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Yao X, Gao S, Yan N. Structural biology of voltage-gated calcium channels. Channels (Austin) 2024; 18:2290807. [PMID: 38062897 PMCID: PMC10761187 DOI: 10.1080/19336950.2023.2290807] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 11/27/2023] [Indexed: 12/18/2023] Open
Abstract
Voltage-gated calcium (Cav) channels mediate Ca2+ influx in response to membrane depolarization, playing critical roles in diverse physiological processes. Dysfunction or aberrant regulation of Cav channels can lead to life-threatening consequences. Cav-targeting drugs have been clinically used to treat cardiovascular and neuronal disorders for several decades. This review aims to provide an account of recent developments in the structural dissection of Cav channels. High-resolution structures have significantly advanced our understanding of the working and disease mechanisms of Cav channels, shed light on the molecular basis for their modulation, and elucidated the modes of actions (MOAs) of representative drugs and toxins. The progress in structural studies of Cav channels lays the foundation for future drug discovery efforts targeting Cav channelopathies.
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Affiliation(s)
- Xia Yao
- TaiKang Center for Life and Medical Sciences, School of Pharmaceutical Sciences, Wuhan University, Wuhan, China
| | - Shuai Gao
- TaiKang Center for Life and Medical Sciences, School of Pharmaceutical Sciences, Wuhan University, Wuhan, China
| | - Nieng Yan
- Beijing Frontier Research Center for Biological Structures, State Key Laboratory of Membrane Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
- Shenzhen Medical Academy of Research and Translation, Shenzhen, China
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2
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Akin EJ, Aoun J, Jimenez C, Mayne K, Baeck J, Young MD, Sullivan B, Sanders KM, Ward SM, Bulley S, Jaggar JH, Earley S, Greenwood IA, Leblanc N. ANO1, CaV1.2, and IP3R form a localized unit of EC-coupling in mouse pulmonary arterial smooth muscle. J Gen Physiol 2023; 155:e202213217. [PMID: 37702787 PMCID: PMC10499037 DOI: 10.1085/jgp.202213217] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 08/01/2023] [Accepted: 08/29/2023] [Indexed: 09/14/2023] Open
Abstract
Pulmonary arterial (PA) smooth muscle cells (PASMC) generate vascular tone in response to agonists coupled to Gq-protein receptor signaling. Such agonists stimulate oscillating calcium waves, the frequency of which drives the strength of contraction. These Ca2+ events are modulated by a variety of ion channels including voltage-gated calcium channels (CaV1.2), the Tmem16a or Anoctamin-1 (ANO1)-encoded calcium-activated chloride (CaCC) channel, and Ca2+ release from the sarcoplasmic reticulum through inositol-trisphosphate receptors (IP3R). Although these calcium events have been characterized, it is unclear how these calcium oscillations underly a sustained contraction in these muscle cells. We used smooth muscle-specific ablation of ANO1 and pharmacological tools to establish the role of ANO1, CaV1.2, and IP3R in the contractile and intracellular Ca2+ signaling properties of mouse PA smooth muscle expressing the Ca2+ biosensor GCaMP3 or GCaMP6. Pharmacological block or genetic ablation of ANO1 or inhibition of CaV1.2 or IP3R, or Ca2+ store depletion equally inhibited 5-HT-induced tone and intracellular Ca2+ waves. Coimmunoprecipitation experiments showed that an anti-ANO1 antibody was able to pull down both CaV1.2 and IP3R. Confocal and superresolution nanomicroscopy showed that ANO1 coassembles with both CaV1.2 and IP3R at or near the plasma membrane of PASMC from wild-type mice. We conclude that the stable 5-HT-induced PA contraction results from the integration of stochastic and localized Ca2+ events supported by a microenvironment comprising ANO1, CaV1.2, and IP3R. In this model, ANO1 and CaV1.2 would indirectly support cyclical Ca2+ release events from IP3R and propagation of intracellular Ca2+ waves.
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Affiliation(s)
- Elizabeth J. Akin
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, Reno, NV, USA
| | - Joydeep Aoun
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, Reno, NV, USA
| | - Connor Jimenez
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, Reno, NV, USA
| | - Katie Mayne
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, Reno, NV, USA
| | - Julius Baeck
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, Reno, NV, USA
| | - Michael D. Young
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, Reno, NV, USA
| | - Brennan Sullivan
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, Reno, NV, USA
| | - Kenton M. Sanders
- Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, USA
| | - Sean M. Ward
- Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, USA
| | - Simon Bulley
- Department of Physiology, College of Medicine, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Jonathan H. Jaggar
- Department of Physiology, College of Medicine, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Scott Earley
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, Reno, NV, USA
| | - Iain A. Greenwood
- Department of Vascular Pharmacology, Molecular and Clinical Science Research Institute, St. George’s University of London, London, UK
| | - Normand Leblanc
- Department of Pharmacology and Center of Biomedical Research Excellence (COBRE) for Molecular and Cellular Signal Transduction in the Cardiovascular System, Reno, NV, USA
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3
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Quiroz-Acosta T, Bermeo K, Arenas I, Garcia DE. G-protein tonic inhibition of calcium channels in pancreatic β-cells. Am J Physiol Cell Physiol 2023; 325:C592-C598. [PMID: 37458440 DOI: 10.1152/ajpcell.00447.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 06/30/2023] [Accepted: 07/03/2023] [Indexed: 08/17/2023]
Abstract
Voltage-gated calcium channels (CaV) conduct Ca2+ influx promoting neurotransmitters and hormone release. CaV are finely regulated by voltage-dependent and independent pathways either by G-protein-coupled receptors (GPCRs) or intramembrane lipids, respectively, in neurons and glands. Interestingly, pancreatic β-cells are abundantly innervated by both sympathetic and parasympathetic neurons, while a variety of high-voltage activated (HVA) Ca2+ channels are present in these cells. Thus, autonomic system seems to exert a tonic inhibition on HVA Ca2+ channels throughout GPCRs, constitutively preventing hormone secretion. Therefore, this work aimed to investigate noradrenergic and cholinergic inhibition of HVA Ca2+ channels in pancreatic β-cells. Experiments were conducted in pancreatic β-cells of rat by using patch-clamping methods, immunocytochemistry, pharmacological probes, and biochemical reagents. A voltage-clamp protocol with a strong depolarizing prepulse was used to unmask tonic inhibition. Herein, we consistently find a basal tonic inhibition of HVA Ca2+ channels according to a GPCRs regulation. Facilitation ratio is enhanced by noradrenaline (NA) according to a voltage-dependent regulation and a membrane-delimited mechanism, while no facilitation changes are observed with carbachol or phosphatidylinositol 4,5-bisphosphate (PIP2). Furthermore, carbachol or intramembrane lipids, such as PIP2, do not change facilitation ratio according to a voltage-independent regulation. Together, HVA Ca2+ channels of pancreatic β-cells are constitutively inhibited by GPCRs, suggesting a natural brake preventing cells from exhaustive insulin secretion.NEW & NOTEWORTHY Our results support the hypothesis that GPCRs tonically inhibit HVA Ca2+ channels in pancreatic β-cells. A voltage-clamp protocol with a strong depolarizing prepulse was used to unmask voltage-dependent inhibition of Ca2+ channels. The novelty of these results strengthens the critical role of Gβγ's in Ca2+ channel regulation, highlighting kinetic slowing and increased facilitation ratio. Together, HVA Ca2+ channels of pancreatic β-cells are constitutively inhibited by GPCRs underlying fine-tuning modulation of insulin secretion.
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Affiliation(s)
- Tayde Quiroz-Acosta
- Department of Physiology, Faculty of Medicine, Universidad Nacional Autónoma de México, UNAM, Ciudad de México, Mexico
| | - Karina Bermeo
- Department of Physiology, Faculty of Medicine, Universidad Nacional Autónoma de México, UNAM, Ciudad de México, Mexico
| | - Isabel Arenas
- Department of Physiology, Faculty of Medicine, Universidad Nacional Autónoma de México, UNAM, Ciudad de México, Mexico
| | - David E Garcia
- Department of Physiology, Faculty of Medicine, Universidad Nacional Autónoma de México, UNAM, Ciudad de México, Mexico
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Harvey KE, Tang S, LaVigne EK, Pratt EPS, Hockerman GH. RyR2 regulates store-operated Ca2+ entry, phospholipase C activity, and electrical excitability in the insulinoma cell line INS-1. PLoS One 2023; 18:e0285316. [PMID: 37141277 PMCID: PMC10159205 DOI: 10.1371/journal.pone.0285316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Accepted: 04/19/2023] [Indexed: 05/05/2023] Open
Abstract
The ER Ca2+ channel ryanodine receptor 2 (RyR2) is required for maintenance of insulin content and glucose-stimulated insulin secretion, in part, via regulation of the protein IRBIT in the insulinoma cell line INS-1. Here, we examined store-operated and depolarization-dependent Ca2+entry using INS-1 cells in which either RyR2 or IRBIT were deleted. Store-operated Ca2+ entry (SOCE) stimulated with thapsigargin was reduced in RyR2KO cells compared to controls, but was unchanged in IRBITKO cells. STIM1 protein levels were not different between the three cell lines. Basal and stimulated (500 μM carbachol) phospholipase C (PLC) activity was also reduced specifically in RyR2KO cells. Insulin secretion stimulated by tolbutamide was reduced in RyR2KO and IRBITKO cells compared to controls, but was potentiated by an EPAC-selective cAMP analog in all three cell lines. Cellular PIP2 levels were increased and cortical f-actin levels were reduced in RyR2KO cells compared to controls. Whole-cell Cav channel current density was increased in RyR2KO cells compared to controls, and barium current was reduced by acute activation of the lipid phosphatase pseudojanin preferentially in RyR2KO cells over control INS-1 cells. Action potentials stimulated by 18 mM glucose were more frequent in RyR2KO cells compared to controls, and insensitive to the SK channel inhibitor apamin. Taken together, these results suggest that RyR2 plays a critical role in regulating PLC activity and PIP2 levels via regulation of SOCE. RyR2 also regulates β-cell electrical activity by controlling Cav current density and SK channel activation.
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Affiliation(s)
- Kyle E Harvey
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana, United States of America
| | - Shiqi Tang
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana, United States of America
| | - Emily K LaVigne
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana, United States of America
- Purdue Interdisciplinary Life Sciences Program, Purdue University, West Lafayette, Indiana, United States of America
| | - Evan P S Pratt
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana, United States of America
- Purdue Interdisciplinary Life Sciences Program, Purdue University, West Lafayette, Indiana, United States of America
| | - Gregory H Hockerman
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana, United States of America
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Zong P, Yue L. Regulation of Presynaptic Calcium Channels. ADVANCES IN NEUROBIOLOGY 2023; 33:171-202. [PMID: 37615867 DOI: 10.1007/978-3-031-34229-5_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
Voltage-gated calcium channels (VGCCs), especially Cav2.1 and Cav2.2, are the major mediators of Ca2+ influx at the presynaptic membrane in response to neuron excitation, thereby exerting a predominant control on synaptic transmission. To guarantee the timely and precise release of neurotransmitters at synapses, the activity of presynaptic VGCCs is tightly regulated by a variety of factors, including auxiliary subunits, membrane potential, G protein-coupled receptors (GPCRs), calmodulin (CaM), Ca2+-binding proteins (CaBP), protein kinases, various interacting proteins, alternative splicing events, and genetic variations.
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Affiliation(s)
- Pengyu Zong
- Department of Cell Biology, Calhoun Cardiology Center, University of Connecticut School of Medicine, Farmington, CT, USA
| | - Lixia Yue
- Department of Cell Biology, Calhoun Cardiology Center, University of Connecticut School of Medicine, Farmington, CT, USA.
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Dickson EJ. Role of Lysosomal Cholesterol in Regulating PI(4,5)P 2-Dependent Ion Channel Function. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1422:193-215. [PMID: 36988882 DOI: 10.1007/978-3-031-21547-6_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
Abstract
Lysosomes are central regulators of cellular growth and signaling. Once considered the acidic garbage can of the cell, their ever-expanding repertoire of functions include the regulation of cell growth, gene regulation, metabolic signaling, cell migration, and cell death. In this chapter, we detail how another of the lysosome's crucial roles, cholesterol transport, plays a vital role in the control of ion channel function and neuronal excitability through its ability to influence the abundance of the plasma membrane signaling lipid phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2). This chapter will introduce the biosynthetic pathways of cholesterol and PI(4,5)P2, discuss the molecular mechanisms through which each lipid distinctly regulates ion channels, and consider the interdependence of these lipids in the control of ion channel function.
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Affiliation(s)
- Eamonn J Dickson
- Department of Physiology and Membrane Biology, University of California, Davis, CA, USA.
