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 ?CaMKII. 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 ?CaMKII, ?CaMKII 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 ?CaMKII/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 ?CaMKII translocation in real time and assess the impact of Ca2+/CaM delivered to the nucleus via this shuttle mechanism. (2) We will manipulate the ?CaMKII 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, ?CaMKII, 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.
The ability to regulate gene expression in response to stimuli from the outside world is critical for the function of nearly all cell types in the body and plays crucial role in regulating the function of neurons and their assembly into functional networks. This project studies the process by which excitation of neurons by membrane depolarization couples via opening of specific types of calcium channel and activation of cell signaling machinery to transcription of genes in the cell nucleus. Research on basic excitable cell biology will advance our understanding of how cells remodel themselves in health and in diseases such as addiction and autism.
| Cohen, Samuel M; Suutari, Benjamin; He, Xingzhi et al. (2018) Calmodulin shuttling mediates cytonuclear signaling to trigger experience-dependent transcription and memory. Nat Commun 9:2451 |
| Mullins, Caitlin; Fishell, Gord; Tsien, Richard W (2016) Unifying Views of Autism Spectrum Disorders: A Consideration of Autoregulatory Feedback Loops. Neuron 89:1131-1156 |
| Poo, Mu-Ming; Pignatelli, Michele; Ryan, Tomás J et al. (2016) What is memory? The present state of the engram. BMC Biol 14:40 |
| Rink, Timothy J; Tsien, Louis Y; Tsien, Richard W (2016) Roger Yonchien Tsien (1952-2016). Nature 538:172 |
| Ma, Huan; Li, Boxing; Tsien, Richard W (2015) Distinct roles of multiple isoforms of CaMKII in signaling to the nucleus. Biochim Biophys Acta 1853:1953-7 |
| Ma, Huan; Groth, Rachel D; Cohen, Samuel M et al. (2014) ?CaMKII shuttles Ca²?/CaM to the nucleus to trigger CREB phosphorylation and gene expression. Cell 159:281-94 |
| Groth, Rachel D; Tirko, Natasha N; Tsien, Richard W (2014) CaV1.2 calcium channels: just cut out to be regulated? Neuron 82:939-40 |
