1
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Mohamad FH, Mohamad Jamali MA, Che Has AT. Structure-function Studies of GABA (A) Receptors and Related computer-aided Studies. J Mol Neurosci 2023; 73:804-817. [PMID: 37750966 DOI: 10.1007/s12031-023-02158-3] [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] [Received: 08/03/2023] [Accepted: 09/12/2023] [Indexed: 09/27/2023]
Abstract
The γ-aminobutyric acid type A receptor (GABA (A) receptor) is a membrane protein activated by the neurotransmitter GABA. Structurally, this major inhibitory neurotransmitter receptor in the human central nervous system is a pentamer that can be built from a selection of 19 subunits consisting of α(1,2,3,4,5 or 6), β (1,2 or 3), γ (1,2 or 3), ρ (1,2 or 3), and δ, π, θ, and ε. This creates several possible pentameric arrangements, which also influence the pharmacological and physiological properties of the receptor. The complexity and heterogeneity of the receptors are further increased by the addition of short and long splice variants in several subunits and the existence of multiple allosteric binding sites and expansive ligands that can bind to the receptors. Therefore, a comprehensive understanding of the structure and function of the receptors is required to gain novel insights into the consequences of receptor dysfunction and subsequent drug development studies. Notably, advancements in computational-aided studies have facilitated the elucidation of residual interactions and exploring energy binding, which may otherwise be challenging to investigate. In this review, we aim to summarize the current understanding of the structure and function of GABA (A) receptors obtained from advancements in computational-aided applications.
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Affiliation(s)
- Fatin H Mohamad
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Health Campus, Kubang Kerian, 16150 Kota Bharu, Kelantan, Malaysia
| | - Muhamad Arif Mohamad Jamali
- Faculty of Science and Technology, Universiti Sains Islam Malaysia, Bandar Baru Nilai, 71800, Nilai, Negeri Sembilan, Malaysia
| | - Ahmad Tarmizi Che Has
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Health Campus, Kubang Kerian, 16150 Kota Bharu, Kelantan, Malaysia.
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2
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Pierce SR, Xu SQ, Germann AL, Steinbach JH, Akk G. Potentiation of the GABA AR reveals variable energetic contributions by etiocholanolone and propofol. Biophys J 2023:S0006-3495(23)00591-X. [PMID: 37752702 DOI: 10.1016/j.bpj.2023.09.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 09/14/2023] [Accepted: 09/21/2023] [Indexed: 09/28/2023] Open
Abstract
The properties of a potentiator are typically evaluated by measuring its ability to enhance the magnitude of the control response. Analysis of the ability of drugs to potentiate responses from receptor channels takes place in the context of particular models to extract parameters for functional effects. In the often-used coagonist model, the agonist generating control activity and the potentiator enhancing the control activity make additive energetic contributions to stabilize the active state of the receptor. The energetic contributions are fixed and, once known, enable calculation of predicted receptor behavior at any concentration combination of agonist and potentiator. Here, we have examined the applicability of the coagonist model by measuring the relationship between the magnitude of receptor potentiation and the level of background activity. Ternary αβγ GABAA receptors were activated by GABA or the allosteric agonist propofol, or by a gain-of-function mutation, and etiocholanolone- or propofol-mediated potentiation of peak responses was measured. We show that the free energy change contributed by the modulators etiocholanolone or propofol is reduced at higher levels of control activity, thereby being in disagreement with basic principles of the coagonist model. Possible mechanisms underlying this discrepancy are discussed.
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Affiliation(s)
- Spencer R Pierce
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri
| | - Sophia Q Xu
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri
| | - Allison L Germann
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri
| | - Joe Henry Steinbach
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri; The Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri
| | - Gustav Akk
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri; The Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri.
