Lysosome biogenesis and homeostasis

溶酶体生物发生和稳态

• 批准号: 8558084
• 负责人: rosa puertollano
• 金额: $ 51.15万
• 依托单位: NATIONAL HEART, LUNG, AND BLOOD INSTITUTE
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8558084
• 关键词: Amino Acids; Autophagocytosis; Binding; Biogenesis; Catabolic Process; Cell Cycle; Cell Nucleus; Cell Proliferation; Cell physiology; Cells; Cellular biology; Collaborations; Complex; Couples; Cues; Cytosol; Development; Diabetes Mellitus; Disease; Dissociation; Equilibrium; Exocytosis; Family; Gene Expression; Genes; Genetic Transcription; Goals; Growth; Growth Factor; Helix-Turn-Helix Motifs; Homeostasis; Lead; Leucine Zippers; Lysosomes; Malignant Neoplasms; Metabolic Diseases; Molecular; Molecular Chaperones; Nutrient; Organelles; Production; Protein Biosynthesis; Protein-Serine-Threonine Kinases; Proteins; Regulation; Research; Role; Signal Transduction; Starvation; Stress; Up-Regulation; Variant; Work; cell growth; deprivation; human FRAP1 protein; human disease; insight; late endosome; member; novel; novel strategies; response; transcription factor

One of the most fundamental issues in cell biology is how cells integrate growth-stimulating and inhibitory signals to ultimately regulate a diversity of key cellular functions, including gene expression, autophagy, organelle biogenesis, and cell growth. mTOR is a serine/threonine kinase that regulates proliferation, cell cycle, and autophagy in response to energy levels, growth factors, and nutrients. mTOR responds to numerous stresses and its dysregulation leads to cancer, metabolic disease, and diabetes. In cells, mTOR exists as two structurally and functionally distinct complexes termed mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2). mTORC1 couples energy and nutrient abundance to cell growth and proliferation by balancing anabolic (protein synthesis and nutrient storage) and catabolic processes (autophagy and the utilization of energy stores). Active mTORC1 localizes to late endosomes/lysosomes and this distribution is thought to be critical for the ability of mTORC1 to sense and respond to variations in the levels of amino acids. mTORC1 is considered a transcription-independent regulator of autophagy. Under rich-nutrient conditions, mTORC1 is active and directly phosphorylates and inhibits Atg proteins involved in autophagy induction such as Atg13 and Atg1 (ULK1/2). Under starvation conditions when mTORC1 is inactivated, mTORC1 dissociates from the ULK complex, thus leading to autophagy induction. Recently, a new transcription-dependent mechanism regulating autophagy has been identified. The transcription factor EB (TFEB) is a member of the basic helix-loop-helix leucine-zipper family of transcription factors that controls lysosomal biogenesis and autophagy by positively regulating genes belonging to the Coordinated Lysosomal Expression and Regulation (CLEAR) network. Importantly, we have found that mTORC1 controls the activity and cellular localization of TFEB. Under nutrient-rich conditions, mTORC1 phophorylates TFEB in S211, thus promoting binding of TFEB to the cytosolic chaperone 14-3-3 and retention of TFEB in the cytosol. Upon amino acids deprivation, dissociation of the TFEB/14-3-3 complex results in delivery of TFEB to the nucleus and up-regulation of genes that leads to induction of autophagy, biogenesis of lysosomes, and increased lysosomal degradation. We are currently investigating the molecular mechanisms that regulate recruitment of TFEB to lysosomes, a critical step in the regulation of this transcription factor by mTORC1. Overall, our work provides new insight for understanding the novel and exciting role of lysosomes as signaling centers that synchronize environmental cues with gene expression, energy production, and cellular homeostasis. Finally, and in collaboration with the group of Dr. Andrea Ballabio, we found that over-expression of TFEB induces lysosomal exocytosis and leads to cellular clearance in several Lysosomal Storage Disorders. This work emphasizes how the elucidation of novel basic cellular processes may potentially lead to the development of new approaches for treatment of human disease.

细胞生物学中最基本的问题之一是细胞如何整合生长刺激信号和抑制信号，最终调控多种关键细胞功能，包括基因表达、自噬、细胞器生物发生和细胞生长。MTOR是一种丝氨酸/苏氨酸激酶，调节细胞增殖、细胞周期和自噬，以响应能量水平、生长因子和营养物质。MTOR对大量压力做出反应，其失调会导致癌症、代谢性疾病和糖尿病。在细胞中，mTOR以两种结构和功能不同的复合体存在，称为mTOR复合体1(MTORC1)和mTOR复合体2(MTORC2)。MTORC1通过平衡合成代谢(蛋白质合成和营养储存)和分解代谢(自噬和能量储存)，将丰富的能量和营养与细胞的生长和增殖联系在一起。活性的mTORC1定位于晚期的内切体/溶酶体，这种分布被认为是mTORC1感知和响应氨基酸水平变化的能力的关键。MTORC1被认为是自噬的非转录调节因子。在营养丰富的条件下，mTORC1是活性的，直接磷酸化并抑制参与自噬诱导的ATG蛋白，如ATg13和Atg1(ULK1/2)。在饥饿条件下，当mTORC1失活时，mTORC1从ULK复合体中解离，从而导致自噬诱导。 最近，人们发现了一种新的调控自噬的转录依赖机制。转录因子EB(TFEB)是基本的螺旋-环-螺旋-亮氨酸拉链转录因子家族的成员，通过正向调节溶酶体表达与调节(CLEAR)网络中的基因来控制溶酶体的生物发生和自噬。重要的是，我们发现mTORC1控制着TFEB的活性和细胞定位。在营养丰富的条件下，mTORC1磷酸化S211中的TFEB，从而促进TFEB与胞液伴侣14-3-3的结合和TFEB在胞浆中的保留。当氨基酸缺乏时，TFEB/14-3-3复合体的解离导致TFEB被运送到细胞核，基因上调导致自噬、溶酶体的生物发生和溶酶体降解的增加。我们目前正在研究调节TFEB向溶酶体募集的分子机制，这是mTORC1调控该转录因子的关键步骤。总体而言，我们的工作为理解溶酶体作为信号中心的新的和令人兴奋的角色提供了新的见解，它将环境信号与基因表达、能量产生和细胞动态平衡同步。 最后，与Andrea Ballabio博士合作，我们发现TFEB的过度表达诱导溶酶体胞吐，并导致几种溶酶体储存障碍的细胞清除。这项工作强调了对新的基本细胞过程的阐明可能如何潜在地导致治疗人类疾病的新方法的发展。