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Zoltowska KM, Das U, Lismont S, Enzlein T, Maesako M, Houser MCQ, Franco ML, Özcan B, Gomes Moreira D, Karachentsev D, Becker A, Hopf C, Vilar M, Berezovska O, Mobley W, Chávez-Gutiérrez L. Alzheimer's disease linked Aβ42 exerts product feedback inhibition on γ-secretase impairing downstream cell signaling. eLife 2024; 12:RP90690. [PMID: 39027984 PMCID: PMC11259434 DOI: 10.7554/elife.90690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2024] Open
Abstract
Amyloid β (Aβ) peptides accumulating in the brain are proposed to trigger Alzheimer's disease (AD). However, molecular cascades underlying their toxicity are poorly defined. Here, we explored a novel hypothesis for Aβ42 toxicity that arises from its proven affinity for γ-secretases. We hypothesized that the reported increases in Aβ42, particularly in the endolysosomal compartment, promote the establishment of a product feedback inhibitory mechanism on γ-secretases, and thereby impair downstream signaling events. We conducted kinetic analyses of γ-secretase activity in cell-free systems in the presence of Aβ, as well as cell-based and ex vivo assays in neuronal cell lines, neurons, and brain synaptosomes to assess the impact of Aβ on γ-secretases. We show that human Aβ42 peptides, but neither murine Aβ42 nor human Aβ17-42 (p3), inhibit γ-secretases and trigger accumulation of unprocessed substrates in neurons, including C-terminal fragments (CTFs) of APP, p75, and pan-cadherin. Moreover, Aβ42 treatment dysregulated cellular homeostasis, as shown by the induction of p75-dependent neuronal death in two distinct cellular systems. Our findings raise the possibility that pathological elevations in Aβ42 contribute to cellular toxicity via the γ-secretase inhibition, and provide a novel conceptual framework to address Aβ toxicity in the context of γ-secretase-dependent homeostatic signaling.
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Affiliation(s)
| | - Utpal Das
- Department of Neurosciences, University of California San DiegoLa JollaUnited States
| | - Sam Lismont
- VIB-KU Leuven Center for Brain & Disease ResearchLeuvenBelgium
| | - Thomas Enzlein
- VIB-KU Leuven Center for Brain & Disease ResearchLeuvenBelgium
- Center for Mass Spectrometry and Optical Spectroscopy (CeMOS), Mannheim University of Applied SciencesMannheimGermany
| | - Masato Maesako
- Department of Neurology, Massachusetts General Hospital/Harvard Medical SchoolCharlestownUnited States
| | - Mei CQ Houser
- Department of Neurology, Massachusetts General Hospital/Harvard Medical SchoolCharlestownUnited States
| | - Maria Luisa Franco
- Molecular Basis of Neurodegeneration Unit, Instituto de Biomedicina de ValenciaValenciaSpain
| | - Burcu Özcan
- VIB-KU Leuven Center for Brain & Disease ResearchLeuvenBelgium
| | | | - Dmitry Karachentsev
- Department of Neurosciences, University of California San DiegoLa JollaUnited States
| | - Ann Becker
- Department of Neurosciences, University of California San DiegoLa JollaUnited States
| | - Carsten Hopf
- Center for Mass Spectrometry and Optical Spectroscopy (CeMOS), Mannheim University of Applied SciencesMannheimGermany
- Medical Faculty, Heidelberg UniversityHeidelbergGermany
- Mannheim Center for Translational Neuroscience (MCTN), Medical Faculty Mannheim, Heidelberg UniversityHeidelbergGermany
| | - Marçal Vilar
- Molecular Basis of Neurodegeneration Unit, Instituto de Biomedicina de ValenciaValenciaSpain
| | - Oksana Berezovska
- Department of Neurology, Massachusetts General Hospital/Harvard Medical SchoolCharlestownUnited States
| | - William Mobley
- Department of Neurosciences, University of California San DiegoLa JollaUnited States
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2
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Zoltowska KM, Das U, Lismont S, Enzlein T, Maesako M, Houser MCQ, Franco ML, Özcan B, Moreira DG, Karachentsev D, Becker A, Hopf C, Vilar M, Berezovska O, Mobley W, Chávez-Gutiérrez L. Alzheimer's disease linked Aβ42 exerts product feedback inhibition on γ-secretase impairing downstream cell signaling. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.08.02.551596. [PMID: 37577527 PMCID: PMC10418207 DOI: 10.1101/2023.08.02.551596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
