Isoform-Specific Mechanisms Of A3Î²4Âˆ—-Nicotinic Acetylcholine Receptor Modulation By The Prototoxin Lynx1
This study investigates - for the first time to our knowledge - the existence and mechanisms of functional interactions between the endogenous mammalian prototoxin, lynx1, and Î±3- and Î²4-subunit-containing human nicotinic acetylcholine receptors (Î±3Î²4âˆ—-nAChRs). Concatenated gene constructs were used to express precisely defined Î±3Î²4âˆ—-nAChR isoforms (Î±3Î²4)2Î²4-, (Î±3Î²4)2Î±3-, (Î±3Î²4)2Î±5(398D)-, and (Î±3Î²4)2a5(398N)-nAChR in Xenopus oocytes. In the presence or absence of lynx1, Î±3Î²4âˆ—-nAChR agonist responses were recorded by using 2-electrode voltage clamp and single-channel electrophysiology, whereas radioimmunolabeling measured cellsurface expression. Lynx1 reduced (Î±3Î²4)2Î²4-nAChR function principally by lowering cell-surface expression, whereas single-channel effects were primarily responsible for reducing (Î±3Î²4)2Î±3-nAChR function [decreased unitary conductance (â€¡50%), altered burst proportions (3-fold reduction in the proportion of long bursts), and enhanced closed dwell times (3- to 6-fold increase)]. Alterations in both cell-surface expression and single-channel properties accounted for the reduction in (Î±3Î²4)2Î±5-nAChR function that wasmediated by lynx1. No effects were observed when a3b4âˆ—-nAChRs were coexpressed with mutated lynx1 (control). Lynx1 is expressed in the habenulopeduncular tract, where Î±3Î²4âˆ—-Î±5âˆ—-nAChR subtypes are critical contributors to the balance between nicotine aversion and reward. This gives our findings a high likelihood of physiologic significance. The exquisite isoform selectivity of lynx1 interactions provides new insights into the mechanisms and allosteric sites [Î±(2)-interface containing] by which prototoxins canmodulatenAChRfunction. - George, A. A., Bloy, A.,Miwa, J. M., Lindstrom, J. M., Lukas, R. J., Whiteaker, P. Isoform-specific mechanisms of Î±3Î²4âˆ—-nicotinic acetylcholine receptor modulation by the prototoxin lynx1.
Digital Object Identifier (DOI)
George, Andrew A.; Bloy, Abigail; Miwa, Julie M.; Lindstrom, Jon M.; Lukas, Ronald J.; and Whiteaker, Paul, "Isoform-Specific Mechanisms Of A3Î²4Âˆ—-Nicotinic Acetylcholine Receptor Modulation By The Prototoxin Lynx1" (2017). Neurobiology. 243.