysis revealed autophagic vacuoles in LAMP-2 deficient cardiomyocytes. Protein analysis showed unaltered levels of SERCA2a, calsequestrin and phospholamban. CONCLUSIONS Cardiac contractile function in LAMP-2 deficient mice as a model for Danon disease is significantly attenuated. The occurrence of autophagic vacuoles in LAMP-2 deficient myocytes is likely to be causal for the depressed contractile function resulting in an attenuated cardiac pump reserve.
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Affiliation(s)
- Jörg Stypmann
- Department of Cardiology and Angiology, University Hospital Münster, Münster, Germany.
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Kollmann K, Mutenda KE, Balleininger M, Eckermann E, von Figura K, Schmidt B, Lübke T. Identification of novel lysosomal matrix proteins by proteome analysis. Proteomics 2006; 5:3966-78. [PMID: 16145712 DOI: 10.1002/pmic.200401247] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The lysosomal matrix is estimated to contain about 50 different proteins. Most of the matrix proteins are acid hydrolases that depend on mannose 6-phosphate receptors (MPR) for targeting to lysosomes. Here, we describe a comprehensive proteome analysis of MPR-binding proteins from mouse. Mouse embryonic fibroblasts defective in both MPR (MPR 46-/- and MPR 300-/-) are known to secrete the lysosomal matrix proteins. Secretions of these cells were affinity purified using an affinity matrix derivatized with MPR46 and MPR300. In the protein fraction bound to the affinity matrix and eluted with mannose 6-phosphate, 34 known lysosomal matrix proteins, 4 candidate proteins of the lysosomal matrix and 4 non-lysosomal contaminants were identified by mass spectrometry after separation by two-dimensional gel electrophoresis or by multidimensional protein identification technology. For 3 of the candidate proteins, mammalian ependymin-related protein-2 (MERP-2), retinoid-inducible serine carboxypeptidase (RISC) and the hypothetical 66.3-kDa protein we could verify that C-terminally tagged forms bound in an M6P-dependent manner to an MPR-affinity matrix and were internalized via MPR-mediated endocytosis. Hence these 3 proteins are likely to represent hitherto unrecognized lysosomal matrix proteins.
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Affiliation(s)
- Katrin Kollmann
- Zentrum Biochemie und Molekulare Zellbiologie, Abteilung Biochemie II, Georg-August Universität Göttingen, Göttingen, Germany
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Koike M, Shibata M, Waguri S, Yoshimura K, Tanida I, Kominami E, Gotow T, Peters C, von Figura K, Mizushima N, Saftig P, Uchiyama Y. Participation of autophagy in storage of lysosomes in neurons from mouse models of neuronal ceroid-lipofuscinoses (Batten disease). Am J Pathol 2006; 167:1713-28. [PMID: 16314482 PMCID: PMC1613187 DOI: 10.1016/s0002-9440(10)61253-9] [Citation(s) in RCA: 258] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
In cathepsin D-deficient (CD-/-) and cathepsins B and L double-deficient (CB-/-CL-/-) mice, abnormal vacuolar structures accumulate in neurons of the brains. Many of these structures resemble autophagosomes in which part of the cytoplasm is retained but their precise nature and biogenesis remain unknown. We show here how autophagy contributes to the accumulation of these vacuolar structures in neurons deficient in cathepsin D or both cathepsins B and L by demonstrating an increased conversion of the molecular form of MAP1-LC3 for autophagosome formation from the cytosolic form (LC3-I) to the membrane-bound form (LC3-II). In both CD-/- and CB-/-CL-/- mouse brains, the membrane-bound LC3-II form predominated whereas MAP1-LC3 signals accumulated in granular structures located in neuronal perikarya and axons of these mutant brains and were localized to the membranes of autophagosomes, evidenced by immunofluorescence microscopy and freeze-fracture-replica immunoelectron microscopy. Moreover, as in CD-/- neurons, autofluorescence and subunit c of mitochondrial ATP synthase accumulated in CB-/-CL-/- neurons. This suggests that not only CD-/- but also CB-/-CL-/- mice could be useful animal models for neuronal ceroid-lipofuscinosis/Batten disease. These data strongly argue for a major involvement of autophagy in the pathogenesis of Batten disease/lysosomal storage disorders.
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Affiliation(s)
- Masato Koike
- Department of Cell Biology and Neurosciences, Osaka University Graduate School of Medicine, Suita, Japan
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D'Hooge R, Lüllmann-Rauch R, Beckers T, Balschun D, Schwake M, Reiss K, von Figura K, Saftig P. Neurocognitive and psychotiform behavioral alterations and enhanced hippocampal long-term potentiation in transgenic mice displaying neuropathological features of human alpha-mannosidosis. J Neurosci 2006; 25:6539-49. [PMID: 16014715 PMCID: PMC6725435 DOI: 10.1523/jneurosci.0283-05.2005] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Mice with alpha-mannosidase gene inactivation provide an experimental model for alpha-mannosidosis, a lysosomal storage disease with severe neuropsychological and psychopathological complications. Neurohistological alterations in these mice were similar to those in patients and included vacuolations and axonal spheroids in the CNS and peripheral nervous system. Vacuolation was most prominent and evenly distributed in neuronal perikarya of the hippocampal CA2 and CA3 regions, whereas CA1 and dentate gyrus were weakly or not affected. Field potential recordings from CA1 region in hippocampal slices showed enhanced theta burst-induced long-term potentiation (LTP) in alpha-mannosidase-deficient mice. Longitudinal assessment in age-matched alpha-mannosidase-deficient and wild-type littermates, using an extended test battery, demonstrated a neurocognitive and psychotiform profile that may relate to the psychopathological alterations in clinical alpha-mannosidosis. Brainstem auditory-evoked potentials and basic neuromotor abilities were not impaired and did not deteriorate with age. Exploratory and conflict tests revealed consistent decreases in exploratory activity and emotional blunting in the knock-out group. alpha-Mannosidosis mice were also impaired in aversively motivated learning and acquisition of signal-shock associations. Acquisition and reversal learning in the water maze task, passive avoidance learning in the step-through procedure, as well as emotional response conditioning in an operant procedure were all impaired. Acquisition or shaping of an appetitive instrumental conditioning task was unchanged. Appetitive odor discrimination learning was only marginally impaired during shaping, whereas both the discrimination and reversal subtasks were normal. We propose that prominent storage and enhanced LTP in hippocampus have contributed to these specific behavioral alterations in alpha-mannosidase-deficient mice.
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Affiliation(s)
- Rudi D'Hooge
- Laboratory of Biological Psychology, University of Leuven, B-3000 Leuven, Belgium.
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Roeser D, Preusser-Kunze A, Schmidt B, Gasow K, Wittmann JG, Dierks T, von Figura K, Rudolph MG. A general binding mechanism for all human sulfatases by the formylglycine-generating enzyme. Proc Natl Acad Sci U S A 2006; 103:81-6. [PMID: 16368756 PMCID: PMC1324989 DOI: 10.1073/pnas.0507592102] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2005] [Indexed: 11/18/2022] Open
Abstract
The formylglycine (FGly)-generating enzyme (FGE) uses molecular oxygen to oxidize a conserved cysteine residue in all eukaryotic sulfatases to the catalytically active FGly. Sulfatases degrade and remodel sulfate esters, and inactivity of FGE results in multiple sulfatase deficiency, a fatal disease. The previously determined FGE crystal structure revealed two crucial cysteine residues in the active site, one of which was thought to be implicated in substrate binding. The other cysteine residue partakes in a novel oxygenase mechanism that does not rely on any cofactors. Here, we present crystal structures of the individual FGE cysteine mutants and employ chemical probing of wild-type FGE, which defined the cysteines to differ strongly in their reactivity. This striking difference in reactivity is explained by the distinct roles of these cysteine residues in the catalytic mechanism. Hitherto, an enzyme-substrate complex as an essential cornerstone for the structural evaluation of the FGly formation mechanism has remained elusive. We also present two FGE-substrate complexes with pentamer and heptamer peptides that mimic sulfatases. The peptides isolate a small cavity that is a likely binding site for molecular oxygen and could host reactive oxygen intermediates during cysteine oxidation. Importantly, these FGE-peptide complexes directly unveil the molecular bases of FGE substrate binding and specificity. Because of the conserved nature of FGE sequences in other organisms, this binding mechanism is of general validity. Furthermore, several disease-causing mutations in both FGE and sulfatases are explained by this binding mechanism.