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3
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Kłopotowski K, Michałowski MA, Gos M, Mosiądz D, Czyżewska MM, Mozrzymas JW. Mutation of valine 53 at the interface between extracellular and transmembrane domains of the β 2 principal subunit affects the GABA A receptor gating. Eur J Pharmacol 2023; 947:175664. [PMID: 36934960 DOI: 10.1016/j.ejphar.2023.175664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 02/09/2023] [Accepted: 03/16/2023] [Indexed: 03/21/2023]
Abstract
GABAA receptors (gamma-aminobutyric acid type A receptors) are pentameric ligand-gated ion channels mediating inhibition in adult mammalian brains. Their static structure has been intensely studied in the past years but the underlying molecular activatory mechanisms remain obscure. The interface between extracellular and transmembrane domains has been recognized as a key player in the receptor gating. However, the role of the valine 53 in the β1-β2 loop of the principal subunit (β2) remains controversial showing differences compared to homologous residues in some cys-loop counterparts such as nAChR. To address the role of the β2V53 residue in the α1β2γ2L receptor gating, we performed high resolution macroscopic and single-channel recordings. To explore underlying molecular mechanisms a variety of substituting amino acids were investigated: Glutamate and Lysine (different electric charge), Alanine (aliphatic, larger than Valine) and Histidine (same residue as in homologous α1H55). We report that mutation of the β2V53 residue results in alterations of nearly all gating transitions including opening/closing, preactivation and desensitization. A dramatic gating impairment was observed for glutamate substitution (β2V53E) but β2V53K mutation had a weak effect. The impact of histidine substitution was also small while β2V53A markedly affected the receptor but to a smaller extent than β2V53E. Considering available structures in desensitized and bicuculline blocked shut states we propose that strongly detrimental effect of β2V53E mutation on receptor activation results from electrostatic interaction between the glutamate and β2K274 on the loop M2-M3 which stabilizes the receptor in the shut state. We conclude that β2V53 is strongly involved in mechanisms underlying the receptor gating.
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Affiliation(s)
- Karol Kłopotowski
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chałubińskiego 3a, Wrocław, Dolnośląskie, PL 50-368, Poland.
| | - Michał A Michałowski
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chałubińskiego 3a, Wrocław, Dolnośląskie, PL 50-368, Poland
| | - Michalina Gos
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chałubińskiego 3a, Wrocław, Dolnośląskie, PL 50-368, Poland; University of Wroclaw, Department of Molecular Physiology and Neurobiology, Sienkiewicza 21, Wrocław, Dolnośląskie, Pl 50-335, Poland
| | - Daniela Mosiądz
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chałubińskiego 3a, Wrocław, Dolnośląskie, PL 50-368, Poland
| | - Marta M Czyżewska
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chałubińskiego 3a, Wrocław, Dolnośląskie, PL 50-368, Poland
| | - Jerzy W Mozrzymas
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chałubińskiego 3a, Wrocław, Dolnośląskie, PL 50-368, Poland; University of Wroclaw, Department of Molecular Physiology and Neurobiology, Sienkiewicza 21, Wrocław, Dolnośląskie, Pl 50-335, Poland.
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4
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Kaczor PT, Michałowski MA, Mozrzymas JW. α 1 Proline 277 Residues Regulate GABA AR Gating through M2-M3 Loop Interaction in the Interface Region. ACS Chem Neurosci 2022; 13:3044-3056. [PMID: 36219829 PMCID: PMC9634794 DOI: 10.1021/acschemneuro.2c00401] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Cys-loop receptors are a superfamily of transmembrane, pentameric receptors that play a crucial role in mammalian CNS signaling. Physiological activation of these receptors is typically initiated by neurotransmitter binding to the orthosteric binding site, located at the extracellular domain (ECD), which leads to the opening of the channel pore (gate) at the transmembrane domain (TMD). Whereas considerable knowledge on molecular mechanisms of Cys-loop receptor activation was gathered for the acetylcholine receptor, little is known with this respect about the GABAA receptor (GABAAR), which mediates cellular inhibition. Importantly, several static structures of GABAAR were recently described, paving the way to more in-depth molecular functional studies. Moreover, it has been pointed out that the TMD-ECD interface region plays a crucial role in transduction of conformational changes from the ligand binding site to the channel gate. One of the interface structures implicated in this transduction process is the M2-M3 loop with a highly conserved proline (P277) residue. To address this issue specifically for α1β2γ2L GABAAR, we choose to substitute proline α1P277 with amino acids with different physicochemical features such as electrostatic charge or their ability to change the loop flexibility. To address the functional impact of these mutations, we performed macroscopic and single-channel patch-clamp analyses together with modeling. Our findings revealed that mutation of α1P277 weakly affected agonist binding but was critical for all transitions of GABAAR gating: opening/closing, preactivation, and desensitization. In conclusion, we provide evidence that conservative α1P277 at the interface is strongly involved in regulating the receptor gating.