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Yoon JY, Ho WK. Involvement of Ca2+ in Signaling Mechanisms Mediating Muscarinic Inhibition of M Currents in Sympathetic Neurons. Cell Mol Neurobiol 2022:10.1007/s10571-022-01303-7. [DOI: 10.1007/s10571-022-01303-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 10/31/2022] [Indexed: 11/13/2022]
Abstract
AbstractAcetylcholine can excite neurons by suppressing M-type (KCNQ) potassium channels. This effect is mediated by M1 muscarinic receptors coupled to the Gq protein. Although PIP2 depletion and PKC activation have been strongly suggested to contribute to muscarinic inhibition of M currents (IM), direct evidence is lacking. We investigated the mechanism involved in muscarinic inhibition of IM with Ca2+ measurement and electrophysiological studies in both neuronal (rat sympathetic neurons) and heterologous (HEK cells expressing KCNQ2/KCNQ3) preparations. We found that muscarinic inhibition of IM was not blocked either by PIP2 or by calphostin C, a PKC inhibitor. We then examined whether muscarinic inhibition of IM uses multiple signaling pathways by blocking both PIP2 depletion and PKC activation. This maneuver, however, did not block muscarinic inhibition of IM. Additionally, muscarinic inhibition of IM was not prevented either by sequestering of G-protein βγ subunits from Gα-transducin or anti-Gβγ antibody or by preventing intracellular trafficking of channel proteins with blebbistatin, a class-II myosin inhibitor. Finally, we re-examined the role of Ca2+ signals in muscarinic inhibition of IM. Ca2+ measurements showed that muscarinic stimulation increased intracellular Ca2+ and was comparable to the Ca2+ mobilizing effect of bradykinin. Accordingly, 20-mM of BAPTA significantly suppressed muscarinic inhibition of IM. In contrast, muscarinic inhibition of IM was completely insensitive to 20-mM EGTA. Taken together, these data suggest a role of Ca2+ signaling in muscarinic modulation of IM. The differential effects of EGTA and BAPTA imply that Ca2+ microdomains or spatially local Ca2+ signals contribute to inhibition of IM.
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Behrendt M, Solinski HJ, Schmelz M, Carr R. Bradykinin-Induced Sensitization of Transient Receptor Potential Channel Melastatin 3 Calcium Responses in Mouse Nociceptive Neurons. Front Cell Neurosci 2022; 16:843225. [PMID: 35496916 PMCID: PMC9043526 DOI: 10.3389/fncel.2022.843225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2021] [Accepted: 03/18/2022] [Indexed: 11/13/2022] Open
Abstract
TRPM3 is a calcium-permeable cation channel expressed in a range of sensory neurons that can be activated by heat and the endogenous steroid pregnenolone sulfate (PS). During inflammation, the expression and function of TRPM3 are both augmented in somatosensory nociceptors. However, in isolated dorsal root ganglion (DRG) neurons application of inflammatory mediators like prostaglandins and bradykinin (BK) inhibit TRPM3. Therefore, the aim of this study was to examine the effect of preceding activation of cultured 1 day old mouse DRG neurons by the inflammatory mediator BK on TRPM3-mediated calcium responses. Calcium signals were recorded using the intensity-based dye Fluo-8. We found that TRPM3-mediated calcium responses to PS were enhanced by preceding application of BK in cells that responded to BK with a calcium signal, indicating BK receptor (BKR) expression. The majority of cells that co-expressed TRPM3 and BKRs also expressed TRPV1, however, only a small fraction co-expressed TRPA1, identified by calcium responses to capsaicin and supercinnamaldehyde, respectively. Signaling and trafficking pathways responsible for sensitization of TRPM3 following BK were characterized using inhibitors of second messenger signaling cascades and exocytosis. Pharmacological blockade of protein kinase C, calcium–calmodulin-dependent protein kinase II and diacylglycerol (DAG) lipase did not affect BK-induced sensitization, but inhibition of DAG kinase did. In addition, release of calcium from intracellular stores using thapsigargin also resulted in TRPM3 sensitization. Finally, BK did not sensitize TRPM3 in the presence of exocytosis inhibitors. Collectively, we show that preceding activation of DRG neurons by BK sensitized TRPM3-mediated calcium responses to PS. Our results indicate that BKR-mediated activation of intracellular signaling pathways comprising DAG kinase, calcium and exocytosis may contribute to TRPM3 sensitization during inflammation.
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Kovács ZM, Dienes C, Hézső T, Almássy J, Magyar J, Bányász T, Nánási PP, Horváth B, Szentandrássy N. Pharmacological Modulation and (Patho)Physiological Roles of TRPM4 Channel—Part 1: Modulation of TRPM4. Pharmaceuticals (Basel) 2022; 15:ph15010081. [PMID: 35056138 PMCID: PMC8781449 DOI: 10.3390/ph15010081] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 01/06/2022] [Indexed: 02/06/2023] Open
Abstract
Transient receptor potential melastatin 4 is a unique member of the TRPM protein family and, similarly to TRPM5, is Ca2+-sensitive and permeable to monovalent but not divalent cations. It is widely expressed in many organs and is involved in several functions by regulating the membrane potential and Ca2+ homeostasis in both excitable and non-excitable cells. This part of the review discusses the pharmacological modulation of TRPM4 by listing, comparing, and describing both endogenous and exogenous activators and inhibitors of the ion channel. Moreover, other strategies used to study TRPM4 functions are listed and described. These strategies include siRNA-mediated silencing of TRPM4, dominant-negative TRPM4 variants, and anti-TRPM4 antibodies. TRPM4 is receiving more and more attention and is likely to be the topic of research in the future.
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Affiliation(s)
- Zsigmond Máté Kovács
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.M.K.); (C.D.); (T.H.); (J.A.); (J.M.); (T.B.); (P.P.N.); (B.H.)
- Doctoral School of Molecular Medicine, University of Debrecen, 4032 Debrecen, Hungary
| | - Csaba Dienes
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.M.K.); (C.D.); (T.H.); (J.A.); (J.M.); (T.B.); (P.P.N.); (B.H.)
- Doctoral School of Molecular Medicine, University of Debrecen, 4032 Debrecen, Hungary
| | - Tamás Hézső
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.M.K.); (C.D.); (T.H.); (J.A.); (J.M.); (T.B.); (P.P.N.); (B.H.)
- Doctoral School of Molecular Medicine, University of Debrecen, 4032 Debrecen, Hungary
| | - János Almássy
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.M.K.); (C.D.); (T.H.); (J.A.); (J.M.); (T.B.); (P.P.N.); (B.H.)
| | - János Magyar
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.M.K.); (C.D.); (T.H.); (J.A.); (J.M.); (T.B.); (P.P.N.); (B.H.)
- Division of Sport Physiology, Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
| | - Tamás Bányász
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.M.K.); (C.D.); (T.H.); (J.A.); (J.M.); (T.B.); (P.P.N.); (B.H.)
| | - Péter P. Nánási
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.M.K.); (C.D.); (T.H.); (J.A.); (J.M.); (T.B.); (P.P.N.); (B.H.)
- Department of Dental Physiology and Pharmacology, Faculty of Dentistry, University of Debrecen, 4032 Debrecen, Hungary
| | - Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.M.K.); (C.D.); (T.H.); (J.A.); (J.M.); (T.B.); (P.P.N.); (B.H.)
- Faculty of Pharmacy, University of Debrecen, 4032 Debrecen, Hungary
| | - Norbert Szentandrássy
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.M.K.); (C.D.); (T.H.); (J.A.); (J.M.); (T.B.); (P.P.N.); (B.H.)
- Department of Basic Medical Sciences, Faculty of Dentistry, University of Debrecen, 4032 Debrecen, Hungary
- Correspondence:
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Lee AS, Tiwari S, Bishop I, Matossian V, Romaneschi N, Miyazaki T, VanderVeen L, Zalevsky J, DeFea K, Cahill CM, Walwyn WM. In vivo and in vitro Characterization of a Partial Mu Opioid Receptor Agonist, NKTR-181, Supports Future Therapeutic Development. FRONTIERS IN PAIN RESEARCH 2021; 2:695962. [PMID: 35295409 PMCID: PMC8915576 DOI: 10.3389/fpain.2021.695962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 07/15/2021] [Indexed: 11/13/2022] Open
Abstract
Mu opioid receptor (MOPr) agonists are well-known and frequently used clinical analgesics but are also rewarding due to their highly addictive and often abusive properties. This may lead to opioid use disorder (OUD) a disorder that effects millions of people worldwide. Therefore, novel compounds are urgently needed to treat OUD. As opioids are effective analgesics and OUD often occurs in conjunction with chronic pain, these novel compounds may be opioids, but they must have a low abuse liability. This could be mediated by diminishing or slowing blood-brain barrier transport, slowing target receptor binding kinetics, and showing a long half-life. NKTR-181 is a PEGylated oxycodol and a MOPr agonist that has slowed blood-brain barrier transport, a long half-life, and diminished likeability in clinical trials. In this study, we examined the signaling and behavioral profile of NKTR-181 in comparison with oxycodone to determine whether further therapeutic development of this compound may be warranted. For this preclinical study, we used a number of in vitro and in vivo assays. The signaling profile of NKTR-181 was determined by the electrophysiological assessment of MOPr-Ca2+ channel inhibition in the nociceptive neurons of rodent dorsal root ganglia. Heterologous cell-based assays were used to assess biased agonism and receptor trafficking. Different rodent behavioral models were used to define the NKTR-181-induced relief of effective and reflexive nociception and drug-seeking behavior as assessed by an intravenous self-administration (IVSA) of NKTR-181. We found that NKTR-181 and oxycodone are partial agonists in G-protein signaling and Ca2+ channel inhibition assays and promote limited MOPr desensitization. However, NKTR-181 inhibits Ca2+ channels by a different mechanism than oxycodone and induces a different pattern of arrestin recruitment. In addition, NKTR-181 has a slower receptor on-rate and a slower rate of Ca2+ channel coupling than oxycodone. This signaling profile is coupled with a slower onset of antinociception and limited drug-seeking behavior in comparison with oxycodone. Together with its known long half-life and slow blood-brain barrier transport, these data suggest that NKTR-181 could be further studied as a pharmacotherapeutic treatment modality for OUD.
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Affiliation(s)
- Alex S. Lee
- Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, Los Angeles, CA, United States
| | - Suchi Tiwari
- Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, Los Angeles, CA, United States
| | - Isabel Bishop
- Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, Los Angeles, CA, United States
| | - Vartan Matossian
- Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, Los Angeles, CA, United States
| | - Nicole Romaneschi
- Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, Los Angeles, CA, United States
| | | | | | | | - Kathryn DeFea
- KiloDalton Consulting, Orinda, CA, United States
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, CA, United States
| | - Catherine M. Cahill
- Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, Los Angeles, CA, United States
- Brain Research Institute, University of California, Los Angeles, Los Angeles, CA, United States
- Shirley & Stefen Hatos Center for Neuropharmacology, University of California, Los Angeles, Los Angeles, CA, United States
- Jane & Terry Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, Los Angeles, CA, United States
| | - Wendy M. Walwyn
- Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, Los Angeles, CA, United States
- Brain Research Institute, University of California, Los Angeles, Los Angeles, CA, United States
- Shirley & Stefen Hatos Center for Neuropharmacology, University of California, Los Angeles, Los Angeles, CA, United States
- Jane & Terry Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, Los Angeles, CA, United States
- *Correspondence: Wendy M. Walwyn
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11
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Kruse M, Whitten RJ. Control of Neuronal Excitability by Cell Surface Receptor Density and Phosphoinositide Metabolism. Front Pharmacol 2021; 12:663840. [PMID: 33967808 PMCID: PMC8097148 DOI: 10.3389/fphar.2021.663840] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 03/29/2021] [Indexed: 12/27/2022] Open
Abstract
Phosphoinositides are members of a family of minor phospholipids that make up about 1% of all lipids in most cell types. Despite their low abundance they have been found to be essential regulators of neuronal activities such as action potential firing, release and re-uptake of neurotransmitters, and interaction of cytoskeletal proteins with the plasma membrane. Activation of several different neurotransmitter receptors can deplete phosphoinositide levels by more than 90% in seconds, thereby profoundly altering neuronal behavior; however, despite the physiological importance of this mechanism we still lack a profound quantitative understanding of the connection between phosphoinositide metabolism and neuronal activity. Here, we present a model that describes phosphoinositide metabolism and phosphoinositide-dependent action potential firing in sympathetic neurons. The model allows for a simulation of activation of muscarinic acetylcholine receptors and its effects on phosphoinositide levels and their regulation of action potential firing in these neurons. In this paper, we describe the characteristics of the model, its calibration to experimental data, and use the model to analyze how alterations of surface density of muscarinic acetylcholine receptors or altered activity levels of a key enzyme of phosphoinositide metabolism influence action potential firing of sympathetic neurons. In conclusion, the model provides a comprehensive framework describing the connection between muscarinic acetylcholine signaling, phosphoinositide metabolism, and action potential firing in sympathetic neurons which can be used to study the role of these signaling systems in health and disease.
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Affiliation(s)
- Martin Kruse
- Department of Biology, Bates College, Lewiston, ME, United States
- Program in Neuroscience, Bates College, Lewiston, ME, United States
| | - Rayne J. Whitten
- Program in Neuroscience, Bates College, Lewiston, ME, United States
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12
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Agahari FA, Stricker C. Serotonergic Modulation of Spontaneous and Evoked Transmitter Release in Layer II Pyramidal Cells of Rat Somatosensory Cortex. Cereb Cortex 2021; 31:1182-1200. [PMID: 33063109 DOI: 10.1093/cercor/bhaa285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
As axons from the raphe nuclei densely innervate the somatosensory cortex, we investigated how serotonin (5-HT) modulates transmitter release in layer II pyramidal cells of rat barrel cortex. In the presence of tetrodotoxin and gabazine, 10 μM 5-HT caused a waxing and waning in the frequency of miniature excitatory postsynaptic currents (mEPSC) with no effect on amplitude. Specifically, within 15 min of recording the mEPSC frequency initially increased by 28 ± 7%, then dropped to below control (-15 ± 3%), before resurging back to 27 ± 7% larger than control. These changes were seen in 47% of pyramidal cells (responders) and were mediated by 5-HT2C receptors (5-HT2CR). Waxing resulted from phospholipase C activation, IP3 production, and Ca2+ release from presynaptic stores. Waning was prevented if PKC was blocked. In contrast, in paired recordings, the unitary EPSC amplitude was reduced by 50 ± 3% after 5-HT exposure in almost all cases with no significant effect on paired-pulse ratio and synaptic dynamics. This sustained EPSC reduction was also caused by 5-HT2R, but was mediated by presynaptic Gβγ subunits likely limiting influx through CaV2 channels. EPSC reduction, together with enhanced spontaneous noise in a restricted subset of inputs, could temporarily diminish the signal-to-noise ratio and affect the computation in the neocortical microcircuit.
