Antagonistic roles of HuD and KSRP for mRNA stability in neuronal growth

 描述（由申请人提供）：轴突和树突的延伸和成熟是使神经系统发挥功能的重要发育步骤。这种发展需要精确调控基因表达，协调激活和失活与神经元的生长，成熟和功能相关的基因表达程序。神经元突起或“神经突”的生长必须精确地定时和调节，以产生功能性神经回路。基因表达的调控不仅仅是将DNA转录成mRNA，而且越来越清楚的是，许多调控发生在神经元的转录后。调控步骤包括mRNA的剪接、亚细胞定位和翻译控制。mRNA的稳定性在基因表达中起着关键作用，通过改变可作为模板的单个mRNA的量来随时间产生新的蛋白质。生长中的神经突内mRNA的稳定和不稳定也会影响新蛋白质的产生。尽管越来越多的认识到这一机制的重要性，我们有一点了解神经元mRNA的稳定性是如何调节。PI和Co-PI实验室最近的工作已经揭示了神经元中mRNA稳定性调节的机制。RNA结合蛋白KSRP和HuD竞争结合GAP-43 mRNA。已知这两种RNA结合蛋白具有多种功能，并且我们的数据表明KSRP和HuD具有拮抗功能。对于GAP-43 mRNA，KSRP结合使转录物不稳定，而HuD结合使转录物稳定。通过初始CLIP分析，KSRP和HuD可以结合重叠的mRNA组群，并且细胞质KSRP似乎提供了通过使mRNA不稳定来限制神经突长度的调控因子。这些数据使我们假设，HuD和KSRP与特定的含ARE的mRNA的队列的竞争性相互作用控制神经元蛋白表达的时间和空间模式在轴突生长的起始和终止通过mRNA的稳定性的变化。我们将用三个具体目标来检验这一假设：1）KSRP是否使神经元mRNA群不稳定？2)KSRP或HuD相互作用是否改变了定位mRNA的稳定性？3)KSRP和HuD是否竞争与具有拮抗功能的mRNA的共享队列结合？这些目标的完成将填补神经元mRNA稳定性机制及其对大脑发育的贡献的知识空白。

 DESCRIPTION (provided by applicant): Extension and maturation of axons and dendrites are essential developmental steps that allow the nervous system to function. This development requires precise regulation of gene expression, with coordinated activation and inactivation of gene expression programs associated with growth, maturation, and function of neurons. Growth of neuronal processes or `neurites' must be precisely timed and regulated to generate functional neural circuits. Regulation of gene expression extends beyond transcribing DNA into mRNAs, and it has become increasingly clear that much regulation occurs post-transcriptionally in neurons. Regulatory steps include splicing, subcellular localization, and translational control of mRNAs. Stability of mRNAs plays a critical role in gene expression by modifying the amount of an individual mRNA available as a template for generating new protein over time. Stabilization and destabilization of mRNAs within growing neurites also impacts where new proteins are produced. Despite increased recognition of importance of this mechanism, we have little understanding of how neuronal mRNA stability is regulated. Recent work from the PI's and Co- PI's labs have uncovered a mechanism for modulation of mRNA stability in neurons. The RNA binding proteins KSRP and HuD compete for binding to GAP-43 mRNA. Both these RNA binding proteins are known to have multiple functions, and our data suggest that KSRP and HuD have antagonistic functions. For GAP-43 mRNA, KSRP binding destabilizes the transcript while HuD binding stabilizes the transcript. By initial CLIP analyses, KSRP and HuD can bind to overlapping cohorts of mRNAs and cytoplasmic KSRP appears to provide a governor to limit neurite length by destabilizing mRNAs. These data have led us to hypothesize that competitive interactions of HuD and KSRP with specific cohorts of ARE-containing mRNAs control the temporal and spatial pattern of neuronal protein expression during the initiation and termination of neurite outgrowth through changes in mRNA stability. We will test this hypothesis with three specific aims: 1) Does KSRP destabilize neuronal mRNA cohorts? 2) Do KSRP or HuD interactions alter stability of localized mRNAs? 3) Do KSRP and HuD compete for binding to a shared cohort of mRNAs with antagonistic functions? Completion of these aims will fill a gap in knowledge on mechanisms of neuronal mRNA stability and its contributions to brain development.