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5
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Terejko K, Michałowski MA, Iżykowska I, Dominik A, Brzóstowicz A, Mozrzymas JW. Mutations at the M2 and M3 Transmembrane Helices of the GABA ARs α 1 and β 2 Subunits Affect Primarily Late Gating Transitions Including Opening/Closing and Desensitization. ACS Chem Neurosci 2021; 12:2421-2436. [PMID: 34101432 PMCID: PMC8291490 DOI: 10.1021/acschemneuro.1c00151] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
![]()
GABA type A receptors
(GABAARs) belong to the pentameric
ligand-gated ion channel (pLGIC) family and play a crucial role in
mediating inhibition in the adult mammalian brain. Recently, a major
progress in determining the static structure of GABAARs
was achieved, although precise molecular scenarios underlying conformational
transitions remain unclear. The ligand binding sites (LBSs) are located
at the extracellular domain (ECD), very distant from the receptor
gate at the channel pore. GABAAR gating is complex, comprising
three major categories of transitions: openings/closings, preactivation,
and desensitization. Interestingly, mutations at, e.g., the ligand
binding site affect not only binding but often also more than one
gating category, suggesting that structural determinants for distinct
conformational transitions are shared. Gielen and co-workers (2015)
proposed that the GABAAR desensitization gate is located
at the second and third transmembrane segment. However, studies of
our and others’ groups indicated that other parts of the GABAAR macromolecule might be involved in this process. In the
present study, we asked how selected point mutations (β2G254V, α1G258V, α1L300V,
and β2L296V) at the M2 and M3 transmembrane segments
affect gating transitions of the α1β2γ2 GABAAR. Using high resolution macroscopic
and single-channel recordings and analysis, we report that these substitutions,
besides affecting desensitization, also profoundly altered openings/closings,
having some minor effect on preactivation and agonist binding. Thus,
the M2 and M3 segments primarily control late gating transitions of
the receptor (desensitization, opening/closing), providing a further
support for the concept of diffuse gating mechanisms for conformational
transitions of GABAAR.
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Affiliation(s)
- Katarzyna Terejko
- Department of Biophysics and Neuroscience, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland
| | - Michał A. Michałowski
- Department of Biophysics and Neuroscience, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland
- Department of Molecular Physiology and Neurobiology, University of Wrocław, ul. Sienkiewicza 21, 50-335 Wrocław, Poland
| | - Ilona Iżykowska
- Department of Biophysics and Neuroscience, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland
| | - Anna Dominik
- Department of Biophysics and Neuroscience, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland
| | - Aleksandra Brzóstowicz
- Department of Biophysics and Neuroscience, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland
| | - Jerzy W. Mozrzymas
- Department of Biophysics and Neuroscience, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland
- Department of Molecular Physiology and Neurobiology, University of Wrocław, ul. Sienkiewicza 21, 50-335 Wrocław, Poland
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6
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Kaczor PT, Wolska AD, Mozrzymas JW. α 1 Subunit Histidine 55 at the Interface between Extracellular and Transmembrane Domains Affects Preactivation and Desensitization of the GABA A Receptor. ACS Chem Neurosci 2021; 12:562-572. [PMID: 33471498 PMCID: PMC7875458 DOI: 10.1021/acschemneuro.0c00781] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
![]()
The
GABAA receptor is a member of the Cys-loop family
and plays a crucial role in the adult mammalian brain inhibition.
Although the static structure of this receptor is emerging, the molecular
mechanisms underlying its conformational transitions remain elusive.
It is known that in the Cys-loop receptors, the interface between
extracellular and transmembrane domains plays a key role in transmitting
the “activation wave” down to the channel gate in the
pore. It has been previously reported that histidine 55 (H55), located
centrally at the interfacial β1−β2 loop of the
α1 subunit, is important in the receptor activation,
but it is unknown which specific gating steps it is affecting. In
the present study, we addressed this issue by taking advantage of
the state-of-the-art macroscopic and single-channel recordings together
with extensive modeling. Considering that H55 is known to affect the
local electrostatic landscape and because it is neighbored by two
negatively charged aspartates, a well conserved feature in the α
subunits, we considered substitution with negative (E) and positive
(K) residues. We found that these mutations markedly affected the
receptor gating, altering primarily preactivation and desensitization
transitions. Importantly, opposite effects were observed for these
two mutations strongly suggesting involvement of electrostatic interactions.
Single-channel recordings suggested also a minor effect on opening/closing
transitions which did not depend on the electric charge of the substituting
amino acid. Altogether, we demonstrate that H55 mutations affect primarily
preactivation and desensitization most likely by influencing local
electrostatic interactions at the receptor interface.
