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C subunit of the ATP synthase is an amyloidogenic calcium dependent channel-forming peptide with possible implications in mitochondrial permeability transition. Sci Rep 2021; 11:8744. [PMID: 33888826 PMCID: PMC8062469 DOI: 10.1038/s41598-021-88157-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 04/06/2021] [Indexed: 01/18/2023] Open
Abstract
The c subunit is an inner mitochondrial membrane (IMM) protein encoded by three nuclear genes. Best known as an integral part of the F0 complex of the ATP synthase, the c subunit is also present in other cytoplasmic compartments in ceroid lipofuscinoses. Under physiological conditions, this 75 residue-long peptide folds into an α-helical hairpin and forms oligomers spanning the lipid bilayer. In addition to its physiological role, the c subunit has been proposed as a key participant in stress-induced IMM permeabilization by the mechanism of calcium-induced permeability transition. However, the molecular mechanism of the c subunit participation in IMM permeabilization is not completely understood. Here we used fluorescence spectroscopy, atomic force microscopy and black lipid membrane methods to gain insights into the structural and functional properties of unmodified c subunit protein that might make it relevant to mitochondrial toxicity. We discovered that c subunit is an amyloidogenic peptide that can spontaneously fold into β-sheets and self-assemble into fibrils and oligomers in a Ca2+-dependent manner. C subunit oligomers exhibited ion channel activity in lipid membranes. We propose that the toxic effects of c subunit might be linked to its amyloidogenic properties and are driven by mechanisms similar to those of neurodegenerative polypeptides such as Aβ and α-synuclein.
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2
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Amodeo GF, Pavlov EV. Amyloid β, α-synuclein and the c subunit of the ATP synthase: Can these peptides reveal an amyloidogenic pathway of the permeability transition pore? BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1863:183531. [PMID: 33309700 DOI: 10.1016/j.bbamem.2020.183531] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 10/26/2020] [Accepted: 11/09/2020] [Indexed: 01/29/2023]
Abstract
Mitochondrial Permeability Transition (PT) is a phenomenon of increased permeability of the inner mitochondrial membrane in response to high levels of Ca2+ and/or reactive oxygen species (ROS) in the matrix. PT occurs upon the opening of a pore, namely the permeability transition pore (PTP), which dissipates the membrane potential uncoupling the respiratory chain. mPT activation and PTP formation can occur through multiple molecular pathways. The specific focus of this review is to discuss the possible molecular mechanisms of PTP that involve the participation of mitochondrially targeted amyloid peptides Aβ, α-synuclein and c subunit of the ATP synthase (ATPase). As activators of PTP, amyloid peptides are uniquely different from other activators because they are capable of forming channels in lipid bilayers. This property rises the possibility that in this permeabilization pathway the formation of the channel involves the direct participation of peptides, making it uniquely different from other PTP induction mechanisms. In this pathway, a critical step of PTP activation involves the import of amyloidogenic peptides from the cytosol into the matrix. In the matrix these peptides, which would fold into α-helical structure in native conditions, interact with cyclophilin D (CypD) and upon stimulation by elevated ROS and/or the Ca2+ spontaneously misfold into β-sheet ion conducting pores, causing PTP opening.
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Affiliation(s)
- Giuseppe F Amodeo
- Department of Molecular Pathobiology, New York University, United States of America.
| | - Evgeny V Pavlov
- Department of Molecular Pathobiology, New York University, United States of America.
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3
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Abstract
Mitochondrial ATP generation by oxidative phosphorylation combines the stepwise oxidation by the electron transport chain (ETC) of the reducing equivalents NADH and FADH2 with the generation of ATP by the ATP synthase. Recent studies show that the ATP synthase is not only essential for the generation of ATP but may also contribute to the formation of the mitochondrial permeability transition pore (PTP). We present a model, in which the PTP is located within the c-subunit ring in the Fo subunit of the ATP synthase. Opening of the PTP was long associated with uncoupling of the ETC and the initiation of programmed cell death. More recently, it was shown that PTP opening may serve a physiologic role: it can transiently open to regulate mitochondrial signaling in mature cells, and it is open in the embryonic mouse heart. This review will discuss how the ATP synthase paradoxically lies at the center of both ATP generation and cell death.
