Assessing GPCR and G Protein Signaling to the Nucleus in Live Cells Using Fluorescent Biosensors

G protein-coupled receptor (GPCR) signaling cascades regulate a wide variety of cellular processes and feature prominently in many cardiovascular pathologies. As such they represent major drug targets and discovering novel aspects of GPCR signaling provide important opportunities to identify additional potential therapeutic approaches to reverse or prevent cardiac remodeling and failure. Monitoring cellular traffi cking of signaling components and specifi c protein kinase activities using fl uorescent biosensors has provided key insight into stress/GPCR-induced kinase signaling networks and their effect on cardiac gene expression. Herein we describe the protocols for the expression, visualization (by confocal microscopy), and interpretation of data obtained with such biosensors expressed in adult cardiomyocytes. Our focus is on the cellular traffi cking of class II histone deacetylases (i.e., HDAC5) and on the FRET sensor (Camui) for calmodulindependent protein kinase II (CaMKII).