Djakovic Stevan N, Schwarz Lindsay A, Barylko Barbara, DeMartino George N, Patrick Gentry N
Section of Neurobiology, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093-0347, USA.
J Biol Chem. 2009 Sep 25;284(39):26655-65. doi: 10.1074/jbc.M109.021956. Epub 2009 Jul 28.
Protein degradation via the ubiquitin proteasome system has been shown to regulate changes in synaptic strength that underlie multiple forms of synaptic plasticity. It is plausible, therefore, that the ubiquitin proteasome system is itself regulated by synaptic activity. By utilizing live-cell imaging strategies we report the rapid and dynamic regulation of the proteasome in hippocampal neurons by synaptic activity. We find that the blockade of action potentials (APs) with tetrodotoxin inhibited the activity of the proteasome, whereas the up-regulation of APs with bicuculline dramatically increased the activity of the proteasome. In addition, the regulation of the proteasome is dependent upon external calcium entry in part through N-methyl-D-aspartate receptors and L-type voltage-gated calcium channels and requires the activity of calcium/calmodulin-dependent protein kinase II (CaMKII). Using in vitro and in vivo assays we find that CaMKII stimulates proteasome activity and directly phosphorylates Rpt6, a subunit of the 19 S (PA700) subcomplex of the 26 S proteasome. Our data provide a novel mechanism whereby CaMKII may regulate the proteasome in neurons to facilitate remodeling of synaptic connections through protein degradation.
通过泛素蛋白酶体系统进行的蛋白质降解已被证明可调节突触强度的变化，而突触强度的变化是多种形式突触可塑性的基础。因此，泛素蛋白酶体系统本身受突触活动调节是合理的。通过利用活细胞成像策略，我们报告了突触活动对海马神经元中蛋白酶体的快速动态调节。我们发现，用河豚毒素阻断动作电位（APs）会抑制蛋白酶体的活性，而用荷包牡丹碱上调APs则会显著增加蛋白酶体的活性。此外，蛋白酶体的调节部分依赖于通过N-甲基-D-天冬氨酸受体和L型电压门控钙通道的外部钙内流，并且需要钙/钙调蛋白依赖性蛋白激酶II（CaMKII）的活性。使用体外和体内试验，我们发现CaMKII刺激蛋白酶体活性并直接磷酸化Rpt6，Rpt6是26S蛋白酶体19S（PA700）亚复合物的一个亚基。我们的数据提供了一种新机制，通过该机制CaMKII可能调节神经元中的蛋白酶体，以通过蛋白质降解促进突触连接的重塑。
