1
|
Juza R, Musilek K, Mezeiova E, Soukup O, Korabecny J. Recent advances in dopamine D 2 receptor ligands in the treatment of neuropsychiatric disorders. Med Res Rev 2023; 43:55-211. [PMID: 36111795 DOI: 10.1002/med.21923] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 07/29/2022] [Accepted: 08/09/2022] [Indexed: 02/04/2023]
Abstract
Dopamine is a biologically active amine synthesized in the central and peripheral nervous system. This biogenic monoamine acts by activating five types of dopamine receptors (D1-5 Rs), which belong to the G protein-coupled receptor family. Antagonists and partial agonists of D2 Rs are used to treat schizophrenia, Parkinson's disease, depression, and anxiety. The typical pharmacophore with high D2 R affinity comprises four main areas, namely aromatic moiety, cyclic amine, central linker and aromatic/heteroaromatic lipophilic fragment. From the literature reviewed herein, we can conclude that 4-(2,3-dichlorophenyl), 4-(2-methoxyphenyl)-, 4-(benzo[b]thiophen-4-yl)-1-substituted piperazine, and 4-(6-fluorobenzo[d]isoxazol-3-yl)piperidine moieties are critical for high D2 R affinity. Four to six atoms chains are optimal for D2 R affinity with 4-butoxyl as the most pronounced one. The bicyclic aromatic/heteroaromatic systems are most frequently occurring as lipophilic appendages to retain high D2 R affinity. In this review, we provide a thorough overview of the therapeutic potential of D2 R modulators in the treatment of the aforementioned disorders. In addition, this review summarizes current knowledge about these diseases, with a focus on the dopaminergic pathway underlying these pathologies. Major attention is paid to the structure, function, and pharmacology of novel D2 R ligands, which have been developed in the last decade (2010-2021), and belong to the 1,4-disubstituted aromatic cyclic amine group. Due to the abundance of data, allosteric D2 R ligands and D2 R modulators from patents are not discussed in this review.
Collapse
Affiliation(s)
- Radomir Juza
- Experimental Neurobiology, National Institute of Mental Health, Klecany, Czech Republic.,Department of Chemistry, Faculty of Science, University of Hradec Kralove, Hradec Kralove, Czech Republic
| | - Kamil Musilek
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, Hradec Kralove, Czech Republic.,Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| | - Eva Mezeiova
- Experimental Neurobiology, National Institute of Mental Health, Klecany, Czech Republic.,Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| | - Ondrej Soukup
- Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| | - Jan Korabecny
- Experimental Neurobiology, National Institute of Mental Health, Klecany, Czech Republic.,Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| |
Collapse
|
2
|
Juza R, Vlcek P, Mezeiova E, Musilek K, Soukup O, Korabecny J. Recent advances with 5-HT 3 modulators for neuropsychiatric and gastrointestinal disorders. Med Res Rev 2020; 40:1593-1678. [PMID: 32115745 DOI: 10.1002/med.21666] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Revised: 11/10/2019] [Accepted: 02/11/2020] [Indexed: 12/17/2022]
Abstract
Serotonin (5-hydroxytryptophan [5-HT]) is a biologically active amine expressed in platelets, in gastrointestinal (GI) cells and, to a lesser extent, in the central nervous system (CNS). This biogenic compound acts through the activation of seven 5-HT receptors (5-HT1-7 Rs). The 5-HT3 R is a ligand-gated ion channel belonging to the Cys-loop receptor family. There is a wide variety of 5-HT3 R modulators, but only receptor antagonists (known as setrons) have been used clinically for chemotherapy-induced nausea and vomiting and irritable bowel syndrome treatment. However, since the discovery of the setrons in the mid-1980s, a large number of studies have been published exploring new potential applications due their potency in the CNS and mild side effects. The results of these studies have revealed new potential applications, including the treatment of neuropsychiatric disorders such as schizophrenia, depression, anxiety, and drug abuse. In this review, we provide information related to therapeutic potential of 5-HT3 R antagonists on GI and neuropsychiatric disorders. The major attention is paid to the structure, function, and pharmacology of novel 5-HT3 R modulators developed over the past 10 years.
