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Inderwiedenstraße L, Kienitz MC. Angiotensin receptors and α 1B-adrenergic receptors regulate native IK (ACh) and phosphorylation-deficient GIRK4 (S418A) channels through different PKC isoforms. Pflugers Arch 2024; 476:1041-1064. [PMID: 38658400 DOI: 10.1007/s00424-024-02966-5] [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: 02/27/2024] [Revised: 04/03/2024] [Accepted: 04/17/2024] [Indexed: 04/26/2024]
Abstract
Signaling of G protein-activated inwardly rectifying K+ (GIRK) channels is an important mechanism of the parasympathetic regulation of the heart rate and cardiac excitability. GIRK channels are inhibited during stimulation of Gq-coupled receptors (GqPCRs) by depletion of phosphatidyl-4,5-bisphosphate (PIP2) and/or channel phosphorylation by protein kinase C (PKC). The GqPCR-dependent modulation of GIRK currents in terms of specific PKC isoform activation was analyzed in voltage-clamp experiments in rat atrial myocytes and in CHO or HEK 293 cells. By using specific PKC inhibitors, we identified the receptor-activated PKC isoforms that contribute to phenylephrine- and angiotensin-induced GIRK channel inhibition. We demonstrate that the cPKC isoform PKCα significantly contributes to GIRK inhibition during stimulation of wildtype α1B-adrenergic receptors (α1B-ARs). Deletion of the α1B-AR serine residues S396 and S400 results in a preferential regulation of GIRK activity by PKCβ. As a novel finding, we report that the AT1-receptor-induced GIRK inhibition depends on the activation of the nPKC isoform PKCε whereas PKCα and PKCβ do not mainly participate in the angiotensin-mediated GIRK reduction. Expression of the dominant negative (DN) PKCε prolonged the onset of GIRK inhibition and significantly reduced AT1-R desensitization, indicating that PKCε regulates both GIRK channel activity and the strength of the receptor signal via a negative feedback mechanism. The serine residue S418 represents an important phosphorylation site for PKCε in the GIRK4 subunit. To analyze the functional impact of this PKC phosphorylation site for receptor-specific GIRK channel modulation, we monitored the activity of a phosphorylation-deficient (GIRK4 (S418A)) GIRK4 channel mutant during stimulation of α1B-ARs or AT1-receptors. Mutation of S418 did not impede α1B-AR-mediated GIRK inhibition, suggesting that S418 within the GIRK4 subunit is not subject to PKCα-induced phosphorylation. Furthermore, activation of angiotensin receptors induced pronounced GIRK4 (S418A) channel inhibition, excluding that this phosphorylation site contributes to the AT1-R-induced GIRK reduction. Instead, phosphorylation of S418 has a facilitative effect on GIRK activity that was abolished in the GIRK4 (S418A) mutant. To summarize, the present study shows that the receptor-dependent regulation of atrial GIRK channels is attributed to the GqPCR-specific activation of different PKC isoforms. Receptor-specific activated PKC isoforms target distinct phosphorylation sites within the GIRK4 subunit, resulting in differential regulation of GIRK channel activity with either facilitative or inhibitory effects on GIRK currents.
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Affiliation(s)
- Leonie Inderwiedenstraße
- Department for Cellular and Translational Physiology, Institute of Physiology, Ruhr University Bochum, Universitätsstrasse 150, 44801, Bochum, Germany
| | - Marie-Cécile Kienitz
- Department for Cellular and Translational Physiology, Institute of Physiology, Ruhr University Bochum, Universitätsstrasse 150, 44801, Bochum, Germany.
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2
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Boyle CA, Lei S. Neuromedin B excites central lateral amygdala neurons and reduces cardiovascular output and fear-potentiated startle. J Cell Physiol 2023; 238:1381-1404. [PMID: 37186390 PMCID: PMC10330072 DOI: 10.1002/jcp.31020] [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: 10/26/2022] [Revised: 03/27/2023] [Accepted: 03/28/2023] [Indexed: 05/17/2023]
Abstract
Neuromedin B (NMB) and gastrin-releasing peptide (GRP) are the two mammalian analogs in the bombesin peptide family that exert a variety of actions including emotional processing, appetitive behaviors, cognition, and tumor growth. The bombesin-like peptides interact with three receptors: the NMB-preferring bombesin 1 (BB1) receptors, the GRP-preferring bombesin 2 (BB2) receptors and the orphan bombesin 3 (BB3) receptors. Whereas, injection of bombesin into the central amygdala reduces satiety and modulates blood pressure, the underlying cellular and molecular mechanisms have not been determined. As administration of bombesin induces the expression of Fos in the lateral nucleus of the central amygdala (CeL) which expresses BB1 receptors, we probed the effects of NMB on CeL neurons using in vitro and in vivo approaches. We showed that activation of the BB1 receptors increased action potential firing frequency recorded from CeL neurons via inhibition of the inwardly rectifying K+ (Kir) channels. Activities of phospholipase Cβ and protein kinase C were required, whereas intracellular Ca2+ release was unnecessary for BB1 receptor-elicited potentiation of neuronal excitability. Application of NMB directly into the CeA reduced blood pressure and heart rate and significantly reduced fear-potentiated startle. We may provide a cellular and molecular mechanism whereby bombesin-like peptides modulate anxiety and fear responses in the amygdala.
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Affiliation(s)
- Cody A. Boyle
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND 58203, USA
| | - Saobo Lei
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND 58203, USA
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3
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Gada KD, Chang M, Chandrashekar A, Plant LD, Noujaim SF, Logothetis DE. Mechanism of PKCε regulation of cardiac GIRK channel gating. Proc Natl Acad Sci U S A 2023; 120:e2212325120. [PMID: 36584301 PMCID: PMC9910474 DOI: 10.1073/pnas.2212325120] [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: 07/18/2022] [Accepted: 11/09/2022] [Indexed: 12/31/2022] Open
Abstract
G-protein-gated inwardly rectifying potassium (GIRK) channel activity is regulated by the membrane phospholipid, phosphatidylinositol-4,5-bisphosphate (PI 4,5P2). Constitutive activity of cardiac GIRK channels in atrial myocytes, that is implicated in atrial fibrillation (AF), is mediated via a protein kinase C-ε (PKCε)-dependent mechanism. The novel PKC isoform, PKCε, is reported to enhance the activity of cardiac GIRK channels. Here, we report that PKCε stimulation leads to activation of GIRK channels in mouse atria and in human stem cell-derived atrial cardiomyocytes (iPSCs). We identified residue GIRK4(S418) which when mutated to Ala abolished, or to Glu, mimicked the effects of PKCε on GIRK currents. PKCε strengthened the interactions of the cardiac GIRK isoforms, GIRK4 and GIRK1/4 with PIP2, an effect that was reversed in the GIRK4(S418A) mutant. This mechanistic insight into the PKCε-mediated increase in channel activity because of GIRK4(S418) phosphorylation, provides a precise druggable target to reverse AF-related pathologies due to GIRK overactivity.
