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Yagita K, Noguchi H, Koyama S, Hamasaki H, Komori T, Aishima S, Kosaka T, Ueda M, Komohara Y, Watanabe A, Sasagasako N, Ninomiya T, Oda Y, Honda H. Chronological Changes in the Expression Pattern of Hippocampal Prion Proteins During Disease Progression in Sporadic Creutzfeldt-Jakob Disease MM1 Subtype. J Neuropathol Exp Neurol 2022; 81:900-909. [PMID: 36063412 DOI: 10.1093/jnen/nlac078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The differential effects of sporadic Creutzfeldt-Jakob disease (sCJD) on the hippocampus and other neocortical areas are poorly understood. We aimed to reveal the histological patterns of cellular prion protein (PrPC) and abnormal prion protein (PrPSc) in hippocampi of sCJD patients and normal controls (NCs). Our study examined 18 postmortem sCJD patients (MM1, 14 cases; MM1 + 2c, 3 cases; MM1 + 2t, 1 case) and 12 NCs. Immunohistochemistry was conducted using 4 primary antibodies, of which 3 targeted the N-terminus of the prion protein (PrP), and 1 (EP1802Y) targeted the C-terminal domain. PrPC expression was abundant in the hippocampus of NCs, and the distribution of PrPC at CA3/4 was reminiscent of synaptic complexes. In sCJD cases with a disease history of <2 years, antibodies against the N-terminus could not detect synapse-like PrP expression at CA4; however, EP1802Y could characterize the synapse-like expression. PrPSc accumulation and spongiform changes became evident after 2 years of illness, when PrPSc deposits were more noticeably detected by N-terminal-specific antibodies. Our findings highlighted the chronology of histopathological alterations in the CA4 region in sCJD patients.
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Affiliation(s)
- Kaoru Yagita
- Department of Neuropathology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Hideko Noguchi
- Department of Neuropathology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Sachiko Koyama
- Department of Neuropathology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Hideomi Hamasaki
- Department of Neuropathology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Takashi Komori
- Department of Laboratory Medicine and Pathology, Tokyo Metropolitan Neurological Hospital, Tokyo, Japan
| | - Shinichi Aishima
- Department of Pathology and Microbiology, Faculty of Medicine, University of Saga, Saga, Japan
| | - Takayuki Kosaka
- Department of Neurology, National Hospital Organization Kumamoto Medical Center, Kumamoto, Japan
| | - Mitsuharu Ueda
- Department of Neurology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan
| | - Yoshihiro Komohara
- Department of Cell Pathology, Graduate School of Medical Sciences, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Akihiro Watanabe
- Department of Neurology, Neuro-Muscular Center, National Omuta Hospital, Omuta, Japan
| | - Naokazu Sasagasako
- Department of Neurology, Neuro-Muscular Center, National Omuta Hospital, Omuta, Japan
| | - Toshiharu Ninomiya
- Department of Epidemiology and Public Health, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.,Department of Center for Cohort Studies, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Yoshinao Oda
- Department of Anatomic Pathology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Hiroyuki Honda
- Department of Neuropathology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
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Volatile Anesthetic Sevoflurane Precursor 1,1,1,3,3,3-Hexafluoro-2-Propanol (HFIP) Exerts an Anti-Prion Activity in Prion-Infected Culture Cells. Neurochem Res 2021; 46:2056-2065. [PMID: 34043140 PMCID: PMC8254714 DOI: 10.1007/s11064-021-03344-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 04/20/2021] [Accepted: 05/12/2021] [Indexed: 12/22/2022]
Abstract
Prion disease is a neurodegenerative disorder with progressive neurologic symptoms and accelerated cognitive decline. The causative protein of prion disease is the prion protein (PrP), and structural transition of PrP from the normal helix rich form (PrPC) to the abnormal β-sheet rich form (PrPSc) occurs in prion disease. While so far numerous therapeutic agents for prion diseases have been developed, none of them are still useful. A fluorinated alcohol, hexafluoro isopropanol (HFIP), is a precursor to the inhalational anesthetic sevoflurane and its metabolites. HFIP is also known as a robust α-helix inducer and is widely used as a solvent for highly aggregated peptides. Here we show that the α-helix-inducing activity of HFIP caused the conformational transformation of the fibrous structure of PrP into amorphous aggregates in vitro. HFIP added to the ScN2a cell medium, which continuously expresses PrPSc, reduced PrPSc protease resistance after 24-h incubation. It was also clarified that ScN2a cells are more susceptible to HFIP than any of the cells being compared. Based on these findings, HFIP is expected to develop as a therapeutic agent for prion disease.
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Cellular Prion Protein (PrPc): Putative Interacting Partners and Consequences of the Interaction. Int J Mol Sci 2020; 21:ijms21197058. [PMID: 32992764 PMCID: PMC7583789 DOI: 10.3390/ijms21197058] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 09/20/2020] [Accepted: 09/23/2020] [Indexed: 02/08/2023] Open
Abstract
Cellular prion protein (PrPc) is a small glycosylphosphatidylinositol (GPI) anchored protein most abundantly found in the outer leaflet of the plasma membrane (PM) in the central nervous system (CNS). PrPc misfolding causes neurodegenerative prion diseases in the CNS. PrPc interacts with a wide range of protein partners because of the intrinsically disordered nature of the protein’s N-terminus. Numerous studies have attempted to decipher the physiological role of the prion protein by searching for proteins which interact with PrPc. Biochemical characteristics and biological functions both appear to be affected by interacting protein partners. The key challenge in identifying a potential interacting partner is to demonstrate that binding to a specific ligand is necessary for cellular physiological function or malfunction. In this review, we have summarized the intracellular and extracellular interacting partners of PrPc and potential consequences of their binding. We also briefly describe prion disease-related mutations at the end of this review.
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Shimizu T, Kozuka Y, Kusano M, Nagane M, Yamashita T, Hachiya N. PrP (122-139) is a covert mitochondrial targeting signal of prion protein and it specifically triggers the perinuclear clustering of mitochondria in neuronal culture cells. Biochem Biophys Res Commun 2020; 524:301-307. [PMID: 31987501 DOI: 10.1016/j.bbrc.2020.01.099] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Accepted: 01/17/2020] [Indexed: 12/12/2022]
Abstract
In many neurodegenerative diseases, mitochondria are actively involved in the onset and/or progression of diseases because the energy depletion of the neuronal cells directly leads to the dysfunction and degeneration of cells. In the case of prion diseases, mitochondrial involvement has been reported recently and evidence that prion protein (PrP) is localized in mitochondria is increasing. Despite these findings, the precise molecular mechanism by which PrP targets mitochondria remains unclear. PrP is a secretory protein and does not have a pre-sequence that targets the mitochondria, therefore, we thought that there was a covert signal in the amino acid sequence of PrP. To find the sequence, we constructed various GFP-fused PrP-truncations and colocalization with mitochondria was verified by live-cell imaging. Consequently, we found that 18 amino acids, PrP (122-139), are indispensable for the mitochondrial targeting of PrP. In addition, fluorescent microscopy observation revealed that PrP-localized mitochondria were accumulated at the perinuclear region in neuronal cells such as mouse neuroblastoma Neuro2a (N2a) and prion persistent infection N2a strain (ScN2a), anterograde movement of the mitochondria toward the cell membrane was completely inhibited because of the stacking of PrP on the outer membrane. The cristae formation of perinuclear accumulated mitochondria was disappeared indicating the reduced mitochondrial activity. Surprisingly, PrP-dependent mitochondrial perinuclear accumulation was specifically occurred on neuronal cells, whereas in epithelial HeLa cells and fibroblast COS-7 cells, no perinuclear accumulation observed even after the mitochondrial targeting of PrP.
