Î±Conotoxin Arenatus Ib[V11Lv16D] Is A Potent And Selective Antagonist At Rat And Human Native Î±7 Nicotinic Acetylcholine Receptors
A recently developed Î±-conotoxin, Î±-conotoxin Arenatus IB-[V11l,V16D] (Î±-CtxArIB[V11L,V16D]), is a potent and selective competitive antagonist at rat recombinant Î±7 nicotinic acetylcholine receptors (nAChRs), making it an attractive probe for this receptor subtype. Î±7 nAChRs are potential therapeutic targets that are widely expressed in both neuronal and nonneuronal tissues, where they are implicated in a variety of functions. In this study, we evaluate this toxin at rat and human native nAChRs. Functional Î±7 nAChR responses were evoked by choline plus the allosteric potentiator PNU-120596 [1-(5-chloro-2,4-dimethoxy-phenyl)-3-(5- methyl-isoxazol-3-yl)-urea] in rat PC12 cells and human SH-SY5Y cells loaded with calcium indicators. Î±-CtxArIB[V11L,V16D] specifically inhibited Î±7 nAChR-mediated increases in Ca 2+ in PC12 cells. Responses to other stimuli, 5-I-A-85380 [5-iodo-3-(2(S)-azetidinylmethoxy)pyridine dihydrochloride], nicotine, or KCl, that did not activate Î±7 nAChRs were unaffected. Human Î±7 nAChRs were also sensitive to Î±-CtxArIB[V11L, V16D]; acetylcholine-evoked currents in Xenopus laevis oocytes expressing human Î±7 nAChRs were inhibited by Î±-CtxArIB[V11L,V16D] (IC 50 , 3.4 nM) in a slowly reversible manner, with full recovery taking 15 min. This is consistent with the time course of recovery from blockade of rat Î±7 nAChRs in PC12 cells. Î±-CtxArIB[V11L,V16D] inhibited human native Î±7 nAChRs in SHSY5Y cells, activated by either choline or AR-R17779 [(2)-spiro[1-azabicyclo[2.2.2]octane-3,59-oxazolidin]-29-one] plus PNU-120596. Rat brain Î±7 nAChRs contribute to dopamine release from striatal minces; Î±-CtxArIB[V11L,V16D] (300 nM) selectively inhibited choline-evoked dopamine release without affecting responses evoked by nicotine that activates heteromeric nAChRs. This study establishes that Î±-CtxArIB[V11L,V16D] selectively inhibits human and rat native Î±7 nAChRs with comparable potency, making this a potentially useful antagonist for investigating Î±7 nAChR functions. Copyright Â© 2008 by The American Society for Pharmacology and Experimental Therapeutics.
Journal of Pharmacology and Experimental Therapeutics
Digital Object Identifier (DOI)
Innocent, Neal; Livingstone, Phil D.; Hone, Arik; Kimura, Atsuko; Young, Tracey; Whiteaker, Paul; McIntosh, J. Michael; and Wonnacott, Susan, "Î±Conotoxin Arenatus Ib[V11Lv16D] Is A Potent And Selective Antagonist At Rat And Human Native Î±7 Nicotinic Acetylcholine Receptors" (2008). Neurobiology. 388.