Amyloid β (Aβ) peptides accumulating in the brain are proposed to trigger Alzheimer's disease (AD). However, molecular cascades underlying their toxicity are poorly defined. Here, we explored a novel hypothesis for Aβ42 toxicity that arises from its proven affinity for γ-secretases. We hypothesized that the reported increases in Aβ42, particularly in the endolysosomal compartment, promote the establishment of a product feedback inhibitory mechanism on γ-secretases, and thereby impair downstream signaling events. We show that human Aβ42 peptides, but neither murine Aβ42 nor human Aβ17-42 (p3), inhibit γ-secretases and trigger accumulation of unprocessed substrates in neurons, including C-terminal fragments (CTFs) of APP, p75 and pan-cadherin. Moreover, Aβ42 treatment dysregulated cellular -homeostasis, as shown by the induction of p75-dependent neuronal death in two distinct cellular systems. Our findings raise the possibility that pathological elevations in Aβ42 contribute to cellular toxicity via the γ-secretase inhibition, and provide a novel conceptual framework to address Aβ toxicity in the context of γ-secretase-dependent homeostatic signaling.
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Affiliation(s)
| | - Utpal Das
- Department of Neurosciences, University of California San Diego, La Jolla, CA, United States of America
| | - Sam Lismont
- VIB-KU Leuven Center for Brain & Disease Research, VIB, Leuven, Belgium
| | - Thomas Enzlein
- VIB-KU Leuven Center for Brain & Disease Research, VIB, Leuven, Belgium
- Center for Mass Spectrometry and Optical Spectroscopy (CeMOS), Mannheim University of Applied Sciences, Mannheim, Germany
| | - Masato Maesako
- Department of Neurology, Massachusetts General Hospital/Harvard Medical School, Charlestown, MA, United States of America
| | - Mei CQ Houser
- Department of Neurology, Massachusetts General Hospital/Harvard Medical School, Charlestown, MA, United States of America
| | - María Luisa Franco
- Molecular Basis of Neurodegeneration Unit, Institute of Biomedicine of València (IBV-CSIC), València, Spain
| | - Burcu Özcan
- VIB-KU Leuven Center for Brain & Disease Research, VIB, Leuven, Belgium
| | | | - Dmitry Karachentsev
- Department of Neurosciences, University of California San Diego, La Jolla, CA, United States of America
| | - Ann Becker
- Department of Neurosciences, University of California San Diego, La Jolla, CA, United States of America
| | - Carsten Hopf
- Center for Mass Spectrometry and Optical Spectroscopy (CeMOS), Mannheim University of Applied Sciences, Mannheim, Germany
- Medical Faculty, Heidelberg University, Heidelberg, Germany
- Mannheim Center for Translational Neuroscience (MCTN), Medical Faculty Mannheim, Heidelberg University, Heidelberg, Germany
| | - Marçal Vilar
- Molecular Basis of Neurodegeneration Unit, Institute of Biomedicine of València (IBV-CSIC), València, Spain
| | - Oksana Berezovska
- Department of Neurology, Massachusetts General Hospital/Harvard Medical School, Charlestown, MA, United States of America
| | - William Mobley
- Department of Neurosciences, University of California San Diego, La Jolla, CA, United States of America
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3
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Wong E, Frost GR, Li YM. γ-Secretase Modulatory Proteins: The Guiding Hand Behind the Running Scissors. Front Aging Neurosci 2020; 12:614690. [PMID: 33343338 PMCID: PMC7738330 DOI: 10.3389/fnagi.2020.614690] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 11/10/2020] [Indexed: 12/16/2022] Open
Abstract
Described as the "proteasome of the membrane" or the "scissors in the membrane," γ-secretase has notoriously complicated biology, and even after decades of research, the full extent of its regulatory mechanism remains unclear. γ-Secretase is an intramembrane aspartyl protease complex composed of four obligatory subunits: Nicastrin (NCT), Presenilin (PS), Presenilin Enhancer-2 (Pen-2), and Anterior pharynx-defective-1 (Aph-1). γ-Secretase cleaves numerous type 1 transmembrane substrates, with no apparent homology, and plays major roles in broad biological pathways such as development, neurogenesis, and cancer. Notch and the amyloid precursor protein (APP) and are undoubtedly the best-studied γ-secretase substrates because of their role in cancer and Alzheimer's disease (AD) and therefore became the focus of increasing studies as an attractive therapeutic target. The regulation of γ-secretase is intricate and involves the function of multiple cellular entities. Recently, γ-secretase modulatory proteins (GSMPs), which are non-essential subunits and yet modulate γ-secretase activity and specificity, have emerged as an important component in guiding γ-secretase. GSMPs are responsive to cellular and environmental changes and therefore, provide another layer of regulation of γ-secretase. This type of enzymatic regulation allows for a rapid and fine-tuning of γ-secretase activity when appropriate signals appear enabling a temporal level of regulation. In this review article, we discuss the latest developments on GSMPs and implications on the development of effective therapeutics for γ-secretase-associated diseases such as AD and cancer.
