Investigating the molecular mechanisms of early neuronal morphogenesis

摘要 细胞形态是多细胞生物体细胞最显著的特征之一 与细胞功能密切相关。神经元和其他极化细胞如何致力于它们的形态 鲜为人知，但培养中分离细胞的自发形态发生表明， 形态的指令通常是内在编码的。我们之前发现了一种序列特异的RNA- 结合蛋白，杂乱无章，作为建立早期神经元形态所必需的一个因素 作为一种蛋白质，它能够赋予非神经元起源的细胞类似的形状。凌乱不堪 识别主要在其翻译的编码区mRNAs内的唯一结合基序 抑制。目前尚不清楚凌乱如何规范翻译，也不清楚翻译或其他功能 凌乱的形态是诱导细胞极化的关键。在这里，我们寻求通过以下方式解决这一问题 破译凌乱驱动的细胞形状重塑的机制基础。我们的初步研究 表明在粗毛虫广泛的蛋白质-蛋白质相互作用网络中，粗毛虫之间的相互作用 低复杂结构域(LCD)和CCR4-NOT复合体是诱导细胞所必需的 形态发生。我们提出了三个特定的目标来研究CCR4的分子和细胞作用- 不是复杂的，作为凌乱控制的细胞形态发生的关键效应器。首先，我们将调查 杂乱无章的性质--CCR4--非互动及其对目标信息命运的影响，重点 尤其是它们的聚(A)尾长、稳定性和平移。第二，我们将审问招聘人员 以及CCR4-NOT在蓬乱诱导的细胞形态发生中的作用。第三，我们将确定 Unkempt对其与CCR4相互作用的翻译后修饰--不包括复合体和RNA 因为它控制着局部蛋白质的翻译。这项研究将阐明早期的分子基础。 神经元的形态发生，有助于我们对控制细胞的线索的一般理解 发育和疾病中的形态。

SUMMARY Cellular morphology is one of the most distinctive features of somatic cells in multicellular organisms and is intimately linked with cellular function. How neurons and other polarized cells commit to their morphologies is poorly understood, but spontaneous morphogenesis of dissociated cells in culture suggest that the basic instructions for morphology are often intrinsically encoded. We previously identified a sequence-specific RNA- binding protein, Unkempt, as a factor that is essential for the establishment of the early neuronal morphology and as a protein that is capable of endowing a similar shape to cells of nonneuronal origin. Unkempt recognizes a unique binding motif predominantly within coding regions mRNAs the translation of which it suppresses. It is unclear how Unkempt regulates translation, and whether translation or another functional modality of Unkempt is critical to its induction of cell polarization. Here, we seek to solve this problem by deciphering the mechanistic basis of Unkempt-driven remodeling of cellular shape. Our preliminary studies indicate that in the broad protein-protein interaction network of Unkempt, the interaction between Unkempt’s low-complexity domain (LCD) and the CCR4-NOT complex is exquisitely required for the induction of cell morphogenesis. We propose three specific aims to investigate the molecular and cellular roles of the CCR4- NOT complex as a critical effector of Unkempt-controlled cell morphogenesis. First, we will investigate the nature of Unkempt – CCR4-NOT interactions and their impact on the fate of the targeted messages, focusing in particular on their poly(A) tail length, stability, and translation. Second, we will interrogate the recruitment and function of CCR4-NOT in Unkempt-induced cell morphogenesis. Third, we will determine the effect of post-translational modifications of Unkempt on its interactions with the CCR4-NOT complex and RNA, as well as its control of local protein translation. This study will shed light on the molecular underpinnings of the early neuronal morphogenesis and contribute to our general understanding of the cues that control cellular morphology in development and disease.