1
|
Davenport CM, Teubner BJW, Han SB, Patton MH, Eom TY, Garic D, Lansdell BJ, Shirinifard A, Chang TC, Klein J, Pruett-Miller SM, Blundon JA, Zakharenko SS. Innate frequency-discrimination hyperacuity in Williams-Beuren syndrome mice. Cell 2022; 185:3877-3895.e21. [PMID: 36152627 PMCID: PMC9588278 DOI: 10.1016/j.cell.2022.08.022] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 06/14/2022] [Accepted: 08/24/2022] [Indexed: 01/26/2023]
Abstract
Williams-Beuren syndrome (WBS) is a rare disorder caused by hemizygous microdeletion of ∼27 contiguous genes. Despite neurodevelopmental and cognitive deficits, individuals with WBS have spared or enhanced musical and auditory abilities, potentially offering an insight into the genetic basis of auditory perception. Here, we report that the mouse models of WBS have innately enhanced frequency-discrimination acuity and improved frequency coding in the auditory cortex (ACx). Chemogenetic rescue showed frequency-discrimination hyperacuity is caused by hyperexcitable interneurons in the ACx. Haploinsufficiency of one WBS gene, Gtf2ird1, replicated WBS phenotypes by downregulating the neuropeptide receptor VIPR1. VIPR1 is reduced in the ACx of individuals with WBS and in the cerebral organoids derived from human induced pluripotent stem cells with the WBS microdeletion. Vipr1 deletion or overexpression in ACx interneurons mimicked or reversed, respectively, the cellular and behavioral phenotypes of WBS mice. Thus, the Gtf2ird1-Vipr1 mechanism in ACx interneurons may underlie the superior auditory acuity in WBS.
Collapse
Affiliation(s)
- Christopher M Davenport
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Brett J W Teubner
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Seung Baek Han
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Mary H Patton
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Tae-Yeon Eom
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Dusan Garic
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Benjamin J Lansdell
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Abbas Shirinifard
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Ti-Cheng Chang
- Center for Applied Bioinformatics, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Jonathon Klein
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Shondra M Pruett-Miller
- Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Jay A Blundon
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Stanislav S Zakharenko
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
| |
Collapse
|
2
|
Wang J, Zhang H, Yin X, Bian Y. Anti-CD47 antibody synergizes with cisplatin against laryngeal cancer by enhancing phagocytic ability of macrophages. Clin Exp Immunol 2021; 205:333-342. [PMID: 33999416 DOI: 10.1111/cei.13618] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2021] [Revised: 04/23/2021] [Accepted: 05/03/2021] [Indexed: 01/25/2023] Open
Abstract
Cisplatin is mainly used in late-stage or recurrent laryngeal cancer patients. However, the effect of the chemotherapy is limited due to cisplatin resistance. Therefore, we explored the synergized role of immunosuppressive mediator with cisplatin in laryngeal cancer. Cancer cells isolated from tissues of patients with laryngeal cancer were treated with cisplatin to screen the potential immunosuppressive mediator, whose synergized effects with cisplatin were explored both in vivo and in vitro. CD47 was selected for its high expression in cisplatin-treated laryngeal cancer cells. Blocking CD47 expression using its neutralizing antibody (aCD47) synergized with cisplatin to increase macrophage phagocytosis in a co-culture system of human epithelial type 2 (Hep-2) cancer cells with tumor-associated macrophages (TAMs). Moreover, aCD47 together with cisplatin prevented tumor growth by inhibiting proliferation of cancer cells and the secretion of proinflammatory cytokines, as well as by inducing the apoptosis of cancer cells and phagocytosis of TAMs in a Hep-2-implanted mouse tumor model. aCD47 synergized with cisplatin against laryngeal cancer by enhancing the phagocytic ability of TAMs, and the combined therapy of cisplatin and aCD47 might serve as a novel therapeutic strategy against laryngeal cancer.
Collapse
Affiliation(s)
- Jingmiao Wang
- The First Department of Otorhinolaryngology, the Second Hospital of Hebei Medical University, Shijiazhuang, Hebei, China
| | - Haizhong Zhang
- The First Department of Otorhinolaryngology, the Second Hospital of Hebei Medical University, Shijiazhuang, Hebei, China
| | - Xiaoyan Yin
- The First Department of Otorhinolaryngology, the Second Hospital of Hebei Medical University, Shijiazhuang, Hebei, China
| | - Yanrui Bian
- The First Department of Otorhinolaryngology, the Second Hospital of Hebei Medical University, Shijiazhuang, Hebei, China
| |
Collapse
|
3
|
Cunha-Reis D, Caulino-Rocha A, Correia-de-Sá P. VIPergic neuroprotection in epileptogenesis: challenges and opportunities. Pharmacol Res 2021; 164:105356. [DOI: 10.1016/j.phrs.2020.105356] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 11/28/2020] [Accepted: 11/29/2020] [Indexed: 12/19/2022]
|
4
|
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.
Collapse
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
| |
Collapse
|
5
|
Li Z, He SQ, Tseng PY, Xu Q, Tiwari V, Yang F, Shu B, Zhang T, Tang Z, Raja SN, Wang Y, Dong X, Guan Y. The inhibition of high-voltage-activated calcium current by activation of MrgC11 involves phospholipase C-dependent mechanisms. Neuroscience 2015; 300:393-403. [PMID: 26022362 DOI: 10.1016/j.neuroscience.2015.05.043] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Revised: 05/05/2015] [Accepted: 05/18/2015] [Indexed: 01/27/2023]
Abstract
High-voltage-activated (HVA) calcium channels play an important role in synaptic transmission. Activation of Mas-related G-protein-coupled receptor subtype C (MrgC; mouse MrgC11, rat homolog rMrgC) inhibits HVA calcium current (ICa) in small-diameter dorsal root ganglion (DRG) neurons, but the intracellular signaling cascade underlying MrgC agonist-induced inhibition of HVA ICa in native DRG neurons remains unclear. To address this question, we conducted patch-clamp recordings in MrgA3-eGFP-wild-type mice, in which most MrgA3-eGFP(+) DRG neurons co-express MrgC11 and can be identified for recording. We found that the inhibition of HVA ICa by JHU58 (0.001-100nM, a dipeptide, MrgC-selective agonist) was significantly reduced by pretreatment with a phospholipase C (PLC) inhibitor (U73122, 1μM), but not by its inactive analog (U73343) or vehicle. Further, in rats that had undergone spinal nerve injury, pretreatment with intrathecal U73122 nearly abolished the inhibition of mechanical hypersensitivity by intrathecal JHU58. The inhibition of HVA ICa in MrgA3-eGFP(+) neurons by JHU58 (100nM) was partially reduced by pretreatment with a Gβγ blocker (gallein, 100μM). However, applying a depolarizing prepulse and blocking the Gαi and Gαs pathways with pertussis toxin (PTX) (0.5μg/mL) and cholera toxin (CTX) (0.5μg/mL), respectively, had no effect. These findings suggest that activation of MrgC11 may inhibit HVA ICa in mouse DRG neurons through a voltage-independent mechanism that involves activation of the PLC, but not Gαi or Gαs, pathway.
Collapse
Affiliation(s)
- Z Li
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - S-Q He
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - P-Y Tseng
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - Q Xu
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - V Tiwari
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - F Yang
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - B Shu
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA; Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Wuhan 430030, China
| | - T Zhang
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA; Department of Neurology, Beijing Tiantan Hospital, Capital Medical University, Beijing 100050, China
| | - Z Tang
- Nanjing University of Chinese Medicine, 138 Xianlin Road, Nanjing, Jiangsu 210023, China
| | - S N Raja
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - Y Wang
- Department of Anesthesiology, Beijing Chaoyang Hospital, Capital Medical University, Beijing 100020, China
| | - X Dong
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA; Howard Hughes Medical Institute, Johns Hopkins University, School of Medicine, Baltimore, MD 21287, USA.
| | - Y Guan
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA.
| |
Collapse
|
6
|
Proft J, Weiss N. G protein regulation of neuronal calcium channels: back to the future. Mol Pharmacol 2014; 87:890-906. [PMID: 25549669 DOI: 10.1124/mol.114.096008] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 12/30/2014] [Indexed: 11/22/2022] Open
Abstract
Neuronal voltage-gated calcium channels have evolved as one of the most important players for calcium entry into presynaptic endings responsible for the release of neurotransmitters. In turn, and to fine-tune synaptic activity and neuronal communication, numerous neurotransmitters exert a potent negative feedback over the calcium signal provided by G protein-coupled receptors. This regulation pathway of physiologic importance is also extensively exploited for therapeutic purposes, for instance in the treatment of neuropathic pain by morphine and other μ-opioid receptor agonists. However, despite more than three decades of intensive research, important questions remain unsolved regarding the molecular and cellular mechanisms of direct G protein inhibition of voltage-gated calcium channels. In this study, we revisit this particular regulation and explore new considerations.
Collapse
Affiliation(s)
- Juliane Proft
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Norbert Weiss
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| |
Collapse
|
7
|
Agosti F, López Soto EJ, Cabral A, Castrogiovanni D, Schioth HB, Perelló M, Raingo J. Melanocortin 4 receptor activation inhibits presynaptic N-type calcium channels in amygdaloid complex neurons. Eur J Neurosci 2014; 40:2755-65. [PMID: 24943127 DOI: 10.1111/ejn.12650] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Revised: 04/30/2014] [Accepted: 05/05/2014] [Indexed: 12/22/2022]
Abstract
The melanocortin 4 receptor (MC4R) is a G protein-coupled receptor involved in food intake and energy expenditure regulation. MC4R activation modifies neuronal activity but the molecular mechanisms by which this regulation occurs remain unclear. Here, we tested the hypothesis that MC4R activation regulates the activity of voltage-gated calcium channels and, as a consequence, synaptic activity. We also tested whether the proposed effect occurs in the amygdala, a brain area known to mediate the anorexigenic actions of MC4R signaling. Using the patch-clamp technique, we found that the activation of MC4R with its agonist melanotan II specifically inhibited 34.5 ± 1.5% of N-type calcium currents in transiently transfected HEK293 cells. This inhibition was concentration-dependent, voltage-independent and occluded by the Gαs pathway inhibitor cholera toxin. Moreover, we found that melanotan II specifically inhibited 25.9 ± 2.0% of native N-type calcium currents and 55.4 ± 14.4% of evoked inhibitory postsynaptic currents in mouse cultured amygdala neurons. In vivo, we found that the MC4R agonist RO27-3225 increased the marker of cellular activity c-Fos in several components of the amygdala, whereas the N-type channel blocker ω conotoxin GVIA increased c-Fos expression exclusively in the central subdivision of the amygdala. Thus, MC4R specifically inhibited the presynaptic N-type channel subtype, and this inhibition may be important for the effects of melanocortin in the central subdivision of the amygdala.
