HIG2 and Hypoxic Regulation of Protein Synthesis

描述(由申请人提供)： 缺氧是实体瘤特有的一种病理生理应激，实验和临床研究均表明，缺氧可影响肿瘤的侵袭性、转移潜能和对治疗的反应。这些现象的机制尚未确定，但被认为至少部分依赖于低氧诱导的基因和蛋白质表达变化。研究人员已经确定了低氧应激反应级联反应的许多组成部分，从低氧感觉开始，到转录变化，再到蛋白质表达变化和翻译后蛋白质修饰。不能启动新的低氧反应基因转录的肿瘤细胞在模型肿瘤中生长不良(HIF基因敲除)。同样，不表达缺氧靶蛋白血管内皮生长因子的细胞在模型肿瘤中生长也很差(血管内皮生长因子基因敲除)。因此，可以得出结论，研究应激反应级联反应的其他组成部分是合理的，因为阻断它们可能对肿瘤生长产生同样深远的影响。我们建议调查HIG2是否可以影响应激依赖的蛋白质合成，因为我们有证据表明HIG2与缺氧期间的翻译机制有关。我们先前已经发现HIG2是一种新的63个氨基酸的蛋白质，在各种正常细胞和肿瘤细胞系中被低氧强烈诱导。我们现在证明HIG2蛋白与细胞质成员共定位 “应激颗粒”。应激颗粒已被证明可以调节热休克反应中的蛋白质翻译，我们认为它们在低氧时具有类似的功能。这项拨款建议是基于这样一个假设，即HIG2通过与应激颗粒的成分相关联，在低氧期间调节蛋白质合成方面发挥重要作用。为了解决这一假设，我们建议1)确定HIG2靶向应激颗粒的机制，2)确定HIG2在缺氧过程中的结合伙伴，3)建立HIG2在应激颗粒中在肿瘤形成过程中的功能意义。这些实验应该确定HIG2是否对低氧依赖的翻译控制是必要的，以及这种控制对人类肿瘤低氧区域内细胞的生存有多重要。

DESCRIPTION (provided by applicant): Hypoxia is a unique patho-physiologic stress of the solid tumor that has been shown both experimentally and clinically to influence tumor aggressiveness, metastatic potential and response to therapy. The mechanisms for these phenomena have not been determined, but are thought to be at least partially dependent upon gene and protein expression changes induced by hypoxia. Investigators have identified many components of the hypoxic stress response cascade starting from hypoxic sensing, to transcriptional changes, to protein expression changes and post-translational protein modifications. Tumor cells that are unable to start new hypoxia-responsive mRNA transcription grow poorly in model tumors (HIF knockouts). Likewise, cells that fail to express the hypoxic target protein vascular endothelial growth factor also grow poorly in model tumors (VEGF knockouts). The conclusion can therefore be made that studying other components of the stress response cascade is reasonable, because blocking them could have similarly profound impact on tumor growth. We propose to investigate if HIG2 can influence stress-dependent protein synthesis because we have evidence that HIG2 is associated with translational machinery during hypoxia. We have previously identified HIG2 as a novel 63 amino acid proteins that is robustly induced by hypoxia in a wide variety of normal cells and tumor cell lines. We now show that the HIG2 protein co-localizes with members of the cytoplasmic "Stress granule". Stress granules have been shown to regulate protein translation in response to heat shock, and we suggest that they serve a similar function during hypoxia. This grant proposal is based upon the hypothesis that HIG2 plays an important function in regulating protein synthesis during hypoxia through its association with components of the stress granule. To address this hypothesis, we propose to 1) Identify the mechanism by which HIG2 is targeted to the stress granule, 2) Determine binding partners for HIG2 during hypoxia and 3) Establish the functional significance of HIG2 within the stress granule during tumor formation. These experiments should determine if HIG2 is necessary for hypoxia-dependent translational control, and how important this control is to the survival of ceils within the hypoxic regions of human tumors.