Lysosome biogenesis and homeostasis

溶酶体生物发生和稳态

• 批准号: 9353144
• 负责人: Rosa Puertollano-Moro
• 金额: $ 104.66万
• 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/9353144
• 关键词: Address; Amino Acids; Autophagocytosis; Binding; Biogenesis; Calcineurin; Catabolic Process; Cell Cycle; Cell Death; Cell Fate Control; Cell Nucleus; Cell Proliferation; Cell physiology; Cells; Cellular Stress; Cellular biology; Complex; Couples; Cytosol; Diabetes Mellitus; Dissociation; Energy Metabolism; Equilibrium; FRAP1 gene; Family; Gene Expression; Genes; Goals; Growth; Growth Factor Gene; Guanosine Triphosphate Phosphohydrolases; Helix-Turn-Helix Motifs; Homeostasis; Immune; Immune response; Leucine Zippers; Link; Lysosomes; Malignant Neoplasms; Mediating; Metabolic Diseases; Molecular; Molecular Chaperones; Nutrient; Organelles; Pathway interactions; Phosphorylation; Play; Process; Protein Biosynthesis; Protein-Serine-Threonine Kinases; Proteins; Recruitment Activity; Regulation; Research; Role; Signal Transduction; Starvation; Stress; Surface; Transcriptional Regulation; Up-Regulation; Variant; Work; activating transcription factor; cell growth; chemokine; cytokine; deprivation; detection of nutrient; late endosome; macrophage; member; novel; overexpression; response; stressor; 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. 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. We have also identified the transcription factor E3 (TFE3) as novel regulator of lysosomal formation and function. Similar to TFEB, the recruitment of TFE3 to lysosomes is mediated by active Rag GTPases and this step is critical for mTORC1-mediated phosphorylation of TFE3 and retention in the cytosol. Over-expression of TFE3 results in increased autophagy and enhanced lysosomal biogenesis, as evidenced by an increase in the number of lysosomes and lysosomal activity. In contrast, depletion of endogenous TFE3 entirely abolishes the cellular response to starvation, thus confirming the crucial role of TFE3 in nutrient sensing and energy metabolism. More recently we have addresses the participation of TFEB and TFE3 in cellular adaptation to different types of stress. We found that TFEB and TFE3 play an important role in the cellular response to ER stress. Treatment with ER stressors causes translocation of TFEB and TFE3 to the nucleus in a process that is dependent on PERK and calcineurin but not on mTORC1. Activated TFEB and TFE3 enhance cellular response to stress by inducing direct transcriptional upregulation of ATF4 and other unfolded protein response (UPR) genes. Under conditions of prolonged ER stress, TFEB and TFE3 contribute to cell death, thus revealing an unexpected role for these proteins in controlling cell fate. Finally, we found that TFEB and TFE3 cooperate in the transcriptional regulation of the innate immune response. TFEB and TFE3 are rapidly recruited to the nucleus of activated macrophages where they promote lysosomal biogenesis, autophagy induction, as well as expression of a number of cytokines, chemokines, and other immune-related genes involved in the regulation and activation of the innate immune response. In summary, our work evidences a broader role of TFEB and TFE3 in the cellular response to stress than previously anticipated and reveals an integrated cooperation between different cellular stress pathways.

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，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，根据能量水平、生长因子和营养物质调节增殖、细胞周期和自噬。mTOR响应多种应激，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 （mTORC1）和mTOR复合物2 （mTORC2）。mTORC1通过平衡合成代谢（蛋白质合成和营养储存）和分解代谢过程（自噬和能量储存的利用），将能量和营养丰富度与细胞生长和增殖结合起来。活性mTORC1定位于晚期内体/溶酶体，这种分布被认为对mTORC1感知和响应氨基酸水平变化的能力至关重要。