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，这对细胞是有毒的，并可能导致不适当的细胞死亡。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。这些蛋白质作为分子伴侣发挥作用，是防御机制的一部分，该机制可以限制蛋白质损伤的程度，从而允许细胞和有机体在蛋白毒性压力下生存下来。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，该过程由BCL2家族中支持和反对凋亡的成员控制。细胞生物学中的一个基本问题是，细胞如何调控启动细胞凋亡破坏过程的决定。我的研究计划的主要重点一直是研究热休克蛋白在这一决策过程中的作用。 我们的工作导致了主要的热休克蛋白HSP70防止应激诱导的细胞凋亡的原始证明。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HSP70如何防止这种情况发生。我们已经确定了促凋亡的bcl2家族蛋白noxA在热诱导的细胞凋亡中的作用。我们证明了HSP70可以防止热诱导的NOXA积累。我们还表明，这是通过调节noxa蛋白合成的microRNA(miR-23a)来实现的。这项计划中的实验将研究控制热应激细胞中miRNA生物生成的机制，以及HSP70如何调节它们。我们计划鉴定调控pri-miR-23a表达的转录因子，并研究它们的活性是如何受到热疗和HSP70之间的相互作用的控制。最近的研究表明，microRNAs可以由细胞释放并递送到外体内的受体细胞。我们计划检测高温和HSP70过表达对外体miRNA输出的影响。 这些研究的结果将为深入了解高温对microRNA生物发生的影响以及HSP70在保护这一重要过程中的作用。它们将为尚未探索的细胞生物学领域奠定基础，该领域可能会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，microRNAs在调控细胞生物学的几乎所有方面都发挥着重要作用，它们的放松调控导致了包括癌症在内的许多人类疾病。HSP70的过度表达和凋亡抑制是癌细胞的特征，而产生HSP70的能力在衰老过程中会下降。然而，蛋白毒性应激对microRNA生物发生的影响及其与疾病的关系以及HSP70的作用尚不清楚。

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.