Degradation of Postsynaptic Scaffold GKAP and Regulation of Dendritic Spine Morphology by the TRIM[subscript 3] Ubiquitin Ligase in Rat Hippocampal Citation

Changes in neuronal activity modify the structure of dendritic spines and alter the function and protein composition of synapses. Regulated degradation of postsynaptic density (PSD) proteins by the ubiquitin-proteasome system is believed to play an important role in activity-dependent synaptic remodeling. Stimulating neuronal activity in vitro and in vivo induces the ubiquitination and degradation of GKAP/SAPAP and Shank, major scaffold proteins of the PSD. However, the specific ubiquitin ligases that regulate postsynaptic protein composition have not been identified. Here we identify the RING fingercontaining protein TRIM3 as a specific E3 ubiquitin ligase for the PSD scaffold GKAP/SAPAP1. Present in PSD fractions from rat brain, TRIM3 stimulates ubiquitination and proteasome-dependent degradation of GKAP, and induces the loss of GKAP and associated scaffold Shank1 from postsynaptic sites. Suppression of endogenous TRIM3 by RNA interference (RNAi) results in increased accumulation of GKAP and Shank1 at synapses, as well as enlargement of dendritic spine heads. RNAi of TRIM3 also prevented the loss of GKAP induced by synaptic activity. Thus, TRIM3 is a novel E3 ligase that mediates activitydependent turnover of PSD scaffold proteins and is a negative regulator of dendritic spine morphology. Citation: Hung AY, Sung CC, Brito IL, Sheng M (2010) Degradation of Postsynaptic Scaffold GKAP and Regulation of Dendritic Spine Morphology by the TRIM3 Ubiquitin Ligase in Rat Hippocampal Neurons. PLoS ONE 5(3): e9842. doi:10.1371/journal.pone.0009842 Editor: Fabien Tell, The Research Center of Neurobiology-Neurophysiology of Marseille, France Received September 28, 2009; Accepted March 2, 2010; Published March 24, 2010 Copyright: 2010 Hung et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The work was funded by National Institutes of Health K08 Award NS41411 (A.Y.H.). M.S. was an Investigator of the Howard Hughes Medical Institute. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: M.S. is presently an employee of Genentech Inc., South San Francisco, a member of the Roche Group. All of the work done for this study was performed at MIT. This does not alter the authors’ adherence to all PLoS ONE policies on sharing data and materials. * E-mail: [email protected]