Roles of an APP-binding pro-apoptotic protein in mediating neuronal cell death

描述（由申请人提供）：细胞凋亡是对许多生理功能重要的基本细胞过程。已经发现细胞凋亡的失调涉及多种疾病，包括癌症和神经退行性疾病。在神经退行性疾病中，神经元在遭受各种损伤后发生凋亡。鉴定新的蛋白质介导的细胞凋亡和阐明的潜在机制将是重要的发展新的战略，以打击这些疾病。阿尔茨海默病（AD）的一个重要病理特征和主要原因是？-淀粉样蛋白（A？）在大脑中形成细胞外老年斑的肽。一个？肽来自于？淀粉样前体蛋白（APP）通过连续切割？分泌酶和？-分泌酶APP的裂解方式为？-分泌酶还释放APP的胞内结构域（AICD），其已被认为在基因转录调节中起作用。此外，APP，？APP的裂解的C末端片段（C99）、AICD和通过半胱天冬酶裂解衍生自AICD的较小片段（C31和Jcasp）已显示在过表达时具有细胞毒性，表明它们参与细胞凋亡。在我们的初步研究中，我们已经确定了一个APP/AICD相互作用蛋白，凋亡素（也称为SLC 25 A38），它属于线粒体载体蛋白（MCP）家族。重要的是，我们发现，凋亡素是一种促凋亡蛋白，其过表达可以诱导caspase依赖的凋亡，其中APP是部分需要的。此外，凋亡素的水平在AD脑和神经元中在损伤处理后升高，而凋亡素的下调可以保护神经元免受神经毒性。因此，我们推测凋亡素介导的细胞凋亡在神经毒性诱导的神经退行性疾病如AD中起重要作用。在本研究中，我们将进一步研究凋亡素诱导细胞凋亡的分子途径，并确定凋亡素的生物学功能。我们将确定APP及其代谢产物是否以及如何影响appoptosin和apoptosin，研究appoptosin是否调节APP加工/A？一代此外，我们将研究AD患者和转基因小鼠脑样品中凋亡素的活性、浓度或定位的任何变化，以建立凋亡素与AD之间的直接联系。此外，我们还将构建凋亡素（条件性）基因敲除小鼠，研究其生理功能。通过将脑特异性凋亡素敲除小鼠与AD小鼠模型杂交，我们将确定脑中凋亡素的缺乏是否可以改善AD小鼠中的AD样病理和记忆/行为缺陷。总之，我们的研究将阐明凋亡素介导的细胞凋亡的机制，并证明其在与退行性损伤相关的神经元死亡中的重要性。这些结果将揭示凋亡素作为多种疾病的新治疗靶点，如神经退行性疾病和癌症。

DESCRIPTION (provided by applicant): Apoptosis is an essential cellular process important for many physiological functions. Dysregulation of apoptosis has been found to be involved in multiple diseases including cancers and neurodegenerative diseases. Neurons, after suffering various insults, undergo apoptosis in neurodegenerative diseases. Identification of new proteins mediating apoptosis and elucidation of the underlying mechanisms will be important for developing new strategies to fight against these diseases. An important pathologic feature and the primary cause of Alzheimer's disease (AD) is overproduction/accumulation of ?-amyloid (A?) peptides that form extracellular senile plaques in the brain. A? peptides are derived from ?-amyloid precursor protein (APP) through sequential cleavages by ?-secretase and ?-secretase. Cleavage of APP by ?-secretase also releases the intracellular domain of APP (AICD) which has been suggested to play a role in gene transcription regulation. Moreover, APP, ?-cleaved C-terminal fragment of APP (C99), AICD and smaller fragments (C31 and Jcasp), derived from AICD by caspase cleavage, have been shown to be cytotoxic when overexpressed, suggesting their involvement in apoptosis. In our preliminary studies, we have identified an APP/AICD-interacting protein, appoptosin (also known as SLC25A38), which belongs to the mitochondrial carrier protein (MCP) family. Importantly, we find that appoptosin is a pro-apoptotic protein and its overexpression can induce caspase-dependent apoptosis, for which APP is partially required. In addition, the level of appoptosin is elevated in AD brains and in neurons upon insult treatments, whereas downregulation of appoptosin can protect neurons against neurotoxicity. Therefore, we hypothesize that appoptosin-mediated apoptosis plays an important role in neurotoxicity-induced neurodegenerative diseases such as AD. In this application, we will further study the molecular pathways underlying the apoptosis induced by appoptosin and identify the biological function of appoptosin. We will ascertain whether and how APP and its metabolites affect appoptosin and reciprocally, study whether appoptosin regulates APP processing/A? generation. Furthermore, we will investigate any change in the activity, concentration or localization of appoptosin in the brain samples of AD patients and transgenic mice to establish a direct link between appoptosin and AD. Moreover, we will generate appoptosin (conditional) knockout mice to study its physiological functions. By crossing brain-specific appoptosin knockout mice with an AD mouse model, we will determine whether a deficiency of appoptosin in the brain can ameliorate AD-like pathologies and memory/behavioral deficits in the AD mice. Together, our studies will elucidate the mechanism underlying appoptosin-mediated apoptosis and demonstrate its importance in neuronal death associated with degenerative insults. The results should reveal appoptosin as a new therapeutic target for multiple diseases, such as neurodegenerative diseases and cancers.