Induction of autophagy and inhibition of tumorigenesis by beclin 1

The process of autophagy, or bulk degradation of cellular proteins through an autophagosomic-lysosomal pathway, is important in normal growth control and may be defective in tumour cells. However, little is known about the genetic mediators of autophagy in mammalian cells or their role in tumour development. The mammalian gene encoding Beclin 1, a novel Bcl-2-interacting, coiled-coil protein, has structural similarity to the yeast autophagy gene, apg6/vps30, and is mono-allelically deleted in 40-75% of sporadic human breast cancers and ovarian cancers. Here we show, using gene-transfer techniques, that beclin 1 promotes autophagy in autophagy-defective yeast with a targeted disruption of agp6/vps30, and in human MCF7 breast carcinoma cells. The autophagy-promoting activity of beclin 1 in MCF7 cells is associated with inhibition of MCF7 cellular proliferation, in vitro clonigenicity and tumorigenesis in nude mice. Furthermore, endogenous Beclin 1 protein expression is frequently low in human breast epithelial carcinoma cell lines and tissue, but is expressed ubiquitously at high levels in normal breast epithelia. Thus, beclin 1 is a mammalian autophagy gene that can inhibit tumorigenesis and is expressed at decreased levels in human breast carcinoma. These findings suggest that decreased expression of autophagy proteins may contribute to the development or progression of breast and other human malignancies.     

HDAC6 rescues neurodegeneration and provides an essential link between autophagy and the UPS

A prominent feature of late-onset neurodegenerative diseases is accumulation of misfolded protein in vulnerable neurons. When levels of misfolded protein overwhelm degradative pathways, the result is cellular toxicity and neurodegeneration. Cellular mechanisms for degrading misfolded protein include the ubiquitin-proteasome system (UPS), the main non-lysosomal degradative pathway for ubiquitinated proteins, and autophagy, a lysosome-mediated degradative pathway. The UPS and autophagy have long been viewed as complementary degradation systems with no point of intersection. This view has been challenged by two observations suggesting an apparent interaction: impairment of the UPS induces autophagy in vitro, and conditional knockout of autophagy in the mouse brain leads to neurodegeneration with ubiquitin-positive pathology. It is not known whether autophagy is strictly a parallel degradation system, or whether it is a compensatory degradation system when the UPS is impaired; furthermore, if there is a compensatory interaction between these systems, the molecular link is not known. Here we show that autophagy acts as a compensatory degradation system when the UPS is impaired in Drosophila melanogaster, and that histone deacetylase 6 (HDAC6), a microtubule-associated deacetylase that interacts with polyubiquitinated proteins, is an essential mechanistic link in this compensatory interaction. We found that compensatory autophagy was induced in response to mutations affecting the proteasome and in response to UPS impairment in a fly model of the neurodegenerative disease spinobulbar muscular atrophy. Autophagy compensated for impaired UPS function in an HDAC6-dependent manner. Furthermore, expression of HDAC6 was sufficient to rescue degeneration associated with UPS dysfunction in vivo in an autophagy-dependent manner. This study suggests that impairment of autophagy (for example, associated with ageing or genetic variation) might predispose to neurodegeneration. Morover, these findings suggest that it may be possible to intervene in neurodegeneration by augmenting HDAC6 to enhance autophagy.     

Non-apoptotic role of BID in inflammation and innate immunity

Innate immunity is a fundamental defence response that depends on evolutionarily conserved pattern recognition receptors for sensing infections or danger signals. Nucleotide-binding and oligomerization domain (NOD) proteins are cytosolic pattern-recognition receptors of paramount importance in the intestine, and their dysregulation is associated with inflammatory bowel disease. They sense peptidoglycans from commensal microorganisms and pathogens and coordinate signalling events that culminate in the induction of inflammation and anti-microbial responses. However, the signalling mechanisms involved in this process are not fully understood. Here, using genome-wide RNA interference, we identify candidate genes that modulate the NOD1 inflammatory response in intestinal epithelial cells. Our results reveal a significant crosstalk between innate immunity and apoptosis and identify BID, a BCL2 family protein, as a critical component of the inflammatory response. Colonocytes depleted of BID or macrophages from Bid(-/-) mice are markedly defective in cytokine production in response to NOD activation. Furthermore, Bid(-/-) mice are unresponsive to local or systemic exposure to NOD agonists or their protective effect in experimental colitis. Mechanistically, BID interacts with NOD1, NOD2 and the IκB kinase (IKK) complex, impacting NF-κB and extracellular signal-regulated kinase (ERK) signalling. Our results define a novel role of BID in inflammation and immunity independent of its apoptotic function, furthering the mounting evidence of evolutionary conservation between the mechanisms of apoptosis and immunity.     

