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Secka J, Pal A, Acquah FA, Mooers BHM, Karki AB, Mahjoub D, Fakhr MK, Wallace DR, Okada T, Toyooka N, Kuta A, Koduri N, Herndon D, Roberts KP, Wang Z, Hileman B, Rajagopal N, Hussaini SR. Coupling of acceptor-substituted diazo compounds and tertiary thioamides: synthesis of enamino carbonyl compounds and their pharmacological evaluation. RSC Adv 2022; 12:19431-19444. [PMID: 35865562 PMCID: PMC9256013 DOI: 10.1039/d2ra02415b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 06/25/2022] [Indexed: 11/25/2022] Open
Abstract
This paper describes the synthesis of enamino carbonyl compounds by the copper(i)-catalyzed coupling of acceptor-substituted diazo compounds and tertiary thioamides. We plan to use this method to synthesize indolizidine (−)-237D analogs to find α6-selective antismoking agents. Therefore, we also performed in silico α6-nAchRs binding studies of selected products. Compounds with low root-mean-square deviation values showed more favorable binding free energies. We also report preliminary pharmacokinetic data on indolizidine (−)-237D and found it to have weak activity at CYP3A4. In addition, as enamino carbonyl compounds are also known for antimicrobial properties, we screened previously reported and new enamino carbonyl compounds for antibacterial, antimicrobial, and antifungal properties. Eleven compounds showed significant antimicrobial activities. This paper describes the synthesis of enamino carbonyl compounds by the copper(i)-catalyzed coupling of acceptor-substituted diazo compounds and tertiary thioamides.![]()
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Affiliation(s)
- Jim Secka
- Department of Chemistry and Biochemistry, The University of Tulsa 800 S. Tucker Drive Tulsa Oklahoma 74104 USA
| | - Arpan Pal
- Department of Chemistry and Biochemistry, The University of Tulsa 800 S. Tucker Drive Tulsa Oklahoma 74104 USA
| | - Francis A Acquah
- Department of Biochemistry and Molecular Biology, University of Oklahoma of Health Sciences Center Oklahoma City OK 73104 Unites States.,Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma Health Sciences Center Oklahoma City OK 73104 USA.,Laboratory of Biomolecular Structure and Function, University of Oklahoma of Health Sciences Center Oklahoma City OK 73104 USA
| | - Blaine H M Mooers
- Department of Biochemistry and Molecular Biology, University of Oklahoma of Health Sciences Center Oklahoma City OK 73104 Unites States.,Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma Health Sciences Center Oklahoma City OK 73104 USA.,Laboratory of Biomolecular Structure and Function, University of Oklahoma of Health Sciences Center Oklahoma City OK 73104 USA
| | - Anand B Karki
- Department of Biological Science, The University of Tulsa 800 S. Tucker Drive Tulsa Oklahoma 74104 USA
| | - Dania Mahjoub
- Department of Biological Science, The University of Tulsa 800 S. Tucker Drive Tulsa Oklahoma 74104 USA
| | - Mohamed K Fakhr
- Department of Biological Science, The University of Tulsa 800 S. Tucker Drive Tulsa Oklahoma 74104 USA
| | - David R Wallace
- Department of Pharmacology and Physiology, Oklahoma State University Center for Health Sciences Tulsa Oklahoma 74107 USA
| | - Takuya Okada
- Faculty of Engineering, University of Toyama 3190 Gofuku Toyama 930-8555 Japan
| | - Naoki Toyooka
- Faculty of Engineering, University of Toyama 3190 Gofuku Toyama 930-8555 Japan
| | - Adama Kuta
- Department of Chemistry and Biochemistry, The University of Tulsa 800 S. Tucker Drive Tulsa Oklahoma 74104 USA
| | - Naga Koduri
- Department of Chemistry and Biochemistry, The University of Tulsa 800 S. Tucker Drive Tulsa Oklahoma 74104 USA
