title: Isoform-specific mechanisms of α3β4*-nicotinic acetylcholine receptor modulation by the prototoxin lynx1.
abstract: This study investigates-for the first time to our knowledge-the existence and mechanisms of functional interactions between the endogenous mammalian prototoxin, lynx1, and α3- and β4-subunit-containing human nicotinic acetylcholine receptors (α3β4*-nAChRs). Concatenated gene constructs were used to express precisely defined α3β4*-nAChR isoforms (α3β4)2β4-, (α3β4)2α3-, (α3β4)2α5(398D)-, and (α3β4)2α5(398N)-nAChR inXenopusoocytes. In the presence or absence of lynx1, α3β4*-nAChR agonist responses were recorded by using 2-electrode voltage clamp and single-channel electrophysiology, whereas radioimmunolabeling measured cell-surface expression. Lynx1 reduced (α3β4)2β4-nAChR function principally by lowering cell-surface expression, whereas single-channel effects were primarily responsible for reducing (α3β4)2α3-nAChR function [decreased unitary conductance (≥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 (α3β4)2α5-nAChR function that was mediated by lynx1. No effects were observed when α3β4*-nAChRs were coexpressed with mutated lynx1 (control). Lynx1 is expressed in the habenulopeduncular tract, where α3β4*-α5*-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 [α(-)-interface containing] by which prototoxins can modulate nAChR function.-George, A. A., Bloy, A., Miwa, J. M., Lindstrom, J. M., Lukas, R. J., Whiteaker, P. Isoform-specific mechanisms of α3β4*-nicotinic acetylcholine receptor modulation by the prototoxin lynx1.
authors.affiliation: Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA; andrew.george@dignityhealth.org.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: George
authors.affiliation: Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA.|Leeds Institute of Cancer and Pathology, St. James' University Hospital, Leeds, United Kingdom.
authors.forename: Abigail
authors.initials: A
authors.lastname: Bloy
authors.affiliation: Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania, USA.
authors.forename: Julie M
authors.initials: JM
authors.lastname: Miwa
authors.affiliation: Department of Neuroscience, University of Pennsylvania Medical School, Philadelphia, Pennsylvania, USA.
authors.forename: Jon M
authors.initials: JM
authors.lastname: Lindstrom
authors.affiliation: Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA.
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Lukas
authors.affiliation: Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Whiteaker
mesh_terms: D000200:Action Potentials; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology; D058851:GPI-Linked Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D011978:Receptors, Nicotinic / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014981:Xenopus
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D058851:GPI-Linked Proteins; C485626:LYNX1 protein, human; D020033:Protein Isoforms; D021122:Protein Subunits; D011978:Receptors, Nicotinic
keywords: GPI-linked proteins; TEVC; concatenated receptor subunits; neurotoxins; single-channel electrophysiology