NEURONAL ACTIVITY AND INTRACELLULAR SIGNALING

描述(改编自申请者摘要)：依赖活动的监管 神经功能的启动在很大程度上是通过去极化诱导的 钙离子内流。已有研究表明，神经元钙离子可以激活许多 细胞内激酶级联调节基因转录、 突触可塑性和细胞存活。其中许多依赖于活动 神经营养因子家族的功能是相同的，这表明 共同的信号通路。两条途径，cAMP非依赖性蛋白激酶 (PKA)级联和细胞外信号调节激酶(ERK)级联 被认为是神经元钙信号转导的潜在靶点。 申请人实验室的最新数据发现了一种新的信号 NGF和cAMP信号的下游通路。这条途径涉及到 依赖PKA的RAS相关小G蛋白Rap1和Rap1的激活 随后激活神经元特异性ERK级联反应。主要假说 这一提议的关键是刺激这种依赖于Rap的ERK级联是一种 活性依赖性钙内流的靶点。这项提议利用了膜 PC12神经元系和海马神经元的去极化 模拟钙内流的活性依赖性调节。申请者将测试 假设小G蛋白Rap1参与了 去极化介导的ERKs激活。最近的研究表明， 神经元RAP1被多个第二信使激活。因此， 申请者进一步提出，研究像神经营养一样， 在RAP1的信号转导中，PKA是神经元钙激活所必需的。最后， 申请者还将测试RAP1激活可以偶联的假设 钙内流对ERKs的两种核作用：细胞外信号转位 ERK本身和CREB依赖的转录。这篇文章中概述的工作 格兰特将影响神经科学的许多领域，并将指出Rap1是 神经元信号的汇合点。鉴于PKA的作用得到了很好的证明 而CREB在这些伴随神经元活动的长期变化中， 这些对PC12细胞的研究很可能会确定 RAP依赖的通路在长期变化中。申请人认为 这项提案中概述的实验最终可能会影响到更广泛的 突触可塑性、长时程增强与神经元的研究 生死存亡。

DESCRIPTION (Adapted from applicant's abstract): Activity-dependent regulation of neuronal function is initiated in large part via depolarization-induced calcium influx. Neuronal calcium has been shown to activate a number of intracellular kinase cascades to regulate processes such as gene transcription, synaptic plasticity and cell survival. Many of these activity-dependent functions are shared by the neurotrophin family of growth factors suggesting a common signaling pathway. Two pathways, the cAMP independent protein kinase (PKA) cascade and the extracellular signal regulated kinase (ERK) cascade have been implicated as potential targets for neuronal calcium-mediated signaling. Recent data in the applicant's laboratory have identified a novel signaling pathway downstream of NGF and cAMP signaling. This pathway involves PKA-dependent activation of the Ras-related small G protein, Rap1, and subsequent activation of a neuronal-specific ERK cascade. The major hypothesis of this proposal is that stimulation of this Rap-dependent ERK cascade is a target for activity-dependent calcium influx. This proposal utilizes membrane depolarization of both the PC12 neuronal cell line and hippocampal neurons to mimic activity-dependent regulation of calcium influx. The applicant will test the hypothesis that the small G protein Rap1 participates in the depolarization-mediated activation of ERKs. Recent studies have shown that neuronal Rap1 is activated by multiple second messengers. Therefore, the applicant further proposes to examine the possibility that, like neurotrophic signaling, PKA is required for neuronal calcium activation of Rap1. Finally, the applicant will also test the hypothesis that activation of Rap1 can couple calcium influx to two nuclear actions of ERKs: the nuclear translocation of ERKs themselves and CREB-dependent transcription. The work outlined in this grant will impact many areas of neuroscience and will point to Rap1 as a confluence point of neuronal signals. Given the well documented role for PKA and CREB in these long-term changes that accompany neuronal activity, it is likely that these studies in PC12 cells will identify the importance of Rap-dependent pathways in the long-term changes. The applicant believes that the experiments outlined in this proposal may ultimately impact more general research on synaptic plasticity, long-term potentiation (LTP) and neuronal survival.