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Affiliation(s)
- Fransiscus Adrian Agahari
- Neuronal Network Laboratory, Eccles Institute of Neuroscience, The John Curtin School of Medical Research, Australian National University, Acton ACT 2601, Australia.,Division of Cerebral Circuitry, National Institute for Physiological Sciences, Okazaki 444-8787, Japan.,Brain Science Institute, Tamagawa University, Tokyo 194-8610, Japan
| | - Christian Stricker
- Neuronal Network Laboratory, Eccles Institute of Neuroscience, The John Curtin School of Medical Research, Australian National University, Acton ACT 2601, Australia
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13
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Kirchner MK, Armstrong WE, Guan D, Ueta Y, Foehring RC. PIP 2 alters of Ca 2+ currents in acutely dissociated supraoptic oxytocin neurons. Physiol Rep 2020; 7:e14198. [PMID: 31444865 PMCID: PMC6708058 DOI: 10.14814/phy2.14198] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 07/11/2019] [Indexed: 12/21/2022] Open
Abstract
Magnocellular neurosecretory cells (MNCs) occupying the supraoptic nucleus (SON) contain voltage‐gated Ca2+ channels that provide Ca2+ for triggering vesicle release, initiating signaling pathways, and activating channels, such as the potassium channels underlying the afterhyperpolarization (AHP). Phosphotidylinositol 4,5‐bisphosphate (PIP2) is a phospholipid membrane component that has been previously shown to modulate Ca2+ channels, including in the SON in our previous work. In this study, we further investigated the ways in which PIP2 modulates these channels, and for the first time show how PIP2 modulates CaV channel currents in native membranes. Using whole cell patch clamp of genetically labeled dissociated neurons, we demonstrate that PIP2 depletion via wortmannin (0.5 μmol/L) inhibits Ca2+ channel currents in OT but not VP neurons. Additionally, it hyperpolarizes voltage‐dependent activation of the channels by ~5 mV while leaving the slope of activation unchanged, properties unaffected in VP neurons. We also identified key differences in baseline currents between the cell types, wherein VP whole cell Ca2+ currents display more inactivation and shorter deactivation time constants. Wortmannin accelerates inactivation of Ca2+ channels in OT neurons, which we show to be mostly an effect on N‐type Ca2+ channels. Finally, we demonstrate that wortmannin prevents prepulse‐induced facilitation of peak Ca2+ channel currents. We conclude that PIP2 is a modulator that enhances current through N‐type channels. This has implications for the afterhyperpolarization (AHP) of OT neurons, as previous work from our laboratory demonstrated the AHP is inhibited by wortmannin, and that its primary activation is from intracellular Ca2+ contributed by N‐type channels.
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Affiliation(s)
- Matthew K Kirchner
- Department of Anatomy and Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
| | - William E Armstrong
- Department of Anatomy and Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Dongxu Guan
- Department of Anatomy and Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Yoichi Ueta
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan
| | - Robert C Foehring
- Department of Anatomy and Physiology, University of Tennessee Health Science Center, Memphis, Tennessee
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14
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Lemtiri-Chlieh F, Arold ST, Gehring C. Mg 2+ Is a Missing Link in Plant Cell Ca 2+ Signalling and Homeostasis-A Study on Vicia faba Guard Cells. Int J Mol Sci 2020; 21:ijms21113771. [PMID: 32471040 PMCID: PMC7312177 DOI: 10.3390/ijms21113771] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2020] [Revised: 05/13/2020] [Accepted: 05/15/2020] [Indexed: 01/04/2023] Open
Abstract
Hyperpolarization-activated calcium channels (HACCs) are found in the plasma membrane and tonoplast of many plant cell types, where they have an important role in Ca2+-dependent signalling. The unusual gating properties of HACCs in plants, i.e., activation by membrane hyperpolarization rather than depolarization, dictates that HACCs are normally open in the physiological hyperpolarized resting membrane potential state (the so-called pump or P-state); thus, if not regulated, they would continuously leak Ca2+ into cells. HACCs are permeable to Ca2+, Ba2+, and Mg2+; activated by H2O2 and the plant hormone abscisic acid (ABA); and their activity in guard cells is greatly reduced by increasing amounts of free cytosolic Ca2+ ([Ca2+]Cyt), and hence closes during [Ca2+]Cyt surges. Here, we demonstrate that the presence of the commonly used Mg-ATP inside the guard cell greatly reduces HACC activity, especially at voltages ≤ −200 mV, and that Mg2+ causes this block. Therefore, we firstly conclude that physiological cytosolic Mg2+ levels affect HACC gating and that channel opening requires either high negative voltages (≥−200 mV) or displacement of Mg2+ away from the immediate vicinity of the channel. Secondly, based on structural comparisons with a Mg2+-sensitive animal inward-rectifying K+ channel, we propose that the likely candidate HACCs described here are cyclic nucleotide gated channels (CNGCs), many of which also contain a conserved diacidic Mg2+ binding motif within their pores. This conclusion is consistent with the electrophysiological data. Finally, we propose that Mg2+, much like in animal cells, is an important component in Ca2+ signalling and homeostasis in plants.
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Affiliation(s)
- Fouad Lemtiri-Chlieh
- King Abdullah University of Science and Technology (KAUST), Biological and Environmental Science and Engineering (BESE), Thuwal 23955-6900, Saudi Arabia;
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT 06030, USA
- Correspondence: (F.L.-C); (C.G.)
| | - Stefan T. Arold
- King Abdullah University of Science and Technology (KAUST), Biological and Environmental Science and Engineering (BESE), Thuwal 23955-6900, Saudi Arabia;
- King Abdullah University of Science and Technology (KAUST), Computational Bioscience Research Center (CBRC), Thuwal 23955-6900, Saudi Arabia
- Centre de Biochimie Structurale, CNRS, INSERM, Université de Montpellier, 34090 Montpellier, France
| | - Chris Gehring
- King Abdullah University of Science and Technology (KAUST), Biological and Environmental Science and Engineering (BESE), Thuwal 23955-6900, Saudi Arabia;
- Department of Chemistry, Biology & Biotechnology, University of Perugia, 06121 Perugia, Italy
- Correspondence: (F.L.-C); (C.G.)
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15
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Shah S, Carver CM, Mullen P, Milne S, Lukacs V, Shapiro MS, Gamper N. Local Ca 2+ signals couple activation of TRPV1 and ANO1 sensory ion channels. Sci Signal 2020; 13:13/629/eaaw7963. [PMID: 32345727 DOI: 10.1126/scisignal.aaw7963] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
ANO1 (TMEM16A) is a Ca2+-activated Cl- channel (CaCC) expressed in peripheral somatosensory neurons that are activated by painful (noxious) stimuli. These neurons also express the Ca2+-permeable channel and noxious heat sensor TRPV1, which can activate ANO1. Here, we revealed an intricate mechanism of TRPV1-ANO1 channel coupling in rat dorsal root ganglion (DRG) neurons. Simultaneous optical monitoring of CaCC activity and Ca2+ dynamics revealed that the TRPV1 ligand capsaicin activated CaCCs. However, depletion of endoplasmic reticulum (ER) Ca2+ stores reduced capsaicin-induced Ca2+ increases and CaCC activation, suggesting that ER Ca2+ release contributed to TRPV1-induced CaCC activation. ER store depletion by plasma membrane-localized TRPV1 channels was demonstrated with an ER-localized Ca2+ sensor in neurons exposed to a cell-impermeable TRPV1 ligand. Proximity ligation assays established that ANO1, TRPV1, and the IP3 receptor IP3R1 were often found in close proximity to each other. Stochastic optical reconstruction microscopy (STORM) confirmed the close association between all three channels in DRG neurons. Together, our data reveal the existence of ANO1-containing multichannel nanodomains in DRG neurons and suggest that coupling between TRPV1 and ANO1 requires ER Ca2+ release, which may be necessary to enhance ANO1 activation.
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Affiliation(s)
- Shihab Shah
- School of Biomedical Science, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Chase M Carver
- Department of Cell and Integrative Physiology, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Pierce Mullen
- School of Biomedical Science, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Stephen Milne
- School of Biomedical Science, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Viktor Lukacs
- School of Biomedical Science, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Mark S Shapiro
- Department of Cell and Integrative Physiology, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Nikita Gamper
- School of Biomedical Science, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK. .,Department of Pharmacology, Hebei Medical University, Shijiazhuang 050017, People's Republic of China
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16
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Castro H, Bermeo K, Arenas I, Garcia DE. Maintenance of Ca V2.2 channel-current by PIP 2 unveiled by neomycin in sympathetic neurons of the rat. Arch Biochem Biophys 2020; 682:108261. [PMID: 31923392 DOI: 10.1016/j.abb.2020.108261] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2019] [Revised: 12/13/2019] [Accepted: 01/06/2020] [Indexed: 02/01/2023]
Abstract
Membrane lipids are key determinants in the regulation of voltage-gated ion channels. Phosphatidylinositol 4,5-bisphosphate (PIP2), a native membrane phospholipid, has been involved in the maintenance of the current amplitude and in the voltage-independent regulation of voltage-gated calcium channels (VGCC). However, the nature of the PIP2 regulation on VGCC has not been fully elucidated. This work aimed to investigate whether the interacting PIP2 electrostatic charges may account for maintaining the current amplitude of CaV2.2 channels. Furthermore, we tested whether charge shielding of PIP2 mimics the voltage-independent inhibition induced by M1 muscarinic acetylcholine receptor (M1R) activation. Therefore, neomycin, a polycation that has been shown to block electrostatic interactions of PIP2, was intracellularly dialyzed in superior cervical ganglion (SCG) neurons of the rat. Consistently, neomycin time-dependently diminished the calcium current amplitude letting the channel exhibit the hallmarks of the voltage-independent regulation. These results support that interacting PIP2 charges not only underly the maintenance of the channel-current but also that charge screening of PIP2 by itself unveils the voltage-independent features of CaV2.2 channels in SCG neurons.
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Affiliation(s)
- Hector Castro
- Department of Physiology, School of Medicine, Universidad Nacional Autónoma de México (UNAM), Apartado Postal 70250, C.P. 04510, CdMx, México
| | - Karina Bermeo
- Department of Physiology, School of Medicine, Universidad Nacional Autónoma de México (UNAM), Apartado Postal 70250, C.P. 04510, CdMx, México
| | - Isabel Arenas
- Department of Physiology, School of Medicine, Universidad Nacional Autónoma de México (UNAM), Apartado Postal 70250, C.P. 04510, CdMx, México
| | - David E Garcia
- Department of Physiology, School of Medicine, Universidad Nacional Autónoma de México (UNAM), Apartado Postal 70250, C.P. 04510, CdMx, México.
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17
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Rivas-Ramírez P, Reboreda A, Rueda-Ruzafa L, Herrera-Pérez S, Lamas JA. PIP 2 Mediated Inhibition of TREK Potassium Currents by Bradykinin in Mouse Sympathetic Neurons. Int J Mol Sci 2020; 21:ijms21020389. [PMID: 31936257 PMCID: PMC7014146 DOI: 10.3390/ijms21020389] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 12/30/2019] [Accepted: 01/02/2020] [Indexed: 12/17/2022] Open
Abstract
Bradykinin (BK), a hormone inducing pain and inflammation, is known to inhibit potassium M-currents (IM) and to increase the excitability of the superior cervical ganglion (SCG) neurons by activating the Ca2+-calmodulin pathway. M-current is also reduced by muscarinic agonists through the depletion of membrane phosphatidylinositol 4,5-biphosphate (PIP2). Similarly, the activation of muscarinic receptors inhibits the current through two-pore domain potassium channels (K2P) of the “Tandem of pore-domains in a Weakly Inward rectifying K+ channel (TWIK)-related channels” (TREK) subfamily by reducing PIP2 in mouse SCG neurons (mSCG). The aim of this work was to test and characterize the modulation of TREK channels by bradykinin. We used the perforated-patch technique to investigate riluzole (RIL) activated currents in voltage- and current-clamp experiments. RIL is a drug used in the palliative treatment of amyotrophic lateral sclerosis and, in addition to blocking voltage-dependent sodium channels, it also selectively activates the K2P channels of the TREK subfamily. A cell-attached patch-clamp was also used to investigate TREK-2 single channel currents. We report here that BK reduces spike frequency adaptation (SFA), inhibits the riluzole-activated current (IRIL), which flows mainly through TREK-2 channels, by about 45%, and reduces the open probability of identified single TREK-2 channels in cultured mSCG cells. The effect of BK on IRIL was precluded by the bradykinin receptor (B2R) antagonist HOE-140 (d-Arg-[Hyp3, Thi5, d-Tic7, Oic8]BK) but also by diC8PIP2 which prevents PIP2 depletion when phospholipase C (PLC) is activated. On the contrary, antagonizing inositol triphosphate receptors (IP3R) using 2-aminoethoxydiphenylborane (2-APB) or inhibiting protein kinase C (PKC) with bisindolylmaleimide did not affect the inhibition of IRIL by BK. In conclusion, bradykinin inhibits TREK-2 channels through the activation of B2Rs resulting in PIP2 depletion, much like we have demonstrated for muscarinic agonists. This mechanism implies that TREK channels must be relevant for the capture of information about pain and visceral inflammation.
