alpha -Conotoxin AuIB Selectively Blocks alpha 3 beta 4 Nicotinic Acetylcholine Receptors and Nicotine-Evoked Norepinephrine Release

• Published in: The Journal of neuroscience 1998-11, Vol.18 (21), p.8571-8579
• Main Authors: Luo, S, Kulak, J M, Cartier, GE, Jacobsen, R B, Yoshikami, D, Olivera, B M, McIntosh, J M
• Format: Article
• Language: English
• ISSN: 0270-6474

Neuronal nicotinic acetylcholine receptors (nAChRs) with putative alpha 3 beta 4-subunits have been implicated in the mediation of signaling in various systems, including ganglionic transmission peripherally and nicotine-evoked neurotransmitter release centrally. However, progress in the characterization of these receptors has been hampered by a lack of alpha 3 beta 4-selective ligands. In this report, we describe the purification and characterization of an alpha 3 beta 4 nAChR antagonist, alpha -conotoxin AuIB, from the venom of the "court cone," Conus aulicus. We also describe the total chemical synthesis of this and two related peptides that were also isolated from the venom. alpha -Conotoxin AuIB blocks alpha 3 beta 4 nAChRs expressed in Xenopus oocytes with an IC sub(50) of 0.75 mu M, a k sub(on) of 1.4 x 10 super(6) min super(- 1) M super(-1), a k sub(off) of 0.48 min super(-1), and a K sub(d) of 0.5 mu M. Furthermore, alpha -conotoxin AuIB blocks the alpha 3 beta 4 receptor with >100-fold higher potency than other receptor subunit combinations, including alpha 2 beta 2, alpha 2 beta 4, alpha 3 beta 2, alpha 4 beta 2, alpha 4 beta 4, and alpha 1 beta 1 gamma delta . Thus, AuIB is a novel, selective probe for alpha 3 beta 4 nAChRs. AuIB (1-5 mu M) blocks 20-35% of the nicotine-stimulated norepinephrine release from rat hippocampal synaptosomes, whereas nicotine-evoked dopamine release from striatal synaptosomes is not affected. Conversely, the alpha 3 beta 2-specific alpha -conotoxin MII (100 nM) blocks 33% of striatal dopamine release but not hippocampal norepinephrine release. This suggests that in the respective systems, alpha 3 beta 4-containing nAChRs mediate norepinephrine release, whereas alpha 3 beta 2-containing receptors mediate dopamine release.