细胞自噬对拟南芥种子萌发的影响

自噬在植物生长发育过程发挥着至关重要的作用，但是植物中自噬与种子萌发的关系尚不明确。为了探究自噬对种子萌发的影响，通过基因表达检测、蛋白免疫印迹实验和种子萌发速率比较，分析了细胞自噬对拟南芥(Arabidopsis thaliana)种子萌发的影响。研究结果表明细胞自噬在植物种子萌发过程中发挥重要作用:(1)自噬基因的表达在种子萌发过程中明显上调，且ATG8蛋白在种子萌发过程中逐渐积累，表明种子萌发过程中细胞自噬被激活；(2)细胞自噬抑制剂3-methyladenine (3-MA)能够显著地抑制拟南芥野生型种子的萌发，拟南芥自噬突变体种子的萌发速度比野生型种子的慢，表明细胞自噬途径在种子萌发过程中发挥正向调控作用但不是种子萌发所必需的。     

Exercise-induced BCL2-regulated autophagy is required for muscle glucose homeostasis

Exercise has beneficial effects on human health, including protection against metabolic disorders such as diabetes. However, the cellular mechanisms underlying these effects are incompletely understood. The lysosomal degradation pathway, autophagy, is an intracellular recycling system that functions during basal conditions in organelle and protein quality control. During stress, increased levels of autophagy permit cells to adapt to changing nutritional and energy demands through protein catabolism. Moreover, in animal models, autophagy protects against diseases such as cancer, neurodegenerative disorders, infections, inflammatory diseases, ageing and insulin resistance. Here we show that acute exercise induces autophagy in skeletal and cardiac muscle of fed mice. To investigate the role of exercise-mediated autophagy in vivo, we generated mutant mice that show normal levels of basal autophagy but are deficient in stimulus (exercise- or starvation)-induced autophagy. These mice (termed BCL2 AAA mice) contain knock-in mutations in BCL2 phosphorylation sites (Thr69Ala, Ser70Ala and Ser84Ala) that prevent stimulus-induced disruption of the BCL2-beclin-1 complex and autophagy activation. BCL2 AAA mice show decreased endurance and altered glucose metabolism during acute exercise, as well as impaired chronic exercise-mediated protection against high-fat-diet-induced glucose intolerance. Thus, exercise induces autophagy, BCL2 is a crucial regulator of exercise- (and starvation)-induced autophagy in vivo, and autophagy induction may contribute to the beneficial metabolic effects of exercise.     

清肺止咳平喘颗粒抗炎和免疫抑制作用初探

目的观察清肺止咳平喘颗粒的抗炎、免疫作用。方法用二甲苯及琼脂建立炎症模型观察清肺止咳平喘 颗粒对急性炎症及慢性炎症的作用;从体液免疫和细胞免疫两方面观察清肺止咳平喘颗粒的免疫作用。结果清 肺止咳平喘颗粒可明显对抗急性炎症和慢性炎症,抑制体液免疫和细胞免疫。结论清肺止咳平喘颗粒有较好的 抗炎和抑制免疫的作用。     

Autophagy fights disease through cellular self-digestion

Autophagy, or cellular self-digestion, is a cellular pathway involved in protein and organelle degradation, with an astonishing number of connections to human disease and physiology. For example, autophagic dysfunction is associated with cancer, neurodegeneration, microbial infection and ageing. Paradoxically, although autophagy is primarily a protective process for the cell, it can also play a role in cell death. Understanding autophagy may ultimately allow scientists and clinicians to harness this process for the purpose of improving human health.     

