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Impact of membrane lipid composition on the structure and stability of the transmembrane domain of amyloid precursor protein. Proc Natl Acad Sci U S A 2016; 113:E5281-7. [PMID: 27559086 DOI: 10.1073/pnas.1606482113] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cleavage of the amyloid precursor protein (APP) by γ-secretase is a crucial first step in the evolution of Alzheimer's disease. To discover the cleavage mechanism, it is urgent to predict the structures of APP monomers and dimers in varying membrane environments. We determined the structures of the C9923-55 monomer and homodimer as a function of membrane lipid composition using a multiscale simulation approach that blends atomistic and coarse-grained models. We demonstrate that the C9923-55 homodimer structures form a heterogeneous ensemble with multiple conformational states, each stabilized by characteristic interpeptide interactions. The relative probabilities of each conformational state are sensitive to the membrane environment, leading to substantial variation in homodimer peptide structure as a function of membrane lipid composition or the presence of an anionic lipid environment. In contrast, the helicity of the transmembrane domain of monomeric C991-55 is relatively insensitive to the membrane lipid composition, in agreement with experimental observations. The dimer structures of human EphA2 receptor depend on the lipid environment, which we show is linked to the location of the structural motifs in the dimer interface, thereby establishing that both sequence and membrane composition modulate the complete energy landscape of membrane-bound proteins. As a by-product of our work, we explain the discrepancy in structures predicted for C99 congener homodimers in membrane and micelle environments. Our study provides insight into the observed dependence of C99 protein cleavage by γ-secretase, critical to the formation of amyloid-β protein, on membrane thickness and lipid composition.
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52
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Xu TH, Yan Y, Kang Y, Jiang Y, Melcher K, Xu HE. Alzheimer's disease-associated mutations increase amyloid precursor protein resistance to γ-secretase cleavage and the Aβ42/Aβ40 ratio. Cell Discov 2016; 2:16026. [PMID: 27625790 PMCID: PMC4994064 DOI: 10.1038/celldisc.2016.26] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2016] [Accepted: 06/22/2016] [Indexed: 12/24/2022] Open
Abstract
Mutations in the amyloid precursor protein (APP) gene and the aberrant cleavage of APP by γ-secretase are associated with Alzheimer's disease (AD). Here we have developed a simple and sensitive cell-based assay to detect APP cleavage by γ-secretase. Unexpectedly, most familial AD (FAD)-linked APP mutations make APP partially resistant to γ-secretase. Mutations that alter residues N terminal to the γ-secretase cleavage site Aβ42 have subtle effects on cleavage efficiency and cleavage-site selectivity. In contrast, mutations that alter residues C terminal to the Aβ42 site reduce cleavage efficiency and dramatically shift cleavage-site specificity toward the aggregation-prone Aβ42. Moreover, mutations that remove positive charge at residue 53 greatly reduce the APP cleavage by γ-secretase. These results suggest a model of γ-secretase substrate recognition, in which the APP region C terminal to the Aβ42 site and the positively charged residue at position 53 are the primary determinants for substrate binding and cleavage-site selectivity. We further demonstrate that this model can be extended to γ-secretase processing of notch receptors, a family of highly conserved cell-surface signaling proteins.