Collapse
Affiliation(s)
- Francina Agosti
- Laboratory of Electrophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA), La Plata, Buenos Aires, Argentina
| | | | | | | | | | | | | |
Collapse
|
8
|
Lu VB, Puhl HL, Ikeda SR. N-Arachidonyl glycine does not activate G protein-coupled receptor 18 signaling via canonical pathways. Mol Pharmacol 2012; 83:267-82. [PMID: 23104136 DOI: 10.1124/mol.112.081182] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Recent studies propose that N-arachidonyl glycine (NAGly), a carboxylic analogue of anandamide, is an endogenous ligand of the Gα(i/o) protein-coupled receptor 18 (GPR18). However, a high-throughput β-arrestin-based screen failed to detect activation of GPR18 by NAGly (Yin et al., 2009; JBC, 18:12328). To address this inconsistency, this study investigated GPR18 coupling in a native neuronal system with endogenous signaling pathways and effectors. GPR18 was heterologously expressed in rat sympathetic neurons, and the modulation of N-type (Ca(v)2.2) calcium channels was examined. Proper expression and trafficking of receptor were confirmed by the "rim-like" fluorescence of fluorescently tagged receptor and the positive staining of external hemagglutinin-tagged GPR18-expressing cells. Application of NAGly on GPR18-expressing neurons did not inhibit calcium currents but instead potentiated currents in a voltage-dependent manner, similar to what has previously been reported (Guo et al., 2008; J Neurophysiol, 100:1147). Other proposed agonists of GPR18, including anandamide and abnormal cannabidiol, also failed to induce inhibition of calcium currents. Mutants of GPR18, designed to constitutively activate receptors, did not tonically inhibit calcium currents, indicating a lack of GPR18 activation or coupling to endogenous G proteins. Other downstream effectors of Gα(i/o)-coupled receptors, G protein-coupled inwardly rectifying potassium channels and adenylate cyclase, were not modulated by GPR18 signaling. Furthermore, GPR18 did not couple to other G proteins tested: Gα(s), Gα(z), and Gα(15). These results suggest NAGly is not an agonist for GPR18 or that GPR18 signaling involves noncanonical pathways not examined in these studies.
Collapse
Affiliation(s)
- Van B Lu
- Laboratory of Molecular Physiology, National Institutes of Health/National Institute on Alcohol Abuse and Alcoholism, 5625 Fishers Lane, Room TS-11, MSC 9411, Bethesda, MD 20892, USA.
| | | | | |
Collapse
|
9
|
Zamponi GW, Currie KPM. Regulation of Ca(V)2 calcium channels by G protein coupled receptors. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:1629-43. [PMID: 23063655 DOI: 10.1016/j.bbamem.2012.10.004] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 10/02/2012] [Accepted: 10/04/2012] [Indexed: 12/29/2022]
Abstract
Voltage gated calcium channels (Ca²⁺ channels) are key mediators of depolarization induced calcium influx into excitable cells, and thereby play pivotal roles in a wide array of physiological responses. This review focuses on the inhibition of Ca(V)2 (N- and P/Q-type) Ca²⁺-channels by G protein coupled receptors (GPCRs), which exerts important autocrine/paracrine control over synaptic transmission and neuroendocrine secretion. Voltage-dependent inhibition is the most widespread mechanism, and involves direct binding of the G protein βγ dimer (Gβγ) to the α1 subunit of Ca(V)2 channels. GPCRs can also recruit several other distinct mechanisms including phosphorylation, lipid signaling pathways, and channel trafficking that result in voltage-independent inhibition. Current knowledge of Gβγ-mediated inhibition is reviewed, including the molecular interactions involved, determinants of voltage-dependence, and crosstalk with other cell signaling pathways. A summary of recent developments in understanding the voltage-independent mechanisms prominent in sympathetic and sensory neurons is also included. This article is part of a Special Issue entitled: Calcium channels.
Collapse
Affiliation(s)
- Gerald W Zamponi
- Department of Physiology & Pharmacology, Hotchkiss Brain Institute, University of Calgary, Canada
| | | |
Collapse
|
10
|
Betke KM, Wells CA, Hamm HE. GPCR mediated regulation of synaptic transmission. Prog Neurobiol 2012; 96:304-21. [PMID: 22307060 DOI: 10.1016/j.pneurobio.2012.01.009] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2011] [Revised: 01/12/2012] [Accepted: 01/20/2012] [Indexed: 02/06/2023]
Abstract
Synaptic transmission is a finely regulated mechanism of neuronal communication. The release of neurotransmitter at the synapse is not only the reflection of membrane depolarization events, but rather, is the summation of interactions between ion channels, G protein coupled receptors, second messengers, and the exocytotic machinery itself which exposes the components within a synaptic vesicle to the synaptic cleft. The focus of this review is to explore the role of G protein signaling as it relates to neurotransmission, as well as to discuss the recently determined inhibitory mechanism of Gβγ dimers acting directly on the exocytotic machinery proteins to inhibit neurotransmitter release.
Collapse
Affiliation(s)
- Katherine M Betke
- Vanderbilt University Medical Center, 442 Robinson Research Building, 23rd Ave. South @ Pierce, Nashville, TN 37232-6600, USA.
| | | | | |
Collapse
|
11
|
Won YJ, Ono F, Ikeda SR. Identification and modulation of voltage-gated Ca2+ currents in zebrafish Rohon-Beard neurons. J Neurophysiol 2010; 105:442-53. [PMID: 20962070 DOI: 10.1152/jn.00625.2010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Electrically excitable cells have voltage-dependent ion channels on the plasma membrane that regulate membrane permeability to specific ions. Voltage-gated Ca(2+) channels (VGCCs) are especially important as Ca(2+) serves as both a charge carrier and second messenger. Zebrafish (Danio rerio) are an important model vertebrate for studies of neuronal excitability, circuits, and behavior. However, electrophysiological properties of zebrafish VGCCs remain largely unexplored because a suitable preparation for whole cell voltage-clamp studies is lacking. Rohon-Beard (R-B) sensory neurons represent an attractive candidate for this purpose because of their relatively large somata and functional homology to mammalian dorsal root ganglia (DRG) neurons. Transgenic zebrafish expressing green fluorescent protein in R-B neurons, (Isl2b:EGFP)(ZC7), were used to identify dissociated neurons suitable for whole cell patch-clamp experiments. Based on biophysical and pharmacological properties, zebrafish R-B neurons express both high- and low-voltage-gated Ca(2+) current (HVA- and LVA-I(Ca), respectively). Ni(+)-sensitive LVA-I(Ca) occur in the minority of R-B neurons (30%) and ω-conotoxin GVIA-sensitive Ca(V)2.2 (N-type) Ca(2+) channels underlie the vast majority (90%) of HVA-I(Ca). To identify G protein coupled receptors (GPCRs) that modulate HVA-I(Ca), a panel of neurotransmitters was screened. Application of GABA/baclofen or serotonin produced a voltage-dependent inhibition while application of the mu-opioid agonist DAMGO resulted in a voltage-independent inhibition. Unlike in mammalian neurons, GPCR-mediated voltage-dependent modulation of I(Ca) appears to be transduced primarily via a cholera toxin-sensitive Gα subunit. These results provide the basis for using the zebrafish model system to understanding Ca(2+) channel function, and in turn, how Ca(2+) channels contribute to mechanosensory function.
Collapse
Affiliation(s)
- Yu-Jin Won
- 1Section on Transmitter Signaling, Laboratory of Molecular Physiology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland 20892-9411, USA
| | | | | |
Collapse
|
12
|
Tompkins JD, Girard BM, Vizzard MA, Parsons RL. VIP and PACAP effects on mouse major pelvic ganglia neurons. J Mol Neurosci 2010; 42:390-6. [PMID: 20428965 DOI: 10.1007/s12031-010-9367-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Accepted: 04/06/2010] [Indexed: 12/18/2022]
Abstract
Major pelvic ganglia (MPG) neurons innervate urogenital organs and components of the lower bowel. Immunoreactivity for vasoactive intestinal polypeptide (VIP) has previously been observed in the MPG, and VIP knockout animals have impaired micturition reflexes suggesting a role for this neuropeptide in urogenital function. Here, we investigate the presence and action of VIP and a related neuropeptide, pituitary adenylate cyclase activating polypeptide (PACAP), in the pelvic ganglia of male mice. An abundance of VIP-immunoreactive (IR) neurons and nerve fibers were observed in the ganglion, whereas PACAP immunoreactivity was not seen. Extracts from acutely isolated MPG contained transcripts for the VPAC1, VPAC2, and PAC1 receptors. Local application of VIP, PACAP, or maxadilan to isolated pelvic ganglion neurons shortened the duration of the afterhyperpolarization (AHP) of action potentials elicited by brief intracellular depolarization. All three peptides also increased neuronal excitability within a subpopulation of the sampled neurons. Bath application of apamin, a peptide antagonist of SK channels, shortened the duration of the AHP indicating that AHP duration in pelvic neurons is determined principally by SK-channel activity. The results suggest that VIP has a role in the neural control of pelvic organ function and activation of VPAC and/or PAC1 receptors can modulate the activity of the autonomic neurons innervating pelvic organs.
Collapse
Affiliation(s)
- John D Tompkins
- Departments of Anatomy and Neurobiology, College of Medicine, University of Vermont, Burlington, VT 05405, USA.
| | | | | | | |
Collapse
|
13
|
Thapliyal A, Bannister RA, Hanks C, Adams BA. The monomeric G proteins AGS1 and Rhes selectively influence Galphai-dependent signaling to modulate N-type (CaV2.2) calcium channels. Am J Physiol Cell Physiol 2008; 295:C1417-26. [PMID: 18815223 DOI: 10.1152/ajpcell.00341.2008] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Activator of G protein Signaling 1 (AGS1) and Ras homologue enriched in striatum (Rhes) define a new group of Ras-like monomeric G proteins whose signaling properties and physiological roles are just beginning to be understood. Previous results suggest that AGS1 and Rhes exhibit distinct preferences for heterotrimeric G proteins, with AGS1 selectively influencing Galphai and Rhes selectively influencing Galphas. Here, we demonstrate that AGS1 and Rhes trigger nearly identical modulation of N-type Ca(2+) channels (Ca(V)2.2) by selectively altering Galphai-dependent signaling. Whole-cell currents were recorded from HEK293 cells expressing Ca(V)2.2 and Galphai- or Galphas-coupled receptors. AGS1 and Rhes reduced basal current densities and triggered tonic voltage-dependent (VD) inhibition of Ca(V)2.2. Additionally, each protein attenuated agonist-initiated channel inhibition through Galphai-coupled receptors without reducing channel inhibition through a Galphas-coupled receptor. The above effects of AGS1 and Rhes were blocked by pertussis toxin (PTX) or by expression of a Gbetagamma-sequestering peptide (masGRK3ct). Transfection with HRas, KRas2, Rap1A-G12V, Rap2B, Rheb2, or Gem failed to duplicate the effects of AGS1 and Rhes on Ca(V)2.2. Our data provide the first demonstration that AGS1 and Rhes exhibit similar if not identical signaling properties since both trigger tonic Gbetagamma signaling and both attenuate receptor-initiated signaling by the Gbetagamma subunits of PTX-sensitive G proteins. These results are consistent with the possibility that AGS1 and Rhes modulate Ca(2+) influx through Ca(V)2.2 channels under more physiological conditions and thereby influence Ca(2+)-dependent events such as neurosecretion.