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18
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Dong N, Lee DWK, Sun HS, Feng ZP. Dopamine-mediated calcium channel regulation in synaptic suppression in L. stagnalis interneurons. Channels (Austin) 2019; 12:153-173. [PMID: 29589519 PMCID: PMC5972806 DOI: 10.1080/19336950.2018.1457897] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
D2 dopamine receptor-mediated suppression of synaptic transmission from interneurons plays a key role in neurobiological functions across species, ranging from respiration to memory formation. In this study, we investigated the mechanisms of D2 receptor-dependent suppression using soma-soma synapse between respiratory interneuron VD4 and LPeD1 in the mollusk Lymnaea stagnalis (L. stagnalis). We studied the effects of dopamine on voltage-dependent Ca2+ current and synaptic vesicle release from the VD4. We report that dopamine inhibits voltage-dependent Ca2+ current in the VD4 by both voltage-dependent and -independent mechanisms. Dopamine also suppresses synaptic vesicle release downstream of activity-dependent Ca2+ influx. Our study demonstrated that dopamine acts through D2 receptors to inhibit interneuron synaptic transmission through both voltage-dependent Ca2+ channel-dependent and -independent pathways. Taken together, these findings expand our understanding of dopamine function and fundamental mechanisms that shape the dynamics of neural circuit.
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Affiliation(s)
- Nancy Dong
- a Department of Physiology, Faculty of Medicine , University of Toronto , Toronto , ON , Canada
| | - David W K Lee
- a Department of Physiology, Faculty of Medicine , University of Toronto , Toronto , ON , Canada
| | - Hong-Shuo Sun
- a Department of Physiology, Faculty of Medicine , University of Toronto , Toronto , ON , Canada
| | - Zhong-Ping Feng
- a Department of Physiology, Faculty of Medicine , University of Toronto , Toronto , ON , Canada
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19
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Malloy CA, Somasundaram E, Omar A, Bhutto U, Medley M, Dzubuk N, Cooper RL. Pharmacological identification of cholinergic receptor subtypes: modulation of locomotion and neural circuit excitability in Drosophila larvae. Neuroscience 2019; 411:47-64. [DOI: 10.1016/j.neuroscience.2019.05.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 04/16/2019] [Accepted: 05/07/2019] [Indexed: 01/28/2023]
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20
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Bielopolski N, Amin H, Apostolopoulou AA, Rozenfeld E, Lerner H, Huetteroth W, Lin AC, Parnas M. Inhibitory muscarinic acetylcholine receptors enhance aversive olfactory learning in adult Drosophila. eLife 2019; 8:48264. [PMID: 31215865 PMCID: PMC6641838 DOI: 10.7554/elife.48264] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 06/18/2019] [Indexed: 11/13/2022] Open
Abstract
Olfactory associative learning in Drosophila is mediated by synaptic plasticity between the Kenyon cells of the mushroom body and their output neurons. Both Kenyon cells and their inputs from projection neurons are cholinergic, yet little is known about the physiological function of muscarinic acetylcholine receptors in learning in adult flies. Here, we show that aversive olfactory learning in adult flies requires type A muscarinic acetylcholine receptors (mAChR-A), particularly in the gamma subtype of Kenyon cells. mAChR-A inhibits odor responses and is localized in Kenyon cell dendrites. Moreover, mAChR-A knockdown impairs the learning-associated depression of odor responses in a mushroom body output neuron. Our results suggest that mAChR-A function in Kenyon cell dendrites is required for synaptic plasticity between Kenyon cells and their output neurons.
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Affiliation(s)
- Noa Bielopolski
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Hoger Amin
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | | | - Eyal Rozenfeld
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Hadas Lerner
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Wolf Huetteroth
- Institute for Biology, University of Leipzig, Leipzig, Germany
| | - Andrew C Lin
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Moshe Parnas
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.,Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
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21
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Nociceptor Signalling through ion Channel Regulation via GPCRs. Int J Mol Sci 2019; 20:ijms20102488. [PMID: 31137507 PMCID: PMC6566991 DOI: 10.3390/ijms20102488] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 05/08/2019] [Accepted: 05/13/2019] [Indexed: 12/23/2022] Open
Abstract
The prime task of nociceptors is the transformation of noxious stimuli into action potentials that are propagated along the neurites of nociceptive neurons from the periphery to the spinal cord. This function of nociceptors relies on the coordinated operation of a variety of ion channels. In this review, we summarize how members of nine different families of ion channels expressed in sensory neurons contribute to nociception. Furthermore, data on 35 different types of G protein coupled receptors are presented, activation of which controls the gating of the aforementioned ion channels. These receptors are not only targeted by more than 20 separate endogenous modulators, but can also be affected by pharmacotherapeutic agents. Thereby, this review provides information on how ion channel modulation via G protein coupled receptors in nociceptors can be exploited to provide improved analgesic therapy.
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22
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Gq-Coupled Muscarinic Receptor Enhancement of KCNQ2/3 Channels and Activation of TRPC Channels in Multimodal Control of Excitability in Dentate Gyrus Granule Cells. J Neurosci 2018; 39:1566-1587. [PMID: 30593498 DOI: 10.1523/jneurosci.1781-18.2018] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 12/17/2018] [Accepted: 12/20/2018] [Indexed: 12/21/2022] Open
Abstract
KCNQ (Kv7, "M-type") K+ channels and TRPC (transient receptor potential, "canonical") cation channels are coupled to neuronal discharge properties and are regulated via Gq/11-protein-mediated signals. Stimulation of Gq/11-coupled receptors both consumes phosphatidylinositol 4,5-bisphosphate (PIP2) via phosphalipase Cβ hydrolysis and stimulates PIP2 synthesis via rises in Ca2+ i and other signals. Using brain-slice electrophysiology and Ca2+ imaging from male and female mice, we characterized threshold K+ currents in dentate gyrus granule cells (DGGCs) and CA1 pyramidal cells, the effects of Gq/11-coupled muscarinic M1 acetylcholine (M1R) 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 M1R enhancement of M-current, rather than suppression, due to stimulation of PIP2 synthesis, which was paralleled by increased PIP2-gated G-protein coupled inwardly rectifying K+ currents as well. Deficiency of KCNQ2-containing M-channels ablated the M1R-induced enhancement of M-current in DGGCs. Simultaneously, M1R stimulation in DGGCs induced robust increases in [Ca2+]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 M1R stimulation in these cells, similar to the previously described actions of M1R stimulation on M-current in peripheral ganglia that mostly involves PIP2 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.SIGNIFICANCE STATEMENT At the neuronal membrane, protein signaling cascades consisting of ion channels and metabotropic receptors govern the electrical properties and neurotransmission of neuronal networks. Muscarinic acetylcholine receptors are G-protein-coupled metabotropic receptors that control the excitability of neurons through regulating ion channels, intracellular Ca2+ signals, and other second-messenger cascades. We have illuminated previously unknown actions of muscarinic stimulation on the excitability of hippocampal principal neurons that include M channels, TRPC (transient receptor potential, "canonical") cation channels, and powerful regulation of lipid metabolism. Our results show that these signaling pathways, and mechanisms of excitability, are starkly distinct between peripheral ganglia and brain, and even between different principal neurons in the hippocampus.
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23
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Liu L, Bonventre JV, Rittenhouse AR. cPLA2α-/- sympathetic neurons exhibit increased membrane excitability and loss of N-Type Ca2+ current inhibition by M1 muscarinic receptor signaling. PLoS One 2018; 13:e0201322. [PMID: 30557348 PMCID: PMC6296557 DOI: 10.1371/journal.pone.0201322] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 07/11/2018] [Indexed: 11/18/2022] Open
Abstract
Group IVa cytosolic phospholipase A2 (cPLA2α) mediates GPCR-stimulated arachidonic acid (AA) release from phosphatidylinositol 4,5-bisphosphate (PIP2) located in plasma membranes. We previously found in superior cervical ganglion (SCG) neurons that PLA2 activity is required for voltage-independent N-type Ca2+ (N-) current inhibition by M1 muscarinic receptors (M1Rs). These findings are at odds with an alternative model, previously observed for M-current inhibition, where PIP2 dissociation from channels and subsequent metabolism by phospholipase C suffices for current inhibition. To resolve cPLA2α’s importance, we have investigated its role in mediating voltage-independent N-current inhibition (~40%) that follows application of the muscarinic agonist oxotremorine-M (Oxo-M). Preincubation with different cPLA2α antagonists or dialyzing cPLA2α antibodies into cells minimized N-current inhibition by Oxo-M, whereas antibodies to Ca2+-independent PLA2 had no effect. Taking a genetic approach, we found that SCG neurons from cPLA2α-/- mice exhibited little N-current inhibition by Oxo-M, confirming a role for cPLA2α. In contrast, cPLA2α antibodies or the absence of cPLA2α had no effect on voltage-dependent N-current inhibition by M2/M4Rs or on M-current inhibition by M1Rs. These findings document divergent M1R signaling mediating M-current and voltage-independent N-current inhibition. Moreover, these differences suggest that cPLA2α acts locally to metabolize PIP2 intimately associated with N- but not M-channels. To determine cPLA2α’s functional importance more globally, we examined action potential firing of cPLA2α+/+ and cPLA2α-/- SCG neurons, and found decreased latency to first firing and interspike interval resulting in a doubling of firing frequency in cPLA2α-/- neurons. These unanticipated findings identify cPLA2α as a tonic regulator of neuronal membrane excitability.
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Affiliation(s)
- Liwang Liu
- Program in Neuroscience, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Joseph V. Bonventre
- Harvard Institute of Medicine, Harvard Medical School & Brigham and Women's Hospital, Boston, Massachusetts, United States of America
| | - Ann R. Rittenhouse
- Program in Neuroscience, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- * E-mail:
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Liu Y, Iwano T, Ma F, Wang P, Wang Y, Zheng M, Liu G, Ono K. Short- and long-term roles of phosphatidylinositol 4,5-bisphosphate PIP 2 on Cav3.1- and Cav3.2-T-type calcium channel current. ACTA ACUST UNITED AC 2018; 26:31-38. [PMID: 30528337 DOI: 10.1016/j.pathophys.2018.12.001] [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: 08/01/2018] [Revised: 11/30/2018] [Accepted: 12/01/2018] [Indexed: 11/24/2022]
Abstract
T-type calcium (Ca2+) channels play important physiological functions in excitable cells including cardiomyocyte. Phosphatidylinositol-4,5-bisphosphate (PIP2) has recently been reported to modulate various ion channels' function. However the actions of PIP2 on the T-type Ca2+ channel remain unclear. To elucidate possible effects of PIP2 on the T-type Ca2+ channel, we applied patch clamp method to investigate recombinant CaV3.1- and CaV3.2-T-type Ca2+ channels expressed in mammalian cell lines with PIP2 in acute- and long-term potentiation. Short- and long-term potentiation of PIP2 shifted the activation and the steady-state inactivation curve toward the hyperpolarization direction of CaV3.1-ICa.T without affecting the maximum inward current density. Short- and long-term potentiation of PIP2 also shifted the activation curve toward the hyperpolarization direction of CaV3.2-ICa.T without affecting the maximum inward current density. Conversely, long-term but not short-term potentiation of PIP2 shifted the steady-state inactivation curve toward the hyperpolarization direction of CaV3.2-ICa.T. Long-term but not short-term potentiation of PIP2 blunted the voltage-dependency of current decay CaV3.1-ICa.T. PIP2 modulates CaV3.1- and CaV3.2-ICa.T not by their current density but by their channel gating properties possibly through its membrane-delimited actions.
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Affiliation(s)
- Yangong Liu
- Department of Cardiology, The First Hospital of Hebei Medical University, 89 Donggang Road, Shijiazhuang, Hebei Province, 050031, People's Republic of China; Department of Pathophysiology, Oita University School of Medicine, Yufu, Oita, 879-5593, Japan
| | - Tomohiro Iwano
- Department of Pathophysiology, Oita University School of Medicine, Yufu, Oita, 879-5593, Japan
| | - Fangfang Ma
- Department of Cardiology, The First Hospital of Hebei Medical University, 89 Donggang Road, Shijiazhuang, Hebei Province, 050031, People's Republic of China; Department of Pathophysiology, Oita University School of Medicine, Yufu, Oita, 879-5593, Japan
| | - Pu Wang
- Department of Cardiology, The First Hospital of Hebei Medical University, 89 Donggang Road, Shijiazhuang, Hebei Province, 050031, People's Republic of China; Department of Pathophysiology, Oita University School of Medicine, Yufu, Oita, 879-5593, Japan
| | - Yan Wang
- Department of Pathophysiology, Oita University School of Medicine, Yufu, Oita, 879-5593, Japan
| | - Mingqi Zheng
- Department of Cardiology, The First Hospital of Hebei Medical University, 89 Donggang Road, Shijiazhuang, Hebei Province, 050031, People's Republic of China
| | - Gang Liu
- Department of Cardiology, The First Hospital of Hebei Medical University, 89 Donggang Road, Shijiazhuang, Hebei Province, 050031, People's Republic of China
| | - Katsushige Ono
- Department of Pathophysiology, Oita University School of Medicine, Yufu, Oita, 879-5593, Japan.
