Molecular Determinants Underlying Delta Selective Compound 2 Activity at <i>δ</i>-Containing GABA<sub>A</sub> Receptors

Falk-Petersen, Christina Birkedahl; Rostrup, Frederik; Löffler, Rebekka; Buchleithner, Stine; Harpsøe, Kasper; Gloriam, David E.; Frølund, Bente; Wellendorph, Petrine

doi:10.1124/molpharm.121.000266

Cited by 3 publications

(3 citation statements)

References 54 publications

(74 reference statements)

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“…Presuming the primacy of δ‐GABA A Rs as the main neurosteroid target, a logical approach would be to develop a δ‐GABA A R selective PAM, as exemplified by DS2 59,63,64 . Although there is functional selectivity for both recombinant and native δ‐GABA A Rs, mutagenesis studies have highlighted key amino acid interaction sites with DS2 located not on the δ subunit per se, but instead residing in transmembrane pockets formed between the α subunit (Falk‐Petersen 2021 α4) and the β subunit 173 . Unfortunately, DS2 has limited brain penetration 64 but ongoing analogue studies may resolve this current limitation 174,175 .…”

Section: Exploring Therapeutic Opportunities Beyond Neurosteroidsmentioning

confidence: 99%

“…59,63,64 Although there is functional selectivity for both recombinant and native δ-GABA A Rs, mutagenesis studies have highlighted key amino acid interaction sites with DS2 located not on the δ subunit per se, but instead residing in transmembrane pockets formed between the α subunit (Falk-Petersen 2021 α4) and the β subunit. 173 Unfortunately, DS2 has limited brain penetration 64 but ongoing analogue studies may resolve this current limitation. 174,175 The development of brain penetrant δ-GABA A R selective compounds would be invaluable in clarifying the role of these receptors in the behavioural effects of neurosteroids but may additionally pave the way for novel small molecule therapeutics with an improved side effect profile.…”

Section: E Xploring Ther Apeuti C Opp Ortunitie S B E Yond Neuros Ter...mentioning

confidence: 99%

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Relating neurosteroid modulation of inhibitory neurotransmission to behaviour

Belelli

Phillips

Atack

et al. 2021

J Neuroendocrinology

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Studies in the 1980s revealed endogenous metabolites of progesterone and deoxycorticosterone to be potent, efficacious, positive allosteric modulators (PAMs) of the GABAA receptor (GABAAR). The discovery that such steroids are locally synthesised in the central nervous system (CNS) promoted the thesis that neural inhibition in the CNS may be “fine‐tuned” by these neurosteroids to influence behaviour. In preclinical studies, these neurosteroids exhibited anxiolytic, anticonvulsant, analgesic and sedative properties and, at relatively high doses, induced a state of general anaesthesia, a profile consistent with their interaction with GABAARs. However, realising the therapeutic potential of either endogenous neurosteroids or synthetic “neuroactive” steroids has proven challenging. Recent approval by the Food and Drug Administration of the use of allopregnanolone (brexanolone) to treat postpartum depression has rekindled enthusiasm for exploring their potential as new medicines. Although neurosteroids are selective for GABAARs, they exhibit little or no selectivity across the many GABAAR subtypes. Nevertheless, a relatively minor population of receptors incorporating the δ‐subunit (δ‐GABAARs) appears to be an important contributor to their behavioural effects. Here, we consider how neurosteroids acting upon GABAARs influence neuronal signalling, as well as how such effects may acutely and persistently influence behaviour, and explore the case for developing selective PAMs of δ‐GABAAR subtypes for the treatment of psychiatric disorders.