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Affiliation(s)
- Dirk Roeser
- Department of Molecular Structural Biology, University of Göttingen, Justus-von-Liebig-Weg 11, D-37077 Göttingen, Germany
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19
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Koduru S, Vegiraju SR, Nadimpalli SK, von Figura K, Pohlmann R, Dennes A. The early vertebrate Danio rerio Mr 46000 mannose-6-phosphate receptor: biochemical and functional characterisation. Dev Genes Evol 2005; 216:133-43. [PMID: 16362416 DOI: 10.1007/s00427-005-0043-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2005] [Accepted: 11/03/2005] [Indexed: 10/25/2022]
Abstract
Mannose-6-phosphate receptors (MPRs) have been identified in a wide range of species from humans to invertebrates such as molluscs. A characteristic of all MPRs is their common property to recognize mannose-6-phosphate residues that are labelling lysosomal enzymes and to mediate their targeting to lysosomes in mammalian cells by the corresponding receptor proteins. We present here the analysis of full-length sequences for MPR 46 from zebrafish (Danio rerio) and its functional analysis. This is the first non-mammalian MPR 46 to be characterised. The amino acid sequences of the zebrafish MPR 46 displays 70% similarity to the human MPR 46 protein. In particular, all essential cysteine residues, the transmembrane domain as well as the cytoplasmic tail residues harbouring the signals for endocytosis and Golgi-localizing, gamma-ear-containing, ARF-binding protein (GGA)-mediated sorting at the trans-Golgi network, are highly conserved. The zebrafish MPR 46 has the arginine residue known to be essential for mannose-6-phosphate binding and other additional characteristic residues of the mannose-6-phosphate ligand-binding pocket. Like the mammalian MPR 46, zebrafish MPR 46 binds to the multimeric mannose-6-phosphate ligand phosphomannan and can rescue the missorting of lysosomal enzymes in mammalian MPR-deficient cells. The conserved C-terminal acidic dileucine motif (DxxLL) in the cytoplasmic domain of zebrafish MPR 46 essential for the interaction of the GGAs with the receptor domains interacts with the human GGA1-VHS domain. Interestingly, the serine residue suggested to regulate the interaction between the tail and the GGAs in a phosphorylation-dependent manner is substituted by a proline residue in fish.
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Affiliation(s)
- Suresh Koduru
- Protein Biochemistry Laboratory, Department of Biochemistry, University of Hyderabad, Hyderabad 500 046, India
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20
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Willenborg M, Schmidt CK, Braun P, Landgrebe J, von Figura K, Saftig P, Eskelinen EL. Mannose 6-phosphate receptors, Niemann-Pick C2 protein, and lysosomal cholesterol accumulation. J Lipid Res 2005; 46:2559-69. [PMID: 16177447 DOI: 10.1194/jlr.m500131-jlr200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Niemann-Pick disease type C (NPC), caused by mutations in the NPC1 gene or the NPC2 gene, is characterized by the accumulation of unesterified cholesterol and other lipids in endo/lysosomal compartments. NPC2 is a small, soluble, lysosomal protein that is targeted to this compartment via a mannose 6-phosphate-inhibitable pathway. To obtain insight into the roles of mannose 6-phosphate receptors (MPRs) in NPC2 targeting, we here examine the trafficking and function of NPC2 in fibroblast lines deficient in one or both of the two MPRs, MPR46 and MPR300. We demonstrate that either MPR alone is sufficient to transport NPC2 to the endo/lysosomal compartment, although MPR300 seems to be more efficient than MPR46. In the absence of both MPRs, NPC2 is secreted into the culture medium, and only a small amount of intracellular NPC2 can be detected, mainly in the endoplasmic reticulum. This leads to massive accumulation of unesterified cholesterol in the endo/lysosomal compartment of the MPR46/300-deficient fibroblasts, a phenotype similar to that of the NPC patient fibroblasts. In addition, we observed an upregulation of NPC1 protein and mRNA in the MPR-double-deficient cells. Taken together, our results suggest that the lysosomal targeting of NPC2 is strictly dependent on MPRs in fibroblasts.
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Affiliation(s)
- Marion Willenborg
- Institute of Biochemistry, University of Kiel, D-24098 Kiel, Germany
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21
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Shimizu T, Hayashi Y, Yamasaki R, Yamada J, Zhang J, Ukai K, Koike M, Mine K, von Figura K, Peters C, Saftig P, Fukuda T, Uchiyama Y, Nakanishi H. Proteolytic degradation of glutamate decarboxylase mediates disinhibition of hippocampal CA3 pyramidal cells in cathepsin D-deficient mice. J Neurochem 2005; 94:680-90. [PMID: 15992379 DOI: 10.1111/j.1471-4159.2005.03250.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Although of clinical importance, little is known about the mechanism of seizure in neuronal ceroid lipofuscinosis (NCL). In the present study, we have attempted to elucidate the mechanism underlying the seizure of cathepsin D-deficient (CD-/-) mice that show a novel type of lysosomal storage disease with a phenotype resembling late infantile NCL. In hippocampal slices prepared from CD-/- mice at post-natal day (P)24, spontaneous burst discharges were recorded from CA3 pyramidal cells. At P24, the mean amplitude of IPSPs after stimulation of the mossy fibres was significantly smaller than that of wild-type mice, which was substantiated by the decreased level of gamma-aminobutyric acid (GABA) contents in the hippocampus measured by high-performance liquid chromatography (HPLC). At this stage, activated microglia were found to accumulate in the pyramidal cell layer of the hippocampal CA3 subfield of CD-/- mice. However, there was no significant change in the numerical density of GABAergic interneurons in the CA3 subfield of CD-/- mice at P24, estimated by counting the number of glutamate decarboxylase (GAD) 67-immunoreactive somata. In the hippocampus and the cortex of CD-/- mice at P24, some GABAergic interneurons displayed extremely high somatic granular immunoreactivites for GAD67, suggesting the lysosomal accumulation of GAD67. GAD67 levels in axon terminals abutting on to perisomatic regions of hippocampal CA3 pyramidal cells was not significantly changed in CD-/- mice even at P24, whereas the total protein levels of GAD67 in both the hippocampus and the cortex of CD-/- mice after P24 were significantly decreased as a result of degradation. Furthermore, the recombinant human GAD65/67 was rapidly digested by the lysosomal fraction prepared from the whole brain of wild-type and CD-/- mice. These observations strongly suggest that the reduction of GABA contents, presumably because of lysosomal degradation of GAD67 and lysosomal accumulation of its degraded forms, are responsible for the dysfunction of GABAergic interneurons in the hippocampal CA3 subfield of CD-/- mice.
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Affiliation(s)
- Tokiko Shimizu
- Laborarory of Oral Aging Science, Faculty of Dental Sciences, Kyushu University, Fukuoka, Japan
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22
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Dierks T, Dickmanns A, Preusser-Kunze A, Schmidt B, Mariappan M, von Figura K, Ficner R, Rudolph MG. Molecular basis for multiple sulfatase deficiency and mechanism for formylglycine generation of the human formylglycine-generating enzyme. Cell 2005; 121:541-552. [PMID: 15907468 DOI: 10.1016/j.cell.2005.03.001] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2004] [Revised: 02/10/2005] [Accepted: 03/02/2005] [Indexed: 11/27/2022]
Abstract
Sulfatases are enzymes essential for degradation and remodeling of sulfate esters. Formylglycine (FGly), the key catalytic residue in the active site, is unique to sulfatases. In higher eukaryotes, FGly is generated from a cysteine precursor by the FGly-generating enzyme (FGE). Inactivity of FGE results in multiple sulfatase deficiency (MSD), a fatal autosomal recessive syndrome. Based on the crystal structure, we report that FGE is a single-domain monomer with a surprising paucity of secondary structure and adopts a unique fold. The effect of all 18 missense mutations found in MSD patients is explained by the FGE structure, providing a molecular basis of MSD. The catalytic mechanism of FGly generation was elucidated by six high-resolution structures of FGE in different redox environments. The structures allow formulation of a novel oxygenase mechanism whereby FGE utilizes molecular oxygen to generate FGly via a cysteine sulfenic acid intermediate.
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Affiliation(s)
- Thomas Dierks
- Department of Biochemistry II, University of Göttingen, D-37073 Göttingen, Germany
| | - Achim Dickmanns
- Department of Molecular Structural Biology, University of Göttingen, D-37077 Göttingen, Germany
| | | | - Bernhard Schmidt
- Department of Biochemistry II, University of Göttingen, D-37073 Göttingen, Germany
| | - Malaiyalam Mariappan
- Department of Biochemistry II, University of Göttingen, D-37073 Göttingen, Germany
| | - Kurt von Figura
- Department of Biochemistry II, University of Göttingen, D-37073 Göttingen, Germany.
| | - Ralf Ficner
- Department of Molecular Structural Biology, University of Göttingen, D-37077 Göttingen, Germany
| | - Markus Georg Rudolph
- Department of Molecular Structural Biology, University of Göttingen, D-37077 Göttingen, Germany.