Collapse
Affiliation(s)
- Ashish Thapliyal
- Dept. of Biology, Utah State Univ., 5305 Old Main Hill, Logan, UT 84322, USA
| | | | | | | |
Collapse
|
14
|
The mGlu(4) receptor allosteric modulator N-phenyl-7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxamide acts as a direct agonist at mGlu(6) receptors. Eur J Pharmacol 2008; 589:49-52. [PMID: 18593581 DOI: 10.1016/j.ejphar.2008.06.054] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Revised: 06/10/2008] [Accepted: 06/15/2008] [Indexed: 11/21/2022]
Abstract
Effects of the mGlu(4) receptor allosteric modulator N-phenyl-7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxamide (PHCCC) were tested on closely related mGlu6 receptors. Modulation of native calcium currents in isolated sympathetic neurons from rat superior cervical ganglion by expressed mGlu(4) and mGlu(6) receptor was used to assay receptor activity. Glutamate concentration-response curves with and without PHCCC confirmed that the drug is an allosteric modulator of mGlu(4) receptor, without direct agonist activity. Conversely, PHCCC directly activates the mGlu(6) receptor and does not enhance activity of glutamate. Therefore, PHCCC is a direct mGlu(6) receptor agonist, but lacks allosteric modulatory properties.
Collapse
|
15
|
Guo J, Williams DJ, Puhl HL, Ikeda SR. Inhibition of N-Type Calcium Channels by Activation of GPR35, an Orphan Receptor, Heterologously Expressed in Rat Sympathetic Neurons. J Pharmacol Exp Ther 2007; 324:342-51. [DOI: 10.1124/jpet.107.127266] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
|
16
|
Abstract
The regulation of presynaptic, voltage-gated calcium channels by activation of heptahelical G protein-coupled receptors exerts a crucial influence on presynaptic calcium entry and hence on neurotransmitter release. Receptor activation subjects presynaptic N- and P/Q-type calcium channels to a rapid, membrane-delimited inhibition-mediated by direct, voltage-dependent interactions between G protein betagamma subunits and the channels-and to a slower, voltage-independent modulation involving soluble second messenger molecules. In turn, the direct inhibition of the channels is regulated as a function of many factors, including channel subtype, ancillary calcium channel subunits, and the types of G proteins and G protein regulatory factors involved. Twenty-five years after this mode of physiological regulation was first described, we review the investigations that have led to our current understanding of its molecular mechanisms.
Collapse
Affiliation(s)
- H William Tedford
- Hotchkiss Brain Institute, Department of Physiology and Biophysics, University of Calgary, Calgary, Canada
| | | |
Collapse
|
17
|
Baba T, Sakisaka T, Mochida S, Takai Y. PKA-catalyzed phosphorylation of tomosyn and its implication in Ca2+-dependent exocytosis of neurotransmitter. J Cell Biol 2005; 170:1113-25. [PMID: 16186257 PMCID: PMC2171531 DOI: 10.1083/jcb.200504055] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2005] [Accepted: 08/22/2005] [Indexed: 12/24/2022] Open
Abstract
Neurotransmitter is released from nerve terminals by Ca2+-dependent exocytosis through many steps. SNARE proteins are key components at the priming and fusion steps, and the priming step is modulated by cAMP-dependent protein kinase (PKA), which causes synaptic plasticity. We show that the SNARE regulatory protein tomosyn is directly phosphorylated by PKA, which reduces its interaction with syntaxin-1 (a component of SNAREs) and enhances the formation of the SNARE complex. Electrophysiological studies using cultured superior cervical ganglion (SCG) neurons revealed that this enhanced formation of the SNARE complex by the PKA-catalyzed phosphorylation of tomosyn increased the fusion-competent readily releasable pool of synaptic vesicles and, thereby, enhanced neurotransmitter release. This mechanism was indeed involved in the facilitation of neurotransmitter release that was induced by a potent biological mediator, the pituitary adenylate cyclase-activating polypeptide, in SCG neurons. We describe the roles and modes of action of PKA and tomosyn in Ca2+-dependent neurotransmitter release.
Collapse
Affiliation(s)
- Takeshi Baba
- Department of Molecular Biology and Biochemistry, Osaka University Graduate School of Medicine/Faculty of Medicine, Suita 565-0871, Japan
| | | | | | | |
Collapse
|
18
|
Ruiz-Velasco V, Puhl HL, Fuller BC, Sumner AD. Modulation of Ca2+ channels by opioid receptor-like 1 receptors natively expressed in rat stellate ganglion neurons innervating cardiac muscle. J Pharmacol Exp Ther 2005; 314:987-94. [PMID: 15937148 DOI: 10.1124/jpet.105.089284] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Postganglionic sympathetic nerve terminals innervate cardiac muscle and express opioid receptor-like 1 (ORL1) receptors, the most recently described member of the opioid receptor subclass. ORL1 receptors are stimulated by the endogenous heptadecapeptide nociceptin (Noc). To better understand how the signaling events by Noc regulate sympathetic neuron excitability, the goal of the present study was to determine whether sympathetic stellate ganglion (SG) neurons, innervating the heart, natively express ORL1 opioid receptors and couple to Ca(2+) channels. SG neurons in adult male rats were retrograde-labeled with a fluorescent tracer via injection of the ventricular muscle employing ultrasound imaging. Thereafter, N-type Ca(2+) channel modulation was investigated using the whole-cell variant of the patch-clamp technique. Exposure of labeled SG neurons to Noc resulted in a concentration-dependent inhibition of Ca(2+) currents (with an estimated EC(50) of 193 +/- 14 nM). Pre-exposure of SG neurons to the ORL1 receptor blocker, [Nphe(1),Arg(14),Lys(15)]N/OFQ-NH(2) (UFP-101), significantly decreased the Noc-mediated Ca(2+) current inhibition. The Ca(2+) current inhibition was also blocked by pertussis toxin pretreatment, indicating that signaling occurs via Galpha(i/o) G proteins. Finally, the full-length ORL1 receptor cDNA in SG neurons was cloned and sequenced. Of the two known alternatively spliced variants in rats, sequencing analysis showed that the ORL1 receptor expressed in SG neurons is the short form. Overall, these results suggest that stimulation of postsynaptic ORL1 receptors by Noc in SG neurons regulate cardiac sympathetic activity.
Collapse
Affiliation(s)
- Victor Ruiz-Velasco
- Department of Anesthesiology, Penn State College of Medicine, Hershey, 17033-0850, USA.
| | | | | | | |
Collapse
|
19
|
Kiss T. G-protein coupled activation of potassium channels by endogenous neuropeptides in snail neurons. Eur J Neurosci 2005; 21:2177-85. [PMID: 15869514 DOI: 10.1111/j.1460-9568.2005.04037.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Members of the mytilus inhibitory peptide (MIP) family play an important role in the modulation of many physiological processes in molluscs. The signal transduction pathways affected by the MIP effect have not, however, been elucidated. Application of guanosine 5'-[gamma-thio]triphosphate tetralithium salt (GTPgammaS), guanosine 5'-[beta-thio]diphosphate trilithium salt (GDPbetaS), the G-protein inhibitor suramin and pertussis toxin (PTX) demonstrated the involvement of the PTX-insensitive G-protein in the signal transduction pathway mediating MIP effects. Both G-protein alpha(i) and betagamma subunits were identified in D-neurons of Helix pomatia by immunoblotting. Their role in signal transduction was shown in electrophysiological experiments, which supported the notion that, in addition to the Galpha subunit, the betagamma dimer also participates in the neuropeptide-induced activation of K-channels in snail neurons. Finally, neuropeptide-activated responses were inhibited by the activation of adenylyl cyclase and by blockers of the phospholipase pathway. We suggest that bifurcation of the signal transduction takes place at the level of G-protein subunits. The alpha subunit may have a direct effect on adenylyl cyclase, while the betagamma subunit may have a direct effect on phospholipase enzymes.
Collapse
Affiliation(s)
- Tibor Kiss
- Department of Zoology, Balaton Limnological Research Institute, Hungarian Academy of Sciences, Tihany, Hungary.
| |
Collapse
|
20
|
Cunha-Reis D, Ribeiro JA, Sebastião AM. VIP enhances synaptic transmission to hippocampal CA1 pyramidal cells through activation of both VPAC1 and VPAC2 receptors. Brain Res 2005; 1049:52-60. [PMID: 15935995 DOI: 10.1016/j.brainres.2005.04.077] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Revised: 04/20/2005] [Accepted: 04/26/2005] [Indexed: 11/30/2022]
Abstract
We previously described that vasoactive intestinal peptide (VIP) increases synaptic transmission to hippocampal CA1 pyramidal cells at concentrations known to activate VIP-selective receptors (VPAC1 and VPAC2) but not the PACAP-selective PAC1 receptor. We now investigated the involvement of VPAC1 and VPAC2 receptors in the effects elicited by VIP as well as the transduction pathways activated by VIP to cause enhancement of synaptic transmission. Blockade of either VPAC1 or VPAC2 receptors with PG 97-269 (100 nM) or PG 99-465 (100 nM) inhibited VIP-induced enhancement of synaptic transmission. Selective activation of VPAC1 receptors with [K15, R16, L27] VIP(1-7)/GRF(8-27) (10 nM) or of VPAC2 receptors with RO 25-1553 (10 nM) increased synaptic transmission to CA1 pyramidal cells, and this increase was larger when both agonists were applied together. Inhibition of either PKA with H-89 (1 microM) or PKC with GF109203X (1 microM) attenuated the effect of VIP (1 nM). GF109203X (1 microM) abolished the effect of the VPAC1 agonist [K15, R16, L27] VIP(1-7)/GRF(8-27) (10 nM) on hippocampal synaptic transmission but that effect was not changed by H-89 (1 microM). The effect of RO 25-1553 (100 nM) obtained in the presence of both the PAC1 and VPAC1 antagonists, M65 (30 nM) and PG 97-269 (100 nM), was strongly inhibited by H-89 (1 microM) but not GF109203X (1 microM). It is concluded that VIP enhances synaptic transmission to CA1 pyramidal cell dendrites through VPAC1 and VPAC2 receptor activation. VPAC1-mediated actions are dependent on PKC activity, and VPAC2-mediated actions are responsible for the PKA-dependent actions of VIP on CA1 hippocampal transmission.
Collapse
Affiliation(s)
- Diana Cunha-Reis
- Institute of Pharmacology and Neurosciences, Faculty of Medicine, University of Lisbon, Av. Prof. Egas Moniz, 1649-028 Lisbon, Portugal.
| | | | | |
Collapse
|
21
|
Chen H, Ikeda SR. Modulation of ion channels and synaptic transmission by a human sensory neuron-specific G-protein-coupled receptor, SNSR4/mrgX1, heterologously expressed in cultured rat neurons. J Neurosci 2005; 24:5044-53. [PMID: 15163697 PMCID: PMC6729361 DOI: 10.1523/jneurosci.0990-04.2004] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Human sensory neuron-specific G-protein-coupled receptors (SNSRs) are expressed solely in small diameter primary sensory neurons. This restricted expression pattern is of considerable therapeutic interest because small nociceptors transmit chronic pain messages. The neuronal function of human SNSRs is difficult to assess because rodent orthologs have yet to be clearly defined, and individual isoforms are found only in a small subset of primary sensory neurons. To circumvent this problem, we expressed human SNSR4 (hSNSR4; also known as Hs.mrgX1) in rat superior cervical ganglion (SCG), dorsal root ganglion (DRG), and hippocampal neurons using nuclear injection or recombinant adenoviruses and examined modulation of ion channels and neurotransmission using whole-cell patch-clamp techniques. BAM8-22 (a 15 amino acid C-terminal fragment of bovine adrenal medulla peptide 22), a peptide agonist derived from proenkephalin, inhibited high (but not low) voltage-activated Ca2+ current in both DRG and SCG neurons expressing hSNSR4, whereas no response was detected in control neurons. The Ca2+ current inhibition was concentration dependent and partially sensitive to Pertussis toxin (PTX) treatment. Additionally, the peptide was highly effective in modulating current arising from M-type K+ channels in SCG neurons expressing hSNSR4. In hippocampal neurons expressing hSNSR4, BAM8-22 induced presynaptic inhibition of transmission that was abolished after PTX treatment. Our data indicate that hSNSR4, when heterologously expressed in rat neurons, can be activated by an opioid-related peptide, couples to G(q/11)-proteins as well as PTX-sensitive G(i/o)-proteins, and modulates neuronal Ca2+ channels, K+ channels, and synaptic transmission.
