Molecular mechanisms initiating cell migrations in Caonorhabditis elegans

描述(申请人提供)：癌症的进展和转移需要细胞极性的改变，从而导致细胞粘附性和运动性的改变。粘附性和运动性由极化的肌动蛋白细胞骨架调节。我们的长期目标是确定在健康生长和疾病期间使肌动蛋白极化的机制。我们使用模式生物秀丽线虫来研究胚胎发育过程中的细胞运动。利用基因敲除突变体，我们已经证明，肌动蛋白成核调节因子包括GTPase CED-10/rac1，肌动蛋白成核Arp2/3复合体的任何成分，或其激活剂WAVE/SCAR复合体，都会导致相同的表型：胚胎细胞迁移失败，形态发生和上皮极性改变。保守的波/疤痕复合体的突变与包括侵袭性转移癌在内的癌症有关。例如，WAVE2在恶性肺癌和转移性结直肠癌中错误表达(Semba等人。2006年；岩屋等人。2007)。然而，肌动蛋白细胞骨架是如何在正常生长过程中被调控的，还是在转移过程中被错误调控的，目前还不是很清楚。我们最近发现了在胚胎细胞迁移过程中调节rac1/CED-10和WAVE/SCAR的细胞外信号。有了这些上游信号，我们想要解决以下关于外部信号如何极化F-肌动蛋白的假说：目的/假设：我们假设，质膜上的不同信号激活WAVE/SCAR复合体以促进细胞极化，我们已经发现的细胞外受体在细胞间信号传递和细胞内信号传递中发挥重要作用。具体目的：(1)建立ECM(细胞外基质)受体通过调节顶端交界处的波来支持上皮细胞迁移的模型。(2)确定组织之间的信号是否组织了表皮细胞中的F-肌动蛋白。(3)验证ECM受体通过调节特定RAC间隙发挥作用的模型。研究设计：在目标1中，我们使用我们的体内系统来确定波是如何被招募到心尖连接的，以及它在那里起到了什么作用，以更好地了解波/疤痕是如何促进细胞极性的。在目标2中，我们创建了一个体内模型，用于测试组织如何检测邻近组织中F-肌动蛋白的极化状态。在目标3中，我们使用遗传学和生物化学来鉴定在胚胎形态发生过程中调节RAC/CED-10的GAP蛋白。临床意义：我们在秀丽线虫中研究的基因之一WAVE3的人类同源基因被认为是高级别、三阴性乳腺癌的生物标记物(Kulkarni等人，2012年)，并与浸润性前列腺癌和结肠癌有关(Fernando等人，2010年；张等人，2012年)。了解在细胞迁移过程中通过波/疤痕复合体调节肌动蛋白动态的分子不仅有助于我们理解正常发育，而且可能为人类疾病中肌动蛋白调控的改变提供新的生物标志物。

DESCRIPTION (provided by applicant): Cancer progression and metastasis require changes in cell polarity that drives changes in cellular adhesion and motility. Adhesion and motility are regulated by the polarized actin cytoskeleton. Our long-term goal is to identify the mechanisms that polarize actin during healthy growth and during disease. We have used the model organism C. elegans to study cell movements during embryonic development. Using knockout mutants we have shown that loss of regulators of actin nucleation including the GTPase CED-10/Rac1, any component of the actin nucleating Arp2/3 complex, or of its activator, the WAVE/SCAR complex, results in the same phenotype: failure in embryonic cell migrations, morphogenesis and altered epithelial polarity. Mutations in the conserved WAVE/SCAR complex are associated with cancers including aggressive metastatic cancers. For example, WAVE2 is misexpressed in malignant lung cancers and metastatic colorectal cancers (Semba et al. 2006; Iwaya et al. 2007). However, how the actin cytoskeleton is regulated during normal growth or misregulated during metastasis is not well understood. We have recently identified extracellular signals that regulate Rac1/CED-10 and WAVE/SCAR during embryonic cell migrations. With these upstream signals in hand we want to address the following hypothesis for how outside signals polarize F-actin: Objective/Hypothesis: We hypothesize that distinct signals at the plasma membrane activate the WAVE/SCAR complex to promote cell polarization, and that the extracellular receptors we have identified play an important role in both signaling between cells, and in transmitting signals intracellularly to polarize cellular F-actin. Specific Aims: (1) To tes the model that ECM (extra cellular matrix) receptors support epithelial cell migrations by regulating WAVE at the apical junction. (2) To determine if signaling between tissues organizes F-actin in epidermal cells. (3) To test the model that ECM receptors act through the regulation of specific Rac GAPs. Study Design: In Aim 1 we use our in vivo system to determine both how WAVE is recruited to apical junction and what role it plays there to better understand how WAVE/SCAR promotes cell polarity. In Aim 2 we create an in vivo model for testing how tissues detect the polarized state of F-actin in neighboring tissues. In Aim 3 we use genetics and biochemistry to identify the GAP proteins that regulate Rac/CED-10 during embryonic morphogenesis. Clinical relevance: The human homolog of one of the genes we study in C. elegans, WAVE3, is considered a biomarker for high grade, triple negative breast cancer (Kulkarni et al., 2012) and is associated with invasive prostate and colon cancers (Fernando et al., 2010; Zhang et al., 2012). Understanding the molecules that regulate actin dynamics through the WAVE/SCAR complex during cell migrations will not only enlighten our understanding of normal development but could suggest new biomarkers for altered actin regulation in human disease.