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Amodeo GF, Solesio ME, Pavlov EV. From ATP synthase dimers to C-ring conformational changes: unified model of the mitochondrial permeability transition pore. Cell Death Dis 2017; 8:1. [PMID: 29233966 PMCID: PMC5839071 DOI: 10.1038/s41419-017-0042-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2017] [Revised: 08/11/2017] [Accepted: 10/06/2017] [Indexed: 12/24/2022]
Affiliation(s)
- Giuseppe Federico Amodeo
- Department of Basic Sciences, New York University, College of Dentistry, 345 East 24th Street, New York, NY, 10010, USA
| | - Maria E Solesio
- Department of Basic Sciences, New York University, College of Dentistry, 345 East 24th Street, New York, NY, 10010, USA
| | - Evgeny V Pavlov
- Department of Basic Sciences, New York University, College of Dentistry, 345 East 24th Street, New York, NY, 10010, USA.
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5
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Bonora M, Wieckowski MR, Chinopoulos C, Kepp O, Kroemer G, Galluzzi L, Pinton P. Molecular mechanisms of cell death: central implication of ATP synthase in mitochondrial permeability transition. Oncogene 2015; 34:1475-86. [PMID: 24727893 DOI: 10.1038/onc.2014.96] [Citation(s) in RCA: 169] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Revised: 02/20/2014] [Accepted: 02/27/2014] [Indexed: 12/14/2022]
Abstract
The term mitochondrial permeability transition (MPT) is commonly used to indicate an abrupt increase in the permeability of the inner mitochondrial membrane to low molecular weight solutes. Widespread MPT has catastrophic consequences for the cell, de facto marking the boundary between cellular life and death. MPT results indeed in the structural and functional collapse of mitochondria, an event that commits cells to suicide via regulated necrosis or apoptosis. MPT has a central role in the etiology of both acute and chronic diseases characterized by the loss of post-mitotic cells. Moreover, cancer cells are often relatively insensitive to the induction of MPT, underlying their increased resistance to potentially lethal cues. Thus, intense efforts have been dedicated not only at the understanding of MPT in mechanistic terms, but also at the development of pharmacological MPT modulators. In this setting, multiple mitochondrial and extramitochondrial proteins have been suspected to critically regulate the MPT. So far, however, only peptidylprolyl isomerase F (best known as cyclophilin D) appears to constitute a key component of the so-called permeability transition pore complex (PTPC), the supramolecular entity that is believed to mediate MPT. Here, after reviewing the structural and functional features of the PTPC, we summarize recent findings suggesting that another of its core components is represented by the c subunit of mitochondrial ATP synthase.
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Affiliation(s)
- M Bonora
- Section of Pathology, Oncology and Experimental Biology, Laboratory for Technologies of Advanced Therapies (LTTA), Department of Morphology, Surgery and Experimental Medicine, Interdisciplinary Centre for the Study of Inflammation (ICSI), University of Ferrara, Ferrara, Italy
| | - M R Wieckowski
- Department of Biochemistry, Nencki Institute of Experimental Biology, Warsaw, Poland
| | - C Chinopoulos
- Department of Medical Biochemistry, Semmelweis University, Budapest, Hungary
| | - O Kepp
- 1] Equipe 11 labelisée par la Ligue Nationale contre le cancer, INSERM U1138, Centre de Recherche des Cordeliers, Paris, France [2] Université Paris Descartes/Paris 5, Sorbonne Paris Cité, Paris, France [3] Metabolomics and Cell Biology platforms, Gustave Roussy Comprehensive Cancer Center, Villejuif, France
| | - G Kroemer
- 1] Equipe 11 labelisée par la Ligue Nationale contre le cancer, INSERM U1138, Centre de Recherche des Cordeliers, Paris, France [2] Université Paris Descartes/Paris 5, Sorbonne Paris Cité, Paris, France [3] Metabolomics and Cell Biology platforms, Gustave Roussy Comprehensive Cancer Center, Villejuif, France [4] Pôle de Biologie, Hôpital Européen Georges Pompidou, AP-HP, Paris, France
| | - L Galluzzi
- 1] Equipe 11 labelisée par la Ligue Nationale contre le cancer, INSERM U1138, Centre de Recherche des Cordeliers, Paris, France [2] Université Paris Descartes/Paris 5, Sorbonne Paris Cité, Paris, France [3] Gustave Roussy Comprehensive Cancer Center, Villejuif, France
| | - P Pinton
- Section of Pathology, Oncology and Experimental Biology, Laboratory for Technologies of Advanced Therapies (LTTA), Department of Morphology, Surgery and Experimental Medicine, Interdisciplinary Centre for the Study of Inflammation (ICSI), University of Ferrara, Ferrara, Italy
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6
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Alam MR, Baetz D, Ovize M. Cyclophilin D and myocardial ischemia-reperfusion injury: a fresh perspective. J Mol Cell Cardiol 2015; 78:80-9. [PMID: 25281838 DOI: 10.1016/j.yjmcc.2014.09.026] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2014] [Revised: 09/23/2014] [Accepted: 09/25/2014] [Indexed: 01/06/2023]
Abstract
Reperfusion is characterized by a deregulation of ion homeostasis and generation of reactive oxygen species that enhance the ischemia-related tissue damage culminating in cell death. The mitochondrial permeability transition pore (mPTP) has been established as an important mediator of ischemia-reperfusion (IR)-induced necrotic cell death. Although a handful of proteins have been proposed to contribute in mPTP induction, cyclophilin D (CypD) remains its only bona fide regulatory component. In this review we summarize existing knowledge on the involvement of CypD in mPTP formation in general and its relevance to cardiac IR injury in specific. Moreover, we provide insights of recent advancements on additional functions of CypD depending on its interaction partners and post-translational modifications. Finally we emphasize the therapeutic strategies targeting CypD in myocardial IR injury. This article is part of a Special Issue entitled "Mitochondria: From Basic Mitochondrial Biology to Cardiovascular Disease".
