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Mutations Linked to Autosomal Dominant Nocturnal Frontal Lobe Epilepsy Affect Allosteric Ca²⁺ Activation of the α4β2 Nicotinic Acetylcholine Receptor

Rodrigues-Pinguet, Nivalda O. and Pinguet, Thierry J. and Figl, Antonio and Lester, Henry A. and Cohen, Bruce N. (2005) Mutations Linked to Autosomal Dominant Nocturnal Frontal Lobe Epilepsy Affect Allosteric Ca²⁺ Activation of the α4β2 Nicotinic Acetylcholine Receptor. Molecular Pharmacology, 68 (2). pp. 487-501. ISSN 0026-895X. https://resolver.caltech.edu/CaltechAUTHORS:20200428-121436325

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Abstract

Extracellular Ca²⁺ robustly potentiates the acetylcholine response of α4β2 nicotinic receptors. Rat orthologs of five mutations linked to autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE)—α4(S252F), α4(S256L), α4(+L264), β2(V262L), and β2(V262M)—reduced 2 mM Ca²⁺ potentiation of the α4β2 1 mM acetylcholine response by 55 to 74%. To determine whether altered allosteric Ca²⁺ activation or enhanced Ca²⁺ block caused this reduction, we coexpressed the rat ADNFLE mutations with an α4 N-terminal mutation, α4(E180Q), that abolished α4β2 allosteric Ca²⁺ activation. In each case, Ca²⁺ inhibition of the double mutants was less than that expected from a Ca²⁺ blocking mechanism. In fact, the effects of Ca²⁺ on the ADNFLE mutations near the intracellular end of the M2 region—α4(S252F) and α4(S256L)—were consistent with a straightforward allosteric mechanism. In contrast, the effects of Ca²⁺ on the ADNFLE mutations near the extracellular end of the M2 region—α4(+L264)β2, β2(V262L), and β2(V262M)—were consistent with a mixed mechanism involving both altered allosteric activation and enhanced block. However, the effects of 2 mM Ca²⁺ on the α4β2, α4(+L264)β2, and α4β2(V262L) single-channel conductances, the effects of membrane potential on the β2(V262L)-mediated reduction in Ca²⁺ potentiation, and the effects of eliminating the negative charges in the extracellular ring on this reduction failed to provide any direct evidence of mutant-enhanced Ca²⁺ block. Moreover, analyses of the α4β2, α4(S256L), and α4(+L264) Ca²⁺ concentration-potentiation relations suggested that the ADNFLE mutations reduce Ca²⁺ potentiation of the α4β2 acetylcholine response by altering allosteric activation rather than by enhancing block.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1124/mol.105.011155DOIArticle
ORCID:
AuthorORCID
Pinguet, Thierry J.0000-0002-9994-6482
Lester, Henry A.0000-0002-5470-5255
Additional Information:© 2005 The American Society for Pharmacology and Experimental Therapeutics. Received January 18, 2005; accepted May 17, 2005. This work was supported by grants from the National Institute of Health (NS0438000 and NS011756, to B.N.C. and H.A.L., respectively and a minority supplement (NS0438000-04S1 to N.O.R.). Portions of this work were published previously by UMI publishers in a doctoral dissertation by N.O.R.
Funders:
Funding AgencyGrant Number
NIHNS0438000
NIHNS011756
NIHNS0438000-04S1
Issue or Number:2
Record Number:CaltechAUTHORS:20200428-121436325
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200428-121436325
Official Citation:Mutations Linked to Autosomal Dominant Nocturnal Frontal Lobe Epilepsy Affect Allosteric Ca2+ Activation of the α4β2 Nicotinic Acetylcholine Receptor. Nivalda O. Rodrigues-Pinguet, Thierry J. Pinguet, Antonio Figl, Henry A. Lester and Bruce N. Cohen. Molecular Pharmacology August 1, 2005, 68 (2) 487-501; DOI: https://doi.org/10.1124/mol.105.011155
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:102875
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:28 Apr 2020 19:37
Last Modified:24 Nov 2020 17:57

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