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Affiliation(s)
- Takuto Shimizu
- Laboratory of Biochemistry, School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamiharas-shi, Kanagawa, 252-5201, Japan; Tokyo Metropolitan Industrial Technology Research Institute, 2-4-10 Aomi, Koto-ku, Tokyo, 135-0064, Japan
| | - Yoshimichi Kozuka
- Shinku Device, Co. Ltd., 1285-5 Iijima-Cho, Mito, Ibaraki, 311-4155, Japan
| | - Mayumi Kusano
- Joyful Life, Inc., 4-5 Kojimachi, Chiyoda-ku, Tokyo, 102-0083, Japan
| | - Masaki Nagane
- Laboratory of Biochemistry, School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamiharas-shi, Kanagawa, 252-5201, Japan
| | - Tadashi Yamashita
- Laboratory of Biochemistry, School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamiharas-shi, Kanagawa, 252-5201, Japan
| | - Naomi Hachiya
- Tokyo Metropolitan Industrial Technology Research Institute, 2-4-10 Aomi, Koto-ku, Tokyo, 135-0064, Japan.
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Iwamaru Y, Kitani H, Okada H, Takenouchi T, Shimizu Y, Imamura M, Miyazawa K, Murayama Y, Hoover EA, Yokoyama T. Proximity of SCG10 and prion protein in membrane rafts. J Neurochem 2015; 136:1204-1218. [PMID: 26663033 DOI: 10.1111/jnc.13488] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 11/23/2015] [Accepted: 11/24/2015] [Indexed: 12/14/2022]
Abstract
The conversion of normal cellular prion protein (PrPC) into its pathogenic isoform (PrPSc) is an essential event in prion pathogenesis. In culture models, membrane rafts are suggested to play a critical role in PrPSc formation. To identify the candidate molecules capable of interacting with PrPC and facilitating PrPSc formation in membrane rafts, we applied a novel biochemical labeling method termed enzyme-mediated activation of radical sources. Enzyme-mediated activation of radical sources was applied to the Lubrol WX insoluble detergent-resistant membrane fractions from mouse neuroblastoma (N2a) cells in which the surface PrPC was labeled with HRP-conjugated anti-PrP antibody. Two-dimensional western blots of these preparations revealed biotinylated spots of approximately 20 kDa with an isoelectric point of 8.0-9.0. Liquid chromatography-tandem mass spectrometry analysis resulted in the identification of peptides containing SCG10, the neuron-specific microtubule regulator. Proximity of SCG10 and PrPC was confirmed using proximity ligation assay and co-immunoprecipitation assay. Transfection of persistently 22L prion-infected N2a cells with SCG10 small interfering RNA reduced SCG10 expression, but did not prevent PrPSc accumulation, indicating that SCG10 appears to be unrelated to PrPSc formation of 22L prion. Immunofluorescence and western blot analyses showed reduced levels of SCG10 in the hippocampus of prion-infected mice, suggesting a possible association between SCG10 levels and the prion neuropathogenesis. By applying a novel biochemical labeling method against detergent-resistant membrane fractions from mouse neuroblastoma cells, the neuron-specific microtubule-destabilization protein, SCG10 was identified as a novel candidate that is proximate to normal prion protein (PrP) in membrane rafts. SCG10 seemed unrelated to disease-related PrP formation under certain conditions, while there is a possible association between SCG10 levels and prion neuropathogenesis. Cover Image for this issue: doi: 10.1111/jnc.13310.
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Affiliation(s)
- Yoshifumi Iwamaru
- Influenza and Prion Disease Research Center, National Institute of Animal Health, Tsukuba, Ibaraki, Japan.,Prion Research Center, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, USA
| | - Hiroshi Kitani
- Animal Immune and Cell Biology Research Unit, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan
| | - Hiroyuki Okada
- Influenza and Prion Disease Research Center, National Institute of Animal Health, Tsukuba, Ibaraki, Japan
| | - Takato Takenouchi
- Animal Immune and Cell Biology Research Unit, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan
| | - Yoshihisa Shimizu
- Influenza and Prion Disease Research Center, National Institute of Animal Health, Tsukuba, Ibaraki, Japan
| | - Morikazu Imamura
- Influenza and Prion Disease Research Center, National Institute of Animal Health, Tsukuba, Ibaraki, Japan
| | - Kohtaro Miyazawa
- Influenza and Prion Disease Research Center, National Institute of Animal Health, Tsukuba, Ibaraki, Japan
| | - Yuichi Murayama
- Influenza and Prion Disease Research Center, National Institute of Animal Health, Tsukuba, Ibaraki, Japan
| | - Edward A Hoover
- Prion Research Center, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, USA
| | - Takashi Yokoyama
- Influenza and Prion Disease Research Center, National Institute of Animal Health, Tsukuba, Ibaraki, Japan
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Bravard A, Auvré F, Fantini D, Bernardino-Sgherri J, Sissoëff L, Daynac M, Xu Z, Etienne O, Dehen C, Comoy E, Boussin FD, Tell G, Deslys JP, Radicella JP. The prion protein is critical for DNA repair and cell survival after genotoxic stress. Nucleic Acids Res 2014; 43:904-16. [PMID: 25539913 PMCID: PMC4333392 DOI: 10.1093/nar/gku1342] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The prion protein (PrP) is highly conserved and ubiquitously expressed, suggesting that it plays an important physiological function. However, despite decades of investigation, this role remains elusive. Here, by using animal and cellular models, we unveil a key role of PrP in the DNA damage response. Exposure of neurons to a genotoxic stress activates PRNP transcription leading to an increased amount of PrP in the nucleus where it interacts with APE1, the major mammalian endonuclease essential for base excision repair, and stimulates its activity. Preventing the induction of PRNP results in accumulation of abasic sites in DNA and impairs cell survival after genotoxic treatment. Brains from Prnp−/− mice display a reduced APE1 activity and a defect in the repair of induced DNA damage in vivo. Thus, PrP is required to maintain genomic stability in response to genotoxic stresses.