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Affiliation(s)
- Eitan Wong
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, United States
| | | | - Yue-Ming Li
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, United States
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4
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Sinha A, Chang JC, Xu P, Gindinova K, Cho Y, Sun W, Wu X, Li YM, Greengard P, Kelly JW, Sinha SC. Brain Permeable Tafamidis Amide Analogs for Stabilizing TTR and Reducing APP Cleavage. ACS Med Chem Lett 2020; 11:1973-1979. [PMID: 33062181 PMCID: PMC7549266 DOI: 10.1021/acsmedchemlett.9b00688] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Accepted: 03/02/2020] [Indexed: 02/08/2023] Open
Abstract
Tafamidis, 1, a potent transthyretin kinetic stabilizer, weakly inhibits the γ-secretase enzyme in vitro. We have synthesized four amide derivatives of 1. These compounds reduce production of the Aβ peptide in N2a695 cells but do not inhibit the γ-secretase enzyme in cell-free assays. By performing fluorescence correlation spectroscopy, we have shown that TTR inhibits Aβ oligomerization and that addition of tafamidis or its amide derivative does not affect TTR's ability to inhibit Aβ oligomerization. The piperazine amide derivative of tafamidis (1a) efficiently penetrates and accumulates in mouse brain and undergoes proteolysis under physiological conditions in mice to produce tafamidis.
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Affiliation(s)
- Anjana Sinha
- Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, New York 10065, United States
| | - Jerry C Chang
- Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, New York 10065, United States
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, United States
| | - Peng Xu
- Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, New York 10065, United States
| | - Katherina Gindinova
- Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, New York 10065, United States
| | - Younhee Cho
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Weilin Sun
- Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, New York 10065, United States
| | - Xianzhong Wu
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, United States
| | - Yue Ming Li
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, United States
| | - Paul Greengard
- Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, New York 10065, United States
| | - Jeffery W Kelly
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Subhash C Sinha
- Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, New York 10065, United States
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5
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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.
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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
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6
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Verhelst SHL. Intramembrane proteases as drug targets. FEBS J 2017; 284:1489-1502. [PMID: 27889944 DOI: 10.1111/febs.13979] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 11/14/2016] [Accepted: 11/24/2016] [Indexed: 01/04/2023]
Abstract
Proteases are considered attractive drug targets. Various drugs targeting classical, soluble proteases have been approved for treatment of human disease. Intramembrane proteases (IMPs) are a more recently discovered group of proteolytic enzymes. They are embedded in lipid bilayers and their active sites are located in the plane of a membrane. All four mechanistic families of IMPs have been linked to disease, but currently, no drugs against IMPs have entered the market. In this review, I will outline the function of IMPs with a focus on the ones involved in human disease, which includes Alzheimer's disease, cancer, and infectious diseases by microorganisms. Inhibitors of IMPs are known for all mechanistic classes, but are not yet very potent or selective - aside from those targeting γ-secretase. I will here describe the different features of IMP inhibitors and discuss a list of issues that need attention in the near future in order to improve the drug development for IMPs.
