Amyloid-Î² (AÎ²) accumulation and aggregation are thought to contribute to the pathogenesis of Alzheimer's disease (AD). In AD, there is a selective decrease in the numbers of radioligand binding sites corresponding to the most abundant nicotinic acetylcholine receptor (nAChR) subtype, which contains human Î±4 and Î²2 subunits (hÎ±4Î²2-nAChR). However, the relationships between these phenomena are uncertain, and effects of AÎ² on hÎ±4Î²2-nAChR function have not been investigated in detail. We first confirmed expression of hÎ±4 and hÎ²2 subunits as messenger RNA in transfected, human SH-EP1 cells by reverse transcription-polymerase chain reaction and mRNA fluorescence in situ, hybridization analyses. Immunoprecipitation Western analyses confirmed Î±4 and Î²2 subunit protein expression and coassembly. Whole cell current recording demonstrated heterologous expression in SH-EP1-hÎ±4Î²2 cells of functional hÎ±4Î²2-nAChRs with characteristic responses to nicotinic agonists or antagonists. Nicotine-induced whole cell currents were suppressed by AÎ²1-42 in a dose-dependent manner. Functional inhibition was selective for AÎ²1-42compared with the functionally inactive, control peptide AÎ²40-1. AÎ²1-42-mediated inhibition of hÎ±4Î²2-nAChR function was non-competitive, voltage-independent, and use-independent. Pre-loading of cells with guanyl-5â€²-yl thiophosphate failed to prevent AÎ²1-42- induced inhibition, suggesting that down-regulation of hÎ±4Î²2-nAChR function by AÎ²1-42 is not mediated by nAChR intemalization. Sensitivity to AÎ²j_42 antagonism at 1 nM was evident for hÎ±4Î²2-nAChRs, but not for heterologously expressed human Î±7-nAChRs, although both nAChR subtypes were functionally inhibited by 100 nM AÎ²1-42, with the magnitude of functional block being higher for 100 nM AÎ²1-42 acting on hÎ±7-nAChRs. These findings suggest that hÎ±4Î²2-nAChRs are sensitive and perhaps pathophysiologically relevant targets for AÎ² neurotoxicity in AD.
Journal of Biological Chemistry
Digital Object Identifier (DOI)
Wu, Jie; Kuo, Yen Ping; George, Andrew A.; Xu, Lin; Hu, Jun; and Lukas, Ronald J., "Î²-Amyloid Directly Inhibits Human Î±4Î²3-Nicotinic Acetylcholine Receptors Heterologously Expressed In Human Sh-Ep1 Cells" (2004). Neurobiology. 75.