51
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α-Synuclein assembles into higher-order multimers upon membrane binding to promote SNARE complex formation. Proc Natl Acad Sci U S A 2014; 111:E4274-83. [PMID: 25246573 DOI: 10.1073/pnas.1416598111] [Citation(s) in RCA: 341] [Impact Index Per Article: 34.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Physiologically, α-synuclein chaperones soluble NSF attachment protein receptor (SNARE) complex assembly and may also perform other functions; pathologically, in contrast, α-synuclein misfolds into neurotoxic aggregates that mediate neurodegeneration and propagate between neurons. In neurons, α-synuclein exists in an equilibrium between cytosolic and membrane-bound states. Cytosolic α-synuclein appears to be natively unfolded, whereas membrane-bound α-synuclein adopts an α-helical conformation. Although the majority of studies showed that cytosolic α-synuclein is monomeric, it is unknown whether membrane-bound α-synuclein is also monomeric, and whether chaperoning of SNARE complex assembly by α-synuclein involves its cytosolic or membrane-bound state. Here, we show using chemical cross-linking and fluorescence resonance energy transfer (FRET) that α-synuclein multimerizes into large homomeric complexes upon membrane binding. The FRET experiments indicated that the multimers of membrane-bound α-synuclein exhibit defined intermolecular contacts, suggesting an ordered array. Moreover, we demonstrate that α-synuclein promotes SNARE complex assembly at the presynaptic plasma membrane in its multimeric membrane-bound state, but not in its monomeric cytosolic state. Our data delineate a folding pathway for α-synuclein that ranges from a monomeric, natively unfolded form in cytosol to a physiologically functional, multimeric form upon membrane binding, and show that only the latter but not the former acts as a SNARE complex chaperone at the presynaptic terminal, and may protect against neurodegeneration.
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52
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Theillet FX, Binolfi A, Frembgen-Kesner T, Hingorani K, Sarkar M, Kyne C, Li C, Crowley PB, Gierasch L, Pielak GJ, Elcock AH, Gershenson A, Selenko P. Physicochemical properties of cells and their effects on intrinsically disordered proteins (IDPs). Chem Rev 2014; 114:6661-714. [PMID: 24901537 PMCID: PMC4095937 DOI: 10.1021/cr400695p] [Citation(s) in RCA: 338] [Impact Index Per Article: 33.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Indexed: 02/07/2023]
Affiliation(s)
- Francois-Xavier Theillet
- Department
of NMR-supported Structural Biology, In-cell NMR Laboratory, Leibniz Institute of Molecular Pharmacology (FMP Berlin), Robert-Roessle Strasse 10, 13125 Berlin, Germany
| | - Andres Binolfi
- Department
of NMR-supported Structural Biology, In-cell NMR Laboratory, Leibniz Institute of Molecular Pharmacology (FMP Berlin), Robert-Roessle Strasse 10, 13125 Berlin, Germany
| | - Tamara Frembgen-Kesner
- Department
of Biochemistry, University of Iowa, Bowen Science Building, 51 Newton
Road, Iowa City, Iowa 52242, United States
| | - Karan Hingorani
- Departments
of Biochemistry & Molecular Biology and Chemistry, Program in
Molecular & Cellular Biology, University
of Massachusetts, Amherst, 240 Thatcher Way, Amherst, Massachusetts 01003, United States
| | - Mohona Sarkar
- Department
of Chemistry, Department of Biochemistry and Biophysics and Lineberger
Comprehensive Cancer Center, University
of North Carolina, Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Ciara Kyne
- School
of Chemistry, National University of Ireland,
Galway, University Road, Galway, Ireland
| | - Conggang Li
- Key Laboratory
of Magnetic Resonance in Biological Systems, State Key Laboratory
of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center
for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071, P.R. China
| | - Peter B. Crowley
- School
of Chemistry, National University of Ireland,
Galway, University Road, Galway, Ireland
| | - Lila Gierasch
- Departments
of Biochemistry & Molecular Biology and Chemistry, Program in
Molecular & Cellular Biology, University
of Massachusetts, Amherst, 240 Thatcher Way, Amherst, Massachusetts 01003, United States
| | - Gary J. Pielak
- Department
of Chemistry, Department of Biochemistry and Biophysics and Lineberger
Comprehensive Cancer Center, University
of North Carolina, Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Adrian H. Elcock
- Department
of Biochemistry, University of Iowa, Bowen Science Building, 51 Newton
Road, Iowa City, Iowa 52242, United States
| | - Anne Gershenson
- Departments
of Biochemistry & Molecular Biology and Chemistry, Program in
Molecular & Cellular Biology, University
of Massachusetts, Amherst, 240 Thatcher Way, Amherst, Massachusetts 01003, United States
| | - Philipp Selenko
- Department
of NMR-supported Structural Biology, In-cell NMR Laboratory, Leibniz Institute of Molecular Pharmacology (FMP Berlin), Robert-Roessle Strasse 10, 13125 Berlin, Germany
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53
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Direct observation of the three regions in α-synuclein that determine its membrane-bound behaviour. Nat Commun 2014; 5:3827. [PMID: 24871041 PMCID: PMC4046108 DOI: 10.1038/ncomms4827] [Citation(s) in RCA: 322] [Impact Index Per Article: 32.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Accepted: 04/07/2014] [Indexed: 12/22/2022] Open
Abstract
α-synuclein (αS) is a protein involved in neurotransmitter release in presynaptic terminals, and whose aberrant aggregation is associated with Parkinson's disease. In dopaminergic neurons, αS exists in a tightly regulated equilibrium between water-soluble and membrane-associated forms. Here we use a combination of solid-state and solution NMR spectroscopy to characterize the conformations of αS bound to lipid membranes mimicking the composition and physical properties of synaptic vesicles. The study shows three αS regions possessing distinct structural and dynamical properties, including an N-terminal helical segment having a role of membrane anchor, an unstructured C-terminal region that is weakly associated with the membrane and a central region acting as a sensor of the lipid properties and determining the affinity of αS membrane binding. Taken together, our data define the nature of the interactions of αS with biological membranes and provide insights into their roles in the function of this protein and in the molecular processes leading to its aggregation.