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Hackelberg S, Oliver D. Metabotropic Acetylcholine and Glutamate Receptors Mediate PI(4,5)P 2 Depletion and Oscillations in Hippocampal CA1 Pyramidal Neurons in situ. Sci Rep 2018; 8:12987. [PMID: 30154490 PMCID: PMC6113233 DOI: 10.1038/s41598-018-31322-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Accepted: 08/17/2018] [Indexed: 01/24/2023] Open
Abstract
The sensitivity of many ion channels to phosphatidylinositol-4,5-bisphosphate (PIP2) levels in the cell membrane suggests that PIP2 fluctuations are important and general signals modulating neuronal excitability. Yet the PIP2 dynamics of central neurons in their native environment remained largely unexplored. Here, we examined the behavior of PIP2 concentrations in response to activation of Gq-coupled neurotransmitter receptors in rat CA1 hippocampal neurons in situ in acute brain slices. Confocal microscopy of the PIP2-selective molecular sensors tubbyCT-GFP and PLCδ1-PH-GFP showed that pharmacological activation of muscarinic acetylcholine (mAChR) or group I metabotropic glutamate (mGluRI) receptors induces transient depletion of PIP2 in the soma as well as in the dendritic tree. The observed PIP2 dynamics were receptor-specific, with mAChR activation inducing stronger PIP2 depletion than mGluRI, whereas agonists of other Gαq-coupled receptors expressed in CA1 neurons did not induce measureable PIP2 depletion. Furthermore, the data show for the first time neuronal receptor-induced oscillations of membrane PIP2 concentrations. Oscillatory behavior indicated that neurons can rapidly restore PIP2 levels during persistent activation of Gq and PLC. Electrophysiological responses to receptor activation resembled PIP2 dynamics in terms of time course and receptor specificity. Our findings support a physiological function of PIP2 in regulating electrical activity.
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Affiliation(s)
- Sandra Hackelberg
- Institute of Physiology and Pathophysiology, Philipps University, 35037, Marburg, Germany
- The Ken and Ruth Davee Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Dominik Oliver
- Institute of Physiology and Pathophysiology, Philipps University, 35037, Marburg, Germany.
- DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, GRK 2213, Philipps University, Marburg, Germany.
- Center for Mind, Brain and Behavior (CMBB), Marburg and Giessen, Germany.
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26
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Liu YN, Lu XX, Ren A, Shi L, Zhu J, Jiang AL, Yu HS, Zhao MW. Conversion of phosphatidylinositol (PI) to PI4-phosphate (PI4P) and then to PI(4,5)P 2 is essential for the cytosolic Ca 2+ concentration under heat stress in Ganoderma lucidum. Environ Microbiol 2018; 20:2456-2468. [PMID: 29697195 DOI: 10.1111/1462-2920.14254] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 04/13/2018] [Accepted: 04/23/2018] [Indexed: 11/29/2022]
Abstract
How cells drive the phospholipid signal response to heat stress (HS) to maintain cellular homeostasis is a fundamental issue in biology, but the regulatory mechanism of this fundamental process is unclear. Previous quantitative analyses of lipids showed that phosphatidylinositol (PI) accumulates after HS in Ganoderma lucidum, implying the inositol phospholipid signal may be associated with HS signal transduction. Here, we found that the PI-4-kinase and PI-4-phosphate-5-kinase activities are activated and that their lipid products PI-4-phosphate and PI-4,5-bisphosphate are increased under HS. Further experimental results showed that the cytosolic Ca2+ ([Ca2+ ]c ) and ganoderic acid (GA) contents induced by HS were decreased when cells were pretreated with Li+ , an inhibitor of inositol monophosphatase, and this decrease could be rescued by PI and PI-4-phosphate. Furthermore, inhibition of PI-4-kinases resulted in a decrease in the Ca2+ and GA contents under HS that could be rescued by PI-4-phosphate but not PI. However, the decrease in the Ca2+ and GA contents by silencing of PI-4-phosphate-5-kinase could not be rescued by PI-4-phosphate. Taken together, our study reveals the essential role of the step converting PI to PI-4-phosphate and then to PI-4,5-bisphosphate in [Ca2+ ]c signalling and GA biosynthesis under HS.
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Affiliation(s)
- Yong-Nan Liu
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, Microbiology Department, College of Life Sciences, Nanjing Agricultural University, Jiangsu, Nanjing 210095, People's Republic of China
| | - Xiao-Xiao Lu
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, Microbiology Department, College of Life Sciences, Nanjing Agricultural University, Jiangsu, Nanjing 210095, People's Republic of China
| | - Ang Ren
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, Microbiology Department, College of Life Sciences, Nanjing Agricultural University, Jiangsu, Nanjing 210095, People's Republic of China
| | - Liang Shi
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, Microbiology Department, College of Life Sciences, Nanjing Agricultural University, Jiangsu, Nanjing 210095, People's Republic of China
| | - Jing Zhu
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, Microbiology Department, College of Life Sciences, Nanjing Agricultural University, Jiangsu, Nanjing 210095, People's Republic of China
| | - Ai-Liang Jiang
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, Microbiology Department, College of Life Sciences, Nanjing Agricultural University, Jiangsu, Nanjing 210095, People's Republic of China
| | - Han-Shou Yu
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, Microbiology Department, College of Life Sciences, Nanjing Agricultural University, Jiangsu, Nanjing 210095, People's Republic of China
| | - Ming-Wen Zhao
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, Microbiology Department, College of Life Sciences, Nanjing Agricultural University, Jiangsu, Nanjing 210095, People's Republic of China
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Neumaier F, Alpdogan S, Hescheler J, Schneider T. Protein phosphorylation maintains the normal function of cloned human Ca v2.3 channels. J Gen Physiol 2018; 150:491-510. [PMID: 29453293 PMCID: PMC5839719 DOI: 10.1085/jgp.201711880] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Revised: 12/22/2017] [Accepted: 01/24/2018] [Indexed: 11/30/2022] Open
Abstract
Cav2.3 Ca2+ channels are subject to cytosolic regulation, which has been difficult to characterize in native cells. Neumaier et al. demonstrate the role of phosphorylation in the function of these channels and suggest a close relationship between voltage dependence and the phosphorylation state. R-type currents mediated by native and recombinant Cav2.3 voltage-gated Ca2+ channels (VGCCs) exhibit facilitation (run-up) and subsequent decline (run-down) in whole-cell patch-clamp recordings. A better understanding of the two processes could provide insight into constitutive modulation of the channels in intact cells, but low expression levels and the need for pharmacological isolation have prevented investigations in native systems. Here, to circumvent these limitations, we use conventional and perforated-patch-clamp recordings in a recombinant expression system, which allows us to study the effects of cell dialysis in a reproducible manner. We show that the decline of currents carried by human Cav2.3+β3 channel subunits during run-down is related to adenosine triphosphate (ATP) depletion, which reduces the number of functional channels and leads to a progressive shift of voltage-dependent gating to more negative potentials. Both effects can be counteracted by hydrolysable ATP, whose protective action is almost completely prevented by inhibition of serine/threonine but not tyrosine or lipid kinases. Protein kinase inhibition also mimics the effects of run-down in intact cells, reduces the peak current density, and hyperpolarizes the voltage dependence of gating. Together, our findings indicate that ATP promotes phosphorylation of either the channel or an associated protein, whereas dephosphorylation during cell dialysis results in run-down. These data also distinguish the effects of ATP on Cav2.3 channels from those on other VGCCs because neither direct nucleotide binding nor PIP2 synthesis is required for protection from run-down. We conclude that protein phosphorylation is required for Cav2.3 channel function and could directly influence the normal features of current carried by these channels. Curiously, some of our findings also point to a role for leupeptin-sensitive proteases in run-up and possibly ATP protection from run-down. As such, the present study provides a reliable baseline for further studies on Cav2.3 channel regulation by protein kinases, phosphatases, and possibly proteases.
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Affiliation(s)
- Felix Neumaier
- Institute for Neurophysiology, University of Cologne, Cologne, Germany
| | - Serdar Alpdogan
- Institute for Neurophysiology, University of Cologne, Cologne, Germany
| | - Jürgen Hescheler
- Institute for Neurophysiology, University of Cologne, Cologne, Germany
| | - Toni Schneider
- Institute for Neurophysiology, University of Cologne, Cologne, Germany
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28
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Brown DA. Regulation of neural ion channels by muscarinic receptors. Neuropharmacology 2017; 136:383-400. [PMID: 29154951 DOI: 10.1016/j.neuropharm.2017.11.024] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 10/26/2017] [Accepted: 11/13/2017] [Indexed: 12/20/2022]
Abstract
The excitable behaviour of neurons is determined by the activity of their endogenous membrane ion channels. Since muscarinic receptors are not themselves ion channels, the acute effects of muscarinic receptor stimulation on neuronal function are governed by the effects of the receptors on these endogenous neuronal ion channels. This review considers some principles and factors determining the interaction between subtypes and classes of muscarinic receptors with neuronal ion channels, and summarizes the effects of muscarinic receptor stimulation on a number of different channels, the mechanisms of receptor - channel transduction and their direct consequences for neuronal activity. Ion channels considered include potassium channels (voltage-gated, inward rectifier and calcium activated), voltage-gated calcium channels, cation channels and chloride channels. This article is part of the Special Issue entitled 'Neuropharmacology on Muscarinic Receptors'.
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Affiliation(s)
- David A Brown
- Department of Neuroscience, Physiology & Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
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29
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Topalidou I, Cooper K, Pereira L, Ailion M. Dopamine negatively modulates the NCA ion channels in C. elegans. PLoS Genet 2017; 13:e1007032. [PMID: 28968387 PMCID: PMC5638609 DOI: 10.1371/journal.pgen.1007032] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Revised: 10/12/2017] [Accepted: 09/18/2017] [Indexed: 02/07/2023] Open
Abstract
The NALCN/NCA ion channel is a cation channel related to voltage-gated sodium and calcium channels. NALCN has been reported to be a sodium leak channel with a conserved role in establishing neuronal resting membrane potential, but its precise cellular role and regulation are unclear. The Caenorhabditis elegans orthologs of NALCN, NCA-1 and NCA-2, act in premotor interneurons to regulate motor circuit activity that sustains locomotion. Recently we found that NCA-1 and NCA-2 are activated by a signal transduction pathway acting downstream of the heterotrimeric G protein Gq and the small GTPase Rho. Through a forward genetic screen, here we identify the GPCR kinase GRK-2 as a new player affecting signaling through the Gq-Rho-NCA pathway. Using structure-function analysis, we find that the GPCR phosphorylation and membrane association domains of GRK-2 are required for its function. Genetic epistasis experiments suggest that GRK-2 acts on the D2-like dopamine receptor DOP-3 to inhibit Go signaling and positively modulate NCA-1 and NCA-2 activity. Through cell-specific rescuing experiments, we find that GRK-2 and DOP-3 act in premotor interneurons to modulate NCA channel function. Finally, we demonstrate that dopamine, through DOP-3, negatively regulates NCA activity. Thus, this study identifies a pathway by which dopamine modulates the activity of the NCA channels.
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Affiliation(s)
- Irini Topalidou
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
- * E-mail: (IT); (MA)
| | - Kirsten Cooper
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Laura Pereira
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, New York, United States of America
| | - Michael Ailion
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
- * E-mail: (IT); (MA)
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30
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The NCA-1 and NCA-2 Ion Channels Function Downstream of G q and Rho To Regulate Locomotion in Caenorhabditis elegans. Genetics 2017; 206:265-282. [PMID: 28325749 DOI: 10.1534/genetics.116.198820] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Accepted: 03/15/2017] [Indexed: 02/07/2023] Open
Abstract
The heterotrimeric G protein Gq positively regulates neuronal activity and synaptic transmission. Previously, the Rho guanine nucleotide exchange factor Trio was identified as a direct effector of Gq that acts in parallel to the canonical Gq effector phospholipase C. Here, we examine how Trio and Rho act to stimulate neuronal activity downstream of Gq in the nematode Caenorhabditis elegans Through two forward genetic screens, we identify the cation channels NCA-1 and NCA-2, orthologs of mammalian NALCN, as downstream targets of the Gq-Rho pathway. By performing genetic epistasis analysis using dominant activating mutations and recessive loss-of-function mutations in the members of this pathway, we show that NCA-1 and NCA-2 act downstream of Gq in a linear pathway. Through cell-specific rescue experiments, we show that function of these channels in head acetylcholine neurons is sufficient for normal locomotion in C. elegans Our results suggest that NCA-1 and NCA-2 are physiologically relevant targets of neuronal Gq-Rho signaling in C. elegans.
