Role of the protein phosphatase 1 inhibitor CPI-17 in ERM- and adhesion-dependent Ras regulation in neurons

神经营养作用由Ras家族的小g蛋白控制并传递给细胞反应。Ras是发育中的神经系统和成人神经系统的正常功能和可塑性所必需的。影响神经元中Ras的诱导和反调控机制必须严格控制，因为Ras调控的缺失与记忆和学习缺陷以及与年龄相关的脑退化有关。我们最近发现了一种控制非神经元细胞中Ras活性的新途径，其中包括磷酸酶MYPT-1-PP1δ及其抑制剂CPI-17。这种水平的Ras激活涉及MYPT-1-PP1δ靶点ezrin和merlin的磷酸化状态。初步结果表明，CPI-17在海马中正常表达，这促使我们研究神经元CPI-17在大脑特定区域对学习和记忆重要的merlin/ erm依赖性Ras调控中的作用。具体来说，CPI-17作为蛋白磷酸酶1 （PP1）抑制剂的信号活动将与细胞增殖、分化、突触可塑性和学习能力等功能读数相关。我们的研究范围将从各种神经元细胞模型系统的细胞培养研究，包括对初级海马神经元的研究，到使用转基因小鼠模型，诱导神经元限制性CPI-17过表达以及在大脑特定区域敲除CPI-17。我们打算建立这样的小鼠，并分析CPI-17对学习、记忆、突触传递和突触可塑性的影响。实验结果将提供Ras调控的详细图像，包括ezrin和merlin的磷酸化状态。这一机制可能代表了Ras在成人神经系统中控制神经元稳定性和可塑性的一个全新方面。

Neurotrophic actions are controlled and transmitted to cellular responses by the Ras family of small G-proteins. Ras is required for the normal functioning and plasticity of the developing, as well as the adult, nervous system. Induction and counter regulatory mechanisms that affect Ras in neurons must be tightly controlled, since loss of proper Ras regulation has been associated with memory and learning deficits, as well as age-related brain degeneration. We have recently identified a novel pathway controlling Ras activity in non-neuronal cells, which includes the phosphatase MYPT-1-PP1δ and its inhibitor CPI-17. This level of Ras activation involves the phosphorylation status of the MYPT-1-PP1δ targets ezrin and merlin. Preliminary results showing that CPI-17 is normally expressed in the hippocampus have prompted us to study the role of neuronal CPI-17 on merlin/ERM-dependent Ras regulation in specific areas of the brain important for learning and memory. Specifically, the signalling activities of CPI-17 as a protein phosphatase 1 (PP1) inhibitor will be correlated to functional readouts such as cell proliferation, differentiation, synaptic plasticity and learning capabilities. Our studies will range from cell culture studies on various neuronal cell model systems, including work on primary hippocampal neurons, to the use of a transgenic mouse model with inducible neuronal-restricted CPI-17 overexpression as well as knockout of CPI-17 in specific areas of the brain. We intend to create such mice and analyse the effects of CPI-17 on learning, memory, synaptic transmission and synaptic plasticity. The outcome of the experiments will provide a detailed picture of Ras regulation, involving the phosphorylation status of ezrin and merlin. This mechanism will likely represent a totally novel aspect of Ras control in neuronal stability and plasticity within the adult nervous system.