Collapse
Affiliation(s)
- Huanmian Chen
- Laboratory of Molecular Physiology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland 20892-8115, USA
| | | |
Collapse
|
22
|
Endoh T. Modulation of voltage-dependent calcium channels by neurotransmitters and neuropeptides in parasympathetic submandibular ganglion neurons. Arch Oral Biol 2004; 49:539-57. [PMID: 15126136 DOI: 10.1016/j.archoralbio.2004.02.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/03/2004] [Indexed: 12/20/2022]
Abstract
The control of saliva secretion is mainly under parasympathetic control, although there also could be a sympathetic component. Sympathetic nerves are held to have a limited action in secretion in submandibular glands because, on electrical stimulation, only a very small increase to the normal background, basal secretion occurs. Parasympathetic stimulation, on the other hand, caused a good flow of saliva with moderate secretion of acinar mucin, plus an extensive secretion of granules from the granular tubules. The submandibular ganglion (SMG) is a parasympathetic ganglion which receives inputs from preganglionic cholinergic neurons, and innervates the submandibular salivary gland to control saliva secretion. Neurotransmitters and neuropeptides acting via G-protein coupled receptors (GPCRs) change the electrical excitability of neurons. In these neurons, many neurotransmitters and neuropeptides modulate voltage-dependent calcium channels (VDCCs). The modulation is mediated by a family of GPCRs acting either directly through the membrane delimited G-proteins or through second messengers. However, the mechanism of modulation and the signal transduction pathway linked to an individual GPCRs depend on the animal species. This review reports how neurotransmitters and neuropeptides modulate VDCCs and how these modulatory actions are integrated in SMG systems. The action of neurotransmitters and neuropeptides on VDCCs may provide a mechanism for regulating SMG excitability and also provide a cellular mechanism of a variety of neuronal Ca(2+)-dependent processes.
Collapse
Affiliation(s)
- Takayuki Endoh
- Department of Physiology, Tokyo Dental College, 1-2-2 Masago, Mihama-ku, Chiba 261-8502, Japan.
| |
Collapse
|
23
|
Kammermeier PJ, Yun J. Activation of metabotropic glutamate receptor 1 dimers requires glutamate binding in both subunits. J Pharmacol Exp Ther 2004; 312:502-8. [PMID: 15466247 DOI: 10.1124/jpet.104.073155] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Group I metabotropic glutamate receptors (mGluRs) form stable, disulfide-linked homodimers. Lack of a verifiably monomeric mGluR1 mutant has led to difficulty in assessing the role of dimerization in the molecular mechanism of mGluR1 activation. The related GABA(B) receptor exhibits striking intradimer cross talk (ligand binding at one subunit effectively produces G protein activation at the other), but it is unclear whether group I mGluRs exhibit analogous cross talk. Signaling of heterologously expressed mGluR1 was examined in isolated rat sympathetic neurons by measuring glutamate-mediated inhibition of native calcium currents. To examine mGluR1 activity when only one dimer subunit has access to glutamate ligand, wildtype mGluR1 was coexpressed with mGluR1 Y74A, a mutant with impaired glutamate binding, and the activity of the heterodimer (mutant/wild type) was examined. The mGluR1 Y74A mutant alone had a dose-response curve that was shifted by about 2 orders of magnitude. The half-maximal dose of glutamate shifted from 1.3 (wild-type mGluR1) to about 450 (mGluR1 Y74A) microM. However, the maximal effect was similar. Wild-type mGluR1 was expressed with excess Y74A mGluR1 to generate a receptor population consisting largely of mutant homodimers and mutant/wild-type heterodimers but without detectable wild-type homodimers. Under these conditions, no glutamate-mediated calcium current inhibition was observed below approximately 300 microM glutamate, although wild-type mGluR1 protein was detectable with immunofluorescence. These data suggest that mutant/wild-type heterodimeric receptors are inactive at ligand concentrations favoring glutamate association with receptor dimers at only one subunit.
Collapse
Affiliation(s)
- Paul J Kammermeier
- Department of Physiology and Pharmacology, Northeastern Ohio Universities College of Medicine, 4209 State Route 44, P.O. Box 95, Rootstown, OH 44272, USA.
| | | |
Collapse
|
24
|
Abstract
There are many different calcium channels expressed in the mammalian nervous system, but N-type and P/Q-type calcium channels appear to dominate the presynaptic terminals of central and peripheral neurons. The neurotransmitter-induced modulation of these channels can result in alteration of synaptic transmission. This review highlights the mechanisms by which neurotransmitters affect the activity of N-type and P/Q-type calcium channels. The inhibition of these channels by voltage-dependent and voltage-independent mechanisms is emphasized because of the wealth of information available on the intracellular mediators and on the effect of these pathways on the single-channel gating.
Collapse
Affiliation(s)
- Keith S Elmslie
- Department of Physiology, Tulane University Health Science Center, New Orleans, Louisiana 70112, USA.
| |
Collapse
|
25
|
Kamaishi H, Endoh T, Suzuki T. Multiple signal pathways coupling VIP and PACAP receptors to calcium channels in hamster submandibular ganglion neurons. Auton Neurosci 2004; 111:15-26. [PMID: 15109935 DOI: 10.1016/j.autneu.2004.01.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2003] [Revised: 01/07/2004] [Accepted: 01/08/2004] [Indexed: 11/29/2022]
Abstract
The Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are two novel neuropeptides which produce particular biological effects caused by interaction with G-protein-coupled receptors. We have shown in a previous study where VIP and PACAP 38 inhibit voltage-dependent calcium channel (VDCC) currents (ICa) via G-proteins in hamster submandibular ganglion (SMG) neurons. In this study, we attempt to further characterize the signal transduction pathways of VIP-and PACAP 38-induced modulation of ICa. Application of 1 microM VIP and PACAP 38 inhibited ICa by 33.0 +/- 3.1% and 36.8 +/- 2.6%, respectively (mean +/- S.E.M., n = 8). Application of strong voltage prepulse attenuated PACAP 38-induced inhibition of ICa. Pretreatment of cAMP dependent protein kinase (PKA) activator attenuated VIP-induced inhibition, but not the PACAP 38-induced inhibition. Intracellular dialysis of the PKA inhibitor attenuated the VIP-induced inhibition, but not the PACAP 38-induced inhibition. Pretreatment of protein kinase C (PKC) activator and inhibitor attenuated VIP-induced inhibition, but not the PACAP 38-induced inhibition. Pretreatment of cholera toxin (CTX) attenuated PACAP 38-induced inhibition of ICa. These findings indicate that there are multiple signaling pathways in VIP and PACAP 38-induced inhibitions of ICa: one pathway would be the VPAC1/VPAC2 receptors-induced inhibition involving both the PKA and PKC, and another one concerns the PAC1 receptor-induced inhibition via Gs-protein betagamma subunits. The VIP-and PACAP 38-induced facilitation of ICa can be observed in the SMG neurons in addition to inhibiting of ICa.
Collapse
Affiliation(s)
- Hideaki Kamaishi
- Department of Physiology, Tokyo Dental College, 1-2-2, Masago, Mihama, Chiba 261-8502, Japan
| | | | | |
Collapse
|
26
|
Narahashi T, Marszalec W, Moriguchi S, Yeh JZ, Zhao X. Unique mechanism of action of Alzheimer's drugs on brain nicotinic acetylcholine receptors and NMDA receptors. Life Sci 2004; 74:281-91. [PMID: 14607256 DOI: 10.1016/j.lfs.2003.09.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
While a variety of hypotheses have been proposed for the cause of Alzheimer's disease, our knowledge is far from complete to explain the disease making it difficult to develop the methods for treatment. In the brain of Alzheimer's patients, both neuronal nicotinic acetylcholine (nACh) receptors and NMDA receptors are known to be down-regulated. Thus four anticholinesterases have been developed and approved for the treatment in the U.S.A. However, these are not ideal drugs considering their side effects and limited effectiveness. Nefiracetam is being developed for the treatment of Alzheimer's and other patients with dementia, and has unique actions in potentiating the activity of both nACh and NMDA receptors as demonstrated by in vitro patch clamp experiments using rat cortical neurons in primary culture. Nefiracetam potentiated alpha4beta2-like ACh- and NMDA-induced currents at nanomolar concentrations forming bell-shaped dose-response curves with the maximum potentiation occurring at 1 and 10 nM, respectively. Nefiracetam potentiated nACh receptor currents via G(s) proteins, but not G(i)/G(o) proteins, PKA or PKC. Nefiracetam potentiation of NMDA currents occurred via interactions with the glycine binding site of the NMDA receptor. The nefiracetam potentiation of both nACh and NMDA receptors in a potent and efficacious manner is deemed responsible for its cognitive enhancing action.
Collapse
Affiliation(s)
- Toshio Narahashi
- Department of Molecular Pharmacology Biological Chemistry, Northwestern University Medical School, 303 E. Chicago Avenue, Chicago, IL 60611, USA.
| | | | | | | | | |
Collapse
|
27
|
Narahashi T, Moriguchi S, Zhao X, Marszalec W, Yeh JZ. Mechanisms of Action of Cognitive Enhancers on Neuroreceptors. Biol Pharm Bull 2004; 27:1701-6. [PMID: 15516710 DOI: 10.1248/bpb.27.1701] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
No strategies for curing Alzheimer's disease have been developed yet as we do not know the exact cause of the disease. The only therapy that is available for patients is symptomatic treatment. Since Alzheimer's disease is associated with downregulation of the cholinergic system in the brain, its stimulation is expected to improve the patients' cognition, learning, and memory. Four anticholinesterases have been approved in the U.S.A. for the treatment of Alzheimer's disease patients. However, because of the inhibition of cholinesterases, these drugs have side effects and their effectiveness does not last long. Thus new approaches are needed. One approach is to stimulate directly nicotinic acetylcholine (nACh) receptors in the brain, and another is to stimulate NMDA receptors which are also known to be downregulated in Alzheimer's patients. Nefiracetam has been shown to potentiate ACh currents in the alpha4beta2 receptor of rat cortical neurons with a bell-shaped dose-response relationship and the maximum effect at 1 nM. This effect was exerted via G(s) proteins. The alpha7 receptor was almost unaffected by nefiracetam. Nefiracetam also potentiated NMDA currents with the maximum effect at 10 nM via interaction with the glycine-binding site of the receptor. Galantamine had a moderate potentiating effect on the alpha4beta2 receptor and potentiated NMDA currents with the maximum effect at 1 microM. However, galantamine did not interact with the glycine-binding site. Donepezil, a potent anticholinesterase, also potentiated NMDA currents at 1-10000 nM. In conclusion, these three drugs potentiate the activity not only of the cholinergic system but also of the NMDA system, thereby stimulating the downregulated nACh receptors and NMDA receptors to improve patients' learning, cognition, and memory.