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Affiliation(s)
- Kirin D. Gada
- Department of Pharmaceutical Sciences, Bouvé College of Health Sciences and College of Science, Northeastern University, Boston, MA02115
| | - Mengmeng Chang
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL33602
| | - Aishwarya Chandrashekar
- Department of Pharmaceutical Sciences, Bouvé College of Health Sciences and College of Science, Northeastern University, Boston, MA02115
| | - Leigh D. Plant
- Department of Pharmaceutical Sciences, Bouvé College of Health Sciences and College of Science, Northeastern University, Boston, MA02115
- Center for Drug Discovery, Bouvé College of Health Sciences and College of Science, Northeastern University, Boston, MA02115
| | - Sami F. Noujaim
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL33602
| | - Diomedes E. Logothetis
- Department of Pharmaceutical Sciences, Bouvé College of Health Sciences and College of Science, Northeastern University, Boston, MA02115
- Center for Drug Discovery, Bouvé College of Health Sciences and College of Science, Northeastern University, Boston, MA02115
- Department of Chemistry and Chemical Biology, Bouvé College of Health Sciences and College of Science, Northeastern University, Boston, MA02115
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Shostak DM, Constantin S, Flannery J, Wray S. Acetylcholine regulation of GnRH neuronal activity: A circuit in the medial septum. Front Endocrinol (Lausanne) 2023; 14:1147554. [PMID: 36950690 PMCID: PMC10025473 DOI: 10.3389/fendo.2023.1147554] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 02/22/2023] [Indexed: 03/08/2023] Open
Abstract
In vertebrates, gonadotropin-releasing hormone (GnRH)-secreting neurons control fertility by regulating gonadotrophs in the anterior pituitary. While it is known that acetylcholine (ACh) influences GnRH secretion, whether the effect is direct or indirect, and the specific ACh receptor (AChR) subtype(s) involved remain unclear. Here, we determined 1) whether ACh can modulate GnRH cellular activity and 2) a source of ACh afferents contacting GnRH neurons. Calcium imaging was used to assay GnRH neuronal activity. With GABAergic and glutamatergic transmission blocked, subtype-specific AChR agonists and antagonists were applied to identify direct regulation of GnRH neurons. ACh and nicotine caused a rise in calcium that declined gradually back to baseline after 5-6 min. This response was mimicked by an alpha3-specific agonist. In contrast, muscarine inhibited GnRH calcium oscillations, and blocking M2 and M4 together prevented this inhibition. Labeling for choline acetyltransferase (ChAT) and GnRH revealed ChAT fibers contacting GnRH neurons, primarily in the medial septum (MS), and in greater number in females than males. ChAT positive cells in the MS are known to express p75NGFRs. Labeling for p75NGFR, ChAT and GnRH indicated that ChAT fibers contacting GnRH cells originate from cholinergic cells within these same rostral areas. Together, these results indicate that cholinergic cells in septal areas can directly regulate GnRH neurons.
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Boyle CA, Hu B, Quaintance KL, Mastrud MR, Lei S. Ionic signalling mechanisms involved in neurokinin-3 receptor-mediated augmentation of fear-potentiated startle response in the basolateral amygdala. J Physiol 2022; 600:4325-4345. [PMID: 36030507 PMCID: PMC9529888 DOI: 10.1113/jp283433] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 08/15/2022] [Indexed: 09/10/2023] Open
Abstract
The tachykinin peptides include substance P (SP), neurokinin A and neurokinin B, which interact with three G-protein-coupled neurokinin receptors, NK1Rs, NK2Rs and NK3Rs, respectively. Whereas high densities of NK3Rs have been detected in the basolateral amygdala (BLA), the functions of NK3Rs in this brain region have not been determined. We found that activation of NK3Rs by application of the selective agonist, senktide, persistently excited BLA principal neurons. NK3R-elicited excitation of BLA neurons was mediated by activation of a non-selective cation channel and depression of the inwardly rectifying K+ (Kir) channels. With selective channel blockers and knockout mice, we further showed that NK3R activation excited BLA neurons by depressing the G protein-activated inwardly rectifying K+ (GIRK) channels and activating TRPC4 and TRPC5 channels. The effects of NK3Rs required the functions of phospholipase Cβ (PLCβ), but were independent of intracellular Ca2+ release and protein kinase C. PLCβ-mediated depletion of phosphatidylinositol 4,5-bisphosphate was involved in NK3R-induced excitation of BLA neurons. Microinjection of senktide into the BLA of rats augmented fear-potentiated startle (FPS) and this effect was blocked by prior injection of the selective NK3R antagonist SB 218795, suggesting that activation of NK3Rs in the BLA increased FPS. We further showed that TRPC4/5 and GIRK channels were involved in NK3R-elicited facilitation of FPS. Our results provide a cellular and molecular mechanism whereby NK3R activation excites BLA neurons and enhances FPS. KEY POINTS: Activation of NK3 receptors (NK3Rs) facilitates the excitability of principal neurons in rat basolateral amygdala (BLA). NK3R-induced excitation is mediated by inhibition of GIRK channels and activation of TRPC4/5 channels. Phospholipase Cβ and depletion of phosphatidylinositol 4,5-bisphosphate are necessary for NK3R-mediated excitation of BLA principal neurons. Activation of NK3Rs in the BLA facilitates fear-potentiated startle response. GIRK channels and TRPC4/5 channels are involved in NK3R-mediated augmentation of fear-potentiated startle.
