Locating inositol 1,4,5-trisphosphate in the nucleus and neuronal dendrites with genetically encoded fluorescent indicators

Inositol 1,4,5-trisphosphate (InsP(3)) is a key second messenger in many cell types and also in distinct subcellular regions of single living cells; however, little is examined about the subcellular dynamics of InsP(3) in a variety of cell types. We have developed fluorescent indicators to locate InsP(3) dynamics in single living cells based on an intramolecular fluorescence resonance energy transfer. Our indicator has visualized InsP(3) dynamics in the cytoplasm of cultured cells and even in single thin dendrites of hippocampal neurons, which has been unseen previously. We have further localized the present indicator in the nucleus and pinpointed nuclear InsP(3) dynamics. The observation with our nuclear InsP(3) indicator has solved a question on nuclear propagation of InsP(3) from the cytoplasm and has drawn a conclusion that the nuclear InsP(3) dynamics synchronously occurs with cytosolic InsP(3) dynamics evoked by agonist stimulations. The present approach contributes to the understanding of when, where, and how InsP(3) is generated and removed in a variety of living cells.