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23
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Sugie K, Noguchi S, Kozuka Y, Arikawa-Hirasawa E, Tanaka M, Yan C, Saftig P, von Figura K, Hirano M, Ueno S, Nonaka I, Nishino I. Autophagic vacuoles with sarcolemmal features delineate Danon disease and related myopathies. J Neuropathol Exp Neurol 2005; 64:513-22. [PMID: 15977643 DOI: 10.1093/jnen/64.6.513] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Among the autophagic vacuolar myopathies (AVMs), a subgroup is characterized pathologically by unusual autophagic vacuoles with sarcolemmal features (AVSF) and includes Danon disease and X-linked myopathy with excessive autophagy. The diagnostic importance and detailed morphologic features of AVSF in different AVMs have not been well established, and the mechanism of AVSF formation is not known. To address these issues, we have performed detailed histologic studies of myopathies with AVSF and other AVMs. In Danon disease and related AVMs, at the light microscopic level, autophagic vacuoles appeared to be accumulations of lysosomes, which, by electron microscopy consisted of clusters of autophagic vacuoles, indicative of autolysosomes. Some autolysosomes were surrounded by membranes with sarcolemmal proteins, acetylcholinesterase activity, and basal lamina. In Danon disease, the number of fibers with AVSF increased linearly with age while the number with autolysosomal accumulations decreased slightly, suggesting that AVSF are produced secondarily in response to autolysosomes. Most of the AVSF form enclosed spaces, indicating that the vacuolar membranes may be formed in situ rather than through sarcolemmal indentation. This unique intracytoplasmic membrane structure was not found in other AVMs. In conclusion, AVSF with acetylcholinesterase activity are autolysosomes surrounded by secondarily generated intracytoplasmic sarcolemma-like structure and delineates a subgroup of AVMs.
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Affiliation(s)
- Kazuma Sugie
- Department of Neuromuscular Research, National Institute of Neuroscience, National Hospital for Mental Nervous and Muscular Disorders, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan
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24
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Mariappan M, Preusser-Kunze A, Balleininger M, Eiselt N, Schmidt B, Gande SL, Wenzel D, Dierks T, von Figura K. Expression, localization, structural, and functional characterization of pFGE, the paralog of the Calpha-formylglycine-generating enzyme. J Biol Chem 2005; 280:15173-9. [PMID: 15708861 DOI: 10.1074/jbc.m413698200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
pFGE is the paralog of the formylglycine-generating enzyme (FGE), which catalyzes the oxidation of a specific cysteine to Calpha-formylglycine, the catalytic residue in the active site of sulfatases. The enzymatic activity of sulfatases depends on this posttranslational modification, and the genetic defect of FGE causes multiple sulfatase deficiency. The structural and functional properties of pFGE were analyzed. The comparison with FGE demonstrates that both share a tissue-specific expression pattern and the localization in the lumen of the endoplasmic reticulum. Both are retained in the endoplasmic reticulum by a saturable mechanism. Limited proteolytic cleavage at similar sites indicates that both also share a similar three-dimensional structure. pFGE, however, is lacking the formylglycine-generating activity of FGE. Although overexpression of FGE stimulates the generation of catalytically active sulfatases, overexpression of pFGE has an inhibitory effect. In vitro pFGE interacts with sulfatase-derived peptides but not with FGE. The inhibitory effect of pFGE on the generation of active sulfatases may therefore be caused by a competition of pFGE and FGE for newly synthesized sulfatase polypeptides.
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Affiliation(s)
- Malaiyalam Mariappan
- Institut für Biochemie und Molekulare Zellbiologie, Abteilung Biochemie II, Universität Göttingen, Germany
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25
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Dickmanns A, Schmidt B, Rudolph MG, Mariappan M, Dierks T, von Figura K, Ficner R. Crystal structure of human pFGE, the paralog of the Calpha-formylglycine-generating enzyme. J Biol Chem 2005; 280:15180-7. [PMID: 15687489 DOI: 10.1074/jbc.m414317200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In eukaryotes, sulfate esters are degraded by sulfatases, which possess a unique Calpha-formylglycine residue in their active site. The defect in post-translational formation of the Calpha-formylglycine residue causes a severe lysosomal storage disorder in humans. Recently, FGE (formylglycine-generating enzyme) has been identified as the protein required for this specific modification. Using sequence comparisons, a protein homologous to FGE was found and denoted pFGE (paralog of FGE). pFGE binds a sulfatase-derived peptide bearing the FGE recognition motif, but it lacks formylglycine-generating activity. Both proteins belong to a large family of pro- and eukaryotic proteins containing the DUF323 domain, a formylglycine-generating enzyme domain of unknown three-dimensional structure. We have crystallized the glycosylated human pFGE and determined its crystal structure at a resolution of 1.86 A. The structure reveals a novel fold, which we denote the FGE fold and which therefore serves as a paradigm for the DUF323 domain. It is characterized by an asymmetric partitioning of secondary structure elements and is stabilized by two calcium cations. A deep cleft on the surface of pFGE most likely represents the sulfatase polypeptide binding site. The asymmetric unit of the pFGE crystal contains a homodimer. The putative peptide binding site is buried between the monomers, indicating a biological significance of the dimer. The structure suggests the capability of pFGE to form a heterodimer with FGE.
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Affiliation(s)
- Achim Dickmanns
- Abteilung Molekulare Strukturbiologie, Institut für Mikrobiologie und Genetik, Georg-August-Universität, Justus-von-Liebig Weg 9, D-37077 Göttingen, Germany
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26
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Preusser-Kunze A, Mariappan M, Schmidt B, Gande SL, Mutenda K, Wenzel D, von Figura K, Dierks T. Molecular characterization of the human Calpha-formylglycine-generating enzyme. J Biol Chem 2005; 280:14900-10. [PMID: 15657036 DOI: 10.1074/jbc.m413383200] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calpha-formylglycine (FGly) is the catalytic residue in the active site of sulfatases. In eukaryotes, it is generated in the endoplasmic reticulum by post-translational modification of a conserved cysteine residue. The FGly-generating enzyme (FGE), performing this modification, is an endoplasmic reticulum-resident enzyme that upon overexpression is secreted. Recombinant FGE was purified from cells and secretions to homogeneity. Intracellular FGE contains a high mannose type N-glycan, which is processed to the complex type in secreted FGE. Secreted FGE shows partial N-terminal trimming up to residue 73 without loosing catalytic activity. FGE is a calcium-binding protein containing an N-terminal (residues 86-168) and a C-terminal (residues 178-374) protease-resistant domain. The latter is stabilized by three disulfide bridges arranged in a clamp-like manner, which links the third to the eighth, the fourth to the seventh, and the fifth to the sixth cysteine residue. The innermost cysteine pair is partially reduced. The first two cysteine residues are located in the sequence preceding the N-terminal protease-resistant domain. They can form intramolecular or intermolecular disulfide bonds, the latter stabilizing homodimers. The C-terminal domain comprises the substrate binding site, as evidenced by yeast two-hybrid interaction assays and photocross-linking of a substrate peptide to proline 182. Peptides derived from all known human sulfatases served as substrates for purified FGE indicating that FGE is sufficient to modify all sulfatases of the same species.
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Affiliation(s)
- Andrea Preusser-Kunze
- Institut für Biochemie und Molekulare Zellbiologie, Abteilung Biochemie II, Universität Göttingen, Heinrich-Düker-Weg 12, 37073 Göttingen, Germany
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27
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Abstract
Cytotoxic T lymphocytes (CTL) play an important role in the rejection of allogeneic cells and organs. CTL secrete granzymes and perforin as cytotoxic effector molecules. The mannose 6-phosphate receptor (Mpr)300 has been reported to function as receptor for granzyme B on target cells and to be essential for the rejection of allogeneic cells in vivo. Using mouse embryonal fibroblasts from Mpr300 and Mpr46 knockout mice, we show that both Mpr 300 and Mpr46 are dispensable on target cells for lysis and apoptosis mediated by alloreactive CTL in vitro and for allorejection in vivo. In agreement with a postulated function of Mpr300 as a tumor suppressor gene, deficiency of Mpr300 appears to promote cellular proliferation and tumorigenicity but not resistance to allorejection.
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Affiliation(s)
- Ralf Dressel
- Division of Immunogenetics, University of Göttingen, Heirich-Duker-Weg 12, 37073 Göttingen, Germany.
