Dynamic regulation of innate immunity by ubiquitin and ubiquitin-like proteins

Protein post-translational modifications (PTMs) are central to the host innate immune regulations. Dynamically, PTMs fine-tune the spatial and temporary responses of immune- and non-immune-cells, in accordance with extracellular and intracellular stresses. Ubiquitin and ubiquitin-like proteins (Ubls) are emerging as the important multi-functional signals, controlling the activation, stability, affinity and location of many signaling proteins. Recent investigations, at the molecular-cellular-animal models, have shed new light on the versatility of the ubiquitin, SUMO and ISG15, for shaping the strength and duration of the innate immune responses. This review summarizes our current knowledge on the functions and regulatory mechanisms of the ubiquitin and Ubls in the innate immunity, the first line of host defense against microbial infection.     

Simultaneous knockdown of BRAF and expression of INK4A in melanoma cells leads to potent growth inhibition and apoptosis

Abnormal BRAF and p16INK4A co-exist in 60% of melanomas. BRAF mutation also occurs in 80% of benign nevi where it turns-on p16INK4A resulting in proliferative senescence; loss of p16INK4A removes the inhibitory block leading to melanoma development. Since only melanomas with wild-type BRAF have amplified CDK4 and cyclin D1 genes, p16INK4A-CDK4/6-cyclin D pathway is viewed as linearly downstream of BRAF. Thus, co-occurrence of aberrant BRAF and INK4A may be remnant of changes during melanoma formation without functional significance. To explore this notion, we simultaneously knocked down BRAF (via siRNA) and expressed INK4A cDNA in melanoma cells and observed enhanced growth inhibition. Notably, although each alone had no statistically significant effect on apoptosis, co-expression of BRAF siRNA and INK4A cDNA caused potent apoptosis, which was associated with up-regulation of BIM and down-regulation of BCL2. Our results suggest that aberrant BRAF and INK4A cooperate to promote proliferation and survival of melanoma cells.     

Eukaryotic cell signaling and transcriptional activation induced by bacterial porins

The protein composition of the outer membrane of Gram-negative bacteria consists of about 20 immunochemically distinct proteins, termed outer membrane proteins (OMPs). Apart from their structural role, OMPs have been shown to have other functions, particularly with regard to transport, and have been classified as permeases and porins. Porins, during their interaction with the host, are immunogenic and also directly stimulate several cellular functions. Porins work both as molecules present on the bacterial surface and as molecules released by bacteria. Lipopolysaccharide and OMPs, the major structural macromolecular constituents of the outer membrane, carry out a fundamental role in the pathogenesis of Gram-negative infections. This brief review describes the multiple facets of the biological activities of porins both in vitro and in vivo, particularly focusing on their ability to induce the expression of cytokines and other factors that modulate cellular activities with either pathological or adaptive consequences. This brief discussion will focus on the signal transmission mechanisms induced by bacterial porins.     

Identification of novel 3,5-diarylpyrazoline derivatives containing salicylamide moiety as potential anti-melanoma agents

There is an accumulating body of experimental evidences validating oncogenic BRAF^V600E as a therapeutic target and offering opportunities for anti-melanoma drug development. Encouraged by the positive results of pyrazole derivatives as BRAF^V600E inhibitors, we sought to design diverse novel potential BRAF^V600E inhibitors as antitumor agents based on pyrazole skeleton. In silico and in vitro screening of our designed pyrazole derivatives has identified Hit 1 as BRAF^V600E inhibitor. Based on its structure and through further structure modification, compound 25, which exhibited the most potent inhibitory activity with an IC₅₀ value of 0.16 μM for BRAF^V600E and GI₅₀ value of 0.24 μM for mutant BRAF-dependent melanoma cells, was obtained. The 3D-QSAR models and the molecular docking simulation were introduced to analyze the structure–activity relationship.     

