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 IP₃Rs, 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.