Role of the nuclear envelope in calcium signalling

The endoplasmic reticulum (ER) is the major Ca2+ store inside the cell. Its organisation in specialised subdomains allows the local delivery of Ca2+ to specific cell areas on stimulation. The nuclear envelope (NE), which is continuous with the ER, has a double role: it insulates the nucleoplasm from the cytoplasm and it stores Ca2+ around the nucleus. Furthermore, all the constituents of the signalling cascade leading to Ca2+ mobilisation are found in the NE; this allows the nuclear Ca2+ to be regulated autonomously. On the other hand, cytosolic Ca2+ transients can propagate within the nucleus via the nuclear pore complex. The variations in nuclear Ca2+ concentration are important for controlling gene transcription and progression in the cell cycle. Recent data suggest that invaginations of the NE modify the morphology of the nucleus and may affect Ca2+ dynamics in the nucleus and regulate transcriptional activity.