Role of TGFBeta in Microtubule Dynamics

tgf β信号分子家族成员在脊椎动物和无脊椎动物中普遍存在，在许多重要的体内平衡、发育和生物过程中起着关键作用。迄今为止，所有已知的TGFbeta激活的信号通路都能刺激转录反应。鉴于TGFbeta下游细胞反应的多样性，这种生长抑制多肽可能对其他重要的细胞功能至关重要。我们克隆并测序了一种称为km23的新成分，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TGFbeta介导了一种新的信号通路，该通路对沿微管（MT）的细胞内运输至关重要。有趣的是，我们发现km23的一个关键位点在9个卵巢肿瘤序列中有5个发生突变。尽管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发挥作用，但尚未注意到负端MT动力学的控制与tgf - β等天然生长调节剂之间的联系。此外，没有一种抗癌药物似乎能特异性调节-末端MT功能。基于我们的初步数据和本文提出的研究，我们将描述这一新途径的步骤，并确定它是否以及如何影响其他主要的已知TGFbeta信号通路，Mapks和Smads。将对正常组织细胞和卵巢癌、乳腺癌和结肠癌不同发展阶段的组织细胞进行激光捕获显微解剖，以确定km23突变发生的阶段。分子分析研究将解决当tgfβ受体或信号通路被改变时km23表达和/或活性被改变的假设。最终，我们将提供证据证明km23是癌症药物发现的新分子靶点。

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.