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Affiliation(s)
- Przemyslaw T. Kaczor
- Department of Biophysics and Neuroscience, Wroclaw Medical University, Chalubinskiego 3a, Wroclaw, Dolnoślaskie 50-368, Poland
| | - Aleksandra D. Wolska
- Department of Biophysics and Neuroscience, Wroclaw Medical University, Chalubinskiego 3a, Wroclaw, Dolnoślaskie 50-368, Poland
| | - Jerzy W. Mozrzymas
- Department of Biophysics and Neuroscience, Wroclaw Medical University, Chalubinskiego 3a, Wroclaw, Dolnoślaskie 50-368, Poland
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7
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Interaction between GABA A receptor α 1 and β 2 subunits at the N-terminal peripheral regions is crucial for receptor binding and gating. Biochem Pharmacol 2020; 183:114338. [PMID: 33189674 DOI: 10.1016/j.bcp.2020.114338] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 11/09/2020] [Accepted: 11/09/2020] [Indexed: 01/08/2023]
Abstract
Pentameric ligand gated ion channels (pLGICs) are crucial in electrochemical signaling but exact molecular mechanisms of their activation remain elusive. So far, major effort focused on the top-down molecular pathway between the ligand binding site and the channel gate. However, recent studies revealed that pLGIC activation is associated with coordinated subunit twisting in the membrane plane. This suggests a key role of intersubunit interactions but the underlying mechanisms remain largely unknown. Herein, we investigated a "peripheral" subunit interface region of GABAA receptor where structural modeling indicated interaction between N-terminal α1F14 and β2F31 residues. Our experiments underscored a crucial role of this interaction in ligand binding and gating, especially preactivation and opening, showing that the intersubunit cross-talk taking place outside (above) the top-down pathway can be strongly involved in receptor activation. Thus, described here intersubunit interaction appears to operate across a particularly long distance, affecting vast portions of the macromolecule.
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8
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Brodzki M, Michałowski MA, Gos M, Mozrzymas JW. Mutations of α 1F45 residue of GABA A receptor loop G reveal its involvement in agonist binding and channel opening/closing transitions. Biochem Pharmacol 2020; 177:113917. [PMID: 32194055 DOI: 10.1016/j.bcp.2020.113917] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 03/12/2020] [Indexed: 10/24/2022]
Abstract
GABAA receptors (GABAARs) mediate inhibitory neurotransmission in the mammalian brain. Recently, numerous GABAAR static structures have been published, but the molecular mechanisms of receptor activation remain elusive. Loop G is a rigid β-strand belonging to an extensive β-sheet that spans the regions involved in GABA binding and the interdomain interface which is important in receptor gating. It has been reported that loop G participates in ligand binding and gating of GABAARs, however, it remains unclear which specific gating transitions are controlled by this loop. Analysis of macroscopic responses revealed that mutation at the α1F45 residue (loop G midpoint) resulted in slower macroscopic desensitization and accelerated deactivation. Single-channel analysis revealed that these mutations also affected open and closed times distributions and reduced open probability. Kinetic modeling demonstrated that mutations affected primarily channel opening/closing and ligand binding with a minor effect on preactivation. Thus, α1F45 residue, in spite of its localization close to binding site, affects late gating transitions. In silico structural analysis suggested an important role of α1F45 residue in loop G stability and rigidity as well as in general structure of the binding site. We propose that the rigid β-sheet comprising loop G is well suited for long range communication within GABAAR but this mechanism becomes impaired when α1F45 is mutated. In conclusion, we demonstrate that loop G is crucial in controlling both binding and gating of GABAARs. These data shed new light on GABAAR activation mechanism and may also be helpful in designing clinically relevant modulators.
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Affiliation(s)
- Marek Brodzki
- University of Wrocław, Department of Molecular Physiology and Neurobiology, ul. Sienkiewicza 21, 50-335 Wrocław, Poland; Wrocław Medical University, Department of Biophysics, Laboratory of Neuroscience, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland.
| | - Michał A Michałowski
- University of Wrocław, Department of Molecular Physiology and Neurobiology, ul. Sienkiewicza 21, 50-335 Wrocław, Poland; Wrocław Medical University, Department of Biophysics, Laboratory of Neuroscience, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland.
| | - Michalina Gos
- University of Wrocław, Department of Molecular Physiology and Neurobiology, ul. Sienkiewicza 21, 50-335 Wrocław, Poland; Wrocław Medical University, Department of Biophysics, Laboratory of Neuroscience, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland
| | - Jerzy W Mozrzymas
- Wrocław Medical University, Department of Biophysics, Laboratory of Neuroscience, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland.
