Nuclear Ca2+ signalling in cerebellar Purkinje neurons.

An increase in nuclear Ca(2+) concentration may activate nuclear Ca(2+)-sensitive proteins and thereby regulate gene transcription. Ca(2+) can enter the nucleus from the cytoplasm either through nuclear pores or less certainly by release from the nuclear envelope. Recent studies indicate that the nuclear membrane of cerebellar Purkinje, but not granule neurons, contains multiple inositol 1,4,5-trisphosphate receptors (InsP(3)Rs) localized to the inner nuclear membrane. These data suggest that the nuclear envelope in some neurons is a Ca(2+) store specialized to release Ca(2+) directly into the nucleoplasm and thereby to amplify Ca(2+) signals entering the nucleus from the cytoplasm or to generate nuclear Ca(2+) transients on its own. Here we review current data on the mechanisms of regulation of Ca(2+) in the cell nucleus with particular emphasis on cerebellar Purkinje neurons.