K-Ras4A Trafficking and Signaling

描述(申请人提供)：RAS癌基因是人类癌症中最常见的突变。RAS蛋白是一种小的GTP酶，它控制着生长、增殖和生存的关键细胞通路，其调节失调广泛地与癌症有关。的 KRAS中的三个RAS基因突变是人类肿瘤中最常见的。KRAS基因编码的剪接变异体有两种：K-Ras4A和K-Ras4B。尽管K-Ras4A亚型作为原始的K-RAS病毒癌基因具有重要意义，但人们已经做了大量的工作来研究RAS的生物学特性，但绝大多数研究都忽略了它。最近的研究已经开始暗示K-Ras4A在癌症中的作用比之前假设的更大，但对K-Ras4A蛋白仍然知之甚少。这项拟议的工作试图通过阐明K-Ras4A的细胞生物学来纠正这一点，并有两个特定的目标。首先，我们将研究K-Ras4A本地化的靶向信号及其调控方式。由于RAS信号需要膜结合，因此确定K-Ras4A是如何在细胞内运输的，对于了解它是如何发挥信号作用至关重要。我们假设K-Ras4A通过棕榈酰化和多碱结合的相互作用被运输到质膜，并将用活细胞成像研究来验证这一点。其次，我们将探讨K-Ras4A在肿瘤发生中的作用。我们将研究K-Ras4A在人类癌细胞系中的相对表达水平和对生存和肿瘤发生的依赖性，并研究两种K-Ras亚型的相对信号输出。我们从这些研究中的发现将提供对这一难以捉摸的异构体的更好的理解，并有助于我们对RAS生物学的了解。这项工作也将对K-RAS驱动的抗癌药物的设计和开发具有重要意义。

DESCRIPTION (provided by applicant): Ras oncogenes are the most frequently mutated in human cancer. The Ras proteins are small GTPases that control critical cellular pathways for growth, proliferation, and survival, dysregulation of which is implicated extensively in cancer. Of the three Ras genes, mutations in KRAS are the most frequently found in human tumors. There are two splice variants encoded by the KRAS gene: K-Ras4A and K-Ras4B. Much work has been done to characterize Ras biology, but the vast majority of studies have overlooked the K-Ras4A isoform, despite its importance as the original K-Ras viral oncogene. Recent studies have begun to implicate a greater role for K-Ras4A in cancer than previously assumed, but little is still known about the K-Ras4A protein. This proposed work seeks to rectify this by elucidating the cell biology of K- Ras4A with two specific aims. First, we will investigate the targeting signas for K-Ras4A localization and how they are regulated. As membrane association is required for Ras signaling, determining how K-Ras4A is trafficked within the cell is critical in understanding how it exerts its signaling effects. We hypothesize that K-Ras4A is trafficked to the plasma membrane by combined palmitoylation and polybasic interactions, and will test this with live cell imaging studies. Second, we will explore the role that K-Ras4A plays in mediating oncogenesis. We will examine in human cancer cell lines the relative expression levels and dependence on K-Ras4A for survival and tumorigenesis, and study the relative signaling outputs of the two K-Ras isoforms. Our findings from these studies will provide a better understanding of this elusive isoform and contribute to our knowledge of Ras biology. This work will also have significant implications for the design and development of drugs against cancers driven by K-Ras.