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31
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Tolstykh GP, Tarango M, Roth CC, Ibey BL. Nanosecond pulsed electric field induced dose dependent phosphatidylinositol-4,5-bisphosphate signaling and intracellular electro-sensitization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:438-445. [DOI: 10.1016/j.bbamem.2017.01.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Revised: 12/15/2016] [Accepted: 01/02/2017] [Indexed: 12/11/2022]
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32
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Kim YH, Jeong JH, Ahn DS, Chung S. Phospholipase C-dependent hydrolysis of phosphatidylinositol 4,5-bisphosphate underlies agmatine-induced suppression of N-type Ca 2+ channel in rat celiac ganglion neurons. Biochem Biophys Res Commun 2017; 484:342-347. [PMID: 28131838 DOI: 10.1016/j.bbrc.2017.01.120] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Accepted: 01/23/2017] [Indexed: 12/27/2022]
Abstract
Agmatine suppresses peripheral sympathetic tone by modulating Cav2.2 channels in peripheral sympathetic neurons. However, the detailed cellular signaling mechanism underlying the agmatine-induced Cav2.2 inhibition remains unclear. Therefore, in the present study, we investigated the electrophysiological mechanism for the agmatine-induced inhibition of Cav2.2 current (ICav2.2) in rat celiac ganglion (CG) neurons. Consistent with previous reports, agmatine inhibited ICav2.2 in a VI manner. The agmatine-induced inhibition of the ICav2.2 current was also almost completely hindered by the blockade of the imidazoline I2 receptor (IR2), and an IR2 agonist mimicked the inhibitory effect of agmatine on ICav2.2, implying involvement of IR2. The agmatine-induced ICav2.2 inhibition was significantly hampered by the blockade of G protein or phospholipase C (PLC), but not by the pretreatment with pertussis toxin. In addition, diC8-phosphatidylinositol 4,5-bisphosphate (PIP2) dialysis nearly completely hampered agmatine-induced inhibition, which became irreversible when PIP2 resynthesis was blocked. These results suggest that in rat peripheral sympathetic neurons, agmatine-induced IR2 activation suppresses Cav2.2 channel voltage-independently, and that the PLC-dependent PIP2 hydrolysis is responsible for the agmatine-induced suppression of the Cav2.2 channel.
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Affiliation(s)
- Young-Hwan Kim
- Department of Physiology, Brain Korea 21 Plus Project for Medical Science, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Ji-Hyun Jeong
- Department of Physiology, Brain Korea 21 Plus Project for Medical Science, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Duck-Sun Ahn
- Department of Physiology, Brain Korea 21 Plus Project for Medical Science, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Seungsoo Chung
- Department of Physiology, Brain Korea 21 Plus Project for Medical Science, Yonsei University College of Medicine, Seoul 03722, Republic of Korea.
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33
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Jung SR, Seo JB, Deng Y, Asbury CL, Hille B, Koh DS. Contributions of protein kinases and β-arrestin to termination of protease-activated receptor 2 signaling. ACTA ACUST UNITED AC 2016; 147:255-71. [PMID: 26927499 PMCID: PMC4772372 DOI: 10.1085/jgp.201511477] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Systematic imaging studies and modeling reveal new details of the regulation of the Gq-coupled GPCR, protease-activated receptor 2, by phosphorylation and β-arrestin. Activated Gq protein–coupled receptors (GqPCRs) can be desensitized by phosphorylation and β-arrestin binding. The kinetics and individual contributions of these two mechanisms to receptor desensitization have not been fully distinguished. Here, we describe the shut off of protease-activated receptor 2 (PAR2). PAR2 activates Gq and phospholipase C (PLC) to hydrolyze phosphatidylinositol 4,5-bisphosphate (PIP2) into diacylglycerol and inositol trisphosphate (IP3). We used fluorescent protein–tagged optical probes to monitor several consequences of PAR2 signaling, including PIP2 depletion and β-arrestin translocation in real time. During continuous activation of PAR2, PIP2 was depleted transiently and then restored within a few minutes, indicating fast receptor activation followed by desensitization. Knockdown of β-arrestin 1 and 2 using siRNA diminished the desensitization, slowing PIP2 restoration significantly and even adding a delayed secondary phase of further PIP2 depletion. These effects of β-arrestin knockdown on PIP2 recovery were prevented when serine/threonine phosphatases that dephosphorylate GPCRs were inhibited. Thus, PAR2 may continuously regain its activity via dephosphorylation when there is insufficient β-arrestin to trap phosphorylated receptors. Similarly, blockers of protein kinase C (PKC) and G protein–coupled receptor kinase potentiated the PIP2 depletion. In contrast, an activator of PKC inhibited receptor activation, presumably by augmenting phosphorylation of PAR2. Our interpretations were strengthened by modeling. Simulations supported the conclusions that phosphorylation of PAR2 by protein kinases initiates receptor desensitization and that recruited β-arrestin traps the phosphorylated state of the receptor, protecting it from phosphatases. Speculative thinking suggested a sequestration of phosphatidylinositol 4-phosphate 5 kinase (PIP5K) to the plasma membrane by β-arrestin to explain why knockdown of β-arrestin led to secondary depletion of PIP2. Indeed, artificial recruitment of PIP5K removed the secondary loss of PIP2 completely. Altogether, our experimental and theoretical approaches demonstrate roles and dynamics of the protein kinases, β-arrestin, and PIP5K in the desensitization of PAR2.
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Affiliation(s)
- Seung-Ryoung Jung
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195
| | - Jong Bae Seo
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195
| | - Yi Deng
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195
| | - Charles L Asbury
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195
| | - Bertil Hille
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195
| | - Duk-Su Koh
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195 Department of Physics, Pohang University of Science and Technology, Pohang, Kyungbuk, 790-784, Republic of Korea
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Tolstykh GP, Thompson GL, Beier HT, Steelman ZA, Ibey BL. nsPEF-induced PIP 2 depletion, PLC activity and actin cytoskeletal cortex remodeling are responsible for post-exposure cellular swelling and blebbing. Biochem Biophys Rep 2016; 9:36-41. [PMID: 28955986 PMCID: PMC5614542 DOI: 10.1016/j.bbrep.2016.11.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 10/11/2016] [Accepted: 11/08/2016] [Indexed: 01/11/2023] Open
Abstract
Cell swelling and blebbing has been commonly observed following nanosecond pulsed electric field (nsPEF) exposure. The hypothesized origin of these effects is nanoporation of the plasma membrane (PM) followed by transmembrane diffusion of extracellular fluid and disassembly of cortical actin structures. This investigation will provide evidence that shows passive movement of fluid into the cell through nanopores and increase of intracellular osmotic pressure are not solely responsible for this observed phenomena. We demonstrate that phosphatidylinositol-4,5-bisphosphate (PIP2) depletion and hydrolysis are critical steps in the chain reaction leading to cellular blebbing and swelling. PIP2 is heavily involved in osmoregulation by modulation of ion channels and also serves as an intracellular membrane anchor to cortical actin and phospholipase C (PLC). Given the rather critical role that PIP2 depletion appears to play in the response of cells to nsPEF exposure, it remains unclear how its downstream effects and, specifically, ion channel regulation may contribute to cellular swelling, blebbing, and unknown mechanisms of the lasting “permeabilization” of the PM. Nanosecond electric pulses (nsEPs) of high amplitude induce hydrolysis of PIP2. PLC activation is leading to post-exposure cellular swelling and blebbing. Ion channels modulation and nanoporation are responsible for cellular swelling. Cortical actin dissociation after PIP2 depletion is critical for cellular blebbing.
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Affiliation(s)
- Gleb P. Tolstykh
- General Dynamics Information Technology, JBSA Fort Sam Houston, TX, USA
- Corespondence to: General Dynamics Information Technology, 4141 Petroleum Road, JBSA Fort Sam Houston, TX 78234, USA.
| | - Gary L. Thompson
- Oak Ridge Institute for Science & Education, JBSA Fort Sam Houston, TX, USA
| | - Hope T. Beier
- Air Force Research Laboratory, 711th Human Performance Wing, Airman Systems Directorate, Bioeffects Division, Optical Radiation Bioeffects Branch, JBSA Fort Sam Houston, TX, USA
| | | | - Bennett L. Ibey
- Air Force Research Laboratory, 711th Human Performance Wing, Airman Systems Directorate, Bioeffects Division, Radio Frequency Bioeffects Branch, JBSA Fort Sam Houston, TX, USA
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35
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Kienitz MC, Vladimirova D, Müller C, Pott L, Rinne A. Receptor Species-dependent Desensitization Controls KCNQ1/KCNE1 K+ Channels as Downstream Effectors of Gq Protein-coupled Receptors. J Biol Chem 2016; 291:26410-26426. [PMID: 27834678 DOI: 10.1074/jbc.m116.746974] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 11/09/2016] [Indexed: 12/17/2022] Open
Abstract
Activation of Gq protein-coupled receptors (GqPCRs) might induce divergent cellular responses, related to receptor-specific activation of different branches of the Gq signaling pathway. Receptor-specific desensitization provides a mechanism of effector modulation by restricting the spatiotemporal activation of signaling components downstream of Gq We quantified signaling events downstream of GqPCR activation with FRET-based biosensors in CHO and HEK 293 cells. KCNQ1/KCNE1 channels (IKs) were measured as a functional readout of receptor-specific activation. Activation of muscarinic M1 receptors (M1-Rs) caused robust and reversible inhibition of IKs. In contrast, activation of α1B-adrenergic receptors (α1B-ARs) induced transient inhibition of IKs, which turned into delayed facilitation after agonist withdrawal. As a novel finding, we demonstrate that GqPCR-specific kinetics of IKs modulation are determined by receptor-specific desensitization, evident at the level of Gαq activation, phosphatidylinositol 4,5-bisphosphate (PIP2) depletion, and diacylglycerol production. Sustained IKs inhibition during M1-R stimulation is attributed to robust membrane PIP2 depletion, whereas the rapid desensitization of α1B-AR delimits PIP2 reduction and augments current activation by protein kinase C (PKC). Overexpression of Ca2+-independent PKCδ did not affect the time course of α1B-AR-induced diacylglycerol formation, excluding a contribution of PKCδ to α1B-AR desensitization. Pharmacological inhibition of Ca2+-dependent PKC isoforms abolished fast α1B receptor desensitization and augmented IKs reduction, but did not affect IKs facilitation. These data indicate a contribution of Ca2+-dependent PKCs to α1B-AR desensitization, whereas IKs facilitation is induced by Ca2+-independent PKC isoforms. In contrast, neither inhibition of Ca2+-dependent/Ca2+-independent isoforms nor overexpression of PKCδ induced M1 receptor desensitization, excluding a contribution of PKC to M1-R-induced IKs modulation.
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Affiliation(s)
- Marie-Cécile Kienitz
- From the Institute of Physiology, Ruhr-University Bochum, Universitätsstrasse 150, D-44780 Bochum, Germany
| | - Dilyana Vladimirova
- From the Institute of Physiology, Ruhr-University Bochum, Universitätsstrasse 150, D-44780 Bochum, Germany
| | - Christian Müller
- From the Institute of Physiology, Ruhr-University Bochum, Universitätsstrasse 150, D-44780 Bochum, Germany
| | - Lutz Pott
- From the Institute of Physiology, Ruhr-University Bochum, Universitätsstrasse 150, D-44780 Bochum, Germany
| | - Andreas Rinne
- From the Institute of Physiology, Ruhr-University Bochum, Universitätsstrasse 150, D-44780 Bochum, Germany
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de la Cruz L, Puente EI, Reyes-Vaca A, Arenas I, Garduño J, Bravo-Martínez J, Garcia DE. PIP2 in pancreatic β-cells regulates voltage-gated calcium channels by a voltage-independent pathway. Am J Physiol Cell Physiol 2016; 311:C630-C640. [PMID: 27488666 DOI: 10.1152/ajpcell.00111.2016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 07/29/2016] [Indexed: 12/21/2022]
Abstract
Phosphatidylinositol-4,5-bisphosphate (PIP2) is a membrane phosphoinositide that regulates the activity of many ion channels. Influx of calcium primarily through voltage-gated calcium (CaV) channels promotes insulin secretion in pancreatic β-cells. However, whether CaV channels are regulated by PIP2, as is the case for some non-insulin-secreting cells, is unknown. The purpose of this study was to investigate whether CaV channels are regulated by PIP2 depletion in pancreatic β-cells through activation of a muscarinic pathway induced by oxotremorine methiodide (Oxo-M). CaV channel currents were recorded by the patch-clamp technique. The CaV current amplitude was reduced by activation of the muscarinic receptor 1 (M1R) in the absence of kinetic changes. The Oxo-M-induced inhibition exhibited the hallmarks of voltage-independent regulation and did not involve PKC activation. A small fraction of the Oxo-M-induced CaV inhibition was diminished by a high concentration of Ca2+ chelator, whereas ≥50% of this inhibition was prevented by diC8-PIP2 dialysis. Localization of PIP2 in the plasma membrane was examined by transfecting INS-1 cells with PH-PLCδ1, which revealed a close temporal association between PIP2 hydrolysis and CaV channel inhibition. Furthermore, the depletion of PIP2 by a voltage-sensitive phosphatase reduced CaV currents in a way similar to that observed following M1R activation. These results indicate that activation of the M1R pathway inhibits the CaV channel via PIP2 depletion by a Ca2+-dependent mechanism in pancreatic β- and INS-1 cells and thereby support the hypothesis that membrane phospholipids regulate ion channel activity by interacting with ion channels.