| | - Deacon Herndon
- Department of Chemistry and Biochemistry, The University of Tulsa 800 S. Tucker Drive Tulsa Oklahoma 74104 USA
| | - Kenneth P Roberts
- Department of Chemistry and Biochemistry, The University of Tulsa 800 S. Tucker Drive Tulsa Oklahoma 74104 USA
| | - Zhiguo Wang
- Department of Chemistry and Biochemistry, The University of Tulsa 800 S. Tucker Drive Tulsa Oklahoma 74104 USA
| | - Bethany Hileman
- Department of Chemistry and Biochemistry, The University of Tulsa 800 S. Tucker Drive Tulsa Oklahoma 74104 USA
| | - Nisha Rajagopal
- Department of Chemistry and Biochemistry, The University of Tulsa 800 S. Tucker Drive Tulsa Oklahoma 74104 USA
| | - Syed R Hussaini
- Department of Chemistry and Biochemistry, The University of Tulsa 800 S. Tucker Drive Tulsa Oklahoma 74104 USA
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Takashima K, Okada T, Kato A, Yamasaki Y, Sugouchi T, Akanuma S, Kubo Y, Hosoya K, Morita H, Ito T, Kodama T, Tanabe G, Toyooka N. Divergent Synthesis of Decahydroquinoline‐Type Poison‐Frog Alkaloids. ChemistrySelect 2022. [DOI: 10.1002/slct.202104533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Katsuki Takashima
- Faculty of Engineering University of Toyama 3190 Gofuku Toyama 930–8555 Japan
| | - Takuya Okada
- Faculty of Engineering University of Toyama 3190 Gofuku Toyama 930–8555 Japan
- Graduate School of Innovative Life Science University of Toyama 3190 Gofuku Toyama 930–8555 Japan
| | - Atsushi Kato
- Department of Hospital Pharmacy University of Toyama 2630 Sugitani Toyama 930–0194 Japan
| | - Yuhei Yamasaki
- Faculty of Pharmaceutical Sciences University of Toyama 2630 Sugitani Toyama 930–0194 Japan
| | - Takeshi Sugouchi
- Faculty of Pharmaceutical Sciences University of Toyama 2630 Sugitani Toyama 930–0194 Japan
| | - Shin‐ichi Akanuma
- Faculty of Pharmaceutical Sciences University of Toyama 2630 Sugitani Toyama 930–0194 Japan
| | - Yoshiyuki Kubo
- Faculty of Pharmaceutical Sciences University of Toyama 2630 Sugitani Toyama 930–0194 Japan
| | - Ken‐ichi Hosoya
- Faculty of Pharmaceutical Sciences University of Toyama 2630 Sugitani Toyama 930–0194 Japan
| | - Hiroyuki Morita
- Institute of Natural Medicine University of Toyama 2630 Sugitani Toyama 930–0194 Japan
| | - Takuya Ito
- Institute of Natural Medicine University of Toyama 2630 Sugitani Toyama 930–0194 Japan
- Faculty of Pharmacy Osaka Ohtani University Tondabayashi Osaka 584–8540 Japan
| | - Takeshi Kodama
- Institute of Natural Medicine University of Toyama 2630 Sugitani Toyama 930–0194 Japan
| | - Genzoh Tanabe
- Faculty of Pharmacy Kindai University 3–4-1 Kowakae Higashi-osaka Osaka 577–8502 Japan
| | - Naoki Toyooka
- Faculty of Engineering University of Toyama 3190 Gofuku Toyama 930–8555 Japan
- Graduate School of Innovative Life Science University of Toyama 3190 Gofuku Toyama 930–8555 Japan
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Acquah FA, Paramel M, Kuta A, Hussaini SR, Wallace DR, Mooers BHM. Simulations of Promising Indolizidine- α6- β2 Nicotinic Acetylcholine Receptor Complexes. Int J Mol Sci 2021; 22:7934. [PMID: 34360698 PMCID: PMC8347036 DOI: 10.3390/ijms22157934] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 07/08/2021] [Accepted: 07/20/2021] [Indexed: 11/24/2022] Open
Abstract
