Role of DYRK1A/MNB in synaptic growth and function

PROJECT SUMMARY The nervous system fine-tunes synaptic output to ensure reliable communication, partly through kinase-drive protein phosphorylation. Alterations in phosphorylation dynamics profoundly affect neurotransmitter release, synaptic vesicle recycling, synaptic growth and plasticity, and are closely associated with neurodevelopmental and neurodegenerative disorders. The evolutionarily conserved DYRK1A kinase plays a critical role in neurodevelopment and is implicated in several neurological conditions, including autism, Down syndrome, intellectual disabilities, and Alzheimer’s disease. Despite its importance, the precise mechanisms by which DYRK1A regulates synaptic function remain unclear, and its physiological substrates are largely unidentified. Using Drosophila as a model, our previous work demonstrated that the DYRK1A homolog, minibrain kinase (MNB), is essential for synaptic transmission, modulating clathrin-mediated and bulk vesicle endocytosis through the phosphorylation of synaptojanin. To advance our understanding of MNB functions in vivo, we developed an innovative approach that integrates proximity labeling with phosphoprofiling to identify novel physiological substrates and pathways regulated by MNB in neurons. Building on these preliminary findings, this proposal aims to investigate two novel MNB-regulated pathways at the synapse: selective autophagy and neuropeptide release. Aim 1 will examine the role of MNB/DYRK1A in regulating autophagy at the synapse. We hypothesize that MNB phosphorylation of a protein required for selective autophagy facilitates the removal of damaged synaptic components and toxic aggregates. Additionally, we will investigate the role of MNB-dependent phosphorylation in modulating TDP-43 aggregation in a fly model of frontotemporal dementia and amyotrophic lateral sclerosis. Aim 2 will determine and validate MNB/DYRK1A's role in regulating neuropeptide release. The proposed research will provide critical insights into MNB's regulatory roles at the synapse, offering new perspectives on the molecular mechanisms of synaptic activity and potential therapeutic avenues for neurodegenerative diseases. Additionally, our innovative kinase substrate identification method can be broadly applied to other kinases, offering a powerful tool for future studies.