Cytochrome c Degradation: A Mechanism to Restrict Apoptosis in Postmitotic Cells

细胞色素 c 降解：限制有丝分裂后细胞凋亡的机制

• 批准号: 8534158
• 负责人: Mohanish P Deshmukh
• 金额: $ 34.55万
• 依托单位: UNIV OF NORTH CAROLINA CHAPEL HILL
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-09-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8534158
• 关键词: Affect; Apoptosis; Apoptotic; Binding; Binding Proteins; Cardiac; Cardiac Myocytes; Caspase; Cell Death; Cell Survival; Cells; Cessation of life; Cytosol; Degenerative Disorder; Employee Strikes; Ensure; Event; Failure; Fibroblasts; Goals; Heat-Shock Proteins 70; Laboratories; Life; Mammalian Cell; Mediating; Mitochondria; Mitotic; Molecular; Muscle Fibers; Muscular Dystrophies; Neurodegenerative Disorders; Neurons; Organism; Pathology; Pathway interactions; Physiological; Play; Proteins; Regulation; Reporting; Role; Safety; Testing; Ubiquitin; Ubiquitination; apoptotic protease-activating factor 1; cancer cell; clinically significant; cytochrome c; human BIRC4 protein; inhibitor-of-apoptosis protein; multicatalytic endopeptidase complex; novel; prevent; public health relevance; regenerative; ubiquitin-protein ligase

DESCRIPTION (provided by applicant): The ability to strictly regulate apoptosis is particularly important for postmitotic cells such as neurons, cardiomyocytes and myotubes because these cells have limited regenerative potential and are maintained for the lifetime of the organism. Failure to restrict apoptosis can result in increased vulnerability to cell death, as seen in many degenerative diseases. Therefore, an understanding of survival mechanisms in postmitotic cells is of physiological and pathological importance. The mitochondrial release of cytochrome c (cyt c) is a crucial event that triggers caspase activation during apoptosis. Here, we have identified a novel mechanism for regulating cyt c-mediated apoptosis engaged by neurons and other postmitotic cells, where cytosolic cyt c itself is targeted for proteasomal degradation. Importantly, while we do not observe cyt c degradation in primary mitotic cells such as fibroblasts, we find mitochondrial-released cyt c to be also degraded in certain cancer cells. As evasion of apoptosis is an important feature of both postmitotic and cancer cells, targeting cytosolic cyt c for degradation could be a shared mechanism used by these cells for survival. In this proposal, our goals are to identify the molecular mechanisms by which cytosolic cyt c is targeted for degradation. In Aim 1, we will define the factors which determine whether or not a cell will target cytosolic cyt c for degradation, including examining whether low levels of Apaf-1 in cells is a key determinant for cyt c degradation. In Aim 2, we will examine cyt c ubiquitination and identify the specific residues of cyt c that are targeted for ubiquitination. Our hypothesis is that ubiquitinated cyt c is not able to bind Apaf-1. We will test this, and examine whether conditions that block cyt c degradation increase the vulnerability of postmitotic cells to apoptosis. Our focus in Aim 3 is to identify the E3 ubiquitin ligase that targets cyt c for degradation. Our preliminary results suggest that cyt c binds to Hsp70 and the E3 Ligase CHIP (Carboxyl Heat shock protein 70-Interacting Protein) in the cytosol. Therefore, we will test whether the ubiquitination and degradation of cytosolic cyt c is mediated by CHIP in postmitotic and cancer cells. PUBLIC HEALTH RELEVANCE: Our plans here are to investigate how the cell death pathway is regulated in mammalian cells. We have discovered a novel mechanism engaged by postmitotic cells such as neurons, cardiomyocytes and myotubes that highly restricts cell death and likely ensures their long term survival. Understanding the survival mechanisms used by postmitotic cells has enormous clinical significance because increased death of these cells is central to the pathology of many neurodegenerative diseases, cardiac pathologies and muscular dystrophies.

