Hsp60 regulation of apoptosis in prostate cancer

描述（由申请人提供）：热休克蛋白60 （Hsp60）在前列腺癌（PCa）中高表达，与不良预后相关。细胞凋亡信号缺陷导致患者预后不良。缺陷性凋亡是由于Hsp60在PCa细胞中的高表达，然而，其潜在的分子机制尚未完全确定。我们的目标是确定Hsp60如何调节PCa细胞凋亡。我们和其他人观察到Hsp60在正常前列腺上皮细胞中定位于线粒体，而在前列腺癌细胞中，Hsp60同时存在于线粒体和细胞质中。我们提供的证据表明，线粒体Hsp60 （mHsp60）促进caspase-3激活，从而诱导细胞凋亡，而细胞质Hsp60 （cHsp60）不能支持caspase-3激活，从而抑制细胞凋亡。大多数mHsp60以低聚物形式存在，而cHsp60以单体形式存在。此外，hsp60寡聚物诱导caspase-3激活，但hsp60单体缺乏这一功能。因此，Hsp60在抗癌药物作用下促进或抑制细胞凋亡取决于其定位和分子形式。由于大多数caspase-3位于细胞质中，而hsp60寡聚物位于线粒体中，我们假设细胞质中hsp60寡聚物的积累诱导了有效的细胞凋亡。进一步，我们提出确定mHsp60如何激活线粒体中的caspase-3有可能改善现有的PCa治疗。为了解决这一假设并测试可能的治疗潜力，我们将：目标1。明确mHsp60激活caspase-3的机制，鉴定未知的mHsp60-/ chsp60相互作用蛋白。这些发现将描述寡聚物mHsp60如何与线粒体中的caspase-3相互作用并激活，以及线粒体中活性caspase-3如何放大caspase级联反应。目标2。探讨Hsp60寡聚状态及其对细胞凋亡的影响。目的是研究hsp60寡聚物在肿瘤细胞和正常细胞中caspase-3激活功能的相关性。目标3。评估hsp60寡聚物是否是前列腺癌肿瘤细胞凋亡的关键决定因素。本课题拟建研究的完成可能会确立hsp60寡聚物作为PCa治疗的关键靶点。重要影响：大部分caspase-3存在于细胞质中，因此新的抗pca药物可以触发/增强cHsp60的寡聚和/或从线粒体向细胞质释放mHsp60，从而诱导有效的caspase-3激活和细胞凋亡。由于单个cHsp60在癌症和肿瘤细胞的细胞质中高表达，而在正常细胞中不表达，因此在细胞质中诱导/增强Hsp60寡聚化的抗癌药物会选择性地诱导癌细胞凋亡。重要的是,

DESCRIPTION (provided by applicant): Heat shock protein 60 (Hsp60) is highly expressed in prostate cancer (PCa) and is associated with poor prognosis. Poor prognosis in patients results from defective apoptosis signaling. Defective apoptosis is due to high expression of Hsp60 in PCa cells, however, the underlying molecular mechanisms are not yet fully defined. Our goal is to determine how Hsp60 regulates PCa cell apoptosis. We and others observed that Hsp60 is localized to mitochondria in normal prostate epithelial cells, whereas in PCa cells Hsp60 is in both mitochondria and cytosol. We provided evidence that mitochondrial Hsp60 (mHsp60) promotes caspase-3 activation and thus induces apoptosis, whereas cytosolic Hsp60 (cHsp60) fails to support caspase-3 activation and suppresses apoptosis. The majority of mHsp60 exists as oligomers, whereas cHsp60 is in monomeric form. In addition, Hsp60-oligomer induces caspase-3 activation but Hsp60-monomer lacks this function. Therefore, whether Hsp60 promotes or suppresses apoptosis in response to anticancer agents is dependent upon both its localization and its molecular forms. Because majority of caspase-3 localizes in the cytosol and Hsp60-oligomer resides in mitochondria, we hypothesized that accumulation of Hsp60-oligomer in the cytosol induces efficient apoptosis. Further we propose that defining how mHsp60 activates caspase-3 in mitochondria has the potential to improve existing PCa therapy. To address the hypothesis and test possible therapeutic potentials, we will: Aim 1. Define the mechanisms of caspase-3 activation by mHsp60, and identify unknown mHsp60-/cHsp60-interacting proteins. The findings will delineate how oligomeric mHsp60 interacts with and activates caspase-3 in mitochondria, and how active caspase-3 in mitochondria amplifies the caspase cascade. Aim 2. Investigate the oligomerization status of Hsp60 and its impact on apoptosis. The goal of this Aim is to correlate the impact of caspase-3 activating function of Hsp60-oligomer in cancer and normal cells. Aim 3. Evaluate whether Hsp60-oligomer is a key determinant of apoptosis in PCa tumor. The completion of proposed research in this Aim may establish Hsp60-oligomer as a key target for PCa therapy. Important impact: The majority of caspase-3 resides in the cytosol, thus new anti-PCa agents that trigger/enhance oligomerization of cHsp60 and/or release of mHsp60 from mitochondria to the cytosol will induce efficient caspase-3 activation and apoptosis. Since monomeric cHsp60 is highly expressed in the cytosol of cancer and tumor cells but not in normal cells, anticancer agents that induce/enhance oligomerization of Hsp60 in the cytosol will selectively induce cancer cell apoptosis. Importantly, this proposal will identify Hsp60-oligomer as a new caspase-3-activating complex in apoptosis, and direct activation of caspase-3 by Hsp60 oligomer will be highly efficient means to induce PCa cell apoptosis because it does not rely on activation of initiator caspases (e.g., caspase-9, and -8).