Mechanism of heat-induced cell death and its regulation by the molecular chaperone protein Hsp70

细胞对应激刺激的反应是激活一种进化上保守的‘热休克反应’，导致热休克蛋白的产生增加。这些蛋白质是一种防御机制的一部分，该机制可以限制蛋白质损伤的程度，从而允许细胞和生物体在通常会致命的温度压力下生存下来。热休克蛋白作为分子伴侣发挥作用，因为它们帮助蛋白质折叠，而蛋白质折叠会被高温暴露和其他破坏蛋白质的压力破坏。应激诱导的细胞死亡是通过一种被称为细胞凋亡的受调控的细胞清除过程发生的。我们已经证明，主要的热休克蛋白Hsp70可以防止应激诱导的细胞凋亡。我的研究计划的长期目标是确定高温如何触发细胞凋亡，以及主要的热诱导蛋白Hsp70如何阻止这种情况发生。我的假设是，热应激影响特定的Bcl-2家族蛋白的活性，这些蛋白是调节细胞凋亡的核心。本研究的目的是确定高温对促凋亡蛋白Bcl-2家族蛋白NOXA的表达、稳定性、翻译后修饰和相互作用伙伴的影响。另一个相关的目标是确定导致应激诱导的细胞凋亡激活的热敏靶标的性质。具体地说，我们将(I)确定磷酸化在控制Noxa蛋白水平中的作用及其与抗凋亡的Bcl-2家族蛋白Mcl-1的相互作用，(Ii)通过研究microRNAs在调控Noxa mRNA转录水平中的作用来确定控制热诱导Noxa mRNA积累的机制，以及(Iii)通过检测在冷血脊椎动物(蛙)细胞中表达的人Bax蛋白的温度激活谱来确定促凋亡的Bax家族蛋白Bax是否直接被温度升高激活。这项工作将促进我们对细胞应激如何触发细胞凋亡以及Hsp70如何抑制这一过程的理解。因此，这些研究将提供对细胞和有机体在压力环境中适应和坚持的基本能力的洞察。

Cells respond to stressful stimuli by activating an evolutionarily conserved 'heat shock response' that results in the increased production of heat shock proteins. These proteins are part of a defense mechanism that acts to limit the extent of protein damage and thereby allows cells and organisms to survive temperature stresses that would normally be lethal. The heat shock proteins function as molecular chaperones in that they assist in protein folding, which is disrupted by elevated temperature exposure as well as other protein-damaging stresses. Stress-induced cell death occurs through a regulated process of cell elimination known as apoptosis. We have demonstrated that the major heat-shock protein, Hsp70 prevents stress-induced apoptosis. The long-term goal of my research program is to determine how hyperthermia triggers apoptosis and how the major heat-inducible protein, Hsp70, prevents this from occurring. My hypothesis is that heat stress affects the activity of specific Bcl-2 family proteins, which are central to the regulation of apoptosis. The objectives of this proposal are to determine the effect of hyperthermia on the expression, stability, post-translational modifications and interaction partners of the pro-apoptotic Bcl-2 family protein Noxa. An additional and related goal is to determine the nature of the heat-sensitive target that leads to the activation of stress-induced apoptosis. Specifically, we will (i) determine the role of phosphorylation in the control of Noxa protein levels and its interaction with the anti-apoptotic Bcl-2 family protein Mcl-1, (ii) determine the mechanism controlling heat-induced Noxa mRNA accumulation by examining the role of microRNAs in the regulation of Noxa mRNA transcript levels and (iii) determine whether the pro-apoptotic Bcl-2 family protein Bax is directly activated by temperature elevation by examining the temperature activation profile of human Bax protein expressed in the cells of a cold-blooded vertebrate (frogs). The work will advance our understanding of how cell stress triggers apoptosis and how this is suppressed by Hsp70. These studies will therefore provide insight into the fundamental ability of cells and organisms to adapt and persist in stressful environments.