Collapse
Affiliation(s)
- Toshio Narahashi
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, Chicago, IL 60611, USA.
| | | | | | | | | |
Collapse
|
28
|
Abstract
Calcium influx into any cell requires fine tuning to guarantee the correct balance between activation of calcium-dependent processes, such as muscle contraction and neurotransmitter release, and calcium-induced cell damage. G protein-coupled receptors play a critical role in negative feedback to modulate the activity of the CaV2 subfamily of the voltage-dependent calcium channels, which are largely situated on neuronal and neuro-endocrine cells. The basis for the specificity of the relationships among membrane receptors, G proteins, and effector calcium channels will be discussed, as well as the mechanism by which G protein-mediated inhibition is thought to occur. The inhibition requires free G beta gamma dimers, and the cytoplasmic linker between domains I and II of the CaV2 alpha 1 subunits binds G beta gamma dimers, whereas the intracellular N terminus of CaV2 alpha 1 subunits provides essential determinants for G protein modulation. Evidence suggests a key role for the beta subunits of calcium channels in the process of G protein modulation, and the role of a class of proteins termed "regulators of G protein signaling" will also be described.
Collapse
Affiliation(s)
- Annette C Dolphin
- Department of Pharmacology, University College London, Gower St., London WC1E 6BT, UK.
| |
Collapse
|
29
|
Vásquez C, Lewis DL. The beta2-adrenergic receptor specifically sequesters Gs but signals through both Gs and Gi/o in rat sympathetic neurons. Neuroscience 2003; 118:603-10. [PMID: 12710970 DOI: 10.1016/s0306-4522(03)00024-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Beta(2)-adrenergic receptors (beta(2)-AR) and CB1 cannabinoid receptors share the property of being constitutively active. The CB1 cannabinoid receptor can also sequester G(i/o) proteins; however, it is not known whether the beta(2)-AR can also sequester G proteins. Beta(2)-ARs were heterologously expressed in rat superior cervical ganglion neurons by microinjection of cDNA and studied using the patch-clamp technique. The beta-AR agonist isoproterenol increased the Ca(2+) current 25.9+/-1.6% in neurons microinjected with 100 ng/microl beta(2)-AR cDNA but was without effect on control neurons. Pretreatment with cholera toxin (CTX) abolished the effect of isoproterenol, indicating coupling via G(s) proteins. In neurons microinjected with 200 ng/microl beta(2)-AR cDNA, isoproterenol had the opposite effect of inhibiting the Ca(2+) current 36.5+/-2.0%. Inhibition of the Ca(2+) current was sensitive to pertussis toxin, indicating beta(2)-AR coupling to G(i/o) proteins. Pretreatment with CTX resulted in a greater 54+/-3.8% inhibition of the Ca(2+) current, indicating that G(s) coupling masks the full effect of G(i/o) coupling. Expression of beta(2)-ARs abolished signaling by G(s)-coupled receptors for vasoactive intestinal polypeptide (VIP). VIP inhibited the Ca(2+) current 49.5+/-0.5% in control neurons but had no effect in neurons expressing beta(2)-ARs. In contrast, expression of beta(2)-ARs had no effect on signaling by the G(i/o)-coupled alpha(2)-adrenergic receptor. This study demonstrates that the beta(2)-AR couples to both G(s) and G(i/o) proteins but specifically sequesters G(s) proteins, preventing their interaction with another G(s)-coupled receptor. beta(2)-adrenergic receptors thus have the potential to prevent other G(s)-coupled receptors from transducing their biological signals.
Collapse
MESH Headings
- Adrenergic beta-Agonists/pharmacology
- Animals
- Calcium Signaling/drug effects
- Calcium Signaling/physiology
- Cells, Cultured
- Cholera Toxin/pharmacology
- DNA, Complementary
- GTP-Binding Protein alpha Subunits, Gi-Go/drug effects
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- GTP-Binding Protein alpha Subunits, Gs/drug effects
- GTP-Binding Protein alpha Subunits, Gs/metabolism
- Heterotrimeric GTP-Binding Proteins/drug effects
- Heterotrimeric GTP-Binding Proteins/metabolism
- Male
- Neurons/drug effects
- Neurons/metabolism
- Rats
- Rats, Wistar
- Receptors, Adrenergic, beta-2/drug effects
- Receptors, Adrenergic, beta-2/genetics
- Receptors, Adrenergic, beta-2/metabolism
- Receptors, Cannabinoid
- Receptors, Drug/drug effects
- Receptors, Drug/metabolism
- Signal Transduction/drug effects
- Signal Transduction/genetics
- Superior Cervical Ganglion/cytology
- Superior Cervical Ganglion/drug effects
- Superior Cervical Ganglion/metabolism
- Vasoactive Intestinal Peptide/pharmacology
Collapse
Affiliation(s)
- C Vásquez
- Department of Pharmacology and Toxicology, Medical College of Georgia, 1120 15th Street, Augusta, GA 30912-2300, USA
| | | |
Collapse
|
30
|
Guo J, Schofield GG. Activation of muscarinic m5 receptors inhibits recombinant KCNQ2/KCNQ3 K+ channels expressed in HEK293T cells. Eur J Pharmacol 2003; 462:25-32. [PMID: 12591092 DOI: 10.1016/s0014-2999(03)01323-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A variety of G-protein-coupled receptors regulate membrane excitability via M-type K(+) current (M-current) modulation. Muscarinic m1 and m3 acetylcholine receptors have both been implicated in the modulation of M-current. The muscarinic m5 receptor, like muscarinic m1 and m3 receptors, couples to phospholipase C via a pertussis toxin-insensitive G protein. Since a number of other receptors which activate phospholipase C also modulate M-current, we investigated if muscarinic m5 receptors could modulate recombinant M-type (KCNQ2/KCNQ3) K(+) channels after heterologous expression in human embryonic kidney (HEK) 293T cells. Application of Oxo-tremorine M to HEK293T cells expressing muscarinic m1, m3, or m5 receptors produced a similar robust inhibition of M-current, whereas muscarinic m2 and m4 receptor stimulation was without effect. Muscarinic m1, m3, or m5 receptor stimulation decreased the deactivation time constants of M-current at -50 mV. The inhibition of M-current by stimulation of muscarinic m1, m3, or m5 receptors was insensitive to overnight treatment with pertussis toxin or cholera toxin, which interfere with G(i/o) and G(s) G-protein signaling. These data suggest that muscarinic m1, m3, and m5 receptors inhibit M-channels via the activation of a common G protein.
Collapse
Affiliation(s)
- Juan Guo
- Department of Physiology SL-39, Tulane University Health Sciences Center, 1430 Tulane Avenue, New Orleans, LA 70112, USA
| | | |
Collapse
|
31
|
Suzuki T, Ono H, Ikegami H. PACAP-induced depolarizations in hamster submandibular ganglion neurons. THE BULLETIN OF TOKYO DENTAL COLLEGE 2003; 44:21-4. [PMID: 12772583 DOI: 10.2209/tdcpublication.44.21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In this study, we have investigated the effects of pituitary adenylate cyclase-activating polypeptide (PACAP) on in vitro hamster submandibular ganglion neurons using the conventional intracellular recording technique. PACAP (10 microM) induced slow depolarizations in approximately 70% of tested cells. PACAP-induced depolarizations were approximately 10 mV in the peak amplitude, and their durations were approximately 10 min. The slow depolarizations were accompanied by a decrease in membrane conductance (gm) at the initial phase and an increase in gm at the peak phase. Membrane input resistance increased by 14.8 +/- 2.2% (mean +/- S.E., max.) of the resting value at the initial phase and decreased by 30.8 +/- 4.3% (max.) at the peak phase. Anodal break spikes were elicited at the initial phase during PACAP-induced depolarization. In one neuron, anodal break spikes were elicited at the peak. Spikes which followed the anodal break spike were also elicited at 4 Hz in the initial phase during the slow depolarizations. The decrease in gm was probably produced by an inhibition of calcium conductance and an inhibition of slow Ca(2+)-activated K+ channels, while the increase in gm might have been produced by an activation of nonselective cation channels. The slow depolarizations by PACAP might be mediated by a membrane-delimited signal transduction cascade involving G protein in the submandibular ganglion neurons.
Collapse
Affiliation(s)
- Takashi Suzuki
- Department of Physiology, Tokyo Dental College, 1-2-2 Masago, Mihama-ku, Chiba 261-8502, Japan
| | | | | |
Collapse
|
32
|
Borgland SL, Connor M, Ryan RM, Ball HJ, Christie MJ. Prostaglandin E(2) inhibits calcium current in two sub-populations of acutely isolated mouse trigeminal sensory neurons. J Physiol 2002; 539:433-44. [PMID: 11882676 PMCID: PMC2290145 DOI: 10.1113/jphysiol.2001.013322] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Prostaglandins are important mediators of pain and inflammation. We have examined the effects of prostanoids on voltage-activated calcium currents (I(Ca)) in acutely isolated mouse trigeminal sensory neurons, using standard whole cell voltage clamp techniques. Trigeminal neurons were divided into two populations based on the presence (Type 2) or absence (Type 1) of low voltage-activated T-type I(Ca). The absence of T-type I(Ca) is highly correlated with sensitivity to mu-opioid agonists and the VR1 agonist capsaicin. In both populations of cells, high voltage-activated I(Ca) was inhibited by PGE(2) with an EC(50) of about 35 nM, to a maximum of 30 %. T-type I(Ca) was not inhibited by PGE(2). Pertussis toxin pre-treatment abolished the effects of PGE(2) in Type 2 cells, but not in Type 1 cells, whereas treatment with cholera toxin prevented the effects of PGE(2) in Type 1 cells, but not in Type 2 cells. Inhibition of I(Ca) by PGE(2) was associated with slowing of current activation and could be relieved with a large positive pre-pulse, consistent with inhibition of I(Ca) by G protein betagamma subunits. Reverse transcription-polymerase chain reaction of mRNA from trigeminal ganglia indicated that all four EP prostanoid receptors were present. However, in both Type 1 and Type 2 cells the effects of PGE(2) were only mimicked by the selective EP(3) receptor agonist ONO-AE-248, and not by selective agonists for EP(1) (ONO-DI-004), EP(2) (ONO-AE1-259) and EP(4) (ONO-AE1-329) receptors. These data indicate that two populations of neurons in trigeminal ganglia differing in their calcium channel expression, sensitivity to mu-opioids and capsaicin also have divergent mechanisms of PGE(2)-mediated inhibition of calcium channels, with Gi/Go type G proteins involved in one population, and Gs type G proteins in the other.
