Unraveling the high- and low-sensitivity agonist responses of nicotinic acetylcholine receptors

TY - JOUR

T1 - Unraveling the high- and low-sensitivity agonist responses of nicotinic acetylcholine receptors

AU - Harpsøe, Kasper

AU - Ahring, Philip K

AU - Christensen, Jeppe K

AU - Jensen, Marianne L

AU - Peters, Dan

AU - Balle, Thomas

PY - 2011/7/27

Y1 - 2011/7/27

N2 - The neuronal α4β2 nicotinic acetylcholine receptors exist as two distinct subtypes, (α 4)2(β2)3 and (α 4)3(β2)2, and biphasic responses to acetylcholine and other agonists have been ascribed previously to coexistence of these two receptor subtypes. We offer a novel and radical explanation for the observation of two distinct agonist sensitivities. Using different expression ratios of mammalian α4 and β2 subunits and concatenated constructs, we demonstrate that a biphasic response is an intrinsic functional property of the (α4)3(β2)2 receptor. In addition to two high-sensitivity sites at α4β2 interfaces, the (α4)3(β2)2 receptor contains a third low-sensitivity agonist binding site in the a4a4 interface. Occupation of this site is required for full activation and is responsible for the widened dynamic response range of this receptor subtype. By site-directed mutagenesis, we show that three residues, which differ between the α4β2 and α4 α4 sites, control agonist sensitivity. The results presented here provide a basic insight into the function of pentameric ligand-gated ion channels, which enables modulation of the receptors with hitherto unseen precision; it becomes possible to rationally design therapeutics targeting subpopulations of specific receptor subtypes.

AB - The neuronal α4β2 nicotinic acetylcholine receptors exist as two distinct subtypes, (α 4)2(β2)3 and (α 4)3(β2)2, and biphasic responses to acetylcholine and other agonists have been ascribed previously to coexistence of these two receptor subtypes. We offer a novel and radical explanation for the observation of two distinct agonist sensitivities. Using different expression ratios of mammalian α4 and β2 subunits and concatenated constructs, we demonstrate that a biphasic response is an intrinsic functional property of the (α4)3(β2)2 receptor. In addition to two high-sensitivity sites at α4β2 interfaces, the (α4)3(β2)2 receptor contains a third low-sensitivity agonist binding site in the a4a4 interface. Occupation of this site is required for full activation and is responsible for the widened dynamic response range of this receptor subtype. By site-directed mutagenesis, we show that three residues, which differ between the α4β2 and α4 α4 sites, control agonist sensitivity. The results presented here provide a basic insight into the function of pentameric ligand-gated ion channels, which enables modulation of the receptors with hitherto unseen precision; it becomes possible to rationally design therapeutics targeting subpopulations of specific receptor subtypes.

KW - Former Faculty of Pharmaceutical Sciences

U2 - 10.1523/JNEUROSCI.1509-11.2011

DO - 10.1523/JNEUROSCI.1509-11.2011

M3 - Journal article

C2 - 21795528

SN - 0270-6474

VL - 31

SP - 10759

EP - 10766

JO - Journal of Neuroscience

JF - Journal of Neuroscience

IS - 30

ER -