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Affiliation(s)
- Steven H L Verhelst
- Department of Cellular and Molecular Medicine, KU Leuven - University of Leuven, Belgium.,AG Chemical Proteomics, Leibniz Institute for Analytical Sciences ISAS, Dortmund, Germany
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7
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Gilchrist ML, Ahn K, Li YM. Imaging and Functional Analysis of γ-Secretase and Substrate in a Proteolipobead System with an Activity-Based Probe. Anal Chem 2016; 88:1303-11. [PMID: 26699370 PMCID: PMC4911041 DOI: 10.1021/acs.analchem.5b03762] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Investigation of intramembranal protease catalysis demands the generation of intact biomembrane assemblies with structural integrity and lateral mobility. Here, we report the development of a microsphere supported-biomembrane platform enabling characterization of γ-secretase and substrate within proteolipobead assemblies via microscopy and flow cytometry. The active enzyme loading levels were tracked using an activity-based probe, with the biomembranes delineated by carbocyanine lipid reporters. Proteolipobeads formed from HeLa proteoliposomes gave rise to homogeneous distributions of active γ-secretase within supported biomembranes with native-like fluidity. The substrate loading into supported biomembranes was detergent-dependent, as evidenced by even colocalization of substrate and lipid tracers in confocal 3D imaging of individual proteolipobeads. Moreover, the loading level was tunable with bulk substrate concentration. γ-Secretase substrate cleavage and its inhibition within γ-secretase proteolipobeads were observed. This platform offers a means to visualize enzyme and substrate loading, activity, and inhibition in a controllable biomembrane microenvironment.
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Affiliation(s)
- M. Lane Gilchrist
- Department of Chemical Engineering and the Department of Biomedical Engineering, The City College of the City University of New York, 140th Street and Convent Avenue, New York, New York 10031, United States
| | - Kwangwook Ahn
- Chemistry Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York 10065, United States
| | - Yue-Ming Li
- Chemistry Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York 10065, United States
- Program of Pharmacology, Weill Graduate School of Medical Sciences of Cornell University, New York, New York 10021, United States
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8
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Shum D, Bhinder B, Radu C, Farazi T, Landthaler M, Tuschl T, Calder P, Ramirez CN, Djaballah H. An image-based biosensor assay strategy to screen for modulators of the microRNA 21 biogenesis pathway. Comb Chem High Throughput Screen 2013; 15:529-41. [PMID: 22540737 DOI: 10.2174/138620712801619131] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Revised: 04/12/2011] [Accepted: 04/13/2012] [Indexed: 12/21/2022]
Abstract
microRNAs (miRNAs) are evolutionary conserved, small endogenous non-coding, RNA molecules. Although their mode of action has been extensively studied, little is known about their biogenesis. As their altered expression has been implicated in many diseases, small molecules that would modulate their expression are sought after. They are generated through the concerted action of several complexes which promote their transcription, maturation, export, trafficking, and loading of mature miRNA into silencing complexes. An increasing number of studies have suggested that each of these steps serves as a regulatory junction in the process, and therefore provides an intervention point. For this purpose, we have developed a simple image-based assay strategy to screen for such modulators. Here, we describe its successful implementation which combines the use of a microRNA 21 (miR-21) synthetic mimic together with an EGFP based reporter cell line, where its expression is under the control of miR-21, to monitor EGFP expression in a format suitable for HTS. The strategy was further validated using a small panel of known gene modulators of the miRNA pathway. A screen was performed in duplicate against a library of 6,912 compounds and identified 48 initial positives exhibiting enhanced EGFP fluorescence intensity. 42 compounds were found to be inherently fluorescent in the green channel leaving the remaining 6 as potential inhibitors and with a positive rate of 0.09%. Taken together, this validated strategy offers the opportunity to discover novel and specific inhibitors of the pathway through the screening of diverse chemical libraries.
