Phosphatidylinositol 3-kinases and Autophagy

磷脂酰肌醇 3-激酶和自噬

• 批准号: 8454422
• 负责人: Wei-Xing Zong
• 金额: $ 38.72万
• 依托单位: STATE UNIVERSITY NEW YORK STONY BROOK
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-04-13 至 2016-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8454422
• 关键词: 1-Phosphatidylinositol 3-Kinase; Afferent Neurons; Autophagocytosis; Autophagosome; Biological; Biological Process; Bypass; Catalytic Domain; Cell Culture Techniques; Cell physiology; Cells; Complex; Data; Degenerative Disorder; Development; Etiology; GTPase-Activating Proteins; Generations; Genes; Heart; Homeostasis; Knock-out; Knockout Mice; Lipids; Liver; Lysosomes; Malignant Neoplasms; Mammals; Mediating; Membrane; Membrane Protein Traffic; Metabolic; Metabolism; Molecular; Monomeric GTP-Binding Proteins; Nutrient; Pathway interactions; Phosphatidylinositols; Phospholipids; Phosphotransferases; Physiological; Play; Process; Production; Protein Isoforms; Proteins; Proto-Oncogene Proteins c-akt; Regulation; Reporting; Role; Sensory; Sequence Homology; Signal Pathway; Signal Transduction; Signaling Molecule; Substrate Specificity; Testing; Tissues; Vps34 Phosphatidylinositol 3 Kinase; Yeasts; base; deprivation; design; essential phospholipids; human FRAP1 protein; human disease; hydroxyl group; in vivo; mTOR Signaling Pathway; member; novel; phosphatidylinositol phosphate, PtdIns(4,5)P2; response; scaffold; sensor; uptake

DESCRIPTION (provided by applicant): The phosphatidylinositol 3-kinases (PI3Ks) are lipid kinases that phosphorylate the 3'-hydroxyl group of phosphatidylinositol (PIs) and phosphoinositides. The generated phospholipids are critical signaling molecules. Based on substrate specificity and sequence homology, PI3Ks are grouped into three classes: Class I, Class II, and Class III. In vivo, Class I PI3Ks are believed to preferentially phosphorylate PtdIns(4,5)P2 to generate PI(3,4,5)P3, a pivotal signaling molecule that activates multiple downstream signaling cascades, including the Akt/TOR pathway. Class III PI3K is composed of a sole member, Vps34, that converts PtdIns to PI(3)P. Vps34 is the only PI3K reported to be evolutionarily conserved from yeast to mammals. An important cellular process controlled by PI3Ks is autophagy, which is involved in many physiological and pathological conditions. The current dogma is that in metazoans, autophagy requires PI(3)P, the product of Class III PI3K Vps34. On the contrary, autophagy is inhibited by PI(3,4,5)P3, the product of Class IA PI3Ks, that mediates activation of the Akt/mTOR pathway. However, the direct role of PI3Ks, especially that of the Class IA PI3Ks, in autophagy remains unclear. Using p110a and p110¿ conditional knockout mice, we have recently shown that the Class IA p110¿ isoform is a positive regulator of autophagy, both in cell culture and in vivo. p110¿ promotes autophagy by activating Vps34 kinase activity and the generation of the autophagy- essential phospholipid PI(3)P. This autophagy-promoting function of p110¿ is independent of its catalytic activity. These findings prompt us to propose the central hypothesis that the Class IA p110¿ subunit positively regulates autophagy acting as a molecular scaffold. In this proposal, we plan to study the molecular mechanisms underlying the autophagy-promoting function of p110¿, and to explore its biological roles. Based on our preliminary data, we propose that p110¿ may promote autophagy by activating the small GTPase Rab5, which has been recently shown to activate Vps34 and promote autophagy. We also hypothesize that p110¿ changes its subcellular localization and autophagy-promoting activity in response to trophic factor deprivation. Moreover, although it is well recognized that the Class III PI3K Vps34 plays an essential role in autophagy in yeast, its role in mammals remains elusive. Surprisingly, a recent report showed that autophagosomes still form in Vps34-null sensory neurons, suggesting that the molecular and physiological role of Vps34 in mammalian autophagy needs to be re-examined. Our recent study indicates a molecular connection between p110¿ and Vps34. Hence in this proposal, we will also use tissue-specific Vps34 knockout mice to study Vps34 and its interplay with p110¿ in regulating autophagy. Completion of this project will uncover the novel function of p110¿ as a molecular scaffold to promote autophagy both at basal state and in response to trophic factor availability, and define the role of Vps34 in autophagy in mammals. This will help our understanding to the roles of PI3Ks in regulating cellular homeostasis, metabolism, and their involvement in human diseases such as cancer.

描述（由申请人提供）：磷脂酰肌醇3-激酶（PI3K）是磷酸化磷脂酰肌醇（PI）和磷酸肌醇的3'-羟基的脂质激酶。产生的磷脂是关键的信号分子。根据底物特异性和序列同源性，PI3K 分为三类：I 类、II 类和 III 类。在体内，I 类 PI3K 被认为优先磷酸化 PtdIns(4,5)P2 以生成 PI(3,4,5)P3，PI(3,4,5)P3 是一种关键信号分子，可激活多个下游信号级联，包括 Akt/TOR 通路。 III 类 PI3K 由唯一成员 Vps34 组成，它将 PtdIns 转换为 PI(3)P。 Vps34 是唯一据报道从酵母到哺乳动物在进化上保守的 PI3K。 PI3Ks控制的一个重要的细胞过程是自噬，它参与许多生理和病理条件。目前的教条是，在后生动物中，自噬需要 PI(3)P，即 III 类 PI3K Vps34 的产物。相反，自噬被 PI(3,4,5)P3（IA 类 PI3K 的产物）抑制，介导 Akt/mTOR 通路的激活。然而，PI3K，尤其是 IA 类 PI3K，在自噬中的直接作用仍不清楚。使用 p110a 和 p110¿ 条件敲除小鼠，我们最近证明 IA 类 p110¿ 亚型在细胞培养和体内都是自噬的正调节因子。 p110¿ 通过激活 Vps34 激酶活性和自噬必需磷脂 PI(3)P 的生成来促进自噬。 p110 的这种自噬促进功能与其催化活性无关。这些发现促使我们提出中心假设，即 IA 类 p110 亚基作为分子支架积极调节自噬。在本提案中，我们计划研究p110¿促进自噬功能的分子机制，并探讨其生物学作用。根据我们的初步数据，我们提出 p110¿ 可能通过激活小 GTPase Rab5 来促进自噬，最近研究表明 Rab5 可以激活 Vps34 并促进自噬。我们还假设 p110¿ 响应营养因子剥夺而改变其亚细胞定位和自噬促进活性。此外，尽管人们普遍认识到 III 类 PI3K Vps34 在酵母自噬中发挥重要作用，但其在哺乳动物中的作用仍然难以捉摸。令人惊讶的是，最近的一份报告表明，自噬体仍然在 Vps34 缺失的感觉神经元中形成，这表明 Vps34 在哺乳动物自噬中的分子和生理作用需要重新检查。我们最近的研究表明 p110¿ 和 Vps34 之间存在分子联系。因此，在本提案中，我们还将使用组织特异性 Vps34 敲除小鼠来研究 Vps34 及其与 p110 在调节自噬中的相互作用。该项目的完成将揭示 p110 作为分子支架促进基础状态下自噬和响应营养因子可用性的新功能，并确定 Vps34 在哺乳动物自噬中的作用。这将有助于我们了解 PI3K 在调节细胞稳态、新陈代谢中的作用及其与癌症等人类疾病的关系。