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Affiliation(s)
- Ting-Hai Xu
- Key Laboratory of Receptor Research, VARI-SIMM Center, Center for Structure and Function of Drug Targets, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China; Laboratory of Structural Sciences and Laboratory of Structural Biology and Biochemistry, Van Andel Research Institute, Grand Rapids, MI, USA; University of Chinese Academy of Sciences, Beijing, China
| | - Yan Yan
- Key Laboratory of Receptor Research, VARI-SIMM Center, Center for Structure and Function of Drug Targets, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China; Laboratory of Structural Sciences and Laboratory of Structural Biology and Biochemistry, Van Andel Research Institute, Grand Rapids, MI, USA; University of Chinese Academy of Sciences, Beijing, China
| | - Yanyong Kang
- Laboratory of Structural Sciences and Laboratory of Structural Biology and Biochemistry, Van Andel Research Institute , Grand Rapids, MI, USA
| | - Yi Jiang
- Key Laboratory of Receptor Research, VARI-SIMM Center, Center for Structure and Function of Drug Targets, Shanghai Institute of Materia Medica, Chinese Academy of Sciences , Shanghai, China
| | - Karsten Melcher
- Laboratory of Structural Sciences and Laboratory of Structural Biology and Biochemistry, Van Andel Research Institute , Grand Rapids, MI, USA
| | - H Eric Xu
- Key Laboratory of Receptor Research, VARI-SIMM Center, Center for Structure and Function of Drug Targets, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China; Laboratory of Structural Sciences and Laboratory of Structural Biology and Biochemistry, Van Andel Research Institute, Grand Rapids, MI, USA
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53
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Bugge K, Lindorff-Larsen K, Kragelund BB. Understanding single-pass transmembrane receptor signaling from a structural viewpoint-what are we missing? FEBS J 2016; 283:4424-4451. [PMID: 27350538 DOI: 10.1111/febs.13793] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 06/10/2016] [Accepted: 06/27/2016] [Indexed: 11/30/2022]
Abstract
Single-pass transmembrane receptors are involved in essential processes of both physiological and pathological nature and represent more than 1300 proteins in the human genome. Despite the high biological relevance of these receptors, the mechanisms of the signal transductions they facilitate are incompletely understood. One major obstacle is the lack of structures of the transmembrane domains that connect the extracellular ligand-binding domains to the intracellular signaling platforms. Over a period of almost 20 years since the first structure was reported, only 21 of these receptors have become represented by a transmembrane domain structure. This scarceness stands in strong contrast to the significance of these transmembrane α-helices for receptor functionality. In this review, we explore the properties and qualities of the current set of structures, as well as the methodological difficulties associated with their characterization and the challenges left to be overcome. Without an increased and focused effort to bring this class of proteins on par with the remaining membrane protein field, a serious lag in their biological understanding looms. Design of pharmaceutical agents, prediction of mutational affects in relation to disease, and deciphering of functional mechanisms require high-resolution structural information, especially when dealing with a domain carrying so much functionality in so few residues.
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Affiliation(s)
- Katrine Bugge
- Department of Biology, Structural Biology and NMR Laboratory, University of Copenhagen, Denmark
| | - Kresten Lindorff-Larsen
- Department of Biology, Structural Biology and NMR Laboratory, University of Copenhagen, Denmark
| | - Birthe B Kragelund
- Department of Biology, Structural Biology and NMR Laboratory, University of Copenhagen, Denmark
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54
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Reinert J, Richard BC, Klafki HW, Friedrich B, Bayer TA, Wiltfang J, Kovacs GG, Ingelsson M, Lannfelt L, Paetau A, Bergquist J, Wirths O. Deposition of C-terminally truncated Aβ species Aβ37 and Aβ39 in Alzheimer's disease and transgenic mouse models. Acta Neuropathol Commun 2016; 4:24. [PMID: 26955942 PMCID: PMC4784385 DOI: 10.1186/s40478-016-0294-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 02/26/2016] [Indexed: 11/10/2022] Open
Abstract
In Alzheimer's disease (AD) a variety of amyloid β-peptides (Aβ) are deposited in the form of extracellular diffuse and neuritic plaques (NP), as well as within the vasculature. The generation of Aβ from its precursor, the amyloid precursor protein (APP), is a highly complex procedure that involves subsequent proteolysis of APP by β- and γ-secretases. Brain accumulation of Aβ due to impaired Aβ degradation and/or altered ratios between the different Aβ species produced is believed to play a pivotal role in AD pathogenesis. While the presence of Aβ40 and Aβ42 in vascular and parenchymal amyloid have been subject of extensive studies, the deposition of carboxyterminal truncated Aβ peptides in AD has not received comparable attention. In the current study, we for the first time demonstrate the immunohistochemical localization of Aβ37 and Aβ39 in human sporadic AD (SAD). Our study further included the analysis of familial AD (FAD) cases carrying the APP mutations KM670/671NL, E693G and I716F, as well as a case of the PSEN1 ΔExon9 mutation. Aβ37 and Aβ39 were found to be widely distributed within the vasculature in the brains of the majority of studied SAD and FAD cases, the latter also presenting considerable amounts of Aβ37 containing NPs. In addition, both peptides were found to be present in extracellular plaques but only scarce within the vasculature in brains of a variety of transgenic AD mouse models. Taken together, our study indicates the importance of C-terminally truncated Aβ in sporadic and familial AD and raises questions about how these species are generated and regulated.
