Multifaceted Regulation of Neuronal L-Type Ca2+ Channels by the N-Terminal Domain: from CaMKII Targeting to Nuclear Signaling

Abstract

Appropriate Ca2+ influx through the plasma membrane plays a key role in neuronal excitability and plasticity. Neuronal excitation activates voltage-gated L-type (CaV1.x) Ca2+ channels (LTCCs) that results in nuclear CREB phosphorylation and immediate early gene expression. Activation of this long-range pathway is critical for memory formation and requires recruitment of Ca2+/calmodulin-dependent protein kinase II (CaMKII) to the immediate vicinity of the LTCC via an unknown mechanism. Here, I showed that activated CaMKII strongly interacts with a novel binding motif in the N-terminal domain (NTD) of the CaV1.3 LTCC α1 subunit. Mutations in the CaV1.3 α1 subunit NTD or in the CaMKII catalytic domain that largely prevent the in vitro interaction interfere with excitation-transcription coupling in cultured hippocampal neurons. Furthermore, CaMKII/NTD interaction is also important for channel clustering and phosphorylation in vitro. In addition, I found that the CaV1.3 NTD interacts with the LTCC β2a subunit to regulate Ca2+-dependent inactivation of the channel. Lastly, I showed that the CaV1.3 NTD may be proteolyzed and that the isolated CaV1.3 NTD is targeted to the nucleus when over-expressed, regulating gene transcription and neuronal morphology. Taken together, data in this dissertation define a novel regulation motif within the neuronal LTCC that is critical in mediating channel signaling and regulating channel kinetics.