Calcium controls the transcription of its own transporters and channels indeveloping neurons

Calcium has now become important as a regulator of gene expression. Cerebel lar granule cells developing in culture undergo early apoptosis unless thei r calcium is permitted to increase, e.g., by depolarizing their plasma memb rane. The increase is kept within controlled limits by changing the pattern of transcription of calcium transporters: The IF, channel (but not the rya nodine channel) becomes strongly upregulated after some days in culture in a reaction which is controlled by calcineurin. Two plasma membrane calcium pumps (isoforms PMCA2 and PMCA3) also become strongly up-regulated after so me days; one (PMCA1) experiences instead a splicing switch which up-regulat es a truncated variant of the isoform. By contrast, one splicing variant of the isoform PMCA4 and one of the Na/Ca exchangers of the plasma membrane ( NCX2) become very rapidly down-regulated: Their down-regulation is also con trolled by calcineurin. The altered pattern of Ca2+ transporter expression is likely to reflect development-linked changes in the demands for calcium signaling in different domains of the neuronal cell. (C) 1999 Academic Pres s.