1
|
Adhikari UK, Tayebi M. Epitope-specific anti-PrP antibody toxicity: a comparative in-silico study of human and mouse prion proteins. Prion 2021; 15:155-176. [PMID: 34632945 PMCID: PMC8900626 DOI: 10.1080/19336896.2021.1964326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Despite having therapeutic potential, anti-PrP antibodies caused a major controversy due to their neurotoxic effects. For instance, treating mice with ICSM antibodies delayed prion disease onset, but both were found to be either toxic or innocuous to neurons by researchers following cross-linking PrPC. In order to elucidate and understand the reasons that led to these contradictory outcomes, we conducted a comprehensive in silico study to assess the antibody-specific toxicity. Since most therapeutic anti-PrP antibodies were generated against human truncated recombinant PrP91-231 or full-length mouse PrP23-231, we reasoned that host specificity (human vs murine) of PrPC might influence the nature of the specific epitopes recognized by these antibodies at the structural level possibly explaining the 'toxicity' discrepancies reported previously. Initially, molecular dynamics simulation and pro-motif analysis of full-length human (hu)PrP and mouse (mo)PrP 3D structure displayed conspicuous structural differences between huPrP and moPrP. We identified 10 huPrP and 6 moPrP linear B-cell epitopes from the prion protein 3D structure where 5 out of 10 huPrP and 3 out of 6 moPrP B-cell epitopes were predicted to be potentially toxic in immunoinformatics approaches. Herein, we demonstrate that some of the predicted potentially 'toxic' epitopes identified by the in silico analysis were similar to the epitopes recognized by the toxic antibodies such as ICSM18 (146-159), POM1 (138-147), D18 (133-157), ICSM35 (91-110), D13 (95-103) and POM3 (95-100). This in silico study reveals the role of host specificity of PrPC in epitope-specific anti-PrP antibody toxicity.
Collapse
Affiliation(s)
| | - Mourad Tayebi
- School of Medicine, Western Sydney University, Campbelltown, NSW, Australia
| |
Collapse
|
2
|
Chida J, Hara H, Uchiyama K, Takahashi E, Miyata H, Kosako H, Tomioka Y, Ito T, Horiuchi H, Matsuda H, Kido H, Sakaguchi S. Prion protein signaling induces M2 macrophage polarization and protects from lethal influenza infection in mice. PLoS Pathog 2020; 16:e1008823. [PMID: 32845931 PMCID: PMC7489546 DOI: 10.1371/journal.ppat.1008823] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 09/14/2020] [Accepted: 07/20/2020] [Indexed: 11/18/2022] Open
Abstract
The cellular prion protein, PrPC, is a glycosylphosphatidylinositol anchored-membrane glycoprotein expressed most abundantly in neuronal and to a lesser extent in non-neuronal cells. Its conformational conversion into the amyloidogenic isoform in neurons is a key pathogenic event in prion diseases, including Creutzfeldt-Jakob disease in humans and scrapie and bovine spongiform encephalopathy in animals. However, the normal functions of PrPC remain largely unknown, particularly in non-neuronal cells. Here we show that stimulation of PrPC with anti-PrP monoclonal antibodies (mAbs) protected mice from lethal infection with influenza A viruses (IAVs), with abundant accumulation of anti-inflammatory M2 macrophages with activated Src family kinases (SFKs) in infected lungs. A SFK inhibitor dasatinib inhibited M2 macrophage accumulation in IAV-infected lungs after treatment with anti-PrP mAbs and abolished the anti-PrP mAb-induced protective activity against lethal influenza infection in mice. We also show that stimulation of PrPC with anti-PrP mAbs induced M2 polarization in peritoneal macrophages through SFK activation in vitro and in vivo. These results indicate that PrPC could activate SFK in macrophages and induce macrophage polarization to an anti-inflammatory M2 phenotype after stimulation with anti-PrP mAbs, thereby eliciting protective activity against lethal infection with IAVs in mice after treatment with anti-PrP mAbs. These results also highlight PrPC as a novel therapeutic target for IAV infection.
Collapse
Affiliation(s)
- Junji Chida
- Division of Molecular Neurobiology, The Institute for Enzyme Research (KOSOKEN), Tokushima University, Tokushima, Japan
| | - Hideyuki Hara
- Division of Molecular Neurobiology, The Institute for Enzyme Research (KOSOKEN), Tokushima University, Tokushima, Japan
| | - Keiji Uchiyama
- Division of Molecular Neurobiology, The Institute for Enzyme Research (KOSOKEN), Tokushima University, Tokushima, Japan
| | - Etsuhisa Takahashi
- Division of Enzyme Chemistry, The Institute for Enzyme Research, Tokushima University (KOSOKEN), Tokushima, Japan
| | - Hironori Miyata
- Animal Research Center, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan
| | - Hidetaka Kosako
- Division of Cell Signaling, Fujii Memorial Institute of Medical Sciences, Tokushima University, Kuramoto-cho, Tokushima, Japan
| | - Yukiko Tomioka
- Laboratory of Laboratory Animal Science, Joint Department of Veterinary Medicine, Faculty of Agriculture, Tottori University, Tottori, Japan
| | - Toshihiro Ito
- Avian Zoonosis Research Center, Faculty of Agriculture, Tottori University, Koyama-cho, Tottori, Japan
| | - Hiroyuki Horiuchi
- Laboratory of Immunobiology, Graduate School of Integrated Sciences for Life, Hiroshima University, Japan
| | - Haruo Matsuda
- Laboratory of Immunobiology, Department of Molecular and Applied Bioscience, Graduate School of Biosphere Science, Hiroshima University, Japan
| | - Hiroshi Kido
- Division of Enzyme Chemistry, The Institute for Enzyme Research, Tokushima University (KOSOKEN), Tokushima, Japan
| | - Suehiro Sakaguchi
- Division of Molecular Neurobiology, The Institute for Enzyme Research (KOSOKEN), Tokushima University, Tokushima, Japan
- * E-mail:
| |
Collapse
|
3
|
Kriegler T, Lang S, Notari L, Hessa T. Prion Protein Translocation Mechanism Revealed by Pulling Force Studies. J Mol Biol 2020; 432:4447-4465. [PMID: 32502491 DOI: 10.1016/j.jmb.2020.05.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 05/10/2020] [Accepted: 05/28/2020] [Indexed: 11/26/2022]
Abstract
The mammalian prion protein (PrP) engages with the ribosome-Sec61 translocation channel complex to generate different topological variants that are either physiological, or involved in neurodegenerative diseases. Here, we describe cotranslational folding and translocation mechanisms of PrP coupled to an Xbp1-based arrest peptide as folding sensor, to measure forces acting on PrP nascent chain. Our data reveal two main pulling events followed by a minor third one exerted on the nascent chains during their translocation. Using those force landscapes, we show that a specific sequence within an intrinsically disordered region, containing a polybasic and glycine-proline rich residues, modulates the second pulling event by interacting with TRAP complex. This work also delineates the sequence of events involved in generation of PrP toxic transmembrane topologies during its synthesis. Our results shed new insight into the folding of such a topological complex protein, where marginal pulling by the signal sequence, together with the flanking downstream sequence in the mature domain, primarily drives an overall inefficient translocation resulting in the nascent chain to adopt alternative topologies.
Collapse
Affiliation(s)
- Theresa Kriegler
- Department of Biochemistry and Biophysics, Arrhenius Laboratories of Natural Sciences, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden
| | - Sven Lang
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Luigi Notari
- Department of Clinical Neuroscience, Therapeutic Immune Design Unit, CMM, L8:02, Karolinska Institutet, Sweden
| | - Tara Hessa
- Department of Biochemistry and Biophysics, Arrhenius Laboratories of Natural Sciences, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden.
| |
Collapse
|
4
|
PrP Knockout Cells Expressing Transmembrane PrP Resist Prion Infection. J Virol 2017; 91:JVI.01686-16. [PMID: 27847358 DOI: 10.1128/jvi.01686-16] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 11/01/2016] [Indexed: 11/20/2022] Open
Abstract
Glycosylphosphatidylinositol (GPI) anchoring of the prion protein (PrPC) influences PrPC misfolding into the disease-associated isoform, PrPres, as well as prion propagation and infectivity. GPI proteins are found in cholesterol- and sphingolipid-rich membrane regions called rafts. Exchanging the GPI anchor for a nonraft transmembrane sequence redirects PrPC away from rafts. Previous studies showed that nonraft transmembrane PrPC variants resist conversion to PrPres when transfected into scrapie-infected N2a neuroblastoma cells, likely due to segregation of transmembrane PrPC and GPI-anchored PrPres in distinct membrane environments. Thus, it remained unclear whether transmembrane PrPC might convert to PrPres if seeded by an exogenous source of PrPres not associated with host cell rafts and without the potential influence of endogenous expression of GPI-anchored PrPC To further explore these questions, constructs containing either a C-terminal wild-type GPI anchor signal sequence or a nonraft transmembrane sequence containing a flexible linker were expressed in a cell line derived from PrP knockout hippocampal neurons, NpL2. NpL2 cells have physiological similarities to primary neurons, representing a novel and advantageous model for studying transmissible spongiform encephalopathy (TSE) infection. Cells were infected with inocula from multiple prion strains and in different biochemical states (i.e., membrane bound as in brain microsomes from wild-type mice or purified GPI-anchorless amyloid fibrils). Only GPI-anchored PrPC supported persistent PrPres propagation. Our data provide strong evidence that in cell culture GPI anchor-directed membrane association of PrPC is required for persistent PrPres propagation, implicating raft microdomains as a location for conversion. IMPORTANCE Mechanisms of prion propagation, and what makes them transmissible, are poorly understood. Glycosylphosphatidylinositol (GPI) membrane anchoring of the prion protein (PrPC) directs it to specific regions of cell membranes called rafts. In order to test the importance of the raft environment on prion propagation, we developed a novel model for prion infection where cells expressing either GPI-anchored PrPC or transmembrane-anchored PrPC, which partitions it to a different location, were treated with infectious, misfolded forms of the prion protein, PrPres We show that only GPI-anchored PrPC was able to convert to PrPres and able to serially propagate. The results strongly suggest that GPI anchoring and the localization of PrPC to rafts are crucial to the ability of PrPC to propagate as a prion.