描述（由申请人提供）：严格调节细胞凋亡的能力对于有丝分裂后细胞（例如神经元、心肌细胞和肌管）尤其重要，因为这些细胞的再生潜力有限并且在生物体的一生中都得以维持。正如许多退行性疾病中所见，未能限制细胞凋亡可能会导致细胞死亡的可能性增加。因此，了解有丝分裂后细胞的生存机制具有生理和病理意义。 细胞色素 c (cyt c) 的线粒体释放是细胞凋亡过程中触发 caspase 激活的关键事件。在这里，我们发现了一种调节神经元和其他有丝分裂后细胞参与的细胞色素 c 介导的细胞凋亡的新机制，其中细胞质细胞色素 c 本身是蛋白酶体降解的目标。 重要的是，虽然我们没有观察到原代有丝分裂细胞（如成纤维细胞）中的 cyt c 降解，但我们发现线粒体释放的 cyt c 在某些癌细胞中也会降解。由于逃避细胞凋亡是有丝分裂后细胞和癌细胞的一个重要特征，因此靶向胞浆细胞色素 c 进行降解可能是这些细胞用于生存的共同机制。 在本提案中，我们的目标是确定胞质 cyt c 降解的分子机制。在目标 1 中，我们将定义决定细胞是否靶向胞质 cyt c 进行降解的因素，包括检查细胞中低水平的 Apaf-1 是否是 cyt c 降解的关键决定因素。在目标 2 中，我们将检查 cyt c 泛素化并鉴定泛素化靶向的 cyt c 特定残基。我们的假设是泛素化的细胞色素 c 不能结合 Apaf-1。我们将对此进行测试，并检查阻止细胞色素 c 降解的条件是否会增加有丝分裂后细胞凋亡的脆弱性。我们目标 3 的重点是确定以细胞色素 c 为目标进行降解的 E3 泛素连接酶。我们的初步结果表明，细胞色素 c 与细胞质中的 Hsp70 和 E3 连接酶 CHIP（羧基热休克蛋白 70 相互作用蛋白）结合。 因此，我们将测试有丝分裂后细胞和癌细胞中胞质细胞色素c的泛素化和降解是否由CHIP介导。 公共健康相关性：我们的计划是研究哺乳动物细胞中细胞死亡途径的调节方式。我们发现了神经元、心肌细胞和肌管等有丝分裂后细胞参与的一种新机制，可以高度限制细胞死亡，并可能确保它们的长期存活。了解有丝分裂后细胞的生存机制具有巨大的临床意义，因为这些细胞死亡的增加是许多神经退行性疾病、心脏病和肌营养不良的病理学的核心。

项目成果

Human embryonic stem cells have constitutively active Bax at the Golgi and are primed to undergo rapid apoptosis.

• DOI: 10.1016/j.molcel.2012.04.002
• 发表时间: 2012-06-08
• 期刊: MOLECULAR CELL
• 影响因子: 16
• 作者: Dumitru, Raluca;Gama, Vivian;Fagan, B. Matthew;Bower, Jacquelyn J.;Swahari, Vijay;Pevny, Larysa H.;Deshmukh, Mohanish
• 通讯作者: Deshmukh, Mohanish

Cerebellar granule neuron progenitors are the source of Hk2 in the postnatal cerebellum.

小脑颗粒神经元祖细胞是出生后小脑中 Hk2 的来源。

• DOI: 10.1186/2049-3002-1-15
• 发表时间: 2013-06-11
• 期刊: Cancer & metabolism
• 影响因子: 5.9
• 作者: Gershon TR;Crowther AJ;Liu H;Miller CR;Deshmukh M
• 通讯作者: Deshmukh M

Bax deficiency prolongs cerebellar neurogenesis, accelerates medulloblastoma formation and paradoxically increases both malignancy and differentiation.

• DOI: 10.1038/onc.2012.248
• 发表时间: 2013-05-02
• 期刊: ONCOGENE
• 影响因子: 8
• 作者: Garcia, I.;Crowther, A. J.;Gama, V.;Miller, C. Ryan;Deshmukh, M.;Gershon, T. R.
• 通讯作者: Gershon, T. R.