Redox regulation of germline and vulval development in Caenorhabditis elegans

In vitro studies have indicated that reactive oxygen species (ROS) and the oxidation of signaling molecules are important mediators of signal transduction. We have identified two pathways by which the altered redox chemistry of the clk-1 mutants of Caenorhabditis elegans acts in vivo on germline development. One pathway depends on the oxidation of an analog of vertebrate low density lipoprotein (LDL) and acts on the germline through the Ack-related tyrosine kinase (ARK-1) kinase and inositol trisphosphate (IP3) signaling. The other pathway is the oncogenic ras signaling pathway, whose action on germline as well as vulval development appears to be modulated by cytoplasmic ROS.     

Rewiring MAP kinase pathways using alternative scaffold assembly mechanisms

How scaffold proteins control information flow in signaling pathways is poorly understood: Do they simply tether components, or do they precisely orient and activate them? We found that the yeast mitogen-activated protein (MAP) kinase scaffold Ste5 is tolerant to major stereochemical perturbations; heterologous protein interactions could functionally replace native kinase recruitment interactions, indicating that simple tethering is largely sufficient for scaffold-mediated signaling. Moreover, by engineering a scaffold that tethers a unique kinase set, we could create a synthetic MAP kinase pathway with non-natural input-output properties. These findings demonstrate that scaffolds are highly flexible organizing factors that can facilitate pathway evolution and engineering.     

A conserved p38 MAP kinase pathway in Caenorhabditis elegans innate immunity

A genetic screen for Caenorhabditis elegans mutants with enhanced susceptibility to killing by Pseudomonas aeruginosa led to the identification of two genes required for pathogen resistance: sek-1, which encodes a mitogen-activated protein (MAP) kinase kinase, and nsy-1, which encodes a MAP kinase kinase kinase. RNA interference assays and biochemical analysis established that a p38 ortholog, pmk-1, functions as the downstream MAP kinase required for pathogen defense. These data suggest that this MAP kinase signaling cassette represents an ancient feature of innate immune responses in evolutionarily diverse species.     

孕酮对绵羊输卵管上皮细胞β-防御素-1 mRNA表达的影响

旨在研究孕酮(P4)对绵羊输卵管上皮细胞内β-防御素-1( SBD-1) mRNA基因表达的影响及可能参与的信号通路,利用10~(-8) mol/L P4培养绵羊输卵管上皮细胞2 h、6 h、12 h、24 h、48 h,利用RT-qPCR技术检测 SBD-1 mRNA的表达变化,选取P4诱导 SBD-1 mRNA表达的最佳时间。分别添加P4核受体阻断剂RU-486、蛋白激酶C (PKC)阻断剂H-7、蛋白激酶A (PKA)阻断剂H-89干预绵羊输卵管上皮细胞1h,再使用P4处理细胞。结果显示,用10~(-8)mol/L P4诱导绵羊输卵管上皮细胞6 h, SBD-1 mRNA表达显著升高;添加RU-486和H-89显著抑制P4诱导的 SBD-1 mRNA的表达;添加H-7后 SBD-1 mRNA的表达量无显著性差异。以上结果表明,P4诱导的绵羊输卵管上皮细胞中 SBD-1 mRNA的表达通过孕酮核受体(PR)和PKA信号通路介导,与PKC信号通路激活无关。     

Reduced MAP kinase phosphatase-1 degradation after p42/p44MAPK-dependent phosphorylation

The mitogen-activated protein (MAP) kinase cascade is inactivated at the level of MAP kinase by members of the MAP kinase phosphatase (MKP) family, including MKP-1. MKP-1 was a labile protein in CCL39 hamster fibroblasts; its degradation was attenuated by inhibitors of the ubiquitin-directed proteasome complex. MKP-1 was a target in vivo and in vitro for p42(MAPK) or p44(MAPK), which phosphorylates MKP-1 on two carboxyl-terminal serine residues, Serine 359 and Serine 364. This phosphorylation did not modify MKP-1's intrinsic ability to dephosphorylate p44(MAPK) but led to stabilization of the protein. These results illustrate the importance of regulated protein degradation in the control of mitogenic signaling.     

马铃薯油菜素内酯信号激酶基因StBSKs的克隆与序列分析

油菜素内酯是一种参与调控植物生长发育和环境抗性的植物激素,BSKs是BR信号通路中重要的信号转导激酶。以马铃薯为试验材料,通过同源序列检索分析设计特异性引物,采用RT-PCR技术克隆得到BSK基因家族的7个基因,分别命名为StBSK1、StBSK2、StBSK3、StBSK4、StBSK5、StBSK6和StBSK7。其CDS全长分别为1 497、1 479、1 464、1 461、1 476、1 476和1 476 bp,分别编码498、492、487、486、491、491和491个氨基酸。生物信息学分析表明,StBSKs蛋白的等电点为5.14~6.37,均呈弱酸性;这7个蛋白均无跨膜结构域和信号肽;氨基酸序列比对发现,StBSKs蛋白的氨基酸序列在N端存在较大差异。系统进化树分析发现,StBSKs蛋白与同科物种的亲缘关系更近。本研究结果丰富了对马铃薯油菜素内酯信号激酶StBSKs基因的认知,也为进一步深入研究StBSKs的基因功能奠定基础。     

