1
|
Ortner M, Guschtschin-Schmidt N, Stelzer W, Muhle-Goll C, Langosch D. Permissive Conformations of a Transmembrane Helix Allow Intramembrane Proteolysis by γ-Secretase. J Mol Biol 2023; 435:168218. [PMID: 37536392 DOI: 10.1016/j.jmb.2023.168218] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 07/26/2023] [Accepted: 07/26/2023] [Indexed: 08/05/2023]
Abstract
The intramembrane protease γ-secretase activates important signaling molecules, such as Notch receptors. It is still unclear, however, how different elements within the primary structure of substrate transmembrane domains (TMDs) contribute to their cleavability. Using a newly developed yeast-based cleavage assay, we identified three crucial regions within the TMDs of the paralogs Notch1 and Notch3 by mutational and gain-of-function approaches. The AAAA or AGAV motifs within the N-terminal half of the TMDs were found to confer strong conformational flexibility to these TMD helices, as determined by mutagenesis coupled to deuterium/hydrogen exchange. Crucial amino acids within the C-terminal half may support substrate docking into the catalytic cleft of presenilin, the enzymatic subunit of γ-secretase. Further, residues close to the C-termini of the TMDs may stabilize a tripartite β-sheet in the substrate/enzyme complex. NMR structures reveal different extents of helix bending as well as an ability to adopt widely differing conformational substates, depending on the sequence of the N-terminal half. The difference in cleavability between Notch1 and Notch3 TMDs is jointly determined by the conformational repertoires of the TMD helices and the sequences of the C-terminal half, as suggested by mutagenesis and building molecular models. In sum, cleavability of a γ-secretase substrate is enabled by different functions of cooperating TMD regions, which deepens our mechanistic understanding of substrate/non-substrate discrimination in intramembrane proteolysis.
Collapse
Affiliation(s)
- Martin Ortner
- Chair of Biopolymer Chemistry, Technical University of Munich, Freising, Germany
| | - Nadja Guschtschin-Schmidt
- Institute for Biological Interfaces 4, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany; Institute of Organic Chemistry, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Walter Stelzer
- Chair of Biopolymer Chemistry, Technical University of Munich, Freising, Germany
| | - Claudia Muhle-Goll
- Institute for Biological Interfaces 4, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany; Institute of Organic Chemistry, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Dieter Langosch
- Chair of Biopolymer Chemistry, Technical University of Munich, Freising, Germany.
| |
Collapse
|
2
|
Cooperation of N- and C-terminal substrate transmembrane domain segments in intramembrane proteolysis by γ-secretase. Commun Biol 2023; 6:177. [PMID: 36792683 PMCID: PMC9931712 DOI: 10.1038/s42003-023-04470-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 01/11/2023] [Indexed: 02/17/2023] Open
Abstract
Intramembrane proteases play a pivotal role in biology and medicine, but how these proteases decode cleavability of a substrate transmembrane (TM) domain remains unclear. Here, we study the role of conformational flexibility of a TM domain, as determined by deuterium/hydrogen exchange, on substrate cleavability by γ-secretase in vitro and in cellulo. By comparing hybrid TMDs based on the natural amyloid precursor protein TM domain and an artificial poly-Leu non-substrate, we find that substrate cleavage requires conformational flexibility within the N-terminal half of the TMD helix (TM-N). Robust cleavability also requires the C-terminal TM sequence (TM-C) containing substrate cleavage sites. Since flexibility of TM-C does not correlate with cleavage efficiency, the role of the TM-C may be defined mainly by its ability to form a cleavage-competent state near the active site, together with parts of presenilin, the enzymatic component of γ-secretase. In sum, cleavability of a γ-secretase substrate appears to depend on cooperating TM domain segments, which deepens our mechanistic understanding of intramembrane proteolysis.