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54
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Lokappa SB, Suk JE, Balasubramanian A, Samanta S, Situ AJ, Ulmer TS. Sequence and Membrane Determinants of the Random Coil–Helix Transition of α-Synuclein. J Mol Biol 2014; 426:2130-44. [DOI: 10.1016/j.jmb.2014.02.024] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Revised: 02/24/2014] [Accepted: 02/28/2014] [Indexed: 11/16/2022]
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55
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Investigation of homeodomain membrane translocation properties: insights from the structure determination of engrailed-2 homeodomain in aqueous and membrane-mimetic environments. Biophys J 2014; 105:667-78. [PMID: 23931315 DOI: 10.1016/j.bpj.2013.06.024] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Revised: 06/02/2013] [Accepted: 06/07/2013] [Indexed: 11/21/2022] Open
Abstract
In addition to their well-known DNA-binding properties, homeodomains have the ability to efficiently translocate across biological membranes through still poorly-characterized mechanisms. To date, most biophysical studies addressing the mechanisms of internalization have focused on small synthetic peptides rather than full-length globular homeodomains. In this work, we characterized the conformational properties of chicken Engrailed 2 homeodomain (En2HD) in aqueous solution and in membrane mimetic environments using circular dichroism, Trp fluorescence, and NMR spectroscopy. En2HD adopts a well-defined three-helical bundle fold in aqueous solution. The Trp-48 residue, which is critical for internalization, is fully buried in the hydrophobic core. Circular dichroism and fluorescence reveal that a conformational transition occurs in anionic lipid vesicles and in micelles. En2HD loses its native three-dimensional structure in micellar environments but, remarkably, near-native helical secondary structures are maintained. Long-range interactions could be detected using site-directed spin labels, indicating that the three helices do not adopt extended orientations. Noncovalent paramagnetic probes yielded information about helix positioning and unveiled the burial of critical aromatic and basic residues within the micelles. Our results suggest that electrostatic interactions with membranes may be determinant in inducing a conformational change enabling Trp-48 to insert into membranes.
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56
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Shvadchak VV, Subramaniam V. A four-amino acid linker between repeats in the α-synuclein sequence is important for fibril formation. Biochemistry 2014; 53:279-81. [PMID: 24397337 DOI: 10.1021/bi401427t] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
α-Synuclein is a 140-amino acid protein that can switch conformation among intrinsically disordered in solution, helical on a membrane, and β-sheet in amyloid fibrils. Using the fluorescence of single-tryptophan mutants, we determined the immersion of different regions of the protein into lipid membranes. Our results suggest the presence of a flexible break close to residues 52-55 between two helical domains. The four-amino acid linker is not necessary for membrane binding but is important for fibril formation. A deletion mutant lacking this linker aggregates extremely slowly and slightly inhibits wild-type aggregation, possibly by blocking the growing ends of fibrils.
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Affiliation(s)
- Volodymyr V Shvadchak
- Nanobiophysics, MESA+ Institute for Nanotechnology, and MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente , 7522 NB Enschede, The Netherlands
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57
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Jain N, Bhasne K, Hemaswasthi M, Mukhopadhyay S. Structural and dynamical insights into the membrane-bound α-synuclein. PLoS One 2013; 8:e83752. [PMID: 24376740 PMCID: PMC3869795 DOI: 10.1371/journal.pone.0083752] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Accepted: 11/07/2013] [Indexed: 12/31/2022] Open
Abstract
Membrane-induced disorder-to-helix transition of α-synuclein, a presynaptic protein, has been implicated in a number of important neuronal functions as well as in the etiology of Parkinson’s disease. In order to obtain structural insights of membrane-bound α-synuclein at the residue-specific resolution, we took advantage of the fact that the protein is devoid of tryptophan and incorporated single tryptophan at various residue positions along the sequence. These tryptophans were used as site-specific markers to characterize the structural and dynamical aspects of α-synuclein on the negatively charged small unilamellar lipid vesicles. An array of site-specific fluorescence readouts, such as the spectral-shift, quenching efficiency and anisotropy, allowed us to discern various features of the conformational rearrangements occurring at different locations of α-synuclein on the lipid membrane. In order to define the spatial localization of various regions of the protein near the membrane surface, we utilized a unique and sensitive indicator, namely, red-edge excitation shift (REES), which originates when a fluorophore is located in a highly ordered micro-environment. The extent of REES observed at different residue positions allowed us to directly identify the residues that are localized at the membrane-water interface comprising a thin (∼ 15 Å) layer of motionally restrained water molecules and enabled us to construct a dynamic hydration map of the protein. The combination of site-specific fluorescence readouts allowed us to unravel the intriguing molecular details of α-synuclein on the lipid membrane in a direct model-free fashion. Additionally, the combination of methodologies described here are capable of distinguishing subtle but important structural alterations of α-synuclein bound to different negatively charged lipids with varied head-group chemistry. We believe that the structural modulations of α-synuclein on the membrane could potentially be related to its physiological functions as well as to the onset of Parkinson’s diseases.
