High Selectivity of an α‑Conotoxin LvIA Analogue for α3β2 Nicotinic Acetylcholine Receptors Is Mediated by β2 Functionally Important Residues

The
α3β2 and α3β4 nicotinic acetylcholine
receptors (nAChRs) are widely expressed in the central and peripheral
nervous systems, playing critical roles in various physiological processes
and in such pathologies as addiction to nicotine and other drugs of
abuse. α-Conotoxin LvIA, which we previously isolated from Conus lividus, modestly discriminates α3β2
and α3β4 rat nAChRs exhibiting a ∼17-fold tighter
binding to the former. Here, alanine scanning resulted in two more
selective analogues [N9A]­LvIA and [D11A]­LvIA, the former having a
>2000-fold higher selectivity for α3β2. The determined
crystal structures of [N9A]­LvIA and [D11A]­LvIA bound to the acetylcholine-binding
protein (AChBP) were followed by homologous modeling of the complexes
with the α3β2 and α3β4 nAChRs and by receptor
mutagenesis, which revealed Phe106, Ser108, Ser113, and Ser168 residues
in the β2 subunit as essential for LvIA binding. These results
may be useful for the design of novel compounds of therapeutic potential
targeting α3β2 nAChRs.