Rajgor Dipen, Fiuza Maria, Parkinson Gabrielle T, Hanley Jonathan G
From the School of Biochemistry and the Centre for Synaptic Plasticity, University of Bristol, Bristol BS8 1TD, United Kingdom.
From the School of Biochemistry and the Centre for Synaptic Plasticity, University of Bristol, Bristol BS8 1TD, United Kingdom
J Biol Chem. 2017 Jun 9;292(23):9774-9786. doi: 10.1074/jbc.M117.776302. Epub 2017 Apr 12.
MicroRNAs (miRNAs) are important regulators of localized mRNA translation in neuronal dendrites. The presence of RNA-induced silencing complex proteins in these compartments and the dynamic miRNA expression changes that occur in response to neuronal stimulation highlight their importance in synaptic plasticity. Previously, we demonstrated a novel interaction between the major RNA-induced silencing complex component Argounaute-2 (Ago2) and the BAR (bin/amphiphysin/rvs) domain protein PICK1. PICK1 recruits Ago2 to recycling endosomes in dendrites, where it inhibits miRNA-mediated translational repression. Chemical induction of long-term depression via NMDA receptor activation causes the dissociation of Ago2 from PICK1 and a consequent increase in dendritic miRNA-mediated gene silencing. The mechanism that underlies the regulation of PICK1-Ago2 binding is unknown. In this study, we demonstrate that the PICK1-Ago2 interaction is directly sensitive to Ca ions so that high [Ca] reduces PICK1 binding to Ago2. Mutating a stretch of C-terminal Ca-binding residues in PICK1 results in a complete block of NMDA-induced PICK1-Ago2 disassociation in cortical neurons. Furthermore, the same mutant also blocks NMDA-stimulated miRNA-mediated gene silencing. This study defines a novel mechanism whereby elevated [Ca] induced by NMDA receptor activation modulates Ago2 and miRNA activity via PICK1. Our work suggests a Ca-dependent process to regulate miRNA activity in neurons in response to the induction of long-term depression.
微小RNA（miRNA）是神经元树突中局部mRNA翻译的重要调节因子。这些区域中存在RNA诱导沉默复合体蛋白，以及响应神经元刺激而发生的动态miRNA表达变化，突出了它们在突触可塑性中的重要性。此前，我们证明了主要的RNA诱导沉默复合体成分AGO2（Argonaute-2）与BAR（bin/amphiphysin/rvs）结构域蛋白PICK1之间存在一种新的相互作用。PICK1将AGO2招募到树突中的回收内体，在那里它抑制miRNA介导的翻译抑制。通过NMDA受体激活化学诱导长时程抑制会导致AGO2与PICK1解离，从而使树突中miRNA介导的基因沉默增加。PICK1-AGO2结合调控的潜在机制尚不清楚。在本研究中，我们证明PICK1-AGO2相互作用对钙离子直接敏感，因此高钙离子浓度会降低PICK1与AGO2的结合。突变PICK1中一段C端钙离子结合残基会导致皮质神经元中NMDA诱导的PICK1-AGO2解离完全受阻。此外，相同的突变体也会阻断NMDA刺激的miRNA介导的基因沉默。本研究定义了一种新机制，即NMDA受体激活诱导的钙离子浓度升高通过PICK1调节AGO2和miRNA活性。我们的工作提示了一种钙离子依赖的过程，以响应长时程抑制的诱导来调节神经元中的miRNA活性。
