Tuning Protein Dynamics to Sense Rapid Endoplasmic‐Reticulum Calcium Dynamics
Xiaonan Deng, Xin‐Qiu Yao, Ken Berglund, Bin Dong, Daniel Ouedraogo, Mohammad A. Ghane, You Zhuo, Cheyenne McBean, Zheng Wei, Samer Gozem, Shan Ping Yu, Ling Wei, Ning Fang, Angela M. Mabb, Giovanni Gadda, Donald Hamelberg, Jenny J. Yang
Abstract
Abstract Multi‐scale calcium (Ca 2+ ) dynamics, exhibiting wide‐ranging temporal kinetics, constitutes a ubiquitous mode of signal transduction. We report a novel endoplasmic‐reticulum (ER)‐targeted Ca 2+ indicator, R‐CatchER, which showed superior kinetics in vitro ( k off ≥2×10 3 s −1 , k on ≥7×10 6 M −1 s −1 ) and in multiple cell types. R‐CatchER captured spatiotemporal ER Ca 2+ dynamics in neurons and hotspots at dendritic branchpoints, enabled the first report of ER Ca 2+ oscillations mediated by calcium sensing receptors (CaSRs), and revealed ER Ca 2+ ‐based functional cooperativity of CaSR. We elucidate the mechanism of R‐CatchER and propose a principle to rationally design genetically encoded Ca 2+ indicators with a single Ca 2+ ‐binding site and fast kinetics by tuning rapid fluorescent‐protein dynamics and the electrostatic potential around the chromophore. The design principle is supported by the development of G‐CatchER2, an upgrade of our previous (G‐)CatchER with improved dynamic range. Our work may facilitate protein design, visualizing Ca 2+ dynamics, and drug discovery.