Collapse
MESH Headings
- Animals
- Calcium Channel Blockers/pharmacology
- Calcium Channels/drug effects
- Calcium Channels/metabolism
- Calcium Channels, N-Type/drug effects
- Calcium Channels, N-Type/metabolism
- Calcium Channels, Q-Type/drug effects
- Calcium Channels, Q-Type/metabolism
- Cholera Toxin/pharmacology
- Dinoprostone/pharmacology
- Electrophysiology
- Female
- GTP-Binding Protein alpha Subunits, Gi-Go/drug effects
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- GTP-Binding Protein alpha Subunits, Gs/drug effects
- GTP-Binding Protein alpha Subunits, Gs/metabolism
- GTP-Binding Proteins/drug effects
- GTP-Binding Proteins/metabolism
- In Vitro Techniques
- Ion Channel Gating
- Male
- Mice
- Mice, Inbred C57BL
- Neurons, Afferent/drug effects
- Patch-Clamp Techniques
- Pertussis Toxin
- RNA/genetics
- RNA/isolation & purification
- Reverse Transcriptase Polymerase Chain Reaction
- Trigeminal Nerve/drug effects
- Trigeminal Nerve/metabolism
- Virulence Factors, Bordetella/pharmacology
Collapse
|
33
|
Hayashi K, Endoh T, Shibukawa Y, Yamamoto T, Suzuki T. VIP and PACAP inhibit L-, N- and P/Q-type Ca2+ channels of parasympathetic neurons in a voltage independent manner. THE BULLETIN OF TOKYO DENTAL COLLEGE 2002; 43:31-9. [PMID: 12013823 DOI: 10.2209/tdcpublication.43.31] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In this study, we investigated the effects of vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide 1-38 (PACAP) on the voltage-gated calcium currents in hamster submandibular ganglion neurons. VIP and PACAP inhibited the high threshold voltage-gated calcium current in a voltage-independent and a concentration-dependent manner via the G protein-mediated pathway. L-, N- and P/Q-type components of the total maximum voltage-gated calcium current accounted for 48.0 +/- 3.1% (n = 4), 35.1 +/- 4.7% (n = 4), and 13.5 +/- 2.3% (n = 3) of the total peak amplitude, respectively. VIP at a concentration of 1 microM inhibited the L-type calcium current by 33.2% +/- 1.4% (n = 4), the N-type current by 31.0 +/- 3.6%, and the P/Q-type current by 3.2 +/- 1.1% (n = 3). PACAP at a concentration of 1 microM inhibited the L-type current by 35.6 +/- 5.7%, the N-type current by 34.4 +/- 3.1% (n = 4), and the P/Q-type current by 6.4 +/- 2.1% (n = 2). However, VIP and PACAP did not inhibit the low threshold voltage-gated (T-type) calcium current. The rank order of potency was PACAP > VIP. In experiments replacing GTP with GDP-beta-S, the inhibitory effects of VIP and PACAP were prevented. In experiments of double-pulse protocol, depolarizing conditioning pulses could not relieve the inhibition of total high threshold voltage-gated calcium currents produced by VIP and PACAP. Therefore, the inhibition of the high threshold voltage-gated calcium channels produced by VIP and PACAP in hamster parasympathetic neurons differed in its mechanisms from that of N-type calcium channels in rat sympathetic neurons.
Collapse
Affiliation(s)
- Kentarou Hayashi
- Department of Physiology, Tokyo Dental College, 1-2-2 Masago, Mihama-ku, Chiba 261-8502, Japan
| | | | | | | | | |
Collapse
|
34
|
Kolaj M, Renaud LP. Norepinephrine acts via alpha(2) adrenergic receptors to suppress N-type calcium channels in dissociated rat median preoptic nucleus neurons. Neuropharmacology 2001; 41:472-9. [PMID: 11543767 DOI: 10.1016/s0028-3908(01)00090-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The median preoptic (MnPO) nucleus, a key CNS site for hydromineral and cardiovascular homeostasis, receives a dense norepinephrine innervation from brainstem autonomic centers. Since norepinephrine is known to influence neuronal excitability by modulating calcium channel function, we applied whole cell patch clamp techniques to study calcium currents in 116 dissociated MnPO neurons, including 30 cells identified by a retrograde label as projecting to the hypothalamic paraventricular nucleus. Norepinephrine (3-50 microM) suppressed high-voltage-activated calcium currents (HVA I(Ca)) in 80% of cells, selectively blockable by yohimbine and mimicked by UK14,304 and clonidine. The norepinephrine effect was relieved by strong prior depolarization, indicating a voltage-dependent component. Intracellular GTP-gamma-S blocked the effect. Blockade by extracellular NEM suggested involvement of pertussis-toxin sensitive G-proteins. Based on pharmacological properties, these HVA I(Ca)s had the following composition: 40-45% N-type (blockable by omega-conotoxin GVIA); 20-25% L-type (blockable by nimodipine); 15-20% P/Q-type (blockable by omega-agatoxin IVA). Since approximately 75% of the norepinephrine effect was blockable with omega-conotoxin GVIA, we conclude that postsynaptic alpha(2) adrenoceptors preferentially suppress N-type calcium channels, revealing a novel mechanism whereby norepinephrine can modulate excitability in MnPO neurons.
Collapse
Affiliation(s)
- M Kolaj
- Neurology and Neurosciences, Loeb Health Research Institute, Ottawa Hospital--Civic Site and University of Ottawa, 1053 Carling Avenue, Ottawa, Ontario, Canada K1Y 4E9
| | | |
Collapse
|
35
|
Abstract
The inhibition of presynaptic calcium channels via G-protein-dependent second messenger pathways is a key mechanism of transmitter release modulation. We used the calyx-type nerve terminal of the chick ciliary ganglion to examine which G-proteins are involved in the voltage-sensitive inhibition of presynaptic N-type calcium channels. Adenosine caused a prominent inhibition of the calcium current that was totally blocked by pretreatment with pertussis toxin (PTX), consistent with an exclusive involvement of G(o)/G(i) in the G-protein pathway. Immunocytochemistry was used to localize these G-protein types to the nerve terminal and its transmitter release face. We used two approaches to test for modulation by other G-protein types. First, we treated the terminals with ligands for a variety of G-protein-linked neurotransmitter receptor types that have been associated with different G-protein families. Although small inhibitory effects were observed, these could all be eliminated by PTX, indicating that in this terminal the G(i) family is the sole transmitter-induced G-protein inhibitory pathway. Second, we examined the kinetics of calcium channel inhibition by uncaging the nonselective and irreversible G-protein activator GTPgammaS, bypassing the receptors. A large fraction of the rapid GTPgammaS-induced inhibition persisted, consistent with a G(o)/G(i)-independent pathway. Immunocytochemistry identified G(q), G(11), G(12), and G(13) as potential PTX-insensitive second messengers at this terminal. Thus, our results suggest that whereas neurotransmitter-mediated calcium channel inhibition is mainly, and possibly exclusively, via G(o)/G(i), other rapid PTX-insensitive G-protein pathways exist that may involve novel, and perhaps transmitter-independent, activating mechanisms.
Collapse
|
36
|
Zhao X, Kuryatov A, Lindstrom JM, Yeh JZ, Narahashi T. Nootropic drug modulation of neuronal nicotinic acetylcholine receptors in rat cortical neurons. Mol Pharmacol 2001; 59:674-83. [PMID: 11259610 DOI: 10.1124/mol.59.4.674] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nefiracetam (DM-9384) is a new pyrrolidone nootropic drug being developed for the treatment of Alzheimer's type and poststroke vascular-type dementia. Because the cholinergic system plays an important role in cognitive functions and Alzheimer's disease dementia, the present study was conducted to elucidate the mechanism of action of nefiracetam and aniracetam on neuronal nicotinic acetylcholine receptors (nnAChRs). Currents were recorded from rat cortical neurons in long-term primary culture using the whole-cell, patch-clamp technique. Two types of currents were evoked by acetylcholine (ACh): alpha-bungarotoxin-sensitive, alpha 7-type currents and alpha-bungarotoxin-insensitive, alpha 4 beta 2-type currents. Although nefiracetam and aniracetam inhibited alpha 7-type currents only weakly, these nootropic agents potentiated alpha 4 beta 2-type currents in a very potent and efficacious manner. Nefiracetam at 1 nM and aniracetam at 0.1 nM reversibly potentiated alpha 4 beta 2-type currents to 200 to 300% of control. Nefiracetam at very high concentrations (approximately 10 microM) also potentiated alpha 4 beta 2-type currents but to a lesser extent, indicative of a bell-shaped dose-response relationship. Nefiracetam markedly increased the saturating responses induced by high concentrations of ACh. However, human alpha 4 beta 2 subunits expressed in human embryonic kidney cells were inhibited rather than potentiated by nefiracetam. The specific protein kinase A inhibitors (H-89, KT5720, and peptide 5-24) and protein kinase C inhibitors (chelerythrine, calphostin C, and peptide 19--63) did not prevent nefiracetam from potentiating alpha 4 beta 2-type currents, indicating that these protein kinases are not involved in nefiracetam action. The nefiracetam potentiating action was not affected by 24-h pretreatment of neurons with pertussis toxin, but was abolished by cholera toxin. Therefore, G(s) proteins, but not G(i)/G(o) proteins, are involved in nefiracetam potentiation. These results indicate that nnAChRs are an important site of action of nefiracetam and G(s) proteins may be its crucial target.
Collapse
Affiliation(s)
- X Zhao
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, Chicago, Illinois 60611, USA
| | | | | | | | | |
Collapse
|
37
|
Liu DM, Cuevas J, Adams DJ. VIP and PACAP potentiation of nicotinic ACh-evoked currents in rat parasympathetic neurons is mediated by G-protein activation. Eur J Neurosci 2000; 12:2243-51. [PMID: 10947803 DOI: 10.1046/j.1460-9568.2000.00116.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The effects of vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP27 and PACAP38) on isolated parasympathetic neurons of rat intracardiac and submandibular ganglia were examined under voltage clamp using whole-cell patch-clamp recording techniques. VIP and PACAP (</= 10 nM) selectively and reversibly increased the affinity of nicotinic acetylcholine receptor channels (nAChRs) for their agonists resulting in a potentiation of acetylcholine (ACh)-evoked whole-cell currents at low agonist concentrations. VIP-induced potentiation was observed with either ACh or nicotine as the cholinergic agonist. The VIP- but not the PACAP-induced potentiation of ACh-evoked currents was inhibited by [Ac-Tyr1, D-Phe2]-GRF 1-29, amide (100 nM), a selective antagonist of VPAC1 and VPAC2 receptors; whereas the PACAP38- but not the VIP-induced potentiation was inhibited by 100 nM PACAP6-38, a PAC1 and VPAC2 receptor antagonist. The signal transduction pathway mediating VIP- and PACAP-induced potentiation of nicotinic ACh-evoked currents involves a pertussis toxin (PTX)-sensitive G-protein. Intracellular application of 200 microM GTPgammaS or GDPbetaS inhibited VIP-induced potentiation of ACh-evoked whole-cell currents. GTPgammaS alone potentiated ACh- and nicotine-evoked currents and the magnitude of these currents was not further increased by VIP or PACAP. The G-protein subtype modulating the neuronal nAChRs was examined by intracellular dialysis with antibodies directed against alphao, alphai-1,2, alphai-3 or beta G-protein subunits. Only the anti-Galphao and anti-Gbeta antibodies significantly inhibited the effect of VIP and PACAP on ACh-evoked currents. The potentiation of ACh-evoked currents by VIP and PACAP may be mediated by a membrane-delimited signal transduction cascade involving the PTX-sensitive Go protein.
