Hypoxia and the control of protein synthesis and homeostasis in Drosophila

动物经常生活在环境含氧量波动的环境中，因此，它们必须根据氧气供应的变化来协调新陈代谢。特别是在缺氧的情况下，动物需要改变它们的新陈代谢，以限制消耗大量能量的合成代谢过程，维持体内平衡，促进生存。这种代谢控制的缺陷会损害细胞和组织的稳态，并可能导致死亡。******一种代谢策略是抑制蛋白质合成。考虑到蛋白质合成占细胞ATP使用的三分之一以上，这种抑制有助于限制能量消耗。选择性翻译控制也提供了一种机制，将基因表达限制为应激反应所需的蛋白质。缺氧可以抑制翻译，其机制几乎都是在细胞培养中研究的。目前尚不清楚的是，在动物缺氧时，翻译控制如何促进细胞和组织稳态的体内调节。******这个NSERC项目的目标是研究缺氧如何调节mRNA翻译来控制生物体生理和生存，以果蝇为模型。果蝇可以忍受长时间的低氧而不影响生存能力。我们的项目有三个主要目的来研究这种显著的缺氧耐受性的分子基础：***目的1：研究PERK对缺氧耐受性的影响。我们的数据表明，缺氧通过激活PERK激酶来抑制翻译，PERK激酶磷酸化并抑制eIF2alpha，这是一个重要的翻译起始因子。此外，我们发现PERK突变体不能耐受缺氧。我们将测试PERK是否通过细胞自主和/或细胞非自主机制对翻译和生物体存活产生这些影响。******目的2：探讨PERK对缺氧时胰岛素信号传导的影响。胰岛素信号的抑制是无脊椎动物对应激的保守调节反应。我们发现缺氧抑制了果蝇的全身胰岛素信号。我们将测试这是否是PERK调节缺氧耐受性的机制。******目的3：确定新的缺氧耐受性调节因子。这个长期目标将使用多体分析来鉴定缺氧诱导mRNA翻译的基因。然后，我们将研究这些基因作为缺氧耐受性的潜在调节因子。这些目标将为我们的项目提供新的、长期的研究途径。******这项NSERC拨款将建立一个新的，令人兴奋的研究项目，以帮助了解细胞，组织和生物体如何耐受缺氧，维持体内平衡和生存。＊＊＊＊＊＊＊＊

Animals often live in conditions where environmental oxygen levels fluctuate As a result, they must coordinate their metabolism with changes in oxygen availability. In particular, upon oxygen deprivation, or hypoxia, animals need to alter their metabolism to limit energetically costly anabolic processes, maintain homeostasis and promote survival. Defects in this metabolic control can impair cell and tissue homeostasis and can lead to lethality.******One metabolic strategy is suppression of protein synthesis. Given that protein synthesis accounts for over a third of cellular ATP use, this suppression helps to restrict energy expenditure. Selective translational control also provides a mechanism to limit gene expression to proteins required for stress responses. Hypoxia can suppress translation and the mechanisms have been studied almost exclusively in cell culture. What is not clear is how translational control contributes to in vivo regulation of cell and tissue homeostasis in animals during hypoxia. ******The goal of this NSERC program is to examine how hypoxia regulates mRNA translation to control organismal physiology and survival, using Drosophila as a model. Drosophila can tolerate prolonged periods of low oxygen with no effects on viability. Our program has three main objectives to examine the molecular basis for this striking hypoxia tolerance:***Objective 1: To examine the effects of PERK on hypoxia tolerance. Our data suggest that hypoxia suppress translation by activating PERK kinase, which phosphorylates and inhibits eIF2alpha, an essential translation initiation factor. Moreover, we find that PERK mutants are unable to tolerate hypoxia. We will test whether PERK exerts these effects on translation and organismal survival via cell autonomous and /or cell non-autonomous mechanisms.******Objective 2: To examine effects of PERK on insulin signaling in hypoxia. Suppression of insulin signaling is a conserved regulatory response to stress in invertebrates. We find that hypoxia inhibits systemic insulin signaling in Drosophila. We will test whether this is a mechanism used by PERK to regulate hypoxia tolerance. ******Objective 3: To identify new regulators of hypoxia tolerance. This longer-term objective will use polysome profiling to identify genes whose mRNA translation is induced by hypoxia. We will then investigate these genes as potential regulators of hypoxia tolerance. These objective will provide new, long-term avenues of investigation for our program.******This NSERC grant will establish a new, exciting program of research to help understand how cells, tissues and organisms can tolerate hypoxia and maintain homeostasis and survival. ********