Regulation of neuronal excitation–transcription coupling by Kv2.1-induced clustering of somatic L-type Ca(2+) channels at ER-PM junctions

In mammalian brain neurons, membrane depolarization leads to voltage-gated Ca(2+) channel-mediated Ca(2+) influx that triggers diverse cellular responses, including gene expression, in a process termed excitation–transcription coupling. Neuronal L-type Ca(2+) channels, which have prominent populations on the soma and distal dendrites of hippocampal neurons, play a privileged role in excitation–transcription coupling. The voltage-gated K(+) channel Kv2.1 organizes signaling complexes containing the L-type Ca(2+) channel Cav1.2 at somatic endoplasmic reticulum–plasma membrane junctions. This leads to enhanced clustering of Cav1.2 channels, increasing their activity. However, the downstream consequences of the Kv2.1-mediated regulation of Cav1.2 localization and function on excitation–transcription coupling are not known. Here, we have identified a region between residues 478 to 486 of Kv2.1’s C terminus that mediates the Kv2.1-dependent clustering of Cav1.2. By disrupting this Ca(2+) channel association domain with either mutations or with a cell-penetrating interfering peptide, we blocked the Kv2.1-mediated clustering of Cav1.2 at endoplasmic reticulum–plasma membrane junctions and the subsequent enhancement of its channel activity and somatic Ca(2+) signals without affecting the clustering of Kv2.1. These interventions abolished the depolarization-induced and L-type Ca(2+) channel-dependent phosphorylation of the transcription factor CREB and the subsequent expression of c-Fos in hippocampal neurons. Our findings support a model whereby the Kv2.1-Ca(2+) channel association domain-mediated clustering of Cav1.2 channels imparts a mechanism to control somatic Ca(2+) signals that couple neuronal excitation to gene expression.