Collapse
|
3
|
Eden A, Zhao J, Xiao Y, Gibson J, Wang C. Covalent fragment inhibits intramembrane proteolysis. Front Mol Biosci 2022; 9:958399. [PMID: 36158579 PMCID: PMC9490316 DOI: 10.3389/fmolb.2022.958399] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 07/01/2022] [Indexed: 01/09/2023] Open
Abstract
Alzheimer's disease (AD) is a serious public health crisis with only one current modifying treatment. The reduction of amyloid load by targeting γ-secretase (GS) has been a leading approach in AD drug discovery and development. Despite the focus on GS inhibition, multiple GS inhibitors (GSIs) have failed in clinical trials as a result of side effects including exacerbated cognitive decline. These side effects are largely attributable to inhibition of normal GS function. Standard enzyme inhibitors target catalytic or allosteric sites of the enzyme, including the active site presenilin, as previous GSIs did. To avoid issues observed from broad-spectrum GSIs we discovered that fragment 6H8 that covalently binds to the substrate of GS, the transmembrane domain of amyloid precursor protein (APPTM). Nuclear Magnetic Resonance (NMR) Spectroscopy combined with MALDI-TOF-MS established 6H8 covalently binds to APPTM. 6H8 acts as a Michael acceptor and covalently links to the side chain amines of lysine residues, specifically targeting a cluster of C-terminal lysines K53-K55. Through this modification, 6H8 can inhibit intramembrane proteolysis of an archaeal homolog of presenilin (the active subunit of GS) via substrate binding with a 2-4 μM IC50, determined by a gel-based cleavage assay. 6H8, while too small to be an effective drug candidate, can be combined with a specific non-covalent partner and function as an effective covalent warhead of a targeted covalent inhibitor (TCI). The future development of the 6H8 fragment into the covalent warhead of a TCI is, to our knowledge, a novel approach to AD drug discovery.
Collapse
Affiliation(s)
- Angela Eden
- Center for Biotechnology and Interdisciplinary Studies, Troy, NY, United States
- Department of Chemistry and Chemical Biology, Troy, NY, United States
- Department of Biological Sciences, Troy, NY, United States
| | - Jing Zhao
- Center for Biotechnology and Interdisciplinary Studies, Troy, NY, United States
| | - Yuanyuan Xiao
- Center for Biotechnology and Interdisciplinary Studies, Troy, NY, United States
| | - James Gibson
- Center for Biotechnology and Interdisciplinary Studies, Troy, NY, United States
| | - Chunyu Wang
- Center for Biotechnology and Interdisciplinary Studies, Troy, NY, United States
- Department of Chemistry and Chemical Biology, Troy, NY, United States
- Department of Biological Sciences, Troy, NY, United States
| |
Collapse
|
4
|
Hitzenberger M, Götz A, Menig S, Brunschweiger B, Zacharias M, Scharnagl C. The dynamics of γ-secretase and its substrates. Semin Cell Dev Biol 2020; 105:86-101. [DOI: 10.1016/j.semcdb.2020.04.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 04/09/2020] [Accepted: 04/15/2020] [Indexed: 12/18/2022]
|
5
|
Dehury B, Tang N, Mehra R, Blundell TL, Kepp KP. Side-by-side comparison of Notch- and C83 binding to γ-secretase in a complete membrane model at physiological temperature. RSC Adv 2020; 10:31215-31232. [PMID: 35520661 PMCID: PMC9056423 DOI: 10.1039/d0ra04683c] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 08/15/2020] [Indexed: 12/29/2022] Open
Abstract
γ-Secretase cleaves the C99 fragment of the amyloid precursor protein, leading to formation of aggregated β-amyloid peptide central to Alzheimer's disease, and Notch, essential for cell regulation. Recent cryogenic electron microscopy (cryo-EM) structures indicate major changes upon substrate binding, a β-sheet recognition motif, and a possible helix unwinding to expose peptide bonds towards nucleophilic attack. Here we report side-by-side comparison of the 303 K dynamics of the two proteins in realistic membranes using molecular dynamics simulations. Our ensembles agree with the cryo-EM data (full-protein Cα-RMSD = 1.62–2.19 Å) but reveal distinct presenilin helix conformation states and thermal β-strand to coil transitions of C83 and Notch100. We identify distinct 303 K hydrogen bond dynamics and water accessibility of the catalytic sites. The RKRR motif (1758–1761) contributes significantly to Notch binding and serves as a “membrane anchor” that prevents Notch displacement. Water that transiently hydrogen bonds to G1753 and V1754 probably represents the catalytic nucleophile. At 303 K, Notch and C83 binding induce different conformation states, with Notch mostly present in a closed state with shorter Asp–Asp distance. This may explain the different outcome of Notch and C99 cleavage, as the latter is more imprecise with many products. Our identified conformation states may aid efforts to develop conformation-selective drugs that target C99 and Notch cleavage differently, e.g. Notch-sparing γ-secretase modulators. Distinct membrane dynamics and conformations of C83- and Notch-bound γ-secretase may aid the development of Notch-sparing treatments of Alzheimer's disease.![]()