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Affiliation(s)
- Neha Jain
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER), Mohali, India
| | - Karishma Bhasne
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER), Mohali, India
| | - M. Hemaswasthi
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER), Mohali, India
| | - Samrat Mukhopadhyay
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER), Mohali, India
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER), Mohali, India
- * E-mail:
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58
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Dikiy I, Eliezer D. N-terminal acetylation stabilizes N-terminal helicity in lipid- and micelle-bound α-synuclein and increases its affinity for physiological membranes. J Biol Chem 2013; 289:3652-65. [PMID: 24338013 DOI: 10.1074/jbc.m113.512459] [Citation(s) in RCA: 149] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The Parkinson disease protein α-synuclein is N-terminally acetylated, but most in vitro studies have been performed using unacetylated α-synuclein. Binding to lipid membranes is considered key to the still poorly understood function of α-synuclein. We report the effects of N-terminal acetylation on α-synuclein binding to lipid vesicles of different composition and curvature and to micelles composed of the detergents β-octyl-glucoside (BOG) and SDS. In the presence of SDS, N-terminal acetylation results in a slightly increased helicity for the N-terminal ~10 residues of the protein, likely due to the stabilization of N-terminal fraying through the formation of a helix cap motif. In the presence of BOG, a detergent used in previous isolations of helical oligomeric forms of α-synuclein, the N-terminally acetylated protein adopts a novel conformation in which the N-terminal ~30 residues bind the detergent micelle in a partly helical conformation, whereas the remainder of the protein remains unbound and disordered. Binding of α-synuclein to lipid vesicles with high negative charge content is essentially unaffected by N-terminal acetylation irrespective of curvature, but binding to vesicles of lower negative charge content is increased, with stronger binding observed for vesicles with higher curvature. Thus, the naturally occurring N-terminally acetylated form of α-synuclein exhibits stabilized helicity at its N terminus and increased affinity for lipid vesicles similar to synaptic vesicles, a binding target of the protein in vivo. Furthermore, the novel BOG-bound state of N-terminally acetylated α-synuclein may serve as a model of partly helical membrane-bound intermediates with a role in α-synuclein function and dysfunction.
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Affiliation(s)
- Igor Dikiy
- From the Department of Biochemistry and Program in Structural Biology, Weill Cornell Medical College, New York, New York 10065
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59
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Albesa-Jové D, Giganti D, Jackson M, Alzari PM, Guerin ME. Structure-function relationships of membrane-associated GT-B glycosyltransferases. Glycobiology 2013; 24:108-24. [PMID: 24253765 DOI: 10.1093/glycob/cwt101] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Membrane-associated GT-B glycosyltransferases (GTs) comprise a large family of enzymes that catalyze the transfer of a sugar moiety from nucleotide-sugar donors to a wide range of membrane-associated acceptor substrates, mostly in the form of lipids and proteins. As a consequence, they generate a significant and diverse amount of glycoconjugates in biological membranes, which are particularly important in cell-cell, cell-matrix and host-pathogen recognition events. Membrane-associated GT-B enzymes display two "Rossmann-fold" domains separated by a deep cleft that includes the catalytic center. They associate permanently or temporarily to the phospholipid bilayer by a combination of hydrophobic and electrostatic interactions. They have the remarkable property to access both hydrophobic and hydrophilic substrates that reside within chemically distinct environments catalyzing their enzymatic transformations in an efficient manner. Here, we discuss the considerable progress that has been made in recent years in understanding the molecular mechanism that governs substrate and membrane recognition, and the impact of the conformational transitions undergone by these GTs during the catalytic cycle.
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Affiliation(s)
- David Albesa-Jové
- Unidad de Biofísica, Centro Mixto Consejo Superior de Investigaciones Científicas - Universidad del País Vasco/Euskal Herriko Unibertsitatea (CSIC, UPV/EHU), Barrio Sarriena s/n, Leioa, Bizkaia 48940, Spain
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60
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Hoffman-Zacharska D, Koziorowski D, Ross OA, Milewski M1, Poznanski J1A, Jurek M, Wszolek ZK, Soto-Ortolaza A, awek J1AS1, Janik P, Jamrozik Z, Potulska-Chromik A, Jasinska-Myga B, Opala G, Krygowska-Wajs A, Czyzewski K, Dickson DW, Bal J, Friedman A. Novel A18T and pA29S substitutions in α-synuclein may be associated with sporadic Parkinson's disease. Parkinsonism Relat Disord 2013; 19:1057-1060. [PMID: 23916651 PMCID: PMC4055791 DOI: 10.1016/j.parkreldis.2013.07.011] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Revised: 06/20/2013] [Accepted: 07/13/2013] [Indexed: 11/17/2022]
Abstract
OBJECTIVE Mutations in the α-synuclein-encoding gene SNCA are considered as a rare cause of Parkinson's disease (PD). Our objective was to examine the frequency of the SNCA point mutations among PD patients of Polish origin. METHODS Detection of the known SNCA point mutations A30P (c.88G>C), E46K (c.136G>A) and A53T (c.157A>T) was performed either using the Sequenom MassArray iPLEX platform or by direct sequencing of the SNCA exons 2 and 3. As the two novel substitutions A18T (c.52G>A) and A29S (c.85G>T) were identified, their frequency in a control population of Polish origin was assessed and in silico analysis performed to investigate the potential impact on protein structure and function. RESULTS We did not observe the previously reported point mutations in the SNCA gene in our 629 PD patients; however, two novel potentially pathogenic substitutions A18T and A29S were identified. Each variant was observed in a single patient presenting with a typical late-onset sporadic PD phenotype. Although neither variant was observed in control subjects and in silico protein analysis predicts a damaging effect for A18T and pA29S substitutions, the lack of family history brings into question the true pathogenicity of these rare variants. CONCLUSIONS Larger population based studies are needed to determine the pathogenicity of the A18T and A29S substitutions. Our findings highlight the possible role of rare variants contributing to disease risk and may support further screening of the SNCA gene in sporadic PD patients from different populations.