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Affiliation(s)
- Cody A. Boyle
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND58203, USA
| | - Binqi Hu
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND58203, USA
| | - Kati L. Quaintance
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND58203, USA
| | - Morgan R. Mastrud
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND58203, USA
| | - Saobo Lei
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND58203, USA
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6
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Luo H, Marron Fernandez de Velasco E, Wickman K. Neuronal G protein-gated K + channels. Am J Physiol Cell Physiol 2022; 323:C439-C460. [PMID: 35704701 PMCID: PMC9362898 DOI: 10.1152/ajpcell.00102.2022] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
G protein-gated inwardly rectifying K+ (GIRK/Kir3) channels exert a critical inhibitory influence on neurons. Neuronal GIRK channels mediate the G protein-dependent, direct/postsynaptic inhibitory effect of many neurotransmitters including γ-aminobutyric acid (GABA), serotonin, dopamine, adenosine, somatostatin, and enkephalin. In addition to their complex regulation by G proteins, neuronal GIRK channel activity is sensitive to PIP2, phosphorylation, regulator of G protein signaling (RGS) proteins, intracellular Na+ and Ca2+, and cholesterol. The application of genetic and viral manipulations in rodent models, together with recent progress in the development of GIRK channel modulators, has increased our understanding of the physiological and behavioral impact of neuronal GIRK channels. Work in rodent models has also revealed that neuronal GIRK channel activity is modified, transiently or persistently, by various stimuli including exposure drugs of abuse, changes in neuronal activity patterns, and aversive experience. A growing body of preclinical and clinical evidence suggests that dysregulation of GIRK channel activity contributes to neurological diseases and disorders. The primary goals of this review are to highlight fundamental principles of neuronal GIRK channel biology, mechanisms of GIRK channel regulation and plasticity, the nascent landscape of GIRK channel pharmacology, and the potential relevance of GIRK channels to the pathophysiology and treatment of neurological diseases and disorders.
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Affiliation(s)
- Haichang Luo
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, United States
| | | | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, United States
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7
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PKC regulation of ion channels: The involvement of PIP 2. J Biol Chem 2022; 298:102035. [PMID: 35588786 PMCID: PMC9198471 DOI: 10.1016/j.jbc.2022.102035] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 05/10/2022] [Accepted: 05/11/2022] [Indexed: 11/24/2022] Open
Abstract
Ion channels are integral membrane proteins whose gating has been increasingly shown to depend on the presence of the low-abundance membrane phospholipid, phosphatidylinositol (4,5) bisphosphate. The expression and function of ion channels is tightly regulated via protein phosphorylation by specific kinases, including various PKC isoforms. Several channels have further been shown to be regulated by PKC through altered surface expression, probability of channel opening, shifts in voltage dependence of their activation, or changes in inactivation or desensitization. In this review, we survey the impact of phosphorylation of various ion channels by PKC isoforms and examine the dependence of phosphorylated ion channels on phosphatidylinositol (4,5) bisphosphate as a mechanistic endpoint to control channel gating.
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8
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Qiao P, Schrecke S, Lyu J, Zhu Y, Zhang T, Benavides A, Laganowsky A. Insight into the Phospholipid-Binding Preferences of Kir3.4. Biochemistry 2021; 60:3813-3821. [PMID: 34846128 DOI: 10.1021/acs.biochem.1c00615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The G-protein-gated inwardly rectifying potassium channel 4 (Kir3.4) subunit forms functional tetramers. Previous studies have established that phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) is required for Kir3.4 function. However, the binding preferences of Kir3.4 for the headgroup and acyl chains of phosphorylated phosphatidylinositides (PIPs) and other lipids are not well understood. Here, the interactions between full-length, human Kir3.4 and lipids are characterized using native mass spectrometry (MS) in conjunction with a soluble fluorescent lipid-binding assay. Kir3.4 displays binding preferences for PIPs, and, in some cases, the degree of binding is influenced by the type of acyl chains. The interactions between Kir3.4 and PIPs are weaker in comparison to full-length, human Kir3.2. The binding of PI(4,5)P2 modified with a fluorophore to Kir3.2 can be enhanced by other lipids, such as phosphatidylcholine. Introduction of S143T, a mutation that enhances Kir3.4 activity, results in an overall reduction in the channel binding PIPs. In contrast, the D223N mutant of Kir3.4 that mimics the sodium-bound state exhibited stronger binding for PI(4,5)P2, particularly for those with 18:0-20:4 acyl chains. Taken together, these results provide additional insight into the interaction between Kir3.4 and lipids that are important for channel function.
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Affiliation(s)
- Pei Qiao
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, United States
| | - Samantha Schrecke
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Jixing Lyu
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Yun Zhu
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Tianqi Zhang
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Amanda Benavides
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Arthur Laganowsky
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
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Hu B, Boyle CA, Lei S. Roles of PLCβ, PIP 2 , and GIRK channels in arginine vasopressin-elicited excitation of CA1 pyramidal neurons. J Cell Physiol 2021; 237:660-674. [PMID: 34287874 DOI: 10.1002/jcp.30535] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 06/29/2021] [Accepted: 07/09/2021] [Indexed: 12/15/2022]
Abstract
Arginine vasopressin (AVP) is a hormone exerting vasoconstrictive and antidiuretic action in the periphery and serves as a neuromodulator in the brain. Although the hippocampus receives vasopressinergic innervation and AVP has been shown to facilitate the excitability of CA1 pyramidal neurons, the involved ionic and signaling mechanisms have not been determined. Here we found that AVP excited CA1 pyramidal neurons by activation of V1a receptors. Functions of G proteins and phospholipase Cβ (PLCβ) were required for AVP-elicited excitation of CA1 pyramidal neurons, whereas intracellular Ca2+ release and protein kinase C were unnecessary. PLCβ-mediated depletion of phosphatidylinositol 4,5-bisphosphate (PIP2 ) was required for AVP-elicited excitation of CA1 pyramidal neurons. AVP augmented the input resistance and increased the time constants of CA1 pyramidal neurons. AVP induced an inward current in K+ -containing intracellular solution, whereas no inward currents were observed with Cs+ -containing intracellular solution. AVP-sensitive currents showed inward rectification with a reversal potential close to the K+ reversal potential, suggesting the involvement of inwardly rectifying K+ channels. AVP-induced currents were sensitive to the micromolar concentration of Ba2+ and tertiapin-Q, whereas application of ML 133, a selective Kir2 channel blocker had no effects, suggesting that AVP excited CA1 pyramidal neurons by depressing G protein-gated inwardly rectifying K+ channels. Activation of V1a receptors in the CA1 region facilitated glutamatergic transmission onto subicular pyramidal neurons, suggesting that AVP modulates network activity in the brain. Our results may provide one of the cellular and molecular mechanisms to explain the in vivo physiological functions of AVP.