Collapse
Affiliation(s)
- Budheswar Dehury
- Department of Chemistry, Technical University of Denmark DK-2800 Kongens Lyngby Denmark +45 45252409.,Department of Biochemistry, University of Cambridge Tennis Court Road CB2 1GA UK
| | - Ning Tang
- Department of Chemistry, Technical University of Denmark DK-2800 Kongens Lyngby Denmark +45 45252409
| | - Rukmankesh Mehra
- Department of Chemistry, Technical University of Denmark DK-2800 Kongens Lyngby Denmark +45 45252409
| | - Tom L Blundell
- Department of Biochemistry, University of Cambridge Tennis Court Road CB2 1GA UK
| | - Kasper P Kepp
- Department of Chemistry, Technical University of Denmark DK-2800 Kongens Lyngby Denmark +45 45252409
| |
Collapse
|
6
|
Zhao J, Liu X, Xia W, Zhang Y, Wang C. Targeting Amyloidogenic Processing of APP in Alzheimer's Disease. Front Mol Neurosci 2020; 13:137. [PMID: 32848600 PMCID: PMC7418514 DOI: 10.3389/fnmol.2020.00137] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 07/08/2020] [Indexed: 12/11/2022] Open
Abstract
Alzheimer's disease (AD) is the most common type of senile dementia, characterized by neurofibrillary tangle and amyloid plaque in brain pathology. Major efforts in AD drug were devoted to the interference with the production and accumulation of amyloid-β peptide (Aβ), which plays a causal role in the pathogenesis of AD. Aβ is generated from amyloid precursor protein (APP), by consecutive cleavage by β-secretase and γ-secretase. Therefore, β-secretase and γ-secretase inhibition have been the focus for AD drug discovery efforts for amyloid reduction. Here, we review β-secretase inhibitors and γ-secretase inhibitors/modulators, and their efficacies in clinical trials. In addition, we discussed the novel concept of specifically targeting the γ-secretase substrate APP. Targeting amyloidogenic processing of APP is still a fundamentally sound strategy to develop disease-modifying AD therapies and recent advance in γ-secretase/APP complex structure provides new opportunities in designing selective inhibitors/modulators for AD.
Collapse
Affiliation(s)
- Jing Zhao
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, United States
| | - Xinyue Liu
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, United States
| | - Weiming Xia
- Geriatric Research Education Clinical Center, Edith Nourse Rogers Memorial Veterans Hospital, Bedford, MA, United States
- Department of Pharmacology and Experimental Therapeutics, School of Medicine, Boston University, Boston, MA, United States
| | - Yingkai Zhang
- Department of Chemistry, New York University, New York, NY, United States
| | - Chunyu Wang
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, United States
- Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY, United States
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, NY, United States
| |
Collapse
|
7
|
Liu X, Zhao J, Zhang Y, Ubarretxena-Belandia I, Forth S, Lieberman RL, Wang C. Substrate-Enzyme Interactions in Intramembrane Proteolysis: γ-Secretase as the Prototype. Front Mol Neurosci 2020; 13:65. [PMID: 32508589 PMCID: PMC7248309 DOI: 10.3389/fnmol.2020.00065] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 04/03/2020] [Indexed: 11/15/2022] Open
Abstract
Intramembrane-cleaving proteases (I-CLiPs) catalyze the hydrolysis of peptide bonds within the transmembrane regions of membrane protein substrates, releasing bioactive fragments that play roles in many physiological and pathological processes. Based on their catalytic mechanism and nucleophile, I-CLiPs are classified into metallo, serine, aspartyl, and glutamyl proteases. Presenilin is the most prominent among I-CLiPs, as the catalytic subunit of γ-secretase (GS) complex responsible for cleaving the amyloid precursor protein (APP) and Notch, as well as many other membrane substrates. Recent cryo-electron microscopy (cryo-EM) structures of GS provide new details on how presenilin recognizes and cleaves APP and Notch. First, presenilin transmembrane helix (TM) 2 and 6 are dynamic. Second, upon binding to GS, the substrate TM helix is unwound from the C-terminus, resulting in an intermolecular β-sheet between the substrate and presenilin. The transition of the substrate C-terminus from α-helix to β-sheet is proposed to expose the scissile peptide bond in an extended conformation, leaving it susceptible to protease cleavage. Despite the astounding new insights in recent years, many crucial questions remain unanswered regarding the inner workings of γ-secretase, however. Key unanswered questions include how the enzyme recognizes and recruits substrates, how substrates are translocated from an initial docking site to the active site, how active site aspartates recruit and coordinate catalytic water, and the nature of the mechanisms of processive trimming of the substrate and product release. Answering these questions will have important implications for drug discovery aimed at selectively reducing the amyloid load in Alzheimer's disease (AD) with minimal side effects.
