Fatty Acid Synthase, Caveolin-1 and Membrane Microdomains in Prostate Cancer

描述(申请人提供)：在前列腺癌(PCa)的人和动物模型中，主要的脂肪生成酶脂肪酸合成酶(Fas)和负责运输胆固醇和调节信号转导的膜蛋白小窝蛋白-1(Cav-1)都过度表达。这两种蛋白都在前列腺癌细胞中发挥致癌作用。现在，我们第一次获得了初步的结果，证明了Fas和Cav-1在前列腺癌细胞中相互作用，并且Fas，一种胞浆蛋白，可以被诱导与富含胆固醇的脂筏膜相关联。进一步的数据表明，在棕榈酰化缺陷的Cav-1突变体中，这两种蛋白质之间的复合体形成受到损害。我们也有证据表明Cav-1棕榈酰化可能在信号转导中发挥作用，侵袭性PCa细胞的EGFR激活导致含有脂筏成分的膜泡和膜Cav-1的快速形成。由于Cav-1是侵袭性前列腺癌的循环标志物，这些分泌的小泡可能与转移扩散有关。最后，我们获得的证据表明，Cav-1和Fas在人类肿瘤中存在相似的亚细胞位置，允许这两种蛋白在体内进行合作。 在本项目中概述的实验中，我们将挑战以下总体假设：Cav-1和Fas合作改变脂筏隔室，有助于形成更富含胆固醇和饱和脂肪酸的膜环境。这些细胞膜的变化可能对肿瘤细胞的生存、生长和其他恶性行为产生重要的功能后果。CAV-1和Fas的共存也可能是一个有用的预后指标。本研究的具体目的是：目的1：确定脂肪酸合成酶和小窝蛋白-1是否协同改变前列腺癌细胞的膜组成和膜动力学。我们将验证这样的假设：(I)c-Src的激活决定了Fas在膜上的定位，Fas和Cav-1共同定位于质膜和/或其他细胞膜，(Ii)Fas和Cav-1改变了膜的组成和动力学，(Iii)Fas在蛋白质棕榈酰化过程中发挥了作用。目的：探讨脂肪酸合酶与小窝蛋白-1在前列腺癌细胞膜上共定位的生物学意义。我们将检验假设：(I)Fas在膜上的定位是致癌的。(Ii)Fas和Cav-1的共同定位根据生物学行为对人类肿瘤进行分层，(Iii)Fas和Cav-1协同调节含有Cav-1的囊泡的分泌。我们相信，这些实验将对Cav-1和Fas在前列腺癌中的作用提供新的见解，并将扩大我们对膜脂变化的性质、范围和生物学意义的理解，这些变化与前列腺癌和可能的其他恶性肿瘤的发生有关。

DESCRIPTION (provided by applicant): Fatty Acid Synthase (FAS), a major lipogenic enzyme, and Caveolin-1 (Cav-1), a membrane protein that transports cholesterol and regulates signal transduction, are both over-expressed in human and animal models of prostate cancer (PCa). Both proteins exert an oncogenic function in PCa cells. Now, for the first time, we have acquired preliminary results demonstrating that FAS and Cav-1 interact in PCa cells and that FAS, a cytosolic protein, can be induced to associate with cholesterol-rich, lipid raft membranes. Further data show that complex formation between the two proteins is impaired in a Cav-1 mutant deficient in palmitoylation. We also have evidence suggesting that Cav-1 palmitoylation may play a role in signal transduction and that EGFR activation of aggressive PCa cells results in rapid formation of membrane vesicles that contain lipid raft components as well as membrane Cav-1. Because Cav-1 is a circulating marker for aggressive PCa, these secreted vesicles may be linked to metastatic dissemination. Finally, we have acquired evidence indicating that Cav-1 and FAS inhabit similar subcellular locations in human tumors, allowing for cooperation between the two proteins in vivo. In the experiments outlined in this project, we will challenge the following overall hypothesis: Cav-1 and FAS collaborate to alter the lipid raft compartment, contributing to a membrane environment that is richer in cholesterol and saturated fatty acids. These changes in cell membranes may exert important functional consequences on tumor cell survival, growth and other malignant behaviors. Cav-1 and FAS colocalization might also be a useful prognostic indicator. The specific aims of the study are: Aim 1: Determine whether Fatty Acid Synthase and Caveolin-1 collaborate to alter membrane composition and membrane dynamics in PCa cells. We will test the hypotheses that: (i) Activation of c-Src determines FAS localization at the membrane, and FAS and Cav-1 co-localize at the plasma membrane and/or at other cellular membranes, (ii) FAS and Cav-1 alter membrane composition and dynamics, (iii) FAS plays a role in protein palmitoylation. Aim 2: Determine the biological significance of Fatty Acid Synthase and Caveolin-1 colocalization at cell membranes in PCa. We will test the hypotheses that: (i) FAS localization at the membrane is oncogenic. (ii) FAS and Cav-1 co-localization stratifies human tumors with respect to biological behavior, (iii) FAS and Cav-1 collaborate to mediate the secretion of Cav-1-containing vesicles. We believe these experiments will provide new insights into the role of Cav-1 and FAS in PCa and will expand our understanding of the nature, the extent, and the biological significance of membrane lipid changes relevant to oncogenesis in PCa and possibly other malignancies.