Autophagy in thymic epithelium shapes the T-cell repertoire and is essential for tolerance

Recognition of self-antigen-derived epitopes presented by major histocompatibility complex class II (MHC II) molecules on thymic epithelial cells (TECs) is critical for the generation of a functional and self-tolerant CD4 T-cell repertoire. Whereas haematopoietic antigen-presenting cells generate MHC-II-peptide complexes predominantly through the processing of endocytosed polypeptides, it remains unknown if and how TECs use unconventional pathways of antigen presentation. Here we address the role of macroautophagy, a process that has recently been shown to allow for endogenous MHC II loading, in T-cell repertoire selection in the mouse thymus. In contrast to most other tissues, TECs had a high constitutive level of autophagy. Genetic interference with autophagy specifically in TECs led to altered selection of certain MHC-II-restricted T-cell specificities and resulted in severe colitis and multi-organ inflammation. Our findings indicate that autophagy focuses the MHC-II-peptide repertoire of TECs on their intracellular milieu, which notably comprises a wide array of otherwise strictly 'tissue-specific' self antigens. In doing so, it contributes to T-cell selection and is essential for the generation of a self-tolerant T-cell repertoire.     

TLR9，先天免疫中重要的抗微生物受体

先天免疫系统是宿主抵御外来微生物入侵的第一道防线，TLR9是先天免疫系统中识别细菌和病毒CpGDNA的主要受体。TLR9信号转导利用MyD88依赖途径．在IRAK-4、IRAK-1、TRAF6和TAKl等关键信号蛋白的协同作用下．激活NF-KB和MAP途径，诱导产生一系列促炎细胞因子和趋化因子，最终引起Thl样炎症反应。TLR9除了有抗感染作用，还与自身免疫紊乱和一些恶性肿瘤发生相关。研究TLR9能帮助了解相关疾病发病机理及寻求预防和治疗的手段。     

Mitochondrial DNA that escapes from autophagy causes inflammation and heart failure

Heart failure is a leading cause of morbidity and mortality in industrialized countries. Although infection with microorganisms is not involved in the development of heart failure in most cases, inflammation has been implicated in the pathogenesis of heart failure. However, the mechanisms responsible for initiating and integrating inflammatory responses within the heart remain poorly defined. Mitochondria are evolutionary endosymbionts derived from bacteria and contain DNA similar to bacterial DNA. Mitochondria damaged by external haemodynamic stress are degraded by the autophagy/lysosome system in cardiomyocytes. Here we show that mitochondrial DNA that escapes from autophagy cell-autonomously leads to Toll-like receptor (TLR) 9-mediated inflammatory responses in cardiomyocytes and is capable of inducing myocarditis and dilated cardiomyopathy. Cardiac-specific deletion of lysosomal deoxyribonuclease (DNase) II showed no cardiac phenotypes under baseline conditions, but increased mortality and caused severe myocarditis and dilated cardiomyopathy 10 days after treatment with pressure overload. Early in the pathogenesis, DNase II-deficient hearts showed infiltration of inflammatory cells and increased messenger RNA expression of inflammatory cytokines, with accumulation of mitochondrial DNA deposits in autolysosomes in the myocardium. Administration of inhibitory oligodeoxynucleotides against TLR9, which is known to be activated by bacterial DNA, or ablation of Tlr9 attenuated the development of cardiomyopathy in DNase II-deficient mice. Furthermore, Tlr9 ablation improved pressure overload-induced cardiac dysfunction and inflammation even in mice with wild-type Dnase2a alleles. These data provide new perspectives on the mechanism of genesis of chronic inflammation in failing hearts.     

Loss of autophagy in the central nervous system causes neurodegeneration in mice

Protein quality-control, especially the removal of proteins with aberrant structures, has an important role in maintaining the homeostasis of non-dividing neural cells. In addition to the ubiquitin-proteasome system, emerging evidence points to the importance of autophagy--the bulk protein degradation pathway involved in starvation-induced and constitutive protein turnover--in the protein quality-control process. However, little is known about the precise roles of autophagy in neurons. Here we report that loss of Atg7 (autophagy-related 7), a gene essential for autophagy, leads to neurodegeneration. We found that mice lacking Atg7 specifically in the central nervous system showed behavioural defects, including abnormal limb-clasping reflexes and a reduction in coordinated movement, and died within 28 weeks of birth. Atg7 deficiency caused massive neuronal loss in the cerebral and cerebellar cortices. Notably, polyubiquitinated proteins accumulated in autophagy-deficient neurons as inclusion bodies, which increased in size and number with ageing. There was, however, no obvious alteration in proteasome function. Our results indicate that autophagy is essential for the survival of neural cells, and that impairment of autophagy is implicated in the pathogenesis of neurodegenerative disorders involving ubiquitin-containing inclusion bodies.     