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55
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Hiruma-Shimizu K, Shimizu H, Thompson GS, Kalverda AP, Patching SG. Deuterated detergents for structural and functional studies of membrane proteins: Properties, chemical synthesis and applications. Mol Membr Biol 2016; 32:139-55. [DOI: 10.3109/09687688.2015.1125536] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
| | - Hiroki Shimizu
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology, Hokkaido, Japan,
| | - Gary S. Thompson
- School of Molecular and Cellular Biology, University of Leeds, Leeds, UK,
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, UK, and
| | - Arnout P. Kalverda
- School of Molecular and Cellular Biology, University of Leeds, Leeds, UK,
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, UK, and
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56
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Nuclear magnetic resonance evidence for the dimer formation of beta amyloid peptide 1-42 in 1,1,1,3,3,3-hexafluoro-2-propanol. Anal Biochem 2016; 498:59-67. [PMID: 26772162 DOI: 10.1016/j.ab.2015.12.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 12/04/2015] [Accepted: 12/29/2015] [Indexed: 01/05/2023]
Abstract
Alzheimer's disease involves accumulation of senile plaques in which filamentous aggregates of amyloid beta (Aβ) peptides are deposited. Recent studies demonstrate that oligomerization pathways of Aβ peptides may be complicated. To understand the mechanisms of Aβ(1-42) oligomer formation in more detail, we have established a method to produce (15)N-labeled Aβ(1-42) suited for nuclear magnetic resonance (NMR) studies. For physicochemical studies, the starting protein material should be solely monomeric and all Aβ aggregates must be removed. Here, we succeeded in fractionating a "precipitation-resistant" fraction of Aβ(1-42) from an "aggregation-prone" fraction by high-performance liquid chromatography (HPLC), even from bacterially overexpressed Aβ(1-42). However, both Aβ(1-42) fractions after 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) treatment formed amyloid fibrils. This indicates that the "aggregation seed" was not completely monomerized during HFIP treatment. In addition, Aβ(1-42) dissolved in HFIP was found to display a monomer-dimer equilibrium, as shown by two-dimensional (1)H-(15)N NMR. We demonstrated that the initial concentration of Aβ during the HFIP pretreatment altered the kinetic profiles of Aβ fibril formation in a thioflavin T fluorescence assay. The findings described here should ensure reproducible results when studying the Aβ(1-42) peptide.
