title: Native α6β4* nicotinic receptors control exocytosis in human chromaffin cells of the adrenal gland.
abstract: In the present study, we have electrophysiologically characterized native nicotinic acetylcholine receptors (nAChRs) in human chromaffin cells of the adrenal gland as well as their contribution to the exocytotic process. α-Conotoxin AuIB blocked by 14 ± 1% the acetylcholine (ACh)-induced nicotinic current. α-Conotoxin MII (α-Ctx MII) exhibited an almost full blockade of the nicotinic current at nanomolar concentrations (IC(50)=21.6 nM). The α6*-preferring α-Ctx MII mutant analogs, α-Ctx MII[H9A,L15A] and α-Ctx MII[S4A,E11A,L15A], blocked nAChR currents with an IC(50) of 217.8 and 33 nM, respectively. These data reveal that nAChRs in these cells include the α6* subtype. The washout of the blockade exerted by α-conotoxin BuIA (α-Ctx BuIA; 1 μM) on ACh-evoked currents was slight and slow, arguing in favor of the presence of a β4 subunit in the nAChR composition. Exocytosis was almost fully blocked by 1 μM α-Ctx MII, its mutant analogs, or α-Ctx BuIA. Finally, the fluorescent analog Alexa Fluor 546-BuIA showed distinct staining in these cells. Our results reveal that α6β4* nAChRs are expressed and contribute to exocytosis in human chromaffin cells of the adrenal gland, the main source of adrenaline under stressful situations.
authors.affiliation: Departamento de Farmacología y Terapéutica, Universidad Autónoma de Madrid, Madrid, Spain. a.perez@uam.es
authors.forename: Alberto
authors.initials: A
authors.lastname: Pérez-Alvarez
authors.forename: Alicia
authors.initials: A
authors.lastname: Hernández-Vivanco
authors.forename: J Michael
authors.initials: JM
authors.lastname: McIntosh
authors.forename: Almudena
authors.initials: A
authors.lastname: Albillos
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000313:Adrenal Medulla / Q000502:physiology*; D002478:Cells, Cultured; D018679:Cholinergic Agonists / Q000494:pharmacology; D019439:Chromaffin Cells / Q000187:drug effects / Q000502:physiology*; D020916:Conotoxins / Q000494:pharmacology; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D005456:Fluorescent Dyes / Q000494:pharmacology; D006801:Humans; D018733:Nicotinic Antagonists / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011806:Quinolinium Compounds / Q000494:pharmacology; D011978:Receptors, Nicotinic / Q000502:physiology*
chemical_list: C481052:Alexa fluor 546; D018679:Cholinergic Agonists; D020916:Conotoxins; D005456:Fluorescent Dyes; D018733:Nicotinic Antagonists; D011806:Quinolinium Compounds; D011978:Receptors, Nicotinic; C427403:alpha(4)beta(4) nicotinic receptor; C098872:alpha-conotoxin MII; C115558:conotoxin AuIB; D000109:Acetylcholine