Excitation-Transcription Coupling in Parvalbumin-Positive Interneurons Employs a Novel CaM Kinase-Dependent Pathway Distinct from Excitatory Neurons

Properly functional CNS circuits depend on inhibitory interneurons that in turn rely upon activity-dependent gene expression for morphological development, connectivity, and excitatory-inhibitory coordination. Despite its importance, excitation-transcription coupling in inhibitory interneurons is poorly understood. We report that PV+ interneurons employ a novel CaMK-dependent pathway to trigger CREB phosphorylation and gene expression. As in excitatory neurons, voltage-gated Ca2+ influx through Ca(V)1 channels triggers CaM nuclear translocation via local Ca2+ signaling. However, PV+ interneurons are distinct in that nuclear signaling is mediated by gamma CaMKI, not gamma CaMKII. CREB phosphorylation also proceeds with slow, sigmoid kinetics, rate-limited by paucity of CaMKIV, protecting against saturation of phospho-CREB in the face of higher firing rates and bigger Ca2+ transients. Our findings support the generality of CaM shuttling to drive nuclear CaMK activity, and they are relevant to disease pathophysiology, insofar as dysfunction of PV+ interneurons and molecules underpinning their excitation-transcription coupling both relate to neuropsychiatric disease.