Nuclear calcium signalling

The topic of nuclear Ca2+ signalling is beset by discrepant observations of substantial nuclear/cytoplasmic gradients. The reasons why some labs have recorded such gradients, whilst other workers see equilibration of Ca-cyt(2+) and Ca-nuc(2+) using the same cells and techniques, is unexplained. Furthermore, how such gradients could arise across the NE that possesses many highly-conductive NPCs is a mystery. Although nuclei may have the capacity to be autonomous signalling entities, with functional Ca2+ release channels and an inositide cycle, the balance of evidence suggests that Ca2+ release on the inner NE does not occur during physiological stimulation. Our work suggests that elementary Ca2+ release events originating in the cytoplasm can give rise to Ca-nuc(2+) signals without causing elevation of the bulk cytoplasm. Clearly, the many Ca2+ signalling mechanisms that may impinge on Ca-nuc(2+) will remain a topic of controversy and debate for some time.