TGF-beta receptor sumoylation and cell behavior

描述(申请人提供)：自分泌转化生长因子-β信号在癌症进展中发挥关键作用，从而在早期癌变中起到肿瘤抑制因子的作用，并在刺激侵袭导致转移中发挥作用。大多数癌症对转化生长因子-β的反应失控，导致对转化生长因子-β的抗增殖反应失活。在某些情况下，这种放松管制与I型或II型转化生长因子-β受体的突变有关。SUMO化，即泛素样相扑蛋白的共价连接，是一种新兴的多种蛋白质的翻译后修饰。苏莫化的作用通常是不可预测的，似乎取决于目标蛋白。相扑相互作用蛋白的可能招募可能导致目标蛋白的蛋白质复合体的形成和功能性质的变化。苏莫化在很大程度上是对参与核功能的转录因子和蛋白质的修饰，而细胞表面受体的苏莫化尚未见报道。我们最近发现，I型转化生长因子-β受体(TbRI)是被总和基化的，这使我们假设，总和作用调节该受体的功能，从而调节转化生长因子-β信号和细胞对转化生长因子-β的反应。在确定了TBRI中的相加位点后，我们还发现了与转移性乳腺癌相关的TBRI中的一个点突变，这导致了对TBRI的相加缺失。这导致了一种假说，即TBRI的总和作用影响自分泌的转化生长因子-β信号，是癌症侵袭行为的决定因素。我们提出了三个目标来确定TBRI SUMO化的分子机制，以及它在细胞对转化生长因子-b的反应和体内癌细胞行为中的作用。目的1描述TBRI的相扑作用机制，包括寻找与之相关的E3相扑连接酶。目的2将研究TBRI总和甲基化对Smad和非Smad信号反应的影响，以及细胞对转化生长因子-b的增殖和侵袭反应。这一目标也应该确定“转移相关”的TBRI突变体、野生型TBRI和苏莫化缺陷的TBRI点突变之间在信号和细胞行为对转化生长因子-b的反应方面的功能差异。最后，目标3将确定TBRI苏莫化和“转移相关”的TBRI点突变对癌细胞行为和体内癌症进展的影响。这些研究将为研究转化生长因子-β受体苏莫化的机制、其在细胞对转化生长因子-β的反应中的作用以及在癌细胞行为和癌症进展中的作用提供基础。

DESCRIPTION (provided by applicant): Autocrine TGF-beta signaling plays key roles in cancer progression, thereby acting as tumor suppressor in early carcinogenesis, and in stimulating invasion leading to metastasis. Most carcinomas have a deregulated response to TGF-beta, leading to inactivation of the antiproliferative response to TGF- beta. In some cases this deregulation is associated with mutations in the type I or type II TGF-beta receptors. Sumoylation, i.e. the covalent attachment of a ubiquitin-like SUMO protein, is an emerging posttranslational modification of various proteins. The role of sumoylation is often unpredictable and seems to depend on the target protein. Possible recruitment of SUMO-interacting proteins may lead to changes in the protein complex formation and functional properties of the target protein. Sumoylation is largely characterized as a modification of transcription factors and proteins involved in nuclear functions, and sumoylation of cell surface receptors has not been reported. We recently discovered that the type I TGF- beta receptor, TbRI, is sumoylated, making us hypothesize that sumoylation regulates the function of this receptor, and consequently TGF-beta signaling and the cell's response to TGF-beta. After identifying the sumoylation site in TbRI, we also found that a point mutation in TbRI, which has been found in association with metastatic breast cancer, confers a lack of sumoylation to TbRI. This leads to the hypothesis that sumoylation of the TbRI affects autocrine TGF-beta signaling and is a determinant of the invasive behavior of carcinomas. We propose three aims to define the molecular mechanism of TbRI sumoylation and its role in the cellular responses to TGF-b and the behavior of cancer cells in vivo. Aim 1 will characterize the mechanism of sumoylation of TbRI, including a search to identify the responsible E3 SUMO ligase. Aim 2 will examine the effect of TbRI sumoylation on Smad and non-Smad signaling responses and the cell's proliferation and invasion responses to TGF-b. This Aim should also define functional differences between the "metastasis- associated" TbRI mutant, wild-type TbRI and a sumoylation-deficient TbRI point mutant in the signaling and cell behavior responses to TGF-b. Finally, Aim 3 will define the effect of TbRI sumoylation and of the "metastasis-associated" TbRI point mutation on the behavior of cancer cells and on cancer progression in vivo. The proposed studies should provide a basis for the characterization of the mechanism of the TGF- beta receptor sumoylation, its role in the cell's response to TGF-beta and in cancer cell behavior and cancer progression.