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Affiliation(s)
- Anne Bravard
- CEA, Institute of Cellular and Molecular Radiobiology, F-92265 Fontenay-aux-Roses, France INSERM, U967, F-92265 Fontenay-aux-Roses, France Université Paris Diderot, UMR 967, F-92265 Fontenay-aux-Roses, France Université Paris Sud, UMR 967, F-92265 Fontenay-aux-Roses, France
| | - Frédéric Auvré
- CEA, Institute of Cellular and Molecular Radiobiology, F-92265 Fontenay-aux-Roses, France INSERM, U967, F-92265 Fontenay-aux-Roses, France Université Paris Diderot, UMR 967, F-92265 Fontenay-aux-Roses, France Université Paris Sud, UMR 967, F-92265 Fontenay-aux-Roses, France
| | - Damiano Fantini
- CEA, Institute of Cellular and Molecular Radiobiology, F-92265 Fontenay-aux-Roses, France INSERM, U967, F-92265 Fontenay-aux-Roses, France Université Paris Diderot, UMR 967, F-92265 Fontenay-aux-Roses, France Université Paris Sud, UMR 967, F-92265 Fontenay-aux-Roses, France
| | - Jacqueline Bernardino-Sgherri
- CEA, Institute of Cellular and Molecular Radiobiology, F-92265 Fontenay-aux-Roses, France INSERM, U967, F-92265 Fontenay-aux-Roses, France Université Paris Diderot, UMR 967, F-92265 Fontenay-aux-Roses, France Université Paris Sud, UMR 967, F-92265 Fontenay-aux-Roses, France
| | - Ludmilla Sissoëff
- CEA, Institut des Maladies Emergentes et des Thérapies Innovantes, Service d'Etudes des Prions et des Infections Atypiques, F-92265 Fontenay-aux-roses, France
| | - Mathieu Daynac
- CEA, Institute of Cellular and Molecular Radiobiology, F-92265 Fontenay-aux-Roses, France INSERM, U967, F-92265 Fontenay-aux-Roses, France Université Paris Diderot, UMR 967, F-92265 Fontenay-aux-Roses, France Université Paris Sud, UMR 967, F-92265 Fontenay-aux-Roses, France
| | - Zhou Xu
- CEA, Institut des Maladies Emergentes et des Thérapies Innovantes, Service d'Etudes des Prions et des Infections Atypiques, F-92265 Fontenay-aux-roses, France
| | - Olivier Etienne
- CEA, Institute of Cellular and Molecular Radiobiology, F-92265 Fontenay-aux-Roses, France INSERM, U967, F-92265 Fontenay-aux-Roses, France Université Paris Diderot, UMR 967, F-92265 Fontenay-aux-Roses, France Université Paris Sud, UMR 967, F-92265 Fontenay-aux-Roses, France
| | - Capucine Dehen
- CEA, Institut des Maladies Emergentes et des Thérapies Innovantes, Service d'Etudes des Prions et des Infections Atypiques, F-92265 Fontenay-aux-roses, France
| | - Emmanuel Comoy
- CEA, Institut des Maladies Emergentes et des Thérapies Innovantes, Service d'Etudes des Prions et des Infections Atypiques, F-92265 Fontenay-aux-roses, France
| | - François D Boussin
- CEA, Institute of Cellular and Molecular Radiobiology, F-92265 Fontenay-aux-Roses, France INSERM, U967, F-92265 Fontenay-aux-Roses, France Université Paris Diderot, UMR 967, F-92265 Fontenay-aux-Roses, France Université Paris Sud, UMR 967, F-92265 Fontenay-aux-Roses, France
| | - Gianluca Tell
- Department of Medical and Biological Sciences, University of Udine, I-33100 Udine, Italy
| | - Jean-Philippe Deslys
- CEA, Institut des Maladies Emergentes et des Thérapies Innovantes, Service d'Etudes des Prions et des Infections Atypiques, F-92265 Fontenay-aux-roses, France
| | - J Pablo Radicella
- CEA, Institute of Cellular and Molecular Radiobiology, F-92265 Fontenay-aux-Roses, France INSERM, U967, F-92265 Fontenay-aux-Roses, France Université Paris Diderot, UMR 967, F-92265 Fontenay-aux-Roses, France Université Paris Sud, UMR 967, F-92265 Fontenay-aux-Roses, France
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Campisi E, Cardone F, Graziano S, Galeno R, Pocchiari M. Role of proteomics in understanding prion infection. Expert Rev Proteomics 2013; 9:649-66. [PMID: 23256675 DOI: 10.1586/epr.12.58] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Transmissible spongiform encephalopathies or prion diseases are fatal neurodegenerative pathologies characterized by the autocatalytic misfolding and polymerization of a cellular glycoprotein (cellular prion protein [PrP(C)]) that accumulates in the CNS and leads to neurodegeneration. The detailed mechanics of PrP(C) conversion to its pathological isoform (PrP(TSE)) are unclear but one or more exogenous factors are likely involved in the process of PrP misfolding. In the last 20 years, proteomic investigations have identified several endogenous proteins that interact with PrP(C), PrP(TSE) or both, which are possibly involved in the prion pathogenetic process. However, current approaches have not yet produced convincing conclusions on the biological value of such PrP interactors. Future advancements in the comprehension of the molecular pathogenesis of prion diseases, in experimental techniques and in data analysis procedures, together with a boost in more productive international collaborations, are therefore needed to improve the understanding on the role of PrP interactors. Finally, the advancement of 'omics' techniques in prion diseases will contribute to the development of novel diagnostic tests and effective drugs.
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Affiliation(s)
- Edmondo Campisi
- Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161, Rome, Italy
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Last V, Williams A, Werling D. Inhibition of cytosolic Phospholipase A2 prevents prion peptide-induced neuronal damage and co-localisation with Beta III Tubulin. BMC Neurosci 2012; 13:106. [PMID: 22928663 PMCID: PMC3496594 DOI: 10.1186/1471-2202-13-106] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Accepted: 08/21/2012] [Indexed: 11/10/2022] Open
Abstract
Background Activation of phospholipase A2 (PLA2) and the subsequent metabolism of arachidonic acid (AA) to prostaglandins have been shown to play an important role in neuronal death in neurodegenerative disease. Here we report the effects of the prion peptide fragment HuPrP106-126 on the PLA2 cascade in primary cortical neurons and translocation of cPLA2 to neurites. Results Exposure of primary cortical neurons to HuPrP106-126 increased the levels of phosphorylated cPLA2 and caused phosphorylated cPLA2 to relocate from the cell body to the cellular neurite in a PrP-dependent manner, a previously unreported observation. HuPrP106-126 also induced significant AA release, an indicator of cPLA2 activation; this preceded synapse damage and subsequent cellular death. The novel translocation of p-cPLA2 postulated the potential for exposure to HuPrP106-126 to result in a re-arrangement of the cellular cytoskeleton. However p-cPLA2 did not colocalise significantly with F-actin, intermediate filaments, or microtubule-associated proteins. Conversely, p-cPLA2 did significantly colocalise with the cytoskeletal protein beta III tubulin. Pre-treatment with the PLA2 inhibitor, palmitoyl trifluoromethyl ketone (PACOCF3) reduced cPLA2 activation, AA release and damage to the neuronal synapse. Furthermore, PACOCF3 reduced expression of p-cPLA2 in neurites and inhibited colocalisation with beta III tubulin, resulting in protection against PrP-induced cell death. Conclusions Collectively, these findings suggest that cPLA2 plays a vital role in the action of HuPrP106-126 and that the colocalisation of p-cPLA2 with beta III tubulin could be central to the progress of neurodegeneration caused by prion peptides. Further work is needed to define exactly how PLA2 inhibitors protect neurons from peptide-induced toxicity and how this relates to intracellular structural changes occurring in neurodegeneration.
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Affiliation(s)
- Victoria Last
- Department of Pathology and Infectious Diseases, Royal Veterinary College, Hawkshead Lane, North Mymms, Hertfordshire AL9 7TA, UK.
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Nieznanska H, Dudek E, Zajkowski T, Szczesna E, Kasprzak AA, Nieznanski K. Prion protein impairs kinesin-driven transport. Biochem Biophys Res Commun 2012; 425:788-93. [PMID: 22885185 DOI: 10.1016/j.bbrc.2012.07.153] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Accepted: 07/27/2012] [Indexed: 01/11/2023]
Abstract
Our previous studies have demonstrated that prion protein (PrP) leads to disassembly of microtubular cytoskeleton through binding to tubulin and its oligomerization. Here we found that PrP-treated cells exhibited improper morphology of mitotic spindles. Formation of aberrant spindles may result not only from altered microtubule dynamics - as expected from PrP-induced tubulin oligomerization - but also from impairing the function of molecular motors. Therefore we checked whether binding of PrP to microtubules affected movement generated by Ncd - a kinesin responsible for the proper organization of division spindles. We found that PrP inhibited Ncd-driven transport of microtubules. Most probably, the inhibition of the microtubule movement resulted from PrP-induced changes in the microtubule structure since Ncd-microtubule binding was reduced already at low PrP to tubulin molar ratios. This study suggests another plausible mechanism of PrP cytotoxicity related to the interaction with tubulin, namely impeding microtubule-dependent transport.
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Affiliation(s)
- Hanna Nieznanska
- Department of Biochemistry, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland
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Abstract
Transgenic mice expressing prion protein (PrP) molecules with several different internal deletions display spontaneous neurodegenerative phenotypes that can be dose-dependently suppressed by coexpression of wild-type PrP. Each of these deletions, including the largest one (Δ32-134), retains 9 aa immediately following the signal peptide cleavage site (residues 23-31; KKRPKPGGW). These residues have been implicated in several biological functions of PrP, including endocytic trafficking and binding of glycosaminoglycans. We report here on our experiments to test the role of this domain in the toxicity of deleted forms of PrP. We find that transgenic mice expressing Δ23-134 PrP display no clinical symptoms or neuropathology, in contrast to mice expressing Δ32-134 PrP, suggesting that residues 23-31 are essential for the toxic phenotype. Using a newly developed cell culture assay, we narrow the essential region to amino acids 23-26, and we show that mutant PrP toxicity is not related to the role of the N-terminal residues in endocytosis or binding to endogenous glycosaminoglycans. However, we find that mutant PrP toxicity is potently inhibited by application of exogenous glycosaminoglycans, suggesting that the latter molecules block an essential interaction between the N terminus of PrP and a membrane-associated target site. Our results demonstrate that a short segment containing positively charged amino acids at the N terminus of PrP plays an essential role in mediating PrP-related neurotoxicity. This finding identifies a protein domain that may serve as a drug target for amelioration of prion neurotoxicity.
