F-BAR proteins in neuronal migration and process formation

打破神经元对称性是极化神经元形成的一个基本过程。大脑中的神经元 发育中的大脑皮层生下来就是球形细胞，必须延长前导和拖尾过程才能迁移 到达它们在发育中的皮质板的目的地。然后皮质神经元将长轴突和树突从 这些过程来创建功能电路。皮质神经元迁移和突起延伸至关重要 依赖于微管和肌动蛋白细胞骨架，但对肌动蛋白细胞骨架如何 和质膜在这些活动中是协调的。膜的突出和内陷是 需要质膜和底层肌动蛋白细胞骨架协调的基本细胞活动。 然而，关于膜突起和内陷如何在加工过程中整合的数据还很匮乏 突起和神经元迁移。F-bar超家族蛋白参与膜曲率传感 以及通过其F-bar结构域的变形，将它们定位为两个膜中潜在的重要角色 内陷和突出。在结构上，它们形成一个弯曲的二聚体，在内吞周围自我多聚体 小泡，使其伸长成小管。CIP4蛋白家族(CIP4、FBP17和TOCA1)是一个家族 结合肌动蛋白相关蛋白的F-bar蛋白。与其他F-bar蛋白一样，CIP4家族被认为是 CIP4主要在膜内陷和内吞中发挥作用，但我们最近的工作表明CIP4与神经元有关 膜的突起也一样。CIP4诱导的片状脂肪肌样突起强烈抑制神经突起生长 文化。相反，我们发现一个近亲家庭成员FBP17在皮质发育过程中形成内吞小管 并促进突出的丝状足突的形成，导致早熟的轴突生长。在这份提案中，我们 我将检验通过CIP4的突起和通过FBP17的内陷的新假说在对抗 调节发育中皮质神经元迁移和突起形成的方式。具体来说，我们会： 1)确定CIP4如何诱导膜突起和FBP17形成内吞小管，2)确定如何 膜管形成导致早熟丝状足的形成和轴突的生长，3)揭示了空间和 内源性标记的CIP4和FBP17在小鼠体内的时间表达模式和4)解析CIP4和 FBP17在活体皮质发育中发挥作用。这项工作将提供对蛋白质是如何 连接膜和肌动蛋白细胞骨架的功能，以调节突起过程和皮质神经元迁移 在哺乳动物早期发育的大脑中。CIP4和FBP17与亨廷顿氏病和 几种形式的癌症，强调了确定这些蛋白质在发育过程中功能的重要性 大脑皮层。

Breaking neuronal symmetry is a fundamental process in the formation of a polarized neuron. Neurons in the developing cerebral cortex are born as spherical cells that must extend leading and trailing processes to migrate to their destination in the developing cortical plate. Cortical neurons then extend long axons and dendrites from these processes to create functional circuits. Cortical neuron migration and process extension is critically dependent on the microtubule and actin cytoskeleton, but relatively little is known about how the actin cytoskeleton and plasma membrane are coordinated during these events. Membrane protrusion and invagination are fundamental cellular activities that require coordination of the plasma membrane and underlying actin cytoskeleton. However, there is a dearth of data on how membrane protrusion and invagination are integrated in process outgrowth and neuronal migration. The F-BAR superfamily of proteins are involved in membrane curvature sensing and deformation through their F-BAR domain, positioning them as potentially important players in both membrane invagination and protrusion. Structurally, they form a curved dimer that self-multimerizes around endocytic vesicles, causing their elongation into tubules. The CIP4 family of proteins (CIP4, FBP17 and TOCA1) is a group of F-BAR proteins that bind actin-associated proteins. Like other F-BAR proteins, the CIP4 family is thought to function primarily in membrane invagination and endocytosis, but our recent work has implicated CIP4 in neuronal membrane protrusion as well. Lamellipodial-like protrusions induced by CIP4 strongly inhibit neurite outgrowth in culture. Conversely, we find that a close family member, FBP17, forms endocytic tubules in developing cortical neurons and promotes prominent filopodia formation, resulting in precocious neurite outgrowth. In this proposal we will test the novel hypothesis that protrusion through CIP4 and invagination through FBP17 act in opposing manners to regulate cortical neuron migration and process formation in the developing cortex. Specifically, we will: 1) Determine how CIP4 induces membrane protrusions and FBP17 forms endocytic tubules, 2) Establish how membrane tubulation results in precocious filopodia formation and neurite outgrowth, 3) Reveal the spatial and temporal expression pattern of endogenously-labeled CIP4 and FBP17 in mouse lines and 4) Resolve CIP4 and FBP17 function in cortical development in vivo. This work will provide fundamental insights into how proteins that bridge the membrane and actin cytoskeleton function to regulate process outgrowth and cortical neuron migration in the early developing mammalian brain. CIP4 and FBP17 have been implicated in Huntington's disease and several forms of cancer, underscoring the importance of determining the function of these proteins in the developing cerebral cortex.