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

细胞通过激活进化上保守的“热休克反应”来应对应激刺激，从而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，其作用是限制蛋白质损伤的程度，从而使细胞和生物体能够在通常是致命的温度压力下存活下来。热休克蛋白的功能是分子伴侣，因为它们协助蛋白质折叠，而蛋白质折叠会被高温暴露和其他蛋白质损伤应激破坏。应激诱导的细胞死亡是通过一个被称为凋亡的细胞消除调控过程发生的。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热疗是如何触发细胞凋亡的，以及主要的热诱导蛋白Hsp70是如何阻止这种情况发生的。我的假设是，热应激会影响特定Bcl-2家族蛋白的活性，而Bcl-2家族蛋白是调节细胞凋亡的核心。本研究的目的是确定热疗对促凋亡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细胞凋亡激活的热敏靶的性质。具体来说，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Bcl-2家族蛋白Mcl-1的相互作用；（ii）通过检测microrna在调控Noxa mRNA转录水平中的作用，确定热诱导Noxa mRNA积累的控制机制；（iii）通过检测冷血脊椎动物（青蛙）细胞中表达的人Bax蛋白的温度激活谱，确定促凋亡的Bcl-2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如何抑制细胞凋亡的理解。因此，这些研究将深入了解细胞和生物体在压力环境中适应和坚持的基本能力。

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.