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Affiliation(s)
- Lizbeth de la Cruz
- Department of Physiology, School of Medicine, Universidad Nacional Autónoma de México (UNAM), Mexico, México
| | - Erika I Puente
- Department of Physiology, School of Medicine, Universidad Nacional Autónoma de México (UNAM), Mexico, México
| | - Arturo Reyes-Vaca
- Department of Physiology, School of Medicine, Universidad Nacional Autónoma de México (UNAM), Mexico, México
| | - Isabel Arenas
- Department of Physiology, School of Medicine, Universidad Nacional Autónoma de México (UNAM), Mexico, México
| | - Julieta Garduño
- Department of Physiology, School of Medicine, Universidad Nacional Autónoma de México (UNAM), Mexico, México
| | - Jorge Bravo-Martínez
- Department of Physiology, School of Medicine, Universidad Nacional Autónoma de México (UNAM), Mexico, México
| | - David E Garcia
- Department of Physiology, School of Medicine, Universidad Nacional Autónoma de México (UNAM), Mexico, México
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Rajani V, Zhang Y, Revill A, Funk G. The role of P2Y1 receptor signaling in central respiratory control. Respir Physiol Neurobiol 2016; 226:3-10. [DOI: 10.1016/j.resp.2015.10.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2015] [Accepted: 10/06/2015] [Indexed: 12/24/2022]
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Abstract
UNLABELLED In neurons, loss of plasma membrane phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] leads to a decrease in exocytosis and changes in electrical excitability. Restoration of PI(4,5)P2 levels after phospholipase C activation is therefore essential for a return to basal neuronal activity. However, the dynamics of phosphoinositide metabolism have not been analyzed in neurons. We measured dynamic changes of PI(4,5)P2, phosphatidylinositol 4-phosphate, diacylglycerol, inositol 1,4,5-trisphosphate, and Ca(2+) upon muscarinic stimulation in sympathetic neurons from adult male Sprague-Dawley rats with electrophysiological and optical approaches. We used this kinetic information to develop a quantitative description of neuronal phosphoinositide metabolism. The measurements and analysis show and explain faster synthesis of PI(4,5)P2 in sympathetic neurons than in electrically nonexcitable tsA201 cells. They can be used to understand dynamic effects of receptor-mediated phospholipase C activation on excitability and other PI(4,5)P2-dependent processes in neurons. SIGNIFICANCE STATEMENT Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] is a minor phospholipid in the cytoplasmic leaflet of the plasma membrane. Depletion of PI(4,5)P2 via phospholipase C-mediated hydrolysis leads to a decrease in exocytosis and alters electrical excitability in neurons. Restoration of PI(4,5)P2 is essential for a return to basal neuronal activity. However, the dynamics of phosphoinositide metabolism have not been analyzed in neurons. We studied the dynamics of phosphoinositide metabolism in sympathetic neurons upon muscarinic stimulation and used the kinetic information to develop a quantitative description of neuronal phosphoinositide metabolism. The measurements and analysis show a several-fold faster synthesis of PI(4,5)P2 in sympathetic neurons than in an electrically nonexcitable cell line, and provide a framework for future studies of PI(4,5)P2-dependent processes in neurons.
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Lu VB, Ikeda SR. Strategies for Investigating G-Protein Modulation of Voltage-Gated Ca2+ Channels. Cold Spring Harb Protoc 2016; 2016:2016/5/pdb.top087072. [PMID: 27140924 DOI: 10.1101/pdb.top087072] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
G-protein-coupled receptor modulation of voltage-gated ion channels is a common means of fine-tuning the response of channels to changes in membrane potential. Such modulation impacts physiological processes such as synaptic transmission, and hence therapeutic strategies often directly or indirectly target these pathways. As an exemplar of channel modulation, we examine strategies for investigating G-protein modulation of CaV2.2 or N-type voltage-gated Ca(2+) channels. We focus on biochemical and genetic tools for defining the molecular mechanisms underlying the various forms of CaV2.2 channel modulation initiated following ligand binding to G-protein-coupled receptors.
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Affiliation(s)
- Van B Lu
- Section on Transmitter Signaling, Laboratory of Molecular Physiology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland 20892-9411
| | - Stephen R Ikeda
- Section on Transmitter Signaling, Laboratory of Molecular Physiology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland 20892-9411
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Rohacs T. Phosphoinositide signaling in somatosensory neurons. Adv Biol Regul 2016; 61:2-16. [PMID: 26724974 PMCID: PMC4884561 DOI: 10.1016/j.jbior.2015.11.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Revised: 11/06/2015] [Accepted: 11/07/2015] [Indexed: 02/03/2023]
Abstract
Somatosensory neurons of the dorsal root ganglia (DRG) and trigeminal ganglia (TG) are responsible for detecting thermal and tactile stimuli. They are also the primary neurons mediating pain and itch. A large number of cell surface receptors in these neurons couple to phospholipase C (PLC) enzymes leading to the hydrolysis of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and the generation of downstream signaling molecules. These neurons also express many different ion channels, several of which are regulated by phosphoinositides. This review will summarize the knowledge on phosphoinositide signaling in DRG neurons, with special focus on effects on sensory and other ion channels.
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Affiliation(s)
- Tibor Rohacs
- Rutgers, New Jersey Medical School, Newark, NJ, USA.
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Jeong JY, Kweon HJ, Suh BC. Dual Regulation of R-Type CaV2.3 Channels by M1 Muscarinic Receptors. Mol Cells 2016; 39:322-9. [PMID: 26923189 PMCID: PMC4844939 DOI: 10.14348/molcells.2016.2292] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 02/03/2016] [Accepted: 02/05/2016] [Indexed: 11/27/2022] Open
Abstract
Voltage-gated Ca(2+) (CaV) channels are dynamically modulated by G protein-coupled receptors (GPCR). The M1 muscarinic receptor stimulation is known to enhance CaV2.3 channel gating through the activation of protein kinase C (PKC). Here, we found that M1 receptors also inhibit CaV2.3 currents when the channels are fully activated by PKC. In whole-cell configuration, the application of phorbol 12-myristate 13-acetate (PMA), a PKC activator, potentiated CaV2.3 currents by ∼two-fold. After the PMA-induced potentiation, stimulation of M1 receptors decreased the CaV2.3 currents by 52 ± 8%. We examined whether the depletion of phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) is responsible for the muscarinic suppression of CaV2.3 currents by using two methods: the Danio rerio voltage-sensing phosphatase (Dr-VSP) system and the rapamycin-induced translocatable pseudojanin (PJ) system. First, dephosphorylation of PI(4,5)P2 to phosphatidylinositol 4-phosphate (PI(4)P) by Dr-VSP significantly suppressed CaV2.3 currents, by 53 ± 3%. Next, dephosphorylation of both PI(4)P and PI(4,5)P2 to PI by PJ translocation further decreased the current by up to 66 ± 3%. The results suggest that CaV2.3 currents are modulated by the M1 receptor in a dual mode-that is, potentiation through the activation of PKC and suppression by the depletion of membrane PI(4,5)P2. Our results also suggest that there is rapid turnover between PI(4)P and PI(4,5)P2 in the plasma membrane.
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Affiliation(s)
- Jin-Young Jeong
- Department of Brain and Cognitive Sciences, DGIST, Daegu 42988,
Korea
| | - Hae-Jin Kweon
- Department of Brain and Cognitive Sciences, DGIST, Daegu 42988,
Korea
| | - Byung-Chang Suh
- Department of Brain and Cognitive Sciences, DGIST, Daegu 42988,
Korea
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Human EAG channels are directly modulated by PIP2 as revealed by electrophysiological and optical interference investigations. Sci Rep 2016; 6:23417. [PMID: 27005320 PMCID: PMC4804213 DOI: 10.1038/srep23417] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 03/03/2016] [Indexed: 11/28/2022] Open
Abstract
Voltage-gated ether à go-go (EAG) K+ channels are expressed in various types of cancer cells and also in the central nervous system. Aberrant overactivation of human EAG1 (hEAG1) channels is associated with cancer and neuronal disorders such as Zimmermann-Laband and Temple-Baraitser syndromes. Although hEAG1 channels are recognized as potential therapeutic targets, regulation of their functional properties is only poorly understood. Here, we show that the membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2) is a potent inhibitory gating modifier of hEAG1 channels. PIP2 inhibits the channel activity by directly binding to a short N-terminal segment of the channel important for Ca2+/calmodulin (CaM) binding as evidenced by bio-layer interferometry measurements. Conversely, depletion of endogenous PIP2 either by serotonin-induced phospholipase C (PLC) activation or by a rapamycin-induced translocation system enhances the channel activity at physiological membrane potentials, suggesting that PIP2 exerts a tonic inhibitory influence. Our study, combining electrophysiological and direct binding assays, demonstrates that hEAG1 channels are subject to potent inhibitory modulation by multiple phospholipids and suggests that manipulations of the PIP2 signaling pathway may represent a strategy to treat hEAG1 channel-associated diseases.
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Thornell IM, Bevensee MO. Phosphatidylinositol 4,5-bisphosphate degradation inhibits the Na+/bicarbonate cotransporter NBCe1-B and -C variants expressed in Xenopus oocytes. J Physiol 2016; 593:541-58. [PMID: 25398525 DOI: 10.1113/jphysiol.2014.284307] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 11/04/2014] [Indexed: 12/16/2022] Open
Abstract
KEY POINTS We previously reported that the phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2 ) directly stimulates heterologously expressed electrogenic Na(+)/bicarbonate cotransporter NBCe1-A in an excised macropatch from the Xenopus oocyte, and indirectly stimulates NBCe1-B and -C in the intact oocyte primarily through inositol 1,4,5-trisphosphate/Ca(2+). In the current study, we expand on a previous observation that PIP2 may also directly stimulate NBCe1 in the intact oocyte. In this study on oocytes, we co-expressed either NBCe1-B or -C and a voltage-sensitive phosphatase (VSP), which depletes PIP2 without changing inositol 1,4,5-trisphosphate, and monitored NBCe1-mediated currents with the two-electrode voltage-clamp technique or pHi changes using Vm/pH-sensitive microelectrodes. Activating VSP inhibited NBCe1-B and -C outward currents and NBCe1-mediated pHi increases, and changes in NBCe1 activity paralleled changes in surface PIP2. This study is a quantitative assessment of PIP2 itself as a regulator of NBCe1-B and -C in the intact cell, and represents the first use of VSP to characterize the PIP2 sensitivity of a transporter. These data combined with our previous work demonstrate that NBCe1-B and -C are regulated by two PIP2-mediated signalling pathways. Specifically, a decrease in PIP2 per se can inhibit NBCe1, whereas hydrolysis of PIP2 to inositol 1,4,5-trisphosphate/Ca(2+) can stimulate the transporter. ABSTRACT The electrogenic Na(+)/bicarbonate cotransporter (NBCe1) of the Slc4 gene family is a powerful regulator of intracellular pH (pHi) and extracellular pH (pHo), and contributes to solute reabsorption and secretion in many epithelia. Using Xenopus laevis oocytes expressing NBCe1 variants, we have previously reported that the phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2) directly stimulates NBCe1-A in an excised macropatch, and indirectly stimulates NBCe1-B and -C in the intact oocyte primarily through inositol 1,4,5-trisphosphate (InsP3)/Ca(2+). In the current study, we used the two-electrode voltage-clamp technique alone or in combination with pH/voltage-sensitive microelectrodes or confocal fluorescence imaging of plasma membrane PIP2 to characterize the PIP2 sensitivity of NBCe1-B and -C in whole oocytes by co-expressing a voltage-sensitive phosphatase (VSP) that decreases PIP2 and bypasses the InsP3/Ca(2+) pathway. An oocyte depolarization that activated VSP only transiently stimulated the NBCe1-B/C current, consistent with an initial rapid depolarization-induced NBCe1 activation, and then a subsequent slower VSP-mediated NBCe1 inhibition. Upon repolarization, the NBCe1 current decreased, and then slowly recovered with an exponential time course that paralleled PIP2 resynthesis as measured with a PIP2-sensitive fluorophore and confocal imaging. A subthreshold depolarization that minimally activated VSP caused a more sustained increase in NBCe1 current, and did not lead to an exponential current recovery following repolarization. Similar results were obtained with oocytes expressing a catalytically dead VSP mutant at all depolarized potentials. Depleting endoplasmic reticulum Ca(2+) did not inhibit the NBCe1 current recovery following repolarization from VSP activation, demonstrating that changes in InsP3/Ca(2+) were not responsible. This study demonstrates for the first time that depleting PIP2 per se inhibits NBCe1 activity. The data in conjunction with previous findings implicate a dual PIP2 regulatory pathway for NBCe1 involving both PIP2 itself and generated InsP3/Ca(2+).
