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Vila A, Shihabeddin E, Zhang Z, Santhanam A, Ribelayga CP, O'Brien J. Synaptic Scaffolds, Ion Channels and Polyamines in Mouse Photoreceptor Synapses: Anatomy of a Signaling Complex. Front Cell Neurosci 2021; 15:667046. [PMID: 34393723 PMCID: PMC8356055 DOI: 10.3389/fncel.2021.667046] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 07/05/2021] [Indexed: 12/29/2022] Open
Abstract
Synaptic signaling complexes are held together by scaffold proteins, each of which is selectively capable of interacting with a number of other proteins. In previous studies of rabbit retina, we found Synapse-Associated Protein-102 (SAP102) and Channel Associated Protein of Synapse-110 (Chapsyn110) selectively localized in the tips of horizontal cell processes at contacts with rod and cone photoreceptors, along with several interacting ion channels. We have examined the equivalent suites of proteins in mouse retina and found similarities and differences. In the mouse retina we identified Chapsyn110 as the scaffold selectively localized in the tips of horizontal cells contacting photoreceptors, with Sap102 more diffusely present. As in rabbit, the inward rectifier potassium channel Kir2.1 was present with Chapsyn110 on the tips of horizontal cell dendrites within photoreceptor invaginations, where it could provide a hyperpolarization-activated current that could contribute to ephaptic signaling in the photoreceptor synapses. Pannexin 1 and Pannexin 2, thought to play a role in ephaptic and/or pH mediated signaling, were present in the outer plexiform layer, but likely not in the horizontal cells. Polyamines regulate many ion channels and control the degree of rectification of Kir2.1 by imposing a voltage-dependent block. During the day polyamine immunolabeling was unexpectedly high in photoreceptor terminals compared to other areas of the retina. This content was significantly lower at night, when polyamine content was predominantly in Müller glia, indicating daily rhythms of polyamine content. Both rod and cone terminals displayed the same rhythm. While polyamine content was not prominent in horizontal cells, if polyamines are released, they may regulate the activity of Kir2.1 channels located in the tips of HCs. The rhythmic change in polyamine content of photoreceptor terminals suggests that a daily rhythm tunes the behavior of suites of ion channels within the photoreceptor synapses.
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Affiliation(s)
- Alejandro Vila
- Richard S. Ruiz M.D. Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, TX, United States.,MD Anderson Cancer Center, UTHealth Graduate School of Biomedical Sciences, Houston, TX, United States
| | - Eyad Shihabeddin
- Richard S. Ruiz M.D. Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, TX, United States.,MD Anderson Cancer Center, UTHealth Graduate School of Biomedical Sciences, Houston, TX, United States
| | - Zhijing Zhang
- Richard S. Ruiz M.D. Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, TX, United States
| | - Abirami Santhanam
- Richard S. Ruiz M.D. Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, TX, United States
| | - Christophe P Ribelayga
- Richard S. Ruiz M.D. Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, TX, United States.,MD Anderson Cancer Center, UTHealth Graduate School of Biomedical Sciences, Houston, TX, United States
| | - John O'Brien
- Richard S. Ruiz M.D. Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, TX, United States.,MD Anderson Cancer Center, UTHealth Graduate School of Biomedical Sciences, Houston, TX, United States
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Killi UK, Wsol V, Soukup O, Kuca K, Winder M, Tobin G. In vitro functional interactions of acetylcholine esterase inhibitors and muscarinic receptor antagonists in the urinary bladder of the rat. Clin Exp Pharmacol Physiol 2013; 41:139-46. [PMID: 24341923 DOI: 10.1111/1440-1681.12191] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Revised: 11/05/2013] [Accepted: 11/07/2013] [Indexed: 11/27/2022]
Abstract
Obidoxime, a weak acetylcholine-esterase (AChE) inhibitor, exerts muscarinic receptor antagonism with a significant muscarinic M2 receptor selective profile. The current examinations aimed to determine the functional significance of muscarinic M2 receptors in the state of AChE inhibition, elucidating muscarinic M2 and M3 receptor interaction. In the in vitro examinations, methacholine evoked concentration-dependent bladder contractile and atrial frequency inhibitory responses. Although atropine abolished both, methoctramine (1 μmol/L) only affected the cholinergic response in the atrial preparations. However, in the presence of methoctramine, physostigmine, an AChE inhibitor, increased the basal tension of the bladder strip preparations (+68%), as well as the contractile responses to low concentrations of methacholine (< 5 μmol/L; +90-290%). In contrast to physostigmine, obidoxime alone raised the basal tension (+58%) and the responses to low concentrations of methacholine (< 5 μmol/L; +80-450%). Physostigmine concentration-dependently increased methacholine-evoked responses, similarly to obidoxime at low concentrations. However, at large concentrations (> 5 μmol/L), obidoxime, because of its unselective muscarinic receptor antagonism, inhibited the methacholine bladder responses. In conclusion, the current results show that muscarinic M2 receptors inhibit muscarinic M3 receptor-evoked contractile responses to low concentrations of acetylcholine in the synaptic cleft. The muscarinic M2 and M3 receptor crosstalk could be a counteracting mechanism in the treatment of AChE inhibition when using reactivators, such as obidoxime.
