Drp1-dependent mitochondrial fission regulates p62-mediated autophagy in LPS-induced activated microglial cells

Microglial activation is known to be an important event during innate immunity, but microglial inflammation is also thought to play a role in the etiology of neurodegenerative diseases. Recently, it was reported that autophagy could influence inflammation and activation of microglia. However, little is known about the regulation of autophagy during microglial activation. In this study, we demonstrated that mitochondrial fission-induced ROS can promote autophagy in microglia. Following LPS-induced autophagy, GFP-LC3 puncta were increased, and this was suppressed by inhibiting mitochondrial fission and mitochondrial ROS. Interestingly, inhibition of mitochondrial fission and mitochondrial ROS also resulted in decreased p62 expression, but Beclin1 and LC3B were unaffected. Taken together, these results indicate that ROS induction due to increased LPS-stimulated mitochondrial fission triggers p62 mediated autophagy in microglial cells. Our findings provide the first important clues towards understanding the correlation between mitochondrial ROS and autophagy.

Abbreviations: Drp1; Dynamin related protein 1, LPS; Lipopolysaccharide, ROS; Reactive Oxygen Species, GFP; Green Fluorescent Protein, CNS; Central Nervous System, AD; Alzheimer’s Disease, PD; Parkinson’s Disease, ALIS; Aggresome-like induced structures, iNOS; inducible nitric oxide synthase, Cox-2; Cyclooxygenase-2, MAPK; Mitogen-activated protein kinase; SODs; Superoxide dismutase, GPXs; Glutathione Peroxidase, Prxs; Peroxiredoxins     

The Crohn’s Disease Risk Factor IRGM Limits NLRP3 Inflammasome Activation by Impeding Its Assembly and by Mediating Its Selective Autophagy

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粉背含笑，云南东南部木兰科植物一新种

对产自云南东南部的木兰科植物一新种粉背含笑Magnolia glaucophylla Sima et H. Yu作了描述和绘图。该新种与棕毛含笑Magnolia fulva (H. T. Chang et B. L. Chen) Figlar接近,区别点在于其叶倒卵形、狭倒卵形或倒卵状椭圆形,侧脉每边19~24条;叶柄无毛;心皮20~26枚,成蓇葖时无毛,果瓣厚4~6 mm。     

A plastic SQSTM1/p62-dependent autophagic reserve maintains proteostasis and determines proteasome inhibitor susceptibility in multiple myeloma cells

Multiple myeloma (MM) is the paradigmatic proteasome inhibitor (PI) responsive cancer, but many patients fail to respond. An attractive target to enhance sensitivity is (macro)autophagy, recently found essential to bone marrow plasma cells, the normal counterpart of MM. Here, integrating proteomics with hypothesis-driven strategies, we identified the autophagic cargo receptor and adapter protein, SQSTM1/p62 as an essential component of an autophagic reserve that not only synergizes with the proteasome to maintain proteostasis, but also mediates a plastic adaptive response to PIs, and faithfully reports on inherent PI sensitivity. Lentiviral engineering revealed that SQSTM1 is essential for MM cell survival and affords specific PI protection. Under basal conditions, SQSTM1-dependent autophagy alleviates the degradative burden on the proteasome by constitutively disposing of substantial amounts of ubiquitinated proteins. Indeed, its inhibition or stimulation greatly sensitized to, or protected from, PI-induced protein aggregation and cell death. Moreover, under proteasome stress, myeloma cells selectively enhanced SQSTM1 de novo expression and reset its vast endogenous interactome, diverting SQSTM1 from signaling partners to maximize its association with ubiquitinated proteins. Saturation of such autophagic reserve, as indicated by intracellular accumulation of undigested SQSTM1-positive aggregates, specifically discriminated patient-derived myelomas inherently susceptible to PIs from primarily resistant ones. These aggregates correlated with accumulation of the endoplasmic reticulum, which comparative proteomics identified as the main cell compartment targeted by autophagy in MM. Altogether, the data integrate autophagy into our previously established proteasome load-versus-capacity model, and reveal SQSTM1 aggregation as a faithful marker of defective proteostasis, defining a novel prognostic and therapeutic framework for MM.     

Role of stress-activated OCT4A in the cell fate decisions of embryonal carcinoma cells treated with etoposide