Collapse
Affiliation(s)
- Xinyue Liu
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, United States
| | - Jing Zhao
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, United States
| | - Yingkai Zhang
- Department of Chemistry, New York University, New York, NY, United States
| | - Iban Ubarretxena-Belandia
- Instituto Biofisika (UPV/EHU, CSIC), University of the Basque Country, Leioa, Spain
- Ikerbasque, Basque Foundation for Science, Bilbao, Spain
| | - Scott Forth
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, United States
- Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY, United States
| | - Raquel L. Lieberman
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, United States
| | - Chunyu Wang
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, United States
- Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY, United States
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, NY, United States
| |
Collapse
|
8
|
Zhao J, Xiao Y, Liu X, Kim S, Wu X, Barros M, Zhuang R, Hou X, Zhang Y, Robakis NK, Li YM, Dordick JS, Ubarretxena-Belandia I, Wang C. Substrate interaction inhibits γ-secretase production of amyloid-β peptides. Chem Commun (Camb) 2020; 56:2578-2581. [PMID: 32016207 PMCID: PMC8219260 DOI: 10.1039/c9cc09170j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Combining NMR, mass spectrometry, AlphaLISA and cell assays, we discovered a compound C1 that binds C-terminal juxtamembrane lysines at the transmembrane domain of the amyloid precursor protein (APPTM) and inhibits γ-secretase production of amyloid-β with μM IC50. Our work suggests that targeting APPTM is a novel and viable strategy in AD drug discovery.
Collapse
Affiliation(s)
- Jing Zhao
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
| | - Yuanyuan Xiao
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
| | - Xinyue Liu
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
| | - Soohyun Kim
- Center for Molecular Biology and Genetics of Neurodegeneration, Departments of Psychiatry and Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Xianzhong Wu
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Marilia Barros
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Ran Zhuang
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
| | - Xuben Hou
- Department of Medicinal Chemistry and Key Laboratory of Chemical Biology of Natural Products (MOE), School of Pharmacy, Shandong University, Jinan, Shandong 250012, China
| | - Yingkai Zhang
- Department of Chemistry, New York University, New York, NY 10003, USA
| | - Nikolaos K Robakis
- Center for Molecular Biology and Genetics of Neurodegeneration, Departments of Psychiatry and Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Yue-Ming Li
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Jonathan S Dordick
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA. and Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY 12180, USA and Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Iban Ubarretxena-Belandia
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA and Instituto Biofisika (UPV/EHU, CSIC), University of the Basque Country, E-48940, Leioa, Spain and Ikerbasque, Basque Foundation for Science, 48013, Bilbao, Spain
| | - Chunyu Wang
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA. and Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY 12180, USA and Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| |
Collapse
|
9
|
Götz A, Mylonas N, Högel P, Silber M, Heinel H, Menig S, Vogel A, Feyrer H, Huster D, Luy B, Langosch D, Scharnagl C, Muhle-Goll C, Kamp F, Steiner H. Modulating Hinge Flexibility in the APP Transmembrane Domain Alters γ-Secretase Cleavage. Biophys J 2019; 116:2103-2120. [PMID: 31130234 PMCID: PMC6554489 DOI: 10.1016/j.bpj.2019.04.030] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 02/14/2019] [Accepted: 04/15/2019] [Indexed: 01/27/2023] Open
Abstract
Intramembrane cleavage of the β-amyloid precursor protein C99 substrate by γ-secretase is implicated in Alzheimer's disease pathogenesis. Biophysical data have suggested that the N-terminal part of the C99 transmembrane domain (TMD) is separated from the C-terminal cleavage domain by a di-glycine hinge. Because the flexibility of this hinge might be critical for γ-secretase cleavage, we mutated one of the glycine residues, G38, to a helix-stabilizing leucine and to a helix-distorting proline. Both mutants impaired γ-secretase cleavage and also altered its cleavage specificity. Circular dichroism, NMR, and backbone amide hydrogen/deuterium exchange measurements as well as molecular dynamics simulations showed that the mutations distinctly altered the intrinsic structural and dynamical properties of the substrate TMD. Although helix destabilization and/or unfolding was not observed at the initial ε-cleavage sites of C99, subtle changes in hinge flexibility were identified that substantially affected helix bending and twisting motions in the entire TMD. These resulted in altered orientation of the distal cleavage domain relative to the N-terminal TMD part. Our data suggest that both enhancing and reducing local helix flexibility of the di-glycine hinge may decrease the occurrence of enzyme-substrate complex conformations required for normal catalysis and that hinge mobility can thus be conducive for productive substrate-enzyme interactions.