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28
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Roces DP, Lüllmann-Rauch R, Peng J, Balducci C, Andersson C, Tollersrud O, Fogh J, Orlacchio A, Beccari T, Saftig P, von Figura K. Efficacy of enzyme replacement therapy in -mannosidosis mice: a preclinical animal study. Hum Mol Genet 2004; 13:1979-88. [PMID: 15269179 DOI: 10.1093/hmg/ddh220] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Alpha-mannosidosis is a lysosomal storage disorder which manifests itself in the excessive storage of mannose-containing oligosaccharides in the lysosomes of multiple peripheral tissues and in the brain. Here we report on the correction of storage in a mouse model of alpha-mannosidosis after intravenous administration of lysosomal acid alpha-mannosidase (LAMAN) from bovine kidney, and human and mouse recombinant LAMAN. The bovine and the human enzyme were barely phosphorylated, whereas the bulk of the mouse LAMAN contained mannose 6-phosphate recognition markers. The clearance decreased from bovine to human to mouse LAMAN with plasma half-times of 4, 8 and 12 min, respectively. The apparent half-life of the internalized enzyme was dependent on the enzyme source as well as tissue type and varied between 3 and 16 h. The corrective effect on the storage of neutral oligosaccharides was time-, tissue- and dose-dependent, and the effects were observed to be transient. After a single dose of LAMAN the maximum corrective effect was observed between 2 and 6 days after injection. In general the corrective effect of the human LAMAN was higher than that of the mouse LAMAN and lowest for the bovine LAMAN. Injection of 250 mU human LAMAN/g body weight followed by a subsequent injection 3.5 days later was sufficient to clear liver, kidney and heart from neutral oligosaccharides. Surprisingly a decrease in mannose containing oligosaccharides was also observed in the brain, with storage levels reported at <30% than that found in controls. These data clearly underline the efficacy of enzyme replacement therapy for the correction of storage in alpha-mannosidosis and suggest that this treatment can substantially decrease storage in the brain.
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Affiliation(s)
- Diego Prieto Roces
- Georg-August-Univeresität Göttingen, Abt. Biochemie II, Heinrich-Düker-Weg 12, 37073 Göttingen, Germany
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29
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Eskelinen EL, Schmidt CK, Neu S, Willenborg M, Fuertes G, Salvador N, Tanaka Y, Lüllmann-Rauch R, Hartmann D, Heeren J, von Figura K, Knecht E, Saftig P. Disturbed cholesterol traffic but normal proteolytic function in LAMP-1/LAMP-2 double-deficient fibroblasts. Mol Biol Cell 2004; 15:3132-45. [PMID: 15121881 PMCID: PMC452571 DOI: 10.1091/mbc.e04-02-0103] [Citation(s) in RCA: 195] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2004] [Revised: 04/13/2004] [Accepted: 04/15/2004] [Indexed: 01/11/2023] Open
Abstract
Mice double deficient in LAMP-1 and -2 were generated. The embryos died between embryonic days 14.5 and 16.5. An accumulation of autophagic vacuoles was detected in many tissues including endothelial cells and Schwann cells. Fibroblast cell lines derived from the double-deficient embryos accumulated autophagic vacuoles and the autophagy protein LC3II after amino acid starvation. Lysosomal vesicles were larger and more peripherally distributed and showed a lower specific density in Percoll gradients in double deficient when compared with control cells. Lysosomal enzyme activities, cathepsin D processing and mannose-6-phosphate receptor expression levels were not affected by the deficiency of both LAMPs. Surprisingly, LAMP-1 and -2 deficiencies did not affect long-lived protein degradation rates, including proteolysis due to chaperone-mediated autophagy. The LAMP-1/2 double-deficient cells and, to a lesser extent, LAMP-2 single-deficient cells showed an accumulation of unesterified cholesterol in endo/lysosomal, rab7, and NPC1 positive compartments as well as reduced amounts of lipid droplets. The cholesterol accumulation in LAMP-1/2 double-deficient cells could be rescued by overexpression of murine LAMP-2a, but not by LAMP-1, highlighting the more prominent role of LAMP-2. Taken together these findings indicate partially overlapping functions for LAMP-1 and -2 in lysosome biogenesis, autophagy, and cholesterol homeostasis.
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30
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Schwarz M, Thiel C, Lübbehusen J, Dorland B, de Koning T, von Figura K, Lehle L, Körner C. Deficiency of GDP-Man:GlcNAc2-PP-dolichol mannosyltransferase causes congenital disorder of glycosylation type Ik. Am J Hum Genet 2004; 74:472-81. [PMID: 14973778 PMCID: PMC1182261 DOI: 10.1086/382492] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2003] [Accepted: 01/02/2004] [Indexed: 01/17/2023] Open
Abstract
The molecular nature of a severe multisystemic disorder with a recurrent nonimmune hydrops fetalis was identified as deficiency of GDP-Man:GlcNAc(2)-PP-dolichol mannosyltransferase, the human orthologue of the yeast ALG1 gene (MIM 605907). The disease belongs to the group of congenital disorders of glycosylation (CDG) and is designated as subtype CDG-Ik. In patient-derived serum, the total amount of the glycoprotein transferrin was reduced. Moreover, a partial loss of N-glycan chains was observed, a characteristic feature of CDG type I forms. Metabolic labeling with [6-(3)H]glucosamine revealed an accumulation of GlcNAc(2)-PP-dolichol and GlcNAc(1)-PP-dolichol in skin fibroblasts of the patient. Incubation of fibroblast extracts with [(14)C]GlcNAc(2)-PP-dolichol and GDP-mannose indicated a severely reduced activity of the beta 1,4-mannosyltransferase, elongating GlcNAc(2)-PP-dolichol to Man(1)GlcNAc(2)-PP-dolichol at the cytosolic side of the endoplasmic reticulum. Genetic analysis of the patient's hALG1 gene identified a homozygous mutation leading to the exchange of a serine residue to leucine at position 258 in the hALG1 protein. The disease-causing nature of the hALG1 mutation for the glycosylation defect was verified by a retroviral complementation approach in patient-derived primary fibroblasts and was confirmed by the expression of wild-type and mutant hALG1 in the Saccharomyces cerevisiae alg1-1 strain.
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Affiliation(s)
- Markus Schwarz
- Georg-August-Universität Göttingen, Biochemie II, Göttingen, Germany; Universität Regensburg, Lehrstuhl für Zellbiologie und Pflanzenphysiologie, Regensburg, Germany; UMC Utrecht, Department of Metabolic and Endocrine Diseases, and UMC Utrecht, Department of Pediatric Metabolic Diseases, Utrecht, The Netherlands
| | - Christian Thiel
- Georg-August-Universität Göttingen, Biochemie II, Göttingen, Germany; Universität Regensburg, Lehrstuhl für Zellbiologie und Pflanzenphysiologie, Regensburg, Germany; UMC Utrecht, Department of Metabolic and Endocrine Diseases, and UMC Utrecht, Department of Pediatric Metabolic Diseases, Utrecht, The Netherlands
| | - Jürgen Lübbehusen
- Georg-August-Universität Göttingen, Biochemie II, Göttingen, Germany; Universität Regensburg, Lehrstuhl für Zellbiologie und Pflanzenphysiologie, Regensburg, Germany; UMC Utrecht, Department of Metabolic and Endocrine Diseases, and UMC Utrecht, Department of Pediatric Metabolic Diseases, Utrecht, The Netherlands
| | - Bert Dorland
- Georg-August-Universität Göttingen, Biochemie II, Göttingen, Germany; Universität Regensburg, Lehrstuhl für Zellbiologie und Pflanzenphysiologie, Regensburg, Germany; UMC Utrecht, Department of Metabolic and Endocrine Diseases, and UMC Utrecht, Department of Pediatric Metabolic Diseases, Utrecht, The Netherlands
| | - Tom de Koning
- Georg-August-Universität Göttingen, Biochemie II, Göttingen, Germany; Universität Regensburg, Lehrstuhl für Zellbiologie und Pflanzenphysiologie, Regensburg, Germany; UMC Utrecht, Department of Metabolic and Endocrine Diseases, and UMC Utrecht, Department of Pediatric Metabolic Diseases, Utrecht, The Netherlands
| | - Kurt von Figura
- Georg-August-Universität Göttingen, Biochemie II, Göttingen, Germany; Universität Regensburg, Lehrstuhl für Zellbiologie und Pflanzenphysiologie, Regensburg, Germany; UMC Utrecht, Department of Metabolic and Endocrine Diseases, and UMC Utrecht, Department of Pediatric Metabolic Diseases, Utrecht, The Netherlands
| | - Ludwig Lehle
- Georg-August-Universität Göttingen, Biochemie II, Göttingen, Germany; Universität Regensburg, Lehrstuhl für Zellbiologie und Pflanzenphysiologie, Regensburg, Germany; UMC Utrecht, Department of Metabolic and Endocrine Diseases, and UMC Utrecht, Department of Pediatric Metabolic Diseases, Utrecht, The Netherlands
| | - Christian Körner
- Georg-August-Universität Göttingen, Biochemie II, Göttingen, Germany; Universität Regensburg, Lehrstuhl für Zellbiologie und Pflanzenphysiologie, Regensburg, Germany; UMC Utrecht, Department of Metabolic and Endocrine Diseases, and UMC Utrecht, Department of Pediatric Metabolic Diseases, Utrecht, The Netherlands
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Dressel R, Raja SM, Höning S, Seidler T, Froelich CJ, von Figura K, Günther E. Granzyme-mediated cytotoxicity does not involve the mannose 6-phosphate receptors on target cells. J Biol Chem 2004; 279:20200-10. [PMID: 14985351 DOI: 10.1074/jbc.m313108200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cytotoxic T lymphocytes (CTL) and natural killer cells secrete granzymes to kill infected or transformed cells. The mannose 6-phosphate receptor (Mpr) 300 on target cells has been reported to function as receptor for secreted granzyme B. Using lymphoblasts and mouse embryonal fibroblast lines from Mpr300 and Mpr46 knockout mice, we show here that both receptors are not essential for CTL-induced apoptosis. Similarly, cells exposed to either monomeric granzyme B or granzyme B-serglycin complexes readily internalize the granzyme and undergo apoptosis in the absence of Mpr300 and Mpr46. Further, no colocalization of granzyme B and Mpr300 could be observed in target cells after internalization. In conclusion, these results strongly argue against an Mpr300- or Mpr46-dependent pathway of granzyme-mediated killing and provide new insight in the internalization of monomeric and complexed granzyme B.
