Nicotinic acetylcholine (ACh) receptors (nAChRs) are prolific receptors found in the peripheral and central nervous system. Because these receptors can be activated by nicotine as well as their native ligand acetylcholine, they have been implicated in several health-related phenomena. Nicotine is the major addictive component of tobacco and chronic tobacco use (smoking) has been implicated in many types of cancer as well as heart disease. Other related phenomena include an inverse correlation between smoking and Parkinson's disease and the published observation that patients with autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) who smoke have fewer seizures. The nAChRs belong to the Cys-loop family of ionotropic receptors, which share a pentameric architecture arranged around a central ion permeable pore. Many distinct subunit combinations can form receptors;and these combinations have distinct pharmacology in two areas: responses to acute applications of nicotinic drugs, and to chronic or repeated applications. We have chosen to study receptors containing the 15 subunit (15* nAChRs) because genome-wide association and candidate gene studies have identified polymorphisms in the 15 gene that are linked to an increased risk for nicotine addiction, alcohol addiction, and lung cancer. Using high resolution fluorescent microscopy techniques including Fvrster resonance energy transfer (FRET) and total internal reflection fluorescence (TIRF) we are able to visualize the nAChR's life cycle from assembly to degradation, within living cells. We have proposed to use these methods to study the assembly of 15* nAChRs, to determine the subcellular trafficking and assembly of 15* nAChRs, and to measure the pharmacological differences between 1422 and 142215 receptors. This study will therefore determine the molecular and subcellular processes that may underlie the response to chronic or repeated nicotine exposure of cells containing 15* receptors.
Roughly 400,000 Americans and roughly 4,000,000 people worldwide die annually of the sequelae to nicotine dependence. This project attempts to explain nicotine dependence.