Agonist-stimulated PLC activity has been known for some time to be dependent on intracellular Ca2+ (Eberhard and Holz 1988) and the availability of fluorescently labelled biosensors for the substrate (PIP2) and both products (DAG and IP3) of PLC allowed us directly to visualize the Ca2+-sensitivity of PLC activity in neuroblastoma cells. Here, HSPG2 is linked to neuroblastoma.