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Otsu Y, Donneger F, Schwartz EJ, Poncer JC. Cation-chloride cotransporters and the polarity of GABA signalling in mouse hippocampal parvalbumin interneurons. J Physiol 2020; 598:1865-1880. [PMID: 32012273 DOI: 10.1113/jp279221] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2019] [Accepted: 01/13/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Cation-chloride cotransporters (CCCs) play a critical role in controlling the efficacy and polarity of GABAA receptor (GABAA R)-mediated transmission in the brain, yet their expression and function in GABAergic interneurons has been overlooked. We compared the polarity of GABA signalling and the function of CCCs in mouse hippocampal pyramidal neurons and parvalbumin-expressing interneurons. Under resting conditions, GABAA R activation was mostly depolarizing and yet inhibitory in both cell types. KCC2 blockade further depolarized the reversal potential of GABAA R-mediated currents often above action potential threshold. However, during repetitive GABAA R activation, the postsynaptic response declined independently of the ion flux direction or KCC2 function, suggesting intracellular chloride build-up is not responsible for this form of plasticity. Our data demonstrate similar mechanisms of chloride regulation in mouse hippocampal pyramidal neurons and parvalbumin interneurons. ABSTRACT Transmembrane chloride gradients govern the efficacy and polarity of GABA signalling in neurons and are usually maintained by the activity of cation-chloride cotransporters, such as KCC2 and NKCC1. Whereas their role is well established in cortical principal neurons, it remains poorly documented in GABAergic interneurons. We used complementary electrophysiological approaches to compare the effects of GABAA receptor (GABAA R) activation in adult mouse hippocampal parvalbumin interneurons (PV-INs) and pyramidal cells (PCs). Loose cell-attached, tight-seal and gramicidin-perforated patch recordings all show GABAA R-mediated transmission is slightly depolarizing and yet inhibitory in both PV-INs and PCs. Focal GABA uncaging in whole-cell recordings reveal that KCC2 and NKCC1 are functional in both PV-INs and PCs but differentially contribute to transmembrane chloride gradients in their soma and dendrites. Blocking KCC2 function depolarizes the reversal potential of GABAA R-mediated currents in PV-INs and PCs, often beyond firing threshold, showing KCC2 is essential to maintain the inhibitory effect of GABAA Rs. Finally, we show that repetitive 10 Hz activation of GABAA Rs in both PV-INs and PCs leads to a progressive decline of the postsynaptic response independently of the ion flux direction or KCC2 function. This suggests intraneuronal chloride build-up may not predominantly contribute to activity-dependent plasticity of GABAergic synapses in this frequency range. Altogether our data demonstrate similar mechanisms of chloride regulation in mouse hippocampal PV-INs and PCs and suggest KCC2 downregulation in the pathology may affect the valence of GABA signalling in both cell types.
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Affiliation(s)
- Yo Otsu
- Inserm UMR-S 1270, 75005, Paris, France.,Sorbonne Université, F75005, Paris, France.,Institut du Fer à Moulin, F75005, Paris, France
| | - Florian Donneger
- Inserm UMR-S 1270, 75005, Paris, France.,Sorbonne Université, F75005, Paris, France.,Institut du Fer à Moulin, F75005, Paris, France
| | - Eric J Schwartz
- Inserm UMR-S 1270, 75005, Paris, France.,Sorbonne Université, F75005, Paris, France.,Institut du Fer à Moulin, F75005, Paris, France
| | - Jean Christophe Poncer
- Inserm UMR-S 1270, 75005, Paris, France.,Sorbonne Université, F75005, Paris, France.,Institut du Fer à Moulin, F75005, Paris, France
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10
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Jatczak-Śliwa M, Kisiel M, Czyzewska MM, Brodzki M, Mozrzymas JW. GABA A Receptor β 2E155 Residue Located at the Agonist-Binding Site Is Involved in the Receptor Gating. Front Cell Neurosci 2020; 14:2. [PMID: 32116555 PMCID: PMC7026498 DOI: 10.3389/fncel.2020.00002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Accepted: 01/06/2020] [Indexed: 12/02/2022] Open
Abstract
GABAA receptors (GABAARs) play a crucial role in mediating inhibition in the adult brain. In spite of progress in describing (mainly) the static structures of this receptor, the molecular mechanisms underlying its activation remain unclear. It is known that in the α1β2γ2L receptors, the mutation of the β2E155 residue, at the orthosteric binding site, strongly impairs the receptor activation, but the molecular and kinetic mechanisms of this effect remain elusive. Herein, we investigated the impact of the β2E155C mutation on binding and gating of the α1β2γ2L receptor. To this end, we combined the macroscopic and single-channel analysis, the use of different agonists [GABA and muscimol (MSC)] and flurazepam (FLU) as a modulator. As expected, the β2E155C mutation caused a vast right shift of the dose–response (for GABA and MSC) and, additionally, dramatic changes in the time course of current responses, indicative of alterations in gating. Mutated receptors showed reduced maximum open probability and enhanced receptor spontaneous activity. Model simulations for macroscopic currents revealed that the primary effect of the mutation was the downregulation of the preactivation (flipping) rate. Experiments with MSC and FLU further confirmed a reduction in the preactivation rate. Our single-channel analysis revealed the mutation impact mainly on the second component in the shut times distributions. Based on model simulations, this finding further confirms that this mutation affects mostly the preactivation transition, supporting thus the macroscopic data. Altogether, we provide new evidence that the β2E155 residue is involved in both binding and gating (primarily preactivation).