Collapse
Affiliation(s)
- Radomir Juza
- National Institute of Mental Health, Klecany, Czech Republic
- Department of Chemistry, University of Hradec Kralove, Hradec Kralove, Czech Republic
| | - Premysl Vlcek
- National Institute of Mental Health, Klecany, Czech Republic
- Third Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Eva Mezeiova
- Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| | - Kamil Musilek
- Department of Chemistry, University of Hradec Kralove, Hradec Kralove, Czech Republic
- Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| | - Ondrej Soukup
- Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| | - Jan Korabecny
- National Institute of Mental Health, Klecany, Czech Republic
- Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| |
Collapse
|
3
|
Toft-Bertelsen TL, Yarishkin O, Redmon S, Phuong TTT, Križaj D, MacAulay N. Volume sensing in the transient receptor potential vanilloid 4 ion channel is cell type-specific and mediated by an N-terminal volume-sensing domain. J Biol Chem 2019; 294:18421-18434. [PMID: 31619514 DOI: 10.1074/jbc.ra119.011187] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Revised: 10/11/2019] [Indexed: 12/29/2022] Open
Abstract
Many retinal diseases are associated with pathological cell swelling, but the underlying etiology remains to be established. A key component of the volume-sensitive machinery, the transient receptor potential vanilloid 4 (TRPV4) ion channel, may represent a sensor and transducer of cell swelling, but the molecular link between the swelling and TRPV4 activation is unresolved. Here, our results from experiments using electrophysiology, cell volumetric measurements, and fluorescence imaging conducted in murine retinal cells and Xenopus oocytes indicated that cell swelling in the physiological range activated TRPV4 in Müller glia and Xenopus oocytes, but required phospholipase A2 (PLA2) activity exclusively in Müller cells. Volume-dependent TRPV4 gating was independent of cytoskeletal rearrangements and phosphorylation. Our findings also revealed that TRPV4-mediated transduction of volume changes is dependent by its N terminus, more specifically by its distal-most part. We conclude that the volume sensitivity and function of TRPV4 in situ depend critically on its functional and cell type-specific interactions.
Collapse
Affiliation(s)
- Trine L Toft-Bertelsen
- Department of Neuroscience, University of Copenhagen, Blegdamsvej 3, Bldg. 24.6, 2200 Copenhagen N, Denmark
| | - Oleg Yarishkin
- Department of Ophthalmology and Visual Sciences, University of Utah School of Medicine, Salt Lake City, Utah 84132
| | - Sarah Redmon
- Department of Ophthalmology and Visual Sciences, University of Utah School of Medicine, Salt Lake City, Utah 84132
| | - Tam T T Phuong
- Department of Ophthalmology and Visual Sciences, University of Utah School of Medicine, Salt Lake City, Utah 84132
| | - David Križaj
- Department of Ophthalmology and Visual Sciences, University of Utah School of Medicine, Salt Lake City, Utah 84132.
| | - Nanna MacAulay
- Department of Neuroscience, University of Copenhagen, Blegdamsvej 3, Bldg. 24.6, 2200 Copenhagen N, Denmark.
| |
Collapse
|
4
|
Campos-Garcia L, Jimenez-Valdes RJ, Hernandez-Bello R, Palma-Nicolas J, Gonzalez GM, Sanchez-Gonzalez A. Candida albicans and non- albicans Isolates from Bloodstream Have Different Capacities to Induce Neutrophil Extracellular Traps. J Fungi (Basel) 2019; 5:jof5020028. [PMID: 30939757 PMCID: PMC6616947 DOI: 10.3390/jof5020028] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 03/27/2019] [Accepted: 03/28/2019] [Indexed: 12/21/2022] Open
Abstract
Neutrophils activated with pathogens or their products induce formation of extracellular traps (NETs), but if this constitutes a general response against all pathogenic species in a single genus or intrageneric differences exist remains unknown, yet this is of great importance for the establishment of effective treatments. To determine this, we analyzed neutrophil extracellular traps formation after the stimulation with bloodstream isolates from different Candida species (Candida albicans, C. tropicalis, C. parapsilosis, and C. glabrata), and found that each species has a different capacity to induce DNA extrusion, which is independent of their morphology (yeast or hyphae). We observed that phospholipase producer's strains and their secretion products were able to induce NETs, a property not observed with phospholipase deficient strains, with exception of some Candida glabrata sensu stricto isolates, which showed no NETs induction although they did show phospholipase production. To further analyze this, we extended our study to include Candida glabrata cryptic species (C. bracarensis and C. nivariensis) and no extracellular traps formation was observed. Here, we contribute to the understanding of how neutrophils initiate NETs, and we found that certain strains may have a differential capacity to trigger these structures, which may explain the high mortality of some isolates.