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Affiliation(s)
- Dorota Hoffman-Zacharska
- Department of Medical Genetics, Institute of Mother and Child, Warsaw, Poland
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Poland
| | - Dariusz Koziorowski
- Department of Neurology, Faculty of Health Science, Medical University of Warsaw, Poland
| | - Owen A. Ross
- Department of Neuroscience, Mayo Clinic Florida, Jacksonville, USA
| | - Micha 1 Milewski
- Department of Medical Genetics, Institute of Mother and Child, Warsaw, Poland
| | - Jaros 1 aw Poznanski
- Department of Biophysics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - Marta Jurek
- Department of Medical Genetics, Institute of Mother and Child, Warsaw, Poland
| | | | | | - Jaros 1 aw S 1 awek
- Department of Neurological and Psychiatric Nursing, Medical University, Gdansk, Poland
- Department of Neurology, St. Albert Hospital, Gdansk, Poland
| | - Piotr Janik
- Department of Neurology, Medical University of Warsaw, Poland
| | | | | | | | - Grzegorz Opala
- Department of Neurology, Medical University of Silesia, Katowice, Poland
| | - Anna Krygowska-Wajs
- Department of Neurology, Collegium Medicum Jagiellonian University, Krakow, Poland
| | - Krzysztof Czyzewski
- Department of Neurology, Central Hospital of the Ministry of Interior and Administration, Warsaw, Poland
| | | | - Jerzy Bal
- Department of Medical Genetics, Institute of Mother and Child, Warsaw, Poland
| | - Andrzej Friedman
- Department of Neurology, Faculty of Health Science, Medical University of Warsaw, Poland
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61
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Hydration dynamics as an intrinsic ruler for refining protein structure at lipid membrane interfaces. Proc Natl Acad Sci U S A 2013; 110:16838-43. [PMID: 24082088 DOI: 10.1073/pnas.1307678110] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Knowing the topology and location of protein segments at water-membrane interfaces is critical for rationalizing their functions, but their characterization is challenging under physiological conditions. Here, we debut a unique spectroscopic approach by using the hydration dynamics gradient found across the phospholipid bilayer as an intrinsic ruler for determining the topology, immersion depth, and orientation of protein segments in lipid membranes, particularly at water-membrane interfaces. This is achieved through the site-specific quantification of translational diffusion of hydration water using an emerging tool, (1)H Overhauser dynamic nuclear polarization (ODNP)-enhanced NMR relaxometry. ODNP confirms that the membrane-bound region of α-synuclein (αS), an amyloid protein known to insert an amphipathic α-helix into negatively charged phospholipid membranes, forms an extended α-helix parallel to the membrane surface. We extend the current knowledge by showing that residues 90-96 of bound αS, which is a transition segment that links the α-helix and the C terminus, adopt a larger loop than an idealized α-helix. The unstructured C terminus gradually threads through the surface hydration layers of lipid membranes, with the beginning portion residing within 5-15 Å above the phosphate level, and only the very end of C terminus surveying bulk water. Remarkably, the intrinsic hydration dynamics gradient along the bilayer normal extends to 20-30 Å above the phosphate level, as demonstrated with a peripheral membrane protein, annexin B12. ODNP offers the opportunity to reveal previously unresolvable structure and location of protein segments well above the lipid phosphate, whose structure and dynamics critically contribute to the understanding of functional versatility of membrane proteins.
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62
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Mazumder P, Suk JE, Ulmer TS. Insight into α-synuclein plasticity and misfolding from differential micelle binding. J Phys Chem B 2013; 117:11448-59. [PMID: 23978162 DOI: 10.1021/jp402589x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Misfolded species of the 140-residue protein α-synuclein (αS) are implicated in the demise of dopaminergic neurons, resulting in fatal neurodegeneration. The intrinsically unstructured protein binds curved synaptic vesicle membranes in helical conformations but misfolds into amyloid fibrils via β-sheet interactions. Breaks in helical αS conformation may offer a pathway to transition from helical to sheet conformation. Here, we explore the evolution of broken αS helix conformations formed in complex with SDS and SLAS micelles by molecular dynamics simulations. The population distribution of experimentally observed αS conformations is related to the spatial concentration of intrinsic micelle shape perturbations. For the success of micelle-induced αS folding, we posit the length of the first helical segment formed, which controls micelle ellipticity, to be a key determinant. The degree of micelle curvature relates to the arrangement and segmental motions of helical secondary structure elements. A criterion for assessing the reproduction of such intermediate time scale protein dynamics is introduced by comparing the sampling of experimental and simulated spin label distributions. Finally, at the sites of breaks in the elongated, marginally stable αS helix, vulnerability to forming a transient, intramolecular β-sheet is identified. Upon subsequent intermolecular β-sheet pairing, pathological αS amyloid formation from initial helical conformation is thus achievable.
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Affiliation(s)
- Parichita Mazumder
- Department of Biochemistry & Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California , 1501 San Pablo Street, Los Angeles, California 90033, United States
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63
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Wietek J, Haralampiev I, Amoussouvi A, Herrmann A, Stöckl M. Membrane bound α-synuclein is fully embedded in the lipid bilayer while segments with higher flexibility remain. FEBS Lett 2013; 587:2572-7. [PMID: 23831067 DOI: 10.1016/j.febslet.2013.06.034] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Revised: 05/28/2013] [Accepted: 06/25/2013] [Indexed: 12/15/2022]
Abstract
Cellular pathways involving α-synuclein (αS) seem to be causative for development of Parkinson's disease. Interactions between αS and lipid membranes appear to be important for the physiological function of the protein and influence the pathological aggregation of αS leading to the formation of amyloid plaques. Upon membrane binding the unstructured αS folds into amphipathic helices. In our work we characterized the penetration depth and probed the local environment of Trp-residues introduced along the αS sequence. We could show that while the entire helix is well embedded in the lipid bilayer, segments with a shallower penetration and supposable higher flexibility exist.