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Affiliation(s)
- Ralf Dressel
- Division of Immunogenetics, University of Göttingen, Heinrich-Düker-Weg 12, 37073 Göttingen, Germany.
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Landgrebe J, Dierks T, Schmidt B, von Figura K. The human SUMF1 gene, required for posttranslational sulfatase modification, defines a new gene family which is conserved from pro- to eukaryotes. Gene 2004; 316:47-56. [PMID: 14563551 DOI: 10.1016/s0378-1119(03)00746-7] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Recently, the human C(alpha)-formylglycine (FGly)-generating enzyme (FGE), whose deficiency causes the autosomal-recessively transmitted lysosomal storage disease multiple sulfatase deficiency (MSD), has been identified. In sulfatases, FGE posttranslationally converts a cysteine residue to FGly, which is part of the catalytic site and is essential for sulfatase activity. FGE is encoded by the sulfatase modifying factor 1 (SUMF1) gene, which defines a new gene family comprising orthologs from prokaryotes to higher eukaryotes. The genomes of E. coli, S. cerevisiae and C. elegans lack SUMF1, indicating a phylogenetic gap and the existence of an alternative FGly-generating system. The genomes of vertebrates including mouse, man and pufferfish contain a sulfatase modifying factor 2 (SUMF2) gene encoding an FGE paralog of unknown function. SUMF2 evolved from a single exon SUMF1 gene as found in diptera prior to divergent intron acquisition. In several prokaryotic genomes, the SUMF1 gene is cotranscribed with genes encoding sulfatases which require FGly modification. The FGE protein contains a single domain that is made up of three highly conserved subdomains spaced by nonconserved sequences of variable lengths. The similarity among the eukaryotic FGE orthologs varies between 72% and 100% for the three subdomains and is highest for the C-terminal subdomain, which is a hotspot for mutations in MSD patients.
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Affiliation(s)
- Jobst Landgrebe
- Abt. Biochemie II, Universität Göttingen, Heinrich-Düker-Weg 12, 37073 Göttingen, Germany
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33
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Schellens JPM, Saftig P, von Figura K, Everts V. Deficiency of mannose 6-phosphate receptors and lysosomal storage: a morphometric analysis of hepatocytes of neonatal mice. Cell Biol Int 2003; 27:897-902. [PMID: 14585283 DOI: 10.1016/j.cellbi.2003.07.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Transport of lysosomal enzymes is mediated by two mannose 6-phosphate receptors: a cation dependent (CD-MPR) and a cation independent receptor (CI-MPR). In the present study the effect of MPR-deficiency on the lysosomal system of neonatal mouse hepatocytes was studied by ultrastructural morphometric analyses. The volume density of the lysosomal system in hepatocytes of mice that lack both receptors was significantly increased in comparison with controls and with mice deficient for CI-MPR only. This higher volume density was due to a nine-fold increase of residual bodies. In CI-MPR-deficient mice the volume density of the lysosomal system was not different from controls and no increase of residual bodies was observed. It is concluded that in hepatocytes of MPR-deficient neonatal mice lysosomal storage occurs when both MPRs are lacking, whereas deficiency of CI-MPR only has no effect on the ultrastructure of the lysosomal system.
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Affiliation(s)
- Jacques P M Schellens
- Department of Cell Biology and Histology, Academic Medical Center, University of Amsterdam, P.O. Box 22700, 1100 DE, Amsterdam, The Netherlands
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34
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Thiel C, Schwarz M, Peng J, Grzmil M, Hasilik M, Braulke T, Kohlschütter A, von Figura K, Lehle L, Körner C. A new type of congenital disorders of glycosylation (CDG-Ii) provides new insights into the early steps of dolichol-linked oligosaccharide biosynthesis. J Biol Chem 2003; 278:22498-505. [PMID: 12684507 DOI: 10.1074/jbc.m302850200] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Deficiency of GDP-Man:Man1GlcNAc2-PP-dolichol mannosyltransferase (hALG2), is the cause of a new type of congenital disorders of glycosylation (CDG) designated CDG-Ii. The patient presented normal at birth but developed in the 1st year of life a multisystemic disorder with mental retardation, seizures, coloboma of the iris, hypomyelination, hepatomegaly, and coagulation abnormalities. An accumulation of Man1GlcNAc2-PP-dolichol and Man2GlcNAc2-PP-dolichol was observed in skin fibroblasts of the patient. Incubation of patient fibroblast extracts with Man1GlcNAc2-PP-dolichol and GDP-mannose revealed a severely reduced activity of the mannosyltransferase elongating Man1GlcNAc2-PP dolichol. Because the Saccharomyces cerevisiae mutant alg2-1 was known to accumulate the same shortened dolichol-linked oligosaccharides as the patient, the yeast ALG2 sequence was used to identify the human ortholog. Genetic analysis revealed that the patient was heterozygous for a single nucleotide deletion and a single nucleotide substitution in the human ortholog of yeast ALG2. Expression of wild type but not of mutant hALG2 cDNA restored the mannosyltransferase activity and the biosynthesis of dolichol-linked oligosaccharides both in patient fibroblasts and in the alg2-1 yeast cells. hALG2 was shown to act as an alpha1,3-mannosyltransferase. The resulting Manalpha1,3-ManGlcNAc2-PP dolichol is further elongated by a yet unknown alpha1,6-mannosyltransferase.
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Affiliation(s)
- Christian Thiel
- Georg-August-Universität Göttingen, Biochemie II, Heinrich-Düker-Weg 12, D-37073 Göttingen, Germany
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35
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Friedrichs B, Tepel C, Reinheckel T, Deussing J, von Figura K, Herzog V, Peters C, Saftig P, Brix K. Thyroid functions of mouse cathepsins B, K, and L. J Clin Invest 2003; 111:1733-45. [PMID: 12782676 PMCID: PMC156100 DOI: 10.1172/jci15990] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Thyroid function depends on processing of the prohormone thyroglobulin by sequential proteolytic events. From in vitro analysis it is known that cysteine proteinases mediate proteolytic processing of thyroglobulin. Here, we have analyzed mice with deficiencies in cathepsins B, K, L, B and K, or K and L in order to investigate which of the cysteine proteinases is most important for proteolytic processing of thyroglobulin in vivo. Immunolabeling demonstrated a rearrangement of the endocytic system and a redistribution of extracellularly located enzymes in thyroids of cathepsin-deficient mice. Cathepsin L was upregulated in thyroids of cathepsin K(-/-) or B(-/-)/K(-/-) mice, suggesting a compensation of cathepsin L for cathepsin K deficiency. Impaired proteolysis resulted in the persistence of thyroglobulin in the thyroids of mice with deficiencies in cathepsin B or L. The typical multilayered appearance of extracellularly stored thyroglobulin was retained in cathepsin K(-/-) mice only. These results suggest that cathepsins B and L are involved in the solubilization of thyroglobulin from its covalently cross-linked storage form. Cathepsin K(-/-)/L(-/-) mice had significantly reduced levels of free thyroxine, indicating that utilization of luminal thyroglobulin for thyroxine liberation is mediated by a combinatory action of cathepsins K and L.