Collapse
Affiliation(s)
- Lizbeth Campos-Garcia
- Departamento de Microbiología, Facultad de Medicina, Universidad Autónoma de Nuevo León, Monterrey 64460, Mexico.
| | - Rocio Jimena Jimenez-Valdes
- Unidad Monterrey, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Vía del Conocimiento 201, Parque PIIT, Apodaca, Monterrey 66628, Mexico.
| | - Romel Hernandez-Bello
- Departamento de Microbiología, Facultad de Medicina, Universidad Autónoma de Nuevo León, Monterrey 64460, Mexico.
| | - Jose Palma-Nicolas
- Departamento de Microbiología, Facultad de Medicina, Universidad Autónoma de Nuevo León, Monterrey 64460, Mexico.
| | - Gloria Maria Gonzalez
- Departamento de Microbiología, Facultad de Medicina, Universidad Autónoma de Nuevo León, Monterrey 64460, Mexico.
| | - Alejandro Sanchez-Gonzalez
- Departamento de Microbiología, Facultad de Medicina, Universidad Autónoma de Nuevo León, Monterrey 64460, Mexico.
| |
Collapse
|
5
|
Elinder F, Liin SI. Actions and Mechanisms of Polyunsaturated Fatty Acids on Voltage-Gated Ion Channels. Front Physiol 2017; 8:43. [PMID: 28220076 PMCID: PMC5292575 DOI: 10.3389/fphys.2017.00043] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Accepted: 01/16/2017] [Indexed: 01/29/2023] Open
Abstract
Polyunsaturated fatty acids (PUFAs) act on most ion channels, thereby having significant physiological and pharmacological effects. In this review we summarize data from numerous PUFAs on voltage-gated ion channels containing one or several voltage-sensor domains, such as voltage-gated sodium (NaV), potassium (KV), calcium (CaV), and proton (HV) channels, as well as calcium-activated potassium (KCa), and transient receptor potential (TRP) channels. Some effects of fatty acids appear to be channel specific, whereas others seem to be more general. Common features for the fatty acids to act on the ion channels are at least two double bonds in cis geometry and a charged carboxyl group. In total we identify and label five different sites for the PUFAs. PUFA site 1: The intracellular cavity. Binding of PUFA reduces the current, sometimes as a time-dependent block, inducing an apparent inactivation. PUFA site 2: The extracellular entrance to the pore. Binding leads to a block of the channel. PUFA site 3: The intracellular gate. Binding to this site can bend the gate open and increase the current. PUFA site 4: The interface between the extracellular leaflet of the lipid bilayer and the voltage-sensor domain. Binding to this site leads to an opening of the channel via an electrostatic attraction between the negatively charged PUFA and the positively charged voltage sensor. PUFA site 5: The interface between the extracellular leaflet of the lipid bilayer and the pore domain. Binding to this site affects slow inactivation. This mapping of functional PUFA sites can form the basis for physiological and pharmacological modifications of voltage-gated ion channels.
