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Hoshino J, Suwabe T, Sumida K, Mise K, Hayami N, Kawada M, Imafuku A, Hiramatsu R, Hasegawa E, Sawa N, Ubara Y, Takaichi K, Yamamoto J, Ishikawa Y, Nakagaki T, Shibazaki S, Nishio S, Atsumi T, Westland R, Verbitsky M, Vukojevic K, Perry BJ, Fasel DA, Zwijnenburg PJG, Gille JJP, Bokenkamp A, D'Agati VD, Gharavi AG, Schreuder MF, Van Wijk JAE, Sanna-Cherchi S, Rodriguez D, Riwanto M, Edenhofer I, Segerer S, Wuthrich RP, Kapoor S, Raaijmakers AMJ, Mekahli D, Van Dyck M, Corveleyn A, Allegaert K, Deviendt K, Kuypers D, Claes K, Levtchenko EN. CYSTIC DISEASE AND CILIOPATHIES. Nephrol Dial Transplant 2014. [DOI: 10.1093/ndt/gfu108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Liu X, Cheng R, Ye X, Verbitsky M, Kisselev S, Mejia-Santana H, Louis E, Cote L, Andrews H, Waters C, Ford B, Fahn S, Marder K, Lee J, Clark L. Increased Rate of Sporadic and Recurrent Rare Genic Copy Number Variants in Parkinson's Disease Among Ashkenazi Jews. Mol Genet Genomic Med 2013; 1:142-154. [PMID: 24073418 PMCID: PMC3782064 DOI: 10.1002/mgg3.18] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
To date, only one genome-wide study has assessed the contribution of copy number variants (CNVs) to Parkinson's disease (PD). We conducted a genome-wide scan for CNVs in a case–control dataset of Ashkenazi Jewish (AJ) origin (268 PD cases and 178 controls). Using high-confidence CNVs, we examined the global genome wide burden of large (≥100 kb) and rare (≤1% in the dataset) CNVs between cases and controls. A total of 986 such CNVs were observed in our dataset of 432 subjects. Overall global burden analyses did not reveal significant differences between cases and controls in CNV rate, distribution of deletions or duplications or number of genes affected by CNVs. Overall deletions (total CNV size and ≥2× frequency) were found 1.4 times more often in cases than in controls (P = 0.019). The large CNVs (≥500 kb) were also significantly associated with PD (P = 0.046, 1.24-fold higher in cases than in controls). Global burden was elevated for rare CNV regions. Specifically, for OVOS2 on Chr12p11.21, CNVs were observed only in PD cases (n = 7) but not in controls (P = 0.028) and this was experimentally validated. A total of 81 PD cases carried a rare genic CNV that was absent in controls. Ingenuity pathway analysis (IPA) identified ATXN3, FBXW7, CHCHD3, HSF1, KLC1, and MBD3 in the same disease pathway with known PD genes.
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Affiliation(s)
- X Liu
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain, College of Physicians and Surgeons, Columbia University, New York, NY, USA
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Alcalay R, Rosado L, Mejia-Santana H, Orbe-Reilly M, Caccappolo E, Tang M, Ruiz D, Ross B, Verbitsky M, Kisselev S, Louis E, Comella C, Colcher A, Jennings D, Nance M, Bressman S, Scott W, Tanner C, Andrews H, Waters C, Fahn S, Cote L, Frucht S, Ford B, Rezak M, Novak K, Friedman J, Pfeiffer R, Marsh L, Hiner B, Siderowf A, Payami H, Molho E, Nutt J, Factor S, Ottman R, Clark L, Marder K. Clinical and Genetic Characteristics of Participants with Juvenile PD: The CORE-PD Study (IN10-2.001). Neurology 2012. [DOI: 10.1212/wnl.78.1_meetingabstracts.in10-2.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Alcalay R, Rosado L, Mejia-Santana H, Orbe-Reilly M, Caccappolo E, Tang M, Ruiz D, Ross B, Verbitsky M, Kisselev S, Louis E, Comella C, Colcher A, Jennings D, Nance M, Bressman S, Scott W, Tanner C, Andrews H, Waters C, Fahn S, Cote L, Frucht S, Ford B, Rezak M, Novak K, Friedman J, Pfeiffer R, Marsh L, Hiner B, Siderowf A, Payami H, Molho E, Nutt J, Factor S, Ottman R, Clark L, Marder K. Clinical and Genetic Characteristics of Participants with Juvenile PD: The CORE-PD Study (S42.002). Neurology 2012. [DOI: 10.1212/wnl.78.1_meetingabstracts.s42.