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Janjic P, Solev D, Kocarev L. Non-trivial dynamics in a model of glial membrane voltage driven by open potassium pores. Biophys J 2023; 122:1470-1490. [PMID: 36919241 PMCID: PMC10147837 DOI: 10.1016/j.bpj.2023.03.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 02/01/2023] [Accepted: 03/07/2023] [Indexed: 03/16/2023] Open
Abstract
Despite the molecular evidence that a nearly linear steady-state current-voltage relationship in mammalian astrocytes reflects a total current resulting from more than one differentially regulated K+ conductance, detailed ordinary differential equation (ODE) models of membrane voltage Vm are still lacking. Various experimental results reporting altered rectification of the major Kir currents in glia, dominated by Kir4.1, have motivated us to develop a detailed model of Vm dynamics incorporating the weaker potassium K2P-TREK1 current in addition to Kir4.1, and study the stability of the resting state Vr. The main question is whether, with the loss of monotonicity in glial I-V curve resulting from altered Kir rectification, the nominal resting state Vr remains stable, and the cell retains the trivial, potassium electrode behavior with Vm after EK. The minimal two-dimensional model of Vm near Vr showed that an N-shape deformed Kir I-V curve induces multistability of Vm in a model that incorporates K2P activation kinetics, and nonspecific K+ leak currents. More specifically, an asymmetrical, nonlinear decrease of outward Kir4.1 conductance, turning the channels into inward rectifiers, introduces instability of Vr. That happens through a robust bifurcation giving birth to a second, more depolarized stable resting state Vdr > -10 mV. Realistic recordings from electrographic seizures were used to perturb the model. Simulations of the model perturbed by constant current through gap junctions and seizure-like discharges as local field potentials led to depolarization and switching of Vm between the two stable states, in a downstate-upstate manner. In the event of prolonged depolarizations near Vdr, such catastrophic instability would affect all aspects of the glial function, from metabolic support to membrane transport, and practically all neuromodulatory roles assigned to glia.
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Affiliation(s)
- Predrag Janjic
- Laboratory for Complex Systems and Networks, Research Centre for Computer Science and Information Technologies, Macedonian Academy of Sciences and Arts, Skopje, North Macedonia.
| | - Dimitar Solev
- Laboratory for Complex Systems and Networks, Research Centre for Computer Science and Information Technologies, Macedonian Academy of Sciences and Arts, Skopje, North Macedonia
| | - Ljupco Kocarev
- Laboratory for Complex Systems and Networks, Research Centre for Computer Science and Information Technologies, Macedonian Academy of Sciences and Arts, Skopje, North Macedonia
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Russell T, Gangotia D, Barry G. Assessing the potential of repurposing ion channel inhibitors to treat emerging viral diseases and the role of this host factor in virus replication. Biomed Pharmacother 2022; 156:113850. [DOI: 10.1016/j.biopha.2022.113850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 09/25/2022] [Accepted: 10/06/2022] [Indexed: 12/03/2022] Open
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Wang T, Xue P, Wang A, Yin M, Han J, Tang S, Liang R. Pore change during degradation of octreotide acetate-loaded PLGA microspheres: The effect of polymer blends. Eur J Pharm Sci 2019; 138:104990. [DOI: 10.1016/j.ejps.2019.104990] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 06/26/2019] [Accepted: 07/07/2019] [Indexed: 10/26/2022]
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Jorgensen C, Darré L, Oakes V, Torella R, Pryde D, Domene C. Lateral Fenestrations in K(+)-Channels Explored Using Molecular Dynamics Simulations. Mol Pharm 2016; 13:2263-73. [PMID: 27173896 DOI: 10.1021/acs.molpharmaceut.5b00942] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Potassium channels are of paramount physiological and pathological importance and therefore constitute significant drug targets. One of the keys to rationalize the way drugs modulate ion channels is to understand the ability of such small molecules to access their respective binding sites, from which they can exert an activating or inhibitory effect. Many computational studies have probed the energetics of ion permeation, and the mechanisms of voltage gating, but little is known about the role of fenestrations as possible mediators of drug entry in potassium channels. To explore the existence, structure, and conformational dynamics of transmembrane fenestrations accessible by drugs in potassium channels, molecular dynamics simulation trajectories were analyzed from three potassium channels: the open state voltage-gated channel Kv1.2, the G protein-gated inward rectifying channel GIRK2 (Kir3.2), and the human two-pore domain TWIK-1 (K2P1.1). The main results of this work were the identification of the sequence identity of four main lateral fenestrations of similar length and with bottleneck radius in the range of 0.9-2.4 Å for this set of potassium channels. It was found that the fenestrations in Kv1.2 and Kir3.2 remain closed to the passage of molecules larger than water. In contrast, in the TWIK-1 channel, both open and closed fenestrations are sampled throughout the simulation, with bottleneck radius shown to correlate with the random entry of lipid membrane molecules into the aperture of the fenestrations. Druggability scoring function analysis of the fenestration regions suggests that Kv and Kir channels studied are not druggable in practice due to steric constraining of the fenestration bottleneck. A high (>50%) fenestration sequence identity was found in each potassium channel subfamily studied, Kv1, Kir3, and K2P1. Finally, the reported fenestration sequence of TWIK-1 compared favorably with another channel, K2P channel TREK-2, reported to possess open fenestrations, suggesting that K2P channels could be druggable via fenestrations, for which we reported atomistic detail of the fenestration region, including the flexible residues M260 and L264 that interact with POPC membrane in a concerted fashion with the aperture and closure of the fenestrations.
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Affiliation(s)
- Christian Jorgensen
- Department of Chemistry, King's College London , Britannia House, 7 Trinity Street, London SE1 1DB, U.K
| | - Leonardo Darré
- Department of Chemistry, King's College London , Britannia House, 7 Trinity Street, London SE1 1DB, U.K
| | - Victoria Oakes
- Department of Chemistry, King's College London , Britannia House, 7 Trinity Street, London SE1 1DB, U.K
| | - Rubben Torella
- Pfizer Neuroscience and Pain Research Unit, Worldwide Medicinal Chemistry , Portway Building, Granta Park, Great Abington, Cambridge CB21 6GS, U.K
| | - David Pryde
- Pfizer Neuroscience and Pain Research Unit, Worldwide Medicinal Chemistry , Portway Building, Granta Park, Great Abington, Cambridge CB21 6GS, U.K
| | - Carmen Domene
- Department of Chemistry, King's College London , Britannia House, 7 Trinity Street, London SE1 1DB, U.K.,Chemistry Research Laboratory, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K
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