神经侵袭是胰腺癌转移的主要途径之一，也是预后较差胰腺癌患者的重要特征。Myosin9b（Myo9b）是Myosin家族成员，通过RhoGAP结构域抑制RhoA活性，亦可作为Slit/Robo信号通路下游分子参与肿瘤的发生发展。前期研究显示：Myo9b促进胰腺癌神经侵袭；RhoGAP通过Patch结构特异性识别RhoA；Myo9b的1361-1916氨基酸区域存在RhoGAP活性的自抑制。本项目运用X-射线晶体学解析Myo9b1361-1916蛋白及其与RhoA复合物的晶体结构，分析其内部结构及胰腺癌突变体对结构的影响；运用分子生物学方法验证Myo9b自抑制的调控机制；采用微流控芯片分析肿瘤细胞沿着神经侵袭的模式、速度及方向的改变，并筛选介导Myo9b促进胰腺癌神经侵袭的氨基酸；利用裸鼠致瘤模型探索Myo9b自抑制在胰腺癌转移中的功能意义。研究结果为开发有效的胰腺癌新型诊疗方法提供理论依据。

Neural invasion of pancreatic cancer cells is a critical route of cancer metastasis and represents a key feature of poor prognosis. Myosin9b (Myo9b), a member of class IX myosins, inhibits RhoA activity through its RhoGAP domain. Myo9b is identified as a downstream component of Slit/Robo signaling pathway, involving in tumorigenesis and tumor development. Our preliminary data demonstrate that Myo9b promotes neural invasion of pancreatic cancer cells. We have structurally characterized Myo9b RhoGAP and found that the Myo9b RhoGAP domain contains a unique patch that specifically recognizes RhoA. We identified that the sequence of 1361-1916 amino acids is required for Myo9b RhoGAP autoinhibition. Utilizing X-ray crystallography we are planning to solve the structure of Myo9b1361-1916 protein and its complex with RhoA, to analyze their internal structure and dysfunction of pancreatic cancer-related mutations. We use the molecular approaches to study the mechanisms underlying Myo9b RhoGAP autoinhibition. In addition, we propose to construct new microfluidic chip to elucidate the model, speed and direction of neural invasion of pancreatic cancer cells and screen the amino acids required for Myo9b-induced neural invasion of pancreatic cancer cells. Furthermore, we will study the role of Myo9b in pancreatic cancer metastasis with nude mice model. It will likely provide useful information for developing new diagnostic and therapeutic approaches for pancreatic cancer.