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Affiliation(s)
- Jonas Wietek
- Department of Biology, Faculty of Mathematics and Natural Sciences I, Humboldt University Berlin, Invalidenstr. 42, 10115 Berlin, Germany
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64
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Burré J, Vivona S, Diao J, Sharma M, Brunger AT, Südhof TC. Properties of native brain α-synuclein. Nature 2013; 498:E4-6; discussion E6-7. [PMID: 23765500 PMCID: PMC4255827 DOI: 10.1038/nature12125] [Citation(s) in RCA: 253] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Accepted: 03/28/2013] [Indexed: 12/19/2022]
Affiliation(s)
- Jacqueline Burré
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California 94305, USA
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65
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Diao J, Burré J, Vivona S, Cipriano DJ, Sharma M, Kyoung M, Südhof TC, Brunger AT. Native α-synuclein induces clustering of synaptic-vesicle mimics via binding to phospholipids and synaptobrevin-2/VAMP2. eLife 2013; 2:e00592. [PMID: 23638301 PMCID: PMC3639508 DOI: 10.7554/elife.00592] [Citation(s) in RCA: 241] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 03/25/2013] [Indexed: 12/13/2022] Open
Abstract
α-Synuclein is a presynaptic protein that is implicated in Parkinson's and other neurodegenerative diseases. Physiologically, native α-synuclein promotes presynaptic SNARE-complex assembly, but its molecular mechanism of action remains unknown. Here, we found that native α-synuclein promotes clustering of synaptic-vesicle mimics, using a single-vesicle optical microscopy system. This vesicle-clustering activity was observed for both recombinant and native α-synuclein purified from mouse brain. Clustering was dependent on specific interactions of native α-synuclein with both synaptobrevin-2/VAMP2 and anionic lipids. Out of the three familial Parkinson's disease-related point mutants of α-synuclein, only the lipid-binding deficient mutation A30P disrupted clustering, hinting at a possible loss of function phenotype for this mutant. α-Synuclein had little effect on Ca(2+)-triggered fusion in our reconstituted single-vesicle system, consistent with in vivo data. α-Synuclein may therefore lead to accumulation of synaptic vesicles at the active zone, providing a 'buffer' of synaptic vesicles, without affecting neurotransmitter release itself. DOI:http://dx.doi.org/10.7554/eLife.00592.001.
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Affiliation(s)
- Jiajie Diao
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States
- Department of Structural Biology, Stanford University, Stanford, United States
- Departments of Photon Sciences, and Neurology and Neurological Sciences, Stanford University, Stanford, United States
- Howard Hughes Medical Institute, Stanford University, Stanford, United States
| | - Jacqueline Burré
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States
| | - Sandro Vivona
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States
- Department of Structural Biology, Stanford University, Stanford, United States
- Departments of Photon Sciences, and Neurology and Neurological Sciences, Stanford University, Stanford, United States
- Howard Hughes Medical Institute, Stanford University, Stanford, United States
| | - Daniel J Cipriano
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States
- Department of Structural Biology, Stanford University, Stanford, United States
- Departments of Photon Sciences, and Neurology and Neurological Sciences, Stanford University, Stanford, United States
- Howard Hughes Medical Institute, Stanford University, Stanford, United States
| | - Manu Sharma
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States
| | - Minjoung Kyoung
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States
- Department of Structural Biology, Stanford University, Stanford, United States
- Departments of Photon Sciences, and Neurology and Neurological Sciences, Stanford University, Stanford, United States
- Howard Hughes Medical Institute, Stanford University, Stanford, United States
| | - Thomas C Südhof
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States
- Howard Hughes Medical Institute, Stanford University, Stanford, United States
- For correspondence: (TCS)
| | - Axel T Brunger
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States
- Department of Structural Biology, Stanford University, Stanford, United States
- Departments of Photon Sciences, and Neurology and Neurological Sciences, Stanford University, Stanford, United States
- Howard Hughes Medical Institute, Stanford University, Stanford, United States
- For correspondence: (ATB)
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66
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Varkey J, Mizuno N, Hegde BG, Cheng N, Steven AC, Langen R. α-Synuclein oligomers with broken helical conformation form lipoprotein nanoparticles. J Biol Chem 2013; 288:17620-30. [PMID: 23609437 DOI: 10.1074/jbc.m113.476697] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
α-Synuclein (αS) is a membrane-binding protein with sequence similarity to apolipoproteins and other lipid-carrying proteins, which are capable of forming lipid-containing nanoparticles, sometimes referred to as "discs." Previously, it has been unclear whether αS also possesses this property. Using cryo-electron microscopy and light scattering, we found that αS can remodel phosphatidylglycerol vesicles into nanoparticles whose shape (ellipsoidal) and dimensions (in the 7-10-nm range) resemble those formed by apolipoproteins. The molar ratio of αS to lipid in nanoparticles is ∼1:20, and αS is oligomeric (including trimers and tetramers). Similar nanoparticles form when αS is added to vesicles of mitochondrial lipids. This observation suggests a mechanism for the previously reported disruption of mitochondrial membranes by αS. Circular dichroism and four-pulse double electron electron resonance experiments revealed that in nanoparticles αS assumes a broken helical conformation distinct from the extended helical conformation adopted when αS is bound to intact vesicles or membrane tubules. We also observed αS-dependent tubule and nanoparticle formation in the presence of oleic acid, implying that αS can interact with fatty acids and lipids in a similar manner. αS-related nanoparticles might play a role in lipid and fatty acid transport functions previously attributed to this protein.
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Affiliation(s)
- Jobin Varkey
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California 90033, USA
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67
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Abstract
Parkinson's disease is one of the most frequent progressive degenerative disorders with unknown origin of the nervous system. The commutation of the disease on Guam led to the discovery of a neurotoxin which was also found in other continents. This neurotoxin was identified in the common cyanobacteria (blue-green algae). Early clinical observations suggested some loose correlations with gastric and duodenal ulcer and Parkinson's disease, while recent studies revealed a toxin, almost identical to that found in cyanobacteria in one strain of Helicobacter pylori, which proved to cause Parkinson like symptoms in animals. Therefore, it cannot be ruled out that there is a slowly progressive poisoning in Parkinson's disease. The disease specific alpha-sinuclein inclusions can be found in nerve cells of the intestinal mucosa far before the appearance of clinical symptoms indicating that the disease may start in the intestines. These results are strengthened by the results of Borody's fecal transplants, after which in Parkinson patients showed a symptomatic improvement. Based on these observations the Parkinson puzzle is getting complete. Although these observations are not evidence based, they may indicate a new way for basic clinical research, as well as a new way of thinking for clinicians. These new observations in psycho-neuro-immunology strengthen the fact that immunological factors may also play a critical factor facilitating local cell necrosis which may be influenced easily.