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Caccappolo E, Alcalay R, Marder K, Tang M, Rosado L, Mejia-Santana H, Ruiz D, Orbe-Reilly M, Ross B, Verbitsky M, Kisselev S, Louis E, Colcher A, Comella C, Siderowf A, Jennings D, Nance M, Bressman S, Scott W, Tanner C, Mickel S, Waters C, Fahn S, Cote L, Frucht S, Ford B, Rezak M, Friedman J, Marsh L, Hiner B, Payami H, Molho E, Ottman R, Clark L. The Effect of Parkin Mutation Status on Cognitive Functioning in EOPD Patients with Long Disease Duration: The CORE-PD Study (PD7.008). Neurology 2012. [DOI: 10.1212/wnl.78.1_meetingabstracts.pd7.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Marder K, Tang MX, Alcalay R, Rosado L, Mejia-Santana H, Caccappolo E, Ruiz D, Orbe-Reilly M, Ross B, Louis E, Comella C, Colcher A, Siderowf A, Jennings D, Nance M, Rezak M, Novak K, Friedman J, Pfeiffer R, Marsh L, Hiner B, Payami H, Molho E, Factor S, Bressman S, Scott W, Tanner C, Mickel S, Andrews H, Waters C, Cote L, Frucht S, Ford B, Verbitsky M, Kisselev S, Ottman R, Clark L. Estimating the Cumulative Risk of PD in Carriers of Parkin Mutations: The CORE-PD Study (PD4.007). Neurology 2012. [DOI: 10.1212/wnl.78.1_meetingabstracts.pd4.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Alcalay RN, Caccappolo E, Mejia-Santana H, Tang MX, Rosado L, Orbe Reilly M, Ruiz D, Ross B, Verbitsky M, Kisselev S, Louis E, Comella C, Colcher A, Jennings D, Nance M, Bressman S, Scott WK, Tanner C, Mickel S, Andrews H, Waters C, Fahn S, Cote L, Frucht S, Ford B, Rezak M, Novak K, Friedman JH, Pfeiffer R, Marsh L, Hiner B, Siderowf A, Payami H, Molho E, Factor S, Ottman R, Clark LN, Marder K. Cognitive performance of GBA mutation carriers with early-onset PD: the CORE-PD study. Neurology 2012; 78:1434-40. [PMID: 22442429 DOI: 10.1212/wnl.0b013e318253d54b] [Citation(s) in RCA: 191] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE To assess the cognitive phenotype of glucocerebrosidase (GBA) mutation carriers with early-onset Parkinson disease (PD). METHODS We administered a neuropsychological battery and the University of Pennsylvania Smell Identification Test (UPSIT) to participants in the CORE-PD study who were tested for mutations in PARKIN, LRRK2, and GBA. Participants included 33 GBA mutation carriers and 60 noncarriers of any genetic mutation. Primary analyses were performed on 26 GBA heterozygous mutation carriers without additional mutations and 39 age- and PD duration-matched noncarriers. Five cognitive domains, psychomotor speed, attention, memory, visuospatial function, and executive function, were created from transformed z scores of individual neuropsychological tests. Clinical diagnoses (normal, mild cognitive impairment [MCI], dementia) were assigned blind to genotype based on neuropsychological performance and functional impairment as assessed by the Clinical Dementia Rating (CDR) score. The association between GBA mutation status and neuropsychological performance, CDR, and clinical diagnoses was assessed. RESULTS Demographics, UPSIT, and Unified Parkinson's Disease Rating Scale-III performance did not differ between GBA carriers and noncarriers. GBA mutation carriers performed more poorly than noncarriers on the Mini-Mental State Examination (p = 0.035), and on the memory (p = 0.017) and visuospatial (p = 0.028) domains. The most prominent differences were observed in nonverbal memory performance (p < 0.001). Carriers were more likely to receive scores of 0.5 or higher on the CDR (p < 0.001), and a clinical diagnosis of either MCI or dementia (p = 0.004). CONCLUSION GBA mutation status may be an independent risk factor for cognitive impairment in patients with PD.
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Affiliation(s)
- R N Alcalay
- Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY, USA.