Tumor cellular senescence induced by genotoxic treatments has recently been found to be paradoxically linked to the induction of “stemness.” This observation is critical as it directly impinges upon the response of tumors to current chemo-radio-therapy treatment regimens. Previously, we showed that following etoposide (ETO) treatment embryonal carcinoma PA-1 cells undergo a p53-dependent upregulation of OCT4A and p21Cip1 (governing self-renewal and regulating cell cycle inhibition and senescence, respectively). Here we report further detail on the relationship between these and other critical cell-fate regulators. PA-1 cells treated with ETO display highly heterogeneous increases in OCT4A and p21Cip1 indicative of dis-adaptation catastrophe. Silencing OCT4A suppresses p21Cip1, changes cell cycle regulation and subsequently suppresses terminal senescence; p21Cip1-silencing did not affect OCT4A expression or cellular phenotype. SOX2 and NANOG expression did not change following ETO treatment suggesting a dissociation of OCT4A from its pluripotency function. Instead, ETO-induced OCT4A was concomitant with activation of AMPK, a key component of metabolic stress and autophagy regulation. p16ink4a, the inducer of terminal senescence, underwent autophagic sequestration in the cytoplasm of ETO-treated cells, allowing alternative cell fates. Accordingly, failure of autophagy was accompanied by an accumulation of p16ink4a, nuclear disintegration, and loss of cell recovery. Together, these findings imply that OCT4A induction following DNA damage in PA-1 cells, performs a cell stress, rather than self-renewal, function by moderating the expression of p21Cip1, which alongside AMPK helps to then regulate autophagy. Moreover, this data indicates that exhaustion of autophagy, through persistent DNA damage, is the cause of terminal cellular senescence.     

嘉庚蛸精子形成过程中KIFC1类似物与NUP62分布的免疫荧光分析

精子发生（spermatogenesis）是受基因调控的复杂的发育过程,精子形成不同阶段生精细胞内基因特异性表达导致顶体的发生、精核形态的建成及尾部的形成,精细胞内特有的微管套（manchette）和活动于微管套上的各种分子马达（molecularmotor）在上述各结构形成中发挥重要作用。     

mTORC1通路中氨基酸信号转导相关机制研究进展

雷帕霉素靶点蛋白（target of rapamycin,TOR）作为细胞内重要的生长和代谢调节中枢,主要通过形成两种复合物TORC1与TORC2发挥其功能。其中TORC1接收广泛的细胞内信号,如氨基酸水平、生长因子、能量以及缺氧状态等,通过调控蛋白质合成来促进细胞的增殖与生长。在这些信号当中,氨基酸不仅能够激活TORC1通路,还同时作为其他信号激活TORC1的必需条件。目前,对于生长因子和能量水平激活TORC1过程的分子机制已有较深入的认识,而对于氨基酸信号如何转导至TORC1的分子机制直到近年来才有了新的突破。该文通过梳理已发表的哺乳动物细胞中氨基酸信号调控mTORC1分子机制的相关实验结论,对该领域的研究方向进行了总结和展望。     

Tracking of fast moving neuronal vesicles with ageladine A

O-Linked β-N-acetylglucosaminylation (O-GlcNAcylation) of nucleocytoplasmic proteins is a ubiquitous post-translational modification in multicellular organisms studied so far. Since aberrant O-GlcNAcylation has a link with insulin resistance, it is important to establish the status of O-GlcNAcylation in differentiation of mesenchymal cells such as preadipocytes. In this study, we found a differentiation-dependent drastic increase in the level of O-GlcNAcylation in mouse 3T3-L1 preadipocytes. The occurrence of the increase in O-GlcNAcylation, which correlated with the expression of C/EBPα, was in part due to increased expression of O-GlcNAc transferase. In addition to the well-known O-GlcNAcylated proteins such as nucleoporins and vimentin, pyruvate carboxylase, long chain fatty acid-CoA ligase 1, and Ewing sarcoma protein were identified as the proteins which are heavily O-GlcNAcylated with the adipocyte differentiation. Both adipocyte differentiation and the differentiation-dependent increase in O-GlcNAcylation were blocked by 6-diazo-5-oxo-norleucine. These results suggest that O-GlcNAcylation particilates, at least in part, in adipogenesis.     

Atg8-family interacting motif crucial for selective autophagy

Autophagy is a bulk degradation system conserved among most eukaryotes. Recently, autophagy has been shown to mediate selective degradation of various targets such as aggregated proteins and damaged or superfluous organelles. Structural studies have uncovered the conserved specific interactions between autophagic receptors and Atg8-family proteins through WXXL-like sequences, which we term the Atg8-family interacting motif (AIM). AIM functions in various autophagic receptors such as Atg19 in the cytoplasm-to-vacuole targeting pathway, p62 and neighbor of BRCA1 gene 1 (NBR1) in autophagic degradation of protein aggregates, and Atg32 and Nix in mitophagy, and may link the target-receptor complex to autophagic membranes and/or their forming machineries.     

Phylogenetic distances for neighbour dependent substitution processes

We consider models of nucleotidic substitution processes where the rate of substitution at a given site depends on the state of the neighbours of the site. We first estimate the time elapsed between an ancestral sequence at stationarity and a present sequence. Second, assuming that two sequences are issued from a common ancestral sequence at stationarity, we estimate the time since divergence. In the simplest non-trivial case of a Jukes-Cantor model with CpG influence, we provide and justify mathematically consistent estimators in these two settings. We also provide asymptotic confidence intervals, valid for nucleotidic sequences of finite length, and we compute explicit formulas for the estimators and for their confidence intervals. In the general case of an RN model with YpR influence, we extend these results under a proviso, namely that the equation defining the estimator has a unique solution.