G protein-coupled receptor regulation: The role of protein interactions and receptor trafficking

The superfamily of G protein-coupled receptors (GPCR) is the largest gene family in the human genome. GPCR-mediated signaling operates in every human cell, and about 50% of existing clinically useful drugs act through GPCR. Kinins are proinflammatory peptides that are rapidly produced extracellularly following pathological insults and tissue damage. These peptides act through two GPCR subtypes, B1 (B1R) and B2 (B2R), to elicit numerous inflammatory responses including vasodilatiation, increased vascular permeability, and pain. GPER1 (G protein-coupled estrogen receptor 1) has recently been suggested as a novel estrogen receptor. Much controversy surrounds this receptor regarding its subcellular localization and activation. The aim of the present thesis was to explore the role of receptor trafficking and protein-interactions in kinin receptor regulation, as well as studying the receptor trafficking and signaling of GPER1. B1R forms homo-oligomers, which is required for proper B1R maturation and cell-surface expression. Furthermore, the endopeptidase EP24.15 is able to degrade BK intracellularly and attenuate maximal B2R responsiveness without influencing the potency of BK. Finally, GPER1 is localized both intracellularly and on the cell surface, where it is subject to rapid, constitutive endocytosis. Estrogen was found to elevate the level of cAMP in mouse myotube C2C12 cells, in a GPER1-dependent manner, but it is still not clear whether estrogen is the true agonist for GPER1. Taken together, the present thesis demonstrates the importance of protein-protein interactions and trafficking for B1R, B2R, and GPER1 regulation and activity. Understanding these mechanisms will be of great benefit in drug development by presenting novel drug targets.