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

描述（由申请人提供）：脂肪酸合成酶（FAS）是一种主要的脂肪生成酶，而小窝蛋白-1 （Cav-1）是一种转运胆固醇和调节信号转导的膜蛋白，在前列腺癌（PCa）的人和动物模型中都过表达。这两种蛋白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结果，证明FAS和Cav-1在PCa细胞中相互作用，并且FAS是一种细胞质蛋白，可以被诱导与富含胆固醇的脂质筏膜结合。进一步的数据表明，在缺乏棕榈酰化的Cav-1突变体中，这两种蛋白之间的复合物形成受损。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，并且EGFR激活侵袭性PCa细胞导致快速形成膜囊泡，其中包含脂筏成分以及膜Cav-1。由于Cav-1是侵袭性前列腺癌的循环标志物，这些分泌的囊泡可能与转移性传播有关。最后，我们已经获得证据表明Cav-1和FAS在人类肿瘤中位于相似的亚细胞位置，允许两种蛋白在体内合作。

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.