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Affiliation(s)
- Bianca Friedrichs
- Institut für Zellbiologie and Bonner Forum Biomedizin, Universität Bonn, Bonn, Germany
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36
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Dierks T, Schmidt B, Borissenko LV, Peng J, Preusser A, Mariappan M, von Figura K. Multiple sulfatase deficiency is caused by mutations in the gene encoding the human C(alpha)-formylglycine generating enzyme. Cell 2003; 113:435-44. [PMID: 12757705 DOI: 10.1016/s0092-8674(03)00347-7] [Citation(s) in RCA: 268] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
C(alpha)-formylglycine (FGly) is the catalytic residue in the active site of eukaryotic sulfatases. It is posttranslationally generated from a cysteine in the endoplasmic reticulum. The genetic defect of FGly formation causes multiple sulfatase deficiency (MSD), a lysosomal storage disorder. We purified the FGly generating enzyme (FGE) and identified its gene and nine mutations in seven MSD patients. In patient fibroblasts, the activity of sulfatases is partially restored by transduction of FGE encoding cDNA, but not by cDNA carrying an MSD mutation. The gene encoding FGE is highly conserved among pro- and eukaryotes and has a paralog of unknown function in vertebrates. FGE is localized in the endoplasmic reticulum and is predicted to have a tripartite domain structure.
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37
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Gamp AC, Tanaka Y, Lüllmann-Rauch R, Wittke D, D'Hooge R, De Deyn PP, Moser T, Maier H, Hartmann D, Reiss K, Illert AL, von Figura K, Saftig P. LIMP-2/LGP85 deficiency causes ureteric pelvic junction obstruction, deafness and peripheral neuropathy in mice. Hum Mol Genet 2003; 12:631-46. [PMID: 12620969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/01/2023] Open
Abstract
In previous overexpression studies we revealed a role for the lysosomal membrane protein LIMP-2/LGP85 in lysosomal biogenesis. LIMP-2-deficient mice show an increased postnatal mortality which is associated with a development of a uni- or bilateral hydronephrosis caused by an obstruction of the ureteropelvic junction. An accumulation of lysosomes in epithelial cells of the ureter adjacent to the ureteral lumen and a disturbed apical expression of uroplakin was observed, suggesting an impairment of membrane transport processes. Serious hearing impairment in LIMP-2-deficient animals was indicated by deficits in acoustic startle responses, in brainstem evoked auditory potentials and a reduced endochondral potential. LIMP-2-deficient mice suffer from a massive decline of spiral ganglia in the cochlea concomitant with that of the inner and outer hair cells. These pathological changes begin at the age of 3 months and are probably secondary to a degeneration of the stria vascularis. LIMP-2-deficient mice are also characterized by a peripheral demyelinating neuropathy. Demyelinization was found to be associated with a massive loss of peripheral myelin proteins and an increased activity and expression of lysosomal proteins highlighting a hitherto unknown role of the lysosomal compartment in the development of this myelination disorder. The phenotype of LIMP-2-deficient mice stimulates the search for mutations in human disorders associated with degeneration of the stria vascularis and/or demyelinization of peripheral nerves.
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MESH Headings
- Animals
- Animals, Newborn
- Biological Transport
- Blotting, Southern
- Blotting, Western
- CD36 Antigens/genetics
- CD36 Antigens/physiology
- Cathepsin D/biosynthesis
- Cell Membrane
- Cochlea/metabolism
- Cochlea/pathology
- Deafness/genetics
- Demyelinating Diseases/genetics
- Epithelial Cells/metabolism
- Evoked Potentials, Auditory
- Exons
- Fibroblasts/metabolism
- Genotype
- Hypertrophy
- Kidney/metabolism
- Lysosomal Membrane Proteins
- Lysosomes/metabolism
- Membrane Glycoproteins
- Membrane Proteins
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Mutant Strains
- Mice, Transgenic
- Microscopy, Electron
- Microscopy, Fluorescence
- Models, Genetic
- Mutation
- Peripheral Nervous System Diseases/genetics
- Phenotype
- Receptors, Scavenger
- Recombination, Genetic
- Reverse Transcriptase Polymerase Chain Reaction
- Sialoglycoproteins
- Subcellular Fractions/metabolism
- Time Factors
- Tissue Distribution
- Transgenes
- Ureter/metabolism
- Urinary Bladder/metabolism
- Urothelium/pathology
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Affiliation(s)
- Alexander-Christian Gamp
- Zentrum Biochemie und Molekulare Zellbiologie, Abt. Biochemie II, Universität Göttingen, 37073 Göttingen, Germany
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38
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Koike M, Shibata M, Ohsawa Y, Nakanishi H, Koga T, Kametaka S, Waguri S, Momoi T, Kominami E, Peters C, Figura KV, Saftig P, Uchiyama Y. Involvement of two different cell death pathways in retinal atrophy of cathepsin D-deficient mice. Mol Cell Neurosci 2003; 22:146-61. [PMID: 12676526 DOI: 10.1016/s1044-7431(03)00035-6] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
To understand the mechanisms of retinal atrophy in cathepsin D-deficient mice, the postnatal development of their retinae was analyzed. TUNEL-positive cells appeared abundantly in the outer nuclear layer (ONL) and slightly in the inner nuclear layer (INL). Nitric oxide synthase (NOS) was induced in microglial cells which invaded retinal layers and phagocytosed dead cell debris, while NOS inhibitors prevented cell death in the INL but not in the ONL. Caspases 9 and 3 were activated only in the ONL after P15. Moreover, no atrophic change was detected in the retina of mice deficient in cathepsin B or L. These results suggest that cathepsin D is essential for the metabolic maintenance of retinal photoreceptor cells and that its deficiency induces apoptosis of the cells, while the loss of INL neurons is mediated by NO from microglial cells.
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Affiliation(s)
- Masato Koike
- Department of Cell Biology and Neurosciences, Osaka University Graduate School of Medicine, 565-0871, Suita, Osaka, Japan
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39
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Marquordt C, Fang Q, Will E, Peng J, von Figura K, Dierks T. Posttranslational modification of serine to formylglycine in bacterial sulfatases. Recognition of the modification motif by the iron-sulfur protein AtsB. J Biol Chem 2003; 278:2212-8. [PMID: 12419807 DOI: 10.1074/jbc.m209435200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calpha-formylglycine is the catalytic residue of sulfatases. Formylglycine is generated by posttranslational modification of a cysteine (pro- and eukaryotes) or serine (prokaryotes) located in a conserved (C/S)XPXR motif. The modifying enzymes are unknown. AtsB, an iron-sulfur protein, is strictly required for modification of Ser(72) in the periplasmic sulfatase AtsA of Klebsiella pneumoniae. Here we show (i) that AtsB is a cytosolic protein acting on newly synthesized serine-type sulfatases, (ii) that AtsB-mediated FGly formation is dependent on AtsA's signal peptide, and (iii) that the cytosolic cysteine-type sulfatase of Pseudomonas aeruginosa can be converted into a substrate of AtsB if the cysteine is substituted by serine and a signal peptide is added. Thus, formylglycine formation in serine-type sulfatases depends both on AtsB and on the presence of a signal peptide, and AtsB can act on sulfatases of other species. AtsB physically interacts with AtsA in a Ser(72)-dependent manner, as shown in yeast two-hybrid and GST pull-down experiments. This strongly suggests that AtsB is the serine-modifying enzyme and that AtsB relies on a cytosolic function of the sulfatase's signal peptide.
