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Autophagy and Immunity Jianzhong Chen Institute of Immunology Zhejiang University School of Medicine Nov 1, 2013 Autophagy Phagy = eating/lysosomal degradation Autophagy = self-eating Mechanism of breakdown of cytoplasm within the lysosome Autophagy: a basic cellular process in eukaryotes 细胞在外界环境因素的影响下，对其内部受损的细胞器、错 误折叠的蛋白质及侵入其内的病原体进行降解的过程。 发现 发现 比利时科学家Christian de Duve在上世纪50 年代通过电镜观察到自噬体结构，并且在 1963 年溶酶体国际会议上首先提出了“自噬 ”这种说法。因此Christian de Duve被公认 为自噬研究的鼻祖。Christian de Duve 也因 发现溶酶体，于1974年获得诺贝尔奖。 “细胞自噬研究”是2013年诺贝尔生理学或 医学奖预测的热门领域。 Autophagy: target Autophagic targets range in size and complexity Individual long-lived macromolecules Whole organelles Microbial invaders Autophagy: purposes (a) quality control of disused or defunct organelles such as irreversibly depolarized or leaky mitochondria; (b) removal of toxic macromolecular aggregates too large for handling by smaller capacity or single-molecule-handling proteolytic systems of the cell (e.g. proteasome); Autophagy: purposes (c) digestion of bulk cytoplasm expressly to replenish amino acids and energy during starvation or growth factor withdrawal; (d) acting on or in concert with the molecular machineries and organelles at the interface between cell survival and cell death (e) controlling and acting as an effector or a regulator of innate and adaptive immunity and inflammation, Autophagy: Function The principal role of Autophagy this ubiquitous eukaryotic homeostatic mechanism is to ensure cell survival under adverse conditions nutrient absence, growth factor withdrawal accumulation of toxic protein aggregates Faulty organelles (e.g., leaky mitochondria) infection by intracellular Autophagy Regulation Highly conserved and regulated process that maintains cellular homeostasis and protects cells against starvation and microbe invasion Autophagy: Function The physiologic and pathophysiologic roles of autophagy (and defects in autophagy) are vast, encompassing Cancer Neurodegeneration metabolic diseases Aging Immunity. Autophagy Autophagosome: A double membrane bound compartment that engulfs cytosol and degrades the cytoplasmic contents. Large: 400-1500 nm May originate from ER or from fusion of lipid-containing vesicles that form ‘sequestration crescent’. Autophagy：type Autophagy：type 根据自噬对底物的选择性可以将自噬可以分为 二类：选择性自噬和非选择性自噬。 非选择性自噬是指细胞内的细胞器随机运送到 溶酶体降解。 选择性自噬是指对降解的底物蛋白有专一性， 根据对底物蛋白选择性的不同，可以分为线粒 体自噬，过氧化物体自噬、内质网自噬、核糖 体自噬和细胞核的碎片状自噬等。 细胞自噬途径 Autophagy genes Based on S. cerevisiae yeast studies. ATG in yeast, homologs in other species. Three Stages Initiation: nutrient starvation, growth factor-mediated starvation Elongation Maturation Autophagy signaling Induction 外部因素 营养缺乏 激素 内部因素 细胞器损伤 异常成分积聚或必需成分存在 病原体 酵母和哺乳动物中自噬诱导的调节 酵母和哺乳动物中自噬诱导的调节 Induction Current Opinion in Immunology 2012, 24:21–31 Elongation Covalent linkage of Atg5 and Atg12 Covalent lipidation of Atg8 Enzymes Atg3, Atg7, and Atg10 are homologs of ubiquitylation enzymes but are used to modify pathway components instead of labeling them for degradation. Maturation GTPases (Rab24) mediate vesicle fusion. Intermediate autophagosomes Fuse with endosomal vesicles. Acquire LAMP, accumulate DAMP proteins. Mature autolysosomes Fuse with lysosomes. Acquire cathepsins and acid phosphatases. The regulation of autophagy Autophagy Regulation Autophagy is regulated by nutrients, growth factors and stress. Various forms of autophagy induction Tuberculosis 92 (2012) 388e396 Regulation of autophagy by cytokines Cellular Signalling 25 (2013) 1272–1278 Detection methods Microscopy Biochemistry Electron microscopy – ultrastructure, morphology, volumetrics, staining. Enzyme activity assays. Radioactive degradation studies. Marker studies Autophagosomal or organelle markers. Fluorescence or immunodetection. Autophagy and diseases Oncology Liver Breast Colon Lung Beclin-1 Myodegerative disease Cardiac stress a-antitrypsin deficiency …… Brain Alzheimer Multiple Sclerosis Parkinson’s disease Hungtingdon’s disease Miscellaneous Cellular Process Apoptosis Aging Growth …… Autophagy and immunity Antigen presentation TLR signaling Infection Inflammation …… Role of autophagy Does autophagy benefit the host as a defense mechanism? Does autophagy benefit the microbe by facilitating survival and replication? Or both? Pharmacological Research 66 (2012) 475– 483 PRRs inflammasomes and autophagy Current Opinion in Immunology 2012, 24:21–31 Exp. Mol. Med. 44(2), 99-108, 2012 Manipulation of autophagy by intracellular bacteria Science,2013,340:697 Human macrophage host defense mechanisms against intracellular M. tuberculosis. Current Opinion in Immunology 2008, 20:371–376 M. tuberculosis inhibits phagosome-lysosome fusion Tuberculosis 92 (2012) 388e396 The role of autophagy in the mode of action of cytokines and antituberculosis drugs in M. tuberculosis infection. Cytokine & Growth Factor Reviews 24 (2013) 335–343 Autophagy as a mechanism to prevent exaggerated endotoxin-induced IL-1β production in macrophages. TIP OF THE ICEBERG?