Collapse
Affiliation(s)
- Fredrik Elinder
- Department of Clinical and Experimental Medicine, Linköping University Linköping, Sweden
| | - Sara I Liin
- Department of Clinical and Experimental Medicine, Linköping University Linköping, Sweden
| |
Collapse
|
6
|
Terhag J, Cavara NA, Hollmann M. Cave Canalem: How endogenous ion channels may interfere with heterologous expression in Xenopus oocytes. Methods 2010; 51:66-74. [DOI: 10.1016/j.ymeth.2010.01.034] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Revised: 01/26/2010] [Accepted: 01/27/2010] [Indexed: 10/19/2022] Open
|
7
|
Sobczak K, Bangel-Ruland N, Leier G, Weber WM. Endogenous transport systems in the Xenopus laevis oocyte plasma membrane. Methods 2009; 51:183-9. [PMID: 19963061 DOI: 10.1016/j.ymeth.2009.12.001] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Revised: 12/02/2009] [Accepted: 12/02/2009] [Indexed: 11/15/2022] Open
Abstract
Oocytes of the South African clawed frog Xenopus laevis are widely used as a heterologous expression system for the characterization of transport systems such as passive and active membrane transporters, receptors and a whole plethora of other membrane proteins originally derived from animal or plant tissues. The large size of the oocytes and the high degree of expression of exogenous mRNA or cDNA makes them an optimal tool, when compared with other expression systems such as yeast, Escherichia coli or eukaryotic cell lines, for the expression and functional characterization of membrane proteins. This easy to handle expression system is becoming increasingly attractive for pharmacological research. Commercially available automated systems that microinject mRNA into the oocytes and perform electrophysiological measurements fully automatically allow for a mass screening of new computer designed drugs to target membrane transport proteins. Yet, the oocytes possess a large variety of endogenous membrane transporters and it is absolutely mandatory to distinguish the endogenous transporters from the heterologous, expressed transport systems. Here, we review briefly the endogenous membrane transport systems of the oocytes.
Collapse
Affiliation(s)
- Katja Sobczak
- Institute of Animal Physiology, Westfalian Wilhelms-University, Hindenburgplatz 55, Muenster, Germany
| | | | | | | |
Collapse
|
8
|
Shimizu T, Okada S, Yamaguchi-Shima N, Yokotani K. Brain phospholipase C–diacylglycerol lipase pathway is involved in vasopressin-induced release of noradrenaline and adrenaline from adrenal medulla in rats. Eur J Pharmacol 2004; 499:99-105. [PMID: 15363956 DOI: 10.1016/j.ejphar.2004.07.087] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2004] [Revised: 07/12/2004] [Accepted: 07/15/2004] [Indexed: 02/02/2023]
Abstract
Recently, we reported that intracerebroventricularly (i.c.v.) administered arginine-vasopressin evokes the release of noradrenaline and adrenaline from adrenal medulla by brain thromboxane A2-mediated mechanisms in rats. These results suggest the involvement of brain arachidonic acid in the vasopressin-induced activation of the central adrenomedullary outflow. Arachidonic acid is released mainly by two pathways: phospholipase A2 (PLA2)-dependent pathway; phospholipase C (PLC)- and diacylglycerol lipase-dependent pathway. In the present study, therefore, we attempted to identify which pathway is involved in the vasopressin-induced release of both catecholamines from adrenal medulla using urethane-anesthetized rats. Vasopressin (0.2 nmol/animal, i.c.v.)-induced elevation of plasma noradrenaline and adrenaline was dose-dependently reduced by neomycin [0.28 and 0.55 micromol (250 and 500 microg)/animal, i.c.v.] and 1-[6-[[(17beta)-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione (U-73122) [5 and 10 nmol (2.3 and 4.6 microg)/animal, i.c.v.] (inhibitors of PLC), and also by 1,6-bis(cyclohexyloximinocarbonylamino)hexane (RHC-80267) [1.3 and 2.6 micromol (500 and 1000 microg)/animal, i.c.v.] (an inhibitor of diacylglycerol lipase). On the other hand, mepacrine [1.1 and 2.2 micromol (500 and 1000 microg)/animal, i.c.v.] (an inhibitor of PLA2) was largely ineffective on the vasopressin-induced elevation of plasma catecholamines. These results suggest that vasopressin evokes the release of noradrenaline and adrenaline from adrenal medulla by the brain PLC- and diacylglycerol lipase-dependent mechanisms in rats.