Collapse
|
5
|
Lewis V, Johanssen VA, Crouch PJ, Klug GM, Hooper NM, Collins SJ. Prion protein "gamma-cleavage": characterizing a novel endoproteolytic processing event. Cell Mol Life Sci 2016; 73:667-83. [PMID: 26298290 PMCID: PMC11108375 DOI: 10.1007/s00018-015-2022-z] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Revised: 07/17/2015] [Accepted: 08/11/2015] [Indexed: 12/31/2022]
Abstract
The cellular prion protein (PrP(C)) is a ubiquitously expressed protein of currently unresolved but potentially diverse function. Of putative relevance to normal biological activity, PrP(C) is recognized to undergo both α- and β-endoproteolysis, producing the cleavage fragment pairs N1/C1 and N2/C2, respectively. Experimental evidence suggests the likelihood that these processing events serve differing cellular needs. Through the engineering of a C-terminal c-myc tag onto murine PrP(C), as well as the selective use of a far-C-terminal anti-PrP antibody, we have identified a new PrP(C) fragment, nominally 'C3', and elaborating existing nomenclature, 'γ-cleavage' as the responsible proteolysis. Our studies indicate that this novel γ-cleavage event can occur during transit through the secretory pathway after exiting the endoplasmic reticulum, and after PrP(C) has reached the cell surface, by a matrix metalloprotease. We found that C3 is GPI-anchored like other C-terminal and full length PrP(C) species, though it does not localize primarily at the cell surface, and is preferentially cleaved from an unglycosylated substrate. Importantly, we observed that C3 exists in diverse cell types as well as mouse and human brain tissue, and of possible pathogenic significance, γ-cleavage may increase in human prion diseases. Given the likely relevance of PrP(C) processing to both its normal function, and susceptibility to prion disease, the potential importance of this previously underappreciated and overlooked cleavage event warrants further consideration.
Collapse
Affiliation(s)
- Victoria Lewis
- Department of Medicine, RMH, The University of Melbourne, Parkville, VIC, 3010, Australia
| | - Vanessa A Johanssen
- Department of Pathology, The University of Melbourne, Parkville, VIC, 3010, Australia
| | - Peter J Crouch
- Department of Pathology, The University of Melbourne, Parkville, VIC, 3010, Australia
| | - Genevieve M Klug
- Department of Medicine, RMH, The University of Melbourne, Parkville, VIC, 3010, Australia
- The Australian National Creutzfeldt-Jakob Disease Registry, The University of Melbourne, Parkville, VIC, 3010, Australia
| | - Nigel M Hooper
- Institute of Brain, Behaviour and Mental Health, Faculty of Medical and Human Sciences, The University of Manchester, Manchester, M13 9PT, UK
| | - Steven J Collins
- Department of Medicine, RMH, The University of Melbourne, Parkville, VIC, 3010, Australia.
- The Australian National Creutzfeldt-Jakob Disease Registry, The University of Melbourne, Parkville, VIC, 3010, Australia.
| |
Collapse
|
6
|
Bruno A, Scrima M, Novellino E, D'Errico G, D'Ursi AM, Limongelli V. The glycan role in the glycopeptide immunogenicity revealed by atomistic simulations and spectroscopic experiments on the multiple sclerosis biomarker CSF114(Glc). Sci Rep 2015; 5:9200. [PMID: 25776265 PMCID: PMC4361856 DOI: 10.1038/srep09200] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 02/24/2015] [Indexed: 12/22/2022] Open
Abstract
Glycoproteins are often recognized as not-self molecules by antibodies triggering the onset of severe autoimmune diseases such as Multiple Sclerosis (MS). Thus, the development of antigen-mimicking biomarkers represents an attractive strategy for an early diagnosis of the disease. An example is the synthetic glycopeptide CSF114(Glc), which was designed and tested as MS biomarker and whose clinical application was limited by its reduced ability to detect autoantibodies in MS patients. In the attempt to improve the efficacy of CSF114(Glc), we have characterized all the events leading to the final binding of the biomarker to the autoantibody using atomistic simulations, ESR and NMR experiments. The glycosydic moiety plays a primary role in the whole process. In particular, in an environment mimicking that used in the clinical tests the glycopeptide assumes a α-helix structure that is functional for the interaction with the antibody. In this conformation CSF114(Glc) binds the monoclonal antibody mAb8-18C5 similarly to the myelin oligodendrocyte glycoprotein MOG, which is a known MS auto-antigen, thus explaining its diagnostic activity. Our study offers new molecular bases to design more effective biomarkers and provides a most valid protocol to investigate other systems where the environment effect is determinant for the biological activity.
Collapse
Affiliation(s)
- Agostino Bruno
- Department of Pharmacy, University of Naples "Federico II", via D. Montesano 49, I-80131 Naples, Italy
| | - Mario Scrima
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II 132, I-84084 Fisciano, Italy
| | - Ettore Novellino
- Department of Pharmacy, University of Naples "Federico II", via D. Montesano 49, I-80131 Naples, Italy
| | - Gerardino D'Errico
- Dipartimento di Scienze Chimiche, Università di Napoli "Federico II", Complesso di Monte Sant'Angelo, via Cinthia, 80126 Naples, Italy
| | - Anna Maria D'Ursi
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II 132, I-84084 Fisciano, Italy
| | - Vittorio Limongelli
- 1] Department of Pharmacy, University of Naples "Federico II", via D. Montesano 49, I-80131 Naples, Italy [2] Università della Svizzera Italiana (USI), Faculty of Informatics, Institute of Computational Science, via G. Buffi 13, CH-6900 Lugano, Switzerland
| |
Collapse
|
7
|
Le Parc A, Honvo Houéto E, Pigat N, Chat S, Leonil J, Chanat E. The membrane-associated form of α(s1)-casein interacts with cholesterol-rich detergent-resistant microdomains. PLoS One 2014; 9:e115903. [PMID: 25549363 PMCID: PMC4280128 DOI: 10.1371/journal.pone.0115903] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Accepted: 12/02/2014] [Indexed: 12/19/2022] Open
Abstract
Caseins, the main milk proteins, interact with colloidal calcium phosphate to form the casein micelle. The mesostructure of this supramolecular assembly markedly influences its nutritional and technological functionalities. However, its detailed molecular organization and the cellular mechanisms involved in its biogenesis have been only partially established. There is a growing body of evidence to support the concept that α(s1)-casein takes center stage in casein micelle building and transport in the secretory pathway of mammary epithelial cells. Here we have investigated the membrane-associated form of α(s1)-casein in rat mammary epithelial cells. Using metabolic labelling we show that α(s1)-casein becomes associated with membranes at the level of the endoplasmic reticulum, with no subsequent increase at the level of the Golgi apparatus. From morphological and biochemical data, it appears that caseins are in a tight relationship with membranes throughout the secretory pathway. On the other hand, we have observed that the membrane-associated form of α(s1)-casein co-purified with detergent-resistant membranes. It was poorly solubilised by Tween 20, partially insoluble in Lubrol WX, and substantially insoluble in Triton X-100. Finally, we found that cholesterol depletion results in the release of the membrane-associated form of α(s1)-casein. These experiments reveal that the insolubility of α(s1)-casein reflects its partial association with a cholesterol-rich detergent-resistant microdomain. We propose that the membrane-associated form of α(s1)-casein interacts with the lipid microdomain, or lipid raft, that forms within the membranes of the endoplasmic reticulum, for efficient forward transport and sorting in the secretory pathway of mammary epithelial cells.
Collapse
Affiliation(s)
- Annabelle Le Parc
- UR1196 Génomique et Physiologie de la Lactation, Institut National de la Recherche Agronomique, Jouy-en-Josas, France
| | - Edith Honvo Houéto
- UR1196 Génomique et Physiologie de la Lactation, Institut National de la Recherche Agronomique, Jouy-en-Josas, France
| | - Natascha Pigat
- UR1196 Génomique et Physiologie de la Lactation, Institut National de la Recherche Agronomique, Jouy-en-Josas, France
| | - Sophie Chat
- UR1196 Génomique et Physiologie de la Lactation, Institut National de la Recherche Agronomique, Jouy-en-Josas, France
| | - Joëlle Leonil
- UMR1253 Science et Technologie du Lait et de l'Œuf, Institut National de la Recherche Agronomique, Rennes, France
| | - Eric Chanat
- UR1196 Génomique et Physiologie de la Lactation, Institut National de la Recherche Agronomique, Jouy-en-Josas, France
- * E-mail:
| |
Collapse
|
8
|
Galian C, Björkholm P, Bulleid N, von Heijne G. Efficient glycosylphosphatidylinositol (GPI) modification of membrane proteins requires a C-terminal anchoring signal of marginal hydrophobicity. J Biol Chem 2012; 287:16399-409. [PMID: 22431723 PMCID: PMC3351287 DOI: 10.1074/jbc.m112.350009] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2012] [Revised: 03/16/2012] [Indexed: 11/06/2022] Open
Abstract
Many plasma membrane proteins are anchored to the membrane via a C-terminal glycosylphosphatidylinositol (GPI) moiety. The GPI anchor is attached to the protein in the endoplasmic reticulum by transamidation, a reaction in which a C-terminal GPI-attachment signal is cleaved off concomitantly with addition of the GPI moiety. GPI-attachment signals are poorly conserved on the sequence level but are all composed of a polar segment that includes the GPI-attachment site followed by a hydrophobic segment located at the very C terminus of the protein. Here, we show that efficient GPI modification requires that the hydrophobicity of the C-terminal segment is "marginal": less hydrophobic than type II transmembrane anchors and more hydrophobic than the most hydrophobic segments found in secreted proteins. We further show that the GPI-attachment signal can be modified by the transamidase irrespective of whether it is first released into the lumen of the endoplasmic reticulum or is retained in the endoplasmic reticulum membrane.
Collapse
Affiliation(s)
- Carmen Galian
- From the Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University SE-106 91 Stockholm, Sweden
| | - Patrik Björkholm
- From the Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University SE-106 91 Stockholm, Sweden
| | - Neil Bulleid
- the Institute of Molecular, Cell and Systems Biology, CMVLS, University of Glasgow, Glasgow, G12 8QQ Scotland, United Kingdom, and
| | - Gunnar von Heijne
- From the Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University SE-106 91 Stockholm, Sweden
- the Science for Life Laboratory, Stockholm University, SE-171 77 Solna, Sweden
| |
Collapse
|
9
|
Andrew AJ, Kao S, Strebel K. C-terminal hydrophobic region in human bone marrow stromal cell antigen 2 (BST-2)/tetherin protein functions as second transmembrane motif. J Biol Chem 2011; 286:39967-81. [PMID: 21937450 DOI: 10.1074/jbc.m111.287011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
BST-2/CD317/HM1.24/tetherin is a host factor that inhibits the release of HIV-1 and other enveloped viruses. Structurally, tetherin consists of an N-terminal transmembrane (TM) region, a central coiled coil motif, and a putative C-terminal glycosylphosphatidylinositol (GPI) anchor motif. A current working model proposes that BST-2 inhibits virus release by physically tethering viral particles to the cell surface via its TM motif and GPI anchor. Here we analyzed the functional importance of the C-terminal GPI anchor motif in BST-2. We replaced the GPI anchor motif in BST-2 with the TM regions of several surface markers and found that the TM motifs of CD40 and transferrin receptor, but not that of CD45, could functionally substitute for a GPI anchor in BST-2. Conversely, replacing the TM region of CD4 by the putative GPI anchor signal of human BST-2 resulted in proper membrane targeting and surface expression of the chimeric protein, indicating that the BST-2 GPI anchor signal can function as a bona fide TM region. In fact, attempts to demonstrate GPI anchor modification of human BST-2 by biochemical methods failed. Our results demonstrate that the putative C-terminal GPI anchor motif in human BST-2 fulfills the requirements of a bona fide TM motif, leading us to propose that human BST-2 may in fact contain a second TM segment rather than a GPI anchor.