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Affiliation(s)
- Muhammad Rizwan Alam
- INSERM U1060, CarMeN Laboratory, Claude Bernard Lyon 1 University, F-69373 Lyon, France
| | - Delphine Baetz
- INSERM U1060, CarMeN Laboratory, Claude Bernard Lyon 1 University, F-69373 Lyon, France
| | - Michel Ovize
- INSERM U1060, CarMeN Laboratory, Claude Bernard Lyon 1 University, F-69373 Lyon, France; Hospices Civils de Lyon, Hôpital Louis Pradel, Service d'Explorations Fonctionnelles Cardiovasculaires & CIC de Lyon, F-69394 Lyon, France.
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Bonora M, Pinton P. Shedding light on molecular mechanisms and identity of mPTP. Mitochondrion 2014; 21:11. [PMID: 25315653 DOI: 10.1016/j.mito.2014.10.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2014] [Accepted: 10/06/2014] [Indexed: 10/24/2022]
Affiliation(s)
- Massimo Bonora
- Section of Pathology Oncology, Experimental Biology Laboratory for Technologies of Advanced Therapies (LTTA), Department of Morphology, Surgery, and Experimental Medicine, University of Ferrara, Ferrara, Italy
| | - Paolo Pinton
- Section of Pathology Oncology, Experimental Biology Laboratory for Technologies of Advanced Therapies (LTTA), Department of Morphology, Surgery, and Experimental Medicine, University of Ferrara, Ferrara, Italy.
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Chinopoulos C, Szabadkai G. What Makes You Can also Break You, Part III: Mitochondrial Permeability Transition Pore Formation by an Uncoupling Channel within the C-Subunit Ring of the F1FO ATP Synthase? Front Oncol 2014; 4:235. [PMID: 25232534 PMCID: PMC4153043 DOI: 10.3389/fonc.2014.00235] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Accepted: 08/11/2014] [Indexed: 11/13/2022] Open
Affiliation(s)
| | - Gyorgy Szabadkai
- Department of Cell and Developmental Biology, Consortium for Mitochondrial Research, University College London , London , UK ; Department of Biomedical Sciences, University of Padua , Padua , Italy
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Bonora M, Bravo-San Pedro JM, Kroemer G, Galluzzi L, Pinton P. Novel insights into the mitochondrial permeability transition. Cell Cycle 2014; 13:2666-70. [PMID: 25486353 PMCID: PMC4612113 DOI: 10.4161/15384101.2014.949082] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Accepted: 07/10/2014] [Indexed: 11/19/2022] Open
Abstract
Alavian and colleagues recently provided further evidence in support of the notion that the c subunit of the mitochondrial F1FO ATP synthase constitutes the long-sought pore-forming unit of the supramolecular complex responsible for the so-called 'mitochondrial permeability transition' (MPT). Besides shedding new light on the molecular mechanisms that underlie the MPT, these findings corroborate the notion that several components of the cell death machinery, including cytochrome c and the F1FO ATP synthase, mediate critical metabolic activities.