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Alcalay RN, Siderowf A, Ottman R, Caccappolo E, Mejia-Santana H, Tang MX, Rosado L, Louis E, Ruiz D, Waters C, Fahn S, Cote L, Frucht S, Ford B, Orbe-Reilly M, Ross B, Verbitsky M, Kisselev S, Comella C, Colcher A, Jennings D, Nance M, Bressman S, Scott WK, Tanner C, Mickel S, Rezak M, Novak KE, Friedman JH, Pfeiffer R, Marsh L, Hiner B, Clark LN, Marder K. Olfaction in Parkin heterozygotes and compound heterozygotes: the CORE-PD study. Neurology 2010; 76:319-26. [PMID: 21205674 DOI: 10.1212/wnl.0b013e31820882aa] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND While Parkinson disease (PD) is consistently associated with impaired olfaction, one study reported better olfaction among Parkin mutation carriers than noncarriers. Whether olfaction differs between Parkin mutation heterozygotes and carriers of 2 Parkin mutations (compound heterozygotes) is unknown. OBJECTIVE To assess the relationship between Parkin genotype and olfaction in PD probands and their unaffected relatives. METHODS We administered the University of Pennsylvania Smell Identification Test (UPSIT) to 44 probands in the Consortium on Risk for Early-Onset Parkinson Disease study with PD onset ≤50 years (10 Parkin mutation heterozygotes, 9 compound heterozygotes, 25 noncarriers) and 80 of their family members (18 heterozygotes, 2 compound heterozygotes, 60 noncarriers). In the probands, linear regression was used to assess the association between UPSIT score (outcome) and Parkin genotype (predictor), adjusting for covariates. Among family members without PD, we compared UPSIT performance in heterozygotes vs noncarriers using generalized estimating equations, adjusting for family membership, age, gender, and smoking. RESULTS Among probands with PD, compound heterozygotes had higher UPSIT scores (31.9) than heterozygotes (20.1) or noncarriers (19.9) (p < 0.001). These differences persisted after adjustment for age, gender, disease duration, and smoking. Among relatives without PD, UPSIT performance was similar in heterozygotes (32.5) vs noncarriers (32.4), and better than in heterozygotes with PD (p = 0.001). CONCLUSION Olfaction is significantly reduced among Parkin mutation heterozygotes with PD but not among their heterozygous relatives without PD. Compound heterozygotes with PD have olfaction within the normal range. Further research is required to assess whether these findings reflect different neuropathology in Parkin mutation heterozygotes and compound heterozygotes.
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Affiliation(s)
- R N Alcalay
- Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
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Lioudyno MI, Verbitsky M, Glowatzki E, Holt JC, Boulter J, Zadina JE, Elgoyhen AB, Guth PS. The alpha9/alpha10-containing nicotinic ACh receptor is directly modulated by opioid peptides, endomorphin-1, and dynorphin B, proposed efferent cotransmitters in the inner ear. Mol Cell Neurosci 2002; 20:695-711. [PMID: 12213449 DOI: 10.1006/mcne.2002.1150] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
UNLABELLED Opioid peptides have been detected in the auditory and vestibular efferent neurons where they colocalize with the major neurotransmitter, acetylcholine. We investigated the function of opioids to modulate neurotransmission mediated by hair cell's alpha9/alpha10-containing nicotinic acetylcholine receptors (alpha9/alpha10nAChRs). The endogenous opioid peptides, endomorphin-1 (mu agonist) and dynorphin B (kappa agonist), but not a delta agonist [D-Pen2,D-Pen-5]enkephalin, inhibited the acetylcholine-evoked currents in frog saccular hair cells and rat inner hair cells. This inhibition was noncompetitive, voltage-independent, and was accompanied by an acceleration of the rate of current decay. Selective mu- and kappa-opioid receptor antagonists did not block the inhibition, although partial reduction by naloxone was observed. All opioid antagonists tested also reduced the acetylcholine response. Endomorphin-1 and dynorphin B inhibited the acetylcholine-evoked currents in alpha9/alpha10-expressing Xenopus oocytes. Because oocytes lack opioid receptors, it provides strong evidence for the direct interaction of opioid peptides with alpha9/alpha10nAChR. CONCLUSION alpha9/alpha10nAChR is a target for modulation by endomorphin-1 and dynorphin B, efferent cotransmitters in the inner ear.