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57
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Prade E, Bittner HJ, Sarkar R, Lopez Del Amo JM, Althoff-Ospelt G, Multhaup G, Hildebrand PW, Reif B. Structural Mechanism of the Interaction of Alzheimer Disease Aβ Fibrils with the Non-steroidal Anti-inflammatory Drug (NSAID) Sulindac Sulfide. J Biol Chem 2015; 290:28737-45. [PMID: 26416887 PMCID: PMC4661391 DOI: 10.1074/jbc.m115.675215] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2015] [Revised: 09/14/2015] [Indexed: 01/12/2023] Open
Abstract
Alzheimer disease is the most severe neurodegenerative disease worldwide. In the past years, a plethora of small molecules interfering with amyloid-β (Aβ) aggregation has been reported. However, their mode of interaction with amyloid fibers is not understood. Non-steroidal anti-inflammatory drugs (NSAIDs) are known γ-secretase modulators; they influence Aβ populations. It has been suggested that NSAIDs are pleiotrophic and can interact with more than one pathomechanism. Here we present a magic angle spinning solid-state NMR study demonstrating that the NSAID sulindac sulfide interacts specifically with Alzheimer disease Aβ fibrils. We find that sulindac sulfide does not induce drastic architectural changes in the fibrillar structure but intercalates between the two β-strands of the amyloid fibril and binds to hydrophobic cavities, which are found consistently in all analyzed structures. The characteristic Asp(23)-Lys(28) salt bridge is not affected upon interacting with sulindac sulfide. The primary binding site is located in the vicinity of residue Gly(33), a residue involved in Met(35) oxidation. The results presented here will assist the search for pharmacologically active molecules that can potentially be employed as lead structures to guide the design of small molecules for the treatment of Alzheimer disease.
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Affiliation(s)
- Elke Prade
- From the Munich Center for Integrated Protein Science at Department Chemie, Technische Universität München, Lichtenbergstr. 4, 85747 Garching, Germany
| | - Heiko J Bittner
- Molecular Modeling, Institute of Medical Physics and Biophysics, Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Riddhiman Sarkar
- From the Munich Center for Integrated Protein Science at Department Chemie, Technische Universität München, Lichtenbergstr. 4, 85747 Garching, Germany
| | | | | | - Gerd Multhaup
- the Department of Pharmacology and Therapeutics, McGill University, Montreal Quebec H3G 1Y6, Canada, and
| | - Peter W Hildebrand
- Molecular Modeling, Institute of Medical Physics and Biophysics, Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Bernd Reif
- From the Munich Center for Integrated Protein Science at Department Chemie, Technische Universität München, Lichtenbergstr. 4, 85747 Garching, Germany, the Helmholtz-Zentrum München, Deutsches Forschungszentrum für Gesundheit und Umwelt, Ingolstädter Landtstr. 1, 85764 Neuherberg, Germany
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58
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Viswanath S, Dominguez L, Foster LS, Straub JE, Elber R. Extension of a protein docking algorithm to membranes and applications to amyloid precursor protein dimerization. Proteins 2015; 83:2170-85. [PMID: 26404856 DOI: 10.1002/prot.24934] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 09/13/2015] [Accepted: 09/17/2015] [Indexed: 12/13/2022]
Abstract
Novel adjustments are introduced to the docking algorithm, DOCK/PIERR, for the purpose of predicting structures of transmembrane protein complexes. Incorporating knowledge about the membrane environment is shown to significantly improve docking accuracy. The extended version of DOCK/PIERR is shown to perform comparably to other leading docking packages. This membrane version of DOCK/PIERR is applied to the prediction of coiled-coil homodimer structures of the transmembrane region of the C-terminal peptide of amyloid precursor protein (C99). Results from MD simulation of the C99 homodimer in POPC bilayer and docking are compared. Docking results are found to capture key aspects of the homodimer ensemble, including the existence of three topologically distinct conformers. Furthermore, the extended version of DOCK/PIERR is successful in capturing the effects of solvation in membrane and micelle. Specifically, DOCK/PIERR reproduces essential differences in the homodimer ensembles simulated in POPC bilayer and DPC micelle, where configurational entropy and surface curvature effects bias the handedness and topology of the homodimer ensemble.
