PT  - JOURNAL ARTICLE
AU  - Drew Everhart
AU  - Edward Reiller
AU  - Armen Mirzoian
AU  - J. Michael McIntosh
AU  - Arun Malhotra
AU  - Charles W. Luetje
TI  - Identification of Residues That Confer α-Conotoxin-PnIA Sensitivity on the α3 Subunit of Neuronal Nicotinic Acetylcholine Receptors
AID  - 10.1124/jpet.103.051656
DP  - 2003 Aug 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 664--670
VI  - 306
IP  - 2
4099  - http://jpet.aspetjournals.org/content/306/2/664.short
4100  - http://jpet.aspetjournals.org/content/306/2/664.full
SO  - J Pharmacol Exp Ther2003 Aug 01; 306
AB  - Neuronal nicotinic receptors composed of the α3 and β2 subunits are at least 1000-fold more sensitive to blockade by α-conotoxin-PnIA than are α2β2 receptors. A series of chimeric subunits, formed from portions of α2 and α3, were coexpressed with β2 in Xenopus oocytes and tested for toxin sensitivity. We found determinants of toxin sensitivity to be widely distributed in the extracellular domain of α3. Analysis of receptors formed by a series of mutant α3 subunits, in which residues that differ between α3 and α2 were changed from what occurs in α3 to what occurs in α2, allowed identification of three determinants of α-conotoxin-PnIA sensitivity: proline 182, isoleucine 188, and glutamine 198. Comparison with determinants of α-conotoxin-MII and κ-bungarotoxin sensitivity on the α3 subunit revealed overlapping, but distinct, arrays of determinants for each of these three toxins. When tested against an EC50 concentration of acetylcholine, the IC50 for α-conotoxin-PnIA blockade was 25 ± 4 nM for α3β2, 84 ± 7 nM for α3P182Tβ2, 700 ± 92 nM for α3I188Kβ2, and 870 ± 61 nM for α3Q198Pβ2. To examine the location of these residues within the receptor structure, we generated a homology model of the α3β2 receptor extracellular domain using the structure of the acetylcholine binding protein as a template. All three residues are located on the C-loop of the α3 subunit, with isoleucine 188 nearest the acetylcholine-binding pocket. The American Society for Pharmacology and Experimental Therapeutics