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Affiliation(s)
- Uday K Killi
- Department of Biochemical Sciences, Faculty of Pharmacy, Charles University, Hradec Kralove, Czech Republic
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3
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Kupchik YM, Barchad-Avitzur O, Wess J, Ben-Chaim Y, Parnas I, Parnas H. A novel fast mechanism for GPCR-mediated signal transduction--control of neurotransmitter release. ACTA ACUST UNITED AC 2011; 192:137-51. [PMID: 21200029 PMCID: PMC3019563 DOI: 10.1083/jcb.201007053] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In addition to calcium influx, charge movement in the G protein–coupled M2-muscarinic receptor is required for the control of acetylcholine release. Reliable neuronal communication depends on accurate temporal correlation between the action potential and neurotransmitter release. Although a requirement for Ca2+ in neurotransmitter release is amply documented, recent studies have shown that voltage-sensitive G protein–coupled receptors (GPCRs) are also involved in this process. However, how slow-acting GPCRs control fast neurotransmitter release is an unsolved question. Here we examine whether the recently discovered fast depolarization-induced charge movement in the M2-muscarinic receptor (M2R) is responsible for M2R-mediated control of acetylcholine release. We show that inhibition of the M2R charge movement in Xenopus oocytes correlated well with inhibition of acetylcholine release at the mouse neuromuscular junction. Our results suggest that, in addition to Ca2+ influx, charge movement in GPCRs is also necessary for release control.
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Affiliation(s)
- Yonatan M Kupchik
- Department of Neurobiology, Institute of Life Sciences, Hebrew University, Jerusalem, Israel
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Graves AR, Lewin KA, A Lindgren C. Nitric oxide, cAMP and the biphasic muscarinic modulation of ACh release at the lizard neuromuscular junction. J Physiol 2004; 559:423-32. [PMID: 15235096 PMCID: PMC1665131 DOI: 10.1113/jphysiol.2004.064469] [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: 11/08/2022] Open
Abstract
In this study, we characterized the pharmacology and physiology of the automodulation of ACh release at the lizard neuromuscular junction (NMJ). The activation of muscarinic ACh receptors generated a biphasic modulation of synaptic transmission. Muscarine-induced activation of M3 receptors (0-12 min) decreased release, whereas M1 activation (> 12 min) enhanced release. Both phases of the biphasic effect are dependent on nitric oxide. However, cAMP acting via protein kinase A is also necessary for the M1 effect. In summary, we present a novel biphasic role for muscarine and implicate M3 receptors in the inhibition and M1 receptors in the enhancement of transmitter releaseat the cholinergic lizard NMJ.
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Affiliation(s)
- Austin R Graves
- Department of Biology Grinnell College 1116 8th Avenue Grinnell, IA 50112, USA
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Melchiorre C, Antonello A, Banzi R, Bolognesi ML, Minarini A, Rosini M, Tumiatti V. Polymethylene tetraamine backbone as template for the development of biologically active polyamines. Med Res Rev 2003; 23:200-33. [PMID: 12500289 DOI: 10.1002/med.10029] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The concept that polyamines may represent a universal template in the receptor recognition process is embodied in the design of ligands for different biological targets. As a matter of fact, the insertion of different pharmacophores onto the polymethylene tetraamine backbone can tune both affinity and selectivity for any given receptor. The application of this approach provided a prospect of modifying benextramine (1). structure to achieve specific recognition of muscarinic receptors that led to the discovery of methoctramine (2). which is widely used as a pharmacological tool for muscarinic receptor characterization. In turn, appropriate structural modifications performed on the structure of methoctramine led to the discovery of new polyamines endowed with high affinity and selectivity for (a). muscarinic receptor subtypes, (b). G(i) proteins, and (c). muscle-type nicotinic receptors. Thus, polyamines tripitramine (9) and spirotramine (33), among others, were designed, which were shown to be highly selective for muscarinic M(2) and M(1) receptors, respectively. Several polyamines have been discovered, which inhibit noncompetitively a closed state of the nicotinic receptor. These ligands, such as 66, resulted in important tools for elucidating the mode and site of interaction of polyamines with the ion channel. It was discovered that reducing the flexibility of the diaminohexane spacer of methoctramine led to polyamines, such as 70, which are endowed with a biological profile significantly different from that of the prototype. Most likely, tetraamine (70) is a potent activator of G(i) proteins. Finally, the universal template approach formed the basis for modifying benextramine (1) structure to the design of ligands, which display affinity for acetylcholinesterase and muscarinic M(2) receptors. Thus, these polyamines, such as caproctamine (78), could have potential in the investigation of Alzheimer disease.