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Affiliation(s)
- David Shum
- HTS Core Facility, Molecular Pharmacology and Chemistry Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
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9
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Feldman T, Kabaleeswaran V, Jang SB, Antczak C, Djaballah H, Wu H, Jiang X. A class of allosteric caspase inhibitors identified by high-throughput screening. Mol Cell 2012; 47:585-95. [PMID: 22795132 DOI: 10.1016/j.molcel.2012.06.007] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Revised: 10/11/2011] [Accepted: 06/01/2012] [Indexed: 10/28/2022]
Abstract
Caspase inhibition is a promising approach for treating multiple diseases. Using a reconstituted assay and high-throughput screening, we identified a group of nonpeptide caspase inhibitors. These inhibitors share common chemical scaffolds, suggesting the same mechanism of action. They can inhibit apoptosis in various cell types induced by multiple stimuli; they can also inhibit caspase-1-mediated interleukin generation in macrophages, indicating potential anti-inflammatory application. While these compounds inhibit all the tested caspases, kinetic analysis indicates they do not compete for the catalytic sites of the enzymes. The cocrystal structure of one of these compounds with caspase-7 reveals that it binds to the dimerization interface of the caspase, another common structural element shared by all active caspases. Consistently, biochemical analysis demonstrates that the compound abates caspase-8 dimerization. Based on these kinetic, biochemical, and structural analyses, we suggest that these compounds are allosteric caspase inhibitors that function through binding to the dimerization interface of caspases.
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Affiliation(s)
- Taya Feldman
- Cell Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
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10
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Tseng HM, Shum D, Bhinder B, Escobar S, Veomett NJ, Tomkinson AE, Gin DY, Djaballah H, Scheinberg DA. A high-throughput scintillation proximity-based assay for human DNA ligase IV. Assay Drug Dev Technol 2011; 10:235-49. [PMID: 22192310 DOI: 10.1089/adt.2011.0404] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Ionizing radiation (IR) and certain chemotherapeutic drugs are designed to generate cytotoxic DNA double-strand breaks (DSBs) in cancer cells. Inhibition of the major DSB repair pathway, nonhomologous end joining (NHEJ), will enhance the cytotoxicity of these agents. Screening for inhibitors of the DNA ligase IV (Lig4), which mediates the final ligation step in NHEJ, offers a novel target-based drug discovery opportunity. For this purpose, we have developed an enzymatic assay to identify chemicals that block the transfer of [α-(33)P]-AMP from the complex Lig4-[α-(33)P]-AMP onto the 5' end of a double-stranded DNA substrate and adapted it to a scintillation proximity assay (SPA). A screen was performed against a collection of 5,280 compounds. Assay statistics show an average Z' value of 0.73, indicative of a robust assay in this SPA format. Using a threshold of >20% inhibition, 10 compounds were initially scored as positive hits. A follow-up screen confirmed four compounds with IC(50) values ranging from 1 to 30 μM. Rabeprazole and U73122 were found to specifically block the adenylate transfer step and DNA rejoining; in whole live cell assays, these compounds were found to inhibit the repair of DSBs generated by IR. The ability to screen and identify Lig4 inhibitors suggests that they may have utility as chemo- and radio-sensitizers in combination therapy and provides a rationale for using this screening strategy to identify additional inhibitors.
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Affiliation(s)
- Hui-Min Tseng
- Molecular Pharmacology and Chemistry Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10583, USA
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11
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Rao TD, Rosales N, Spriggs DR. Dual-fluorescence isogenic high-content screening for MUC16/CA125 selective agents. Mol Cancer Ther 2011; 10:1939-48. [PMID: 21817115 DOI: 10.1158/1535-7163.mct-11-0228] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Most of the currently used cancer chemotherapies are based on compounds that inhibit general cellular mechanisms, such as DNA replication or tubulin function, and lack specificity in relation to features of the cancer cell. Recent advances in genomic studies have increased our knowledge of tumor cell biology, and a panoply of new targets have been postulated. This has provided an opportunity to develop and validate drugs that specifically target cancer cells through their unique genetic characteristics. Identification of MUC16/CA125 both as a marker and a driver of transformation led us to design a target-based high-content screen to identify and classify compounds that exhibit differential effect on MUC16-expressing cells. We developed a coculture assay in 384-well plate containing isogenic ovarian cancer cells that are positive or negative for the MUC16 protein. High-throughput screening of our small molecule pilot library led to the identification of compounds preferentially cytotoxic to MUC16(+) or MUC16(-) cells, using a Preferential Score analysis. We compared screening results in both A2780 and SK-OV-3 ovarian cancer cells in single and coculture settings. We also identified compounds that were cytotoxic for both types of ovarian cancer cells regardless of the MUC16 status. Compounds that were preferentially targeting MUC16 cells were subsequently confirmed by caspase-induction assays. The isogenic, dual-color fluorescence strategy is an innovative approach that can effectively identify novel drug candidates, selectively targeting cancer cells that have unique molecular properties.
