NFAT4 is expressed in primary astrocytes and activated by glutamate

Calcium signaling is a critical component of astrocyte activation but little information is available regarding the identity and function of transcriptional targets of calcium signaling in these cells. As a first step in elucidating the mechanisms that astrocytes use to regulate transcription in response to raised intracellular calcium concentrations, we have investigated expression and activation of the calcium activated transcription factors of the NFAT family. We report here that NFAT4 is expressed in U373 astrocytoma cells and in primary cultures of astrocytes. Treatment of U373 cells or primary astrocytes with the calcium ionophore A23187, or the neurotransmitter glutamate, leads to NFAT nuclear translocation and increased DNA binding to a NFAT consensus site through a cyclosporin A-sensitive process. These data suggest that NFAT4 functions as a calcium-responsive transcription factor in astrocytes.