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Key Words
- AIFM1, apoptosis-inducing factor mitochondrion-associated, 1
- ATP5G, ATP synthase, H+ transporting, mitochondrial FO complex, subunit C
- BCL-XL
- CYPD cyclophilin D
- CYTC holocytochrome c
- CsA, cyclosporin A
- IMM, inner mitochondrial membrane
- MCU, mitochondrial calcium uniporter
- MPT, mitochondrial permeability transition
- PPIF, peptidylprolyl isomerase F
- PTPC, permeability transition pore complex
- RCD, regulated cell death
- SMV, submitochondrial vesicle.
- apoptosis
- cyclophilin D
- cyclosporin A
- necrosis
- permeability transition pore complex
- Δψm; mitochondrial transmembrane potential
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Affiliation(s)
- Massimo Bonora
- Section of Pathology, Oncology and Experimental Biology; Laboratory for Technologies of Advanced Therapies (LTTA); Department of Morphology, Surgery and Experimental Medicine; University of Ferrara; Ferrara, Italy
| | - José Manuel Bravo-San Pedro
- Equipe 11 labelisée par la Ligue Nationale contre le cancer, Centre de Recherche des Cordeliers; Paris, France
- INSERM, U1138; Paris, France
- Gustave Roussy Comprehensive Cancer Center; Villejuif, France
| | - Guido Kroemer
- Equipe 11 labelisée par la Ligue Nationale contre le cancer, Centre de Recherche des Cordeliers; Paris, France
- INSERM, U1138; Paris, France
- Université Paris Descartes/Paris 5; Sorbonne Paris Cité; Paris, France
- Metabolomics and Cell Biology platforms, Gustave Roussy Comprehensive Cancer Center; Villejuif, France
- Pôle de Biologie, Hôpital Européen Georges Pompidou; AP-HP; Paris, France
| | - Lorenzo Galluzzi
- Equipe 11 labelisée par la Ligue Nationale contre le cancer, Centre de Recherche des Cordeliers; Paris, France
- Gustave Roussy Comprehensive Cancer Center; Villejuif, France
- Université Paris Descartes/Paris 5; Sorbonne Paris Cité; Paris, France
| | - Paolo Pinton
- Section of Pathology, Oncology and Experimental Biology; Laboratory for Technologies of Advanced Therapies (LTTA); Department of Morphology, Surgery and Experimental Medicine; University of Ferrara; Ferrara, Italy
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10
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Abstract
We consider an ancient protein, and water as a smooth surface, and show that the interaction of the two allows the protein to change its hydrogen bonding to encapsulate the water. This property could have made a three-dimensional microenvironment, 3-4 Gyr ago, for the evolution of subsequent complex water-based chemistry. Proteolipid, subunit c of ATP synthase, when presented with a water surface, changes its hydrogen bonding from an alpha-helix to beta-sheet-like configuration and moves away from its previous association with lipid to interact with water surface molecules. Protein sheets with an intra-sheet backbone spacing of 3.7A and inter-sheet spacing of 6.0 A hydrogen bond into long ribbons or continuous surfaces to completely encapsulate a water droplet. The resulting morphology is a spherical vesicle or a hexagonal crystal of water ice, encased by a skin of subunit c. Electron diffraction shows the crystals to be highly ordered and compressed and the protein skin to resemble beta-sheets. The protein skin can retain the entrapped water over a temperature rise from 123 to 223 K at 1 x 10(-4) Pa, whereas free water starts to sublime significantly at 153 K.
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Affiliation(s)
- Julie E M McGeoch
- Department of Molecular and Cellular Biology, Harvard University, 7 Divinity Avenue, Cambridge, MA 02138, USA.
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Boriack RL, Bennett MJ. CLN-3 protein is expressed in the pancreatic somatostatin-secreting delta cells. Eur J Paediatr Neurol 2001; 5 Suppl A:99-102. [PMID: 11589017 DOI: 10.1053/ejpn.2000.0443] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Juvenile neuronal ceroid lipofuscinosis (JNCL) is a severe autosomal recessive neurodegenerative disorder resulting from mutations in the CLN3 gene. The gene product is a 438-amino acid hydrophobic peptide of unknown function containing five transmembrane domains. In order to study the tissue distribution of the peptide, polyclonal antibodies were raised in rabbits to three epitopes and were affinity purified before use. All three antibodies were used together for immunocytochemical staining of human pancreas. This staining showed localization in pancreatic islet cells. Double labelling of the tissue indicated that cells staining for the CLN3 protein were also positive for somatostatin.