Collapse
Affiliation(s)
- Takahiro Shimizu
- Department of Neuropharmacology, Program of Neural Integration, Kochi Medical School, Kochi University, Nankoku, Kochi 783-8505, Japan
| | | | | | | |
Collapse
|
9
|
Okada S, Shimizu T, Yokotani K. Brain phospholipase C and diacylglycerol lipase are involved in corticotropin-releasing hormone-induced sympatho-adrenomedullary outflow in rats. Eur J Pharmacol 2003; 475:49-54. [PMID: 12954358 DOI: 10.1016/s0014-2999(03)02148-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previously, we reported that the elevation of plasma noradrenaline and adrenaline induced by intracerebroventricularly (i.c.v.) administered corticotropin-releasing hormone (CRH) was abolished by i.c.v. administered indomethacin, an inhibitor of cyclooxygenase, in rats [Yokotani et al., Eur. J. Pharmacol. 419, 183-189, 2001]. The result suggests the involvement of active metabolites of brain arachidonic acid in the CRH-induced activation of the central sympatho-adrenomedullary outflow. Arachidonic acid is released mainly by two different pathways: phospholipase A2-dependent pathway; phospholipase C- and diacylglycerol lipase-dependent pathway. In the present study, therefore, we tried to identify which pathway is involved in the CRH-induced elevation of plasma catecholamines in urethane-anesthetized rats. CRH (1.5 nmol/animal, i.c.v.)-induced elevation of plasma noradrenaline and adrenaline was abolished by neomycin [0.55 micromol (500 microg)/animal, i.c.v.] and 1-(6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U-73122) [5 nmol (2.3 microg)/animal, i.c.v.] (inhibitors of phospholipase C), and also by 1,6-bis-(cyclohexyloximinocarbonylamino)-hexane (RHC-80267) [1.3 micromol (500 microg)/animal, i.c.v.] (an inhibitor of diacylglycerol lipase). On the other hand, mepacrine [1.1 micromol (500 microg)/animal, i.c.v.] (an inhibitor of phospholipase A2) and 1-(6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-2,5-pyrrolidinedione (U-73343) [5 nmol (2.3 microg)/animal, i.c.v.] (an inactive analog of U-73122) had no effect. These results suggest that CRH activates the central sympatho-adrenomedullary outflow by the brain phospholipase C- and diacylglycerol lipase-dependent mechanisms in rats.
Collapse
Affiliation(s)
- Shoshiro Okada
- Department of Neuropharmacology, Program of Neural Integration, Kochi Medical School, Nankoku, Kochi 783-8505, Japan
| | | | | |
Collapse
|
10
|
Shi LJ, Liu LA, Cheng XH, Wang CA. Decrease in acetylcholine-induced current by neomycin in PC12 cells. Arch Biochem Biophys 2002; 403:35-40. [PMID: 12061799 DOI: 10.1016/s0003-9861(02)00258-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The effects of neomycin, one of the aminoglycoside antibiotics, on the acetylcholine (ACh)-induced current (I(ACh)) were studied in pheochromocytoma cells by using the whole-cell clamp technique. The I(ACh) proved to be generated through neuronal nicotinic receptor. ACh (30 microM) induced an inward current at a holding potential of -80 mV. When cells were treated with neomycin (0.01-1 mM) and ACh (30 microM) simultaneously, an inhibitory effect of neomycin on the peak of I(ACh) was found. This effect was fast, reversible, and concentration dependent. Pretreatment with neomycin for 3-8 min had no effect on the inhibition of I(ACh) induced by neomycin. External application of 0.1 mM neomycin neither shifted the dose-response curve of the peak I(ACh) to the right (dissociation constant (K(d)) = 16.5 microM) nor affected its coefficient (1.8) but inhibited the curve amplitudes by approximately 33%. Stimulated protein kinase C activation by using an exogenous activator produced inhibition of I(ACh), while using protein kinase C inhibitor (PKCI 19-31) had no effect on the inhibition of I(ACh) induced by neomycin. These results suggest that neomycin has an inhibitory effect on I(ACh) without the involvement of phospholipase C. It indicates that neomycin binds to a specific site on the cell membrane, probably on the neuronal nicotinic receptor-coupled channel, and inhibits the I(ACh) in a noncompetitive manner, thus controlling the immediate catecholamine release from the sympathetic cells.
