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Kickinger S, Lie MEK, Suemasa A, Al-Khawaja A, Fujiwara K, Watanabe M, Wilhelmsen KS, Falk-Petersen CB, Frølund B, Shuto S, Ecker GF, Wellendorph P. Molecular Determinants and Pharmacological Analysis for a Class of Competitive Non-transported Bicyclic Inhibitors of the Betaine/GABA Transporter BGT1. Front Chem 2021; 9:736457. [PMID: 34595152 PMCID: PMC8476755 DOI: 10.3389/fchem.2021.736457] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 08/30/2021] [Indexed: 11/17/2022] Open
Abstract
The betaine/GABA transporter 1 (BGT1) is a member of the GABA transporter (GAT) family with still elusive function, largely due to a lack of potent and selective tool compounds. Based on modeling, we here present the design, synthesis and pharmacological evaluation of five novel conformationally restricted cyclic GABA analogs related to the previously reported highly potent and selective BGT1 inhibitor (1S,2S,5R)-5-aminobicyclo[3.1.0]hexane-2-carboxylic acid (bicyclo-GABA). Using [3H]GABA radioligand uptake assays at the four human GATs recombinantly expressed in mammalian cell lines, we identified bicyclo-GABA and its N-methylated analog (2) as the most potent and selective BGT1 inhibitors. Additional pharmacological characterization in a fluorescence-based membrane potential assay showed that bicyclo-GABA and 2 are competitive inhibitors, not substrates, at BGT1, which was validated by a Schild analysis for bicyclo-GABA (pKB value of 6.4). To further elaborate on the selectivity profile both compounds were tested at recombinant α1β2γ2 GABAA receptors. Whereas bicyclo-GABA showed low micromolar agonistic activity, the N-methylated 2 was completely devoid of activity at GABAA receptors. To further reveal the binding mode of bicyclo-GABA and 2 binding hypotheses of the compounds were obtained from in silico-guided mutagenesis studies followed by pharmacological evaluation at selected BGT1 mutants. This identified the non-conserved BGT1 residues Q299 and E52 as the molecular determinants driving BGT1 activity and selectivity. The binding mode of bicyclo-GABA was further validated by the introduction of activity into the corresponding GAT3 mutant L314Q (38 times potency increase cf. wildtype). Altogether, our data reveal the molecular determinants for the activity of bicyclic GABA analogs, that despite their small size act as competitive inhibitors of BGT1. These compounds may serve as valuable tools to selectively and potently target BGT1 in order to decipher its elusive pharmacological role in the brain and periphery such as the liver and kidneys.
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Affiliation(s)
- Stefanie Kickinger
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Department of Pharmaceutical Science, University of Vienna, Vienna, Austria
| | - Maria E K Lie
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Akihiro Suemasa
- Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Anas Al-Khawaja
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Koichi Fujiwara
- Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Mizuki Watanabe
- Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Kristine S Wilhelmsen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Christina B Falk-Petersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Bente Frølund
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Satoshi Shuto
- Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Gerhard F Ecker
- Department of Pharmaceutical Science, University of Vienna, Vienna, Austria
| | - Petrine Wellendorph
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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Suemasa A, Watanabe M, Kobayashi T, Suzuki H, Fukuda H, Minami M, Shuto S. Design and synthesis of cyclopropane-based conformationally restricted GABA analogues as selective inhibitors for betaine/GABA transporter 1. Bioorg Med Chem Lett 2018; 28:3395-3399. [DOI: 10.1016/j.bmcl.2018.08.031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2018] [Revised: 08/25/2018] [Accepted: 08/25/2018] [Indexed: 12/26/2022]
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Kobayashi T, Suemasa A, Igawa A, Ide S, Fukuda H, Abe H, Arisawa M, Minami M, Shuto S. Conformationally Restricted GABA with Bicyclo[3.1.0]hexane Backbone as the First Highly Selective BGT-1 Inhibitor. ACS Med Chem Lett 2014; 5:889-93. [PMID: 25147609 DOI: 10.1021/ml500134k] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 06/16/2014] [Indexed: 11/29/2022] Open
Abstract
On the basis of the three-dimensional diversity-oriented conformational restriction strategy using key chiral cyclopropane units, we previously identified 3 ((2S,3R)-4-amino-3,4-methanobutyric acid) with a chiral trans-cyclopropane structure as a γ-aminobutyric acid (GABA) transporter inhibitor selective for GABA transporter (GAT) subtypes GAT-3 and BGT-1 (betaine/GABA transporter-1). Further conformational restriction of 3 with the rigid bicyclo[3.1.0]hexane backbone led to the successful development of the first highly potent and selective BGT-1 inhibitor 4 (IC50 = 0.59 μM). The bioactive conformation of 3 for BGT-1 was also identified.
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Affiliation(s)
- Takaaki Kobayashi
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12,
Nishi-6, Kita-ku, Sapporo 060-0812, Japan
| | - Akihiro Suemasa
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12,
Nishi-6, Kita-ku, Sapporo 060-0812, Japan
| | - Arisa Igawa
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12,
Nishi-6, Kita-ku, Sapporo 060-0812, Japan
| | - Soichiro Ide
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12,
Nishi-6, Kita-ku, Sapporo 060-0812, Japan
| | - Hayato Fukuda
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12,
Nishi-6, Kita-ku, Sapporo 060-0812, Japan
| | - Hiroshi Abe
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12,
Nishi-6, Kita-ku, Sapporo 060-0812, Japan
| | - Mitsuhiro Arisawa
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12,
Nishi-6, Kita-ku, Sapporo 060-0812, Japan
| | - Masabumi Minami
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12,
Nishi-6, Kita-ku, Sapporo 060-0812, Japan
| | - Satoshi Shuto
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12,
Nishi-6, Kita-ku, Sapporo 060-0812, Japan
- Center for Research
and Education on Drug Discovery, Hokkaido University, Kita-ku, Sapporo 060-0812, Japan
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