Strn3 is a novel Rac1 effector in Schwann cells

项目总结/摘要 在外周神经系统（PNS）发育过程中，雪旺细胞（SC）经历广泛的Rac 1- 依赖于细胞骨架重组，因为它们将细胞质延伸插入轴突束中以进行放射状分选， 包鞘和髓鞘化单个轴突。类似地，在周围神经损伤后，存在广泛的Rac 1- 在称为施密特-兰特曼切口（SLI）的专门区域周围依赖肌动蛋白聚合， SC分化为修复表型2。Feltri实验室先前证明， SC是由α6β1整合素与层粘连蛋白的结合驱动的，这对周围神经的生长至关重要。 发展4.使用蛋白质组学筛选，我们随后将Striatin-3（Strn 3）鉴定为新的候选Rac 1 周围神经的相互作用。Striatin蛋白（Strn 1/3/4）作为Striatin的核心支架成分发挥作用。 相互作用磷酸酶和激酶（STRIPAK）复合物。STRIPAK复合体成员包括 上游Hippo途径激酶Mst 1/2和磷酸酶PP 2A-C，其使Mst 1/2去磷酸化， 使Hippo通路失活，允许机械敏感性转录辅因子的核转位， 活化剂雅普/Taz 26，27，28. Feltri实验室先前证明，SC中的雅普/Taz活性也是 对有髓外周神经发育至关重要25.最初的体外数据表明，敲低Strn 3基因， SC损害其粘附于各种基质的能力，降低增殖，并破坏其结合 有轴突。然后，我生成了一个在SC中特异性缺失Strn 3的小鼠模型（Strn 3SCKO）， 表现出早期放射状分选和髓鞘形成不足缺陷。此外，从这些细胞中分离的Strn 3无效SC 动物在层粘连蛋白基质上显示出降低的伸长和突起延伸。因此，我假设， 在SC中，Strn 3通过与Rac 1相互作用而被外周神经发育和损伤反应所需， STRIPAK介导的Hippo通路调节。为了研究这一假设，将Strn 3SCKO小鼠 进一步通过发育期间的形态、功能和电生理测量表征， 伤后在组织和分离的Strn 3无效SC中的细胞和生物化学实验将确定Strn 3 事实上，通过与Rac 1、STRIPAK复合物和Hippo通路相互作用来调节SC。长期 本研究的目的是了解Strn 3和STRIPAK复合体在外周神经损伤中的功能， 发展和修复，以推进基础神经科学领域，并确定新的治疗目标， 减轻患有脱髓鞘性神经病的患者的疾病负担的潜力， 创伤性周围神经损伤该项目将与强调科学的培训计划相结合。 沟通，解决问题，批判性思维，技术技能和临床经验。研究培训将 发生在亨特詹姆斯凯利研究所，一个跨学科的研究中心，致力于 了解和治疗髓鞘疾病。

Project Summary / Abstract During peripheral nervous system (PNS) development, Schwann cells (SCs) undergo extensive Rac1- dependent cytoskeletal reorganization as they insert cytoplasmic extensions into axon bundles to radially sort, ensheath, and myelinate individual axons. Similarly, following peripheral nerve injury there is extensive Rac1- dependent actin polymerization around specialized regions known as Schmidt-Lantermann incisures (SLIs) as SCs differentiate into a repair phenotype2. The Feltri laboratory previously demonstrated that Rac1 activation in SCs is driven by engagement of α6β1 integrin with laminins, and that this is essential for peripheral nerve development4. Using a proteomic screen, we then identified Striatin-3 (Strn3) as a novel candidate Rac1 interactor in peripheral nerves. Striatin proteins (Strn1/3/4) function as core scaffolding components of STriatin- Interacting Phosphatase And Kinase (STRIPAK) complexes. STRIPAK complex members include the upstream Hippo pathway kinases Mst1/2 and the phosphatase PP2A-C, which dephosphorylates Mst1/2 to deactivate the Hippo pathway, permitting nuclear translocation of the mechanosensitive transcriptional co- activators Yap/Taz26,27,28. The Feltri laboratory previously demonstrated that Yap/Taz activity in SCs is also critical for myelinated peripheral nerve development25. Initial in vitro data suggest that knockdown of Strn3 in SCs impairs their ability to adhere to various substrates, decreases proliferation, and disrupts their association with axons. I then generated a mouse model with Strn3 specifically deleted in SCs (Strn3SCKO) and demonstrated early radial sorting and hypomyelination defects. Additionally, Strn3 null SCs isolated from these animals display reduced elongation and process extension on a laminin substrate. I thus hypothesize that Strn3 is required in SCs for peripheral nerve development and injury response via interaction with Rac1 and STRIPAK-mediated regulation of the Hippo pathway. To investigate this hypothesis, Strn3SCKO mice will be further characterized by morphological, functional, and electrophysiological measures during development and after injury. Cell and biochemical experiments in tissues and isolated Strn3 null SCs will determine if Strn3 indeed regulates SCs by interacting with Rac1, the STRIPAK complex, and the Hippo pathway. The long-term goal of this project is to understand the functions of Strn3 and the STRIPAK complex during peripheral nerve development and repair to advance the field of basic neuroscience and to identify new therapeutic targets with the potential to alleviate the burden of disease for patients suffering from demyelinating neuropathies and traumatic peripheral nerve injuries. This project will be integrated with a training plan that emphasizes scientific communication, problem solving, critical thinking, technical skills, and clinical experience. Research training will take place at the Hunter James Kelly Research Institute, an interdisciplinary research center devoted to understanding and treating diseases of myelin.