Smoking-cessation drugs bind many off-target nicotinic acetylcholine receptors (nAChRs) and cause severe side effects if they are based on nicotine. New drugs that bind only those receptors, such as α6β2* nAChR, implicated in nicotine addiction would avoid the off-target binding. Indolizidine (-)-237D (IND (-)-237D), a bicyclic alkaloid, has been shown to block α6β2* containing nAChRs and functionally inhibit the nicotine-evoked dopamine release. To improve the affinity of indolizidine (-)-237D for α6β2*, we built a library of 2226 analogs. We screened virtually the library against a homology model of α6β2 nAChR that we derived from the recent crystal structure of α4β2 nAChR. We also screened the crystal structure of α4β2 nAChR as a control on specificity. We ranked the compounds based on their predicted free energy of binding. We selected the top eight compounds bound in their best pose and subjected the complexes to 100 ns molecular dynamics simulations to assess the stability of the complexes. All eight analogs formed stable complexes for the duration of the simulations. The results from this work highlight nine distinct analogs of IND (-)-237D with high affinity towards α6β2* nAChR. These leads can be synthesized and tested in in vitro and in vivo studies as lead candidates for drugs to treat nicotine addiction.
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Affiliation(s)
- Francis A. Acquah
- Department of Biochemistry and Molecular Biology, University of Oklahoma of Health Sciences Center, Oklahoma City, OK 73104, USA;
| | - Matthew Paramel
- Department of Chemistry and Biochemistry, The University of Tulsa, Tulsa, OK 74104, USA; (M.P.); (A.K.); (S.R.H.)
| | - Adama Kuta
- Department of Chemistry and Biochemistry, The University of Tulsa, Tulsa, OK 74104, USA; (M.P.); (A.K.); (S.R.H.)
| | - Syed R. Hussaini
- Department of Chemistry and Biochemistry, The University of Tulsa, Tulsa, OK 74104, USA; (M.P.); (A.K.); (S.R.H.)
| | - David R. Wallace
- Department of Pharmacology and Physiology, Oklahoma State University Center for Health Sciences, Tulsa, OK 74107, USA;
| | - Blaine H. M. Mooers
- Department of Biochemistry and Molecular Biology, University of Oklahoma of Health Sciences Center, Oklahoma City, OK 73104, USA;
- Peggy and Charles Stephenson Cancer Center, Oklahoma City, OK 73104, USA
- Laboratory of Biomolecular Structure and Function, University of Oklahoma of Health Sciences Center, Oklahoma City, OK 73104, USA
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You Y, Cui BD, Zhou MQ, Zuo J, Zhao JQ, Xu XY, Zhang XM, Yuan WC. Organocatalytic Asymmetric Michael/Friedel–Crafts Cascade Reaction of 3-Pyrrolyl-oxindoles and α,β-Unsaturated Aldehydes for the Construction of Chiral Spiro[5,6-dihydropyrido[1,2-a]pyrrole-3,3′-oxindoles]. J Org Chem 2015; 80:5951-7. [DOI: 10.1021/acs.joc.5b00597] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Yong You
- National
Engineering Research Center of Chiral Drugs, Chengdu Institute of
Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041, China
- University of Chinese Academy of Sciences, Beijing 10049, China
| | - Bao-Dong Cui
- School
of Pharmacy, Zunyi Medical University, Zunyi 563000, China
| | - Ming-Qiang Zhou
- National
Engineering Research Center of Chiral Drugs, Chengdu Institute of
Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041, China
- University of Chinese Academy of Sciences, Beijing 10049, China
| | - Jian Zuo
- National
Engineering Research Center of Chiral Drugs, Chengdu Institute of
Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041, China
- University of Chinese Academy of Sciences, Beijing 10049, China
| | - Jian-Qiang Zhao
- National
Engineering Research Center of Chiral Drugs, Chengdu Institute of
Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041, China
- University of Chinese Academy of Sciences, Beijing 10049, China
| | - Xiao-Ying Xu
- National
Engineering Research Center of Chiral Drugs, Chengdu Institute of
Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041, China
| | - Xiao-Mei Zhang