Collapse
Affiliation(s)
- Amy J Andrew
- Laboratory of Molecular Microbiology, Viral Biochemistry Section, NIAID, National Institutes of Health, Bethesda, Maryland 20892-0460, USA
| | | | | |
Collapse
|
10
|
Griffiths HH, Whitehouse IJ, Baybutt H, Brown D, Kellett KAB, Jackson CD, Turner AJ, Piccardo P, Manson JC, Hooper NM. Prion protein interacts with BACE1 protein and differentially regulates its activity toward wild type and Swedish mutant amyloid precursor protein. J Biol Chem 2011; 286:33489-500. [PMID: 21795680 DOI: 10.1074/jbc.m111.278556] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
In Alzheimer disease amyloid-β (Aβ) peptides derived from the amyloid precursor protein (APP) accumulate in the brain. Cleavage of APP by the β-secretase BACE1 is the rate-limiting step in the production of Aβ. We have reported previously that the cellular prion protein (PrP(C)) inhibited the action of BACE1 toward human wild type APP (APP(WT)) in cellular models and that the levels of endogenous murine Aβ were significantly increased in PrP(C)-null mouse brain. Here we investigated the molecular and cellular mechanisms underlying this observation. PrP(C) interacted directly with the prodomain of the immature Golgi-localized form of BACE1. This interaction decreased BACE1 at the cell surface and in endosomes where it preferentially cleaves APP(WT) but increased it in the Golgi where it preferentially cleaves APP with the Swedish mutation (APP(Swe)). In transgenic mice expressing human APP with the Swedish and Indiana familial mutations (APP(Swe,Ind)), PrP(C) deletion had no influence on APP proteolytic processing, Aβ plaque deposition, or levels of soluble Aβ or Aβ oligomers. In cells, although PrP(C) inhibited the action of BACE1 on APP(WT), it did not inhibit BACE1 activity toward APP(Swe). The differential subcellular location of the BACE1 cleavage of APP(Swe) relative to APP(WT) provides an explanation for the failure of PrP(C) deletion to affect Aβ accumulation in APP(Swe,Ind) mice. Thus, although PrP(C) exerts no control on cleavage of APP(Swe) by BACE1, it has a profound influence on the cleavage of APP(WT), suggesting that PrP(C) may be a key protective player against sporadic Alzheimer disease.
Collapse
Affiliation(s)
- Heledd H Griffiths
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Papanikolaou A, Papafotika A, Christoforidis S. CD39 Reveals Novel Insights into the Role of Transmembrane Domains in Protein Processing, Apical Targeting and Activity. Traffic 2011; 12:1148-65. [DOI: 10.1111/j.1600-0854.2011.01224.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
|
12
|
Baron GS, Hughson AG, Raymond GJ, Offerdahl DK, Barton KA, Raymond LD, Dorward DW, Caughey B. Effect of glycans and the glycophosphatidylinositol anchor on strain dependent conformations of scrapie prion protein: improved purifications and infrared spectra. Biochemistry 2011; 50:4479-90. [PMID: 21539311 PMCID: PMC3101284 DOI: 10.1021/bi2003907] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mammalian prion diseases involve conversion of normal prion protein, PrP(C), to a pathological aggregated state (PrP(res)). The three-dimensional structure of PrP(res) is not known, but infrared (IR) spectroscopy has indicated high, strain-dependent β-sheet content. PrP(res) molecules usually contain a glycophosphatidylinositol (GPI) anchor and large Asn-linked glycans, which can also vary with strain. Using IR spectroscopy, we tested the conformational effects of these post-translational modifications by comparing wild-type PrP(res) with GPI- and glycan-deficient PrP(res) produced in GPI-anchorless PrP transgenic mice. These analyses required the development of substantially improved purification protocols. Spectra of both types of PrP(res) revealed conformational differences between the 22L, ME7, and Chandler (RML) murine scrapie strains, most notably in bands attributed to β-sheets. These PrP(res) spectra were also distinct from those of the hamster 263K scrapie strain. Spectra of wild-type and anchorless 22L PrP(res) were nearly indistinguishable. With ME7 PrP(res), modest differences between the wild-type and anchorless spectra were detected, notably an ∼2 cm(-1) shift in an apparent β-sheet band. Collectively, the data provide evidence that the glycans and anchor do not grossly affect the strain-specific secondary structures of PrP(res), at least relative to the differences observed between strains, but can subtly affect turns and certain β-sheet components. Recently reported H-D exchange analyses of anchorless PrP(res) preparations strongly suggested the presence of strain-dependent, solvent-inaccessible β-core structures throughout most of the C-terminal half of PrP(res) molecules, with no remaining α-helix. Our IR data provide evidence that similar core structures also comprise wild-type PrP(res).
Collapse
Affiliation(s)
- Gerald S. Baron
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840
| | - Andrew G. Hughson
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840
| | - Gregory J. Raymond
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840
| | - Danielle K. Offerdahl
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840
| | - Kelly A. Barton
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840
| | - Lynne D. Raymond
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840
| | - David W. Dorward
- Microscopy Unit, Research Technology Branch, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840
| | - Byron Caughey
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840
| |
Collapse
|
13
|
Pult F, Fallah G, Braam U, Detro-Dassen S, Niculescu C, Laube B, Schmalzing G. Robust post-translocational N-glycosylation at the extreme C-terminus of membrane and secreted proteins in Xenopus laevis oocytes and HEK293 cells. Glycobiology 2011; 21:1147-60. [PMID: 21303814 DOI: 10.1093/glycob/cwr013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
N-Glycosylation is normally a co-translational process that occurs as soon as a nascent and unfolded polypeptide chain has emerged ~12 residues into the lumen of the endoplasmic reticulum (ER). Here, we describe the efficient utilization of an N-glycosylation site engineered within the luminal extreme C-terminal residues of distinct integral membrane glycoproteins, a native ER resident protein and an engineered secreted protein. This N-glycan addition required that the acceptor asparagine within an Asn-Trp-Ser sequon be located at least four residues away from the C-terminus of the polypeptide and, in the case of membrane proteins, at least 13 residues away from the lumenal side of the transmembrane segment. Pulse-chase assays revealed that the natural N-glycans of the proteins studied were attached co-translationally, whereas C-terminal N-glycosylation occurred post-translocationally within a time frame of hours in Xenopus laevis oocytes and minutes in human embryonic kidney 293 (HEK293) cells. In oocyte and HEK cell expression systems, affinity tag-driven C-terminal N-glycosylation may facilitate the determination of orientation of the C-terminal tail of membrane proteins relative to the membrane.
Collapse
Affiliation(s)
- Frauke Pult
- Department of Molecular Pharmacology, RWTH Aachen University of Aachen, Wendlingweg 2, D-52074 Aachen, Germany
| | | | | | | | | | | | | |
Collapse
|
14
|
Abstract
Infection by prions involves conversion of a host-encoded cell surface protein (PrP(C)) to a disease-related isoform (PrP(Sc)). PrP(C) carries two glycosylation sites variably occupied by complex N-glycans, which have been suggested by previous studies to influence the susceptibility to these diseases and to determine characteristics of prion strains. We used the Rov cell system, which is susceptible to sheep prions, to generate a series of PrP(C) glycosylation mutants with mutations at one or both attachment sites. We examined their subcellular trafficking and ability to convert into PrP(Sc) and to sustain stable prion propagation in the absence of wild-type PrP. The susceptibility to infection of mutants monoglycosylated at either site differed dramatically depending on the amino acid substitution. Aglycosylated double mutants showed overaccumulation in the Golgi compartment and failed to be infected. Introduction of an ectopic glycosylation site near the N terminus fully restored cell surface expression of PrP but not convertibility into PrP(Sc), while PrP(C) with three glycosylation sites conferred cell permissiveness to infection similarly to the wild type. In contrast, predominantly aglycosylated molecules with nonmutated N-glycosylation sequons, produced in cells expressing glycosylphosphatidylinositol-anchorless PrP(C), were able to form infectious PrP(Sc). Together our findings suggest that glycosylation is important for efficient trafficking of anchored PrP to the cell surface and sustained prion propagation. However, properly trafficked glycosylation mutants were not necessarily prone to conversion, thus making it difficult in such studies to discern whether the amino acid changes or glycan chain removal most influences the permissiveness to prion infection.
Collapse
|
15
|
Glypican-1 mediates both prion protein lipid raft association and disease isoform formation. PLoS Pathog 2009; 5:e1000666. [PMID: 19936054 PMCID: PMC2773931 DOI: 10.1371/journal.ppat.1000666] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2009] [Accepted: 10/26/2009] [Indexed: 11/28/2022] Open
Abstract
In prion diseases, the cellular form of the prion protein, PrPC, undergoes a conformational conversion to the infectious isoform, PrPSc. PrPC associates with lipid rafts through its glycosyl-phosphatidylinositol (GPI) anchor and a region in its N-terminal domain which also binds to heparan sulfate proteoglycans (HSPGs). We show that heparin displaces PrPC from rafts and promotes its endocytosis, suggesting that heparin competes with an endogenous raft-resident HSPG for binding to PrPC. We then utilised a transmembrane-anchored form of PrP (PrP-TM), which is targeted to rafts solely by its N-terminal domain, to show that both heparin and phosphatidylinositol-specific phospholipase C can inhibit its association with detergent-resistant rafts, implying that a GPI-anchored HSPG targets PrPC to rafts. Depletion of the major neuronal GPI-anchored HSPG, glypican-1, significantly reduced the raft association of PrP-TM and displaced PrPC from rafts, promoting its endocytosis. Glypican-1 and PrPC colocalised on the cell surface and both PrPC and PrPSc co-immunoprecipitated with glypican-1. Critically, treatment of scrapie-infected N2a cells with glypican-1 siRNA significantly reduced PrPSc formation. In contrast, depletion of glypican-1 did not alter the inhibitory effect of PrPC on the β-secretase cleavage of the Alzheimer's amyloid precursor protein. These data indicate that glypican-1 is a novel cellular cofactor for prion conversion and we propose that it acts as a scaffold facilitating the interaction of PrPC and PrPSc in lipid rafts. The prion diseases are unique in that their infectious nature is not dependent on nucleic acid but is instead attributed to a misfolded protein, the prion protein. This misfolded prion protein is capable of inducing the misfolding of the normal form of the prion protein that is present on the surface of neurons and other cells in the body. However, the site in the cell at which this misfolding occurs and whether other proteins are involved remains controversial. We have addressed these questions by investigating how the normal form of the prion protein is targeted to specialised domains on the plasma membrane termed cholesterol-rich lipid rafts. We show that targeting is due, in part, to a particular heparin sulfate proteoglycan called glypican-1. Significantly, reducing the levels of glypican-1 in an infected cell line reduced the accumulation of misfolded prion protein. We propose that glypican-1 acts as a scaffold facilitating the favourable interaction of the misfolded, infectious form of the prion protein with the normal cellular form within cholesterol-rich lipid rafts. Our results indicate that glypican-1 is intimately involved in the misfolding of the prion protein, the critical event in the pathogenesis of prion diseases such as Creutzfeldt-Jakob disease in humans.
