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Abstract
We report a concise, stereocontrolled synthesis of the neurotoxic sesquiterpenoid (-)-picrotoxinin (1, PXN). The brevity of the route is due to regio- and stereoselective formation of the [4.3.0] bicyclic core by incorporation of a symmetrizing geminal dimethyl group at C5. Dimethylation then enables selective C-O bond formation in multiple intermediates. A series of strong bond (C-C and C-H) cleavages convert the C5 gem-dimethyl group to the C15 lactone of PXN.
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Affiliation(s)
| | - Guanghu Tong
- Department of Chemistry, The Scripps Research Institute, 10550 N Torrey Pines Rd, La Jolla, CA 92037, United States
| | | | - Hannah Burdge
- Department of Chemistry, The Scripps Research Institute, 10550 N Torrey Pines Rd, La Jolla, CA 92037, United States
| | - Ryan A. Shenvi
- Department of Chemistry, The Scripps Research Institute, 10550 N Torrey Pines Rd, La Jolla, CA 92037, United States
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2
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Lennon Luo SX, Liu Y, Lambrecht MJ, Ortwine DF, DiPasquale AG, Liang J, Wang X, Zbieg JR, Li J. cis-Selective synthesis of 1,3-disubstituted tetrahydro-β-carbolines from N-sulfonyl N,S-acetals. Org Biomol Chem 2019; 17:9510-9513. [PMID: 31657418 DOI: 10.1039/c9ob01796h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Nucleophilic addition of Grignard reagents to tetrahydro-β-carboline (THC) N-sulfonyl N,S-acetal generates exclusively cis-1,3-disubstituted THCs with a unique 1,3-diaxial conformation. The stereochemical relationship of the 1,3-substituents was confirmed by 2-dimensional NMR spectroscopy and X-ray crystallography. The mechanism of the reaction is proposed based on crystal structures and molecular orbital calculations.
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3
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Abstract
The asmarines are a family of cytotoxic natural products whose mechanism of action is unknown. Here, we used chemical synthesis to reverse engineer the asmarines and understand the functions of their individual components. We found that the potent asmarine analog "delmarine" arrested the mammalian cell cycle in the G1 phase and that both cell cycle arrest and cytotoxicity were rescued by cotreatment with ferric and ferrous salts. Cellular iron deprivation was clearly indicated by changes in iron-responsive protein markers, and cytotoxicity occurred independently of radical oxygen species (ROS) production. Chemical synthesis allowed for annotation of the distinct structural motifs required for these effects, especially the unusual diazepine, which we found enforced an iron-binding tautomer without distortion of the NCNO dihedral angle out of plane. With this information and a correlation of cytotoxicity with logP, we could replace the diazepine by lipophilic group appendage to N9, which avoided steric clash with the N6-alkyl required to access the aminopyridine. This study transformed the asmarines, scarce marine metabolites, into easily synthesized, modular chemotypes that may complement or succeed iron-selective binders in clinical trials and use.
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Affiliation(s)
- Michael J. Lambrecht
- Department of Chemistry and Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California 92037, United States
| | - Jeffery W. Kelly
- Department of Chemistry and Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California 92037, United States
| | - Ryan A. Shenvi
- Department of Chemistry and Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California 92037, United States
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4
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Zheng X, Andruska N, Lambrecht MJ, He S, Parissenti A, Hergenrother PJ, Nelson ER, Shapiro DJ. Targeting multidrug-resistant ovarian cancer through estrogen receptor α dependent ATP depletion caused by hyperactivation of the unfolded protein response. Oncotarget 2016; 9:14741-14753. [PMID: 29599904 PMCID: PMC5871075 DOI: 10.18632/oncotarget.10819] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 07/10/2016] [Indexed: 12/14/2022] Open
Abstract
Ovarian cancers often recur and tumors acquire resistance to chemotherapy due to overexpression of the ATP-dependent efflux pump, multidrug resistance protein 1 (MDR1/P-glycoprotein/ABCB1). Nontoxic small molecule inhibitors targeting MDR1 have remained largely elusive. Instead, in a novel application of our recently described estrogen receptor α (ERα) biomodulator, BHPI, we targeted MDR1’s substrate, ATP. BHPI depletes intracellular ATP and nearly blocks MDR1-mediated drug efflux in ovarian cancer cells by inducing toxic hyperactivation of the endoplasmic reticulum stress sensor, the unfolded protein response (UPR). BHPI increased sensitivity of MDR1 overexpressing multidrug resistant OVCAR-3 ovarian cancer cells to killing by paclitaxel by >1,000 fold. BHPI also restored doxorubicin sensitivity in OVCAR-3 cells and in MDR1 overexpressing breast cancer cells. In an orthotopic OVCAR-3 xenograft model, paclitaxel was ineffective and the paclitaxel-treated group was uniquely prone to form large secondary tumors in adjacent tissue. BHPI alone strongly reduced tumor growth. Notably, tumors were undetectable in mice treated with BHPI plus paclitaxel. Compared to control ovarian tumors, after the combination therapy, levels of the plasma ovarian cancer biomarker CA125 were at least several hundred folds lower; moreover, CA125 levels progressively declined to undetectable. Targeting MDR1 through UPR-dependent ATP depletion represents a promising therapeutic strategy.
