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

描述（申请人提供）：细胞凋亡是一个重要的细胞过程，对许多生理功能都很重要。细胞凋亡失调已被发现与多种疾病有关，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。鉴定介导细胞凋亡的新蛋白并阐明其潜在机制将对开发对抗这些疾病的新策略具有重要意义。阿尔茨海默病（AD）的一个重要病理特征和主要原因是？在大脑中形成细胞外老年斑的-淀粉样肽。一个吗?多肽来源于？-淀粉样前体蛋白（APP）通过？-secretase和？APP的切割由？-secretase还释放胞内结构域APP (AICD)，该结构域被认为在基因转录调控中起作用。此外，APP, ？APP -cleaved的c端片段（C99）、AICD和更小的片段（C31和Jcasp）通过caspase切割从AICD中获得，当过表达时被证明具有细胞毒性，表明它们参与细胞凋亡。在我们的初步研究中，我们已经确定了一种APP/ aicd相互作用蛋白appoptosin（也称为SLC25A38），它属于线粒体载体蛋白（MCP）家族。重要的是，我们发现appoptosin是一种促凋亡蛋白，它的过表达可以诱导caspase依赖性细胞凋亡，而APP是其中的一部分。此外，在损伤治疗后，阿尔茨海默病大脑和神经元中的凋亡蛋白水平升高，而凋亡蛋白的下调可以保护神经元免受神经毒性。因此，我们假设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。在本项目中，我们将进一步研究凋亡蛋白诱导细胞凋亡的分子途径，并确定凋亡蛋白的生物学功能。我们将确定APP及其代谢物是否以及如何影响凋亡蛋白并相互影响，研究凋亡蛋白是否调节APP加工/A？的一代。此外，我们将研究AD患者和转基因小鼠脑样本中凋亡蛋白的活性、浓度或定位的变化，以建立凋亡蛋白与AD之间的直接联系。此外，我们将产生凋亡蛋白（条件）敲除小鼠来研究其生理功能。通过将脑特异性凋亡蛋白敲除小鼠与AD小鼠模型杂交，我们将确定大脑中凋亡蛋白缺乏是否可以改善AD小鼠的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，并证明其在退行性损伤相关的神经元死亡中的重要性。研究结果表明，凋亡蛋白可作为治疗多种疾病的新靶点，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.