Suppression of basal autophagy in neural cells causes neurodegenerative disease in mice

Autophagy is an intracellular bulk degradation process through which a portion of the cytoplasm is delivered to lysosomes to be degraded. Although the primary role of autophagy in many organisms is in adaptation to starvation, autophagy is also thought to be important for normal turnover of cytoplasmic contents, particularly in quiescent cells such as neurons. Autophagy may have a protective role against the development of a number of neurodegenerative diseases. Here we report that loss of autophagy causes neurodegeneration even in the absence of any disease-associated mutant proteins. Mice deficient for Atg5 (autophagy-related 5) specifically in neural cells develop progressive deficits in motor function that are accompanied by the accumulation of cytoplasmic inclusion bodies in neurons. In Atg5-/- cells, diffuse, abnormal intracellular proteins accumulate, and then form aggregates and inclusions. These results suggest that the continuous clearance of diffuse cytosolic proteins through basal autophagy is important for preventing the accumulation of abnormal proteins, which can disrupt neural function and ultimately lead to neurodegeneration.     

Toll-like receptor signalling in macrophages links the autophagy pathway to phagocytosis

Phagocytosis and autophagy are two ancient, highly conserved processes involved, respectively, in the removal of extracellular organisms and the destruction of organisms in the cytosol. Autophagy, for either metabolic regulation or defence, involves the formation of a double membrane called the autophagosome, which then fuses with lysosomes to degrade the contents, a process that has similarities with phagosome maturation. Toll-like-receptor (TLR) engagement activates a variety of defence mechanisms within phagocytes, including facilitation of phagosome maturation, and also engages autophagy. Therefore we speculated that TLR signalling might link these processes to enhance the function of conventional phagosomes. Here we show that a particle that engages TLRs on a murine macrophage while it is phagocytosed triggers the autophagosome marker LC3 to be rapidly recruited to the phagosome in a manner that depends on the autophagy pathway proteins ATG5 and ATG7; this process is preceded by recruitment of beclin 1 and phosphoinositide-3-OH kinase activity. Translocation of beclin 1 and LC3 to the phagosome was not associated with observable double-membrane structures characteristic of conventional autophagosomes, but was associated with phagosome fusion with lysosomes, leading to rapid acidification and enhanced killing of the ingested organism.     

中药复方制剂对小鼠红细胞免疫功能的影响

研究了具有益气健脾摄血功效的消红散对实验性肾小球肾炎小鼠红细胞免疫粘附因子的影响。结果表明 ,该方能直接兴奋RBC上的C3b受体 ,增强红细胞免疫粘附活性 ,并且使C3b受体的数目增加 ,促使红细胞清除免疫复合物 ,减少在肾小球基底膜沉积 ,从而缓解炎症或CIC介导的病理过程。说明消红散是治疗GN的一种良好的中药     

水体铜对鲤肠道菌群结构及免疫力的影响

为了解水体重金属铜对鲤肠道菌群多样性、结构及免疫力的影响,以不同质量浓度的水体铜胁迫鲤56d,对鲤肠道菌群α多样性、β多样性、基于属水平的群落组成结构及肠道免疫调控因子和紧密连接蛋白的基因表达进行了分析.结果显示,0.14mg·L-1、0.28mg·L-1处理组与对照组相比,α多样性指数有显著性下降(P0.01),主成分分析(PCA)显示两处理组与对照组群落组成区分明显,优势菌群发生明显变化;同时,两处理组肠道免疫调控因子Il-1β,IL-8,TNF-α及信号分子NF-κB基因表达有显著增加(P0.01),肠道紧密连接蛋白Claudin-3,Claudin-c及免疫调控因子IL-10、信号分子TOR基因表达有显著下降(P0.01).结果表明:中、高质量浓度水体铜胁迫显著降低了鲤肠道菌群的多样性,改变了结构组成,对鲤肠道上皮免疫屏障造成了损伤.