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Affiliation(s)
- Carlo Melchiorre
- Dipartimento di Scienze Farmaceutiche, Alma Mater Studiorum-Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy.
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Abstract
Signaling pathways leading to exocytosis and arachidonate release from serosal mast cells by basic secretagogues, including cationic peptides, arise from the involvement of betagamma subunits from G(i2) and G(i3) GTP-binding proteins. The original concept that basic secretagogues directly interact with G proteins implicated the entry of secretagogues into mast cells. This has been demonstrated only for the neuropeptide substance P. Basic secretagogues might share a common mechanism of penetration with the newly described cell-penetrating peptides. The involvement of some membrane transporter or non-selective membrane receptor to basic secretagogues cannot be excluded.
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Affiliation(s)
- Xavier Ferry
- Laboratoire de Neuroimmunopharmacologie, Faculté de Pharmacie, INSERM U425, Université Louis Pasteur-Strasbourg I, bp 24, 67401 Illkirch Cedex, France
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Ferry X, Landry Y. Agmatine: a mastoparan-like activity related to direct activation of heterotrimeric G proteins. Eur J Pharmacol 2002; 435:19-26. [PMID: 11790374 DOI: 10.1016/s0014-2999(01)01561-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We examined agmatine and imidazoline derivatives as putative ligands of trimeric G protein in rat peritoneal mast cells. Agmatine induced a concentration-dependent and pertussis toxin-sensitive secretion of histamine (exocytosis) and arachidonate. Clonidine and idazoxan had no effect. Blockage of Gbetagamma dimers by a specific anti-Gbeta antibody inhibited exocytosis elicited by agmatine and mastoparan. The G protein antagonist [p-Glu(5),D-Trp(7,9,10)]substance P-(5-11) prevented both mastoparan- and agmatine-induced exocytosis when it was allowed to reach its intracellular targets by streptolysin-O permeabilisation. In intact cells, this response was prevented by both the removal of sialic acid residues by neuraminidase and by [D-Pro(4),D-Trp(7,9,10)]substance P-(4-11) acting at the mast cell surface. Exocytosis was restored by permeabilisation of the plasma membrane with streptolysin-O. These results suggest that agmatine might have several molecular targets, exerting its neurotransmitter function at low concentrations (i.e., with high affinity) through membrane receptors and at high concentrations (i.e., with weak affinity) through direct G protein activation.
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Affiliation(s)
- Xavier Ferry
- Faculté de Pharmacie, bp 24, Laboratoire de Neuroimmunopharmacologie, INSERM U425, Université Louis Pasteur-Strasbourg I, 67401 Illkirch Cedex, France
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Melchiorre C, Bolognesi ML, Budriesi R, Ghelardini C, Chiarini A, Minarini A, Rosini M, Tumiatti V, Wade EJ. Design, synthesis, and biological activity of methoctramine-related polyamines as putative G(i) protein activators. J Med Chem 2001; 44:4035-8. [PMID: 11708906 DOI: 10.1021/jm0155594] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The universal template approach provided a prospect of modifying methoctramine (2) structure. Thus, polyamines 3-7 were designed in which the flexibility of the diaminohexane spacer of 2 was replaced by a bipiperidinyl moiety. In electrically stimulated guinea pig left atria, these novel polyamines, unlike prototype 2, displayed a potent intrinsic activity, which was in contrast with the muscarinic antagonism shown in binding studies by some of them (3 and 4) and was inhibited by benzalkonium chloride, an inhibitor of G(i) proteins.