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Affiliation(s)
- Magdalena Jatczak-Śliwa
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland.,Department of Molecular Physiology and Neurobiology, University of Wrocław, Wrocław, Poland
| | - Magdalena Kisiel
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland
| | | | - Marek Brodzki
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland.,Department of Molecular Physiology and Neurobiology, University of Wrocław, Wrocław, Poland
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11
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Terejko K, Kaczor PT, Michałowski MA, Dąbrowska A, Mozrzymas JW. The C loop at the orthosteric binding site is critically involved in GABA A receptor gating. Neuropharmacology 2019; 166:107903. [PMID: 31972511 DOI: 10.1016/j.neuropharm.2019.107903] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 11/15/2019] [Accepted: 12/02/2019] [Indexed: 02/02/2023]
Abstract
GABAA receptors (GABAARs) play a crucial role in mammalian adult brain inhibition. The dysfunction of GABAergic drive is related to such disorders as epilepsy, schizophrenia, and depression. Substantial progress has recently been made in describing the static structure of GABAARs, but the molecular mechanisms that underlie the activation process remain elusive. The C loop of the GABAAR structure shows the largest movement upon ligand binding to the orthosteric binding site, a phenomenon that is referred to as "capping." The C loop is known to be involved in agonist binding, but its role in the gating of Cys-loop receptors is still debated. Herein, we investigated this issue by analyzing the impact of a β2F200 residue mutation of the C loop on gating properties of α1β2γ2 GABAARs. Extensive analyses and the modeling of current responses to saturating agonist application demonstrated that this mutation strongly affected preactivation, opening, closing and desensitization, i.e. all considered gating steps. Single-channel analysis revealed that the β2F200 mutation slowed all shut time components, and open times were shortened. Model fitting of these single-channel data further confirmed that the β2F200 mutation strongly affected all of the gating characteristics. We also found that this mutation altered receptor sensitivity to the benzodiazepine flurazepam, which was attributable to a change in preactivation kinetics. In silico analysis indicated that the β2F200 mutation resulted in distortion of the C loop structure, causing the movement of its tip from the binding site. Altogether, we provide the first evidence that C loop critically controls GABAAR gating.
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Affiliation(s)
- Katarzyna Terejko
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland.
| | - Przemysław T Kaczor
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland
| | - Michał A Michałowski
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland; Department of Molecular Physiology and Neurobiology, University of Wrocław, ul. Sienkiewicza 21, 50-335, Wrocław, Poland
| | - Agnieszka Dąbrowska
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland
| | - Jerzy W Mozrzymas
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland; Department of Molecular Physiology and Neurobiology, University of Wrocław, ul. Sienkiewicza 21, 50-335, Wrocław, Poland.
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12
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Kisiel M, Jatczak-Śliwa M, Mozrzymas JW. Protons modulate gating of recombinant α 1β 2γ 2 GABA A receptor by affecting desensitization and opening transitions. Neuropharmacology 2018; 146:300-315. [PMID: 30326242 DOI: 10.1016/j.neuropharm.2018.10.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 09/28/2018] [Accepted: 10/12/2018] [Indexed: 01/27/2023]
Abstract
Protons are potent modulators of GABAA receptors (GABAARs) and α1Phe64 residue was implicated in their pH sensitivity. Recently, we have demonstrated that this residue is involved in flipping transitions which precede channel opening. We thus re-addressed the mechanism of GABAAR modulation by protons by considering the gating scheme extended by flipping. The impact of pH changes was examined on currents mediated by wild-type α1β2γ2 receptors or by their α1Phe64Leu or α1Phe64Cys mutants and elicited by saturating concentrations of full (GABA) or partial (piperidine-4-sulfonic acid) agonists. To describe the impact of extracellular pH on receptor gating, we combined macroscopic analysis of currents elicited by rapid agonist applications with single-channel studies. Acidification (pH 6.0) increased current amplitudes (in the case of leucine mutants effect was stronger when P4S was used) and decreased the rate and the extent of desensitization whereas alkalization (pH 8.0) had the opposite but weaker effect. Deactivation kinetics for wild-type receptors was slowed down by acidification while in the case of mutants this effect was observed upon alkalization. Moreover, α1Phe64 mutations enhanced GABAAR sensitivity to alkaline pH. Single-channel analysis revealed that acidification prolonged burst durations and affected shut but not open time distributions. Model simulations for macroscopic and single-channel activity indicated a novel mechanism in which protons primarily affected opening and desensitization rates but not flipping/unflipping. This evidence for the impact of protons on the receptor gating together with previously demonstrated effect on the agonist binding, point to a complex effect of extracellular pH on GABAAR macromolecule.