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Affiliation(s)
- R L Boriack
- Department of Pathology, Children's Medical Center of Dallas, 1935 Motor Street, Dallas, Texas 75235, USA
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Das AM, von Harlem R, Feist M, Lücke T, Kohlschütter A. Altered levels of high-energy phosphate compounds in fibroblasts from different forms of neuronal ceroid lipofuscinoses: further evidence for mitochondrial involvement. Eur J Paediatr Neurol 2001; 5 Suppl A:143-6. [PMID: 11588986 DOI: 10.1053/ejpn.2000.0451] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The pathogenesis of neurodegeneration in neuronal ceroid lipofuscinosis (NCL) is still not clear despite progress in mutation analysis of these diseases. We have recently observed anomalies at the level of the mitochondrial ATPsynthase (complex V of the respiratory chain) in fibroblasts from children with CLN1, CLN2, CLN3 and in an ovine model (OCL6). The measurements were carried out in vitro. If these alterations were of relevance in vivo as well, contents of high-energy phosphate compounds should be reduced. In the present study, we measured levels of creatine phosphate (CP), ATP, ADP and AMP in fibroblasts from children with CLN1, CLN2, CLN3 and in OCL6. ATP was reduced to about 50% of normal in CLN1, CLN2 and CLN3, ADP was about 30% of normal in these cells, and CP was 50% of normal in CLN1 and CLN2 but remained normal in CLN3. In fibroblasts of NCL-sheep, however, CP and ADP were increased to 690% and 220% of normal, respectively, while ATP remained normal. If the anomalies found in cellular energy metabolism in fibroblasts were expressed in neurons from NCL patients and NCL sheep 'slow-onset excitotoxicity' could occur leading to cellular dysfunction and eventually to cell death.
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Affiliation(s)
- A M Das
- Department of Paediatrics, Hanover Medical School, Carl Neuberg Str. 1, D-30623 Hanover, Germany.
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Kida E, Golabek AA, Wisniewski KE. Cellular pathology and pathogenic aspects of neuronal ceroid lipofuscinoses. ADVANCES IN GENETICS 2001; 45:35-68. [PMID: 11332776 DOI: 10.1016/s0065-2660(01)45003-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
Lysosomal accumulation of autofluorescent, ceroid lipopigment material in various tissues and organs is a common feature of the neuronal ceroid lipofuscinoses (NCLs). However, recent clinicopathologic and genetic studies have evidenced that NCLs encompass a group of highly heterogeneous disorders. In five of the eight NCL variants distinguished at present, genes associated with the disease process have been isolated and characterized (CLN1, CLN2, CLN3, CLN5, CLN8). Only products of two of these genes, CLN 1 and CLN2, have structural and functional properties of lysosomal enzymes. Nevertheless, according to the nature of the material accumulated in the lysosomes, NCLs in humans as well as natural animal models of these disorders can be divided into two major groups: those characterized by the prominent storage of saposins A and D, and those showing the predominance of subunit c of mitochondrial ATP synthase accumulation. Thus, taking into account the chemical character of the major component of the storage material, NCLs can be classified currently as proteinoses. Of importance, although lysosomal storage material accumulates in NCL subjects in various organs, only brain tissue shows severe dysfunction and cell death, another common feature of the NCL disease process. However, the relation between the genetic defects associated with the NCL forms, the accumulation of storage material, and tissue damage is still unknown. This chapter introduces the reader to the complex pathogenesis of NCLs and summarizes our current knowledge of the potential consequences of the genetic defects of NCL-associated proteins on the biology of the cell.
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Affiliation(s)
- E Kida
- Department of Pathological Neurobiology, New York State Institute for Basic Research in Developmental Disabilities, Staten Island 10314, USA
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McGeoch JE, Guidotti G. Batten disease and the control of the Fo subunit c pore by cGMP and calcium. Eur J Paediatr Neurol 2001; 5 Suppl A:147-50. [PMID: 11588987 DOI: 10.1053/ejpn.2000.0452] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Subunit c of ATP synthase functions as a high conductance ion channel, tightly regulated by calcium. We have suggested that the pathogenesis of Batten syndromes involving overaccumulation of subunit c are linked to the protein's ion channel function. In normal electrically excitable tissue the channel could act as a pacer setting nodal voltage via control of cation entry. The channel conductance is controlled by voltage, calcium, cyclic nucleotides and polyamines. We discuss the pathogenic role that subunit c could play in the electrically excitable tissues of retina, brain and heart where Batten neurodegeneration is seen. Focus is given to potential links between subunit c and the known mutant gene products in the Batten diseases, the process of apoptosis, and the requirement of the growing brain for gradients of cGMP, a ligand of the subunit c channel.