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Possible involvement of calpain-like activity in normal processing of cellular prion protein. Neurosci Lett 2010; 490:150-5. [PMID: 21193014 DOI: 10.1016/j.neulet.2010.12.046] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2010] [Revised: 12/17/2010] [Accepted: 12/19/2010] [Indexed: 11/21/2022]
Abstract
Time-lapse imaging analysis was previously used to show that spontaneous proteolysis of PrP(C), which is fluorescence-labeled at both NH(2)- and COOH-termini, occurred in mouse neuroblastoma neuro2a (N2a) cells susceptible to PrP(Sc). We demonstrated that, unlike other protease inhibitors, a calpain inhibitor, calpastatin, drastically inhibited endoproteolysis of PrP(C), as observed with time-lapse imaging in living cells, suggesting calpain-like activity. Calpastatin also inhibited cleavage of endogenous PrP(C), and unprocessed molecules and the double-labeled PrP(C) accumulated around the perinuclear region. The molecular weight of PrP(C) fragments generated by spontaneous proteolysis was identical to those produced when PrP(C) synthesized in vitro was exposed to exogenous calpain. These results suggest that a calpain-like activity mediates normal processing of PrP(C) in N2a cells.
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Migration-associated secretion of melanoma inhibitory activity at the cell rear is supported by KCa3.1 potassium channels. Cell Res 2010; 20:1224-38. [DOI: 10.1038/cr.2010.121] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
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Nieznanski K. Interactions of prion protein with intracellular proteins: so many partners and no consequences? Cell Mol Neurobiol 2009; 30:653-66. [PMID: 20041289 DOI: 10.1007/s10571-009-9491-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Accepted: 12/18/2009] [Indexed: 10/20/2022]
Abstract
Prion protein (PrP) plays a key role in the pathogenesis of transmissible spongiform encephalopathies (TSEs)--fatal diseases of the central nervous system. Its physiological function as well as exact role in neurodegeneration remain unclear, hence screens for proteins interacting with PrP seem to be the most promising approach to elucidating these issues. PrP is mostly a plasma membrane-anchored extracellular glycoprotein and only a small fraction resides inside the cell, yet the number of identified intracellular partners of PrP is comparable to that of its membranal or extracellular interactors. Since some TSEs are accompanied by significantly increased levels of cytoplasmic PrP and this fraction of the protein has been found to be neurotoxic, it is of particular interest to characterize the intracellular interactome of PrP. It seems reasonable that at elevated cytoplasmic levels, PrP may exert cytotoxic effect by affecting the physiological functions of its intracellular interactors. This review is focused on the cytoplasmic partners of PrP along with possible consequences of their binding.
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Affiliation(s)
- Krzysztof Nieznanski
- Department of Biochemistry, Polish Academy of Sciences, Nencki Institute of Experimental Biology, 3 Pasteur St, Warsaw 02093, Poland.
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14
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Osiecka KM, Nieznanska H, Skowronek KJ, Karolczak J, Schneider G, Nieznanski K. Prion protein region 23-32 interacts with tubulin and inhibits microtubule assembly. Proteins 2009; 77:279-96. [PMID: 19422054 DOI: 10.1002/prot.22435] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In previous studies we have demonstrated that prion protein (PrP) binds directly to tubulin and this interaction leads to the inhibition of microtubule formation by inducement of tubulin oligomerization. This report is aimed at mapping the regions of PrP and tubulin involved in the interaction and identification of PrP domains responsible for tubulin oligomerization. Preliminary studies focused our attention to the N-terminal flexible part of PrP encompassing residues 23-110. Using a panel of deletion mutants of PrP, we identified two microtubule-binding motifs at both ends of this part of the molecule. We found that residues 23-32 constitute a major site of interaction, whereas residues 101-110 represent a weak binding site. The crucial role of the 23-32 sequence in the interaction with tubulin was confirmed employing chymotryptic fragments of PrP. Surprisingly, the octarepeat region linking the above motifs plays only a supporting role in the interaction. The binding of Cu(2+) to PrP did not affect the interaction. We also demonstrate that PrP deletion mutants lacking residues 23-32 exhibit very low efficiency in the inducement of tubulin oligomerization. Moreover, a synthetic peptide corresponding to this sequence, but not that identical with fragment 101-110, mimics the effects of the full-length protein on tubulin oligomerization and microtubule assembly. At the cellular level, peptide composed of the PrP motive 23-30 and signal sequence (1-22) disrupted the microtubular cytoskeleton. Using tryptic and chymotryptic fragments of alpha- and beta-tubulin, we mapped the docking sites for PrP within the C-terminal domains constituting the outer surface of microtubule.
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Affiliation(s)
- Katarzyna M Osiecka
- Department of Biochemistry, Nencki Institute of Experimental Biology, Warsaw, Poland
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15
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Conformational detection of prion protein with biarsenical labeling and FlAsH fluorescence. Biochem Biophys Res Commun 2009; 380:564-8. [PMID: 19285001 DOI: 10.1016/j.bbrc.2009.01.120] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Accepted: 01/22/2009] [Indexed: 11/20/2022]
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16
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The polybasic N-terminal region of the prion protein controls the physical properties of both the cellular and fibrillar forms of PrP. J Mol Biol 2008; 383:1210-24. [PMID: 18789949 DOI: 10.1016/j.jmb.2008.08.073] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2008] [Revised: 07/23/2008] [Accepted: 08/25/2008] [Indexed: 01/07/2023]
Abstract
Individual variations in structure and morphology of amyloid fibrils produced from a single polypeptide are likely to underlie the molecular origin of prion strains and control the efficiency of the species barrier in the transmission of prions. Previously, we observed that the shape of amyloid fibrils produced from full-length prion protein (PrP 23-231) varied substantially for different batches of purified recombinant PrP. Variations in fibril morphology were also observed for different fractions that corresponded to the highly pure PrP peak collected at the last step of purification. A series of biochemical experiments revealed that the variation in fibril morphology was attributable to the presence of miniscule amounts of N-terminally truncated PrPs, where a PrP encompassing residue 31-231 was the most abundant of the truncated polypeptides. Subsequent experiments showed that the presence of small amounts of recombinant PrP 31-231 (0.1-1%) in mixtures with full-length PrP 23-231 had a dramatic impact on fibril morphology and conformation. Furthermore, the deletion of the short polybasic N-terminal region 23-30 was found to reduce the folding efficiency to the native alpha-helical forms and the conformational stability of alpha-PrP. These findings are very surprising considering that residues 23-30 are very distant from the C-terminal globular folded domain in alpha-PrP and from the prion folding domain in the fibrillar form. However, our studies suggest that the N-terminal polybasic region 23-30 is essential for effective folding of PrP to its native cellular conformation. This work also suggests that this region could regulate diversity of prion strains or subtypes despite its remote location from the prion folding domain.
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17
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Nikles D, Vana K, Gauczynski S, Knetsch H, Ludewigs H, Weiss S. Subcellular localization of prion proteins and the 37 kDa/67 kDa laminin receptor fused to fluorescent proteins. Biochim Biophys Acta Mol Basis Dis 2008; 1782:335-40. [PMID: 18339329 DOI: 10.1016/j.bbadis.2008.02.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Revised: 02/12/2008] [Accepted: 02/12/2008] [Indexed: 11/16/2022]
Abstract
The 37 kDa/67 kDa laminin receptor LRP/LR acts as a receptor for both PrPc and PrPSc at the cell surface. Here, we further analyzed the subcellular localization of fluorescent labeled prion protein (PrP) and laminin receptor (LRP/LR) molecules. We show that EGFP-PrP is localized at the cell surface and in a perinuclear compartment, respectively. In contrast, a DsRed-DeltaSP-PrP mutant lacking the signal peptide is almost exclusively found in the nucleus but does not colocalize with heterochromatin. Interestingly, LRP-DsRed efficiently colocalizes with EGFP-PrP in the perinuclear compartment and LRP-ECFP partly colocalizes with DsRed-DeltaSP-PrP in the nucleus, respectively. We conclude that the interactions of PrP and LRP/LR are not restricted to the cell surface but occur also in intracellular compartments suggesting a putative role of LRP/LR in the trafficking of PrP molecules.
