Role of HSP70 in the regulation of miRNA biogenesis in heat stressed cells

环境压力或疾病会导致蛋白质损伤，这对细胞有毒，并可能导致不适当的细胞死亡。细胞通过激活进化上保守的“热休克反应”来响应压力刺激，导致热休克蛋白的产生增加。这些蛋白质作为分子伴侣发挥作用，是防御机制的一部分，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蛋白毒性应激中存活。应激诱导的细胞死亡通过被称为细胞凋亡的细胞消除的调节过程发生，其由BCL 2家族的促凋亡和抗凋亡成员控制。细胞生物学中的一个基本问题是细胞如何调节启动凋亡细胞破坏过程的决定。我的研究计划的首要重点是研究热休克蛋白在这一决策过程中的作用。我们的工作导致了最初的证明，主要的热休克蛋白HSP 70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HSP 70如何防止这种情况发生。我们已经确定了促凋亡BCL 2家族蛋白NOXA在热诱导的细胞凋亡中的作用。我们证明了HSP 70可以防止热诱导的NOXA积累。我们还表明，这是通过调节调节NOXA蛋白合成的microRNA（miR-23 a）发生的。本实验将研究热应激细胞中控制miRNA生物合成的机制以及它们如何受到HSP 70的调控。我们计划鉴定调节pri-miR-23 a表达的转录因子，并研究它们的活性如何受高温和HSP 70之间的相互作用控制。最近的研究表明，microRNA可以由细胞释放并递送到外泌体内的受体细胞。我们计划研究高温和HSP 70过表达对外泌体miRNA输出的影响。这些研究的结果将提供深入了解高温对microRNA生物合成的影响以及HSP 70在保护这一重要过程中的作用。他们将为一个尚未探索的细胞生物学领域奠定基础，该领域可能对自然科学的一个基本研究领域产生重大影响，并可能导致将这些知识应用于疾病状态的研究。例如，微小RNA在调节细胞生物学的几乎所有方面中发挥重要作用，并且它们的失调导致许多人类疾病，包括癌症。HSP 70过表达和凋亡抑制是癌细胞的定义特征，而在衰老过程中产生HSP 70的能力下降。然而，蛋白毒性应激对microRNA生物合成的影响及其与疾病的关系以及HSP 70的作用知之甚少。

Environmental stress or disease can result in protein damage, which is toxic to cells and can lead to inappropriate cell death. 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 function as molecular chaperones and are part of a defense mechanism that acts to limit the extent of protein damage and thereby allow cells and organisms to survive proteotoxic stresses. Stress-induced cell death occurs through a regulated process of cell elimination known as apoptosis, which is controlled by pro- and anti-apoptotic members of the BCL2 family. A fundamental question in cell biology is how cells regulate the decision to initiate the process of apoptotic cell destruction. The overarching focus of my research program has been to examine the role of heat-shock proteins in this decision-making process.****Our work led to the original demonstration that the major heat-shock protein HSP70 prevents stress-induced apoptosis. The long-term goals of my research program are to determine how hyperthermia triggers apoptosis and how HSP70 prevents this from occurring. We have established a role for the pro-apoptotic BCL2 family protein NOXA in heat-induced apoptosis. We demonstrated that HSP70 prevents the heat-induced accumulation of NOXA. We also showed that this occurs through modulation of a microRNA (miR-23a) that regulates NOXA protein synthesis. Experiments in this proposal will examine the mechanisms controlling miRNA biogenesis in heat stressed cells and how they are regulated by HSP70. We plan to identify the transcription factors regulating pri-miR-23a expression and examine how their activity is controlled by the interplay between hyperthermia and HSP70. Recent studies have shown that microRNAs can be released by cells and delivered to recipient cells within exosomes. We plan to examine the effect of hyperthermia and HSP70 overexpression on exosomal miRNA export.****The results of these studies will provide insight into the effects of hyperthermia on microRNA biogenesis and the role of HSP70 in protecting this vital process. They will establish the foundation for an as-yet-unexplored area of cell biology that is likely to have a significant impact on a fundamental area of research in the natural sciences and could potentially lead to studies that would apply this knowledge to disease states. For example, microRNAs play essential roles in regulating nearly all aspects of cell biology and their deregulation contributes to a number of human diseases including cancer. HSP70 overexpression and apoptosis suppression are defining features of cancer cells whereas a decline in the ability to produce HSP70 occurs during aging. However the effects of proteotoxic stress on microRNA biogenesis and its relationship to disease are poorly understood as is the role of HSP70.**