We constructed a series of chimeric neuronal nicotinic acetylcholine (ACh) receptor (nAChR) α subunits to map the location of amino acid residues that determine the pharmacological properties of these receptors. The α2 and α3 subunits form pharmacologically distinct nAChRs upon expression, in combination with the β2 subunit, in Xenopus oocytes. The α2β2 subunit combination is insensitive to the nicotinic antagonist neuronal bungarotoxin (NBT) and is much more sensitive to nicotine than to ACh. In contrast, the α3β2 subunit combination is potently inhibited by NBT and is much less sensitive to nicotine than to ACh. Chimeric subunits were constructed by replacing portions of α2 or α3 with the analogous portion of the other α subunit. Pharmacological analysis of receptors formed by these chimeric subunits, in combination with β2, revealed that amino acid residues involved in determining NBT sensitivity were located within sequence segments 84-121,121-181, and 195-215. Amino acid residues that determine agonist sensitivity were located within sequence segments 1-84 and 195-215. Within region 195-215, we used site-directed mutagenesis to demonstrate the importance of Gin-198 of α3 (proline in α2) in determining both the antagonist sensitivity and the agonist sensitivity of neuronal nAChRs.
|Number of pages||10|
|State||Published - Sep 1 1993|
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