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Affiliation(s)
- Claudia Marquordt
- Institut für Biochemie und Molekulare Zellbiologie, Abt. Biochemie II, Universität Göttingen, Heinrich-Düker-Weg 12, Germany
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40
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Usón I, Schmidt B, von Bülow R, Grimme S, von Figura K, Dauter M, Rajashankar KR, Dauter Z, Sheldrick GM. Locating the anomalous scatterer substructures in halide and sulfur phasing. Acta Crystallogr D Biol Crystallogr 2003; 59:57-66. [PMID: 12499540 DOI: 10.1107/s090744490201884x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2002] [Accepted: 10/14/2002] [Indexed: 11/10/2022]
Abstract
Improved data quality now makes it feasible to exploit the weak anomalous signal derived only from the sulfurs inherent to the protein or in particular from halide ions incorporated by soaking. The latter technique requires the location of a high number of partially occupied halide sites. This number appears to be roughly proportional to the exposed protein surface. This paper explores the application of dual-space ab initio methods as implemented in the program SHELXD to the location of substructures of sulfur in SAD experiments, bromide in SAD and MAD experiments and iodide using SAD and SIRAS to determine the anomalous-atom substructure. Sets of atoms consistent with the Patterson function were generated as a starting point for the dual-space recycling procedure in SHELXD. The substructure is then expanded to the full structure by maximum-likelihood phasing with SHARP and density modification with the program DM. Success in the location of the substructures and subsequent phasing depends critically on the quality of the data and on the extent of the anomalous signal. This varies with each crystal and soak, but for the same crystal the significance of the anomalous signal was found to be highly sensitive to the redundancy of the intensity measurements, which in some cases made all the difference. This is illustrated by the determination of the previously unknown structure of repeat 11 of the human mannose-6-phosphate/insulin-like growth factor II receptor (Man6P/IGFII-receptor), with 310 amino acids in the asymmetric unit, which was phased by soaking the crystals in a cryoprotectant solution containing halide anions.
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Affiliation(s)
- Isabel Usón
- Lehrstuhl für Strukturchemie, Institut für Anorganische Chemie, Universität Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany.
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41
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Peng J, Schmidt B, von Figura K, Dierks T. Identification of formylglycine in sulfatases by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. J Mass Spectrom 2003; 38:80-86. [PMID: 12526009 DOI: 10.1002/jms.404] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
C(alpha)-Formylglycine, the catalytic amino acid residue in the active site of sulfatases, is generated by post-translational modification of a cysteine or serine residue. We describe a highly sensitive procedure for the detection of C(alpha)-formylglycine-containing peptides in tryptic digests of sulfatase proteins. The protocol is based on the formation of hydrazone derivatives of C(alpha)-formylglycine-containing peptides when using dinitrophenylhydrazine as a matrix for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The hydrazone derivatives desorb and ionize with high efficiency and can be detected in the sub-femtomole range. The presence of C(alpha)-formylglycine is indicated by a mass increment of 180.13 u, corresponding to the hydrazone moiety, and also by a unique C-terminal fragment ion, characteristic of sulfatases, that becomes prominent in MALDI post-source decay mass spectra of the hydrazone derivatives.
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Affiliation(s)
- Jianhe Peng
- Institut für Biochemie und Molekulare Zellbiologie, Abt. Biochemie II, Universität Göttingen, Heinrich-Düker-Weg 12, Germany.
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42
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Rodionov DG, Höning S, Silye A, Kongsvik TL, von Figura K, Bakke O. Structural requirements for interactions between leucine-sorting signals and clathrin-associated adaptor protein complex AP3. J Biol Chem 2002; 277:47436-43. [PMID: 12370188 DOI: 10.1074/jbc.m207149200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Cytoplasmic tails of LIMPII and the invariant chain contain similar leucine-based sorting signals, but the invariant chain interacts only with AP1 and AP2, whereas LIMPII interacts strongly with AP3. In a series of in vitro experiments, we investigated the effect of residues upstream of the leucine pairs and demonstrated that these residues determine adapter binding, and certain residues favor interactions with AP3. Furthermore, constructs that interacted stronger with AP3 interacted weakly with AP1 and vice versa. Exchanging residues upstream of the leucine-based signal in LIMPII with those of the invariant chain reduced LIMPII binding to AP3 in vitro, and in vivo the corresponding LIMPII mutant was rerouted via the plasma membrane like the invariant chain. These preferential interactions of different leucine signals with different AP complexes may thus be the determining step sorting proteins from the trans-Golgi network to their final destinations. Proteins that interact with AP3 are sorted directly to endosomes/lysosomes, whereas proteins that interact with AP1 are sorted via a different route. At the same time, constructs that exhibited specificity for either AP1 or AP3 might still interact with AP2, suggesting that AP2 may recognize a wider variety of leucine signals. This is consistent with the suggested role of AP2 in internalization of proteins containing general leucine-based signals, including proteins that have been missorted to the plasma membrane.
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Affiliation(s)
- Dmitrii G Rodionov
- Division of Molecular Cell Biology, Department of Biology, University of Oslo, Norway
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43
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Abstract
Mannose 6-phosphate receptor (MPR 300) protein was earlier affinity purified on phosphomannan gel from the membrane extracts of whole animal acetone powder of a mollusc, unio, in the presence of EDTA (Udaya Lakshmi, Y., Radha, Y., Hille-Rehfeld, A., von Figura, K., and Siva Kumar, N. (1999) Biosci. Rep. 19:403-409). In the present study we demonstrate that the unio also contains the putative mannose 6-phosphate receptor (MPR 46) that can be purified on the same gel in presence of divalent metal ions (10 mM each of calcium, manganese, and magnesium), and in the absence of sodium chloride and at pH 6.5. Chicken and Fish cell MPR 46 proteins were purified under these conditions (Siva Kumar, N., Udaya Lakshmi, Y., Hille-Rehfeld, A., and von Figura, K. (1999) Comp. Biochem. & PhysioL 123B:261-265). The authenticity of the receptor is further confirmed by its ability to react with the MSC1 antibody that is specific for MPR 46 protein. Additional evidence for the presence of MPR 46 in molluscs could be obtained by metabolic labeling of mollusc cells Biomphalaria glabrata (Bg cells) with [35S] methionine and cysteine, and passing the labeled membrane extract on phosphomannan gel (at pH 6.5 and 7.0). On elution with mannose 6-phosphate, followed by immunoprecipitation of the column fractions, we identified the putative MPR 46 protein in the Bg cells. When Bg cell MPR 46 was deglycosylated along with chicken MPR 46 (control) both species yielded a single polypeptide corresponding to molecular mass of 26 kDa, suggesting that both contain the same receptor protein.
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Affiliation(s)
- Siva Kumar Nadimpalli
- Protein Biochemistry Laboratory, Department of Biochemistry, University of Hyderabad, Hyderabad 500 046, India.
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44
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Hartmann D, de Strooper B, Serneels L, Craessaerts K, Herreman A, Annaert W, Umans L, Lübke T, Lena Illert A, von Figura K, Saftig P. The disintegrin/metalloprotease ADAM 10 is essential for Notch signalling but not for alpha-secretase activity in fibroblasts. Hum Mol Genet 2002; 11:2615-24. [PMID: 12354787 DOI: 10.1093/hmg/11.21.2615] [Citation(s) in RCA: 517] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The metalloprotease ADAM 10 is an important APP alpha-secretase candidate, but in vivo proof of this is lacking. Furthermore, invertebrate models point towards a key role of the ADAM 10 orthologues Kuzbanian and sup-17 in Notch signalling. In the mouse, this function is, however, currently attributed to ADAM 17/TACE, while the role of ADAM 10 remains unknown. We have created ADAM 10-deficient mice. They die at day 9.5 of embryogenesis with multiple defects of the developing central nervous system, somites, and cardiovascular system. In situ hybridization revealed a reduced expression of the Notch target gene hes-5 in the neural tube and an increased expression of the Notch ligand dll-1, supporting an important role for ADAM 10 in Notch signalling in the vertebrates as well. Since the early lethality precluded the establishment of primary neuronal cultures, APPs alpha generation was analyzed in embryonic fibroblasts and found to be preserved in 15 out of 17 independently generated ADAM 10-deficient fibroblast cell lines, albeit at a quantitatively more variable level than in controls, whereas a severe reduction was found in only two cases. The variability was not due to differences in genetic background or to variable expression of the alternative alpha-secretase candidates ADAM 9 and ADAM 17. These results indicate, therefore, either a regulation between ADAMs on the post-translational level or that other, not yet known, proteases are able to compensate for ADAM 10 deficiency. Thus, the observed variability, together with recent reports on tissue-specific expression patterns of ADAMs 9, 10 and 17, points to the existence of tissue-specific 'teams' of different proteases exerting alpha-secretase activity.