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Affiliation(s)
- C Melchiorre
- Department of Pharmaceutical Sciences, University of Bologna, Via Belmeloro 6, 40126 Bologna, Italy.
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9
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Ferry X, Eichwald V, Daeffler L, Landry Y. Activation of betagamma subunits of G(i2) and G(i3) proteins by basic secretagogues induces exocytosis through phospholipase Cbeta and arachidonate release through phospholipase Cgamma in mast cells. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2001; 167:4805-13. [PMID: 11673483 DOI: 10.4049/jimmunol.167.9.4805] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Mast cells are activated by Ag-induced clustering of IgE bound to FcepsilonRI receptors or by basic secretagogues that stimulate pertussis toxin-sensitive heterotrimeric G proteins. The cell response includes the secretion of stored molecules, such as histamine, through exocytosis and of de novo synthesized mediators, such as arachidonate metabolites. The respective roles of G proteins alpha and betagamma subunits as well as various types of phospholipase C (PLC) in the signaling pathways elicited by basic secretagogues remain unknown. We show that a specific Ab produced against the C-terminus of Galpha(i3) and an anti-recombinant Galpha(i2) Ab inhibited, with additive effects, both exocytosis and arachidonate release from permeabilized rat peritoneal mast cells elicited by the basic secretagogues mastoparan and spermine. A specific Ab directed against Gbetagamma dimers prevented both secretions. Anti-PLCbeta Abs selectively prevented exocytosis. The selective phosphatidylinositol 3-kinase inhibitor LY 294002 prevented arachidonate release without modifying exocytosis. Gbetagamma coimmunoprecipitated with PLCbeta and phosphatidylinositol 3-kinase. The anti-PLCgamma1 and anti-phospholipase A(2) Abs selectively blocked arachidonate release. Protein tyrosine phosphorylation was inhibited by anti-Gbetagamma Abs, LY294002, and anti PLCgamma1 Abs. These data show that the early step of basic secretagogue transduction is common to both signaling pathways, involving betagamma subunits of G(i2) and G(i3) proteins. Activated Gbetagamma interacts, on one hand, with PLCbeta to elicit exocytosis and, on the other hand, with phosphatidylinositol 3-kinase to initiate the sequential activation of PLCgamma1, tyrosine kinases, and phospholipase A(2), leading to arachidonate release.
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Affiliation(s)
- X Ferry
- Laboratoire de Neuroimmunopharmacologie, Institut National de la Santé et de la Recherche Médicale, Unité 425, Université Louis Pasteur-Strasbourg I, Faculté de Pharmacie, Illkirch, France
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10
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Daeffler L, Landry Y. Inverse agonism at heptahelical receptors: concept, experimental approach and therapeutic potential. Fundam Clin Pharmacol 2000; 14:73-87. [PMID: 10796054 DOI: 10.1111/j.1472-8206.2000.tb00395.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Inverse agonists (negative antagonists) are ligands that stabilize the inactive conformation (R) of receptors according to the two-state receptor model. The active conformation (R*) of heptahelical receptors, i.e. G protein-coupled receptors, has high affinity for G proteins. According to ternary complex models of receptor activation, the R*G complex is in equilibrium with R + G, with spontaneous activity in the absence of agonist. Inverse agonists, having a higher affinity for R, shift R*G towards R + G, decreasing the spontaneous activity of receptors. Agonists have the opposite effect, with a higher affinity for R*. Neutral antagonists have the same affinity for R and R* and compete for both agonists and inverse agonists. Inverse agonists have been recently proposed for a variety of heptahelical receptors. Methods to detect inverse agonists among antagonists are based on the determination of ligand affinity at R and R* with binding experiments, and on the modulation of G protein activity (GTP binding and hydrolysis) or of effector activity. Receptor inverse agonists, but also G protein antagonists and GTPase inhibitors, decrease spontaneous G protein activity corresponding to R*G. Receptor agonists, G protein agonists and GTPase inhibitors increase effector basal activity, but receptor inverse agonists decrease it. The therapeutic potential of inverse agonists is proposed in human diseases ascribed to constitutively active mutant receptors and may be extended to diseases related to wild-type receptor over-expression leading to the increase of R*. Some of the therapeutic effects of presently used receptor antagonists may be related to their inverse agonist properties. Inverse agonists lead to receptor upregulation, offering new approaches to tolerance and dependence to drugs.
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Affiliation(s)
- L Daeffler
- Laboratoire de neuroimmunopharmacologie, INSERM U 425, faculté de pharmacie, université Strasbourg, Illkirch, France
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