Collapse
Affiliation(s)
- Alexander Götz
- Physics of Synthetic Biological Systems (E14), Technical University of Munich, Freising, Germany
| | - Nadine Mylonas
- Biomedical Center (BMC), Metabolic Biochemistry, Ludwig-Maximilians-University, Munich, Germany; German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
| | - Philipp Högel
- Center for Integrated Protein Science Munich at the Lehrstuhl Chemie der Biopolymere, Technical University Munich, Freising, Germany
| | - Mara Silber
- Institute of Organic Chemistry and Institute for Biological Interfaces 4, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Hannes Heinel
- Institute for Medical Physics and Biophysics, Leipzig University, Leipzig, Germany
| | - Simon Menig
- Physics of Synthetic Biological Systems (E14), Technical University of Munich, Freising, Germany
| | - Alexander Vogel
- Institute for Medical Physics and Biophysics, Leipzig University, Leipzig, Germany
| | - Hannes Feyrer
- Institute of Organic Chemistry and Institute for Biological Interfaces 4, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Daniel Huster
- Institute for Medical Physics and Biophysics, Leipzig University, Leipzig, Germany
| | - Burkhard Luy
- Institute of Organic Chemistry and Institute for Biological Interfaces 4, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Dieter Langosch
- Center for Integrated Protein Science Munich at the Lehrstuhl Chemie der Biopolymere, Technical University Munich, Freising, Germany
| | - Christina Scharnagl
- Physics of Synthetic Biological Systems (E14), Technical University of Munich, Freising, Germany.
| | - Claudia Muhle-Goll
- Institute of Organic Chemistry and Institute for Biological Interfaces 4, Karlsruhe Institute of Technology, Karlsruhe, Germany.
| | - Frits Kamp
- Biomedical Center (BMC), Metabolic Biochemistry, Ludwig-Maximilians-University, Munich, Germany
| | - Harald Steiner
- Biomedical Center (BMC), Metabolic Biochemistry, Ludwig-Maximilians-University, Munich, Germany; German Center for Neurodegenerative Diseases (DZNE), Munich, Germany.
| |
Collapse
|
10
|
Hitzenberger M, Zacharias M. Structural Modeling of γ-Secretase Aβ n Complex Formation and Substrate Processing. ACS Chem Neurosci 2019; 10:1826-1840. [PMID: 30638370 DOI: 10.1021/acschemneuro.8b00725] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The intramembrane aspartyl protease γ-secretase (GSEC) cleaves single-span transmembrane helices including the C-terminal fragment of the amyloid precursor protein (APP). This substrate is initially cleaved at the ϵ-site followed by successive processing (trimming) events mostly in steps of three amino acids. GSEC is responsible for the formation of N-terminal APP amyloid-β (Aβ) peptides of different length (e.g., Aβ42) that can form aggregates involved in Alzheimer's disease pathogenesis. The molecular mechanism of GSEC-APP substrate recognition is key for understanding how different peptide products are formed and could help in designing APP-selective modulators. Based on the known structure of apo GSEC and the APP-C99 fragment we have generated putative structural models of the initial binding in three different possible modes using extensive molecular dynamics (MD) simulations. The binding mode with the substrate helix located in a cleft between the transmembrane helices 2 and 3 of the presenilin subunit was identified as a most likely binding mode. Based on this arrangement, the processing steps were investigated using restraint MD simulations to pull the scissile bond (for each processing step) into a transition like (cleavable) state. This allowed us to analyze in detail the motions and energetic contributions of participating residues. The structural model agrees qualitatively well with the influence of many mutations in GSEC and C99. It also explains the effects of inhibitors, cross-linking, as well as spectroscopic data on GSEC substrate binding and can serve as working model for the future planning of structural and biochemical studies.
Collapse
Affiliation(s)
- M. Hitzenberger
- Physics Department T38, Technical University of Munich, James-Frank-Str. 1, 85748 Garching, Germany
| | - M. Zacharias
- Physics Department T38, Technical University of Munich, James-Frank-Str. 1, 85748 Garching, Germany
| |
Collapse
|