Collapse
|
16
|
Taylor DR, Parkin ET, Cocklin SL, Ault JR, Ashcroft AE, Turner AJ, Hooper NM. Role of ADAMs in the ectodomain shedding and conformational conversion of the prion protein. J Biol Chem 2009; 284:22590-600. [PMID: 19564338 PMCID: PMC2755666 DOI: 10.1074/jbc.m109.032599] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The cellular prion protein (PrPC) is essential for the pathogenesis and transmission of prion diseases. PrPC is bound to the plasma membrane via a glycosylphosphatidylinositol anchor, although a secreted, soluble form has also been identified. Previously we reported that PrPC is subject to ectodomain shedding from the membrane by zinc metalloproteinases with a similar inhibition profile to those involved in shedding the amyloid precursor protein. Here we have used gain-of-function (overexpression) and loss-of-function (small interfering RNA knockdown) experiments in cells to identify the ADAMs (adisintegrin and metalloproteinases) involved in the ectodomain shedding of PrPC. These experiments revealed that ADAM9 and ADAM10, but not ADAM17, are involved in the shedding of PrPC and that ADAM9 exerts its effect on PrPC shedding via ADAM10. Using dominant negative, catalytically inactive mutants, we show that the catalytic activity of ADAM9 is required for its effect on ADAM10. Mass spectrometric analysis revealed that ADAM10, but not ADAM9, cleaved PrP between Gly228 and Arg229, three residues away from the site of glycosylphosphatidylinositol anchor attachment. The shedding of another membrane protein, the amyloid precursor protein β-secretase BACE1, by ADAM9 is also mediated via ADAM10. Furthermore, we show that pharmacological inhibition of PrPC shedding or activation of both PrPC and PrPSc shedding by ADAM10 overexpression in scrapie-infected neuroblastoma N2a cells does not alter the formation of proteinase K-resistant PrPSc. Collectively, these data indicate that although PrPC can be shed through the action of ADAM family members, modulation of PrPC or PrPSc ectodomain shedding does not regulate prion conversion.
Collapse
Affiliation(s)
- David R Taylor
- Proteolysis Research Group, Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | | | | | | | | | | | | |
Collapse
|
17
|
Kang D, Yoo JS, Kim MO, Moon MH. A soft preparative method for membrane proteome analysis using frit inlet asymmetrical flow field-flow fractionation: application in a prostatic cancer cell line. J Proteome Res 2009; 8:982-91. [PMID: 19140673 DOI: 10.1021/pr800689y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Membrane proteins participate in a number of important biological functions such as signal transduction, molecular transport, and cell-cell interactions. However, due to the nature of membrane proteins, the development of a preparative method that produces a sufficient yield of purified membrane proteins from the cell remains a challenge. In the present study, frit inlet asymmetrical flow field-flow fractionation (FI-AFlFFF) was employed to fractionate membrane fragments containing membrane proteins from free cytoplasmic proteins of prostatic cancer cell (DU145 cell) lysates. The isolated membrane proteins were then digested and analyzed by nanoflow liquid chromatography/tandem mass spectrometry (nLC-ESI-MS-MS). Since fractionation of the cell lysate mixtures containing membrane fragments and cytoplasmic proteins could be achieved based on the differences of their sizes in FI-AFlFFF, membrane fragments were partially isolated from the cytoplasmic proteins and collected. The performance of FI-AFlFFF for prefractionation of the membrane proteome was examined by comparing the number of membrane proteins that were identified with the number identified using an ultracentrifugation method. The application of FI-AFlFFF to membrane proteomics produced an increased yield of purified membrane proteins with fewer cytoplasmic proteins compared to a conventional ultracentrifugation method.
Collapse
Affiliation(s)
- Dukjin Kang
- Department of Chemistry, Yonsei University, Seoul, 120-749, South Korea
| | | | | | | |
Collapse
|
18
|
Rajasekaran S, Balla S, Gradie P, Gryk MR, Kadaveru K, Kundeti V, Maciejewski MW, Mi T, Rubino N, Vyas J, Schiller MR. Minimotif miner 2nd release: a database and web system for motif search. Nucleic Acids Res 2009; 37:D185-90. [PMID: 18978024 PMCID: PMC2686579 DOI: 10.1093/nar/gkn865] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Accepted: 10/16/2008] [Indexed: 11/24/2022] Open
Abstract
Minimotif Miner (MnM) consists of a minimotif database and a web-based application that enables prediction of motif-based functions in user-supplied protein queries. We have revised MnM by expanding the database more than 10-fold to approximately 5000 motifs and standardized the motif function definitions. The web-application user interface has been redeveloped with new features including improved navigation, screencast-driven help, support for alias names and expanded SNP analysis. A sample analysis of prion shows how MnM 2 can be used. Weblink: http://mnm.engr.uconn.edu, weblink for version 1 is http://sms.engr.uconn.edu.
Collapse
Affiliation(s)
- Sanguthevar Rajasekaran
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06029-2155, Department of Molecular, Microbial, and Structural Biology, Biological System Modeling Group, University of Connecticut Health Center, 263 Farmington Ave. Farmington, CT 06030-3305 and Memorial Sloan-Kettering Cancer Center, NY 10021, USA
| | - Sudha Balla
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06029-2155, Department of Molecular, Microbial, and Structural Biology, Biological System Modeling Group, University of Connecticut Health Center, 263 Farmington Ave. Farmington, CT 06030-3305 and Memorial Sloan-Kettering Cancer Center, NY 10021, USA
| | - Patrick Gradie
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06029-2155, Department of Molecular, Microbial, and Structural Biology, Biological System Modeling Group, University of Connecticut Health Center, 263 Farmington Ave. Farmington, CT 06030-3305 and Memorial Sloan-Kettering Cancer Center, NY 10021, USA
| | - Michael R. Gryk
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06029-2155, Department of Molecular, Microbial, and Structural Biology, Biological System Modeling Group, University of Connecticut Health Center, 263 Farmington Ave. Farmington, CT 06030-3305 and Memorial Sloan-Kettering Cancer Center, NY 10021, USA
| | - Krishna Kadaveru
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06029-2155, Department of Molecular, Microbial, and Structural Biology, Biological System Modeling Group, University of Connecticut Health Center, 263 Farmington Ave. Farmington, CT 06030-3305 and Memorial Sloan-Kettering Cancer Center, NY 10021, USA
| | - Vamsi Kundeti
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06029-2155, Department of Molecular, Microbial, and Structural Biology, Biological System Modeling Group, University of Connecticut Health Center, 263 Farmington Ave. Farmington, CT 06030-3305 and Memorial Sloan-Kettering Cancer Center, NY 10021, USA
| | - Mark W. Maciejewski
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06029-2155, Department of Molecular, Microbial, and Structural Biology, Biological System Modeling Group, University of Connecticut Health Center, 263 Farmington Ave. Farmington, CT 06030-3305 and Memorial Sloan-Kettering Cancer Center, NY 10021, USA
| | - Tian Mi
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06029-2155, Department of Molecular, Microbial, and Structural Biology, Biological System Modeling Group, University of Connecticut Health Center, 263 Farmington Ave. Farmington, CT 06030-3305 and Memorial Sloan-Kettering Cancer Center, NY 10021, USA
| | - Nicholas Rubino
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06029-2155, Department of Molecular, Microbial, and Structural Biology, Biological System Modeling Group, University of Connecticut Health Center, 263 Farmington Ave. Farmington, CT 06030-3305 and Memorial Sloan-Kettering Cancer Center, NY 10021, USA
| | - Jay Vyas
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06029-2155, Department of Molecular, Microbial, and Structural Biology, Biological System Modeling Group, University of Connecticut Health Center, 263 Farmington Ave. Farmington, CT 06030-3305 and Memorial Sloan-Kettering Cancer Center, NY 10021, USA
| | - Martin R. Schiller
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06029-2155, Department of Molecular, Microbial, and Structural Biology, Biological System Modeling Group, University of Connecticut Health Center, 263 Farmington Ave. Farmington, CT 06030-3305 and Memorial Sloan-Kettering Cancer Center, NY 10021, USA
| |
Collapse
|
19
|
Association of a GPI-anchored protein with detergent-resistant membranes facilitates its trafficking through the early secretory pathway. Exp Cell Res 2009; 315:348-56. [DOI: 10.1016/j.yexcr.2008.10.038] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2008] [Revised: 10/19/2008] [Accepted: 10/24/2008] [Indexed: 11/21/2022]
|
20
|
Walmsley AR, Watt NT, Taylor DR, Perera WSS, Hooper NM. alpha-cleavage of the prion protein occurs in a late compartment of the secretory pathway and is independent of lipid rafts. Mol Cell Neurosci 2008; 40:242-8. [PMID: 19056496 DOI: 10.1016/j.mcn.2008.10.012] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2008] [Revised: 10/17/2008] [Accepted: 10/28/2008] [Indexed: 11/27/2022] Open
Abstract
Endoproteolysis of the cellular prion protein (PrP(C)) modulates both the normal function of the protein and the pathogenesis of the neurodegenerative prion diseases. PrP(C) undergoes alpha-cleavage to generate the N-terminally truncated fragment C1. Utilizing various constructs of PrP(C) expressed in human neuroblastoma cells we investigated the subcellular compartment where alpha-cleavage occurs. C1 was detected at the cell surface and the generation of C1 occurred in mutants of PrP(C) incapable of Cu2+-mediated endocytosis. A transmembrane-anchored form that is not lipid raft-localised, as well as a secreted construct lacking the glycosyl-phosphatidylinositol membrane anchor, were also subject to alpha-cleavage. However, when this transmembrane-anchored form was modified with an endoplasmic reticulum retention motif, C1 was not formed. Inhibition of protein export from the Golgi by temperature block increased the amount of C1. Our data thus demonstrate that the alpha-cleavage of PrP(C) occurs predominantly in a raft-independent manner in a late compartment of the secretory pathway.