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Affiliation(s)
- Thapi D Rao
- Laboratory of Clinical Pharmacology, Department of Medicine, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
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12
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Shum D, Smith JL, Hirsch AJ, Bhinder B, Radu C, Stein DA, Nelson JA, Früh K, Djaballah H. High-content assay to identify inhibitors of dengue virus infection. Assay Drug Dev Technol 2011; 8:553-70. [PMID: 20973722 DOI: 10.1089/adt.2010.0321] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Dengue virus (DENV) infections are vectored by mosquitoes and constitute one of the most prevalent infectious diseases in many parts of the world, affecting millions of people annually. Current treatments for DENV infections are nonspecific and largely ineffective. In this study, we describe the adaptation of a high-content cell-based assay for screening against DENV-infected cells to identify inhibitors and modulators of DENV infection. Using this high-content approach, we monitored the inhibition of test compounds on DENV protein production by means of immunofluorescence staining of DENV glycoprotein envelope, simultaneously evaluating cytotoxicity in HEK293 cells. The adapted 384-well microtiter-based assay was validated using a small panel of compounds previously reported as having inhibitory activity against DENV infections of cell cultures, including compounds with antiviral activity (ribavirin), inhibitors of cellular signaling pathways (U0126), and polysaccharides that are presumed to interfere with virus attachment (carrageenan). A screen was performed against a collection of 5,632 well-characterized bioactives, including U.S. Food and Drug Administration-approved drugs. Assay control statistics show an average Z' of 0.63, indicative of a robust assay in this cell-based format. Using a threshold of >80% DENV inhibition with <20% cellular cytotoxicity, 79 compounds were initially scored as positive hits. A follow-up screen confirmed 73 compounds with IC₅₀ potencies ranging from 60 nM to 9 μM and yielding a hit rate of 1.3%. Over half of the confirmed hits are known to target transporters, receptors, and protein kinases, providing potential opportunity for drug repurposing to treat DENV infections. In summary, this assay offers the opportunity to screen libraries of chemical compounds, in an effort to identify and develop novel drug candidates against DENV infections.
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Affiliation(s)
- David Shum
- HTS Core Facility, Molecular Pharmacology and Chemistry Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA
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Tian Y, Crump CJ, Li YM. Dual role of alpha-secretase cleavage in the regulation of gamma-secretase activity for amyloid production. J Biol Chem 2010; 285:32549-56. [PMID: 20675367 DOI: 10.1074/jbc.m110.128439] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Processing of the amyloid precursor protein (APP) by β- and γ-secretases generates pathogenic β-amyloid (Aβ) peptides associated with Alzheimer disease (AD), whereas cleavage of APP by α-secretases precludes Aβ formation. Little is known about the role of α-secretase cleavage in γ-secretase regulation. Here, we show that α-secretase-cleaved APP C-terminal product (αCTF) functions as an inhibitor of γ-secretase. We demonstrate that the substrate inhibitory domain (ASID) within αCTF, which is bisected by the α-secretase cleavage site, contributes to this negative regulation because deleting or masking this domain turns αCTF into a better substrate for γ-secretase. Moreover, α-secretase cleavage can potentiate the inhibitory effect of ASID. Inhibition of γ-secretase activity by αCTF is observed in both in vitro and cellular systems. This work reveals an unforeseen role for α-secretase in generating an endogenous γ-secretase inhibitor that down-regulates the production of Aβ. Deregulation of this feedback mechanism may contribute to the pathogenesis of AD.
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Affiliation(s)
- Yuan Tian
- Molecular Pharmacology and Chemistry Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA
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