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Affiliation(s)
- Binqi Hu
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota, USA
| | - Cody A Boyle
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota, USA
| | - Saobo Lei
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota, USA
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Lei S, Hu B. Ionic and signaling mechanisms involved in neurotensin-mediated excitation of central amygdala neurons. Neuropharmacology 2021; 196:108714. [PMID: 34271017 DOI: 10.1016/j.neuropharm.2021.108714] [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: 04/29/2021] [Revised: 07/05/2021] [Accepted: 07/09/2021] [Indexed: 10/20/2022]
Abstract
Neurotensin (NT) serves as a neuromodulator in the brain where it regulates a variety of physiological functions. Whereas the central amygdala (CeA) expresses NT peptide and NTS1 receptors and application of NT has been shown to excite CeA neurons, the underlying cellular and molecular mechanisms have not been determined. We found that activation of NTS1 receptors increased the neuronal excitability of the lateral nucleus (CeL) of CeA. Both phospholipase Cβ (PLCβ) and phosphatidylinositol 4,5-bisphosphate (PIP2) depletion were required, whereas intracellular Ca2+ release and PKC were unnecessary for NT-elicited excitation of CeL neurons. NT increased the input resistance and time constants of CeL neurons, suggesting that NT excites CeL neurons by decreasing a membrane conductance. Depressions of the inwardly rectifying K+ (Kir) channels including both the Kir2 subfamily and the GIRK channels were required for NT-elicited excitation of CeL neurons. Activation of NTS1 receptors in the CeL led to GABAergic inhibition of medial nucleus of CeA neurons, suggesting that NT modulates the network activity in the amygdala. Our results may provide a cellular and molecular mechanism to explain the physiological functions of NT in vivo.
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Affiliation(s)
- Saobo Lei
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND58203, USA.
| | - Binqi Hu
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND58203, USA
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Lei S, Hu B, Rezagholizadeh N. Activation of V 1a vasopressin receptors excite subicular pyramidal neurons by activating TRPV1 and depressing GIRK channels. Neuropharmacology 2021; 190:108565. [PMID: 33891950 DOI: 10.1016/j.neuropharm.2021.108565] [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: 01/05/2021] [Revised: 03/04/2021] [Accepted: 04/06/2021] [Indexed: 11/25/2022]
Abstract
Arginine vasopressin (AVP) is a nonapeptide that serves as a neuromodulator in the brain and a hormone in the periphery that regulates water homeostasis and vasoconstriction. The subiculum is the major output region of the hippocampus and an integral component in the networks that processes sensory and motor cues to form a cognitive map encoding spatial, contextual, and emotional information. Whereas the subiculum expresses high densities of AVP-binding sites and AVP has been shown to increase the synaptic excitability of subicular pyramidal neurons, the underlying cellular and molecular mechanisms have not been determined. We found that activation of V1a receptors increased the excitability of subicular pyramidal neurons via activation of TRPV1 channels and depression of the GIRK channels. V1a receptor-induced excitation of subicular pyramidal neurons required the function of phospholipase Cβ, but was independent of intracellular Ca2+ release. Protein kinase C was responsible for AVP-mediated depression of GIRK channels, whereas degradation of phosphatidylinositol 4,5-bisphosphate was involved in V1a receptor-elicited activation of TRPV1 channels. Our results may provide one of the cellular and molecular mechanisms to explain the physiological functions of AVP in the brain.
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Affiliation(s)
- Saobo Lei
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, 58203, USA.
| | - Binqi Hu
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, 58203, USA
| | - Neda Rezagholizadeh
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, 58203, USA
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12
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Therapeutic potential of targeting G protein-gated inwardly rectifying potassium (GIRK) channels in the central nervous system. Pharmacol Ther 2021; 223:107808. [PMID: 33476640 DOI: 10.1016/j.pharmthera.2021.107808] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Accepted: 01/05/2021] [Indexed: 12/15/2022]
Abstract
G protein-gated inwardly rectifying potassium channels (Kir3/GirK) are important for maintaining resting membrane potential, cell excitability and inhibitory neurotransmission. Coupled to numerous G protein-coupled receptors (GPCRs), they mediate the effects of many neurotransmitters, neuromodulators and hormones contributing to the general homeostasis and particular synaptic plasticity processes, learning, memory and pain signaling. A growing number of behavioral and genetic studies suggest a critical role for the appropriate functioning of the central nervous system, as well as their involvement in many neurologic and psychiatric conditions, such as neurodegenerative diseases, mood disorders, attention deficit hyperactivity disorder, schizophrenia, epilepsy, alcoholism and drug addiction. Hence, GirK channels emerge as a very promising tool to be targeted in the current scenario where these conditions already are or will become a global public health problem. This review examines recent findings on the physiology, function, dysfunction, and pharmacology of GirK channels in the central nervous system and highlights the relevance of GirK channels as a worthful potential target to improve therapies for related diseases.
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13
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Hu B, Boyle CA, Lei S. Oxytocin receptors excite lateral nucleus of central amygdala by phospholipase Cβ- and protein kinase C-dependent depression of inwardly rectifying K + channels. J Physiol 2020; 598:3501-3520. [PMID: 32458437 DOI: 10.1113/jp279457] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 05/21/2020] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS Activation of oxytocin receptors (OXTRs) facilitates neuronal excitability in rat lateral nucleus of central amygdala (CeL). OXTR-induced excitation is mediated by inhibition of inwardly rectifying K+ (Kir) channels. Phospholipase Cβ is necessary for OXTR-mediated excitation of CeL neurons and depression of Kir channels. OXTR-elicited depression of Kir channels and excitation of CeL neurons require the function of Ca2+ -dependent protein kinase C. ABSTRACT Oxytocin (OXT) is a nonapeptide that exerts anxiolytic effects in the brain. The amygdala is an important structure involved in the modulation of fear and anxiety. A high density of OXT receptors (OXTRs) has been detected in the capsular (CeC) and lateral (CeL) nucleus of the central amygdala (CeA). Previous studies have demonstrated that activation of OXTRs induces remarkable increases in neuronal excitability in the CeL/C. However, the signalling and ionic mechanisms underlying OXTR-induced facilitation of neuronal excitability have not been determined. We found that activation of OXTRs in the CeL increased action potential firing frequency recorded from neurons in this region via inhibition of the inwardly rectifying K+ channels. The functions of phospholipase Cβ and protein kinase C were required for OXTR-induced augmentation of neuronal excitability. Our results provide a cellular and molecular mechanism whereby activation of OXTRs exerts anxiolytic effects.
