Molecular Electrophysiology of Cloned AChR Channels expressed in Xenopus Oocytes

Abstract

At present, the nicotinic acetylcholine receptor (AChR) is the best studied ion channel protein. Extensive biochemical and structural studies were possible because of its abundance in the electric organs of the fish Torpedo and Electrophorus ¹, The AChR of the neuromuscular synapse has been studied from the beginnings of electrophysiology ^2,3, and it has served as a paradigm for the development and application of the patch clamp technique ^4–6, Recently, the primary sequences of all four subunits of the Torpedo AChR ^7–12, of five subunits including a novel ε subunit ¹⁷ of the calf AChR ^13–17, and of various AChR subunits from other species ^12,18–20 have been determined by the cloning and sequencing of cDNA. This has opened the way for detailed structural models ^21,22, and various aspects of AChR structure and function have been related to specific features of the protein sequence ²³. In this context, the electrophysiological study with both whole cell and patch clamp techniques of AChR channels expressed in Xenopus laevis oocytes following the microinjection of mRNA is emerging as a useful approach to the characterization of different types of native or genetically modified receptor-channel proteins.