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Affiliation(s)
- Ian M Thornell
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
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Abstract
Existing analgesics are not efficacious in treating all patients with chronic pain and have harmful side effects when used long term. A deeper understanding of pain signaling and sensitization could lead to the development of more efficacious analgesics. Nociceptor sensitization occurs under conditions of inflammation and nerve injury where diverse chemicals are released and signal through receptors to reduce the activation threshold of ion channels, leading to an overall increase in neuronal excitability. Drugs that inhibit specific receptors have so far been unsuccessful in alleviating pain, possibly because they do not simultaneously target the diverse receptors that contribute to nociceptor sensitization. Hence, the focus has shifted toward targeting downstream convergence points of nociceptive signaling. Lipid mediators, including phosphatidylinositol 4,5-bisphosphate (PIP2), are attractive targets, as these molecules are required for signaling downstream of G-protein-coupled receptors and receptor tyrosine kinases. Furthermore, PIP2 regulates the activity of various ion channels. Thus, PIP2 sits at a critical convergence point for multiple receptors, ion channels, and signaling pathways that promote and maintain chronic pain. Decreasing the amount of PIP2 in neurons was recently shown to attenuate pronociceptive signaling and could provide a novel approach for treating pain. Here, we review the lipid kinases that are known to regulate pain signaling and sensitization and speculate on which additional lipid kinases might regulate signaling in nociceptive neurons.
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López Soto EJ, Agosti F, Cabral A, Mustafa ER, Damonte VM, Gandini MA, Rodríguez S, Castrogiovanni D, Felix R, Perelló M, Raingo J. Constitutive and ghrelin-dependent GHSR1a activation impairs CaV2.1 and CaV2.2 currents in hypothalamic neurons. ACTA ACUST UNITED AC 2015; 146:205-19. [PMID: 26283199 PMCID: PMC4555474 DOI: 10.1085/jgp.201511383] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 07/13/2015] [Indexed: 12/22/2022]
Abstract
Constitutive and ligand-dependent GHSR1a activity attenuates CaV2 current and hypothalamic GABA release through distinct mechanisms and signaling pathways. The growth hormone secretagogue receptor type 1a (GHSR1a) has the highest known constitutive activity of any G protein–coupled receptor (GPCR). GHSR1a mediates the action of the hormone ghrelin, and its activation increases transcriptional and electrical activity in hypothalamic neurons. Although GHSR1a is present at GABAergic presynaptic terminals, its effect on neurotransmitter release remains unclear. The activities of the voltage-gated calcium channels, CaV2.1 and CaV2.2, which mediate neurotransmitter release at presynaptic terminals, are modulated by many GPCRs. Here, we show that both constitutive and agonist-dependent GHSR1a activity elicit a strong impairment of CaV2.1 and CaV2.2 currents in rat and mouse hypothalamic neurons and in a heterologous expression system. Constitutive GHSR1a activity reduces CaV2 currents by a Gi/o-dependent mechanism that involves persistent reduction in channel density at the plasma membrane, whereas ghrelin-dependent GHSR1a inhibition is reversible and involves altered CaV2 gating via a Gq-dependent pathway. Thus, GHSR1a differentially inhibits CaV2 channels by Gi/o or Gq protein pathways depending on its mode of activation. Moreover, we present evidence suggesting that GHSR1a-mediated inhibition of CaV2 attenuates GABA release in hypothalamic neurons, a mechanism that could contribute to neuronal activation through the disinhibition of postsynaptic neurons.
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Affiliation(s)
- Eduardo Javier López Soto
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Francina Agosti
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Agustina Cabral
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Emilio Roman Mustafa
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Valentina Martínez Damonte
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Maria Alejandra Gandini
- Department of Cell Biology, Center for Research and Advanced Studies of the National Polytechnic Institute, 07000 México D.F., México
| | - Silvia Rodríguez
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Daniel Castrogiovanni
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Ricardo Felix
- Department of Cell Biology, Center for Research and Advanced Studies of the National Polytechnic Institute, 07000 México D.F., México
| | - Mario Perelló
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Jesica Raingo
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
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Huang D, Huang S, Peers C, Du X, Zhang H, Gamper N. GABAB receptors inhibit low-voltage activated and high-voltage activated Ca(2+) channels in sensory neurons via distinct mechanisms. Biochem Biophys Res Commun 2015; 465:188-93. [PMID: 26239659 DOI: 10.1016/j.bbrc.2015.07.137] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 07/28/2015] [Indexed: 12/16/2022]
Abstract
Growing evidence suggests that mammalian peripheral somatosensory neurons express functional receptors for gamma-aminobutyric acid, GABAA and GABAB. Moreover, local release of GABA by pain-sensing (nociceptive) nerve fibres has also been suggested. Yet, the functional significance of GABA receptor triggering in nociceptive neurons is not fully understood. Here we used patch-clamp recordings from small-diameter cultured DRG neurons to investigate effects of GABAB receptor agonist baclofen on voltage-gated Ca(2+) currents. We found that baclofen inhibited both low-voltage activated (LVA, T-type) and high-voltage activated (HVA) Ca(2+) currents in a proportion of DRG neurons by 22% and 32% respectively; both effects were sensitive to Gi/o inhibitor pertussis toxin. Inhibitory effect of baclofen on both current types was about twice less efficacious as compared to that of the μ-opioid receptor agonist DAMGO. Surprisingly, only HVA but not LVA current modulation by baclofen was partially prevented by G protein inhibitor GDP-β-S. In contrast, only LVA but not HVA current modulation was reversed by the application of a reducing agent dithiothreitol (DTT). Inhibition of T-type Ca(2+) current by baclofen and the recovery of such inhibition by DTT were successfully reconstituted in the expression system. Our data suggest that inhibition of LVA current in DRG neurons by baclofen is partially mediated by an unconventional signaling pathway that involves a redox mechanism. These findings reinforce the idea of targeting peripheral GABA receptors for pain relief.
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Affiliation(s)
- Dongyang Huang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, 050011, PR China
| | - Sha Huang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, 050011, PR China
| | - Chris Peers
- Faculty of Medicine and Health, University of Leeds, Leeds, UK
| | - Xiaona Du
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, 050011, PR China
| | - Hailin Zhang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, 050011, PR China.
| | - Nikita Gamper
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, 050011, PR China; School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, UK.
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Costimulation of AMPA and metabotropic glutamate receptors underlies phospholipase C activation by glutamate in hippocampus. J Neurosci 2015; 35:6401-12. [PMID: 25904792 DOI: 10.1523/jneurosci.4208-14.2015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Glutamate, a major neurotransmitter in the brain, activates ionotropic and metabotropic glutamate receptors (iGluRs and mGluRs, respectively). The two types of glutamate receptors interact with each other, as exemplified by the modulation of iGluRs by mGluRs. However, the other way of interaction (i.e., modulation of mGluRs by iGluRs) has not received much attention. In this study, we found that group I mGluR-specific agonist (RS)-3,5-dihydroxyphenylglycine (DHPG) alone is not sufficient to activate phospholipase C (PLC) in rat hippocampus, while glutamate robustly activates PLC. These results suggested that additional mechanisms provided by iGluRs are involved in group I mGluR-mediated PLC activation. A series of experiments demonstrated that glutamate-induced PLC activation is mediated by mGluR5 and is facilitated by local Ca(2+) signals that are induced by AMPA-mediated depolarization and L-type Ca(2+) channel activation. Finally, we found that PLC and L-type Ca(2+) channels are involved in hippocampal mGluR-dependent long-term depression (mGluR-LTD) induced by paired-pulse low-frequency stimulation, but not in DHPG-induced chemical LTD. Together, we propose that AMPA receptors initiate Ca(2+) influx via the L-type Ca(2+) channels that facilitate mGluR5-PLC signaling cascades, which underlie mGluR-LTD in rat hippocampus.
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Phosphoinositide dynamics in the postsynaptic membrane compartment: Mechanisms and experimental approach. Eur J Cell Biol 2015; 94:401-14. [DOI: 10.1016/j.ejcb.2015.06.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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Kaur G, Pinggera A, Ortner NJ, Lieb A, Sinnegger-Brauns MJ, Yarov-Yarovoy V, Obermair GJ, Flucher BE, Striessnig J. A Polybasic Plasma Membrane Binding Motif in the I-II Linker Stabilizes Voltage-gated CaV1.2 Calcium Channel Function. J Biol Chem 2015; 290:21086-21100. [PMID: 26100638 PMCID: PMC4543666 DOI: 10.1074/jbc.m115.645671] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Indexed: 12/27/2022] Open
Abstract
L-type voltage-gated Ca(2+) channels (LTCCs) regulate many physiological functions like muscle contraction, hormone secretion, gene expression, and neuronal excitability. Their activity is strictly controlled by various molecular mechanisms. The pore-forming α1-subunit comprises four repeated domains (I-IV), each connected via an intracellular linker. Here we identified a polybasic plasma membrane binding motif, consisting of four arginines, within the I-II linker of all LTCCs. The primary structure of this motif is similar to polybasic clusters known to interact with polyphosphoinositides identified in other ion channels. We used de novo molecular modeling to predict the conformation of this polybasic motif, immunofluorescence microscopy and live cell imaging to investigate the interaction with the plasma membrane, and electrophysiology to study its role for Cav1.2 channel function. According to our models, this polybasic motif of the I-II linker forms a straight α-helix, with the positive charges facing the lipid phosphates of the inner leaflet of the plasma membrane. Membrane binding of the I-II linker could be reversed after phospholipase C activation, causing polyphosphoinositide breakdown, and was accelerated by elevated intracellular Ca(2+) levels. This indicates the involvement of negatively charged phospholipids in the plasma membrane targeting of the linker. Neutralization of four arginine residues eliminated plasma membrane binding. Patch clamp recordings revealed facilitated opening of Cav1.2 channels containing these mutations, weaker inhibition by phospholipase C activation, and reduced expression of channels (as quantified by ON-gating charge) at the plasma membrane. Our data provide new evidence for a membrane binding motif within the I-II linker of LTCC α1-subunits essential for stabilizing normal Ca(2+) channel function.
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Affiliation(s)
- Gurjot Kaur
- Institute of Pharmacy, Department of Pharmacology and Toxicology, and Center for Molecular Biosciences, University of Innsbruck, A-6020 Innsbruck, Austria
| | - Alexandra Pinggera
- Institute of Pharmacy, Department of Pharmacology and Toxicology, and Center for Molecular Biosciences, University of Innsbruck, A-6020 Innsbruck, Austria
| | - Nadine J Ortner
- Institute of Pharmacy, Department of Pharmacology and Toxicology, and Center for Molecular Biosciences, University of Innsbruck, A-6020 Innsbruck, Austria
| | - Andreas Lieb
- Institute of Pharmacy, Department of Pharmacology and Toxicology, and Center for Molecular Biosciences, University of Innsbruck, A-6020 Innsbruck, Austria
| | - Martina J Sinnegger-Brauns
- Institute of Pharmacy, Department of Pharmacology and Toxicology, and Center for Molecular Biosciences, University of Innsbruck, A-6020 Innsbruck, Austria
| | - Vladimir Yarov-Yarovoy
- Department of Physiology and Membrane Biology, UC Davis School of Medicine, Davis, California 95616
| | - Gerald J Obermair
- Division of Physiology, Medical University of Innsbruck, A-6020 Innsbruck, Austria
| | - Bernhard E Flucher
- Division of Physiology, Medical University of Innsbruck, A-6020 Innsbruck, Austria
| | - Jörg Striessnig
- Institute of Pharmacy, Department of Pharmacology and Toxicology, and Center for Molecular Biosciences, University of Innsbruck, A-6020 Innsbruck, Austria.
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Thornell IM, Bevensee MO. Regulators of Slc4 bicarbonate transporter activity. Front Physiol 2015; 6:166. [PMID: 26124722 PMCID: PMC4464172 DOI: 10.3389/fphys.2015.00166] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 05/15/2015] [Indexed: 12/11/2022] Open
Abstract
The Slc4 family of transporters is comprised of anion exchangers (AE1-4), Na+-coupled bicarbonate transporters (NCBTs) including electrogenic Na/bicarbonate cotransporters (NBCe1 and NBCe2), electroneutral Na/bicarbonate cotransporters (NBCn1 and NBCn2), and the electroneutral Na-driven Cl-bicarbonate exchanger (NDCBE), as well as a borate transporter (BTR1). These transporters regulate intracellular pH (pHi) and contribute to steady-state pHi, but are also involved in other physiological processes including CO2 carriage by red blood cells and solute secretion/reabsorption across epithelia. Acid-base transporters function as either acid extruders or acid loaders, with the Slc4 proteins moving HCO−3 either into or out of cells. According to results from both molecular and functional studies, multiple Slc4 proteins and/or associated splice variants with similar expected effects on pHi are often found in the same tissue or cell. Such apparent redundancy is likely to be physiologically important. In addition to regulating pHi, a HCO−3 transporter contributes to a cell's ability to fine tune the intracellular regulation of the cotransported/exchanged ion(s) (e.g., Na+ or Cl−). In addition, functionally similar transporters or splice variants with different regulatory profiles will optimize pH physiology and solute transport under various conditions or within subcellular domains. Such optimization will depend on activated signaling pathways and transporter expression profiles. In this review, we will summarize and discuss both well-known and more recently identified regulators of the Slc4 proteins. Some of these regulators include traditional second messengers, lipids, binding proteins, autoregulatory domains, and less conventional regulators. The material presented will provide insight into the diversity and physiological significance of multiple members within the Slc4 gene family.
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Affiliation(s)
- Ian M Thornell
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham Birmingham, AL, USA
| | - Mark O Bevensee
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham Birmingham, AL, USA ; Nephrology Research and Training Center, University of Alabama at Birmingham Birmingham, AL, USA ; Center of Glial Biology in Medicine, University of Alabama at Birmingham Birmingham, AL, USA ; Civitan International Research Center, University of Alabama at Birmingham Birmingham, AL, USA
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