PROJ 11: RB PROTEIN INACTIVATION RESULTS IN A METABOLIC SHIFT TOWARDS GLUTAMINE

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 视网膜母细胞瘤蛋白(Rb)是最早被发现的肿瘤抑制因子，通过调控细胞周期进程中关键基因的表达，在调节细胞增殖中发挥重要作用。虽然研究Rb功能在肿瘤发生中的作用的大部分工作都集中在细胞周期调节上，但很明显，Rb可能介导了一系列广泛的生化途径，特别是那些涉及细胞代谢的途径。代谢失调现在被认为是肿瘤细胞的一个标志，表现在葡萄糖利用的增加以及对谷氨酰胺消耗的依赖。具体地说，谷氨酰胺用于满足能量生产、核苷酸和氨基酸合成以及谷胱甘肽生产的代谢需求。尽管特定的酶与肿瘤细胞中的谷氨酰胺成瘾现象有关，但促进这种代谢转变的确切信号机制和致癌因素尚未完全描述。使用基因耗尽的Rb基因敲除的小鼠胚胎成纤维细胞，我们证明了Rb的失活特定地导致了对细胞生长和生存对谷氨酰胺的依赖。我们的数据进一步表明，这种代谢变化可能是通过c-Myc依赖的途径进行的，因为Rb的枯竭增加了c-Myc转录和蛋白水平。在这项提议完成时，我们希望能够完全描述RB对谷氨酰胺代谢的调节，并在这样做的过程中提供对肿瘤表型的性质的更多了解，特别是关于RB网络的破坏。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Retinoblastoma protein (Rb), the first described tumor suppressor, plays a vital role in regulating cell proliferation by modulating the expression of key genes involved in cell cycle progression. Although the majority of work investigating the role of Rb function in tumorigenesis has focused on cell cycle regulation, it is clear that Rb may mediate a broad spectrum of biochemical pathways, particularly those involved in cellular metabolism. Dysregulated metabolism is now considered a hallmark of tumorigenic cells, as evident by increased glucose utilization as well as a dependence on glutamine consumption. Specifically, glutamine serves to fulfill the metabolic need for energy production, nucleotide and amino acid synthesis, and the production of glutathione. Even though specific enzymes have been implicated in this phenomenon of "glutamine addiction" in tumor cells, the precise signaling mechanisms and the oncogenic factors that facilitate this metabolic shift have yet to be fully described. Using genetically depleted Rb knockout mouse embryonic fibroblasts, we demonstrate that Rb inactivation specifically leads to a dependence on glutamine for cell growth and survival. Our data further suggest that this metabolic shift may be through a c-Myc dependent pathway, as Rb depletion increases both c-Myc transcript and protein levels. At the completion of this proposal, we expect to have fully characterized the regulation of glutamine metabolism by Rb, and in doing so provide a greater understanding of the nature of the neoplastic phenotype, especially with respect to disruption of the Rb network.