Post-Translational Control of Neuroplasticity Effector Arc/Arg3.1

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Neurons have the remarkable capacity to reorganize their structure, function, and connections in response to stimuli. Among the many signaling molecules and protein effectors found supporting these neuroplastic changes, the Activity-regulated cytoskeleton-associated protein (Arc) can be considered one of the central, as well as most versatile, players. Past research highlight the multiple roles of Arc in neurons; however, what allows this protein to assume one cellular function over another, or interact with the appropriate molecular effectors in response to a specific signal, remains poorly understood. The overarching goal of this Discovery Grant proposal is to test the hypothesis that lysine acetylation of Arc protein at precise sites produces a strong modulatory effect on its subcellular distribution, functions, and/or affinity with different partners. Ultimately, a better understanding of how this type of post-translational modification (PTM) is influencing Arc biology will advance our general understanding of the molecular basis of brain plasticity into new territories. During my postdoctoral training, I used a multidisciplinary approach to search for pharmacological modifiers of Arc expression and function. As part of this investigation, I collected the first evidence of Arc lysine acetylation using tandem mass spectrometry and other complementary biochemical strategies. An initial analysis of the four Arc lysine residues, which I identified as candidate targets for acetylation, revealed that modification of at least one of these sites (K24) could strikingly promote Arc protein accumulation by limiting its polyubiquitination and subsequent proteasomal degradation (Lalonde et al., accepted by Nature Communications). Overall, this finding suggests a strong influence of lysine acetylation on Arc biology and supports the need for a broader investigation into the functional impact, as well as molecular underpinnings, of this modification in neurons. In order to fulfill that goal, I propose to: 1) determine how the individual acetylation of previously identified Arc lysine residues could shape Arc-dependent processes, like AMPA receptor trafficking and dendritic spine morphogenesis, in cultured neurons; 2) establish with the help of proteomic techniques how lysine acetylation changes Arc subcellular distribution and its interaction with other proteins; and 3) uncover the specific acetyltransferase and deacetyltransferase enzymes mediating Arc acetylation in neuronal cells using a targeted RNAi screening strategy. Together, these three complementary lines of research will offer a clear portrait of the influence of lysine acetylation on the neurobiology of Arc, and provide a solid empirical foundation for extending, in the future, our examination of Arc acetylation towards brain development, behavioral control, and the mechanisms of learning and memory.