Recording intracellular cAMP levels with EPAC-based FRET sensors by fluorescence lifetime imaging.

Eukaryotic cells use second messengers such as Ca(2+), IP3, cGMP, and cAMP to transduce extracellular signals like hormones, via membrane receptors to downstream cellular effectors. FRET-based sensors are ideal to visualize and measure these rapid changes of second messenger concentrations in time and place. Here, we describe the use of EPAC-based FRET sensors to measure cAMP with spatiotemporal resolution in cells by fluorescence lifetime imaging (FLIM).