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

 描述(申请人提供)：轴突和树突的延伸和成熟是神经系统发挥作用的基本发育步骤。这种发展需要对基因表达的精确调控，以及与神经元的生长、成熟和功能相关的基因表达程序的协调激活和失活。神经突起或“神经突起”的生长必须精确地计时和调节，才能产生功能神经回路。基因表达的调控不仅仅是将DNA转录成mRNAs，而且越来越清楚的是，许多调控发生在转录后的神经元中。调控步骤包括mRNAs的剪接、亚细胞定位和翻译控制。MRNAs的稳定性在基因表达中起着关键作用，它可以改变单个mRNA的量，随着时间的推移，它可以作为产生新蛋白质的模板。生长中的轴突中mRNAs的稳定和不稳定也会影响新蛋白质的产生。尽管越来越多的人认识到这一机制的重要性，但我们对神经元mRNA稳定性是如何调节的知之甚少。PI和Co-PI实验室最近的工作揭示了神经元中mRNA稳定性的调节机制。RNA结合蛋白KSRP和HUD竞争与GAP-43mRNA的结合。这两种RNA结合蛋白都具有多种功能，我们的数据表明KSRP和HUD具有拮抗功能。对于GAP-43mRNA，KSRP结合使转录本不稳定，而HUD结合使转录本稳定。通过初步的CLIP分析，KSRP和HUD可以与重叠的mRNAs结合，细胞质KSRP似乎提供了一个调节器，通过破坏mRNAs来限制轴突长度。这些数据使我们假设，HUD和KSRP与特定的含有ARE的mRNAs的竞争性相互作用通过改变mRNA的稳定性来控制轴突生长的启动和终止过程中神经元蛋白表达的时空模式。我们将通过三个具体的目标来检验这一假说：1)KSRP是否破坏了神经元mRNA队列的稳定？2)KSRP或HUD的相互作用是否改变了局部mRNAs的稳定性？3)KSRP和HUD是否竞争结合到具有拮抗功能的共享mRNA群？这些目标的完成将填补关于神经元mRNA稳定机制及其对大脑发育贡献的知识空白。

 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.