Nuclear Ca(2+) signalling.

Ca(2+) signalling is important for controlling gene transcription. Changes of the cytosolic Ca(2+) (Ca(2+)) may promote migration of transcription factors or transcriptional regulators to the nucleus. Changes of the nucleoplasmic Ca(2+) (Ca(2+)) can also regulate directly gene expression. Ca(2+) may change by propagation of Ca(2+) changes through the nuclear envelope or by direct release of Ca(2+) inside the nucleus. In the last case nuclear and cytosolic signalling can be dissociated. Phosphatidylinositol bisphosphate, phospholipase C and cyclic ADP-ribosyl cyclase are present inside the nucleus. Inositol trisphosphate receptors (IP(3)R) and ryanodine receptors (RyR) have also been found in the nucleus and can be activated by agonists. Furthermore, nuclear location of the synthesizing enzymes and receptors may be atypical, not associated to the nuclear envelope or other membranes. The possible role of nuclear subdomains such as speckles, nucleoplasmic reticulum, multi-macromolecular complexes and nuclear nanovesicles is discussed.