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Affiliation(s)
- András Guseo
- Fejér Megyei Szent György Kórház Idegosztály Székesfehérvár Cserkész u.
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68
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Yap TL, Velayati A, Sidransky E, Lee JC. Membrane-bound α-synuclein interacts with glucocerebrosidase and inhibits enzyme activity. Mol Genet Metab 2013; 108:56-64. [PMID: 23266198 PMCID: PMC3552326 DOI: 10.1016/j.ymgme.2012.11.010] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Accepted: 11/15/2012] [Indexed: 01/31/2023]
Abstract
Mutations in GBA, the gene encoding glucocerebrosidase, the lysosomal enzyme deficient in Gaucher disease increase the risk for developing Parkinson disease. Recent research suggests a relationship between glucocerebrosidase and the Parkinson disease-related amyloid-forming protein, α-synuclein; however, the specific molecular mechanisms responsible for association remain elusive. Previously, we showed that α-synuclein and glucocerebrosidase interact selectively under lysosomal conditions, and proposed that this newly identified interaction might influence cellular levels of α-synuclein by either promoting protein degradation and/or preventing aggregation. Here, we demonstrate that membrane-bound α-synuclein interacts with glucocerebrosidase, and that this complex formation inhibits enzyme function. Using site-specific fluorescence and Förster energy transfer probes, we mapped the protein-enzyme interacting regions on unilamellar vesicles. Our data suggest that on the membrane surface, the glucocerebrosidase-α-synuclein interaction involves a larger α-synuclein region compared to that found in solution. In addition, α-synuclein acts as a mixed inhibitor with an apparent IC(50) in the submicromolar range. Importantly, the membrane-bound, α-helical form of α-synuclein is necessary for inhibition. This glucocerebrosidase interaction and inhibition likely contribute to the mechanism underlying GBA-associated parkinsonism.
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Affiliation(s)
- Thai Leong Yap
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Arash Velayati
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Ellen Sidransky
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States
- Corresponding authors. Ellen Sidransky, 35 Convent Drive, Room 1A213, Bethesda, MD, 20892. Fax: +1-301-402-6438. Jennifer C. Lee, 50 South Drive, Room 3513, Bethesda, MD, 20892. Fax: +1-301-402-3404. and
| | - Jennifer C. Lee
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States
- Corresponding authors. Ellen Sidransky, 35 Convent Drive, Room 1A213, Bethesda, MD, 20892. Fax: +1-301-402-6438. Jennifer C. Lee, 50 South Drive, Room 3513, Bethesda, MD, 20892. Fax: +1-301-402-3404. and
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69
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Burré J, Sharma M, Südhof TC. Systematic mutagenesis of α-synuclein reveals distinct sequence requirements for physiological and pathological activities. J Neurosci 2012; 32:15227-42. [PMID: 23100443 PMCID: PMC3506191 DOI: 10.1523/jneurosci.3545-12.2012] [Citation(s) in RCA: 125] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Revised: 08/20/2012] [Accepted: 09/02/2012] [Indexed: 12/22/2022] Open
Abstract
α-Synuclein is an abundant presynaptic protein that binds to phospholipids and synaptic vesicles. Physiologically, α-synuclein functions as a SNARE-protein chaperone that promotes SNARE-complex assembly for neurotransmitter release. Pathologically, α-synuclein mutations and α-synuclein overexpression cause Parkinson's disease, and aggregates of α-synuclein are found as Lewy bodies in multiple neurodegenerative disorders ("synucleinopathies"). The relation of the physiological functions to the pathological effects of α-synuclein remains unclear. As an initial avenue of addressing this question, we here systematically examined the effect of α-synuclein mutations on its physiological and pathological activities. We generated 26 α-synuclein mutants spanning the entire molecule, and analyzed them compared with wild-type α-synuclein in seven assays that range from biochemical studies with purified α-synuclein, to analyses of α-synuclein expression in cultured neurons, to examinations of the effects of virally expressed α-synuclein introduced into the mouse substantia nigra by stereotactic injections. We found that both the N-terminal and C-terminal sequences of α-synuclein were required for its physiological function as SNARE-complex chaperone, but that these sequences were not essential for its neuropathological effects. In contrast, point mutations in the central region of α-synuclein, referred to as nonamyloid β component (residues 61-95), as well as point mutations linked to Parkinson's disease (A30P, E46K, and A53T) increased the neurotoxicity of α-synuclein but did not affect its physiological function in SNARE-complex assembly. Thus, our data show that the physiological function of α-synuclein, although protective of neurodegeneration in some contexts, is fundamentally distinct from its neuropathological effects, thereby dissociating the two activities of α-synuclein.
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Affiliation(s)
- Jacqueline Burré
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, California 94305-5453, and
| | - Manu Sharma
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, California 94305-5453, and
| | - Thomas C. Südhof
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, California 94305-5453, and
- Howard Hughes Medical Institute, Stanford University, Stanford, California 94305-5453
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70
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Ding Z, Taneva SG, Huang HKH, Campbell SA, Semenec L, Chen N, Cornell RB. A 22-mer segment in the structurally pliable regulatory domain of metazoan CTP: phosphocholine cytidylyltransferase facilitates both silencing and activating functions. J Biol Chem 2012; 287:38980-91. [PMID: 22988242 DOI: 10.1074/jbc.m112.402081] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
CTP:phosphocholine cytidylyltransferase (CCT), an amphitropic enzyme that regulates phosphatidylcholine synthesis, is composed of a catalytic head domain and a regulatory tail. The tail region has dual functions as a regulator of membrane binding/enzyme activation and as an inhibitor of catalysis in the unbound form of the enzyme, suggesting conformational plasticity. These functions are well conserved in CCTs across diverse phyla, although the sequences of the tail regions are not. CCT regulatory tails of diverse origins are composed of a long membrane lipid-inducible amphipathic helix (m-AH) followed by a highly disordered segment, reminiscent of the Parkinson disease-linked protein, α-synuclein, which we show shares a novel sequence motif with vertebrate CCTs. To unravel features required for silencing, we created chimeric enzymes by fusing the catalytic domain of rat CCTα to the regulatory tail of CCTs from Drosophila, Caenorhabditis elegans, or Saccharomyces cerevisiae or to α-synuclein. Only the tail domains of the two invertebrate CCTs were competent for both suppression of catalytic activity and for activation by lipid vesicles. Thus, both silencing and activating functions of the m-AH can tolerate significant changes in length and sequence. We identified a highly amphipathic 22-residue segment in the m-AH with features conserved among animal CCTs but not yeast CCT or α-synuclein. Deletion of this segment from rat CCT increased the lipid-independent V(max) by 10-fold, equivalent to the effect of deleting the entire tail, and severely weakened membrane binding affinity. However, membrane binding was required for additional increases in catalytic efficiency. Thus, full activation of CCT may require not only loss of a silencing conformation in the m-AH but a gain of an activating conformation, promoted by membrane binding.