Collapse
Affiliation(s)
- D M Liu
- Department of Physiology and Pharmacology, University of Queensland, Brisbane, Australia
| | | | | |
Collapse
|
38
|
Haug T, Storm JF. Protein kinase A mediates the modulation of the slow Ca(2+)-dependent K(+) current, I(sAHP), by the neuropeptides CRF, VIP, and CGRP in hippocampal pyramidal neurons. J Neurophysiol 2000; 83:2071-9. [PMID: 10758117 DOI: 10.1152/jn.2000.83.4.2071] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have studied modulation of the slow Ca(2+)-activated K(+) current (I(sAHP)) in CA1 hippocampal pyramidal neurons by three peptide transmitters: corticotropin releasing factor (CRF, also called corticotropin releasing hormone, CRH), vasoactive intestinal peptide (VIP), and calcitonin gene-related peptide (CGRP). These peptides are known to be expressed in interneurons. Using whole cell voltage clamp in hippocampal slices from young rats, in the presence of tetrodotoxin (TTX, 0.5 microM) and tetraethylammonium (TEA, 5 mM), I(sAHP) was measured after a brief depolarizing voltage step eliciting inward Ca(2+) current. Each of the peptides CRF (100-250 nM), VIP (400 nM), and CGRP (1 microM) significantly reduced the amplitude of I(sAHP). Thus the I(sAHP) amplitude was reduced to 22% by 100 nM CRF, to 17% by 250 nM CRF, to 22% by 400 nM VIP, and to 40% by 1 microM CGRP. We found no consistent concomitant changes in the Ca(2+) current or in the time course of I(sAHP) for any of the three peptides, suggesting that the suppression of I(sAHP) was not secondary to a general suppression of Ca(2+) channel activity. Because each of these peptides is known to activate the cyclic AMP (cAMP) cascade in various cell types, and I(sAHP) is known to be suppressed by cAMP via the cAMP-dependent protein kinase (PKA), we tested whether the effects on I(sAHP) by CRF, VIP, and CGRP are mediated by PKA. Intracellular application of the PKA-inhibitor Rp-cAMPS significantly reduced the suppression of I(sAHP) by CRF, VIP, and CGRP. Thus with 1 mM Rp-cAMPS in the recording pipette, the average suppression of I(sAHP) was reduced from 78 to 26% for 100 nM CRF, from 83 to 32% for 250 nM CRF, from 78 to 30% for 400 nM VIP, and from 60 to 7% for 1 microM CGRP. We conclude that CRF, VIP, and CGRP suppress the slow Ca(2+)-activated K(+) current, I(sAHP), in CA1 hippocampal pyramidal neurons by activating the cAMP-dependent protein kinase, PKA. Together with the monoamine transmitters norepinephrine, serotonin, histamine, and dopamine, these peptide transmitters all converge on the cAMP cascade modulating I(sAHP).
Collapse
Affiliation(s)
- T Haug
- Institute of Physiology and Neurophysiology, University of Oslo, N-0317 Oslo, Norway
| | | |
Collapse
|
39
|
Currie KP, Fox AP. Voltage-dependent, pertussis toxin insensitive inhibition of calcium currents by histamine in bovine adrenal chromaffin cells. J Neurophysiol 2000; 83:1435-42. [PMID: 10712470 DOI: 10.1152/jn.2000.83.3.1435] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Histamine is a known secretagogue in adrenal chromaffin cells. Activation of G-protein linked H(1) receptors stimulates phospholipase C, which generates inositol trisphosphate leading to release of intracellular calcium stores and stimulation of calcium influx through store operated and other channels. This calcium leads to the release of catecholamines. In chromaffin cells, the main physiological trigger for catecholamine release is calcium influx through voltage-gated calcium channels (I(Ca)). Therefore, these channels are important targets for the regulation of secretion. In particular N- and P/Q-type I(Ca) are subject to inhibition by transmitter/hormone receptor activation of heterotrimeric G-proteins. However, the direct effect of histamine on I(Ca) in chromaffin cells is unknown. This paper reports that histamine inhibited I(Ca) in cultured bovine adrenal chromaffin cells and this response was blocked by the H(1) antagonist mepyramine. With high levels of calcium buffering in the patch pipette solution (10 mM EGTA), histamine slowed the activation kinetics and inhibited the amplitude of I(Ca). A conditioning prepulse to +100 mV reversed the kinetic slowing and partially relieved the inhibition. These features are characteristic of a membrane delimited, voltage-dependent pathway which is thought to involve direct binding of G-protein betagamma subunits to the Ca channels. However, unlike virtually every other example of this type of inhibition, the response to histamine was not blocked by pretreating the cells with pertussis toxin (PTX). The voltage-dependent, PTX insensitive inhibition produced by histamine was modest compared with the PTX sensitive inhibition produced by ATP (28% vs. 53%). When histamine and ATP were applied concomitantly there was no additivity of the inhibition beyond that produced by ATP alone (even though the agonists appear to activate distinct G-proteins) suggesting that the inhibition produced by ATP is maximal. When experiments were carried out under conditions of low levels of calcium buffering in the patch pipette solution (0.1 mM EGTA), histamine inhibited I(Ca) in some cells using an entirely voltage insensitive pathway. We demonstrate that activation of PTX insensitive G-proteins (most likely Gq) by H(1) receptors inhibits I(Ca). This may represent a mechanism by which histamine exerts inhibitory (in addition to previously identified stimulatory) effects on catecholamine release.
Collapse
Affiliation(s)
- K P Currie
- Department of Neurobiology, Pharmacology and Physiology, The University of Chicago, Chicago, Illinois 60637, USA
| | | |
Collapse
|
40
|
Colecraft HM, Patil PG, Yue DT. Differential occurrence of reluctant openings in G-protein-inhibited N- and P/Q-type calcium channels. J Gen Physiol 2000; 115:175-92. [PMID: 10653895 PMCID: PMC2217198 DOI: 10.1085/jgp.115.2.175] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Voltage-dependent inhibition of N- and P/Q-type calcium channels by G proteins is crucial for presynaptic inhibition of neurotransmitter release, and may contribute importantly to short-term synaptic plasticity. Such calcium-channel modulation could thereby impact significantly the neuro-computational repertoire of neural networks. The differential modulation of N and P/Q channels could even further enrich their impact upon synaptic tuning. Here, we performed in-depth comparison of the G-protein inhibition of recombinant N and P/Q channels, expressed in HEK 293 cells with the m2 muscarinic receptor. While both channel types display classic features of G-protein modulation (kinetic slowing of activation, prepulse facilitation, and voltage dependence of inhibition), we confirmed previously reported quantitative differences, with N channels displaying stronger inhibition and greater relief of inhibition by prepulses. A more fundamental, qualitative difference in the modulation of these two channels was revealed by a modified tail-activation paradigm, as well as by a novel "slope" analysis method comparing time courses of slow activation and prepulse facilitation. The stark contrast in modulatory behavior can be understood within the context of the "willing-reluctant" model, in which binding of G-protein betagamma subunits to channels induces a reluctant mode of gating, where stronger depolarization is required for opening. Our experiments suggest that only N channels could be opened in the reluctant mode, at voltages normally spanned by neuronal action potentials. By contrast, P/Q channels appear to remain closed, especially over these physiological voltages. Further, the differential occurrence of reluctant openings is not explained by differences in the rate of G-protein unbinding from the two channels. These two scenarios predict very different effects of G-protein inhibition on the waveform of Ca(2+) entry during action potentials, with potentially important consequences for the timing and efficacy of synaptic transmission.
Collapse
Affiliation(s)
- Henry M. Colecraft
- From the Program in Molecular and Cellular Systems Physiology, Departments of Biomedical Engineering and Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Parag G. Patil
- From the Program in Molecular and Cellular Systems Physiology, Departments of Biomedical Engineering and Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - David T. Yue
- From the Program in Molecular and Cellular Systems Physiology, Departments of Biomedical Engineering and Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| |
Collapse
|
41
|
Greif GJ, Sodickson DL, Bean BP, Neer EJ, Mende U. Altered regulation of potassium and calcium channels by GABA(B) and adenosine receptors in hippocampal neurons from mice lacking Galpha(o). J Neurophysiol 2000; 83:1010-8. [PMID: 10669512 DOI: 10.1152/jn.2000.83.2.1010] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To examine the role of G(o) in modulation of ion channels by neurotransmitter receptors, we characterized modulation of ionic currents in hippocampal CA3 neurons from mice lacking both isoforms of Galpha(o). In CA3 neurons from Galpha(o)(-/-) mice, 2-chloro-adenosine and the GABA(B)-receptor agonist baclofen activated inwardly rectifying K(+) currents and inhibited voltage-dependent Ca(2+) currents just as effectively as in Galpha(o)(+/+) littermates. However, the kinetics of transmitter action were dramatically altered in Galpha(o)(-/-) mice in that recovery on washout of agonist was much slower. For example, recovery from 2-chloro-adenosine inhibition of calcium current was more than fourfold slower in neurons from Galpha(o)(-/-) mice [time constant of 12.0 +/- 0.8 (SE) s] than in neurons from Galpha(o)(+/+) mice (time constant of 2.6 +/- 0.2 s). Recovery from baclofen effects was affected similarly. In neurons from control mice, effects of both baclofen and 2-chloro-adenosine on Ca(2+) currents and K(+) currents were abolished by brief exposure to external N-ethyl-maleimide (NEM). In neurons lacking Galpha(o), some inhibition of Ca(2+) currents by baclofen remained after NEM treatment, whereas baclofen activation of K(+) currents and both effects of 2-chloro-adenosine were abolished. These results show that modulation of Ca(2+) and K(+) currents by G protein-coupled receptors in hippocampal neurons does not have an absolute requirement for Galpha(o). However, modulation is changed in the absence of Galpha(o) in having much slower recovery kinetics. A likely possibility is that the very abundant Galpha(o) is normally used but, when absent, can readily be replaced by G proteins with different properties.
Collapse
Affiliation(s)
- G J Greif
- Department of Neurobiology, Harvard Medical School, Massachusetts 02115, USA
| | | | | | | | | |
Collapse
|
42
|
The CB1 cannabinoid receptor can sequester G-proteins, making them unavailable to couple to other receptors. J Neurosci 1999. [PMID: 10531431 DOI: 10.1523/jneurosci.19-21-09271.1999] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We tested the hypothesis that human CB1 cannabinoid receptors (hCB1) can sequester G(i/o)-proteins from a common pool and prevent other receptors from signaling. Human CB1 cannabinoid receptors were expressed in superior cervical ganglion (SCG) neurons by microinjection of hCB1 cDNA. Expression of hCB1 cannabinoid receptors abolished the Ca(2+) current inhibition by endogenous pertussis toxin-sensitive G(i/o)-coupled receptors for norepinephrine (NE) and somatostatin (SOM) but not by endogenous pertussis toxin-insensitive G(s)-coupled receptors for vasoactive intestinal polypeptide. Signaling by NE was rescued by expression of Galpha(oB), Gbeta(1), and Ggamma(3). Expression of mGluR2 metabotropic glutamate receptors, another pertussis toxin-sensitive G-protein-coupled receptor, had no effect on the signaling by NE or SOM. Some hCB1 receptors were constitutively active because the cannabinoid receptor inverse agonist SR 141617A enhanced the Ca(2+) current. Some hCB1 receptors also appear to be precoupled to G(i/o)-proteins because the cannabinoid agonist WIN 55,212-2 decreased the Ca(2+) current at a time when no G-proteins were available to couple to alpha(2)-adrenergic and somatostatin receptors. In SCG neurons microinjected with a lower concentration of hCB1 cDNA, the effect of SR 141716A was reduced, and the response to NE and SOM was partially restored. Subsequent to the application of SR 141716A, the Ca(2+) current inhibition by NE and SOM was abolished. These results suggest that both the active and inactive states of the hCB1 receptor can sequester G(i/o)-proteins from a common pool. Cannabinoid receptors thus have the potential to prevent other G(i/o)-coupled receptors from transducing their biological signals.