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Affiliation(s)
- Daphne Nikles
- Laboratorium für Molekulare Biologie - Genzentrum-Institut für Biochemie der LMU München, Feodor-Lynen-Str. 25, 81377 München, Germany
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18
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Dong CF, Shi S, Wang XF, An R, Li P, Chen JM, Wang X, Wang GR, Shan B, Zhang BY, Han J, Dong XP. The N-terminus of PrP is responsible for interacting with tubulin and fCJD related PrP mutants possess stronger inhibitive effect on microtubule assembly in vitro. Arch Biochem Biophys 2008; 470:83-92. [DOI: 10.1016/j.abb.2007.11.007] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2007] [Revised: 11/08/2007] [Accepted: 11/11/2007] [Indexed: 10/22/2022]
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19
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Butowt R, Davies P, Brown DR. Anterograde axonal transport of chicken cellular prion protein (PrPc) in vivo requires its N-terminal part. J Neurosci Res 2008; 85:2567-79. [PMID: 17335074 DOI: 10.1002/jnr.21229] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The cellular isoform of prion protein (PrP(c)) can exist in membrane-bound and secreted forms. Both forms of PrP(c) can be transported by retinal ganglion cell (RGC) axons along the optic nerve in the anterograde direction. In this study we determined which part of chicken PrP(c) is required for its anterograde axonal transport within the optic nerve of embryonic chicken. We intraocularly injected radio-iodinated fragments of recombinant chicken PrP(c) and then examined their anterograde axonal transport from retina into optic tectum. Using gamma-counting and different autoradiographic techniques we quantified anterograde axonal transport of the N-terminal part of chicken PrP(c) (amino acid residues 1-116) in this model system. The transport of the N-terminal part has similar properties as the anterograde transport of full-length chicken PrP(c) (Butowt et al., 2006) described previously (e.g., has similar efficiency, is microtubule-dependent, and is saturable). Moreover, the pattern of ultrastructural distribution of the N-terminal fragment within RGCs is similar to the distribution of full-length PrP(c). The C-terminal fragment of chicken PrP(c) (residues 118-246) and different PrP-derived peptides were not transported. Moreover, PrP(c)-derived peptides were sorted into different endocytotic pathways in neurons, indicating that they cannot substitute for full-length PrP(c) to study its internalization and trafficking. These data indicate that the N-terminal half of chicken PrP(c) contains the necessary information to drive the internalization and subsequent sorting of extracellular PrP(c) in RGCs soma into the anterograde axonal transport pathway.
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Affiliation(s)
- Rafal Butowt
- Department of Physiology and Cell Biology, University of Nevada, School of Medicine, Reno, Nevada, USA
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20
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Message in a bottle: long-range retrograde signaling in the nervous system. Trends Cell Biol 2007; 17:519-28. [PMID: 18029183 DOI: 10.1016/j.tcb.2007.09.003] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2007] [Revised: 09/07/2007] [Accepted: 09/07/2007] [Indexed: 01/08/2023]
Abstract
In many regions of the nervous system, signals produced by target cells and surrounding glia or in response to in jury are received at axon terminals and then retrogradely propagated to cell bodies where they regulate gene transcription and other cellular processes required for development and adult function. The cellular and molecular mechanisms of axonal retrograde signaling in neurons have traditionally been studied in the context of survival signals provided by target-derived neurotrophic factors, in which signaling endosomes containing endocytosed ligand-receptor complexes and downstream effectors are retrogradely tra nsported by dynein motors. In recent years, this notion has been refined and additional mechanisms for long-range retrograde signaling in axons have been described. This article discusses some outstanding issues in the signaling endosome hypothesis as well as recent findings suggesting the existence of a variety of mechanisms for the retrograde propagation of signals in the nervous system.
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21
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Watts JC, Westaway D. The prion protein family: Diversity, rivalry, and dysfunction. Biochim Biophys Acta Mol Basis Dis 2007; 1772:654-72. [PMID: 17562432 DOI: 10.1016/j.bbadis.2007.05.001] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2006] [Revised: 04/26/2007] [Accepted: 05/02/2007] [Indexed: 11/24/2022]
Abstract
The prion gene family currently consists of three members: Prnp which encodes PrP(C), the precursor to prion disease associated isoforms such as PrP(Sc); Prnd which encodes Doppel, a testis-specific protein involved in the male reproductive system; and Sprn which encodes the newest PrP-like protein, Shadoo, which is expressed in the CNS. Although the identification of numerous candidate binding partners for PrP(C) has hinted at possible cellular roles, molecular interpretations of PrP(C) activity remain obscure and no widely-accepted view as to PrP(C) function has emerged. Nonetheless, studies into the functional interrelationships of prion proteins have revealed an interesting phenomenon: Doppel is neurotoxic to cerebellar cells in a manner which can be blocked by either PrP(C) or Shadoo. Further examination of this paradigm may help to shed light on two prominent unanswered questions in prion biology: the functional role of PrP(C) and the neurotoxic pathways initiated by PrP(Sc) in prion disease.
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Affiliation(s)
- Joel C Watts
- Centre for Research in Neurodegenerative Diseases and Department of Laboratory Medicine and Pathobiology, University of Toronto, Canada
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22
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Abstract
As our knowledge of biological processes advances, we are increasingly aware that cells actively position sub-cellular organelles and other constituents to control a wide range of biological processes. Many studies quantify the position and motion of, for example, fluorescently labeled proteins, protein aggregates, mRNA particles or virus particles. Both differential interference contrast (DIC) and fluorescence microscopy can visualize vesicles, nuclei or other small organelles moving inside cells. While such studies are increasingly important, there has been no complete analysis of the different tracking methods in use, especially from the practical point of view. Here we investigate these methods and clarify how well different algorithms work and also which factors play a role in assessing how accurately the position of an object can be determined. Specifically, we consider how ultimate performance is affected by magnification, by camera type (analog versus digital), by recording medium (VHS and SVHS tape versus direct tracking from camera), by image compression, by type of imaging used (fluorescence versus DIC images) and by a variety of sources of noise. We show that most methods are capable of nanometer scale accuracy under realistic conditions; tracking accuracy decreases with increasing noise. Surprisingly, accuracy is found to be insensitive to the numerical aperture, but, as expected, it scales with magnification, with higher magnification yielding improved accuracy (within limits of signal-to-noise). When noise is present at reasonable levels, the effect of image compression is in most cases small. Finally, we provide a free, robust implementation of a tracking algorithm that is easily downloaded and installed.
