Calcium Channels, Calmodulin and Nuclear CREB Signaling

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 DESCRIPTION (provided by applicant): Excitation-transcription (E-T) coupling is a process that converts the electrical or chemical activation of a cell to a signal conveyed to the nucleus. n this way, the expression of genes can be modulated in an activity-dependent manner. The neuronal remodeling that results is recognized to be necessary and important for long-term adaptive changes during neuronal development, learning and memory and drug addiction. The most scrutinized example of E-T coupling is Ca2+ signaling to the transcription factor CREB (cAMP response element-binding) protein via phosphorylation at Ser133. As an important source of Ca2+ influx, voltage-gated Ca2+ channels have been well studied for their biophysical and biochemical properties. Interestingly, in E-T coupling it seems that Ca2+ influxes through different Ca2+ channels can engage different signaling pathways to the nucleus. For example, CaV1 (also called L-type) channels enjoy a big advantage over CaV2 channels, even though CaV1 channels contribute only a minority of the overall Ca2+ entry in neurons. Our recent Cell paper uncovered that this disparity in potency can be explained by differences in how the two classes of Ca2+ channels employ local and global Ca2+ signaling. However, the 'private line' for the nanodomain advantage of CaV1 channels is unclear. Now we are poised to provide a detailed characterization of the critical question: what carries the long-distance signal from CaV1-anchored signaling complex to the nucleus? We have an answer: Ca2+/CaM translocation to the nucleus depends on a co-transporter that we now identify as γCaMKII. This shuttle gathers cytoplasmic Ca2+/CaM, sequestering it at the CaV1 channel before traveling to the nucleus under control of a nuclear localization signal. This signaling mechanism relies on γCaMKII, βCaMKII and CaN, signaling molecules that operate in the CaV1 nanodomain and also have been implicated in multiple neuropsychiatric diseases. This proposal focuses on understanding the cellular machinery of γCaMKII/CaM translocation and three specific aims are proposed. (1) Define the dynamics of Ca2+ signaling mechanisms that link CaV1 activity to nuclear CREB phosphorylation and CRE-dependent transcription. We will track γCaMKII translocation in real time and assess the impact of Ca2+/CaM delivered to the nucleus via this shuttle mechanism. (2) We will manipulate the γCaMKII pathway using genetic constructs in order to nail down the molecular components required for CREB phosphorylation. We will alter binding interactions and enzymatic actions involving CaM, βCaMKII, CaN, and PP2A at critical steps along the pathway. (3) Understand CaV1-dependent CaM shuttling in neocortical neurons and define distinct roles of nanodomain Ca2+ signaling and voltage gated conformational signaling for E-T coupling. Gaining a clearer picture of the linkage between CaV1 channels and CREB signaling will have a favorable impact on understanding how changes in gene expression alter the function of neurons in neural networks. Thus, the research is relevant both to basic cell biology and to disease states as diverse as addiction, autism and other neuropsychiatric diseases.