L-type voltage-sensitive calcium channel activation stimulates gene expression by a serum response factor-dependent pathway

Calcium regulation of gene expression in neurons: the mode of entry matters

Ca2+ entry into neurons is one of the major effectors of stimulus-induced physiological change. Ca2+ can enter neurons through a number of different voltage-gated and ligand-gated channels. Depending on the route of entry, Ca2+ stimulates distinct intracellular signaling pathways, which activate different sets of genes, resulting in alternative physiological outcomes for the cell. These recent results suggest that the specific effect of a single biochemical second messenger can vary as a consequence of its route of entry into the cell.

L-type voltage-sensitive Ca2+ channel activation regulates c-fos transcription at multiple levels

A mechanism by which voltage-sensitive Ca2+ channel (VSCC) activation triggers c-fos transcription has been characterized. Ca2+ influx through VSCCs stimulates phosphorylation of the transcription factor cAMP response element-binding protein (CREB) on serine 133 leading to an increase in the formation of transcription complexes that can elongate through a transcription pause site within the c-fos gene. Ca(2+)-stimulated CREB serine 133 phosphorylation is mediated by a Ca(2+)-activated kinase and is not dependent on the cAMP-dependent protein kinase (PKA). While necessary for c-fos transcriptional induction following VSCC opening, CREB serine 133 phosphorylation is not sufficient for transcriptional activation. A second, PKA-dependent event is required. Following induction, c-fos transcription is rapidly down-regulated. Dephosphorylation of CREB serine 133 parallels and likely mediates the transcriptional shut-off event. These results suggest that the phosphorylation and dephosphorylation of CREB controls its ability to regulate transcription in membrane-depolarized cells and that multiple pathways contribute to Ca(2+)-activated gene expression.