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Affiliation(s)
- Dieter Hartmann
- Center for Human Genetics KU Leuven and Flanders Interuniversity Institute for Biotechnology, VIB 4 KU Leuven, VIB 7 (Celgen), Herestraat 49, 3000 Leuven, Belgium
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Thiel C, Schwarz M, Hasilik M, Grieben U, Hanefeld F, Lehle L, von Figura K, Körner C. Deficiency of dolichyl-P-Man:Man7GlcNAc2-PP-dolichyl mannosyltransferase causes congenital disorder of glycosylation type Ig. Biochem J 2002; 367:195-201. [PMID: 12093361 PMCID: PMC1222867 DOI: 10.1042/bj20020794] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2002] [Revised: 06/25/2002] [Accepted: 07/02/2002] [Indexed: 12/27/2022]
Abstract
Deficiency of the endoplasmic reticulum enzyme dolichyl-phosphate mannose (Dol-P-Man):Man(7)GlcNAc(2)-PP-dolichyl mannosyltransferase leads to a new type of congenital disorder of glycosylation, designated type Ig. The patient 1 presented with a multisystemic disorder with microcephaly, developmental retardation, convulsions and dysmorphic signs. The isoelectric focusing pattern of the patient's serum transferrin showed the partial loss of complete N-glycan side chains. In skin fibroblasts from the patient, the activity of Dol-P-Man:Man(7)GlcNAc(2)-PP-Dol mannosyltransferase was severely reduced leading to the accumulation of Man(7)GlcNAc(2)-PP-Dol, which was transferred to newly synthesized glycoproteins. Sequencing of the Dol-P-Man:Man(7)GlcNAc(2)-PP-Dol mannosyltransferase cDNA revealed a compound heterozygosity for two point mutations, leading to the exchange of leucine(158) for a proline residue and a premature translation stop with loss of the C-terminal 74 amino acids. The parents were heterozygous for one of the two mutations. Retroviral expression of the wild-type Dol-P-Man:Man(7)GlcNAc(2)-PP-Dol mannosyltransferase cDNA in patient's fibroblasts normalized the mannosyltransferase activity.
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Affiliation(s)
- Christian Thiel
- Georg-August-Universität zu Göttingen, Abteilung Biochemie II, Heinrich-Düker-Weg 12, D-37073 Göttingen, Germany
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46
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Abstract
The heterotetrameric AP-1A adaptor complex of clathrin-coated vesicles is ubiquitously expressed. The mu 1-adaptin subunit of the complex exists as the ubiquitous mu 1A and the polarized epithelia-specific mu 1B, which are 80% identical. In polarized epithelia, mu 1B is incorporated into the AP-1B complex, which is required for basolateral plasma membrane sorting of the low-density lipoprotein receptor. Binding of AP-1B to subdomains of the trans-Golgi network (TGN) appears to be part of the mechanism by which protein sorting is mediated. We expressed mu 1B in mu 1A-deficient fibroblasts to test for mu 1B function in non-polarized cells. AP-1B complexes were formed and bound to the TGN and to endosomes. Moreover, AP-1B restored the AP-1A-dependent sorting of mannose 6-phosphate receptors between endosomes and the TGN. This demonstrates that mu 1A and mu 1B do have overlapping sorting functions and indicates that AP-1A and AP-1B mediate protein sorting along parallel pathways between the TGN and endosomes in polarized epithelia.
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Affiliation(s)
- Eeva-Liisa Eskelinen
- School of Life Sciences, Center for High Resolution Imaging and Processing, University of Dundee, Dundee DD1 5EH, UK
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47
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von Bülow R, Schmidt B, Dierks T, Schwabauer N, Schilling K, Weber E, Usón I, von Figura K. Defective oligomerization of arylsulfatase a as a cause of its instability in lysosomes and metachromatic leukodystrophy. J Biol Chem 2002; 277:9455-61. [PMID: 11777924 DOI: 10.1074/jbc.m111993200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In one of the most common mutations causing metachromatic leukodystrophy, the P426L-allele of arylsulfatase A (ASA), the deficiency of ASA results from its instability in lysosomes. Inhibition of lysosomal cysteine proteinases protects the P426L-ASA and restores the sulfatide catabolism in fibroblasts of the patients. P426L-ASA, but not wild type ASA, was cleaved by purified cathepsin L at threonine 421 yielding 54- and 9-kDa fragments. X-ray crystallography at 2.5-A resolution showed that cleavage is not due to a difference in the protein fold that would expose the peptide bond following threonine 421 to proteases. Octamerization, which depends on protonation of Glu-424, was impaired for P426L-ASA. The mutation lowers the pH for the octamer/dimer equilibrium by 0.6 pH units from pH 5.8 to 5.2. A second oligomerization mutant (ASA-A464R) was generated that failed to octamerize even at pH 4.8. A464R-ASA was degraded in lysosomes to catalytically active 54-kDa intermediate. In cathepsin L-deficient fibroblasts, degradation of P426L-ASA and A464R-ASA to the 54-kDa fragment was reduced, while further degradation was blocked. This indicates that defective oligomerization of ASA allows degradation of ASA to a catalytically active 54-kDa intermediate by lysosomal cysteine proteinases, including cathepsin L. Further degradation of the 54-kDa intermediate critically depends on cathepsin L and is modified by the structure of the 9-kDa cleavage product.
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Affiliation(s)
- Rixa von Bülow
- Georg-August-Universität Göttingen, Abt. Biochemie II, Heinrich-Düker-Weg 12, Göttingen 37073, Germany
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48
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Hanßke B, Thiel C, Lübke T, Hasilik M, Höning S, Peters V, Heidemann PH, Hoffmann GF, Berger EG, von Figura K, Körner C. Deficiency of UDP-galactose:N-acetylglucosamine β-1,4-galactosyltransferase I causes the congenital disorder of glycosylation type IId. J Clin Invest 2002. [DOI: 10.1172/jci0214010] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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49
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Ricotta D, Conner SD, Schmid SL, von Figura K, Honing S. Phosphorylation of the AP2 mu subunit by AAK1 mediates high affinity binding to membrane protein sorting signals. J Cell Biol 2002; 156:791-5. [PMID: 11877457 PMCID: PMC2173304 DOI: 10.1083/jcb.200111068] [Citation(s) in RCA: 215] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
During receptor-mediated endocytosis, AP2 complexes act as a bridge between the cargo membrane proteins and the clathrin coat by binding to sorting signals via the mu 2 subunit and to clathrin via the beta subunit. Here we show that binding of AP2 to sorting signals in vitro is regulated by phosphorylation of the mu 2 subunit of AP2. Phosphorylation of mu 2 enhances the binding affinity of AP2 for sorting motifs as much as 25-fold compared with dephosphorylated AP2. The recognition of sorting signals was not affected by the phosphorylation status of the alpha or beta 2 subunit, suggesting that phosphorylation of mu 2 is critical for regulation of AP2 binding to sorting signals. Phosphorylation of mu 2 occurs at a single threonine residue (Thr-156) and is mediated by the newly discovered adaptor-associated kinase, AAK1, which copurifies with AP2. We propose that phosphorylation of the AP2 mu 2 subunit by AAK1 ensures high affinity binding of AP2 to sorting signals of cargo membrane proteins during the initial steps of receptor-mediated endocytosis.
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Affiliation(s)
- Doris Ricotta
- Institute for Biochemistry II, University of Göttingen, 37073 Göttingen, Germany
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50
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Hansske B, Thiel C, Lübke T, Hasilik M, Höning S, Peters V, Heidemann PH, Hoffmann GF, Berger EG, von Figura K, Körner C. Deficiency of UDP-galactose:N-acetylglucosamine beta-1,4-galactosyltransferase I causes the congenital disorder of glycosylation type IId. J Clin Invest 2002; 109:725-33. [PMID: 11901181 PMCID: PMC150909 DOI: 10.1172/jci14010] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2001] [Accepted: 02/11/2002] [Indexed: 01/02/2023] Open
Abstract
Deficiency of the Golgi enzyme UDP-Gal:N-acetylglucosamine beta-1,4-galactosyltransferase I (beta4GalT I) (E.C.2.4.1.38) causes a new congenital disorder of glycosylation (CDG), designated type IId (CDG-IId), a severe neurologic disease characterized by a hydrocephalus, myopathy, and blood-clotting defects. Analysis of oligosaccharides from serum transferrin by HPLC, mass spectrometry, and lectin binding revealed the loss of sialic acid and galactose residues. In skin fibroblasts and leukocytes, galactosyltransferase activity was reduced to 5% that of controls. In fibroblasts, a truncated polypeptide was detected that was about 12 kDa smaller in size than wild-type beta4GalT I and that failed to localize to the Golgi apparatus. Sequencing of the beta4GalT I cDNA and gene revealed an insertion of a single nucleotide (1031-1032insC) leading to premature translation stop and loss of the C-terminal 50 amino acids of the enzyme. The patient was homozygous and his parents heterozygous for this mutation. Expression of a corresponding mutant cDNA in COS-7 cells led to the synthesis of a truncated, inactive polypeptide, which localized to the endoplasmic reticulum.
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Affiliation(s)
- Bengt Hansske
- Abteilung Biochemie II, Georg-August-Universität Göttingen, Heinrich-Düker-Weg 12, D-37073 Göttingen, Germany
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