- National
Engineering Research Center of Chiral Drugs, Chengdu Institute of
Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041, China
| | - Wei-Cheng Yuan
- National
Engineering Research Center of Chiral Drugs, Chengdu Institute of
Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041, China
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Abstract
This review of simple indolizidine and quinolizidine alkaloids (i.e., those in which the parent bicyclic systems are in general not embedded in polycyclic arrays) is an update of the previous coverage in Volume 55 of this series (2001). The present survey covers the literature from mid-1999 to the end of 2013; and in addition to aspects of the isolation, characterization, and biological activity of the alkaloids, much emphasis is placed on their total synthesis. A brief introduction to the topic is followed by an overview of relevant alkaloids from fungal and microbial sources, among them slaframine, cyclizidine, Steptomyces metabolites, and the pantocins. The important iminosugar alkaloids lentiginosine, steviamine, swainsonine, castanospermine, and related hydroxyindolizidines are dealt with in the subsequent section. The fourth and fifth sections cover metabolites from terrestrial plants. Pertinent plant alkaloids bearing alkyl, functionalized alkyl or alkenyl substituents include dendroprimine, anibamine, simple alkaloids belonging to the genera Prosopis, Elaeocarpus, Lycopodium, and Poranthera, and bicyclic alkaloids of the lupin family. Plant alkaloids bearing aryl or heteroaryl substituents include ipalbidine and analogs, secophenanthroindolizidine and secophenanthroquinolizidine alkaloids (among them septicine, julandine, and analogs), ficuseptine, lasubines, and other simple quinolizidines of the Lythraceae, the simple furyl-substituted Nuphar alkaloids, and a mixed quinolizidine-quinazoline alkaloid. The penultimate section of the review deals with the sizable group of simple indolizidine and quinolizidine alkaloids isolated from, or detected in, ants, mites, and terrestrial amphibians, and includes an overview of the "dietary hypothesis" for the origin of the amphibian metabolites. The final section surveys relevant alkaloids from marine sources, and includes clathryimines and analogs, stellettamides, the clavepictines and pictamine, and bis(quinolizidine) alkaloids.
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Li YJ, Hou CC, Chang KC. Total Synthesis of Indolizidine Alkaloids (-)-167B, (-)-209I, and (-)-223A by Using a Common Tricyclic Lactone. European J Org Chem 2015. [DOI: 10.1002/ejoc.201500028] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Moemeni M, Arvinnezhad H, Samadi S, Salahi F, Jadidi K, Notash B. Highly Regioselective and Diastereoselective, One-Pot, Four-Component Synthesis of Novel Spiroindenoquinoxalineindolizidine Derivatives. J Heterocycl Chem 2014. [DOI: 10.1002/jhet.2121] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Mehdi Moemeni
- Department of Chemistry, Faculty of Sciences; Shahid Beheshti University; G. C., P.O. Box 1983963113 Tehran Iran
| | - Hamid Arvinnezhad
- Department of Chemistry, Faculty of Sciences; Shahid Beheshti University; G. C., P.O. Box 1983963113 Tehran Iran
| | - Saadi Samadi
- Department of Chemistry, Faculty of Sciences; Shahid Beheshti University; G. C., P.O. Box 1983963113 Tehran Iran
| | - Farbod Salahi
- Department of Chemistry, Faculty of Sciences; Shahid Beheshti University; G. C., P.O. Box 1983963113 Tehran Iran
| | - Khosrow Jadidi
- Department of Chemistry, Faculty of Sciences; Shahid Beheshti University; G. C., P.O. Box 1983963113 Tehran Iran
| | - Behrouz Notash