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Affiliation(s)
- Binqi Hu
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND58203, USA
| | - Cody A Boyle
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND58203, USA
| | - Saobo Lei
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND58203, USA
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14
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Yan R, Chen R, Wang J, Shi J, dos Santos WF, Xu Z, Liu L. Jingshu Keli and its Components Notoginsenoside R1 and Ginsenoside Rb1 Alleviate the Symptoms of Cervical Myelopathy through Kir3.1 Mediated Mechanisms. CNS & NEUROLOGICAL DISORDERS-DRUG TARGETS 2019; 18:631-642. [DOI: 10.2174/0929866526666190911150514] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 06/20/2018] [Accepted: 05/06/2019] [Indexed: 12/16/2022]
Abstract
Background & Objective::
Cervical Spondylotic Myelopathy (CSM) is one of the most serious
spinal cord disorders in adults. Pharmacological modulation of ion channels is a common strategy
to interfere with CSM and prevent neuronal damage.
Methods:
Here, we investigated the effects of Jingshu Keli (JSKL), a traditional Chinese herbal formula,
on CSM-related gait abnormality, mechanical allodynia and thermal hyperalgesia, and assessed
the neuronal mechanisms of JSKL on cultured brainstem cells. Behavioral tests and patch clamp recordings
were performed to make this assessment.
Results:
In our study, we found that JSKL significantly recovered the gait performance (P<0.001) and
decreased the levels of mechanical pain in 18.9% (P<0.01) and thermal pain in 18.1% (P<0.05). Further
investigation suggested that JSKL and its containing ginsenoside Rb1 (GRb1), notoginsenoside
R1 (NGR1) reduced the action potential frequency in 38.5%, 27.2%, 25.9%, and hyperpolarized resting
membrane potential in 15.0%, 13.8%, 12.1%, respectively. Kir channels, not KV channels and KCa
channels, were the major intermediate factors achieving treatment effects. Finally, immunostaining results
showed that the phosphorylation of Kir3.1 was promoted, whereas the total expression level did
not change.
Conclusion:
Our study reveals a novel strategy of treating CSM by using Traditional Chinese Medicines
(TCMs) containing active components.
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Affiliation(s)
- Renjie Yan
- State Key Laboratory of New Drug and Pharmaceutical Process, Shanghai Institute of Pharmaceutical Industry, Jingan District, Shanghai, China; State Institute of Pharmaceutical Industry, Shanghai 200437, China
| | - Rui Chen
- State Key Laboratory of New Drug and Pharmaceutical Process, Shanghai Institute of Pharmaceutical Industry, Jingan District, Shanghai, China; State Institute of Pharmaceutical Industry, Shanghai 200437, China
| | - Jiahui Wang
- State Key Laboratory of New Drug and Pharmaceutical Process, Shanghai Institute of Pharmaceutical Industry, Jingan District, Shanghai, China; State Institute of Pharmaceutical Industry, Shanghai 200437, China
| | - Jian Shi
- Institute of Cardiovascular and Metabolic Medicine, School of Medicine, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Wagner Ferreira dos Santos
- Laboratory of Neurobiology and Venoms, Department of Biology, FFCLRP, University of Sao Paulo, Sao Paulo, Brazil
| | - Zhiru Xu
- State Key Laboratory of New Drug and Pharmaceutical Process, Shanghai Institute of Pharmaceutical Industry, Jingan District, Shanghai, China; State Institute of Pharmaceutical Industry, Shanghai 200437, China
| | - Li Liu
- State Key Laboratory of New Drug and Pharmaceutical Process, Shanghai Institute of Pharmaceutical Industry, Jingan District, Shanghai, China; State Institute of Pharmaceutical Industry, Shanghai 200437, China
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15
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Niemeyer A, Rinne A, Kienitz MC. Receptor-specific regulation of atrial GIRK channel activity by different Ca2+-dependent PKC isoforms. Cell Signal 2019; 64:109418. [DOI: 10.1016/j.cellsig.2019.109418] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Revised: 09/11/2019] [Accepted: 09/11/2019] [Indexed: 12/23/2022]
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16
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Li D, Jin T, Gazgalis D, Cui M, Logothetis DE. On the mechanism of GIRK2 channel gating by phosphatidylinositol bisphosphate, sodium, and the Gβγ dimer. J Biol Chem 2019; 294:18934-18948. [PMID: 31659119 DOI: 10.1074/jbc.ra119.010047] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 10/21/2019] [Indexed: 12/19/2022] Open
Abstract
G protein-gated inwardly rectifying K+ (GIRK) channels belong to the inward-rectifier K+ (Kir) family, are abundantly expressed in the heart and the brain, and require that phosphatidylinositol bisphosphate is present so that intracellular channel-gating regulators such as Gβγ and Na+ ions can maintain the channel-open state. However, despite high-resolution structures (GIRK2) and a large number of functional studies, we do not have a coherent picture of how Gβγ and Na+ ions control gating of GIRK2 channels. Here, we utilized computational modeling and all-atom microsecond-scale molecular dynamics simulations to determine which gates are controlled by Na+ and Gβγ and how each regulator uses the channel domain movements to control gate transitions. We found that Na+ ions control the cytosolic gate of the channel through an anti-clockwise rotation, whereas Gβγ stabilizes the transmembrane gate in the open state through a rocking movement of the cytosolic domain. Both effects alter the way in which the channel interacts with phosphatidylinositol bisphosphate and thereby stabilizes the open states of the respective gates. These studies of GIRK channel dynamics present for the first time a comprehensive structural model that is consistent with the great body of literature on GIRK channel function.