Collapse
|
43
|
Ikeda SR, Jeong SW, Kammermeier PJ, Ruiz-Velasco V, King MM. Heterologous expression of a green fluorescent protein-pertussis toxin S1 subunit fusion construct disrupts calcium channel modulation in rat superior cervical ganglion neurons. Neurosci Lett 1999; 271:163-6. [PMID: 10507694 DOI: 10.1016/s0304-3940(99)00555-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The fusion construct pEGFP-PTXS1 was assembled by ligating cDNA encoding the S1 subunit of Bordetella pertussis toxin (PTX) into the plasmid pEGFP-C1 (which codes for enhanced green fluorescent protein). Microinjection of pEGFP-PTXS1 (1-100 ng/microl) into the nucleus of dissociated rat sympathetic ganglion neurons resulted in functional expression as determined from the diffuse green fluorescence and disruption of norepinephrine-mediated N-type Ca2+ channel modulation. The heterologously expressed toxin retained specificity for G alpha(i/o)-dependent pathways as VIP-mediated modulation of N-type Ca2+ channels and muscarine-mediated inhibition of M-type K+ channels persisted in pEGFP-PTXS1 expressing neurons. These data demonstrate that the S1 subunit of PTX is readily expressed in mammalian neurons and remains functional following fusion to the C-terminus of another protein.
Collapse
Affiliation(s)
- S R Ikeda
- Laboratory of Molecular Physiology, Guthrie Research Institute, Sayre, PA 18840-1692, USA.
| | | | | | | | | |
Collapse
|
44
|
Sequestration of G-protein beta gamma subunits by different G-protein alpha subunits blocks voltage-dependent modulation of Ca2+ channels in rat sympathetic neurons. J Neurosci 1999. [PMID: 10366609 DOI: 10.1523/jneurosci.19-12-04755.1999] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The membrane-delimited and voltage-dependent inhibition of N-type Ca2+ channels is mediated by Gbeta gamma subunits. Previously, exogenous excess GDP-bound GalphaoA has been shown to dramatically attenuate the norepinephrine (NE)-mediated Ca2+ current inhibition by sequestration of Gbeta gamma subunits in rat superior cervical ganglion (SCG) neurons. In the present study, we determined whether the attenuation of NE-mediated modulation is specific to GalphaoA or shared by a number of closely related (Galphatr, GalphaoB, Galphai1, Galphai2, Galphai3, Galphaz) or unrelated (Galphas, Galphaq, Galpha11, Galpha16, Galpha12, Galpha13) Galpha subunits. Individual Galpha subunits from different subfamilies were transiently overexpressed in SCG neurons by intranuclear injection of mammalian expression vectors encoding the desired protein. Strikingly, all Galpha subunits except Galphaz nearly blocked basal facilitation and NE-mediated modulation. Likewise, VIP-mediated Ca2+ current inhibition, which is mediated by cholera toxin-sensitive G-protein, was also completely suppressed by a number of Galpha subunits overexpressed in neurons. Galphas expression produced either enhancement or attenuation of the VIP-mediated modulation-an effect that seemed to depend on the expression level. The onset of the nonhydrolyzable GTP analog, guanylylimidodiphosphate-mediated facilitation was significantly delayed by overexpression of different GDP-bound Galpha subunits. Taken together, these data suggest that a wide variety of Galpha subunits are capable of forming heterotrimers with endogenous Gbeta gamma subunits mediating voltage-dependent Ca2+ channel inhibition. In conclusion, coupling specificity in signal transduction is unlikely to arise as a result of restricted Galpha/Gbeta gamma interaction.
Collapse
|
45
|
Hayashi K, Endoh T, Suzuki T. VIP inhibits high voltage-gated calcium channel currents of hamster submandibular ganglion neurons. THE BULLETIN OF TOKYO DENTAL COLLEGE 1999; 40:93-7. [PMID: 10825819 DOI: 10.2209/tdcpublication.40.93] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In this study, we investigated the modulation of calcium channels by vasoactive intestinal polypeptide (VIP) in hamster submandibular ganglion (SMG) cells using the whole-cell patch clamp technique. VIP (1 microM) inhibited the high voltage-gated calcium channels in the SMG neurons via activation of VIP receptors and G-protein coupled to these receptors, but did not affect the low voltage-gated calcium channels. VIP at 1 microM reduced the peak amplitude of the maximum high voltage-gated calcium current by 26.0 +/- 6.2% (mean +/- S.E., n = 5) and slowed the rising phase of the calcium current. The time to peak of the maximum high voltage-gated calcium current was prolonged from 16.8 msec to 22.4 msec. In a representative cell, 1 microM VIP reduced the peak amplitude of maximum high voltage-gated calcium current by 50.5% and the amplitude at the end of voltage step after 300 msec by 51.9%. The VIP-induced inhibition of the calcium current was produced in a voltage-dependent manner. Inhibition was maximal (50.5%) at the level of -20 mV. Therefore, VIP inhibits both transient and sustained types of high voltage-gated calcium channels in the hamster SMG neuron.
Collapse
Affiliation(s)
- K Hayashi
- Department of Physiology, Tokyo Dental College, Chiba, Japan
| | | | | |
Collapse
|
46
|
Dolphin AC, Page KM, Berrow NS, Stephens GJ, Cantí C. Dissection of the calcium channel domains responsible for modulation of neuronal voltage-dependent calcium channels by G proteins. Ann N Y Acad Sci 1999; 868:160-74. [PMID: 10414293 DOI: 10.1111/j.1749-6632.1999.tb11285.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The molecular determinants for G-protein regulation of neuronal calcium channels remain controversial. We have generated a series of alpha 1B/alpha 1E chimeric channels, since rat brain alpha 1E (rbEII), unlike human alpha 1E, showed no G-protein modulation. The study, carried out in parallel using D2 receptor modulation of calcium currents in Xenopus oocytes of G beta gamma modulation of calcium currents in COS-7 cells, consistently showed an essential role for domain I (from the N terminus to the end of the I-II loop) of the alpha 1B Ca2+ channel in G-protein regulation, with no additional effect of the C terminal of alpha 1B. The I-II loop alone of alpha 1B, or the I-II loop together with the C-terminal tail, was insufficient to confer G-protein modulation of alpha 1E (rbEII). We have further observed that the alpha 1E clone rbEII is truncated at the N-terminus compared to other alpha 1 subunits, and we isolated a PCR product from rat brain equivalent to a longer N-terminal isoform. The long N-terminal alpha 1E, unlike the short form, showed G-protein modulation. Furthermore, the equivalent truncation of alpha 1B (delta N1-55) abolished G-protein modulation of alpha 1B. Thus, we propose that the N terminus of alpha 1B and alpha 1E calcium channels contains essential molecular determinants for membrane-delimited G-protein inhibition, and that other regions, including the I-II loop and the C terminus, do not play a conclusive role alone.
Collapse
Affiliation(s)
- A C Dolphin
- Department of Pharmacology, University College London, United Kingdom.
| | | | | | | | | |
Collapse
|
47
|
Ikeda SR, Dunlap K. Voltage-dependent modulation of N-type calcium channels: role of G protein subunits. ADVANCES IN SECOND MESSENGER AND PHOSPHOPROTEIN RESEARCH 1999; 33:131-51. [PMID: 10218117 DOI: 10.1016/s1040-7952(99)80008-1] [Citation(s) in RCA: 138] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- S R Ikeda
- Laboratory of Molecular Physiology, Guthrie Research Institute, Sayre, Pennsylvania 18840, USA
| | | |
Collapse
|
48
|
Kammermeier PJ, Ikeda SR. Expression of RGS2 alters the coupling of metabotropic glutamate receptor 1a to M-type K+ and N-type Ca2+ channels. Neuron 1999; 22:819-29. [PMID: 10230801 DOI: 10.1016/s0896-6273(00)80740-0] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Group I mGluRs heterologously expressed in sympathetic neurons inhibited calcium (I(Ca)) and M-type potassium (I(M)) currents. Treatment with pertussis toxin (PTX) revealed a voltage-dependent (VD), PTX-sensitive component of I(Ca) inhibition and a voltage-independent (VI), PTX-insensitive component. Coexpression of RGS2 occluded mGluR1a inhibition of I(M) and made I(Ca) inhibition VD in PTX-treated cells, presumably by blocking the effects of G alpha(q/11)-GTP. These data indicate that mGluR1a can couple to G(i/o) as well as G(q/11). In addition, VI I(Ca) inhibition proceeds through a G alpha(q/11)-GTP-mediated pathway, which can be occluded by expressing RGS2, leaving the VD, G betagamma-mediated inhibition active. These data may reveal a functional role for the upregulation of RGS2 expression in in vivo systems.
Collapse
Affiliation(s)
- P J Kammermeier
- Laboratory of Molecular Physiology, Guthrie Research Institute, Sayre, Pennsylvania 18840, USA
| | | |
Collapse
|
49
|
Thiel G, Cibelli G. Corticotropin-releasing factor and vasoactive intestinal polypeptide activate gene transcription through the cAMP signaling pathway in a catecholaminergic immortalized neuron. Neurochem Int 1999; 34:183-91. [PMID: 10355485 DOI: 10.1016/s0197-0186(98)00086-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Corticotropin-releasing factor (CRF) and vasoactive intestinal polypeptide (VIP) are neuropeptides displaying a variety of short-term effects in the nervous system. It is shown here in transfection experiments of an immortalized noradrenergic locus coeruleus-like cell line that both CRF and VIP also trigger a signaling cascade capable of activating gene transcription. To elucidate the signaling pathway leading to transcriptional induction, cells were transfected with an inhibitor for cAMP-dependent protein kinase, targeted to the nucleus via a nuclear-localization signal. Transcriptional induction of a reporter gene by CRF and VIP was blocked in these cells, indicating that the cAMP-dependent protein kinase is required for transducing CRF and VIP generated signals into the nucleus. Additionally, transfection experiments with a reporter gene containing cAMP response elements in its regulatory region demonstrate that CRF and VIP receptor activation induce transcription through this genetic regulatory element. We conclude that long-term effects of CRF and VIP in neurons are likely to be mediated by the transcriptional regulation of CRF and VIP-responsive genes via the cAMP signaling pathway.
Collapse
Affiliation(s)
- G Thiel
- Medical Biochemistry and Molecular Biology, University of the Saarland, Medical School, Homburg, Germany.
| | | |
Collapse
|
50
|
Receptor-Mediated Modulation of Voltage-Dependent Ca2+ Channels via Heterotrimeric G-proteins in Neurons. ACTA ACUST UNITED AC 1999. [DOI: 10.1016/s0021-5198(19)30742-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|