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Affiliation(s)
- Shruthi Viswanath
- Department of Computer Science, University of Texas at Austin, Austin, Texas, 78712.,Institute for Computational Engineering and Sciences, University of Texas at Austin, Austin, Texas, 78712
| | - Laura Dominguez
- Department of Chemistry, Boston University, Boston, Massachusetts, 02215
| | - Leigh S Foster
- Department of Chemistry, Boston University, Boston, Massachusetts, 02215
| | - John E Straub
- Department of Chemistry, Boston University, Boston, Massachusetts, 02215
| | - Ron Elber
- Institute for Computational Engineering and Sciences, University of Texas at Austin, Austin, Texas, 78712.,Department of Chemistry, University of Texas at Austin, Austin, Texas, 78712
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59
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Winkler E, Julius A, Steiner H, Langosch D. Homodimerization Protects the Amyloid Precursor Protein C99 Fragment from Cleavage by γ-Secretase. Biochemistry 2015; 54:6149-52. [DOI: 10.1021/acs.biochem.5b00986] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Edith Winkler
- BMC-Biomedical
Center, Metabolic Biochemistry, Ludwig-Maximilians-University, Munich, Germany
| | - Ayse Julius
- Lehrstuhl
Chemie der Biopolymere, Technische Universität München, Weihenstephaner
Berg 3, 85354 Freising, Germany
- Munich Center For Integrated Protein Science (CIPSM), Munich, Germany
| | - Harald Steiner
- BMC-Biomedical
Center, Metabolic Biochemistry, Ludwig-Maximilians-University, Munich, Germany
- DZNE-German Center for Neurodegenerative Diseases, Munich, Germany
| | - Dieter Langosch
- Lehrstuhl
Chemie der Biopolymere, Technische Universität München, Weihenstephaner
Berg 3, 85354 Freising, Germany
- Munich Center For Integrated Protein Science (CIPSM), Munich, Germany
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60
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Abstract
Transmembrane (TM) helices of integral membrane proteins can facilitate strong and specific noncovalent protein-protein interactions. Mutagenesis and structural analyses have revealed numerous examples in which the interaction between TM helices of single-pass membrane proteins is dependent on a GxxxG or (small)xxx(small) motif. It is therefore tempting to use the presence of these simple motifs as an indicator of TM helix interactions. In this Current Topic review, we point out that these motifs are quite common, with more than 50% of single-pass TM domains containing a (small)xxx(small) motif. However, the actual interaction strength of motif-containing helices depends strongly on sequence context and membrane properties. In addition, recent studies have revealed several GxxxG-containing TM domains that interact via alternative interfaces involving hydrophobic, polar, aromatic, or even ionizable residues that do not form recognizable motifs. In multipass membrane proteins, GxxxG motifs can be important for protein folding, and not just oligomerization. Our current knowledge thus suggests that the presence of a GxxxG motif alone is a weak predictor of protein dimerization in the membrane.
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Affiliation(s)
- Mark G Teese
- Lehrstuhl für Chemie der Biopolymere, Technische Universität München , 85354 Freising, Germany.,Center for Integrated Protein Science Munich (CIPSM) , 81377 Munich, Germany
| | - Dieter Langosch
- Lehrstuhl für Chemie der Biopolymere, Technische Universität München , 85354 Freising, Germany.,Center for Integrated Protein Science Munich (CIPSM) , 81377 Munich, Germany
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61
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Wang Y, Barth P. Evolutionary-guided de novo structure prediction of self-associated transmembrane helical proteins with near-atomic accuracy. Nat Commun 2015; 6:7196. [PMID: 25995083 DOI: 10.1038/ncomms8196] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 04/15/2015] [Indexed: 11/09/2022] Open
Abstract
How specific protein associations regulate the function of membrane receptors remains poorly understood. Conformational flexibility currently hinders the structure determination of several classes of membrane receptors and associated oligomers. Here we develop EFDOCK-TM, a general method to predict self-associated transmembrane protein helical (TMH) structures from sequence guided by co-evolutionary information. We show that accurate intermolecular contacts can be identified using a combination of protein sequence covariation and TMH binding surfaces predicted from sequence. When applied to diverse TMH oligomers, including receptors characterized in multiple conformational and functional states, the method reaches unprecedented near-atomic accuracy for most targets. Blind predictions of structurally uncharacterized receptor tyrosine kinase TMH oligomers provide a plausible hypothesis on the molecular mechanisms of disease-associated point mutations and binding surfaces for the rational design of selective inhibitors. The method sets the stage for uncovering novel determinants of molecular recognition and signalling in single-spanning eukaryotic membrane receptors.