Collapse
Affiliation(s)
- Adrian R Walmsley
- Proteolysis Research Group, Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, and Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds LS29JT, UK
| | | | | | | | | |
Collapse
|
21
|
Schubert T, Bärmann M, Rusp M, Gränzer W, Tanaka M. Diffusion of glycosylphosphatidylinositol (GPI)-anchored bovine prion protein (PrPc) in supported lipid membranes studied by single-molecule and complementary ensemble methods. J Memb Sci 2008. [DOI: 10.1016/j.memsci.2007.10.058] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
|
22
|
Griffiths HH, Morten IJ, Hooper NM. Emerging and potential therapies for Alzheimer's disease. Expert Opin Ther Targets 2008; 12:693-704. [DOI: 10.1517/14728222.12.6.693] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
|
23
|
Dupiereux I, Falisse-Poirrier N, Zorzi W, Watt NT, Thellin O, Zorzi D, Pierard O, Hooper NM, Heinen E, Elmoualij B. Protective effect of prion protein via the N-terminal region in mediating a protective effect on paraquat-induced oxidative injury in neuronal cells. J Neurosci Res 2008; 86:653-9. [PMID: 17896796 DOI: 10.1002/jnr.21506] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Transmissible spongiform encephalopathies are a group of neurodegenerative disorders caused by a posttranslational, conformational change in the cellular isoform of the prion protein (PrP(C)) into an infectious, disease-associated form (PrP(Sc)). Increasing evidence supports a role for PrP(C) in the cellular response to oxidative stress. We investigated the effect of oxidative stress mediated by paraquat exposure on SH-SY5Y neuroblastoma cells. A loss of mitochondrial membrane potential and subsequent reduction in ATP production were demonstrated in untransfected SH-SY5Y cells, an effect that was ameliorated by the expression of PrP(C). Cells expressing either PrP-DeltaOct, which lacks the octapeptide repeats, or PrP-DA, in which the N-terminus is tethered to the membrane, showed increased sensitivity to paraquat compared with cells expressing wild-type PrP(C) as shown by reduced viability, loss of their membrane integrity, and reduced mitochondrial bioenergetic measurements. Exposure of prion-infected mouse SMB15S cells to paraquat resulted in a reduction in viability to levels similar to those seen in the untransfected SH-SY5Y cells. However, "curing" the cells with pentosan sulfate restored the viability to the level observed in the SH-SY5Y cells expressing PrP(C). These data would indicate that the molecular mechanism promoting cellular resistance to oxidative stress had been compromised in the infected SMB15S cells, which could be reinstated upon curing. Our study supports the hypothesis that PrP(C) expression protects cells against paraquat-induced oxidative injury, demonstrates the significance of the N-terminal region of the protein in mediating this protective effect, and also shows that the biochemical consequences of prion infection may be reversed with therapeutic intervention.
Collapse
Affiliation(s)
- Ingrid Dupiereux
- Department of Human Histology-CRPP, University of Liège, Sart Tilman, Liège, Belgium
| | | | | | | | | | | | | | | | | | | |
Collapse
|
24
|
Hooper NM, Turner AJ. A new take on prions: preventing Alzheimer's disease. Trends Biochem Sci 2008; 33:151-5. [DOI: 10.1016/j.tibs.2008.01.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2007] [Revised: 01/11/2008] [Accepted: 01/16/2008] [Indexed: 12/31/2022]
|
25
|
Abstract
Subcellular fractionation is central to a range of cell biological, biochemical and proteomic studies. Purification of nuclear-enriched fractions is critical for studies on nuclear structure and function. Here we show that detergent-based nuclear isolation methods cause the redistribution of proteins associated with plasma membrane lipid rafts into nuclear fractions. The glycosyl-phosphatidylinositol (GPI)-anchored prion protein (PrP(C)) and a GPI-anchored construct of angiotensin converting enzyme (GPI-ACE), as well as the lipid raft markers flotillin-1 and -2, were present in the nuclear fractions derived using three different subcellular fractionation protocols. Incubation of intact cells with bacterial phosphatidylinositol-specific phospholipase C (PI-PLC), which cleaves GPI-anchored proteins from the cell surface, significantly reduced the amount of PrP(C) and GPI-ACE in the nuclear fraction. Buoyant sucrose density gradient centrifugation in the presence of Triton X-100 of the nuclear fraction resulted in a significant proportion of the GPI-anchored proteins being recovered in the low density lipid raft fractions. These data indicate that the nuclear fraction isolated using such subcellular fractionation protocols is contaminated with components of plasma membrane lipid rafts and raises questions as to the integrity of the nuclear fraction isolated by such protocols for use in detailed cell biological studies and proteomics analysis.
Collapse
Affiliation(s)
- Yee-How Say
- Proteolysis Research Group, Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | | |
Collapse
|
26
|
Orsi A, Sitia R. Interplays between covalent modifications in the endoplasmic reticulum increase conformational diversity in nascent prion protein. Prion 2007; 1:236-42. [PMID: 19164910 DOI: 10.4161/pri.1.4.5727] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Prion protein (PrP), the causative agent of transmissible spongiform encephalopathies, is synthesized in the endoplasmic reticulum (ER) where it undergoes numerous covalent modifications. Here we investigate the interdependence and regulation of PrP oxidative folding, N-glycosylation and GPI addition in diverse ER conditions. Our results show that formation of the single disulphide bond is a pivotal event, essential for PrP transport, and can occur post-translationally. Retarding its formation enhances N-glycosylation and GPI-anchoring. In contrast, lowering ER Ca(2+) concentration inhibits N-glycosylation and GPI-anchoring. These data reveal tight interplays between the different ER covalent modifications, which collectively increase of PrP conformational diversity and may be important for its propagation.
Collapse
Affiliation(s)
- Andrea Orsi
- Università Vita-Salute San Raffaele Scientific Institute, Milano, Italy
| | | |
Collapse
|
27
|
Watanabe K, Hamada S, Bianco C, Mancino M, Nagaoka T, Gonzales M, Bailly V, Strizzi L, Salomon DS. Requirement of glycosylphosphatidylinositol anchor of Cripto-1 for trans activity as a Nodal co-receptor. J Biol Chem 2007; 282:35772-86. [PMID: 17925387 DOI: 10.1074/jbc.m707351200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cripto-1 (CR-1) has an indispensable role as a Nodal co-receptor for patterning of body axis in embryonic development. CR-1 is reported to have a paracrine activity as a Nodal co-receptor, although CR-1 is primarily produced as a glycosylphosphatidylinositol (GPI)-anchored membrane protein. Regulation of cis and trans function of CR-1 should be important to establish the precise body patterning. However, the mechanism by which GPI-anchored CR-1 can act in trans is not well known. Here we confirmed the paracrine activity of CR-1 by fluorescent cell-labeling and immunofluorescent staining. We generated COOH-terminal-truncated soluble forms of CR-1 based on the attachment site for the GPI moiety (omega-site), which we identified in the present study. GPI-anchored CR-1 has a significantly higher activity than COOH-terminal-truncated soluble forms to induce Nodal signal in trans as well as in cis. Moreover, transmembrane forms of CR-1 partially retained their ability to induce Nodal signaling only when type I receptor Activin-like kinase 4 was overexpressed. NTERA2/D1 cells, which express endogenous CR-1, lost the cell-surface expression of CR-1 after phosphatidylinositol-phospholipase C treatment and became refractory to stimulation of Nodal. These observations suggest that GPI attachment of CR-1 is required for the paracrine activity as a Nodal co-receptor.
Collapse
Affiliation(s)
- Kazuhide Watanabe
- Tumor Growth Factor Section, Mammary Biology and Tumorigenesis Laboratory, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
28
|
Watt NT, Routledge MN, Wild CP, Hooper NM. Cellular prion protein protects against reactive-oxygen-species-induced DNA damage. Free Radic Biol Med 2007; 43:959-67. [PMID: 17697940 DOI: 10.1016/j.freeradbiomed.2007.06.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2007] [Revised: 04/26/2007] [Accepted: 06/05/2007] [Indexed: 11/26/2022]
Abstract
Although the cellular form of the prion protein (PrPC) is critical for the development of prion disease through its conformational conversion into the infectious form (PrPSc), the physiological role of PrPC is less clear. Using alkaline single-cell gel electrophoresis (the Comet assay), we show that expression of PrPC protects human neuroblastoma SH-SY5Y cells against DNA damage under basal conditions and following exposure to reactive oxygen species, either hydroxyl radicals following exposure to Cu2+ or Fe2+ or singlet oxygen following exposure to the photosensitizer methylene blue and white light. Cells expressing either PrPDeltaoct which lacks the octapeptide repeats or the prion-disease-associated mutants A116V or PG14 had increased levels of DNA damage compared to cells expressing PrPC. In PrPSc-infected mouse ScN2a cells there was a significant increase in DNA damage over noninfected N2a cells (median tail DNA 2.87 and 7.33%, respectively). Together, these data indicate that PrPC has a critical role to play in protecting cells against reactive-oxygen-species-mediated DNA damage; a function which requires the octapeptide repeats in the protein, is lost in disease-associated mutants of the protein or upon conversion to PrPSc, and thus provide further support for the neuroprotective role for PrPC.
Collapse
Affiliation(s)
- Nicole T Watt
- Proteolysis Research Group, Institute of Molecular and Cellular Biology, Faculty of Biological Sciences and Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds LS2 9JT, UK
| | | | | | | |
Collapse
|
29
|
Parkin ET, Watt NT, Hussain I, Eckman EA, Eckman CB, Manson JC, Baybutt HN, Turner AJ, Hooper NM. Cellular prion protein regulates beta-secretase cleavage of the Alzheimer's amyloid precursor protein. Proc Natl Acad Sci U S A 2007; 104:11062-7. [PMID: 17573534 PMCID: PMC1904148 DOI: 10.1073/pnas.0609621104] [Citation(s) in RCA: 203] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Proteolytic processing of the amyloid precursor protein (APP) by beta-secretase, beta-site APP cleaving enzyme (BACE1), is the initial step in the production of the amyloid beta (Abeta) peptide, which is involved in the pathogenesis of Alzheimer's disease. The normal cellular function of the prion protein (PrP(C)), the causative agent of the transmissible spongiform encephalopathies such as Creutzfeldt-Jakob disease in humans, remains enigmatic. Because both APP and PrP(C) are subject to proteolytic processing by the same zinc metalloproteases, we tested the involvement of PrP(C) in the proteolytic processing of APP. Cellular overexpression of PrP(C) inhibited the beta-secretase cleavage of APP and reduced Abeta formation. Conversely, depletion of PrP(C) in mouse N2a cells by siRNA led to an increase in Abeta peptides secreted into the medium. In the brains of PrP knockout mice and in the brains from two strains of scrapie-infected mice, Abeta levels were significantly increased. Two mutants of PrP, PG14 and A116V, that are associated with familial human prion diseases failed to inhibit the beta-secretase cleavage of APP. Using constructs of PrP, we show that this regulatory effect of PrP(C) on the beta-secretase cleavage of APP required the localization of PrP(C) to cholesterol-rich lipid rafts and was mediated by the N-terminal polybasic region of PrP(C) via interaction with glycosaminoglycans. In conclusion, this is a mechanism by which the cellular production of the neurotoxic Abeta is regulated by PrP(C) and may have implications for both Alzheimer's and prion diseases.
