The beta1-adrenergic receptor (beta1AR) is a G protein-coupled receptor that mediates many of the physiological effects of adrenaline and noradrenaline. Little is known, however, about the molecular mechanisms of beta1AR targeting and regulation in cells. This project aims to study the interaction between the beta1tAR and MAGI-2, a previously-unknown intracellular beta1AR binding partner that associates with the beta1AR carboxyl-terminus via a high-affinity PDZ domain-mediated interaction. The functional significance of the beta1AR/MAGI-2 association is completely unknown. MAGI-2 may be either a scaffolding protein important for subcellular localization of the beta1AR, a regulatory protein that modulates receptor G protein coupling, or a signaling intermediate that couples the beta1AR to diverse intracellular signaling pathways. These possibilities will be explored with a combination of in vitro and cellular experiments. The in vitro experiments will determine the specificity of the beta1AR/MAGI-2 interaction and the potential ability of MAGI-2 to facilitate the formation of complexes between the beta1AR and other proteins. The cellular experiments will focus on the ability of MAGI-2 to regulate the subcellular distribution of the beta1AR and/or to alter beta1AR signaling to effectors such as adenylyl cyclase and MAP kinase. Furthermore, immunostaining of MAGI-2 and beta1AR in primary neuronal cultures and in brain sections will be examined in order to determine how well the two proteins co-localize in native tissues. These studies will provide mechanistic insight into localization and regulation of the beta1AR, a receptor that is a common target for therapeutics used in the treatment of heart disease and other disorders.