Collapse
Affiliation(s)
- Li-jun Shi
- Department of Physiology, Beijing Medical College of PLA, Beijing 100071, China.
| | | | | | | |
Collapse
|
11
|
Trotti D, Peng JB, Dunlop J, Hediger MA. Inhibition of the glutamate transporter EAAC1 expressed in Xenopus oocytes by phorbol esters. Brain Res 2001; 914:196-203. [PMID: 11578612 DOI: 10.1016/s0006-8993(01)02802-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Recent evidence indicates that second messengers and protein kinases regulate the activity and expression of glutamate transporters. The aim of the present study was to determine if direct activation of protein kinases C or A modulates the activity of the sodium-dependent glutamate transporter EAAC1. EAAC1 modulation was studied in cRNA-injected Xenopus oocytes by measuring [3H]L-glutamate uptake or glutamate-evoked uptake currents. We found that activation of PKA was ineffective, whereas treatment with the PKC agonist phorbol 12-myristate 13-acetate (PMA) caused a significant decrease in EAAC1 transport activity (IC(50)=44.7+/-12 nM). PMA-induced EAAC1 inhibition was PKC-mediated because the inhibition could be blocked by specific PKC inhibitors and incubation with the inactive 4alpha-phorbol-12,13-didecanoate (4alpha-PDD) did not affect EAAC1. Saturation studies of glutamate-evoked uptake currents showed that PMA-mediated inhibition was due to a decrease in I(max) with no change in K(m). PMA simultaneously decreased membrane capacitance (C(m)) and transport-associated current and increased cytosolic accumulation of EAAC1 protein, compared to control. These results suggest that PKC activation inhibits EAAC1 by promoting its retrieval from the plasma membrane. PMA also significantly decreased glutamate uptake in a Madin-Darby canine kidney (MDCK) cell line stably transfected with EAAC1 but enhanced EAAC1-mediated glutamate uptake in the rat C6 glioma cells, consistent with previous observations. Because activation of PKC by phorbol esters leads to opposite effects on EAAC1 activity in different culture models, we conclude that the PKC-mediated regulation of EAAC1 is cell-type specific.
Collapse
Affiliation(s)
- D Trotti
- Membrane Biology Program, Brigham & Women's Hospital, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, USA.
| | | | | | | |
Collapse
|
12
|
Brereton HM, Harland ML, Auld AM, Barritt GJ. Evidence that the TRP-1 protein is unlikely to account for store-operated Ca2+ inflow in Xenopus laevis oocytes. Mol Cell Biochem 2000; 214:63-74. [PMID: 11195791 DOI: 10.1023/a:1007193720930] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The role of the TRP-1 protein, an animal cell homologue of the Drosophila transient receptor potential Ca2+ channel, in store-operated Ca2+ inflow in Xenopus laevis oocytes was investigated. A strategy involving RT-PCR and 3' and 5' rapid amplification of cDNA ends (RACE) was used to confirm and extend previous knowledge of the nucleotide and predicted amino acid sequences of Xenopus TRP-1 (xTRP-1). The predicted amino acid sequence was used to prepare an anti-TRP-l polyclonal antibody which detected the endogenous oocyte xTRP-1 protein and the human TRPC-1 protein expressed in Xenopus oocytes. Ca2+ inflow (measured using fura-2) initiated by 3-deoxy-3-fluoroinositol 1,4,5-trisphosphate (InsP3F) or lysophosphatidic acid (LPA) was completely inhibited by low concentrations of lanthanides (IC50 = 0.5 microM), indicating that InsP3F and LPA principally activate store-operated Ca2+ channels (SOCs). Antisense cRNA or antisense oligodeoxynucleotides, based on different regions of the xTRP-1 cDNA sequence, when injected into Xenopus oocytes, did not inhibit InsP3F-, LPA- or thapsigargin-stimulated Ca2+ inflow. Oocytes expressing the hTRPC-1 protein, which is 96% similar to xTRP-1, exhibited no detectable enhancement of either basal or InsP3F-stimulated Ca2+ inflow and only a very small enhancement of LPA-stimulated Ca2+ in-flow compared with control oocytes. It is concluded that the endogenous xTRP-1 protein is unlikely to be responsible for Ca2+ inflow through the previously-characterised Ca2+ -specific SOCs which are found in Xenopus oocytes. It is considered that xTRP-1 is likely to be a receptor-activated non-selective cation channel such as the channel activated by maitotoxin.