Towards an understating of signal transduction protein interaction networks

Protein network analysis has witnessed a number of advancements in the past for understanding molecular characteristics for important network topologies in biological systems. The signaling pathway regulates cell cycle progression and anti-apoptotic molecules. This pathway is also involved in maintaining cell survival by modulating the activity of apoptosis through RAS, P13K, AKT and BAD activities. The importance of protein-protein interactions to improve usability of the interactome by scoring and ranking interaction data for proteins in signal transduction networks is illustrated using available data and resources.     

Deregulation of DUSP activity in EGFR-mutant lung cancer cell lines contributes to sustained ERK1/2 signaling

Lung cancers demonstrate loss of cellular signaling control pathways. EGFR-mutant non-small cell lung cancer cell lines constitutively express active ERK1/2 and require ERK activity for survival. DUSP4 is a negative regulator of ERK activity and is up-regulated in EGFR-mutant lung cancer cell lines relative to K-ras mutant cells. Both DUSP4 and family member, DUSP1, can bind ERK in vitro. However, only DUSP1 has detectable binding to ERK in vivo in cell lines of either genotype. Depletion of DUSP4 in EGFR-mutant cells unexpectedly results in loss of pERK whereas loss of DUSP4 in K-ras mutant cells predictably yields increased pERK. These data support a role for DUSP4, and perhaps DUSP1, as a positive activator of ERK in EGFR-mutant lung cancer cell lines independent of the ability to bind to ERK.     

Possible involvement of two mechanisms of signal transduction in α1-adrenergic action. Selective effect of cycloheximide

We have previously suggested that the effects of α₁-adrenergic agents on hepatocyte metabolism involve two pathways: (a) a calcium-independent, insulin-sensitive process which is modulated by glucocorticoids; and (b) a calcium-dependent, insulin-insensitive process which is modulated by thyroid hormones. Cycloheximide stimulated ureogenesis through a prazosin-sensitive mechanism in liver cells (α₁-adrenergic). The effect of cycloheximide was insulin-insensitive and calcium-dependent. Furthermore, a clear effect of cycloheximide was observed in hepatocytes obtained from adrenalectomized animals, whereas no effect was observed in cell from hypothyroid rats. The effects of epinephrine and cycloheximide were blocked by phorbol esters in all the conditions tested. Binding competition experiments indicated that cycloheximide interacts with only a fraction of the α₁-adrenergic sites labeled with [³H]prazosin. It is suggested that cycloheximide activates preferentially one of the pathways involved in the α₁-adrenergic action in liver cells.     

细菌内毒素耐受小鼠肝细胞内信号转导相关分子的表达变化

目的 探讨细菌脂多糖(LPS)相关的信号转导分子在内毒素耐受小鼠肝细胞内的变化和作用.方法 将实验小鼠随机分为3大组:敏感组以LPS(2 μg)合并半乳糖胺(D-GalN)直接攻击;耐受组预先以LPS(0.1 μg)注射,再在不同耐受时间点(3 h、1 d、2 d、7 d)以LPS(2 μg)/D-GalN联合攻击.对照组注射生理盐水、D-GalN或LPS(0.1 μg);利用反转录-聚合酶链反应(RT-PCR)及蛋白质印迹法(Western印迹法)测定各信号分子在转录和表达水平的变化.结果 LPS刺激可显著诱导敏感组小鼠肝细胞的Toll样受体(TLR)-4基因转录和蛋白表达;而在LPS预处理的耐受组,TLR-4 mRNA和蛋白的水平均明显低于敏感组(P＜0.01);耐受组中白细胞介素受体相关激酶1(IRAK-1)基因的表达水平也比敏感组明显低(P＜0.01).但是肿瘤坏死因子受体相关因子-6(TRAF-6)的表达水平则不受LPS预处理的影响.NF-κB组分分析显示,敏感组IκB的降解明显高于耐受组;耐受组的p65亚基表达显著降低,而p50亚基表达升高.结论 内毒素耐受可使NF-κB的p65亚基表达下调、p50亚基表达升高和抑制IκB的降解,而TLR-4和IRAK-I的表达下调是诱导产生内毒素耐受性的重要因素.     

