The turnover of synaptic proteins: numbers, principles, and functional implications

• Applicants: Dr. Eugenio Fornasiero, Ph.D.; Professor Dr. Silvio-Olivier Rizzoli, Ph.D.
• Subject Area: Molecular Biology and Physiology of Neurons and Glial Cells
• Term: since 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 273518920

Aged proteins must be replaced by newly produced ones in a precisely coordinated fashion. This process, termed protein turnover, is especially important in neurons, since they are long-lived and are very difficult to replace, which implies that their metabolism must be optimally regulated.In the first funding period of this grant we have generated multiple tools and techniques to study the turnover of the brain, including novel developments in conventional mass spectrometry and in imaging secondary ion mass spectrometry (SIMS). We have measured protein lifetimes in the brain of mice, and we also followed protein turnover in neuronal cultures. Our work demonstrated, among other findings, that protein turnover is intimately linked to synaptic and neuronal activity.We now propose to continue this work, by focusing on the aging brain. Our hypothesis, based on extensive preliminary work, is that protein turnover slows down in the aged brain, especially in the exo- and endocytosis pathway, which probably results in functional errors. We therefore aim to determine how turnover changes in aged mice, and how the changes influence synaptic structure and function. This will enable us to determine the general turnover mechanisms that differentiate the aging brain from the young brain. We will also be able to pinpoint specific molecular pathways that are differentially regulated in the aging brain, including changes in the vesicle exo- and endocytosis pathway, which appears to be particularly affected in the aged mice. Using imaging mass spectrometry, we will determine whether aging affects protein turnover in all neurons in the same fashion, or whether specific areas, neurons, or synapses are more prominently affected. We will also relate protein turnover to the ability to function of the respective neurons and synapses. Finally, we will verify and validate the molecular pathways determined in the previous objectives, by relying on neuronal cultures.This study will generate a first view of how ageing affects the protein turnover of the brain and synapse, and in turn on how turnover affects the function of the ageing neurons.

• DFG Programme: Research Grants