Ion channels as reporters of membrane receptor function: Automated analysis in Xenopus oocytes

Abstract

G-protein-coupled receptors (GPCR) are the most widely used system of communication used by cells. They sense external signals and translate them into intracellular signals. The information is carried mechanically across the cell membrane, without perturbing its integrity. Agonist binding on the extracellular side causes a change in receptor conformation which propagates to the intracellular side and causes release of activated G-proteins, the first messengers of a variety of signaling cascades. Permitting access to powerful electrophysiological techniques, ion channels can be employed to monitor precisely the most proximal steps of GPCR signaling, receptor conformational changes, and G-protein release. The former is achieved by physical attachment of a potassium channel to the GPCR to create an Ion-Channel Coupled Receptor (ICCR). The latter is based on the use of G-protein-regulated potassium channels (GIRK). We describe here how these two systems may be used in the Xenopus oocyte heterologous system with a robotic system for increased throughput.