Ethylene Receptors: Ethylene Perception and Signal Transduction

Ethylene is sensed by a family of receptors that can be divided into two subfamilies based on phylogenetic analysis and some shared structural features. In this review we focus on the mechanistic aspects of how the receptors function in plants to transduce the ethylene signal. Recent work has led to new insights into how ethylene binds to the receptors and how this binding may induce a conformational change to regulate signaling. Additional studies point to several possible mechanisms for signal output by the receptors, which may involve changes in enzymatic activity and/or conformational changes. Other studies indicate the importance of interactions, both physical and genetic, between the receptors and early components of the signaling pathway, in particular, the Raf-like kinase CTR1, which functions as an integral component of the ethylene receptor signaling complex. The current model for signaling in Arabidopsis supports differing contributions from the receptors, with subfamily-1 receptors playing a more significant role than the subfamily-2 receptors in transmitting the ethylene signal.     

菌根共生体形成过程中的信号识别与转导机制

在菌根共生体建立过程中存在信号分子的多重性和信号通路的多样性以及共牛体特异基因的表达调控,从分子水平上揭示了菌根整个发育过程。     

乙烯信号传导的研究进展

植物内源激素乙烯作为信号分子通过信号传导途径调节相关基因表达 ,控制植物体的多种生理活动。乙烯信号传导途径中的许多基因已被克隆定性 ,综述了乙烯信号传导途径中的相关基因的功能及乙烯信号传导模式。     

赤霉素信号转导与植物的矮化

论述近年来在拟南芥、水稻等模式植物中赤霉素信号转导的研究进展。通过对赤霉素相关突变体的生理研究 ,鉴定出几个介入赤霉素信号转导过程的重要基因 ,并对这些基因的产物进行分析 ,根据相应的蛋白特征结构域 ,推导了它们可能具有的功能。利用双突变体 ,分析了这些基因的上下游关系 ,确定了在植物中 ,GA信号转导的几个途径。在此基础上提出了赤霉素信号转导的基本模式 :阻遏是GA信号转导过程中最基本的方式 ,GA信号通过去除阻遏作用来激活转导途径 ,从而调节GA相关的生长与发育。     

菌根共生体形成过程中的信号识别与转导机制

在菌根共生体建立过程中存在信号分子的多重性和信号通路的多样性以及共牛体特异基因的表达调控,从分子水平上揭示了菌根整个发育过程。     

植物赤霉素矮化突变体研究进展

赤霉素(GAs)在植物种子萌发、茎的伸长和花的发育等方面起着非常重要的作用。近年来,随着研究手段和技术不断进步,对赤霉素(GA)生物合成和信号传导过程中相关基因的研究取得了惊人的进展。与GA有关的矮化突变体主要有GA缺陷型和不敏感型两类,本文对与GA生物合成和信号传导过程中有关的这两类矮突变体的研究进展进行综述。对这些这些突变体的研究促进了对赤霉素生物合成和信号传导途径的认识,同时为赤霉素更好地利用提供了科学依据。     

The promise of a protist: the Dictyostelium genome project

The genome of Dictyostelium discoideum is being sequenced by an international consortium and is scheduled for completion in the next few years. The sequence will accelerate research into a number of phenomena carried out by these versatile soil amoebae, providing insight into analogous processes that operate in a wide range of eukaryotes. These include the dynamic regulation of the cytoskeleton during chemotaxis, intercellular communication during multicellular development and the intracellular growth of bacterial pathogens. The current state of the genome project is summarized and the challenges of sequencing a genome with unusually low guanine and cytosine content and with a bimodal base composition distribution are discussed. The prospects for functional analyses at the genomic scale are also considered. Electronic Publication