- Department of Chemistry, Faculty of Sciences; Shahid Beheshti University; G. C., P.O. Box 1983963113 Tehran Iran
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Abels F, Lindemann C, Schneider C. A General Strategy for the Catalytic, Highly Enantio- and Diastereoselective Synthesis of Indolizidine-Based Alkaloids. Chemistry 2014; 20:1964-79. [DOI: 10.1002/chem.201304086] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Indexed: 11/07/2022]
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Nickell JR, Grinevich VP, Siripurapu KB, Smith AM, Dwoskin LP. Potential therapeutic uses of mecamylamine and its stereoisomers. Pharmacol Biochem Behav 2013; 108:28-43. [PMID: 23603417 PMCID: PMC3690754 DOI: 10.1016/j.pbb.2013.04.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Revised: 04/01/2013] [Accepted: 04/03/2013] [Indexed: 12/17/2022]
Abstract
Mecamylamine (3-methylaminoisocamphane hydrochloride) is a nicotinic parasympathetic ganglionic blocker, originally utilized as a therapeutic agent to treat hypertension. Mecamylamine administration produces several deleterious side effects at therapeutically relevant doses. As such, mecamylamine's use as an antihypertensive agent was phased out, except in severe hypertension. Mecamylamine easily traverses the blood-brain barrier to reach the central nervous system (CNS), where it acts as a nicotinic acetylcholine receptor (nAChR) antagonist, inhibiting all known nAChR subtypes. Since nAChRs play a major role in numerous physiological and pathological processes, it is not surprising that mecamylamine has been evaluated for its potential therapeutic effects in a wide variety of CNS disorders, including addiction. Importantly, mecamylamine produces its therapeutic effects on the CNS at doses 3-fold lower than those used to treat hypertension, which diminishes the probability of peripheral side effects. This review focuses on the pharmacological properties of mecamylamine, the differential effects of its stereoisomers, S(+)- and R(-)-mecamylamine, and the potential for effectiveness in treating CNS disorders, including nicotine and alcohol addiction, mood disorders, cognitive impairment and attention deficit hyperactivity disorder.
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Affiliation(s)
- Justin R Nickell
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY 40536, USA.
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Dalton DM, Rappé AK, Rovis T. Perfluorinated Taddol Phosphoramidite as an L,Z-Ligand on Rh(I) and Co(-I): Evidence for Bidentate Coordination via Metal-C 6F 5 Interaction. Chem Sci 2013; 4:2062-2070. [PMID: 23671790 PMCID: PMC3650898 DOI: 10.1039/c3sc50271f] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Perfluorinated Taddol-based phosphoramidite, CKphos, is a highly selective ligand for formation of the vinylogous amide cycloadduct in the Rh(I) catalyzed [2+2+2] cycloaddition of alkenyl isocyanates and alkynes. CKphos overrides substrate bias of product selectivity in the cycloaddition, providing indolizinones in excellent product and enantioselectivities. Excellent selectivities are attributed to a shortened Rh-P bond and coordination of one C6F5 to rhodium via a Z-type interaction, making the phosphoramidite a bidentate L,Z-ligand on rhodium. Evidence for the shortened Rh-P and C6F5 coordination is provided by X-ray, NMR and DFT computation analyses. Additionally, an anionic cobalt complex with CKphos was synthesized and two Co-C6F5 interactions are seen. Rh(C2H4)Cl•CKphos catalyst in the [2+2+2] cycloaddition of alkenyl isocyanates and alkynes represents a rare example of metal-C6F5 Z-type interaction affecting selectivity in transition metal catalysis.
