Phosphorylation of Rpt6 regulates synaptic strength in hippocampal neurons.
Phosphorylation of Rpt6 regulates synaptic strength in hippocampal neurons.
复制标题
DOI：
10.1523/jneurosci.4427-11.2012
复制
发表时间：
2012-04-11
期刊：
影响因子：
--
通讯作者：
Patrick GN
中科院分区：
文献类型：
--
作者：
Djakovic SN;Marquez-Lona EM;Jakawich SK;Wright R;Chu C;Sutton MA;Patrick GN
越来越明显的是，通过泛素蛋白酶体系统进行的蛋白质降解在中枢神经系统突触连接的发育、维持和重塑中起着至关重要的作用。我们和其他研究人员最近描述了蛋白酶体活性的活动依赖性调节以及蛋白酶体向树突棘区室的募集，这涉及到可塑性激酶Ca2 +/钙调蛋白依赖性蛋白激酶IIα（CaMKIIα）对19S ATP酶亚基Rpt6的磷酸化。在此，我们研究了Rpt6磷酸化对蛋白酶体功能和突触强度的作用。利用一种磷酸化特异性抗体，我们证实Rpt6在丝氨酸120（S120）位点被CaMKIIα磷酸化。此外，我们发现Rpt6被CaMKIIα以活动依赖性方式磷酸化。此外，我们表明，Rpt6的丝氨酸120突变为天冬氨酸的磷酸化模拟突变体（S120D）增加了其在大鼠海马树突中对去污剂提取的抗性，这表明磷酸化的Rpt6可能促进蛋白酶体与支架和细胞骨架成分的连接。有趣的是，Rpt6 S120D的表达降低了微小兴奋性突触后电流（mEPSC）的幅度，而磷酸化失活突变体（S120A）的表达则增加了mEPSC的幅度。令人惊讶的是，长期应用荷包牡丹碱或河豚毒素所产生的mEPSC幅度的稳态调节既被改变的Rpt6磷酸化所模拟，又被其阻断。这些数据共同表明，CaMKII依赖的Rpt6在S120位点的磷酸化可能是在缓慢的稳态可塑性中蛋白酶体依赖的突触重塑控制的一个重要调节机制。
It has become increasingly evident that protein degradation via the ubiquitin proteasome system plays a fundamental role in the development, maintenance and remodeling of synaptic connections in the central nervous system. We and others have recently described the activity-dependent regulation of proteasome activity and recruitment of proteasomes into spine compartments involving the phosphorylation of the 19S ATPase subunit, Rpt6, by the plasticity kinase Ca2+/calmodulin-dependent protein kinases II alpha CaMKIIα). Here, we investigated the role of Rpt6 phosphorylation on proteasome function and synaptic strength. Utilizing a phospho-specific antibody we verified that Rpt6 is phosphorylated at Serine 120 (S120) by CaMKIIα. In addition, we found that Rpt6 is phosphorylated by CaMKIIα in an activity-dependent manner. In addition, we showed that a serine 120 to aspartic acid phospho-mimetic mutant of Rpt6 (S120D) increases its resistance to detergent extraction in rat hippocampal dendrites, indicating phosphorylated Rpt6 may promote the tethering of proteasomes to scaffolds and cytoskeletal components. Interestingly, expression of Rpt6 S120D decreased miniature excitatory postsynaptic current (mEPSC) amplitude, while expression of a phospho-dead mutant (S120A) increased mEPSC amplitude. Surprisingly, homeostatic scaling of mEPSC amplitude produced by chronic application of bicuculline or tetrodotoxin is both mimicked and occluded by altered Rpt6 phosphorylation. Together these data suggest that CaMKII-dependent phosphorylation of Rpt6 at S120 may be an important regulatory mechanism for proteasome-dependent control of synaptic remodeling in slow homeostatic plasticity.