Rapid subcellular calcium responses and dynamics by calcium sensor G-CatchER

The precise spatiotemporal characteristics of subcellular calcium(Ca2+) transients are critical for the physiological processes. Here we report a green Ca2+ sensor called "G-CatchER(+)'' using a protein design to report rapid local ER Ca2+ dynamics with significantly improved folding properties. G-CatchER+ exhibits a superior Ca2+ on rate to G-CEPIA1er and has a Ca2+-induced fluorescence lifetimes increase. G-CatchER(+) also reports agonist/antagonist triggered Ca2+ dynamics in several cell types including primary neurons that are orchestrated by IP(3)Rs, RyRs, and SERCAs with an ability to differentiate expression. Upon localization to the lumen of the RyR channel (G-CatchER(+)-JP45), we report a rapid local Ca2+ release that is likely due to calsequestrin. Transgenic expression of G-CatchER(+) in Drosophila muscle demonstrates its utility as an in vivo reporter of stimulus-evoked SR local Ca2+ dynamics. G-CatchER(+) will be an invaluable tool to examine local ER/SR Ca2+ dynamics and facilitate drug development associated with ER dysfunction.