Dynamics of protein synthesis in dopamine-dependent hippocampal synaptic plasticity

How can the brain store our experiences in memory over long time periods? It is thought that memories are stored as changes in the connections between neurons, called synapses. We think that when a memory is stored, the connection between neurons becomes stronger. How strong one neuron responds to another depends on proteins (receptors) that are present at synapses. For memories to become persistent, the cell needs to produce new proteins. However, we still do not understand well which signals inform the cell when new proteins should be made, and we also do not know how the proteins are delivered specifically to those connections that should be strengthened.
In the proposed project, we will first study how signals induce neurons to make new proteins. Of all the events that we experience each day, why is it that some are remembered and others not? Many factors may influence how well we remember. For example, the presentation of a reward may help us remember the event better. Previous research has shown that dopamine, which is released when we receive a reward, is necessary for the neurons to produce new proteins. Here we want to study the underlying mechanism of how dopamine signals to the cell that it should make new protein. We also want to study how the newly produced proteins are distributed in the cell and delivered to the specific connections. To address these questions, we will use new labelling techniques that allow us to distinguish newly produced proteins from those that were already present in the cell.
The results should give us new insights into how memories are stored and could potentially open up new avenues for improving memory in ageing individuals and for treating memory disorder.

In the proposed project we will study fundamental mechanisms of protein-translation dependent LTP, as we as well dynamics of newly synthesised proteins in plasticity. We will combine a newly established, physiologically relevant plasticity protocol, which requires protein translation, with recently developed non-radioactive metabolic labelling methods to monitor newly synthesised proteins, such as the puromycin-based assay SUnSET.
First, we will investigate the mechanism by which dopamine induces protein translation-dependent plasticity using whole-cell patch clamp recordings and pharmacology.
Then, we will study the spatiotemporal dynamics of newly synthesised proteins in LTP using two-photon uncaging and imaging. We will investigate whether newly synthesised proteins are localised to a spine or a dendritic segment, or more globally in the neuron. Furthermore, we will combine these techniques with optogenetics to test whether dopamine release from dopaminergic nerve terminals is sufficient to induce protein translation. We will then investigate important specific newly synthesised proteins involved in plasticity using a proximity-ligation assay that allows identification specifically of newly synthesised proteins. The results of this proposed project would fundamentally broaden the understanding of the role of protein translation in the encoding of long-term memories.