Lysosome biogenesis and homeostasis

溶酶体生物发生和稳态

• 批准号: 8746700
• 负责人: rosa puertollano
• 金额: $ 48.33万
• 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/8746700
• 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; Glycogen; Glycogen storage disease type II; Goals; Growth; Growth Factor; Guanosine Triphosphate Phosphohydrolases; Helix-Turn-Helix Motifs; Homeostasis; Laboratories; Lead; Leucine Zippers; Link; Lysosomes; Malignant Neoplasms; Mediating; Metabolic Diseases; Molecular; Molecular Chaperones; Muscle Fibers; Nutrient; Organelles; Phosphorylation; Production; Protein Biosynthesis; Protein-Serine-Threonine Kinases; Proteins; Recruitment Activity; Regulation; Reporting; Research; Role; Signal Transduction; Starvation; Stress; Surface; Up-Regulation; Variant; Work; cell growth; deprivation; human FRAP1 protein; human disease; insight; late endosome; member; new therapeutic target; 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 also found that TFEB is recruited to lysosomes through direct interaction with active Rag GTPases. This Rag-mediated redistribution of TFEB to the lysosomal surface facilitates the phosphorylation of TFEB by mTORC1 and constitutes an efficient way to link nutrient availability to TFEB inactivation. Inhibition of the interaction between TFEB and Rags results in accumulation of TFEB in the nucleus and constitutive activation of autophagy under nutrient rich conditions, thus indicating that recruitment of TFEB to lysosomes is critical for the proper control of this transcription factor. 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. In collaboration with the group of Dr. Andrea Ballabio, we previously reported that over-expression of TFEB induces lysosomal exocytosis and leads to cellular clearance in several Lysosomal Storage Disorders. We have now extended these observations and found that TFEB is a promising novel therapeutic target for the treatment of Pompe disease. In collaboration with the laboratory of Nina Raben we observed that over-expression of TFEB is sufficient to dramatically reduce lysosomal size and intra-lysosomal glycogen accumulation in Pompe disease myotubes. 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和抑制信号，以最终调节多种关键细胞功能，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，其响应于能量水平、生长因子和营养物调节增殖、细胞周期和自噬。mTOR对许多压力做出反应，其失调导致癌症、代谢疾病和糖尿病。在细胞中，mTOR作为两种结构和功能不同的复合物存在，称为mTOR复合物1（mTORC 1）和mTOR复合物2（mTORC 2）。mTORC 1通过平衡合成代谢（蛋白质合成和营养储存）和分解代谢过程（自噬和能量储存的利用）将能量和营养丰度与细胞生长和增殖相结合。活性mTORC 1定位于晚期内体/溶酶体，这种分布被认为对于mTORC 1感知和响应氨基酸水平变化的能力至关重要。mTORC 1被认为是自噬的转录非依赖性调节因子。在营养丰富的条件下，mTORC 1是活跃的，并直接磷酸化和抑制参与自噬诱导的Atg蛋白，如Atg 13和Atg 1（ULK 1/2）。在饥饿条件下，当mTORC 1失活时，mTORC 1从ULK复合物中解离，从而导致自噬诱导。 最近，一个新的转录依赖性机制调节自噬已被确定。转录因子EB（TFEB）是碱性螺旋-环-螺旋亮氨酸拉链转录因子家族的成员，其通过正调节属于协调溶酶体表达和调节（CLEAR）网络的基因来控制溶酶体生物发生和自噬。重要的是，我们发现mTORC 1控制TFEB的活性和细胞定位。在营养丰富的条件下，mTORC 1磷酸化S211中的TFEB，从而促进TFEB与胞质伴侣14-3-3的结合和TFEB在胞质中的保留。在氨基酸剥夺后，TFEB/14-3-3复合物的解离导致TFEB递送至细胞核和基因的上调，这导致诱导自噬、溶酶体的生物发生和增加的溶酶体降解。 我们还发现TFEB通过与活性Rag GTP酶直接相互作用被募集到溶酶体。这种Rag介导的TFEB向溶酶体表面的再分布促进了mTORC 1对TFEB的磷酸化，并构成了将营养可用性与TFEB失活联系起来的有效方式。TFEB和Rags之间相互作用的抑制导致TFEB在细胞核中的积累和在营养丰富的条件下自噬的组成性激活，从而表明TFEB向溶酶体的募集对于该转录因子的适当控制是至关重要的。总的来说，我们的工作为理解溶酶体作为信号中心的新颖和令人兴奋的作用提供了新的见解，这些信号中心使环境线索与基因表达，能量产生和细胞内稳态同步。 与Andrea Ballabio博士的小组合作，我们以前报道过TFEB的过度表达诱导溶酶体胞吐，并导致几种溶酶体贮积症的细胞清除。我们现在已经扩展了这些观察结果，发现TFEB是治疗庞贝氏症的一个有前途的新的治疗靶点。在与Nina拉本实验室的合作中，我们观察到TFEB的过表达足以显著降低庞贝氏症肌管中的溶酶体大小和溶酶体内糖原积累。这项工作强调了新的基本细胞过程的阐明如何可能导致治疗人类疾病的新方法的发展。