Intracellular signalling: Receptor-specific messenger oscillations

The cytosolic molecule inositol-1,4,5-trisphosphate (InsP3) acts as a messenger to link receptors at the cell surface with alterations in calcium concentration inside the cell, but it is not clear how production of InsP3 is related to the often-complex calcium response. Here we use a fluorescent biosensor to visualize InsP3 synthesis in individual cells in real time and show that this is periodically switched on and off in a receptor-specific manner. Our findings are consistent with intracellular calcium oscillations being generated by either fluctuating or sustained concentrations of InsP3, which may allow diversity of signalling through the same signal-transduction pathway.