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Affiliation(s)
- Xiaobin Zheng
- Department of Biochemistry University of Illinois, Urbana, IL, USA
| | - Neal Andruska
- Department of Biochemistry University of Illinois, Urbana, IL, USA.,College of Medicine, University of Illinois, Urbana, IL, USA
| | | | - Sisi He
- Department of Molecular Integrative Physiology, University of Illinois, Urbana, IL, USA
| | - Amadeo Parissenti
- Cancer Research Program, Advanced Medical Research Institute of Canada, Sudbury, ON, Canada
| | | | - Erik R Nelson
- Department of Molecular Integrative Physiology, University of Illinois, Urbana, IL, USA.,University of Illinois Cancer Center, Urbana, IL, USA
| | - David J Shapiro
- Department of Biochemistry University of Illinois, Urbana, IL, USA.,University of Illinois Cancer Center, Urbana, IL, USA.,College of Medicine, University of Illinois, Urbana, IL, USA
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Palchaudhuri R, Lambrecht MJ, Botham RC, Partlow KC, van Ham TJ, Putt KS, Nguyen LT, Kim SH, Peterson RT, Fan TM, Hergenrother PJ. A Small Molecule that Induces Intrinsic Pathway Apoptosis with Unparalleled Speed. Cell Rep 2015; 13:2027-36. [PMID: 26655912 DOI: 10.1016/j.celrep.2015.10.042] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Revised: 09/08/2015] [Accepted: 10/14/2015] [Indexed: 10/22/2022] Open
Abstract
Apoptosis is generally believed to be a process that requires several hours, in contrast to non-programmed forms of cell death that can occur in minutes. Our findings challenge the time-consuming nature of apoptosis as we describe the discovery and characterization of a small molecule, named Raptinal, which initiates intrinsic pathway caspase-dependent apoptosis within minutes in multiple cell lines. Comparison to a mechanistically diverse panel of apoptotic stimuli reveals that Raptinal-induced apoptosis proceeds with unparalleled speed. The rapid phenotype enabled identification of the critical roles of mitochondrial voltage-dependent anion channel function, mitochondrial membrane potential/coupled respiration, and mitochondrial complex I, III, and IV function for apoptosis induction. Use of Raptinal in whole organisms demonstrates its utility for studying apoptosis in vivo for a variety of applications. Overall, rapid inducers of apoptosis are powerful tools that will be used in a variety of settings to generate further insight into the apoptotic machinery.
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Affiliation(s)
- Rahul Palchaudhuri
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Michael J Lambrecht
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Rachel C Botham
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Kathryn C Partlow
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Tjakko J van Ham
- Cardiovascular Research Center and Division of Cardiology, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA; Broad Institute, Cambridge, MA 02142, USA
| | - Karson S Putt
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Laurie T Nguyen
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Seok-Ho Kim
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Randall T Peterson
- Cardiovascular Research Center and Division of Cardiology, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA; Broad Institute, Cambridge, MA 02142, USA
| | - Timothy M Fan
- Department of Veterinary Clinical Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61802, USA
| | - Paul J Hergenrother
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
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Lambrecht MJ, Brichacek M, Barkauskaite E, Ariza A, Ahel I, Hergenrother PJ. Synthesis of dimeric ADP-ribose and its structure with human poly(ADP-ribose) glycohydrolase. J Am Chem Soc 2015; 137:3558-64. [PMID: 25706250 PMCID: PMC6089346 DOI: 10.1021/ja512528p] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Poly(ADP-ribosyl)ation is a common post-translational modification that mediates a wide variety of cellular processes including DNA damage repair, chromatin regulation, transcription, and apoptosis. The difficulty associated with accessing poly(ADP-ribose) (PAR) in a homogeneous form has been an impediment to understanding the interactions of PAR with poly(ADP-ribose) glycohydrolase (PARG) and other binding proteins. Here we describe the chemical synthesis of the ADP-ribose dimer, and we use this compound to obtain the first human PARG substrate-enzyme cocrystal structure. Chemical synthesis of PAR is an attractive alternative to traditional enzymatic synthesis and fractionation, allowing access to products such as dimeric ADP-ribose, which has been detected but never isolated from natural sources. Additionally, we describe the synthesis of an alkynylated dimer and demonstrate that this compound can be used to synthesize PAR probes including biotin and fluorophore-labeled compounds. The fluorescently labeled ADP-ribose dimer was then utilized in a general fluorescence polarization-based PAR-protein binding assay. Finally, we use intermediates of our synthesis to access various PAR fragments, and evaluation of these compounds as substrates for PARG reveals the minimal features for substrate recognition and enzymatic cleavage. Homogeneous PAR oligomers and unnatural variants produced from chemical synthesis will allow for further detailed structural and biochemical studies on the interaction of PAR with its many protein binding partners.
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Affiliation(s)
- Michael J. Lambrecht
- University of Illinois, Department of Chemistry, Roger Adams Laboratory, 600 South Mathews, Urbana, Illinois 61801, USA
| | - Matthew Brichacek
- University of Illinois, Department of Chemistry, Roger Adams Laboratory, 600 South Mathews, Urbana, Illinois 61801, USA
| | - Eva Barkauskaite
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Antonio Ariza
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Ivan Ahel
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Paul J. Hergenrother
- University of Illinois, Department of Chemistry, Roger Adams Laboratory, 600 South Mathews, Urbana, Illinois 61801, USA
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