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Affiliation(s)
- Y Wang
- Structural and Computational Biology and Molecular Biophysics Graduate Program, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA
| | - P Barth
- 1] Structural and Computational Biology and Molecular Biophysics Graduate Program, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA [2] Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA [3] Department of Pharmacology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA
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62
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Langosch D, Scharnagl C, Steiner H, Lemberg MK. Understanding intramembrane proteolysis: from protein dynamics to reaction kinetics. Trends Biochem Sci 2015; 40:318-27. [PMID: 25941170 DOI: 10.1016/j.tibs.2015.04.001] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 03/31/2015] [Accepted: 04/01/2015] [Indexed: 12/12/2022]
Abstract
Intramembrane proteolysis - cleavage of proteins within the plane of a membrane - is a widespread phenomenon that can contribute to the functional activation of substrates and is involved in several diseases. Although different families of intramembrane proteases have been discovered and characterized, we currently do not know how these enzymes discriminate between substrates and non-substrates, how site-specific cleavage is achieved, or which factors determine the rate of proteolysis. Focusing on γ-secretase and rhomboid proteases, we argue that answers to these questions may emerge from connecting experimental readouts, such as reaction kinetics and the determination of cleavage sites, to the structures and the conformational dynamics of substrates and enzymes.
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Affiliation(s)
- D Langosch
- Technische Universität München, Lehrstuhl Chemie der Biopolymere, Weihenstephaner Berg 3, 85354 Freising, and Munich Center for Integrated Protein Science (CIMPS(M)), Germany.
| | - C Scharnagl
- Fakultät für Physik E14, Technische Universität München, Maximus-von-Imhof-Forum 4, 85354 Freising, Germany
| | - H Steiner
- Ludwig-Maximilians-University Munich, Metabolic Biochemistry and DZNE (German Center for Neurodegenerative Diseases), Munich, Germany
| | - M K Lemberg
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Deutsches Krebsforschungszentrum (DKFZ)-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
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63
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Chen W, Cotten ML. Expression, purification, and micelle reconstitution of antimicrobial piscidin 1 and piscidin 3 for NMR studies. Protein Expr Purif 2014; 102:63-8. [PMID: 25131859 DOI: 10.1016/j.pep.2014.08.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 07/31/2014] [Accepted: 08/01/2014] [Indexed: 12/28/2022]
Abstract
Piscidin 1 and piscidin 3, which were discovered in the mast cells of hybrid striped sea bass, are homologous antimicrobial peptides that are active against drug-resistant bacteria. Piscidin 1, the more antimicrobial and hemolytic peptide, also has anti-HIV-1 and anti-cancer properties. To understand the reasons underlying the different biological activities of the two peptides and identify principles to design antimicrobial drugs with improved efficacy and lower toxicity, their atomic-level structures must be obtained under physiologically-relevant conditions. High-resolution backbone structures of both piscidins exist in the presence of hydrated phospholipid bilayers but full structures that include the side chains are missing. Here, the piscidins 1 and 3 genes were cloned into the TrpLE vector. The corresponding TrpLE-piscidin fusion partners were expressed in Escherichiacoli and recovered from inclusion bodies. Following steps that included Ni-NTA chromatography, cyanogen bromide cleavage of the fusion proteins, and reverse-phase HPLC, purified piscidins 1 and 3 were recovered in very good yield and characterized by NMR. High quality (15)N-(1)H HSQC spectra of piscidins 1 and 3 bound to SDS micelles were collected, demonstrating the feasibility of producing and purifying the isotopically-labeled piscidin peptides required to determine their full structures by multidimensional NMR spectroscopy.