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Section: Exploring Therapeutic Opportunities Beyond Neurosteroidsmentioning

confidence: 99%

Section: E Xploring Ther Apeuti C Opp Ortunitie S B E Yond Neuros Ter...mentioning

confidence: 99%

Relating neurosteroid modulation of inhibitory neurotransmission to behaviour

Belelli

Phillips

Atack

et al. 2021

J Neuroendocrinology

View full text Add to dashboard Cite

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“…This was also observed with buffer (not shown) indicating that it is not related to bicyclo-GABA. Further, this is also a typical phenomenon in the FMP assay also for compounds completely dissolved (Falk-Petersen et al, 2021). Concentration-response curves for agonists were fitted using the four-parameter concentration-response model with GraphPad Prism as described by Falk- .…”

Section: Fmp Assaymentioning

confidence: 99%

Molecular Determinants and Pharmacological Analysis for a Class of Competitive Non-transported Bicyclic Inhibitors of the Betaine/GABA Transporter BGT1

et al. 2021

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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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Decreased extrasynaptic δ‐GABA_A receptors in PNN‐associated parvalbumin interneurons correlates with anxiety in APP and tau mouse models of Alzheimer's disease

Zhang,

Liu,

et al. 2024

British J Pharmacology

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BackgroundAlzheimer's disease (AD) is associated with gradual memory loss and anxiety which affects ~75% of AD patients. This study investigated whether AD‐associated anxiety correlated with modulation of extrasynaptic δ‐subunit‐containing GABAA receptors (δ‐GABAARs) in experimental mouse models of AD.Experimental approachWe combined behavioural experimental paradigms to measure cognition performance, and anxiety with neuroanatomy and molecular biology, using familial knock‐in (KI) mouse models of AD that harbour β‐amyloid (Aβ) precursor protein App (AppNL‐F) with or without humanized microtubule‐associated protein tau (MAPT), age‐matched to wild‐type control mice at three different age windows.ResultsAppNL‐F KI and AppNL‐F/MAPT AD models showed a similar magnitude of cognitive decline and elevated magnitude of anxiety correlated with neuroinflammatory hallmarks, including triggering receptor expressed on myeloid cells 2 (TREM2), reactive astrocytes and activated microglia consistent with accumulation of Aβ, tau and down‐regulation of Wnt/β‐catenin signalling compared to aged‐matched WT controls. In both the CA1 region of the hippocampus and dentate gyrus, there was an age‐dependent decline in the expression of δ‐GABAARs selectively expressed in parvalbumin (PV)‐expressing interneurons, encapsulated by perineuronal nets (PNNs) in the AD mouse models compared to WT mice.In vivo positive allosteric modulation of the δ‐GABAARs, using a δ‐selective‐compound DS2, decreased the level of anxiety in the AD mouse models, which was correlated with reduced hallmarks of neuroinflammation, and ‘normalisation’ of the expression of δ‐GABAARs.ConclusionsOur data show that the δ‐GABAARs could potentially be targeted for alleviating symptoms of anxiety, which would greatly improve the quality of life of AD individuals.

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Molecular Determinants Underlying Delta Selective Compound 2 Activity at δ-Containing GABA_A Receptors

Cited by 3 publications

References 54 publications

Relating neurosteroid modulation of inhibitory neurotransmission to behaviour

Relating neurosteroid modulation of inhibitory neurotransmission to behaviour

Molecular Determinants and Pharmacological Analysis for a Class of Competitive Non-transported Bicyclic Inhibitors of the Betaine/GABA Transporter BGT1

Decreased extrasynaptic δ‐GABA_A receptors in PNN‐associated parvalbumin interneurons correlates with anxiety in APP and tau mouse models of Alzheimer's disease

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Molecular Determinants Underlying Delta Selective Compound 2 Activity at δ-Containing GABAA Receptors

Cited by 3 publications

References 54 publications

Relating neurosteroid modulation of inhibitory neurotransmission to behaviour

Relating neurosteroid modulation of inhibitory neurotransmission to behaviour

Molecular Determinants and Pharmacological Analysis for a Class of Competitive Non-transported Bicyclic Inhibitors of the Betaine/GABA Transporter BGT1

Decreased extrasynaptic δ‐GABAA receptors in PNN‐associated parvalbumin interneurons correlates with anxiety in APP and tau mouse models of Alzheimer's disease

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Product

Resources

About

Molecular Determinants Underlying Delta Selective Compound 2 Activity at δ-Containing GABA_A Receptors

Decreased extrasynaptic δ‐GABA_A receptors in PNN‐associated parvalbumin interneurons correlates with anxiety in APP and tau mouse models of Alzheimer's disease