Collapse
Affiliation(s)
- Edward T. Parkin
- *Proteolysis Research Group, Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, and
- Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Nicole T. Watt
- *Proteolysis Research Group, Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, and
- Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Ishrut Hussain
- Neurodegeneration Research, Neurology and Gastrointestinal Centre of Excellence for Drug Discovery, GlaxoSmithKline Research and Development Limited, Third Avenue, Harlow, Essex CM19 5AW, United Kingdom
| | | | | | - Jean C. Manson
- Roslin Institute, Neuropathogenesis Unit, Edinburgh EH9 3JF, United Kingdom
| | - Herbert N. Baybutt
- Roslin Institute, Neuropathogenesis Unit, Edinburgh EH9 3JF, United Kingdom
| | - Anthony J. Turner
- *Proteolysis Research Group, Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, and
| | - Nigel M. Hooper
- *Proteolysis Research Group, Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, and
- Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds LS2 9JT, United Kingdom
- **To whom correspondence should be addressed. E-mail:
| |
Collapse
|
30
|
van Rosmalen JWG, Martens GJM. Mutagenesis studies in transgenic Xenopus intermediate pituitary cells reveal structural elements necessary for correct prion protein biosynthesis. Dev Neurobiol 2007; 67:715-27. [PMID: 17443819 DOI: 10.1002/dneu.20351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The cellular prion protein (PrP(C)) is generally accepted to be involved in the development of prion diseases, but its physiological role is still under debate. To obtain more insight into PrP(C) functioning, we here used stable Xenopus transgenesis in combination with the proopiomelanocortin (POMC) gene promoter to express mutated forms of Xenopus PrP(C) fused to the C-terminus of the green fluorescent protein (GFP) specifically in the neuroendocrine Xenopus intermediate pituitary melanotrope cells. Similar to GFP-PrP(C), the newly synthesized GFP-PrP(C)K81A mutant protein was stepwise mono- and di-N-glycosylated to 48- and 51-kDa forms, respectively, and eventually complex glycosylated to yield a 55-kDa mature form. Unlike GFP-PrP(C), the mature GFP-PrP(C)K81A mutant protein was not cleaved, demonstrating the endoproteolytic processing of Xenopus PrP(C) at lysine residue 81. Surprisingly, removal of the glycosylphosphatidylinositol (GPI) anchor signal sequence or insertion of an octarepeat still allowed N-linked glycosylation, but the GFP-PrP(C)DeltaGPI and GFP-PrP(C)octa mutant proteins were not complex glycosylated and not cleaved, indicating that the GPI/octa mutants did not reach the mid-Golgi compartment of the secretory pathway. The transgene expression of the mutant proteins did not affect the ultrastructure of the melanotrope cells nor POMC biosynthesis and processing, or POMC-derived peptide secretion. Together, our findings reveal the evolutionary conservation of the site of metabolic cleavage and the importance of the presence of the GPI anchor and the absence of the octarepeat in Xenopus PrP(C) for its correct biosynthesis.
Collapse
Affiliation(s)
- Jos W G van Rosmalen
- Department of Molecular Animal Physiology, Nijmegen Center for Molecular Life Sciences, Institute for Neuroscience, Faculty of Science, Radboud University Nijmegen, 6525 GA Nijmegen, The Netherlands
| | | |
Collapse
|
31
|
Dupiereux I, Zorzi W, Rachidi W, Zorzi D, Pierard O, Lhereux B, Heinen E, Elmoualij B. Study on the toxic mechanism of prion protein peptide 106-126 in neuronal and non neuronal cells. J Neurosci Res 2006; 84:637-46. [PMID: 16786576 DOI: 10.1002/jnr.20965] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A synthetic peptide corresponding to the 106-126 amyloidogenic region of the cellular human prion protein (PrP(c)) is useful for in vitro study of prion-induced neuronal cell death. The aim of the present work was to examine the implication of the cellular prion protein in the toxicity mechanism induced by PrP 106-126. The effect of PrP 106-126 was investigated both on human neuroblastoma SH-SY5Y cells and on SH-SY5Y overexpressing murine cellular prions (wtPrP). We show by metabolic assay tests and ATP assays that PrP(c) expression does not modulate the toxicity of the prion peptide. Moreover, we investigated the effect of this peptide on an established non neuronal model, rabbit kidney epithelial A74 cells that express a doxycycline-inducible murine PrP(c) gene. We show for the first time that the prion peptide 106-126 does not exert any toxic effect on this cell line in the presence or absence of doxycycline. Our results show that the PrP 106-126-induced cell alteration is independent of PrP(c) expression. Rather, it seems to act via an interaction with lipidic components of the plasma membrane as strengthened by our results showing the differential susceptibility of neuronal and non neuronal cell lines that significantly differ by their membrane fatty acid composition.
Collapse
Affiliation(s)
- Ingrid Dupiereux
- Department of Human Histology, CRPP, University of Liège, Institute of Pharmacy-CHU, Sart Tilman, Liège, Belgium
| | | | | | | | | | | | | | | |
Collapse
|
32
|
Wurm S, Wechselberger C. Prion protein modifies TGF-β induced signal transduction. Biochem Biophys Res Commun 2006; 349:525-32. [PMID: 16942751 DOI: 10.1016/j.bbrc.2006.08.074] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2006] [Accepted: 08/11/2006] [Indexed: 10/24/2022]
Abstract
Members of the transforming growth factor-beta (TGF-beta) superfamily regulate a multitude of cellular processes as well as the expression of various proteins such as, e.g., matrix metalloproteinases (MMPs). These endopeptidases selectively degrade components of the extracellular matrix as well as non-matrix substrates like growth factors and cell surface receptors. MMPs are activated during embryonic development, morphogenesis, and tissue resorption/remodeling as well as in pathological conditions such as deranged wound healing and cancer metastasis. In this report we demonstrate that over-expression of cellular prion protein in mouse mammary gland epithelial cells is able to modulate TGF-beta induced signal transduction leading to a synergistic increase of secreted MMP-2 activity. This correlates with elevated substrate detachment of cells grown as an epithelial monolayer as well as interfering with morphogenesis of cells cultured in a three-dimensional collagen type I matrix.
Collapse
Affiliation(s)
- Susanne Wurm
- Upper Austrian Research GmbH, Center for Biomedical Nanotechnology, 4020 Linz, Austria
| | | |
Collapse
|
33
|
Biswas S, Langeveld JPM, Tipper D, Lu S. Intracellular accumulation of a 46 kDa species of mouse prion protein as a result of loss of glycosylation in cultured mammalian cells. Biochem Biophys Res Commun 2006; 349:153-61. [PMID: 16935263 DOI: 10.1016/j.bbrc.2006.08.035] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2006] [Accepted: 08/04/2006] [Indexed: 11/18/2022]
Abstract
Prion diseases are fatal neurodegenerative disorders characterized by the accumulation of an abnormal isoform (PrPSc) of the normal cellular prion protein (PrPC) in the brain. Reportedly, abnormal N-linked glycosylation patterns in PrPC are associated with disease susceptibility; thus, we compared the glycosylation status of normal and several mutant forms of the murine prion protein (MuPrP) in cultured mammalian cells. Substitution of the N-terminal signal sequence of normal MuPrP with a heterologous signal peptide did not alter glycosylation. When expressed without the C-terminal glycophosphatidylinositol anchor signal, the majority of MuPrP remained intracellular and unglycosylated, and a 46 kDa species (p46) of the unglycosylated PrPC was detected on reducing gels. p46 was also observed when wild-type MuPrP was expressed in the presence of tunicamycin or enzymatically deglycosylated in vitro. A rabbit polyclonal anti-serum raised against dimeric MuPrP cross-reacted with p46 and localized the signal within the Golgi apparatus. We propose that the 46 kDa signal is a dimeric form of MuPrP and in the light of recent studies, it can be argued that a relatively stable, non-glycosylated, cytoplasmic PrPC dimer, produced as a result of compromised glycosylation is an intermediate in initiating conversion of PrPC to PrPSc in sporadic transmissible spongiform encephalopathies.
Collapse
Affiliation(s)
- Subhabrata Biswas
- Laboratory of Nucleic Acid Vaccines, Department of Medicine, University of Massachusetts Medical School, 364 Plantation St., Worcester, MA 01605, USA
| | | | | | | |
Collapse
|
34
|
Hooper NM. Glycosylation and GPI anchorage of the prion protein. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2006; 564:95-6. [PMID: 16400810 DOI: 10.1007/0-387-25515-x_14] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Affiliation(s)
- N M Hooper
- School of Biochemistry and Microbiology, Leeds Institute for Genetics, Health and Therapeutics, University of Leeds, Leeds, UK
| |
Collapse
|
35
|
Taylor DR, Watt NT, Perera WSS, Hooper NM. Assigning functions to distinct regions of the N-terminus of the prion protein that are involved in its copper-stimulated, clathrin-dependent endocytosis. J Cell Sci 2005; 118:5141-53. [PMID: 16254249 DOI: 10.1242/jcs.02627] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The cellular prion protein (PrPC) is essential for the pathogenesis and transmission of prion diseases. Although PrPC is known to be located in detergent-insoluble lipid rafts at the surface of neuronal cells, the mechanism of its internalisation is unclear, with both raft/caveolae-based and clathrin-mediated processes being proposed. We have investigated the mechanism of copper-induced internalisation of PrPC in neuronal cells by immunofluorescence microscopy, surface biotinylation assays and buoyant sucrose density gradient centrifugation in the presence of Triton X-100. Clathrin-mediated endocytosis was selectively blocked with tyrphostin A23, which disrupts the interaction between tyrosine motifs in the cytosolic domains of integral membrane proteins and the adaptor complex AP2, and a dominant-negative mutant of the adaptor protein AP180. Both these agents inhibited the copper-induced endocytosis of PrPC. Copper caused PrPC to move laterally out of detergent-insoluble lipid rafts into detergent-soluble regions of the plasma membrane. Using mutants of PrPC that lack either the octapeptide repeats or the N-terminal polybasic region, and a construct with a transmembrane anchor, we show that copper binding to the octapeptide repeats promotes dissociation of PrPC from lipid rafts, whereas the N-terminal polybasic region mediates its interaction with a transmembrane adaptor protein that engages the clathrin endocytic machinery. Our results provide an experimental basis for reconciling the apparently contradictory observations that the prion protein undergoes clathrin-dependent endocytosis despite being localised in lipid rafts. In addition, we have been able to assign distinct functions in the endocytic process to separate regions of the protein.
Collapse
Affiliation(s)
- David R Taylor
- Proteolysis Research Group, School of Biochemistry and Microbiology, Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds LS2 9JT, UK
| | | | | | | |
Collapse
|
36
|
Watt NT, Taylor DR, Gillott A, Thomas DA, Perera WSS, Hooper NM. Reactive Oxygen Species-mediated β-Cleavage of the Prion Protein in the Cellular Response to Oxidative Stress. J Biol Chem 2005; 280:35914-21. [PMID: 16120605 DOI: 10.1074/jbc.m507327200] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cellular prion protein (PrP(C)) is critical for the development of prion diseases. However, the physiological role of PrP(C) is less clear, although a role in the cellular resistance to oxidative stress has been proposed. PrP(C) is cleaved at the end of the copper-binding octapeptide repeats through the action of reactive oxygen species (ROS), a process termed beta-cleavage. Here we show that ROS-mediated beta-cleavage of cell surface PrP(C) occurs within minutes and was inhibited by the hydroxyl radical quencher dimethyl sulfoxide and by an antibody against the octapeptide repeats. A construct of PrP lacking the octapeptide repeats, PrPDeltaoct, failed to undergo ROS-mediated beta-cleavage, as did two mutant forms of PrP, PG14 and A116V, associated with human prion diseases. As compared with cells expressing wild type PrP, when challenged with H2O2 and Cu2+, cells expressing PrPdeltaoct, PG14, or A116V had reduced viability and glutathione peroxidase activity and increased intracellular free radicals. Thus, lack of ROS-mediated beta-cleavage of PrP correlated with the sensitivity of the cells to oxidative stress. These data indicate that the beta-cleavage of PrP(C) is an early and critical event in the mechanism by which PrP protects cells against oxidative stress.
