Regulation of synapse growth by mTOR pathway
The regulated production of proteins in neurons in response to extracellular stimuli has emerged as an important and common mechanism for the modification of synapses. In addition, ample evidence now supports that proteins can be made within neuronal subcompartments such as dendrites. However, the spatial scale over which protein translation is independently regulated and whether it is truly controlled locally in dendrites by focal synaptic activity are unknown. Furthermore, the pathways that link synaptic stimuli to the control of protein production are unclear. In many cell types, the regulation of protein translation in response to extracellular stimuli occurs through the mTOR pathway. An important role for the mTOR pathway is neurons is indicated by the association of mutations in the pathway with the human neurological disorders Tuberous Sclerosis Complex (TSC) and Lhermitte-Duclos Disease (LDD) and the finding that pharmacological inhibitors of mTOR interfere with several forms of long-term synaptic plasticity. The research proposed here will examine the regulation of the mTOR pathway by synaptic stimuli and its role controlling dendritic and synaptic growth. Traditional biochemcial approaches will be used to systematically map the sets of stimuli that activate or repress protein translation in neurons. 2-photon uncaging of glutamate will be used to focally activate synapses and to probe the spatial scale of regulation of protein translation in dendrites. The perturbation of dendritic spine growth and synaptic plasticity resulting from interfering with the mTOR pathway and from genetic mutations associated with TSC and LDD will be determined. Lastly, electrophysiogical analysis and calcium imaging will be used to uncover functional defects arising from interfering with the mTOR pathway.