Dual activation of neuronal G protein-gated inwardly rectifying potassium (GIRK) channels by cholesterol and alcohol

Glaaser, Ian W.; Slesinger, Paul A.

doi:10.1038/s41598-017-04681-x

Cited by 42 publications

(61 citation statements)

References 70 publications

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“…The observed monoexponential decay curve was fit to a rate of K + conductance of 0.0098 ± 0.0002 s −1 . This rate is comparable to that observed for other K + channels using this assay (44). To further confirm the channel in POPC:POPG is not just exhibiting basal activity, we performed a series of assays as a function of the concentration of phosphatidylinositol 4,5-bisphosphate (PIP 2 ), a known inhibitor of KirBac1.1 (32,57).…”

Section: Resultssupporting

confidence: 75%

Conformational changes upon gating of KirBac1.1 into an open-activated state revealed by solid-state NMR and functional assays

Amani

Borcik

Khan

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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The conformational changes required for activation and K+ conduction in inward-rectifier K+ (Kir) channels are still debated. These structural changes are brought about by lipid binding. It is unclear how this process relates to fast gating or if the intracellular and extracellular regions of the protein are coupled. Here, we examine the structural details of KirBac1.1 reconstituted into both POPC and an activating lipid mixture of 3:2 POPC:POPG (wt/wt). KirBac1.1 is a prokaryotic Kir channel that shares homology with human Kir channels. We establish that KirBac1.1 is in a constitutively active state in POPC:POPG bilayers through the use of real-time fluorescence quenching assays and Förster resonance energy transfer (FRET) distance measurements. Multidimensional solid-state NMR (SSNMR) spectroscopy experiments reveal two different conformers within the transmembrane regions of the protein in this activating lipid environment, which are distinct from the conformation of the channel in POPC bilayers. The differences between these three distinct channel states highlight conformational changes associated with an open activation gate and suggest a unique allosteric pathway that ties the selectivity filter to the activation gate through interactions between both transmembrane helices, the turret, selectivity filter loop, and the pore helix. We also identify specific residues involved in this conformational exchange that are highly conserved among human Kir channels.

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Section: Resultssupporting

confidence: 75%

Conformational changes upon gating of KirBac1.1 into an open-activated state revealed by solid-state NMR and functional assays

Amani

Borcik

Khan

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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“…Although the residual current displayed slower deactivation kinetics that might presume involvement of ERG channels (Wang et al, 1998;Gustina and Trudeau, 2009;Larsen, 2010), addition of the ERG channel blocker E-4031 (10 M) to the bath and internal pipette solutions did not significantly alter that current amplitude (t (28) ϭ 0.6, p ϭ 0.55) nor the deactivation currents (t (28) ϭ 0.98, p ϭ 0.65, n ϭ 15 cells) in DGGCs ( Fig. 1 E, F ), perhaps suggesting another member of the EAG channel family that is insensitive to E-4031, such as Elk2 (KCNH3/K v 12.2) (Saganich et al, 2001;Gessner and Heinemann, 2003).…”

Section: Channels and Erg Channels Have Differential Fractional Conmentioning

confidence: 96%

Gq-coupled muscarinic receptor enhancement of KCNQ2/3 channels and activation of TRPC channels in multimodal control of excitability in dentate gyrus granule cells

Carver¹,

Shapiro²

2018

J. Neurosci.

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KCNQ (Kv7, "M-type") K ϩ channels and TRPC (transient receptor potential, "canonical") cation channels are coupled to neuronal discharge properties and are regulated via G q/11-protein-mediated signals. Stimulation of G q/11-coupled receptors both consumes phosphatidylinositol 4,5-bisphosphate (PIP 2) via phosphalipase C␤ hydrolysis and stimulates PIP 2 synthesis via rises in Ca 2ϩ i and other signals. Using brain-slice electrophysiology and Ca 2ϩ imaging from male and female mice, we characterized threshold K ϩ currents in dentate gyrus granule cells (DGGCs) and CA1 pyramidal cells, the effects of G q/11-coupled muscarinic M 1 acetylcholine (M 1 R) stimulation on M current and on neuronal discharge properties, and elucidated the intracellular signaling mechanisms involved. We observed disparate signaling cascades between DGGCs and CA1 neurons. DGGCs displayed M 1 R enhancement of M-current, rather than suppression, due to stimulation of PIP 2 synthesis, which was paralleled by increased PIP 2-gated G-protein coupled inwardly rectifying K ϩ currents as well. Deficiency of KCNQ2-containing M-channels ablated the M 1 R-induced enhancement of M-current in DGGCs. Simultaneously, M 1 R stimulation in DGGCs induced robust increases in [Ca 2ϩ ] i , mostly due to TRPC currents, consistent with, and contributing to, neuronal depolarization and hyperexcitability. CA1 neurons did not display such multimodal signaling, but rather M current was suppressed by M 1 R stimulation in these cells, similar to the previously described actions of M 1 R stimulation on M-current in peripheral ganglia that mostly involves PIP 2 depletion. Therefore, these results point to a pleiotropic network of cholinergic signals that direct cell-type-specific, precise control of hippocampal function with strong implications for hyperexcitability and epilepsy.

