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Phosphatidylinositol 3-kinases and Autophagy

磷脂酰肌醇 3-激酶和自噬

基本信息

批准号：
9205352
负责人：
Wei-Xing Zong
金额：
$ 36.49万
依托单位：
RUTGERS, THE STATE UNIV OF N.J.
依托单位国家：
美国
项目类别：
财政年份：
2012
资助国家：
美国
起止时间：
2012-04-13 至 2017-01-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9205352
关键词：
Phosphatidylinositol kinases Autophagy

项目摘要

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（PI 3 K）是使磷脂酰肌醇（PI）和磷酸肌醇的3 '-羟基磷酸化的脂质激酶。产生的磷脂是关键的信号分子。基于底物特异性和序列同源性，PI 3 K分为三类：I类、II类和III类。在体内，I类PI 3 K被认为优先磷酸化PtdIn（4，5）P2以产生PI（3，4，5）P3，PI（3，4，5）P3是激活多个下游信号级联的关键信号分子，包括Akt/TOR途径。III类PI 3 K由将PtdIns转化为PI（3）P的唯一成员Vps 34组成。Vps 34是据报道从酵母到哺乳动物进化保守的唯一PI 3 K。自噬是由PI 3 Ks控制的一个重要的细胞过程，它参与了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，III类PI 3 K Vps 34的产物。相反，自噬被PI（3，4，5）P3抑制，PI（3，4，5）P3是IA类PI 3 Ks的产物，其介导Akt/mTOR途径的活化。然而，PI 3 Ks，特别是IA类PI 3 Ks在自噬中的直接作用仍不清楚。使用p110 a和p110 <$conditional knockout小鼠，我们最近表明，IA类p110 <$isoform是一个积极的自噬调节，无论是在细胞培养和体内。第110页通过激活Vps 34激酶活性和自噬必需磷脂PI（3）P的产生促进自噬。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一个中心假设，即IA类p110亚基作为一种分子支架积极调节自噬。在这个提议中，我们计划研究p110 <$的自噬促进功能的分子机制，并探索其生物学作用。基于我们的初步数据，我们提出p110 <$可能通过激活小GTdR ab 5来促进自噬，最近已经证明小GTdR ab 5可以激活Vps 34并促进自噬。我们还假设，p110？改变其亚细胞定位和自噬促进活性，以响应营养因子剥夺。此外，尽管公认III类PI 3 K Vps 34在酵母中的自噬中起重要作用，但其在哺乳动物中的作用仍然难以捉摸。令人惊讶的是，最近的一份报告显示，自噬体仍然在Vps 34无效的感觉神经元中形成，这表明Vps 34在哺乳动物自噬中的分子和生理作用需要重新研究。我们最近的研究表明p110和Vps 34之间存在分子联系。因此，在这项提议中，我们还将使用组织特异性Vps 34敲除小鼠来研究Vps 34及其与p110的相互作用，以调节自噬。该项目的完成将揭示p110作为分子支架在基础状态和响应营养因子可用性促进自噬的新功能，并确定Vps 34在哺乳动物自噬中的作用。这将有助于我们理解PI 3 Ks在调节细胞稳态、代谢中的作用，以及它们在人类疾病如癌症中的参与。