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Affiliation(s)
- Dailin Li
- Key Laboratory of Environmental Biotechnology, Fujian Province University, Xiamen University of Technology, Xiamen, 361024 China; Department of Pharmaceutical Sciences, Northeastern University School of Pharmacy, Bouve College of Health Sciences, Boston, Massachusetts 02115.
| | - Taihao Jin
- Department of Pharmaceutical Sciences, Northeastern University School of Pharmacy, Bouve College of Health Sciences, Boston, Massachusetts 02115
| | - Dimitris Gazgalis
- Department of Pharmaceutical Sciences, Northeastern University School of Pharmacy, Bouve College of Health Sciences, Boston, Massachusetts 02115
| | - Meng Cui
- Department of Pharmaceutical Sciences, Northeastern University School of Pharmacy, Bouve College of Health Sciences, Boston, Massachusetts 02115
| | - Diomedes E Logothetis
- Department of Pharmaceutical Sciences, Northeastern University School of Pharmacy, Bouve College of Health Sciences, Boston, Massachusetts 02115.
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17
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Chen IS, Liu C, Tateyama M, Karbat I, Uesugi M, Reuveny E, Kubo Y. Non-sedating antihistamines block G-protein-gated inwardly rectifying K + channels. Br J Pharmacol 2019; 176:3161-3179. [PMID: 31116876 DOI: 10.1111/bph.14717] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 04/19/2019] [Accepted: 05/02/2019] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND AND PURPOSE A second-generation antihistamine, terfenadine, is known to induce arrhythmia by blocking hERG channels. In this study, we have shown that terfenadine also inhibits the activity of G-protein-gated inwardly rectifying K+ (GIRK) channels, which regulate the excitability of neurons and cardiomyocytes. To clarify the underlying mechanism(s), we examined the effects of several antihistamines on GIRK channels and identified the structural determinant for the inhibition. EXPERIMENTAL APPROACH Electrophysiological recordings were made in Xenopus oocytes and rat atrial myocytes to analyse the effects of antihistamines on various GIRK subunits (Kir 3.x). Mutagenesis analyses identified the residues critical for inhibition by terfenadine and the regulation of ion selectivity. The potential docking site of terfenadine was analysed by molecular docking. KEY RESULTS GIRK channels containing Kir 3.1 subunits heterologously expressed in oocytes and native GIRK channels in atrial myocytes were inhibited by terfenadine and other non-sedating antihistamines. In Kir 3.1 subunits, mutation of Phe137, located in the centre of the pore helix, to the corresponding Ser in Kir 3.2 subunits reduced the inhibition by terfenadine. Introduction of an amino acid with a large side chain in Kir 3.2 subunits at Ser148 increased the inhibition. When this residue was mutated to a non-polar amino acid, the channel became permeable to Na+ . Phosphoinositide-mediated activity was also decreased by terfenadine. CONCLUSION AND IMPLICATIONS The Phe137 residue in Kir 3.1 subunits is critical for inhibition by terfenadine. This study provides novel insights into the regulation of GIRK channels by the pore helix and information for drug design.
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Affiliation(s)
- I-Shan Chen
- Division of Biophysics and Neurobiology, Department of Molecular and Cellular Physiology, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Japan.,Department of Physiological Sciences, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Japan
| | - Chang Liu
- Division of Biophysics and Neurobiology, Department of Molecular and Cellular Physiology, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Japan.,Department of Physiological Sciences, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Japan
| | - Michihiro Tateyama
- Division of Biophysics and Neurobiology, Department of Molecular and Cellular Physiology, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Japan.,Department of Physiological Sciences, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Japan
| | - Izhar Karbat
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Motonari Uesugi
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Uji, Japan.,Institute for Chemical Research, Kyoto University, Uji, Japan
| | - Eitan Reuveny
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Yoshihiro Kubo
- Division of Biophysics and Neurobiology, Department of Molecular and Cellular Physiology, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Japan.,Department of Physiological Sciences, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Japan
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18
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Kienitz MC, Niemeyer A, König GM, Kostenis E, Pott L, Rinne A. Biased signaling of Ca 2+-sensing receptors in cardiac myocytes regulates GIRK channel activity. J Mol Cell Cardiol 2019; 130:107-121. [PMID: 30935998 DOI: 10.1016/j.yjmcc.2019.03.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 03/06/2019] [Accepted: 03/27/2019] [Indexed: 12/22/2022]
Abstract
Ca2+-sensing receptors (CaSRs) belong to the class C of G protein-coupled receptors and are activated by extracellular Ca2+. CaSRs display biased G protein signaling by coupling to different classes of heterotrimeric G proteins depending on agonist and cell type. In this study we used fluorescent biosensors to directly analyze G protein coupling to CaSRs and downstream signaling in living cells. In HEK 293 cells, CaSRs displayed biased signaling: elevation of extracellular Ca2+ or application of the alternative agonist spermine caused activation of Gi- and Gq-proteins. Adult cardiac myocytes express endogenous CaSRs, which have been implicated in regulating Ca2+ signaling and contractility. Biased signaling of CaSRs has not been investigated in these cells. To evaluate efficiencies of Gi- and Gq-signaling via CaSRs in rat atrial myocytes, we measured G protein-activated K+ (GIRK) channels. Activation of GIRK requires binding of Gβγ subunits released from Gi proteins, whereas Gq-signaling results in inhibition of GIRK channel activity. Stimulation of CaSRs by Ca2+ or spermine failed to directly activate Gi and GIRK channels. When GIRK channels were pre-activated via endogenous M2 receptors, stimulation of CaSRs caused pronounced inhibition of GIRK currents. This effect was specific to CaSR activation: GIRK current inhibition was sensitive to NPS-2143, a negative allosteric modulator of CaSRs, and abrogated by FR900359, a direct inhibitor of Gq. GIRK current inhibition was also sensitive to the PKC inhibitor chelerythrine, suggesting that following activation of CaSR and Gq, GIRK currents are modulated by PKC phosphorylation. We conclude from this data that cardiac CaSRs do not activate Gi and affect GIRK currents preferentially via the Gq/PKC pathway.