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Affiliation(s)
- Magdalena Kisiel
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław 50-368, Poland.
| | - Magdalena Jatczak-Śliwa
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław 50-368, Poland; Department of Molecular Physiology and Neurobiology, Wrocław University, Wrocław 50-335, Poland
| | - Jerzy W Mozrzymas
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław 50-368, Poland.
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13
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Jatczak-Śliwa M, Terejko K, Brodzki M, Michałowski MA, Czyzewska MM, Nowicka JM, Andrzejczak A, Srinivasan R, Mozrzymas JW. Distinct Modulation of Spontaneous and GABA-Evoked Gating by Flurazepam Shapes Cross-Talk Between Agonist-Free and Liganded GABA A Receptor Activity. Front Cell Neurosci 2018; 12:237. [PMID: 30210295 PMCID: PMC6121034 DOI: 10.3389/fncel.2018.00237] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 07/17/2018] [Indexed: 11/13/2022] Open
Abstract
GABAA receptors (GABAARs) play a crucial inhibitory role in the CNS. Benzodiazepines (BDZs) are positive modulators of specific subtypes of GABAARs, but the underlying mechanism remains obscure. Early studies demonstrated the major impact of BDZs on binding and more recent investigations indicated gating, but it is unclear which transitions are affected. Moreover, the upregulation of GABAAR spontaneous activity by BDZs indicates their impact on receptor gating but the underlying mechanisms remain unknown. Herein, we investigated the effect of a BDZ (flurazepam) on the spontaneous and GABA-induced activity for wild-type (WT, α1β2γ2) and mutated (at the orthosteric binding site α1F64) GABAARs. Surprisingly, in spite of the localization at the binding site, these mutations increased the spontaneous activity. Flurazepam (FLU) upregulated this activity for mutants and WT receptors to a similar extent by affecting opening/closing transitions. Spontaneous activity affected GABA-evoked currents and is manifested as an overshoot after agonist removal that depended on the modulation by BDZs. We explain the mechanism of this phenomenon as a cross-desensitization of ligand-activated and spontaneously active receptors. Moreover, due to spontaneous activity, FLU-pretreatment and co-application (agonist + FLU) protocols yielded distinct results. We provide also the first evidence that GABAAR may enter the desensitized state in the absence of GABA in a FLU-dependent manner. Based on our data and model simulations, we propose that FLU affects agonist-induced gating by modifying primarily preactivation and desensitization. We conclude that the mechanisms of modulation of spontaneous and ligand-activated GABAAR activity concerns gating but distinct transitions are affected in spontaneous and agonist-evoked activity.
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Affiliation(s)
- Magdalena Jatczak-Śliwa
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland.,Department of Molecular Physiology and Neurobiology, University of Wrocław, Wrocław, Poland
| | - Katarzyna Terejko
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland
| | - Marek Brodzki
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland.,Department of Molecular Physiology and Neurobiology, University of Wrocław, Wrocław, Poland
| | - Michał A Michałowski
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland.,Department of Molecular Physiology and Neurobiology, University of Wrocław, Wrocław, Poland
| | - Marta M Czyzewska
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland
| | - Joanna M Nowicka
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland
| | - Anna Andrzejczak
- Department of Molecular Physiology and Neurobiology, University of Wrocław, Wrocław, Poland
| | | | - Jerzy W Mozrzymas
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland
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14
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Irwin JJ, Gaskins G, Sterling T, Mysinger MM, Keiser MJ. Predicted Biological Activity of Purchasable Chemical Space. J Chem Inf Model 2017; 58:148-164. [PMID: 29193970 PMCID: PMC5780839 DOI: 10.1021/acs.jcim.7b00316] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
![]()
Whereas
400 million distinct compounds are now purchasable within
the span of a few weeks, the biological activities of most are unknown.