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Affiliation(s)
- Ziwei Ding
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
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71
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Mizuno N, Varkey J, Kegulian NC, Hegde BG, Cheng N, Langen R, Steven AC. Remodeling of lipid vesicles into cylindrical micelles by α-synuclein in an extended α-helical conformation. J Biol Chem 2012; 287:29301-11. [PMID: 22767608 DOI: 10.1074/jbc.m112.365817] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
α-Synuclein (αS) is a protein with multiple conformations and interactions. Natively unfolded in solution, αS accumulates as amyloid in neurological tissue in Parkinson disease and interacts with membranes under both physiological and pathological conditions. Here, we used cryoelectron microscopy in conjunction with electron paramagnetic resonance (EPR) and other techniques to characterize the ability of αS to remodel vesicles. At molar ratios of 1:5 to 1:40 for protein/lipid (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol), large spherical vesicles are converted into cylindrical micelles ~50 Å in diameter. Other lipids of the same charge (negative) exhibit generally similar behavior, although bilayer tubes of 150-500 Å in width are also produced, depending on the lipid acyl chains. At higher protein/lipid ratios, discoid particles, 70-100 Å across, are formed. EPR data show that, on cylindrical micelles, αS adopts an extended amphipathic α-helical conformation, with its long axis aligned with the tube axis. The observed geometrical relationship between αS and the micelle suggests that the wedging of its long α-helix into the outer leaflet of a membrane may cause curvature and an anisotropic partition of lipids, leading to tube formation.
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Affiliation(s)
- Naoko Mizuno
- Laboratory of Structural Biology, NIAMS, National Institutes of Health, Bethesda, MD 20892, USA.
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72
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Tavassoly O, Lee JS. Methamphetamine binds to α-synuclein and causes a conformational change which can be detected by nanopore analysis. FEBS Lett 2012; 586:3222-8. [DOI: 10.1016/j.febslet.2012.06.040] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Revised: 06/06/2012] [Accepted: 06/25/2012] [Indexed: 01/14/2023]
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73
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Maltsev AS, Ying J, Bax A. Impact of N-terminal acetylation of α-synuclein on its random coil and lipid binding properties. Biochemistry 2012; 51:5004-13. [PMID: 22694188 PMCID: PMC3383124 DOI: 10.1021/bi300642h] [Citation(s) in RCA: 167] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
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N-Terminal acetylation of α-synuclein (aS), a protein
implicated
in the etiology of Parkinson’s disease, is common in mammals.
The impact of this modification on the protein’s structure
and dynamics in free solution and on its membrane binding properties
has been evaluated by high-resolution nuclear magnetic resonance and
circular dichroism (CD) spectroscopy. While no tetrameric form of
acetylated aS could be isolated, N-terminal acetylation resulted in
chemical shift perturbations of the first 12 residues of the protein
that progressively decreased with the distance from the N-terminus.
The directions of the chemical shift changes and small changes in
backbone 3JHH couplings are
consistent with an increase in the α-helicity of the first six
residues of aS, although a high degree of dynamic conformational disorder
remains and the helical structure is sampled <20% of the time.
Chemical shift and 3JHH data
for the intact protein are virtually indistinguishable from those
recorded for the corresponding N-terminally acetylated and nonacetylated
15-residue synthetic peptides. An increase in α-helicity at
the N-terminus of aS is supported by CD data on the acetylated peptide
and by weak medium-range nuclear Overhauser effect contacts indicative
of α-helical character. The remainder of the protein has chemical
shift values that are very close to random coil values and indistinguishable
between the two forms of the protein. No significant differences in
the fibrillation kinetics were observed between acetylated and nonacetylated
aS. However, the lipid binding properties of aS are strongly impacted
by acetylation and exhibit distinct behavior for the first 12 residues,
indicative of an initiation role for the N-terminal residues in an
“initiation–elongation” process of binding to
the membrane.
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Affiliation(s)
- Alexander S Maltsev
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0520, USA
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74
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Suk JE, Situ AJ, Ulmer TS. Construction of covalent membrane protein complexes and high-throughput selection of membrane mimics. J Am Chem Soc 2012; 134:9030-3. [PMID: 22626249 PMCID: PMC3415561 DOI: 10.1021/ja304247f] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The association of transmembrane (TM) helices underlies membrane protein structure and folding. Structural studies of TM complexes are limited by complex stability and the often time-consuming selection of suitable membrane mimics. Here, methodology for the efficient, preparative scale construction of covalent TM complexes and the concomitant high-throughput selection of membrane mimics is introduced. For the employed integrin αIIbβ3 model system, the methodology identified phospholipid bicelles, including their specific composition, as the best membrane mimic. The method facilitates structure determination by NMR spectroscopy as exemplified by the measurement of previously inaccessible residual dipolar couplings and (15)N relaxation parameters.
