The long-term goal of this project is to elucidate the signaling mechanisms underlying activity-dependent synapse formation. We have demonstrated that the secreted glycoprotein Wingless (Wg/Wnt-1), best known for its crucial role in early morphogenesis and pattern formation, is also a fundamental organizer of glutamatergic synapses in the fruit fly Drosophila. Our current studies implicate Wnts in rapid, activity-dependent, structural and functional synaptic modifications. In humans, misregulation of Wnt signaling is associated with a number of cognitive disorders, such as schizophrenia, bipolar disorder, and Alzheimer's disease. Therefore, understanding the mechanisms of Wnt signaling in the nervous system will have important implications for our ability to design clinical strategies to treat these diseases. In this project our experimental approach makes extensive use of live imaging, including that of completely intact animals, combined with electron microscopy, molecular genetics, and electrophysiology to investigate the mechanisms by which activity induces the secretion of Wg and promotes new synaptic formation. We will also explore the synaptic role of Evenless Interrupted/ Wntless/Sprint, a multipass transmembrane protein recently discovered to be critical in epithelial Wg secretion. In particular we will (1) determine the role of electrical activity in Wg synthesis, trafficking and release, (2) determine the significance and molecular mechanisms of activity and Wg-dependent synaptic plasticity, and (3) determine the role of Evi at synapses and test the hypothesis that at the NMJ Evi mediates novel trans-synaptic signaling. We expect our findings will bring about important insights into the general nature of synapse plasticity, as these fly synapses show a considerable degree of molecular conservation with mammalian central synapses, and as Wnts are also involved in mammalian systems during synapse differentiation and long-term modifications in synaptic function.
An important characteristic of neuronal circuits is their ability to change, a property generally referred to as synaptic plasticity, which lies at the foundation of important processes such as learning and memory. Studies in both vertebrates and invertebrates have identified a signaling mechanism, mediated by the secreted protein Wnt/Wingless, which plays key roles in synaptic plasticity. In humans, misregulation of Wnt signaling is associated with a number of cognitive disorders, such as schizophrenia, bipolar disorder, and Alzheimer's disease. Therefore, understanding the mechanisms of Wnt signaling in the nervous system will have important implications for our ability to design clinical strategies to treat these diseases. The goal of this project is to use the powerful genetic approaches available for fruit flies to elucidate the function of Wnts in synaptic plasticity. Specifically in this project we will: (1) determine how synaptic activity induces the trafficking and secretion of Wnt to synapses, (2) investigate how Wnt induces synaptic plasticity, and (3), explore the function of a protein which is hypothesized as being involved in the transport of Wnt across the synapse.
|Kerr, Kimberly S; Fuentes-Medel, Yuly; Brewer, Cassandra et al. (2014) Glial wingless/Wnt regulates glutamate receptor clustering and synaptic physiology at the Drosophila neuromuscular junction. J Neurosci 34:2910-20|
|Korkut, Ceren; Li, Yihang; Koles, Kate et al. (2013) Regulation of postsynaptic retrograde signaling by presynaptic exosome release. Neuron 77:1039-46|
|Koon, Alex C; Budnik, Vivian (2012) Inhibitory control of synaptic and behavioral plasticity by octopaminergic signaling. J Neurosci 32:6312-22|
|Koles, Kate; Budnik, Vivian (2012) Wnt signaling in neuromuscular junction development. Cold Spring Harb Perspect Biol 4:|
|Budnik, Vivian; Salinas, Patricia C (2011) Wnt signaling during synaptic development and plasticity. Curr Opin Neurobiol 21:151-9|
|Koon, Alex C; Ashley, James; Barria, Romina et al. (2011) Autoregulatory and paracrine control of synaptic and behavioral plasticity by octopaminergic signaling. Nat Neurosci 14:190-9|
|Korkut, Ceren; Ataman, Bulent; Ramachandran, Preethi et al. (2009) Trans-synaptic transmission of vesicular Wnt signals through Evi/Wntless. Cell 139:393-404|
|Korkut, Ceren; Budnik, Vivian (2009) WNTs tune up the neuromuscular junction. Nat Rev Neurosci 10:627-34|
|Ramachandran, Preethi; Barria, Romina; Ashley, James et al. (2009) A critical step for postsynaptic F-actin organization: regulation of Baz/Par-3 localization by aPKC and PTEN. Dev Neurobiol 69:583-602|
|Ataman, Bulent; Ashley, James; Gorczyca, Michael et al. (2008) Rapid activity-dependent modifications in synaptic structure and function require bidirectional Wnt signaling. Neuron 57:705-18|
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