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Affiliation(s)
- Wen Chen
- Department of Biological Chemistry & Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, United States
| | - Myriam L Cotten
- Department of Chemistry, Hamilton College, 198 College Hill Road, Clinton, NY 13323, United States.
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64
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Alzheimer's disease--a panorama glimpse. Int J Mol Sci 2014; 15:12631-50. [PMID: 25032844 PMCID: PMC4139864 DOI: 10.3390/ijms150712631] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Revised: 06/26/2014] [Accepted: 07/10/2014] [Indexed: 01/05/2023] Open
Abstract
The single-mutation of genes associated with Alzheimer's disease (AD) increases the production of Aβ peptides. An elevated concentration of Aβ peptides is prone to aggregation into oligomers and further deposition as plaque. Aβ plaques and neurofibrillary tangles are two hallmarks of AD. In this review, we provide a broad overview of the diverses sources that could lead to AD, which include genetic origins, Aβ peptides and tau protein. We shall discuss on tau protein and tau accumulation, which result in neurofibrillary tangles. We detail the mechanisms of Aβ aggregation, fibril formation and its polymorphism. We then show the possible links between Aβ and tau pathology. Furthermore, we summarize the structural data of Aβ and its precursor protein obtained via Nuclear Magnetic Resonance (NMR) or X-ray crystallography. At the end, we go through the C-terminal and N-terminal truncated Aβ variants. We wish to draw reader's attention to two predominant and toxic Aβ species, namely Aβ4-42 and pyroglutamate amyloid-beta peptides, which have been neglected for more than a decade and may be crucial in Aβ pathogenesis due to their dominant presence in the AD brain.
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65
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Dominguez L, Foster L, Meredith SC, Straub JE, Thirumalai D. Structural heterogeneity in transmembrane amyloid precursor protein homodimer is a consequence of environmental selection. J Am Chem Soc 2014; 136:9619-26. [PMID: 24926593 PMCID: PMC4105063 DOI: 10.1021/ja503150x] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The 99 amino acid C-terminal fragment of amyloid precursor protein (C99), consisting of a single transmembrane (TM) helix, is known to form homodimers. Homodimers can be processed by γ-secretase to produce amyloid-β (Aβ) protein, which is implicated in Alzheimer's disease (AD). While knowledge of the structure of C99 homodimers is of great importance, experimental NMR studies and simulations have produced varying structural models, including right-handed and left-handed coiled-coils. In order to investigate the structure of this critical protein complex, simulations of the C99(15-55) homodimer in POPC membrane bilayer and DPC surfactant micelle environments were performed using a multiscale approach that blends atomistic and coarse-grained models. The C99(15-55) homodimer adopts a dominant right-handed coiled-coil topology consisting of three characteristic structural states in a bilayer, only one of which is dominant in the micelle. Our structural study, which provides a self-consistent framework for understanding a number of experiments, shows that the energy landscape of the C99 homodimer supports a variety of slowly interconverting structural states. The relative importance of any given state can be modulated through environmental selection realized by altering the membrane or micelle characteristics.
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Affiliation(s)
- Laura Dominguez
- Department of Chemistry, Boston University , Boston, Massachusetts 02215, United States
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66
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Abstract
In this issue of Structure, Tang and colleagues probe how the Flemish mutation in amyloid precursor protein (APP) affects its conformation and cleavage by γ-secretase. They provide molecular insight into how an extracellular inhibitory element and cholesterol interactions affect the generation of Aβ peptides.
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Affiliation(s)
- Hsiang-Kai Lin
- Department of Structural Biology, University of Pittsburgh School of Medicine, Biomedical Science Tower 3, 3501 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Patrick C A van der Wel
- Department of Structural Biology, University of Pittsburgh School of Medicine, Biomedical Science Tower 3, 3501 Fifth Avenue, Pittsburgh, PA 15260, USA.
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