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MESH Headings
- Acetylcholine/pharmacology
- Animals
- Anura
- Cochlea/drug effects
- Cochlea/physiology
- Dynorphins/pharmacology
- Dynorphins/physiology
- Ear, Inner/physiology
- Electric Conductivity
- Endorphins/pharmacology
- Endorphins/physiology
- Enkephalin, D-Penicillamine (2,5)-/pharmacology
- Hair Cells, Auditory/drug effects
- Hair Cells, Auditory/physiology
- In Vitro Techniques
- Narcotic Antagonists
- Neurotransmitter Agents/physiology
- Oligopeptides/pharmacology
- Oligopeptides/physiology
- Oocytes/drug effects
- Oocytes/metabolism
- Protein Isoforms/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptors, Nicotinic/chemistry
- Receptors, Nicotinic/drug effects
- Receptors, Nicotinic/metabolism
- Receptors, Nicotinic/physiology
- Saccule and Utricle/cytology
- Saccule and Utricle/drug effects
- Saccule and Utricle/physiology
- Synapses/drug effects
- Synapses/physiology
- Xenopus laevis
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Affiliation(s)
- M I Lioudyno
- Department of Pharmacology, Tulane University, New Orleans, Louisiana 70112, USA.
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Lioudyno MI, Verbitsky M, Holt JC, Elgoyhen AB, Guth PS. Morphine inhibits an alpha9-acetylcholine nicotinic receptor-mediated response by a mechanism which does not involve opioid receptors. Hear Res 2000; 149:167-77. [PMID: 11033256 DOI: 10.1016/s0378-5955(00)00180-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Nicotinic acetylcholine (nACh) receptors are known to be targets for modulation by a number of substances, including the opiates. It is known that acetylcholine (ACh) coexists with opioid peptides in cochlear efferent neurons, and such a colocalization has been proposed for the vestibular system. In the present study we test the hypothesis that morphine, an opioid receptor agonist with a broad spectrum of selectivity, modulates alpha9nACh receptor-mediated responses in frog vestibular hair cells. Morphine dose-dependently and reversibly inhibited ACh-induced currents as recorded by the perforated patch-clamp method. In the presence of morphine the ACh dose-response curve was shifted to the right in a parallel fashion, suggesting a competitive interaction. However, naloxone did not antagonize the inhibition produced by morphine. To test the hypothesis that morphine could interact with the alpha9nACh receptor without the involvement of opioid receptors, experiments were performed using Xenopus laevis oocytes injected with the alpha9nACh receptor cRNA. The currents activated by ACh in Xenopus oocytes, a system that lacks opioid receptors, were also dose-dependently inhibited by morphine. We conclude that morphine inhibits the alpha9nACh receptor-mediated response in hair cells and Xenopus oocytes through a mechanism which does not involve opioid receptors but may be a direct block of the alpha9nACh receptor.
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Affiliation(s)
- M I Lioudyno
- Department of Pharmacology, Tulane University School of Medicine, New Orleans, LA 70112, USA.
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Abstract
In the present study, we report that the alpha9 nicotinic acetylcholine receptor (nAChR) expressed in Xenopus laevis oocytes is reversibly blocked by aminoglycoside antibiotics. The aminoglycosides tested blocked the alpha9 nAChR in a concentration-dependent manner with the following rank order of potency: neomycin>gentamicin>streptomycin>amikacin>kanamycin. The antagonistic effect of gentamicin was not overcome by increasing the concentration of acetylcholine (ACh), indicative of a non-competitive type of block. Blockage of ACh-evoked currents by gentamicin was found to be voltage-dependent, being more potent at hyperpolarized than at depolarized holding potentials. Furthermore, gentamicin blockage was dependent upon the extracellular Ca(2+) concentration, shown by the fact that increments in extracellular Ca(2+) significantly reduced the potency of this aminoglycoside to block the alpha9 nAChR. Possible mechanisms of blockage by the aminoglycosides are discussed. The present results suggest that the initial reversible actions of aminoglycosides at the organ of Corti, such as the elimination of the olivocochlear efferent function, are due in part to the interaction with the native alpha9-containing cholinergic receptor of the outer hair cells.