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“…Although the ethanol-bound population of GIRK is expected to be about 1.8%, assuming a blood ethanol concentration of 18 mM, which is relevant to human consumption (10), it has been proposed that a relatively small increase in the K + current could have a substantial effect on the membrane excitability of neurons, by lowering the equilibrium potential and drawing farther from the firing threshold (9). Furthermore, functional analyses of GIRK by Slesinger's group have suggested that the ethanolinduced activation of GIRK can be cooperatively potentiated by other activators of GIRK, such as PIP 2 and cholesterol, which are usually present in native cell membranes (15,22). Thus, the activated fraction of GIRK under physiological conditions is expected to be higher than that calculated using the in vitro K d value obtained from our NMR analyses.…”

Section: Discussionmentioning

confidence: 99%

“…Along with the βγ subunit of G protein (Gβγ) released upon the activation of G-protein-coupled receptors, ethanol is known to directly open GIRK. The opening of GIRK is invoked by ethanol at physiologically relevant concentrations (on the order of 10 −2 M, or 0.1% blood alcohol level), and behavioral studies have shown that weaver mutant mice, which have mutated GIRK with impaired K + selectivity, and GIRK knockout mice exhibited diminished ethanol-induced analgesia (8,10,(13)(14)(15). These observations indicate that the opening of GIRK by ethanol is closely related to the ethanol action in vivo.…”

mentioning

confidence: 94%

Structural basis for the ethanol action on G-protein–activated inwardly rectifying potassium channel 1 revealed by NMR spectroscopy

Toyama

Kano

Mase

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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Ethanol consumption leads to a wide range of pharmacological effects by acting on the signaling proteins in the human nervous system, such as ion channels. Despite its familiarity and biological importance, very little is known about the molecular mechanisms underlying the ethanol action, due to extremely weak binding affinity and the dynamic nature of the ethanol interaction. In this research, we focused on the primary in vivo target of ethanol, G-protein-activated inwardly rectifying potassium channel (GIRK), which is responsible for the ethanol-induced analgesia. By utilizing solution NMR spectroscopy, we characterized the changes in the structure and dynamics of GIRK induced by ethanol binding. We demonstrated here that ethanol binds to GIRK with an apparent dissociation constant of 1.0 M and that the actual physiological binding site of ethanol is located on the cavity formed between the neighboring cytoplasmic regions of the GIRK tetramer. From the methyl-based NMR relaxation analyses, we revealed that ethanol activates GIRK by shifting the conformational equilibrium processes, which are responsible for the gating of GIRK, to stabilize an open conformation of the cytoplasmic ion gate. We suggest that the dynamic molecular mechanism of the ethanol-induced activation of GIRK represents a general model of the ethanol action on signaling proteins in the human nervous system.

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Dual activation of neuronal G protein-gated inwardly rectifying potassium (GIRK) channels by cholesterol and alcohol

Cited by 42 publications

References 70 publications

Conformational changes upon gating of KirBac1.1 into an open-activated state revealed by solid-state NMR and functional assays

Conformational changes upon gating of KirBac1.1 into an open-activated state revealed by solid-state NMR and functional assays

Gq-coupled muscarinic receptor enhancement of KCNQ2/3 channels and activation of TRPC channels in multimodal control of excitability in dentate gyrus granule cells

Structural basis for the ethanol action on G-protein–activated inwardly rectifying potassium channel 1 revealed by NMR spectroscopy

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