REGULATION OF DENDRITE MORPHOGENESIS BY A CONTROSOMAL CAMKIIB SIGNALING PATHWAY

描述(申请人提供)：拟议研究的长期目标是阐明调控哺乳动物大脑中神经元形态发生和连通性的信号机制。主要的蛋白激酶CaMKII主要由大脑中的Alpha和Beta亚型组成。虽然CaMKIIBeta的功能已被阐明，但CaMKIIBeta的异构体特异性催化功能在很大程度上仍未被探索。通过对原代大鼠神经元和在体啮齿动物小脑皮质进行严格控制的基因敲除分析，我们最近发现了CaMKIIBeta在哺乳动物大脑中的第一个独特的催化功能。值得注意的是，CaMKIIBeta以不依赖于CaMKIIAlpha的方式在中心体操作，以驱动树突回缩和修剪。在其他研究中，我们发现Trp通道TRPC5与CaMKIIBeta形成特异性的复合体，而不是CaMKIIAlpha，从而触发中心体CaMKIIBeta信号的激活，导致颗粒神经元和小脑皮质中的树突收缩和修剪。我们的发现定义了一个新的TRPC5调节的中心体CaMKIIBeta信号通路，它控制哺乳动物大脑中的树突图案。我们的发现也提出了关于TRPC5的分子基础-中心体CaMKIIBeta信号的调节以及中心体CaMKIIBeta调节树突形态发生的机制的基本问题。为了解决这些问题，在结构-功能分析中，我们将检验这样一种假设，即TRPC5和CaMKIIBeta中不同的肽基序指定TRPC5/CaMKIIBeta相互作用，从而调节啮齿动物小脑皮质中的树突图案。使用候选的和创新的无偏见的生化方法，我们将鉴定中心体CaMKIIBeta的新底物，并确定它们在CaMKIIBeta调节颗粒神经元和啮齿动物小脑皮质树突形态发生中的作用。最后，在最近令人兴奋的研究中，我们发现蛋白酶体在中心体上运行，促进树突的生长。基于初步数据，我们将检验中心体CaMKIIBeta信号调节中心体蛋白酶体活性从而控制树突形态发生的假设。这项拟议的研究代表了一系列重要的实验，将促进我们对哺乳动物大脑中控制树突图案和连通性的机制的理解。由于树突连接的中断导致了包括智能障碍和自闭症谱系障碍在内的各种神经系统疾病的发病，我们的研究也将促进我们对这些破坏性神经疾病的理解。

DESCRIPTION (provided by applicant): The long-term goals of the proposed research are to elucidate the signaling mechanisms regulating neuronal morphogenesis and connectivity in the mammalian brain. The major protein kinase CaMKII predominantly consists of the Alpha and Beta isoforms in the brain. Although CaMKIIBeta functions have been elucidated, the isoform- specific catalytic functions of CaMKIIBeta have remained largely unexplored. Using rigorously controlled knockdown analyses in primary rat neurons and in the rodent cerebellar cortex in vivo, we recently discovered the first unique catalytic function of CaMKIIBeta in the mammalian brain. Remarkably, CaMKIIBeta operates at the centrosome in a CaMKIIAlpha-independent manner to drive dendrite retraction and pruning. In other studies, we found that the TRP channel TRPC5 forms a specific complex with CaMKIIBeta, but not CaMKIIAlpha, and thereby triggers the activation of centrosomal CaMKIIBeta signaling leading to dendrite retraction and pruning in granule neurons and in the cerebellar cortex in vivo. Our findings define a novel TRPC5-regulated centrosomal CaMKIIBeta signaling pathway that controls dendrite patterning in the mammalian brain. Our findings also raise fundamental questions on the molecular basis of TRPC5-regulation of CaMKIIBeta signaling at the centrosome and the mechanisms by which centrosomal CaMKIIBeta regulates dendrite morphogenesis. To address these questions, in structure-function analyses we will test the hypothesis that distinct peptide motifs within TRPC5 and CaMKIIBeta specify the TRPC5/CaMKIIBeta interaction and thereby regulate dendrite patterning in the rodent cerebellar cortex in vivo. Using candidate and innovative unbiased biochemical approaches, we will identify novel substrates of centrosomal CaMKIIBeta and determine their role in the CaMKIIBeta-regulation of dendrite morphogenesis in granule neurons and in the rodent cerebellar cortex in vivo. Finally, in recent exciting studies, we have discovered that proteasomes operate at the centrosome to promote dendrite growth. Based on preliminary data, we will test the hypothesis that centrosomal CaMKIIBeta signaling regulates proteasome activity at the centrosome and thereby controls dendrite morphogenesis. The proposed research represents an important set of experiments that will advance our understanding of the mechanisms that control dendrite patterning and connectivity in the mammalian brain. Since disruption of dendrite connectivity contributes to the pathogenesis of diverse neurological diseases including intellectual disability and autism spectrum disorders, our studies will also advance our understanding of these devastating neurological diseases.