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Affiliation(s)
- Derek M. Dalton
- Department of Chemistry, Colorado State University, Fort Collins, CO 80526, USA
| | - Anthony K. Rappé
- Department of Chemistry, Colorado State University, Fort Collins, CO 80526, USA
| | - Tomislav Rovis
- Department of Chemistry, Colorado State University, Fort Collins, CO 80526, USA
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Tasso B, Novelli F, Sparatore F, Fasoli F, Gotti C. (+)-Laburnamine, a natural selective ligand and partial agonist for the α4β2 nicotinic receptor subtype. JOURNAL OF NATURAL PRODUCTS 2013; 76:727-731. [PMID: 23461628 DOI: 10.1021/np3007028] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
(+)-Laburnamine (1), a rare alkaloid extracted from Laburnum anagyroides seeds (∼4 mg from 1 kg), was shown to bind with high affinity (Ki, 293 nM) to the α4β2 nicotinic receptor subtype, which is, respectively, 126 and 136 times higher than to the α3β4 (Ki 37 μM) and α7 subtypes (Ki 40 μM). When its ability to release [(3)H]-dopamine from striatal slices was tested in a functional assay, compound 1 behaved as a partial agonist with an EC50 of 5.8 μM and an Emax that was 43% that of nicotine. When incubated with nicotine in the same assay, 1 prevented a maximal effect from being reached.
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Affiliation(s)
- Bruno Tasso
- Dipartimento di Farmacia, Università degli Studi di Genova, Viale Benedetto XV, 3, I-16132 Genova, Italy.
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Wang X, Tsuneki H, Urata N, Tezuka Y, Wada T, Sasaoka T, Sakai H, Saporito RA, Toyooka N. Synthesis and Biological Activities of the 3,5-Disubstituted Indolizidine Poison Frog Alkaloid 239Q and Its Congeners. European J Org Chem 2012. [DOI: 10.1002/ejoc.201200974] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Hone AJ, Scadden M, Gajewiak J, Christensen S, Lindstrom J, McIntosh JM. α-Conotoxin PeIA[S9H,V10A,E14N] potently and selectively blocks α6β2β3 versus α6β4 nicotinic acetylcholine receptors. Mol Pharmacol 2012; 82:972-82. [PMID: 22914547 DOI: 10.1124/mol.112.080853] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) containing α6 and β2 subunits modulate dopamine release in the basal ganglia and are therapeutically relevant targets for treatment of neurological and psychiatric disorders including Parkinson's disease and nicotine dependence. However, the expression profile of β2 and β4 subunits overlap in a variety of tissues including locus ceruleus, retina, hippocampus, dorsal root ganglia, and adrenal chromaffin cells. Ligands that bind α6β2 nAChRs also potently bind the closely related α6β4 subtype. To distinguish between these two subtypes, we synthesized novel analogs of a recently described α-conotoxin, PeIA. PeIA is a peptide antagonist that blocks several nAChR subtypes, including α6/α3β2β3 and α6/α3β4 nAChRs, with low nanomolar potency. We systematically mutated PeIA and evaluated the resulting analogs for enhanced potency and/or selectivity for α6/α3β2β3 nAChRs expressed in Xenopus oocytes (α6/α3 is a subunit chimera that contains the N-terminal ligand-binding domain of the α6 subunit). On the basis of these results, second-generation analogs were then synthesized. The final analog, PeIA[S9H,V10A,E14N], potently blocked acetylcholine-gated currents mediated by α6/α3β2β3 and α6/α3β4 nAChRs with IC(50) values of 223 pM and 65 nM, respectively, yielding a >290-fold separation between the two subtypes. Kinetic studies of ligand binding to α6/α3β2β3 nAChRs yielded a k(off) of 0.096 ± 0.001 min(-1) and a k(on) of 0.23 ± 0.019 min(-1) M(-9). The synthesis of PeIA[S9H,V10A,E14N] demonstrates that ligands can be developed to discriminate between α6β2 and α6β4 nAChRs.
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Affiliation(s)
- Arik J Hone
- Department of Biology, University of Utah, Salt Lake City, Utah, USA
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