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Affiliation(s)
- Jae-Eun Suk
- Department of Biochemistry & Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, 1501 San Pablo Street, Los Angeles, California 90033, United States
| | - Alan J. Situ
- Department of Biochemistry & Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, 1501 San Pablo Street, Los Angeles, California 90033, United States
| | - Tobias S. Ulmer
- Department of Biochemistry & Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, 1501 San Pablo Street, Los Angeles, California 90033, United States
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75
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Shvadchak VV, Yushchenko DA, Pievo R, Jovin TM. The mode of α-synuclein binding to membranes depends on lipid composition and lipid to protein ratio. FEBS Lett 2011; 585:3513-9. [PMID: 22004764 DOI: 10.1016/j.febslet.2011.10.006] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Revised: 10/01/2011] [Accepted: 10/03/2011] [Indexed: 11/28/2022]
Abstract
Interactions of the presynaptic protein α-synuclein with membranes are involved in its physiological action as well as in the pathological misfolding and aggregation related to Parkinsons's disease. We studied the conformation and orientation of α-synuclein bound to model vesicular membranes using multiparametric response polarity-sensitive fluorescent probes together with CD and EPR measurements. At low lipid to α-synuclein ratio the protein binds membranes through its N-terminal domain. When lipids are in excess, the α-helical content and the role of the C-terminus in binding increase. Highly rigid membranes also induce a greater α-helical content and a lower polarity of the protein microenvironment.
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Affiliation(s)
- Volodymyr V Shvadchak
- Laboratory of Cellular Dynamics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
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76
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Breydo L, Wu JW, Uversky VN. Α-synuclein misfolding and Parkinson's disease. Biochim Biophys Acta Mol Basis Dis 2011; 1822:261-85. [PMID: 22024360 DOI: 10.1016/j.bbadis.2011.10.002] [Citation(s) in RCA: 454] [Impact Index Per Article: 34.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Revised: 08/26/2011] [Accepted: 10/03/2011] [Indexed: 12/21/2022]
Abstract
Substantial evidence links α-synuclein, a small highly conserved presynaptic protein with unknown function, to both familial and sporadic Parkinson's disease (PD). α-Synuclein has been identified as the major component of Lewy bodies and Lewy neurites, the characteristic proteinaceous deposits that are the hallmarks of PD. α-Synuclein is a typical intrinsically disordered protein, but can adopt a number of different conformational states depending on conditions and cofactors. These include the helical membrane-bound form, a partially-folded state that is a key intermediate in aggregation and fibrillation, various oligomeric species, and fibrillar and amorphous aggregates. The molecular basis of PD appears to be tightly coupled to the aggregation of α-synuclein and the factors that affect its conformation. This review examines the different aggregation states of α-synuclein, the molecular mechanism of its aggregation, and the influence of environmental and genetic factors on this process.
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Affiliation(s)
- Leonid Breydo
- Department of Molecular Medicine, College of Medicine, University of South Florida, Tampa, FL 33612, USA
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77
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Rao JN, Warren GZL, Estolt-Povedano S, Zammit VA, Ulmer TS. An environment-dependent structural switch underlies the regulation of carnitine palmitoyltransferase 1A. J Biol Chem 2011; 286:42545-42554. [PMID: 21990363 DOI: 10.1074/jbc.m111.306951] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The enzyme carnitine palmitoyltransferase 1 (CPT1), which is anchored in the outer mitochondrial membrane (OMM), controls the rate-limiting step in fatty acid β-oxidation in mammalian tissues. It is inhibited by malonyl-CoA, the first intermediate of fatty acid synthesis, and it responds to OMM curvature and lipid characteristics, which reflect long term nutrient/hormone availability. Here, we show that the N-terminal regulatory domain (N) of CPT1A can adopt two complex amphiphilic structural states, termed Nα and Nβ, that interchange in a switch-like manner in response to offered binding surface curvature. Structure-based site-directed mutageneses of native CPT1A suggest Nα to be inhibitory and Nβ to be noninhibitory, with the relative Nα/Nβ ratio setting the prevalent malonyl-CoA sensitivity of the enzyme. Based on the amphiphilic nature of N and molecular modeling, we propose malonyl-CoA sensitivity to be coupled to the properties of the OMM by Nα-OMM associations that alter the Nα/Nβ ratio. For enzymes residing at the membrane-water interface, this constitutes an integrative regulatory mechanism of exceptional sophistication.
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Affiliation(s)
- Jampani N Rao
- Department of Biochemistry and Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - Gemma Z L Warren
- Metabolic and Vascular Health Division, Warwick Medical School, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom
| | - Sara Estolt-Povedano
- Metabolic and Vascular Health Division, Warwick Medical School, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom
| | - Victor A Zammit
- Metabolic and Vascular Health Division, Warwick Medical School, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom
| | - Tobias S Ulmer
- Department of Biochemistry and Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033.
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78
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Dikiy I, Eliezer D. Folding and misfolding of alpha-synuclein on membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:1013-8. [PMID: 21945884 DOI: 10.1016/j.bbamem.2011.09.008] [Citation(s) in RCA: 146] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Revised: 09/09/2011] [Accepted: 09/12/2011] [Indexed: 12/23/2022]
Abstract
The protein alpha-synuclein is considered to play a major role in the etiology of Parkinson's disease. Because it is found in a classic amyloid fibril form within the characteristic intra-neuronal Lewy body deposits of the disease, aggregation of the protein is thought to be of critical importance, but the context in which the protein undergoes aggregation within cells remains unknown. The normal function of synucleins is poorly understood, but appears to involve membrane interactions, and in particular reversible binding to synaptic vesicle membranes. Structural studies of different states of alpha-synuclein, in the absence and presence of membranes or membrane mimetics, have led to models of how membrane-bound forms of the protein may contribute both to functional properties of the protein, as well as to membrane-induced self-assembly and aggregation. This article reviews this area, with a focus on a particular model that has emerged in the past few years. This article is part of a Special Issue entitled: Protein Folding in Membranes.
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Affiliation(s)
- Igor Dikiy
- Department of Biochemistry and Program in Structural Biology, Weill Cornell Medical College, New York, NY 10065, USA
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