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Affiliation(s)
- Brian C Carter
- Department of Physics and Astronomy, University of California Irvine, Irvine, CA 92612, USA
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23
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Hachiya NS, Imagawa M, Kaneko K. The possible role of protein X, a putative auxiliary factor in pathological prion replication, in regulating a physiological endoproteolytic cleavage of cellular prion protein. Med Hypotheses 2007; 68:670-3. [PMID: 17008028 DOI: 10.1016/j.mehy.2006.07.038] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2006] [Accepted: 07/19/2006] [Indexed: 10/24/2022]
Abstract
The posttranslational conformational conversion of the cellular isoform of prion protein PrP(C) into its scrapie isoform PrP(Sc) is the fundamental process underlying the pathogenesis of prion disease. Based on several transgenic data, it has been postulated that a putative auxiliary factor denoted protein X functions as a molecular chaperone through its unfolding activity of PrP(C) during the formation of PrP(Sc). However, the assumption that protein X therefore exists exclusively in prion diseases appears improbable and thus, it should have some simultaneous physiological role. We, hereby, propose a novel concept - a characteristic role of protein X in supporting a physiological endoproteolytic cleavage of PrP(C). The events corresponding to the formation of the physiologically metabolized PrP(C) or the pathologically transformed PrP(Sc) are mutually exclusive. Amino acid residues that are critical in terms of the target site of protein X for the pathological alteration into PrP(Sc) overlap at the cleavage site. These amino acid residues tend to have a hydrophobic property and are most probably found buried inside the native protein structure. Therefore, a putative molecular chaperone identical to protein X may target the same hydrophobic residues in PrP(C) and work in conjunction with either PrP(Sc) in prion disease or PrP proteases during the physiological state. This postulation may help explain in a relatively simple manner these two mutually exclusive phenomena, viz. the physiological endoproteolytic cleavage of PrP(C) and its pathological conversion into PrP(Sc).
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Affiliation(s)
- Naomi S Hachiya
- Department of Neurophysiology, Tokyo Medical University, 6-1-1 Shinjuku, Tokyo 160-8402, Japan
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24
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Nieznanski K, Podlubnaya ZA, Nieznanska H. Prion protein inhibits microtubule assembly by inducing tubulin oligomerization. Biochem Biophys Res Commun 2006; 349:391-9. [PMID: 16934224 DOI: 10.1016/j.bbrc.2006.08.051] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2006] [Accepted: 08/11/2006] [Indexed: 11/24/2022]
Abstract
A growing body of evidence points to an association of prion protein (PrP) with microtubular cytoskeleton. Recently, direct binding of PrP to tubulin has also been found. In this work, using standard light scattering measurements, sedimentation experiments, and electron microscopy, we show for the first time the effect of a direct interaction between these proteins on tubulin polymerization. We demonstrate that full-length recombinant PrP induces a rapid increase in the turbidity of tubulin diluted below the critical concentration for microtubule assembly. This effect requires magnesium ions and is weakened by NaCl. Moreover, the PrP-induced light scattering structures of tubulin are cold-stable. In preparations of diluted tubulin incubated with PrP, electron microscopy revealed the presence of approximately 50 nm disc-shaped structures not reported so far. These unique tubulin oligomers may form large aggregates. The effect of PrP is more pronounced under the conditions promoting microtubule formation. In these tubulin samples, PrP induces formation of the above oligomers associated with short protofilaments and sheets of protofilaments into aggregates. Noticeably, this is accompanied by a significant reduction of the number and length of microtubules. Hence, we postulate that prion protein may act as an inhibitor of microtubule assembly by inducing formation of stable tubulin oligomers.
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Affiliation(s)
- Krzysztof Nieznanski
- Nencki Institute of Experimental Biology, Department of Muscle Biochemistry, Warsaw, Poland.
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25
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Huang JB, Espinoza J, Romero R, Petty HR. Apparent role of dynein in glucose-6-phosphate dehydrogenase trafficking in neutrophils from pregnant women. Metabolism 2006; 55:279-81. [PMID: 16483869 DOI: 10.1016/j.metabol.2005.09.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2005] [Accepted: 09/27/2005] [Indexed: 11/22/2022]
Abstract
To better understand the mechanisms of metabolic microcompartmentalization associated with neutrophil hexose monophosphate shunt activity during pregnancy, we have studied the intracellular trafficking of glucose-6-phosphate dehydrogenase (G6PDase). Microtubule motor proteins colocalize with G6PDase. Dynein inhibitors block G6PDase accumulation at the microtubule-organizing center in pregnancy cells. On this basis, we conclude that microtubule motor proteins participate in hexose monophosphate shunt enzyme transport within leukocytes.
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Affiliation(s)
- Ji-Biao Huang
- Department of Ophthalmology and Visual Sciences, The University of Michigan Medical School, Ann Arbor, MI 48105, USA
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26
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Bian J, Nazor KE, Angers R, Jernigan M, Seward T, Centers A, Green M, Telling GC. GFP-tagged PrP supports compromised prion replication in transgenic mice. Biochem Biophys Res Commun 2006; 340:894-900. [PMID: 16386707 DOI: 10.1016/j.bbrc.2005.12.085] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2005] [Accepted: 12/07/2005] [Indexed: 11/16/2022]
Abstract
The ability of green fluorescent protein (GFP)-prion protein (PrP) fusions to support prion propagation has not been demonstrated. Here, we show that while transgenic mice expressing PrP tagged at its amino terminus with enhanced GFP, referred to as EGFPrP-N, supported prion replication, disease onset was prolonged, the brains of diseased mice did not exhibit typical disease neuropathology and disease-associated EGFPrP-N lacked the full spectrum of biochemical properties normally associated with PrP(Sc). Co-expression of wild-type PrP and EGFPrP-N substantially reduced prion incubation times and resulted in accumulation of protease-resistant EGFPrP(Sc)-N in the brains of transgenic mice as well as chronically infected cultured cells, suggesting that wild-type PrP rescued a compromised amino terminal function in EGFPrP-N. While our results show that EGFPrP(C)-N adopts a conformation necessary for the production of infectious prions, the synergistic interaction of wild-type and EGFPrP-N underscores the importance of the amino terminus in modulating prion pathogenesis.
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Affiliation(s)
- Jifeng Bian
- Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky, Lexington, KY 40536, USA
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27
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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.
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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
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28
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Omi K, Hachiya NS, Tokunaga K, Kaneko K. siRNA-mediated inhibition of endogenous Huntington disease gene expression induces an aberrant configuration of the ER network in vitro. Biochem Biophys Res Commun 2005; 338:1229-35. [PMID: 16256944 DOI: 10.1016/j.bbrc.2005.10.061] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2005] [Accepted: 10/06/2005] [Indexed: 11/18/2022]
Abstract
Huntingtin is a ubiquitously expressed cytoplasmic protein encoded by the Huntington disease (HD) gene, in which a CAG expansion induces an autosomal dominant progressive neurodegenerative disorder; however, its biological function has not been completely elucidated. Here, we report for the first time that short interfering RNA (siRNA)-mediated inhibition of endogenous Hdh (a mouse homologue of huntingtin) gene expression induced an aberrant configuration of the endoplasmic reticulum (ER) network in vitro. Studies using immunofluorescence microscopy with several ER markers revealed that the ER network appeared to be congregated in various types of cell lines transfected with siRNA directed against Hdh, but not with other siRNAs so far tested. Other subcellular organelles and structures, including the nucleus, Golgi apparatus, mitochondria, lysosomes, microtubules, actin cytoskeletons, cytoplasm, lipid rafts, and plasma membrane, exhibited normal configurations. Western blot analysis of cellular prion protein (PrP(C)) revealed normal glycosylation, which is a simple marker of post-translational modification in the ER and Golgi compartments, and immunofluorescence microscopy detected no altered subcellular distribution of PrP(C) in the post-ER compartments. Further investigation is required to determine whether the distorted ER network, i.e., loss of the huntingtin function, participates in the development of HD.
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Affiliation(s)
- Kazuya Omi
- Second Department of Physiology, Tokyo Medical University, Tokyo 160-8402, Japan
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29
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Bragason BT, Palsdottir A. Processing of ovine PrP(ARQ)C-EGFP chimeras containing Asn138 and Cys151 polymorphisms. Biochem Biophys Res Commun 2005; 336:544-53. [PMID: 16143302 DOI: 10.1016/j.bbrc.2005.08.124] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2005] [Accepted: 08/12/2005] [Indexed: 10/25/2022]
Abstract
Polymorphisms in the prion protein, PrP(C), affect the susceptibility of sheep to scrapie. Three rare polymorphisms, M137T, S138N, and R151C, have been found in Icelandic sheep. Observations suggest that R151C may be associated with lower scrapie susceptibility, whereas S138N is neutral. The effects of the S138N and R151C polymorphisms on the cellular processing of PrP(C) were examined in a model system consisting of the expression of ovine PrP(C)-EGFP (green fluorescent protein) chimeras in the mouse neuroblastoma cell line N2a. Chimeras with the haplotypes A136R154Q171 (ARQ), AN138RQ, and AC151RQ were compared. The chimeras did not differ regarding their translocation into the secretory system, glycosylation, and transport to the cell surface. However, the AC151RQ chimera differed from the other chimeras regarding disulfide bonding characteristics; furthermore, a slight difference was detected between AC151RQ and the other chimeras by limited proteolysis. The processing of the ARQ and AN138RQ chimeras was identical in the experiments performed consistent with observations that it is neutral.
