The Macropinosome: Uncovering the Molecular Anatomy of an Oncogene-driven Organelle

项目摘要 作为癌症中发生的代谢重编程的一个不可或缺的方面，致癌KRAS突变驱动 刺激巨胞饮作用，一种介导非选择性液相摄取的内吞作用。使用 KRAS驱动的胰腺导管腺癌（PDAC）模型，我们首次证明， 巨胞饮作用在肿瘤细胞中起营养获取途径的作用。巨胞饮作用触发 细胞外蛋白通过称为巨胞饮体的离散内吞囊泡内化。传入 蛋白质货物是溶酶体依赖性降解的目标，引起氨基酸的细胞内释放。 这些蛋白质衍生的氨基酸通过贡献于细胞内氨基酸库来支持代谢适应性， 以及中心碳代谢物的生物合成。这样，巨胞饮作用代表了一种新的 肿瘤细胞用来在肿瘤的营养不良条件下生存的氨基酸供应途径 微环境虽然在癌症中驱动巨胞饮的信号转导事件的原理 虽然大胞饮体已经出现，但它本身的详细图像还没有。借助纳米技术，我们 已经开发了从PDAC细胞中分离大胞饮体的纯级分的方法。具有 纯化大胞饮体的能力，我们现在处于独特的地位，受益于大规模蛋白质组学， 可以提供这个重要细胞器的全貌。通过阐明KRAS驱动的 通过对巨胞饮体的研究，我们将进一步了解巨胞饮在癌症中的调节和功能。 此外，更清楚地了解大胞饮体将使我们更好地利用这一途径 治疗并为患者带来突破。

PROJECT SUMMARY As an integral aspect of the metabolic reprogramming that occurs in cancer, oncogenic KRAS mutations drive the stimulation of macropinocytosis, a type of endocytosis that mediates nonselective fluid-phase uptake. Using KRAS-driven models of pancreatic ductal adenocarcinoma (PDAC), we were the first to demonstrate that macropinocytosis functions in tumor cells as a nutrient acquisition pathway. Macropinocytosis triggers the internalization of extracellular proteins via discrete endocytic vesicles called macropinosomes. The incoming protein cargo is targeted for lysosome-dependent degradation, causing the intracellular release of amino acids. These protein-derived amino acids support metabolic fitness by contributing to the intracellular amino acid pools, as well as to the biosynthesis of central carbon metabolites. In this way, macropinocytosis represents a novel amino acid supply route that tumor cells use to survive the nutrient-poor conditions of the tumor microenvironment. While the tenets of the signal transduction events that drive macropinocytosis in cancer have emerged, a detailed picture of the macropinosome itself is not yet available. With the aid of nanotechnology, we have developed methodology to isolate a pure fraction of macropinosomes from PDAC cells. Having the capability to purify macropinosomes, we are now uniquely positioned to benefit from largescale proteomics that can provide a broad picture of this important organelle. By elucidating the molecular anatomy of KRAS-driven macropinosomes, we will gain further insight into the regulation and function of macropinocytosis in cancer. Moreover, having a clearer picture of the macropinosome will make us better positioned to exploit this pathway therapeutically and deliver breakthroughs to patients.