Role of TGFBeta in Microtubule Dynamics

TGF β家族的信号分子成员普遍存在于脊椎动物和无脊椎动物中，并在许多基本的稳态、发育和生物学过程中发挥关键作用。 迄今为止，所有已知的信号通路激活TGF β刺激转录反应。 鉴于TGF β下游细胞反应的多样性，这种生长抑制多肽可能是其他重要细胞功能所必需的。 我们克隆并测序了一种新的成分，称为km 23，它直接与TGF β受体相互作用并被其磷酸化。 基于其与数据库中相关序列的同源性，我们提出TGF β介导一种新的信号传导途径，该途径对沿着微管（MT）的细胞内转运至关重要。 有趣的是，我们发现9个卵巢肿瘤序列中有5个突变了km 23中的一个关键位点。虽然MT动力学的改变已被证明在癌症发展和特定化疗药物的作用机制中起作用，但在负端MT动力学的控制和天然生长调节剂如TGF β之间没有注意到任何联系。 此外，没有一种抗癌药物似乎能特异性调节负端MT功能。 基于我们的初步数据和本文提出的研究，我们将描绘这个新途径的步骤，并确定它是否以及如何影响其他主要已知的TGF β信号通路，Mapks和Smads。 将分析正常组织细胞和来自卵巢癌、乳腺癌和结肠癌进展的各个阶段的组织细胞的激光捕获显微切割，以确定km 23突变发生的阶段。 分子分析研究将解决当TGF β受体或信号传导途径被修饰时km 23表达和/或活性改变的假设。 最终，我们将提供证据，证明km 23是一个新的分子靶点的癌症药物发现。

Members of the TGFbeta family of signaling molecules are found ubiquitously in vertebrates and invertebrates and have critical roles in many essential homeostatic, developmental, and biological processes. To date, all of the known signaling pathways activated by TGFbeta stimulate transcriptional responses. In light of the diversity of TGFbeta's downstream cellular responses, this growth inhibitory polypeptide is likely to be essential for other important cellular functions. We have cloned and sequenced a novel component, termed km23, that directly interacts with and is phosphorylated by the TGFbeta receptors. Based upon its homology to related sequences in the database, we propose that TGFbeta mediates a novel signaling pathway which is critical for intracellular transport along microtubules (MT's). Of interest, we found that a critical site in km23 is mutated in 5 out of 9 ovarian tumor sequences. Although alterations in MT dynamics have been shown to play a role in both cancer development and the mechanism of action of specific chemotherapeutic agents, no link has been noted between control of minus-end MT dynamics and a natural growth regulator such as TGFbeta. Moreover, none of the anti-cancer agents appear to specifically regulate minus-end MT functions. Based upon our preliminary data and the studies proposed herein, we will delineate the steps in this novel pathway, and determine if and how it impinges upon the other major known TGFbeta signaling pathways, the Mapks and the Smads. Laser capture microdissection of normal tissue cells and of tissue cells from various stages of progression of ovarian, breast, and colon cancer will be analyzed to determine the stage at which km23 mutations occur. Molecular profiling studies will address the hypothesis that km23 expression and/or activity is altered when TGFbeta receptors or signaling pathways are modified. Ultimately, we will provide evidence that km23 is a novel molecular target for cancer drug discovery.