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Affiliation(s)
- J E McGeoch
- Department of Molecular and Cellular Biology, Harvard University, 7 Divinity Avenue, Cambridge, MA 02138, USA.
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15
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McGeoch JE, McGeoch MW, Mao R, Guidotti G. Opposing actions of cGMP and calcium on the conductance of the F(0) subunit c pore. Biochem Biophys Res Commun 2000; 274:835-40. [PMID: 10924363 DOI: 10.1006/bbrc.2000.3231] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Subunit c of ATP synthase can be purified from neuronal plasma membrane and from the inner mitochondrial membrane. In the latter location the hydrophobic 75 amino acid protein is one component of the F(1) F(0) ATP synthase complex but in the former it is alone as a pore that is capable of generating spontaneous electrical oscillations. Pure mammalian subunit c when reconstituted in lipid bilayers and voltage clamped, yields a voltage sensitive pore that conducts a cation current regulated by calcium. The current is here found to be activated by cGMP with a K(M) ranging from 14 nM to 19 microM depending on calcium and temperature. It is sensitively inhibited by a number of ligands. The K(I) for calcium ranges from 100 nM to 100 microM depending on cGMP and temperature. DCCD inhibits with a K(app) of 100 nM. The polyamine nicotine inhibits at 84 nM. The pore has properties that would allow it to deliver sodium or calcium through the cell membrane in a controlled manner while maintaining membrane polarization.
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Affiliation(s)
- J E McGeoch
- Department of Molecular and Cellular Biology, Harvard University, 7 Divinity Avenue, Cambridge, Massachusetts, 02138, USA.
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McGeoch JE, McGeoch MW, Carter DJ, Shuman RF, Guidotti G. Biological-to-electronic interface with pores of ATP synthase subunit C in silicon nitride barrier. Med Biol Eng Comput 2000; 38:113-9. [PMID: 10829401 DOI: 10.1007/bf02344699] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
An oscillator pore is identified that generates intermittent, large amplitude, ionic current in the plasma membrane. The pore is thought to be composed of 10-12 units of subunit c of ATP synthase. Pore opening and closing is a co-operative process, dependent on the release, or binding, of as many as six calcium ions. This mechanism suggests a more general method of co-operative threshold detection of chemical agents via protein modification, the output being directly amplified in a circuit. Here the authors describe steps in the development of a sensor of chemical agents. The subunit c pore in a lipid bilayer spans a nanometer-scale hole in a silicon nitride barrier. Either side of the barrier are electrolyte solutions and current through the pore is amplified by circuitry. The techniques of laser ablation, electron beam lithography and ion beam milling are used to make successively smaller holes to carry the lipid patch. Holes of diameter as small as 20 nm are engineered in a silicon nitride barrier and protein activity in lipid membranes spanning holes as small as 30 nm in diameter is measured. The signal-to-noise ratio of the ionic current is improved by various measures that reduce the effective capacitance of the barrier. Some limits to scale reduction are discussed.
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Affiliation(s)
- J E McGeoch
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, USA.
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18
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Abstract
Specific storage of mitochondrial ATP synthase subunit c occurs in most forms of Batten disease, including the ovine form, but its relationship to the characteristic neurodegeneration is not clear. Storage occurs in most cell types but only neurons are functionally affected. Neurons were cultured from control and affected sheep. Ewes were superovulated and inseminated, and embryos were collected, frozen, stored, and later transplanted into surrogate dams for gestation at times to suit experimental demands. The optimal fetal age for cultures was investigated, from 50 to 125 days. There were no differences between control and affected embryos in this period of rapid growth. At 50 days brains consist of smooth-surfaced hemispheres and cerebellum with no obvious demarcation between gray and white matter. At 90 days they are like miniature adult brains. From 200 to 600 million viable cells were recovered from each fetus, regardless of age. DMEM/F12 with B27 was the most practical medium tested. Cell viability was not as good in medium containing serum. Treatment of surfaces with polylysine aided neuron adhesion. No developmental or viability differences were observed between normal and affected neuron cultures. At plating out cells were rounded. A day later single process outgrowths began. After 4 days these were over 200 microm and by Day 6 had created a network. Most neurons were bipolar. Neurons from 50 to 90-day old fetuses persisted in culture for over 100 days.
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Affiliation(s)
- G W Kay
- Animal and Food Sciences Division, Lincoln University, Canterbury, New Zealand
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