Collapse
Affiliation(s)
- Nicole T Watt
- Proteolysis Research Group, School of Biochemistry and Microbiology, Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds LS2 9JT, United Kingdom
| | | | | | | | | | | |
Collapse
|
37
|
Abstract
The transmissible spongiform encephalopathies (TSE), or prion diseases are a group of transmissible neurodegenerative disorders of humans and animals. Although the infectious agent (the 'prion') has not yet been formally defined at the molecular level, much evidence exists to suggest that the major or sole component is an abnormal isoform of the host encoded prion protein (PrP). Different strains or isolates of the infectious agent exist, which exhibit characteristic disease phenotypes when transmitted to susceptible animals. In the absence of a nucleic acid genome it has been hard to accommodate the existence of TSE strains within the protein-only model of prion replication. Recent work examining the conformation and glycosylation patterns of disease-associated PrP has shown that these post-translational modifications show strain-specific properties and contribute to the molecular basis of TSE strain variation. This article will review the role of glycosylation in the susceptibility of cellular PrP to conversion to the disease-associated conformation and the role of glycosylation as a marker of TSE strain type.
Collapse
Affiliation(s)
- Victoria A Lawson
- Department of Pathology, Centre for Neuroscience, and Mental Health Research Institute of Victoria, University of Melbourne, Parkville, Australia
| | | | | | | |
Collapse
|
38
|
Walmsley AR, McCombie G, Neumann U, Marcellin D, Hillenbrand R, Mir AK, Frentzel S. Zinc metalloproteinase-mediated cleavage of the human Nogo-66 receptor. J Cell Sci 2005; 117:4591-602. [PMID: 15331667 DOI: 10.1242/jcs.01324] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The central nervous system myelin components oligodendrocyte-myelin glycoprotein, myelin-associated glycoprotein and the Nogo-66 domain of Nogo-A inhibit neurite outgrowth by binding the neuronal glycosyl-phosphatidylinositol-anchored Nogo-66 receptor (NgR) that transduces the inhibitory signal to the cell interior via a transmembrane co-receptor, p75NTR. Here, we demonstrate that human NgR expressed in human neuroblastoma cells is constitutively cleaved in a post-ER compartment to generate a lipid-raft associated C-terminal fragment that is present on the cell surface and a soluble N-terminal fragment that is released into the medium. Mass spectrometric analysis demonstrated that the N-terminal fragment terminated just after the C-terminus of the ligand-binding domain of NgR. In common with other shedding mechanisms, the release of this fragment was blocked by a hydroxamate-based inhibitor of zinc metalloproteinases, but not by inhibitors of other protease classes and up-regulated by treatment with the cellular cholesterol depleting agent methyl-beta-cyclodextrin. The N-terminal fragment bound Nogo-66 and blocked Nogo-66 binding to cell surface NgR but failed to associate with p75NTR, indicative of a role as a Nogo-66 antagonist. Furthermore, the N- and C-terminal fragments of NgR were detectable in human brain cortex and the N-terminal fragment was also present in human cerebrospinal fluid, demonstrating that NgR proteolysis occurs within the human nervous system. Our findings thus identify a potential cellular mechanism for the regulation of NgR function at the level of the receptor.
Collapse
Affiliation(s)
- Adrian R Walmsley
- Novartis Institutes for BioMedical Research, 4002 Basel, Switzerland.
| | | | | | | | | | | | | |
Collapse
|
39
|
Wojczyk BS, Takahashi N, Levy MT, Andrews DW, Abrams WR, Wunner WH, Spitalnik SL. N-glycosylation at one rabies virus glycoprotein sequon influences N-glycan processing at a distant sequon on the same molecule. Glycobiology 2005; 15:655-66. [PMID: 15677380 DOI: 10.1093/glycob/cwi046] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Rabies glycoprotein (RGP(WT)) contains N-glycosylation sequons at Asn(37), Asn(247), and Asn(319), although Asn(37) is not efficiently glycosylated. To examine N-glycan processing at Asn(247) and Asn(319), full-length glycosylation mutants, RGP(-2-) and RGP(--3), were expressed, and Endo H sensitivity was compared. When the Asn(247) sequon is present alone in RGP(-2-), 90% of its N-glycans are high-mannose type, whereas only 35% of the N-glycans at Asn(319) in RGP(--3) are high-mannose. When both sequons are present in RGP(-23), 87% of the N-glycans are of complex type. The differing patterns of Endo H sensitivity at sequons present individually or together suggests that glycosylation of one sequon affects glycosylation at another, distant sequon. To explore this further, we constructed soluble forms of RGP: RGP(WT)T441His and RGP(--3)T441His. Tryptic glycopeptides from these purified secreted proteins were isolated by HPLC and characterized by a 3D oligosaccharide mapping technique. RGP(WT)T441His had fucosylated, bi- and triantennary complex type glycans at Asn(247) and Asn(319). However, Asn(247) had half as many neutral glycans, more monosialylated glycans, and fewer disialylated glycans when compared with Asn(319). Moreover, when comparing the N-glycans at Asn(319) on RGP(--3)T441His and RGP(WT)T441His, the former had 30% more neutral, 28% more monosialylated, and 33% fewer disialylated glycans. This suggests that the N-glycan at Asn(247) allows additional N-glycan processing to occur at Asn(319), yielding more heavily sialylated bi- and triantennary forms. The mechanism(s) by which glycosylation at one sequon influences N-glycan processing at a distant sequon on the same glycoprotein remains to be determined.
Collapse
Affiliation(s)
- Boguslaw S Wojczyk
- Department of Pathology, College of Physicians and Surgeons of Columbia University, 630 West 168th Street, New York, NY 10032, USA
| | | | | | | | | | | | | |
Collapse
|
40
|
Abstract
A hallmark of prion diseases in humans and animals is the conversion of the cellular prion protein PrPc to a pathogenic isoform, denoted PrPSc. PrPSc is characterized by distinct biochemical and biophysical properties; in addition, it is the major component of infectious prions. All available data indicate that the only difference between PrPc and PrPSc resides in their conformation, emphasizing a critical role of protein folding in the pathogenesis of prion diseases.
Collapse
Affiliation(s)
- Jorg Tatzelt
- Department of Cellular Biochemistry, Max-Planck-Institute for Biochemistry, D-82152 Martinsried, Germany.
| | | |
Collapse
|
41
|
Parkin ET, Watt NT, Turner AJ, Hooper NM. Dual Mechanisms for Shedding of the Cellular Prion Protein. J Biol Chem 2004; 279:11170-8. [PMID: 14711812 DOI: 10.1074/jbc.m312105200] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cellular prion protein (PrP(C)) is essential for the pathogenesis and transmission of prion diseases. Whereas the majority of PrP(C) is bound to the cell membrane via a glycosylphosphatidylinositol (GPI) anchor, a secreted form of the protein has been identified. Here we show that PrP(C) can be shed into the medium of human neuroblastoma SH-SY5Y cells by both protease- and phospholipase-mediated mechanisms. The constitutive shedding of PrP(C) was inhibited by a range of hydroxamate-based zinc metalloprotease inhibitors in a manner identical to the alpha-secretase-mediated shedding of the amyloid precursor protein, indicating a proteolytic shedding mechanism. Like amyloid precursor protein, this zinc metalloprotease-mediated shedding of PrP(C) could be stimulated by phorbol myristate acetate and by copper ions. The lipid raft-disrupting agents filipin and methyl-beta-cyclodextrin promoted the shedding of PrP(C) via a distinct mechanism that was not inhibited by hydroxamate-based inhibitors. Filipin-mediated shedding of PrP(C) is likely to occur via phospholipase cleavage of the GPI anchor, since a transmembrane polypeptide-anchored PrP construct was not shed in response to filipin treatment. Collectively, our data indicate that shedding of PrP(C) can occur via both secretase-like proteolytic cleavage of the protein and phospholipase cleavage of the GPI anchor moiety.
Collapse
Affiliation(s)
- Edward T Parkin
- Proteolysis Research Group, School of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
| | | | | | | |
Collapse
|
42
|
Yao Y, Ren J, Jones IM. Amino terminal interaction in the prion protein identified using fusion to green fluorescent protein. J Neurochem 2003; 87:1057-65. [PMID: 14622086 DOI: 10.1046/j.1471-4159.2003.02039.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In contrast to the well-characterized carboxyl domain, the amino terminal half of the mature cellular prion protein has no defined structure. Here, following fusion of mouse prion protein fragments to green fluorescence protein as a reporter of protein stability, we report extreme variability in fluorescence level that is dependent on the prion fragment expressed. In particular, exposure of the extreme amino terminus in the context of a truncated prion protein molecule led to rapid degradation, whereas the loss of only six amino terminal residues rescued high level fluorescence. Study of the precise endpoints and residue identity associated with high fluorescence suggested a domain within the amino terminal half of the molecule defined by a long-range intramolecular interaction between 23KKRPKP28 and 143DWED146 and dependent upon the anti-parallel beta-sheet ending at residue 169 and normally associated with the structurally defined carboxyl terminal domain. This previously unreported interaction may be significant for understanding prion bioactivity and for structural studies aimed at the complete prion structure.
Collapse
Affiliation(s)
- Yongxiu Yao
- School of Animal and Microbial Sciences, The University of Reading, Reading RG6 6AJ, UK
| | | | | |
Collapse
|
43
|
Walmsley AR, Zeng F, Hooper NM. The N-terminal region of the prion protein ectodomain contains a lipid raft targeting determinant. J Biol Chem 2003; 278:37241-8. [PMID: 12865430 DOI: 10.1074/jbc.m302036200] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The association of the prion protein (PrP) with sphingolipid- and cholesterol-rich lipid rafts is instrumental in the pathogenesis of the neurodegenerative prion diseases. Although the glycosylphosphatidylinositol (GPI) anchor is an exoplasmic determinant of raft association, PrP remained raft-associated in human neuronal cells even when the GPI anchor was deleted or substituted for a transmembrane anchor indicating that the ectodomain contains a raft localization signal. The raft association of transmembrane-anchored PrP occurred independently of Cu(II) binding as it failed to be abolished by either deletion of the octapeptide repeat region (residues 51-90) or treatment of cells with a Cu(II) chelator. Raft association of transmembrane-anchored PrP was only abolished by the deletion of the N-terminal region (residues 23-90) of the ectodomain. This region was sufficient to confer raft localization when fused to the N terminus of a non-raft transmembrane-anchored protein and suppressed the clathrin-coated pit localization signal in the cytoplasmic domain of the amyloid precursor protein. These data indicate that the N-terminal region of PrP acts as a cellular raft targeting determinant and that residues 23-90 of PrP represent the first proteinaceous raft targeting signal within the ectodomain of a GPI-anchored protein.