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Affiliation(s)
| | - Anne Niemeyer
- Department of Physiology, Ruhr University Bochum, Bochum, Germany
| | - Gabriele M König
- Institute of Pharmaceutical Biology, University of Bonn, Bonn, Germany
| | - Evi Kostenis
- Institute of Pharmaceutical Biology, University of Bonn, Bonn, Germany
| | - Lutz Pott
- Department of Physiology, Ruhr University Bochum, Bochum, Germany
| | - Andreas Rinne
- Department of Physiology, Ruhr University Bochum, Bochum, Germany
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19
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Liu Y, LoCaste CE, Liu W, Poltash ML, Russell DH, Laganowsky A. Selective binding of a toxin and phosphatidylinositides to a mammalian potassium channel. Nat Commun 2019; 10:1352. [PMID: 30902995 PMCID: PMC6430785 DOI: 10.1038/s41467-019-09333-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Accepted: 03/05/2019] [Indexed: 02/05/2023] Open
Abstract
G-protein-gated inward rectifying potassium channels (GIRKs) require Gβγ subunits and phosphorylated phosphatidylinositides (PIPs) for gating. Although studies have provided insight into these interactions, the mechanism of how these events are modulated by Gβγ and the binding affinity between PIPs and GIRKs remains poorly understood. Here, native ion mobility mass spectrometry is employed to directly monitor small molecule binding events to mouse GIRK2. GIRK2 binds the toxin tertiapin Q and PIPs selectively and with significantly higher affinity than other phospholipids. A mutation in GIRK2 that causes a rotation in the cytoplasmic domain, similarly to Gβγ-binding to the wild-type channel, revealed differences in the selectivity towards PIPs. More specifically, PIP isoforms known to weakly activate GIRKs have decreased binding affinity. Taken together, our results reveal selective small molecule binding and uncover a mechanism by which rotation of the cytoplasmic domain can modulate GIRK•PIP interactions.
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Affiliation(s)
- Yang Liu
- Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, TX, 77030, USA
| | - Catherine E LoCaste
- Department of Chemistry, Texas A&M University, College Station, TX, 77842, USA
| | - Wen Liu
- Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, TX, 77030, USA
| | - Michael L Poltash
- Department of Chemistry, Texas A&M University, College Station, TX, 77842, USA
| | - David H Russell
- Department of Chemistry, Texas A&M University, College Station, TX, 77842, USA
| | - Arthur Laganowsky
- Department of Chemistry, Texas A&M University, College Station, TX, 77842, USA.
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20
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Constantin S, Wray S. Nociceptin/Orphanin-FQ Inhibits Gonadotropin-Releasing Hormone Neurons via G-Protein-Gated Inwardly Rectifying Potassium Channels. eNeuro 2018; 5:ENEURO.0161-18.2018. [PMID: 30627649 PMCID: PMC6325553 DOI: 10.1523/eneuro.0161-18.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 12/03/2018] [Accepted: 12/03/2018] [Indexed: 12/18/2022] Open
Abstract
The pulsatile release of gonadotropin-releasing hormone (GnRH) is a key feature of the hypothalamic-pituitary-gonadal axis. Kisspeptin neurons in the arcuate nucleus (ARC) trigger GnRH neuronal activity, but how GnRH neurons return to baseline electrical activity is unknown. Nociceptin/orphanin-FQ (OFQ) is an inhibitory neuromodulator. ARC proopiomelanocortin (POMC) neurons, known to receive inputs from ARC kisspeptin neurons, contact GnRH neurons and coexpress OFQ in the rat. In the present study, the effect of OFQ(1-13) on GnRH neurons was determined in the mouse. We identified transcripts for the OFQ receptor [opioid receptor like 1 (ORL1)] in GnRH neurons, and, using two-model systems (explants and slices), we found that OFQ exerted a potent inhibition on GnRH neurons, with or without excitatory inputs. We confirmed that the inhibition was mediated by ORL1 via Gi/o-protein coupling. The inhibition, occurring independently of levels of intracellular cyclic adenosine monophosphate, was sensitive to inwardly rectifying potassium channels. The only specific blocker of Gi/o-protein-coupled inwardly rectifying potassium (GIRK) channels, tertiapin-Q (TPNQ), was ineffective in the inhibition of OFQ. Two GIRK activators, one sharing the binding site of TPNQ and one active only on GIRK1-containing GIRK channels, failed to trigger an inhibition. In contrast, protein kinase C phosphorylation activation, known to inhibit GIRK2-mediated currents, prevented the OFQ inhibition. These results indicate a specific combination of GIRK subunits, GIRK2/3 in GnRH neurons. In vivo, double-labeled OFQ/POMC fibers were found in the vicinity of GnRH neurons, and OFQ fibers apposed GnRH neurons. Together, this study brings to light a potent neuromodulator of GnRH neurons.
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Affiliation(s)
- Stephanie Constantin
- Cellular and Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke/National Institutes of Health, Bethesda, Maryland 20892-3703
| | - Susan Wray
- Cellular and Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke/National Institutes of Health, Bethesda, Maryland 20892-3703
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21
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Ha J, Xu Y, Kawano T, Hendon T, Baki L, Garai S, Papapetropoulos A, Thakur GA, Plant LD, Logothetis DE. Hydrogen sulfide inhibits Kir2 and Kir3 channels by decreasing sensitivity to the phospholipid phosphatidylinositol 4,5-bisphosphate (PIP 2). J Biol Chem 2018; 293:3546-3561. [PMID: 29317494 DOI: 10.1074/jbc.ra117.001679] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Revised: 01/07/2018] [Indexed: 11/06/2022] Open
Abstract
Inwardly rectifying potassium (Kir) channels establish and regulate the resting membrane potential of excitable cells in the heart, brain, and other peripheral tissues. Phosphatidylinositol 4,5-bisphosphate (PIP2) is a key direct activator of ion channels, including Kir channels. The gasotransmitter carbon monoxide has been shown to regulate Kir channel activity by altering channel-PIP2 interactions. Here, we tested in two cellular models the effects and mechanism of action of another gasotransmitter, hydrogen sulfide (H2S), thought to play a key role in cellular responses under ischemic conditions. Direct administration of sodium hydrogen sulfide as an exogenous H2S source and expression of cystathionine γ-lyase, a key enzyme that produces endogenous H2S in specific brain tissues, resulted in comparable current inhibition of several Kir2 and Kir3 channels. This effect resulted from changes in channel-gating kinetics rather than in conductance or cell-surface localization. The extent of H2S regulation depended on the strength of the channel-PIP2 interactions. H2S regulation was attenuated when channel-PIP2 interactions were strengthened and was increased when channel-PIP2 interactions were weakened by depleting PIP2 levels. These H2S effects required specific cytoplasmic cysteine residues in Kir3.2 channels. Mutation of these residues abolished H2S inhibition, and reintroduction of specific cysteine residues back into the background of the cytoplasmic cysteine-lacking mutant rescued H2S inhibition. Molecular dynamics simulation experiments provided mechanistic insights into how potential sulfhydration of specific cysteine residues could lead to changes in channel-PIP2 interactions and channel gating.