Collapse
Affiliation(s)
- H M Brereton
- Department of Medical Biochemistry, School of Medicine, Flinders University, Adelaide, South Australia
| | | | | | | |
Collapse
|
13
|
Weber W. Ion currents of Xenopus laevis oocytes: state of the art. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1421:213-33. [PMID: 10518693 DOI: 10.1016/s0005-2736(99)00135-2] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- W Weber
- Laboratory of Physiology, K.U. Leuven, Campus Gasthuisberg, B-3000, Leuven, Belgium.
| |
Collapse
|
14
|
Bhardwaj SK, Sandhu SK, Sharma P, Kaur G. Impact of diabetes on CNS: role of signal transduction cascade. Brain Res Bull 1999; 49:155-62. [PMID: 10435778 DOI: 10.1016/s0361-9230(99)00047-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Diabetic neuropathy is the most common secondary complication of diabetes mellitus. Several pathogenetic factors have been proposed for diabetic neuropathy. The present investigation was undertaken to study different components of signal transduction from discrete brain regions from streptozotocin-induced diabetic rats. Rats were sacrificed after 1 and 3 months of induction of diabetes, and a control group was also studied in parallel to ascertain the specificity of diabetes-associated changes. Blood glucose level and protein content of discrete brain regions were also estimated. Signal transduction cascade components like protein kinase A, protein kinase C, cAMP, phospholipase C, phospholipase A2, diacylglycerol and inositol phosphate levels were assayed in control and diabetic groups of rats. Significant attenuation in phosphoinositide metabolism along with activation of protein kinase activities were observed. These findings provide evidence to suggest a mechanism linking changes in signal transduction cascade, which is observed in 1- and 3-month diabetic rats, which ultimately leads to development of diabetic neuropathy.
Collapse
Affiliation(s)
- S K Bhardwaj
- Department of Biotechnology, Guru Nanak Dev University, Amritsar, India
| | | | | | | |
Collapse
|
15
|
Abstract
An unusual inward current which is slowly elicited in the Xenopus oocyte membrane during sustained depolarization is reportedly carried by Na+. It is thought that Na+ selective channels are in some way induced to become voltage-sensitive by the depolarization. Earlier studies report that the induction process involves a phospholipase C and a protein kinase C as well as calcium ions. The present work investigated the origins of this calcium in the oocyte. We show that injection of the powerful Ca2+ chelator (BAPTA) in the oocyte, before induction of the Na+ channels, prevented the appearance of the Na+ current, confirming an important role for [Ca2+]i. However, in oocytes perfused with Ca2+ -free medium, induction of the channels could still be obtained, indicating that induction did not depend upon the entry of external Ca2+. Downmodulation of Ca2+ release from inositol 1,4,5-trisphosphate (InsP3)-sensitive stores with caffeine and with a low molecular weight heparin resulted in decreased or no Na+ currents. The results are discussed in terms of the contributions from other endogenous calcium-dependent conductances which can influence the Na+ current amplitudes and time courses. The results presented support the idea that intracellular Ca2+ increase principally due to Ca2+ released from InsP3-sensitive stores is needed by the enzyme systems to produce the depolarization-induced activation of the Na+ conductance in the Xenopus oocyte.
Collapse
Affiliation(s)
- G Charpentier
- Laboratoire de Neurobiologie Cellulaire, Université de Picardie, Faculté des Sciences, Amiens, France.
| | | |
Collapse
|