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Affiliation(s)
- C V Rothlin
- Instituto de Investigaciones en Ingeniería Genética, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Exactas y Naturales, Vuelta de Obligado 2490, Universidad de Buenos Aires, Argentina
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Abstract
The rat alpha9 nicotinic acetylcholine receptor (nAChR) was expressed in Xenopus laevis oocytes and tested for its sensitivity to a wide variety of cholinergic compounds. Acetylcholine (ACh), carbachol, choline and methylcarbachol elicited agonist-evoked currents, giving maximal or near maximal responses. Both the nicotinic agonist suberyldicholine as well as the muscarinic agonists McN-A-343 and methylfurtrethonium behaved as weak partial agonists of the receptor. Most classical cholinergic compounds tested, being either nicotinic (nicotine, epibatidine, cytisine, methyllycaconitine, mecamylamine, dihydro-beta-erythroidine), or muscarinic (muscarine, atropine, gallamine, pilocarpine, bethanechol) agonists and antagonists, blocked the recombinant alpha9 receptor. Block by nicotine, epibatidine, cytisine, methyllycaconitine and atropine was overcome at high ACh concentrations, suggesting a competitive type of block. The present results indicate that alpha9 displays mixed nicotinic-muscarinic features that resemble the ones described for the cholinergic receptor of cochlear outer hair cells (OHCs). We suggest that alpha9 contains the structural determinants responsible for the pharmacological properties of the native receptor.
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Affiliation(s)
- M Verbitsky
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Vuelta de Obligado 2490, 1428, Buenos Aires, Argentina
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Abstract
At the synapse between olivocochlear efferent fibers and outer hair cells (OHCs) of the cochlea, a non-classical ionotropic cholinergic receptor allows Ca(2+) entry into the hair cell, thus activating a Ca(2+)-sensitive K(+) current which hyperpolarizes the cell's membrane. In the mammalian ear, this leads to a reduction in basilar membrane motion, altering auditory nerve fiber activity and reducing the dynamic range of hearing. The alpha9 nicotinic acetylcholine receptor (nAChR) subunit mediates synaptic transmission between cholinergic olivocochlear fibers and OHCs. Given that Ca(2+) is a key player at this inhibitory synapse, we evaluated the permeability to Ca(2+) of the recombinant alpha9 receptor expressed in Xenopus laevis oocytes and the modulation of its activity by extracellular Ca(2+). Our results show that the alpha9 receptor is highly permeable to Ca(2+) and that this cation potently blocks monovalent currents through this channel (IC(50)=100 microM, at -70 mV) in a voltage-dependent manner. At a Ca(2+) concentration similar to that found in the perilymph bathing the base of the OHCs, approximately 90% of the Na(+) current through the alpha9 receptor is blocked, suggesting that one of the main functions of this channel could be to provide a pathway for Ca(2+) influx.
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Affiliation(s)
- E Katz
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Vuelta de Obligado 2490, Buenos Aires, Argentina
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Rothlin CV, Katz E, Verbitsky M, Elgoyhen AB. The alpha9 nicotinic acetylcholine receptor shares pharmacological properties with type A gamma-aminobutyric acid, glycine, and type 3 serotonin receptors. Mol Pharmacol 1999; 55:248-54. [PMID: 9927615 DOI: 10.1124/mol.55.2.248] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the present study, we provide evidence that the alpha9 nicotinic acetylcholine receptor (nAChR) shares pharmacological properties with members of the Cys-loop family of receptors. Thus, the type A gamma-aminobutyric acid receptor antagonist bicuculline, the glycinergic antagonist strychnine, and the type 3 serotonin receptor antagonist ICS-205,930 block ACh-evoked currents in alpha9-injected Xenopus laevis oocytes with the following rank order of potency: strychnine > ICS-205,930 > bicuculline. Block by antagonists was reflected in an increase in the acetylcholine (ACh) EC50 value, with no changes in agonist maximal response or Hill coefficient, which suggests a competitive type of block. Moreover, whereas neither gamma-aminobutyric acid nor glycine modified ACh-evoked currents, serotonin blocked responses to ACh in a concentration-dependent manner. The present results suggest that the alpha9 nAChR must conserve in its primary structure some residues responsible for ligand binding common to other Cys-loop receptors. In addition, it adds further evidence that the alpha9 nAChR and the cholinergic receptor present at the base of cochlear outer hair cells have similar pharmacological properties.
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Affiliation(s)
- C V Rothlin
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas-Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
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