Ubuiquitin proteasome system regulates dendrite pruning of Drosophila sensory neuron. Tzu Lin, Yi-Ping Wu, Sih-Hua Chen, Hsiu-Hsiang Lee. Institute of Molecular Medicine, College of Medicine, National Taiwan University.

   During development, the nervous systems often require remodeling to refine their neuronal circuitry to achieve the mature neuronal connection. Neuronal pruning, one of the remodeling mechanisms in the nervous systems, selectively eliminates specific parts of neurites in the absence of cell death. Class VI dendritic arborization (C4da) neurons, a subset of Drosophila larval peripheral sensory neurons, which undergo a large-scale dendrite pruning during metamorphosis, provide an ideal model system to study the cellular and molecular mechanisms of neuronal pruning. It is known that the function of ubuiquitin proteasome system (UPS) is essential for neuronal pruning in the developing nervous systems of both vertebrates and invertebrates. Recently, we have identified on uncharacterized mutant that showed a defective dendrite pruning phenotype in Drosophila C4da neurons. The dendrite pruning defects in C4da cells of this uncharacterized mutant showed genetic interaction specifically with Rpn2, which encodes a non-ATPase subunit of the regulatory 19S proteasome, but not with Rpn6, which encodes another non-ATPase subunit of 19S proteasome. Moreover, depletion of Rpn2 proteins in C4da neurons by RNAi also showed impaired dendrite pruning phenotype. To further study the regulation of proteasomal activity during dendrite pruning, we generate Dendra2-based reporter lines to monitor live proteasomal activity in Drosophila neurons. Currently, we are characterizing the reporter lines and expect to monitor the proteasomal activity in wild type and mutant neurons during dendrite pruning in the near future.