Identifying and characterizing gene(s) involved in beta-amyloid production.

描述（由申请人提供）：阿尔茨海默病（AD）的特征是神经元外斑块由b-淀粉样蛋白（A?）肽和细胞内神经原纤维缠结（nft）组成，由微管相关蛋白tau的超磷酸化成对螺旋细丝组成。多种证据表明，A？在大脑中，过度磷酸化的tau蛋白是导致AD的主要原因，而在许多被称为tau病的神经退行性疾病中发现了过度磷酸化的tau蛋白。因此，识别参与这些过程的新基因/蛋白是阿尔茨海默病研究的主要目标，并可能提供潜在的治疗靶点。在之前的资助期内，我们应用随机纯合基因微扰（RHGP）技术筛选A？并鉴定出一种新的小鼠基因Rps23r1（在最初的提交中被命名为Fg01）。过表达RPS23R1蛋白可显著降低A？产生，tau磷酸化和GSK-3活性。进一步的体外研究表明，RPS23R1与腺苷酸环化酶相互作用，增加cAMP合成，从而上调PKA活性。已知PKA的激活和GSK-3的失活均可抑制A？生成和GSK-3失活也抑制tau磷酸化。Rps23r1的功能也在表达脑特异性Rps23r1的转基因小鼠中得到证实。此外，APP/PS1/tau三重转基因AD小鼠与Rps23r1转基因小鼠杂交后，AD样病理得到改善，突触标记蛋白水平升高。虽然Rps23r1是一个独特的小鼠基因，但Rps23r1在包括人类在内的各种物种的细胞中产生相同的表型。Rps23r1起源于小鼠Rps23（核糖体蛋白S23） mRNA逆转录，这是mRNA重新整合到基因组中导致基因复制/进化的过程。由于Rps23逆转录也发生在人类中，因此人类可能具有功能性的Rps23r1同源物。我们的研究结果表明，RPS23R1-和功能性人类RPS23R1同源介导的信号通路可能在AD和其他疾病（如癌症和糖尿病）的发病机制中发挥重要作用，其中PKA和GSK-3至关重要。因此，在这项竞争性更新提案中，我们的目标是确定RPS23R1的功能域，鉴定功能性的人类RPS23R1同源物，进一步表征RPS23R1及其人类同源物，并破译其作用机制，特别是抑制A生成，tau磷酸化和GSK-3活性的调节。我们将脑特异性Rps23r1转基因小鼠与AD转基因（Tg2576和APP/PS1/tau三重）小鼠杂交，以确定Rps23r1是否可以改善AD样病理和行为/认知缺陷。我们还将生成Rps23r1条件敲除小鼠，以探索Rps23r1的其他生理功能。这些研究结果有望为制定对抗阿尔茨海默病和其他疾病的新策略提供重要信息。

DESCRIPTION (provided by applicant): Alzheimer's disease (AD) is characterized by extraneuronal plaques consisting of b-amyloid (A?) peptides and intracellular neurofibrillary tangles (NFTs) composed of hyperphosphorylated, paired helical filaments of the microtubule-associated protein, tau. Multiple lines of evidence suggest that overproduction of A? in the brain is a major cause of AD, whereas hyperphosphorylated tau has been found in many neurodegenerative diseases known as tauopathies. Hence, identification of new genes/proteins involved in these processes is a major goal in AD research and may provide potential therapeutic targets. In the previous funding period, we applied the random homozygous gene perturbation (RHGP) technology to screen for genes involved in A? generation and identified a novel mouse gene, Rps23r1(previously named Fg01 in the original submission). Overexpression of the RPS23R1 protein can significantly reduce A? generation, tau phosphorylation and GSK-3 activity. Further in vitro studies showed that RPS23R1 interacts with adenylate cyclases, increasing cAMP synthesis, which upregulates PKA activity. Both activation of PKA and inactivation of GSK-3 are known to inhibit A? generation and GSK-3 inactivation also inhibits tau phosphorylation. The function of Rps23r1 was also demonstrated in transgenic mice expressing brain-specific Rps23r1. Furthermore, the AD-like pathologies of the APP/PS1/tau triple transgenic AD mice were ameliorated and levels of synaptic marker proteins were increased after crossing the mice with the Rps23r1 transgenic mice. Although Rps23r1 is a unique mouse gene, Rps23r1 produces the same phenotype in cells of various species including human. Rps23r1 originated through mouse Rps23 (ribosomal protein S23) mRNA retroposition, a process where mRNA is reintegrated into the genome resulting in gene duplication/evolution. Since Rps23 retroposition also occurred in humans, it is possible that humans possess functional Rps23r1 homologs. Our results suggest that RPS23R1- and functional human RPS23R1 homolog-mediated signaling pathways may play important roles in the pathogenesis of AD and other diseases, such as cancer and diabetes, in which PKA and GSK-3 are crucially involved. Therefore, in this competitive renewal proposal we aim to determine the functional domain(s) of RPS23R1, identify functional human Rps23r1 homologs, further characterize RPS23R1 and its human homologs and decipher mechanisms underlying their effects, specifically inhibition of A generation, tau phosphorylation and modulation of GSK-3 activity. We will cross brain-specific Rps23r1 transgenic mice with AD transgenic (Tg2576 and APP/PS1/tau triple) mice to determine whether Rps23r1 can ameliorate AD-like pathologies and behavioral/cognitive deficits. We will also generate Rps23r1 conditional knockout mice to explore other physiological functions of Rps23r1. The results of these studies are expected to provide important information for developing new strategies to combat AD and other diseases.