title: Reporter mutation studies show that nicotinic acetylcholine receptor (nAChR) α5 Subunits and/or variants modulate function of α6*-nAChR.
abstract: To further the understanding of functional α6α5*-nicotinic acetylcholine receptors (nAChR; the asterisk (*) indicates known or possible presence of other subunits), we have heterologously expressed in oocytes different, mouse or human, nAChR subunit combinations. Coexpression with wild-type α5 subunits or chimeric α5/β3 subunits (in which the human α5 subunit N-terminal, extracellular domain is linked to the remaining domains of the human β3 subunit) almost completely abolishes the very small amount of function seen for α6β4*-nAChR and does not induce function of α6β2*-nAChR. Coexpression with human α5(V9)'(S) subunits bearing a valine 290 to serine mutation in the 9' position of the second transmembrane domain does not rescue the function of α6β4*-nAChR or induce function of α6β2*-nAChR. However, coexpression with mutant chimeric α5/β3(V9)'(S) subunits has a gain-of-function effect (higher functional expression and agonist sensitivity and spontaneous opening inhibited by mecamylamine) on α6β4*-nAChR. Moreover, N143D + M145V mutations in the α6 subunit N-terminal domain enable α5/β3(V9)'(S) subunits to have a gain-of-function effect on α6β2*-nAChR. nAChR containing chimeric α6/α3 subunits plus either β2 or β4 subunits have some function that is modulated in the presence of α5 or α5/β3 subunits. Coexpression with α5/β3(V9)'(S) subunits has a gain-of-function effect more pronounced than that in the presence of α5(V9)'(S) subunits. Gain-of-function effects are dependent, sometimes subtly, on the nature and apparently the extracellular, cytoplasmic, and/or transmembrane domain topology of partner subunits. These studies yield insight into assembly of functional α6α5*-nAChR and provide tools for development of α6*-nAChR-selective ligands that could be important in the treatment of nicotine dependence, and perhaps other neurological diseases.
authors.affiliation: Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona 85013.
authors.forename: Bhagirathi
authors.initials: B
authors.lastname: Dash
authors.affiliation: Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona 85013.
authors.forename: Yongchang
authors.initials: Y
authors.lastname: Chang
authors.affiliation: Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona 85013. Electronic address: rlukas@chw.edu.
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Lukas
mesh_terms: D000818:Animals; D003593:Cytoplasm / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004594:Electrophysiology / Q000379:methods; D005260:Female; D006801:Humans; D008024:Ligands; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D009538:Nicotine / Q000378:metabolism; D009865:Oocytes / Q000378:metabolism; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D011978:Receptors, Nicotinic / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D014982:Xenopus laevis
chemical_list: C447158:CHRNA5 protein, human; C470410:CHRNA6 protein, human; D018076:DNA, Complementary; D008024:Ligands; D009419:Nerve Tissue Proteins; D011978:Receptors, Nicotinic; D011993:Recombinant Fusion Proteins; D009538:Nicotine