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Affiliation(s)
- Junghoon Ha
- From the Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298
| | - Yu Xu
- Department of Pharmaceutical Sciences in the School of Pharmacy, Northeastern University Bouvé College of Health Sciences, Boston, Massachusetts 02115
| | - Takeharu Kawano
- Department of Pharmaceutical Sciences in the School of Pharmacy, Northeastern University Bouvé College of Health Sciences, Boston, Massachusetts 02115
| | - Tyler Hendon
- From the Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298
| | - Lia Baki
- Department of Pharmaceutical Sciences in the School of Pharmacy, Northeastern University Bouvé College of Health Sciences, Boston, Massachusetts 02115
| | - Sumanta Garai
- Department of Pharmaceutical Sciences in the School of Pharmacy, Northeastern University Bouvé College of Health Sciences, Boston, Massachusetts 02115
| | - Andreas Papapetropoulos
- the Laboratory of Pharmacology, Faculty of Pharmacy, National and Kapodistrian University of Athens, Athens 157 71, Greece, and.,the Center of Clinical, Experimental Surgery and Translational Research, Biomedical Research Foundation of the Academy of Athens, Athens 11527, Greece
| | - Ganesh A Thakur
- Department of Pharmaceutical Sciences in the School of Pharmacy, Northeastern University Bouvé College of Health Sciences, Boston, Massachusetts 02115
| | - Leigh D Plant
- Department of Pharmaceutical Sciences in the School of Pharmacy, Northeastern University Bouvé College of Health Sciences, Boston, Massachusetts 02115
| | - Diomedes E Logothetis
- From the Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298, .,Department of Pharmaceutical Sciences in the School of Pharmacy, Northeastern University Bouvé College of Health Sciences, Boston, Massachusetts 02115
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22
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Levitt ES, Williams JT. Desensitization and Tolerance of Mu Opioid Receptors on Pontine Kölliker-Fuse Neurons. Mol Pharmacol 2017; 93:8-13. [PMID: 29097440 DOI: 10.1124/mol.117.109603] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Accepted: 10/25/2017] [Indexed: 12/13/2022] Open
Abstract
Acute desensitization of mu opioid receptors is thought to be an initial step in the development of tolerance to opioids. Given the resistance of the respiratory system to develop tolerance, desensitization of neurons in the Kölliker-Fuse (KF), a key area in the respiratory circuit, was examined. The activation of G protein-coupled inwardly rectifying potassium current was measured using whole-cell voltage-clamp recordings from KF and locus coeruleus (LC) neurons contained in acute rat brain slices. A saturating concentration of the opioid agonist [Met5]-enkephalin (ME) caused significantly less desensitization in KF neurons compared with LC neurons. In contrast to LC, desensitization in KF neurons was not enhanced by activation of protein kinase C or in slices from morphine-treated rats. Cellular tolerance to ME and morphine was also lacking in KF neurons from morphine-treated rats. The lack of cellular tolerance in KF neurons correlates with the relative lack of tolerance to the respiratory depressant effect of opioids.
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Affiliation(s)
- Erica S Levitt
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida (E.S.L.) and Vollum Institute, Oregon Health and Science University, Portland, Oregon (J.T.W.)
| | - John T Williams
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida (E.S.L.) and Vollum Institute, Oregon Health and Science University, Portland, Oregon (J.T.W.)
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23
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Lacin E, Aryal P, Glaaser IW, Bodhinathan K, Tsai E, Marsh N, Tucker SJ, Sansom MSP, Slesinger PA. Dynamic role of the tether helix in PIP 2-dependent gating of a G protein-gated potassium channel. J Gen Physiol 2017; 149:799-811. [PMID: 28720589 PMCID: PMC5560777 DOI: 10.1085/jgp.201711801] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Revised: 06/06/2017] [Accepted: 06/21/2017] [Indexed: 01/21/2023] Open
Abstract
G protein–gated inwardly rectifying potassium (GIRK) channels are activated by the phospholipid phosphatidylinositol 4,5 bisphosphate (PIP2). Using functional and computational experiments, Lacin et al. reveal that PIP2 interacts with the tether helix of the neuronal GIRK channel in a dynamic way. G protein–gated inwardly rectifying potassium (GIRK) channels control neuronal excitability in the brain and are implicated in several different neurological diseases. The anionic phospholipid phosphatidylinositol 4,5 bisphosphate (PIP2) is an essential cofactor for GIRK channel gating, but the precise mechanism by which PIP2 opens GIRK channels remains poorly understood. Previous structural studies have revealed several highly conserved, positively charged residues in the “tether helix” (C-linker) that interact with the negatively charged PIP2. However, these crystal structures of neuronal GIRK channels in complex with PIP2 provide only snapshots of PIP2’s interaction with the channel and thus lack details about the gating transitions triggered by PIP2 binding. Here, our functional studies reveal that one of these conserved basic residues in GIRK2, Lys200 (6′K), supports a complex and dynamic interaction with PIP2. When Lys200 is mutated to an uncharged amino acid, it activates the channel by enhancing the interaction with PIP2. Atomistic molecular dynamic simulations of neuronal GIRK2 with the same 6′ substitution reveal an open GIRK2 channel with PIP2 molecules adopting novel positions. This dynamic interaction with PIP2 may explain the intrinsic low open probability of GIRK channels and the mechanism underlying activation by G protein Gβγ subunits and ethanol.
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Affiliation(s)
- Emre Lacin
- Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Prafulla Aryal
- Department of Biochemistry, University of Oxford, Oxford, England, UK.,OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford, England, UK
| | - Ian W Glaaser
- Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY
| | | | - Eric Tsai
- Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Nidaa Marsh
- Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Stephen J Tucker
- OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford, England, UK.,Department of Physics, University of Oxford, Oxford, England, UK
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, Oxford, England, UK.,OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford, England, UK
| | - Paul A Slesinger
- Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY .,Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY
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