To facilitate access to new chemistry for biology, we have combined
the Similarity Ensemble Approach (SEA) with the maximum Tanimoto similarity
to the nearest bioactive to predict activity for every commercially
available molecule in ZINC. This method, which we label SEA+TC, outperforms
both SEA and a naïve-Bayesian classifier via predictive performance
on a 5-fold cross-validation of ChEMBL’s bioactivity data set
(version 21). Using this method, predictions for over 40% of compounds
(>160 million) have either high significance (pSEA ≥ 40),
high
similarity (ECFP4MaxTc ≥ 0.4), or both, for one or more of
1382 targets well described by ligands in the literature. Using a
further 1347 less-well-described targets, we predict activities for
an additional 11 million compounds. To gauge whether these predictions
are sensible, we investigate 75 predictions for 50 drugs lacking a
binding affinity annotation in ChEMBL. The 535 million predictions
for over 171 million compounds at 2629 targets are linked to purchasing
information and evidence to support each prediction and are freely
available via https://zinc15.docking.org and https://files.docking.org.
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Affiliation(s)
- John J Irwin
- Department of Pharmaceutical Chemistry, University of California, San Francisco , Byers Hall, 1700 4th Street, San Francisco, California 94158-2330, United States
| | - Garrett Gaskins
- Department of Pharmaceutical Chemistry, University of California, San Francisco , Byers Hall, 1700 4th Street, San Francisco, California 94158-2330, United States.,Institute for Neurodegenerative Diseases, University of California, San Francisco , 675 Nelson Rising Lane, San Francisco, California 94158, United States.,Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco , Byers Hall, 1700 4th Street, San Francisco, California 94158, United States.,Institute for Computational Health Sciences, University of California, San Francisco , 550 16th Street, San Francisco, California 94158, United States
| | - Teague Sterling
- Department of Pharmaceutical Chemistry, University of California, San Francisco , Byers Hall, 1700 4th Street, San Francisco, California 94158-2330, United States
| | - Michael M Mysinger
- Department of Pharmaceutical Chemistry, University of California, San Francisco , Byers Hall, 1700 4th Street, San Francisco, California 94158-2330, United States
| | - Michael J Keiser
- Department of Pharmaceutical Chemistry, University of California, San Francisco , Byers Hall, 1700 4th Street, San Francisco, California 94158-2330, United States.,Institute for Neurodegenerative Diseases, University of California, San Francisco , 675 Nelson Rising Lane, San Francisco, California 94158, United States.,Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco , Byers Hall, 1700 4th Street, San Francisco, California 94158, United States.,Institute for Computational Health Sciences, University of California, San Francisco , 550 16th Street, San Francisco, California 94158, United States
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15
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Kisiel M, Jatczak M, Brodzki M, Mozrzymas JW. Spontaneous activity, singly bound states and the impact of alpha 1Phe64 mutation on GABA AR gating in the novel kinetic model based on the single-channel recordings. Neuropharmacology 2017; 131:453-474. [PMID: 29162430 DOI: 10.1016/j.neuropharm.2017.11.030] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Revised: 10/25/2017] [Accepted: 11/17/2017] [Indexed: 12/31/2022]
Abstract
GABAA receptor is the primary mediator of inhibition in the adult mammalian brain. Our recent studies revealed that a classic gating scheme for GABAAR needed to be updated with an intermediate step (flipping) and that the α1Phe64 mutation at the GABA binding site affects this transition. However, description of flipping at the single-channel level remains incomplete. In particular, its role in singly-bound and spontaneous activity remains unknown. We have performed thus single-channel recordings over wide range of agonist concentration for wild-type α1β2γ2L receptors and α1Phe64 mutants. For WT receptors we observed relatively frequent brief spontaneous openings which were also present at low [GABA]. However, closed times distributions for spontaneous activity and at low [GABA] were clearly different indicating that a proportion of short-lived openings were due to liganded, most likely singly bound receptors. Increasing [GABA] resulted in prolongation of bursts and increased occurrence of bursts with long openings and short closures. Mutations of α1Phe64 residue dramatically affected the open and closed time distributions at high and saturating [GABA], especially in the case of cysteine mutants. However, this mutation weakly affected spontaneous or singly bound activity. Model fitting of our single-channel data led us to propose a novel and, to our knowledge, most complete GABAAR kinetic model in which flipping occurs in singly and doubly bound states. However, spontaneous activity did not reveal involvement of flipping. Moreover, we report that α1Phe64 mutation affects not only the flipping but also the opening/closing transitions indicating its generalized impact on the receptor gating.
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Affiliation(s)
- Magdalena Kisiel
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław 50-368, Poland.
| | - Magdalena Jatczak
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław 50-368, Poland; Department of Physiology and Molecular Neurobiology, Wrocław University, Wrocław 50-335, Poland
| | - Marek Brodzki
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław 50-368, Poland; Department of Physiology and Molecular Neurobiology, Wrocław University, Wrocław 50-335, Poland
| | - Jerzy W Mozrzymas
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław 50-368, Poland.
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