Native α6β4* nicotinic receptors control exocytosis in human chromaffin cells of the adrenal gland

In the present study, we have electro-physiologically characterized native nicotinic acetylcholine receptors (nAChRs) in human chromaffin cells of the adrenal gland as well as their contribution to the exocytotic process. alpha-Conotoxin AuIB blocked by 14 +/- 1% the acetylcholine (ACh)-induced nicotinic current. alpha-Conotoxin MII (alpha-Ctx MII) exhibited an almost full blockade of the nicotinic current at nanomolar concentrations (IC(50) = 21.6 nM). The alpha 6*-preferring alpha-Ctx MII mutant analogs, alpha-Ctx MII[H9A,L15A] and alpha-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 alpha 6* subtype. The washout of the blockade exerted by alpha-conotoxin BuIA (alpha-Ctx BuIA; 1 mu M) on ACh-evoked currents was slight and slow, arguing in favor of the presence of a beta 4 subunit in the nAChR composition. Exocytosis was almost fully blocked by 1 mu M alpha-Ctx MII, its mutant analogs, or alpha-Ctx BuIA. Finally, the fluorescent analog Alexa Fluor 546-BuIA showed distinct staining in these cells. Our results reveal that alpha 6 beta 4* nAChRs are expressed and contribute to exocytosis in human chromaffin cells of the adrenal gland, the main source of adrenaline under stressful situations.-Perez-Alvarez, A., Hernandez-Vivanco, A., McIntosh, J. M., Albillos, A. Native alpha 6 beta 4* nicotinic receptors control exocytosis in human chromaffin cells of the adrenal gland. FASEB J. 26, 346-354 (2012). www.fasebj.org