Cover

G protein-coupled receptors (GPCRs) exhibit a common seven-transmembrane α-helices structure and serve as universal cell surface proteins that transmit extracellular signals from a wide variety of hormones, neurotransmitters, and other chemical stimulis into cells. Ligand-activated GPCRs activate heterotrimeric Gαβγ proteins located on the cytoplasmic side of the cell membrane. The activated G proteins, in turn, regulate effector proteins and ion channels that modulate the flow of second messengers, such as cAMP. By using optical approaches in live cells, recent studies have revealed kinetics of activation and deactivation and rate-limiting steps along GPCR cascades of signal transduction and have linked receptor polymorphisms and drug selectivity. From the article in this issue by Vilardaga et al., pages 590–599.

The editors thank Dr. Ron Smith, Alcon Laboratories, Fort Worth, TX, for collaborating with the authors to create the figure on the cover.