Collapse
Affiliation(s)
- Adrian R Walmsley
- School of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
| | | | | |
Collapse
|
44
|
Heller U, Winklhofer KF, Heske J, Reintjes A, Tatzelt J. Post-translational import of the prion protein into the endoplasmic reticulum interferes with cell viability: a critical role for the putative transmembrane domain. J Biol Chem 2003; 278:36139-47. [PMID: 12853456 DOI: 10.1074/jbc.m304002200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Aberrant folding of the mammalian prion protein (PrP) is linked to prion diseases in humans and animals. We show that during post-translational targeting of PrP to the endoplasmic reticulum (ER) the putative transmembrane domain induces misfolding of PrP in the cytosol and interferes with its import into the ER. Unglycosylated and misfolded PrP with an uncleaved N-terminal signal sequence associates with ER membranes, and, moreover, decreases cell viability. PrP expressed in the cytosol, lacking the N-terminal ER targeting sequence, also adopts a misfolded conformation; however, this has no adverse effect on cell growth. PrP processing, productive ER import, and cellular viability can be restored either by deleting the putative transmembrane domain or by using a N-terminal signal sequence specific for co-translational ER import. Our study reveals that the putative transmembrane domain features in the formation of misfolded PrP conformers and indicates that post-translational targeting of PrP to the ER can decrease cell viability.
Collapse
Affiliation(s)
- Ulrich Heller
- Department of Cellular Biochemistry, Max Planck Institute for Biochemistry, Am Klopferspitz 18a, D-82152 Martinsried, Germany
| | | | | | | | | |
Collapse
|
45
|
Winklhofer KF, Heske J, Heller U, Reintjes A, Muranyi W, Moarefi I, Tatzelt J. Determinants of the in vivo folding of the prion protein. A bipartite function of helix 1 in folding and aggregation. J Biol Chem 2003; 278:14961-70. [PMID: 12556465 DOI: 10.1074/jbc.m209942200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Misfolding of the mammalian prion protein (PrP) is implicated in the pathogenesis of prion diseases. We analyzed wild type PrP in comparison with different PrP mutants and identified determinants of the in vivo folding pathway of PrP. The complete N terminus of PrP including the putative transmembrane domain and the first beta-strand could be deleted without interfering with PrP maturation. Helix 1, however, turned out to be a major determinant of PrP folding. Disruption of helix 1 prevented attachment of the glycosylphosphatidylinositol (GPI) anchor and the formation of complex N-linked glycans; instead, a high mannose PrP glycoform was secreted into the cell culture supernatant. In the absence of a C-terminal membrane anchor, however, helix 1 induced the formation of unglycosylated and partially protease-resistant PrP aggregates. Moreover, we could show that the C-terminal GPI anchor signal sequence, independent of its role in GPI anchor attachment, mediates core glycosylation of nascent PrP. Interestingly, conversion of high mannose glycans to complex type glycans only occurred when PrP was membrane-anchored. Our study indicates a bipartite function of helix 1 in the maturation and aggregation of PrP and emphasizes a critical role of a membrane anchor in the formation of complex glycosylated PrP.
Collapse
Affiliation(s)
- Konstanze F Winklhofer
- Department of Cellular Biochemistry, Max-Planck-Institut für Biochemie, Am Klopferspitz 18A, D-82152 Martinsried, Germany
| | | | | | | | | | | | | |
Collapse
|
46
|
Walmsley AR, Hooper NM. Distance of sequons to the C-terminus influences the cellular N-glycosylation of the prion protein. Biochem J 2003; 370:351-5. [PMID: 12460122 PMCID: PMC1223167 DOI: 10.1042/bj20021303] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2002] [Revised: 11/29/2002] [Accepted: 12/02/2002] [Indexed: 11/17/2022]
Abstract
Cell-specific differences in the utilization of the two N-glycosylation sequons (Asn180-Ile-Thr and Asn196-Phe-Thr) of the prion protein (PrP) have been proposed to influence the aetiology of the neurodegenerative prion diseases. As the N-glycosylation of PrP is ablated by deletion of the C-terminal glycosyl-phosphatidylinositol (GPI) anchor signal sequence, we have investigated the determinants for PrP sequon utilization in human neuronal cells using the novel approach of restoring N-glycosylation to secreted forms of PrP lacking a GPI anchor. N-glycosylation was restored to an efficiency comparable with that of GPI anchored PrP when the distance of the sequon to the C-terminus was increased so that it was sufficient to reach the active site of oligosaccharyltransferase before chain termination. Our findings indicate that sequon utilization in PrP is a co-translational process that precedes GPI anchor addition and, as such, will be greatly influenced by the dynamics of the translocon-oligosaccharyltransferase complex.
Collapse
Affiliation(s)
- Adrian R Walmsley
- School of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT, U.K
| | | |
Collapse
|
47
|
Nunziante M, Gilch S, Schätzl HM. Essential role of the prion protein N terminus in subcellular trafficking and half-life of cellular prion protein. J Biol Chem 2003; 278:3726-34. [PMID: 12431994 DOI: 10.1074/jbc.m206313200] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Aberrant metabolism and conformational alterations of the cellular prion protein (PrP(c)) are the underlying causes of transmissible spongiform encephalopathies in humans and animals. In cells, PrP(c) is modified post-translationally and transported along the secretory pathway to the plasma membrane, where it is attached to the cell surface by a glycosylphosphatidylinositol anchor. In surface biotinylation assays we observed that deletions within the unstructured N terminus of murine PrP(c) led to a significant reduction of internalization of PrP after transfection of murine neuroblastoma cells. Truncation of the entire N terminus most significantly inhibited internalization of PrP(c). The same deletions caused a significant prolongation of cellular half-life of PrP(c) and a delay in the transport through the secretory pathway to the cell surface. There was no difference in the glycosylation kinetics, indicating that all PrP constructs equally passed endoplasmic reticulum-based cellular quality control. Addition of the N terminus of the Xenopus laevis PrP, which does not encode a copper-binding repeat element, to N-terminally truncated mouse PrP restored the wild type phenotype. These results provide deeper insight into the life cycle of the PrP(c), raising the novel possibility of a targeting function of its N-proximal part by interacting with the secretory and the endocytic machinery. They also indicate the conservation of this targeting property in evolution.
Collapse
Affiliation(s)
- Max Nunziante
- Gene Center Munich, Max von Pettenkofer Institute for Virology, Faculty of Medicine, Ludwig-Maximilians-University, Feodor-Lynen-Strasse 25, D-81377 Munich, Germany
| | | | | |
Collapse
|
48
|
Zeng F, Watt NT, Walmsley AR, Hooper NM. Tethering the N-terminus of the prion protein compromises the cellular response to oxidative stress. J Neurochem 2003; 84:480-90. [PMID: 12558968 DOI: 10.1046/j.1471-4159.2003.01529.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The role of the N-terminal half of the prion protein (PrPC) in normal cellular function and pathology remains enigmatic. To investigate the biological role of the N-terminus of PrP, we examined the cellular properties of a construct of murine PrP, PrP-DA, in which the N-terminus is tethered to the membrane by an uncleaved signal peptide and which retains the glycosyl-phosphatidylinositol anchor. Human neuroblastoma SH-SY5Y cells expressing PrP-DA were more susceptible to hydrogen peroxide and copper induced toxicity than wtPrP expressing cells. The PrP-DA expressing cells had an increased level of intracellular free radicals and reduced levels of superoxide dismutase and glutathione peroxidase as compared to the wtPrP expressing cells. The membrane topology, cell surface location, lipid raft localisation, intracellular trafficking and copper-mediated endocytosis of PrP-DA were not significantly different from wtPrP. However, cells expressing PrP-DA accumulated an N-terminal fragment that was resistant to proteinase K. The data presented here are consistent with the N-terminal region of PrPC having a role in the cellular response to oxidative stress, and that tethering this region of the protein to the membrane compromises this function through the accumulation of a protease-resistant N-terminal fragment, similar to that seen in some forms of human prion disease.
Collapse
Affiliation(s)
- Fanning Zeng
- School of Biochemistry and Molecular Biology, University of Leeds, Leeds, UK
| | | | | | | |
Collapse
|
49
|
Gu Y, Verghese S, Mishra RS, Xu X, Shi Y, Singh N. Mutant prion protein-mediated aggregation of normal prion protein in the endoplasmic reticulum: implications for prion propagation and neurotoxicity. J Neurochem 2003; 84:10-22. [PMID: 12485397 DOI: 10.1046/j.1471-4159.2003.01255.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Familial prion disorders are believed to result from spontaneous conversion of mutant prion protein (PrPM) to the pathogenic isoform (PrPSc). While most familial cases are heterozygous and thus express the normal (PrPC) and mutant alleles of PrP, the role of PrPC in the pathogenic process is unclear. Plaques from affected cases reveal a heterogeneous picture; in some cases only PrPM is detected, whereas in others both PrPC and PrPM are transformed to PrPSc. To understand if the coaggregation of PrPC is governed by PrP mutations or is a consequence of the cellular compartment of PrPM aggregation, we coexpressed PrPM and PrPC in neuroblastoma cells, the latter tagged with green fluorescent protein (PrPC-GFP) for differentiation. Two PrPM forms (PrP231T, PrP217R/231T) that aggregate spontaneously in the endoplasmic reticulum (ER) were generated for this analysis. We report that PrPC-GFP aggregates when coexpressed with PrP231T or PrP217R/231T, regardless of sequence homology between the interacting forms. Furthermore, intracellular aggregates of PrP231T induce the accumulation of a C-terminal fragment of PrP, most likely derived from a potentially neurotoxic transmembrane form of PrP (CtmPrP) in the ER. These findings have implications for prion pathogenesis in familial prion disorders, especially in cases where transport of PrPM from the ER is blocked by the cellular quality control.
Collapse
Affiliation(s)
- Yaping Gu
- Institute of Pathology, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | | | | | | | | | | |
Collapse
|
50
|
Jakeman DL, Withers SG. On expanding the repertoire of glycosynthases: Mutant β-galactosidases forming β-(1,6)-linkages. CAN J CHEM 2002. [DOI: 10.1139/v02-077] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Oligosaccharide synthesis by enzymatic processes offers the potential for thrusting oligosaccharides to the forefront of pharmaceutical research, in part, due to expedient and scalable reaction protocols. Glycosynthases are an emerging class of mutant enzymes capable of synthesizing glycosidic linkages in high yield. We report a new glycosynthase enzyme generated by a point mutation of E. coli β-galactosidase that condenses α-galactosyl fluoride with aryl glucosides forming a β-(1,6) glycosidic linkage. A further point mutation within the enzyme, proximal to the active site, increases the yields significantly.Key words: glycosyl transfer, glycosynthase, enzymatic oligosaccharide synthesis. tétrahydrooxazine, isofagomine, iminosucres, inhibiteurs de glycosidases.[Traduit par la Rédaction]
Collapse
|