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Affiliation(s)
- Birkir Thor Bragason
- Institute for Experimental Pathology, Keldur, University of Iceland, Vesturlandsvegur, Reykjavik 112, Iceland
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30
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Nieznanski K, Nieznanska H, Skowronek KJ, Osiecka KM, Stepkowski D. Direct interaction between prion protein and tubulin. Biochem Biophys Res Commun 2005; 334:403-11. [PMID: 16004966 DOI: 10.1016/j.bbrc.2005.06.092] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2005] [Accepted: 06/20/2005] [Indexed: 02/04/2023]
Abstract
Recently published data show that the prion protein in its cellular form (PrP(C)) is a component of multimolecular complexes. In this report, zero-length cross-linking with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) allowed us to identify tubulin as one of the molecules interacting with PrP(C) in complexes observed in porcine brain extracts. We found that porcine brain tubulin added to these extracts can be cross-linked with PrP(C). Moreover, we observed that the 34 kDa species identified previously as full-length diglycosylated prion protein co-purifies with tubulin. Cross-linking of PrP(C) species separated by Cu(2+)-loaded immobilized metal affinity chromatography confirmed that only the full-length protein but not the N-terminally truncated form (C1) binds to tubulin. By means of EDC cross-linking and cosedimentation experiments, we also demonstrated a direct interaction of recombinant human PrP (rPrP) with tubulin. The stoichiometry of cosedimentation implies that rPrP molecules are able to bind both the alpha- and beta-isoforms of tubulin composing microtubule. Furthermore, prion protein exhibits higher affinity for microtubules than for unpolymerized tubulin.
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Affiliation(s)
- Krzysztof Nieznanski
- Department of Muscle Biochemistry, Nencki Institute of Experimental Biology, Warsaw, Poland.
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Hachiya NS, Watanabe K, Kawabata MY, Jozuka A, Kozuka Y, Sakasegawa Y, Kaneko K. Prion protein with Y145STOP mutation induces mitochondria-mediated apoptosis and PrP-containing deposits in vitro. Biochem Biophys Res Commun 2005; 327:894-9. [PMID: 15649429 DOI: 10.1016/j.bbrc.2004.12.079] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2004] [Indexed: 10/26/2022]
Abstract
A pathogenic truncation of an amber mutation at codon 145 (Y145STOP) in Gerstmann-Straussler-Scheinker disease (GSS) was investigated through the real-time imaging in living cells, by utilizing GFP-PrP constructs. GFP-PrP(1-144) exhibited an aberrant localization to mitochondria in mouse neuroblastoma neuro2a (N2a) and HpL3-4 cells, a hippocampal cell line established from prnp gene-ablated mice, whereas full-length GFP-PrP did not. The aberrant mitochondrial localization was also confirmed by Western blot analysis. Since GFP-PrP(1-121), as previously reported, and full-length GFP-PrP do not exhibit such mitochondrial localization, the mitochondrial localization of GFP-PrP(1-144) requires not only PrP residues 121-144 (in human sequence) but also COOH-terminal truncation in the current experimental condition. Subsequently, the GFP-PrP(1-144) induced a change in the mitochondrial innermembrane potential (DeltaPsi(m)), release of cytochrome c from the intermembrane space into the cytosol, and DNA fragmentation in these cells. Non-fluorescent PrP(1-144) also induced the DNA fragmentation in N2a and HpL3-4 cells after the proteasomal inhibition. These data may provide clues as to the molecular mechanism of the neurotoxic property of Y145STOP mutation. Furthermore, immunoelectron microscopy revealed numerous electron-dense deposits in mitochondria clusters of GFP-PrP(1-144)-transfected N2a cells, whereas no deposit was detected in the cells transfected with full-length GFP-PrP. Co-localization of GFP/PrP-immunogold particles with porin-immunogold particles as a mitochondrial marker was observed in such electron-dense vesicular foci, resembling those found in autophagic vacuoles forming secondary lysosomes. Whether such electron-dense deposits may serve as a seed for the growth of amyloid plaques, a characteristic feature of GSS with Y145STOP, awaits further investigations.
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Affiliation(s)
- Naomi S Hachiya
- Department of Cortical Function Disorders, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo 187-8502, Japan
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Schnaeker EM, Ossig R, Ludwig T, Dreier R, Oberleithner H, Wilhelmi M, Schneider SW. Microtubule-dependent matrix metalloproteinase-2/matrix metalloproteinase-9 exocytosis: prerequisite in human melanoma cell invasion. Cancer Res 2005; 64:8924-31. [PMID: 15604254 DOI: 10.1158/0008-5472.can-04-0324] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases that cleave and degrade a wide spectrum of extracellular matrix components. By enhancing turnover of extracellular matrix, MMP activity is also known to play a key role in tumor cell invasion. Because extracellular protease activity requires efficient release of these proteases to the cellular surface, we investigated storage, transport, and exocytosis of MMP-2 and MMP-9 in human melanoma cells using immunofluorescence, electrical, and biochemical techniques. Immunolabeling of melanoma cells with antibodies specific for MMP-2 and MMP-9 led to the identification of two distinct populations of small cytoplasmatic vesicles containing MMP-2 or MMP-9, respectively. In combination with alpha-tubulin-specific antibodies, both vesicle populations were found to be aligned along the microtubular network. Moreover, the molecular motor protein kinesin is shown to be localized on most of these vesicles, providing evidence that the identified vesicles are actively propelled along microtubules toward the plasma membrane. The functional relevance of these findings is demonstrated using low dosage (5.9 nmol/L) of paclitaxel to affect the microtubular function of melanoma cells. Although cell proliferation is not altered, paclitaxel treatment impairs secretion of MMP-2/MMP-9 and significantly reduces invasive activity in our new cell invasion assay. In conclusion, we demonstrate in melanoma cells that microtubule-dependent traffic of MMP-containing vesicles and exocytosis are critical steps for invasive behavior and therefore are potential targets for specific antitumor drugs.
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Affiliation(s)
- Eva-Maria Schnaeker
- Institute of Physiology-Nanolab, Institute of Physiological Chemistry and Pathobiochemistry, and Department of Dermatology, University of Muenster, Muenster, Germany
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Hafezparast M, Brandner S, Linehan J, Martin JE, Collinge J, Fisher EMC. Prion disease incubation time is not affected in mice heterozygous for a dynein mutation. Biochem Biophys Res Commun 2005; 326:18-22. [PMID: 15567146 DOI: 10.1016/j.bbrc.2004.10.206] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2004] [Indexed: 11/13/2022]
Abstract
A mechanism for transmission of the infectious prions from the peripheral nerve ends to the central nervous system is thought to involve neuronal anterograde and retrograde transport systems. Cytoplasmic dynein is the major retrograde transport molecular motor whose function is impaired in the Legs at odd angles (Loa) mouse due to a point mutation in the cytoplasmic dynein heavy chain subunit. Loa is a dominant trait which causes neurodegeneration and progressive motor function deficit in the heterozygotes. To investigate the role of cytoplasmic dynein in the transmission of prions within neurons, we inoculated heterozygous Loa and wild type littermates with mouse-adapted scrapie prions intracerebrally and intraperitonially, and determined the incubation period to onset of clinical prion disease. Our data indicate that the dynein mutation in the heterozygous state does not affect prion disease incubation time or its neuropathology in Loa mice.
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Affiliation(s)
- Majid Hafezparast
- Department of Neurodegenerative Disease, Institute of Neurology, National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK.
