Received for publication October 21, 2005.
Revised March 15, 2006.
Accepted for publication March 21, 2006.

Untranslated Region Dependent Dependent Exclusive Expression of High-Sensitivity Subforms of 42 and 32 Nicotinic Acetylcholine Receptors

Abstract

42 nicotinic acetylcholine receptors are recognized as the principal nicotine binding site in brain. Recombinant 42 nAChR demonstrate biphasic concentration-response relationships with low- and high-EC₅₀ components. This study shows that untranslated regions (UTR) can influence expression of high-sensitivity subforms of 42 and & [alpha]32 nAChR. Oocytes injected with 4 and 2 RNA lacking UTR expressed biphasic concentration-response relationships for ACh with high- sensitivity EC₅₀ values of 0.5 to 2.5 µM (14-24% of the population) and low-sensitivity EC₅₀ values of 110-180 µM (76-86%). In contrast, message with UTR expressed exclusively the high-sensitivity 42 nAChR subform with an ACh EC₅₀ value of 2.2 µM. Additional studies revealed pharmacologic differences between high- and low-sensitivity 42 subforms. While the antagonists dihydro--erythroidine (IC₅₀ 3-6 nM) and methyllycaconitine (IC₅₀ 40-130 nM) were not selective between high-and low-sensitivity 42, chlorisondamine, mecamylamine and d-tubocurarine were, respectively, 100-, 8-, and 5- fold selective for the & [alpha]42 subform with low-sensitivity to ACh. Conversely, agonists that selectively activated the high- sensitivity 42 subform with respect to efficacy as well as potency were identified. Further, two of these agonists were shown to activate mouse brain 42 as well as the ferret high-sensitivity 42 expressed in Xenopus oocytes. Using UTR-containing RNA, exclusive expression of a novel high-sensitivity 32 nAChR was also achieved. These studies (a) provide further evidence for the existence of multiple subforms of 42 nAChR, (b) extend that to 32 nAChR, (c) demonstrate UTR influence on 2-containing nAChR properties, and (d) reveal compounds that interact with & [alpha]42 in a subform-selective manner.

Key words: Nicotinic cholinergic, Ion channel regulation

This article has been cited by other articles:

				B. Tu, Z. Gu, J.-x. Shen, P. W. Lamb, and J. L. Yakel Characterization of a Nicotine-Sensitive Neuronal Population in Rat Entorhinal Cortex J. Neurosci., August 19, 2009; 29(33): 10436 - 10448. [Abstract] [Full Text] [PDF]

				C. D. Son, F. J. Moss, B. N. Cohen, and H. A. Lester Nicotine Normalizes Intracellular Subunit Stoichiometry of Nicotinic Receptors Carrying Mutations Linked to Autosomal Dominant Nocturnal Frontal Lobe Epilepsy Mol. Pharmacol., May 1, 2009; 75(5): 1137 - 1148. [Abstract] [Full Text] [PDF]

				N. B. Fedorov, L. C. Benson, J. Graef, P. M. Lippiello, and M. Bencherif Differential Pharmacologies of Mecamylamine Enantiomers: Positive Allosteric Modulation and Noncompetitive Inhibition J. Pharmacol. Exp. Ther., February 1, 2009; 328(2): 525 - 532. [Abstract] [Full Text] [PDF]

				M. Moroni, R. Vijayan, A. Carbone, R. Zwart, P. C. Biggin, and I. Bermudez Non-Agonist-Binding Subunit Interfaces Confer Distinct Functional Signatures to the Alternate Stoichiometries of the {alpha}4{beta}2 Nicotinic Receptor: An {alpha}4-{alpha}4 Interface Is Required for Zn2+ Potentiation J. Neurosci., July 2, 2008; 28(27): 6884 - 6894. [Abstract] [Full Text] [PDF]

				A. Kuryatov, J. Onksen, and J. Lindstrom Roles of Accessory Subunits in {alpha}4{beta}2* Nicotinic Receptors Mol. Pharmacol., July 1, 2008; 74(1): 132 - 143. [Abstract] [Full Text] [PDF]

				C. Gotti, M. Moretti, N. M. Meinerz, F. Clementi, A. Gaimarri, A. C. Collins, and M. J. Marks Partial Deletion of the Nicotinic Cholinergic Receptor {alpha}4 or {beta}2 Subunit Genes Changes the Acetylcholine Sensitivity of Receptor-Mediated 86Rb+ Efflux in Cortex and Thalamus and Alters Relative Expression of {alpha}4 and {beta}2 Subunits Mol. Pharmacol., June 1, 2008; 73(6): 1796 - 1807. [Abstract] [Full Text] [PDF]

				R. Zwart, A. L. Carbone, M. Moroni, I. Bermudez, A. J. Mogg, E. A. Folly, L. M. Broad, A. C. Williams, D. Zhang, C. Ding, et al. Sazetidine-A Is a Potent and Selective Agonist at Native and Recombinant {alpha}4{beta}2 Nicotinic Acetylcholine Receptors Mol. Pharmacol., June 1, 2008; 73(6): 1838 - 1843. [Abstract] [Full Text] [PDF]

				R. M. Drenan, R. Nashmi, P. Imoukhuede, H. Just, S. McKinney, and H. A. Lester Subcellular Trafficking, Pentameric Assembly, and Subunit Stoichiometry of Neuronal Nicotinic Acetylcholine Receptors Containing Fluorescently Labeled {alpha}6 and 3 Subunits Mol. Pharmacol., January 1, 2008; 73(1): 27 - 41. [Abstract] [Full Text] [PDF]

				L. Tapia, A. Kuryatov, and J. Lindstrom Ca2+ Permeability of the ({alpha}4)3(beta2)2 Stoichiometry Greatly Exceeds That of ({alpha}4)2(beta2)3 Human Acetylcholine Receptors Mol. Pharmacol., March 1, 2007; 71(3): 769 - 776. [Abstract] [Full Text] [PDF]

				M. Moroni, R. Zwart, E. Sher, B. K. Cassels, and I. Bermudez {alpha}4beta2 Nicotinic Receptors with High and Low Acetylcholine Sensitivity: Pharmacology, Stoichiometry, and Sensitivity to Long-Term Exposure to Nicotine Mol. Pharmacol., August 1, 2006; 70(2): 755 - 768. [Abstract] [Full Text] [PDF]