Understanding the Role of kB Ras Proteins in Signaling and Development

描述(由申请人提供)：本项目的目标是了解(B-Ras1和(B-Ras2)，一种不寻常的RAS样蛋白亚类成员是如何被调控的，以及它们如何反过来调控导致NF-(B和Ral)GTP酶的途径。这些蛋白最初是通过它们与I(B)蛋白的物理相互作用而被发现的，体外和过表达实验表明它们是核因子-(B)的抑制剂。然而，这些蛋白的真正生理作用尚不清楚。我们使用这两个(B-ras)基因敲除的初步结果表明，它们同时抑制了NF-(B)和Ral GTP酶途径。有趣的是，缺乏B-RAS蛋白的小鼠也会因肺发育缺陷而在围产期死亡。在这项研究提案中，我们打算提出以下问题。在目标1中，我们将研究(B-RAS实际上是如何调节核因子-(B)的。虽然影响I(B)的稳定性是一种可能的机制，但关于(B-RAS到底如何发挥作用的许多问题仍然没有答案。缺乏细胞的可用性(B-RAS将使我们能够以系统的方式探索潜在的机制。我们还将使用巨噬细胞中缺乏B-RAS的小鼠来研究包括感染性休克和胶原性关节炎在内的小鼠炎症模型。在目标2中，我们将询问(B-RAS如何调节RAL，并确定激活的RAL是否有助于NF-B的激活。我们将研究生长因子信号扰乱(B-RAS-RalGAP复合体的机制，并确定为什么与(B-RAS)结合抑制RalGAP的活性。我们还将测试(B-RAS)缺陷细胞中激活的RAL是否有助于核因子-(B)的激活。最后，在目标3中，我们将探索在(B-RAS)缺乏的动物中所看到的肺表型。我们将研究肺表面活性物质表达失调的机制，特别是核因子-B在这一过程中的作用。总而言之，这些研究将为这些进化上保守但神秘的RAS类蛋白质家族成员的生物学提供重要的新见解。

DESCRIPTION (provided by applicant): The goal of this project is to understand how (B-Ras1 and (B-Ras2, members of an unusual sub-class of Ras-like proteins, are regulated, and how they in turn regulate pathways leading to NF-(B and Ral GTPases. These proteins were originally discovered through their physical interaction with the I(B( protein, and in vitro and overexpression experiments indicated that they are inhibitors of NF-(B. However the true physiological role of these proteins has remained unclear. Our preliminary results using knock-outs of both (B-ras genes shows that they act to inhibit both NF-(B and Ral GTPase pathways. Interestingly, mice lacking (B-Ras proteins also die perinatally due to defects in lung development. In this research proposal we aim to ask the following questions. In Aim 1 we will study how (B-Ras actually regulates NF-(B. While affecting the stability of I(B( is a likely mechanism, many questions about exactly how (B-Ras functions remains unanswered. Availability of cells lacking (B-Ras will allow us to explore the underlying mechanism in a systematic manner. We will also use mice lacking (B-Ras in macrophages to study mouse models of inflammation including septic shock and collagen-induced arthritis. In Aim 2 we will ask how (B-Ras regulates Ral, and determine whether activated Ral contributes to NF-(B activation. We will study the mechanism by which growth factor signaling disrupts the (B-Ras-RalGAP complex, and determine why binding to (B-Ras inhibits the activity of RalGAP. We will also test whether the activated Ral in (B-Ras deficient cells contributes to NF-(B activation. Finally in Aim 3 we will explore the lung phenotype seen in the (B-Ras-deficient animals. We will study the mechanism of dysregulated surfactant expression, in particular the role of NF-(B in the process. In summary these studies will provide significant new insight into the biology of these evolutionarily conserved, yet enigmatic, members of this Ras-like family of proteins.