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Drisaldi B, Coomaraswamy J, Mastrangelo P, Strome B, Yang J, Watts JC, Chishti MA, Marvi M, Windl O, Ahrens R, Major F, Sy MS, Kretzschmar H, Fraser PE, Mount HTJ, Westaway D. Genetic Mapping of Activity Determinants within Cellular Prion Proteins. J Biol Chem 2004; 279:55443-54. [PMID: 15459186 DOI: 10.1074/jbc.m404794200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The PrP-like Doppel (Dpl) protein causes apoptotic death of cerebellar neurons in transgenic mice, a process prevented by expression of the wild type (wt) cellular prion protein, PrP(C). Internally deleted forms of PrP(C) resembling Dpl such as PrPDelta32-121 produce a similar PrP(C)-sensitive pro-apoptotic phenotype in transgenic mice. Here we demonstrate that these phenotypic attributes of wt Dpl, wt PrP(C), and PrPDelta132-121 can be accurately recapitulated by transfected mouse cerebellar granule cell cultures. This system was then explored by mutagenesis of the co-expressed prion proteins to reveal functional determinants. By this means, neuroprotective activity of wt PrP(C) was shown to be nullified by a deletion of the N-terminal charged region implicated in endocytosis and retrograde axonal transport (PrPDelta23-28), by deletion of all five octarepeats (PrPDelta51-90), or by glycine replacement of four octarepeat histidine residues required for selective binding of copper ions (Prnp"H/G"). In the case of Dpl, overlapping deletions defined a requirement for the gene interval encoding helices B and B' (DplDelta101-125). These data suggest contributions of copper binding and neuronal trafficking to wt PrP(C) function in vivo and place constraints upon current hypotheses to explain Dpl/PrP(C) antagonism by competitive ligand binding. Further implementation of this assay should provide a fuller understanding of the attributes and subcellular localizations required for activity of these enigmatic proteins.
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Affiliation(s)
- Bettina Drisaldi
- Centre for Research in Neurodegenerative Diseases, Tanz Neuroscience Building, 6 Queen's Park Crescent West, University of Toronto, Toronto, Ontario M5S 3H2, Canada
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Hachiya NS, Sakasegawa Y, Sasaki H, Jozuka A, Tsukita S, Kaneko K. Oligomeric Aip2p/Dld2p modifies the protein conformation of both properly folded and misfolded substrates in vitro. Biochem Biophys Res Commun 2004; 323:339-44. [PMID: 15351742 DOI: 10.1016/j.bbrc.2004.08.098] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2004] [Indexed: 10/26/2022]
Abstract
Oligomeric actin-interacting protein 2 (Aip2p) [Nat. Struct. Biol. 2 (1995) 28]/D-lactate dehydrogenase protein 2 (Dld2p) [Yeast 15 (1999) 1377, Biochem. Biophys. Res. Commun. 295 (2002) 910] exhibits the unique grapple-like structure with an ATP-dependent opening [Biochem. Biophys. Res. Commun. 320 (2004) 1271], which is required for the F-actin conformation modifying activity in vitro and in vivo [Biochem. Biophys. Res. Commun. 319 (2004) 78]. To further investigate the molecular nature of oligomeric Aip2p/Dld2p, the substrate specificity of its binding and protein conformation modifying activity was examined. In the presence of 1mM ATP or AMP-PNP, oligomeric Aip2p/Dld2p bound to all substrates so far examined, and modified the conformation of actin, DNase I, the mature form of invertase, prepro-alpha-factor, pro-alpha-factor, and mitochondrial superoxide dismutase, as determined by the trypsin susceptibility assay. Of note, the activity could modify even the conformation of pathogenic highly aggregated polypeptides, such as recombinant prion protein in beta-sheet form, alpha-synuclein, and amyloid beta (1-42) in the presence of ATP. The in vivo protein conformation modifying activity, however, depends on the growth stage; the most significant substrate modification activity was observed in yeast cells at the log phase, suggesting the presence of a cofactor/s in yeast cells, where F-actin is supposed to be a major target in vivo. These data further support our previous notion that the oligomeric Aip2p/Dld2p may belong to an unusual class of molecular chaperones [Biochem. Biophys. Res. Commun. 320 (2004) 1271], which can target both properly folded and misfolded proteins in an ATP-dependent manner in vitro.
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Affiliation(s)
- Naomi S Hachiya
- Department of Cortical Function Disorders, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo 187-8502, Japan
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Nandi PK, Nicole JC. Nucleic Acid and Prion Protein Interaction Produces Spherical Amyloids which can Function in vivo as Coats of Spongiform Encephalopathy Agent. J Mol Biol 2004; 344:827-37. [PMID: 15533448 DOI: 10.1016/j.jmb.2004.09.080] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2004] [Revised: 09/24/2004] [Accepted: 09/27/2004] [Indexed: 11/15/2022]
Abstract
The infectious agent of transmissible spongiform encephalopathies (TSE) has been considered to be PrP(SC), a structural isoform of cellular prion protein PrP(C). PrP(SC) can exist as oligomers and/or as amyloid polymers. Nucleic acids induce structural conversion of recombinant prion protein PrP and PrP(C) to PrP(SC) form in solution and in vitro. Here, we report that nucleic acids, by interacting with PrP in solution, produce amyloid fibril and fibres of different morphologies, similar to those identified in the diseased brains. In addition, the same interaction produces polymer lattices and spherical amyloids of different dimensions (15-150 nm in diameters). The polymer lattices show apparent morphological similarity to the two-dimensional amyloid crystals obtained from linear amyloids isolated in vivo. The spherical amyloids structurally resemble "spherical particles" observed in natural spongiform encephalopathy (SE) and in scrapie-infected brains (TSE). We suggest that spherical amyloids, PrP(SC)-amylospheroids, are probable constituents of the coat of the spherical particles found in vivo and the latter can act as protective coats of the SE and TSE agents in vivo.
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Affiliation(s)
- P K Nandi
- Pathologie Infectieuse et Immunologie, Institut National de la Recherche Agronomique, 37380 Nouzilly, France.
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Cereghetti GM, Negro A, Vinck E, Massimino ML, Sorgato MC, Van Doorslaer S. Copper(II) Binding to the Human Doppel Protein May Mark Its Functional Diversity from the Prion Protein. J Biol Chem 2004; 279:36497-503. [PMID: 15218028 DOI: 10.1074/jbc.m404341200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Doppel (Dpl) is the first described homologue of the prion protein, the main constituent of the agent responsible for prion diseases. The cellular prion protein (PrP(C)) is predominantly present in the central nervous system. Although its role is not yet completely clarified, PrP(C) seems to be involved in Cu(2+) recycling from synaptic clefts and in preventing neuronal oxidative damage. Conversely, Dpl is expressed in heart and testis and has been shown to regulate male fertility by intervening in gametogenesis and sperm-egg interactions. Therefore, despite a high sequence homology and a similar three-dimensional fold, the functions of PrP(C) and Dpl appear unrelated. Here we show by electron paramagnetic resonance and fluorescence spectroscopy that the in vitro binding of copper(II) to human recombinant Dpl occurs with a different pattern from that observed for recombinant PrP. At physiological pH values, two copper(II)-binding sites with different affinities were found in Dpl. At lower pH values, two additional copper(II)-binding sites can be identified as follows: one complex is present only at pH 4, and the other is observed in the pH range 5-6. As derived from the electron paramagnetic resonance characteristics, all Dpl-copper(II) complexes have a different coordination sphere from those present in PrP. Furthermore, in contrast to the effect shown previously for PrP(C), addition of Cu(2+) to Dpl-expressing cells does not cause Dpl internalization. These results suggest that binding of the ion to PrP(C) and Dpl may contribute to the different functional roles ascribed to these highly homologous proteins.
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Affiliation(s)
- Grazia M Cereghetti
- Dipartimento di Chimica Biologica, C.R.I.B.I., Università di Padova, Viale G. Colombo 3, I-35121 Padua, Italy
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