Pheromone signaling mechanisms in yeast: a prototypical sex machine

The actions of many extracellular stimuli are elicited by complexes of cell surface receptors, heterotrimeric guanine nucleotide-binding proteins (G proteins), and mitogen-activated protein (MAP) kinase complexes. Analysis of haploid yeast cells and their response to peptide mating pheromones has produced important advances in our understanding of G protein and MAP kinase signaling mechanisms. Many of the components, their interrelationships, and their regulators were first identified in yeast. Current analysis of the pheromone response pathway (see the Connections Maps at Science's Signal Transduction Knowledge Environment) will benefit from new and powerful genomic, proteomic, and computational approaches that will likely reveal additional general principles that are applicable to more complex organisms.     

Dual positive and negative regulation of wingless signaling by adenomatous polyposis coli

The evolutionarily conserved Wnt/Wingless signal transduction pathway directs cell proliferation, cell fate, and cell death during development in metazoans and is inappropriately activated in several types of cancer. The majority of colorectal carcinomas contain truncating mutations in the adenomatous polyposis coli (APC) tumor suppressor, a negative regulator of Wnt/Wingless signaling. Here, we demonstrate that Drosophila Apc homologs also have an activating role in both physiological and ectopic Wingless signaling. The Apc amino terminus is important for its activating function, whereas the beta-catenin binding sites are dispensable. Apc likely promotes Wingless transduction through down-regulation of Axin, a negative regulator of Wingless signaling. Given the evolutionary conservation of APC in Wnt signal transduction, an activating role may also be present in vertebrates with relevance to development and cancer.     

Specific expression of a tyrosine kinase gene, blk, in B lymphoid cells

Several pathways of transmembrane signaling in lymphocytes involve protein-tyrosine phosphorylation. With the exception of p56lck, a tyrosine kinase specific to T lymphoid cells that associates with the T cell transmembrane proteins CD4 and CD8, the kinases that function in these pathways are unknown. A murine lymphocyte complementary DNA that represents a new member of the src family has now been isolated and characterized. This complementary DNA, termed blk (for B lymphoid kinase), specifies a polypeptide of 55 kilodaltons that is related to, but distinct from, previously identified retroviral or cellular tyrosine kinases. The protein encoded by blk exhibits tyrosine kinase activity when expressed in bacterial cells. In the mouse and among cell lines, blk is specifically expressed in the B cell lineage. The tyrosine kinase encoded by blk may function in a signal transduction pathway that is restricted to B lymphoid cells.     

靶向猪内质网应激通路的microRNAs预测与验证

【目的】预测并验证靶向猪内质网应激通路中关键基因的microRNAs（miRNAs）,为进一步研究miRNAs对猪内质网应激信号通路调控提供理论基础。【方法】首先利用伪狂犬病毒（PRV）感染猪肾上皮（PK15）细胞,高通量测序检测差异表达的miRNAs。然后通过TargetScan预测靶向内质网应激通路关键基因ATF6、IRE1、PERK、GRP78、XBP1的miRNAs。构建含有候选miRNAs作用位点的双荧光素酶报告基因重组载体,并分别与miRNA-mimics共转染幼仓鼠肾（BHK-21）细胞,通过测定荧光素酶活性来验证内质网应激通路关键基因与候选miRNAs的靶标关系。然后在PK15细胞中分别过表达候选miRNAs,利用qRT-PCR和Western blot检测候选miRNAs对内质网应激通路关键基因mRNA和蛋白表达的影响。【结果】miRNA测序结果显示,PRV感染后共引起35条miRNAs差异表达。TargetScan预测显示,靶向ATF6、IRE1、PERK、GRP78、XBP1的交集miRNAs为miR-142-5p、miR-145-5p、miR-150和miR-199a-5p,并将这些交集miRNAs作为候选miRNAs。随后成功构建psiCHECK-2-ATF6-m142-3′UTR、psiCHECK-2-ATF6-m145-3′UTR、psiCHECK-2-ATF6-m150-3′UTR、psiCHECK-2-ATF6-m199-3′UTR、psiCHECK-2-IRE1- m150-3′UTR、psiCHECK-2-IRE1-m142/145/199-3′UTR、psiCHECK-2-PERK-m145/150-3′UTR、psiCHECK- 2-XBP1-m142/ 145/150/199-3′UTR、psiCHECK-2-GRP78-m145/199-3′UTR双荧光素酶报告基因载体。双荧光素酶检测结果显示,miR-142-5p显著抑制psiCHECK-2-ATF6-m142-3′UTR荧光素酶活性。psiCHECK-2-IRE1-m142/145/199-3′UTR分别与miR-142-5p mimics、miR-145-5p mimics、miR-199a-5p mimics共转染,以及psiCHECK-2-XBP1-m142/145/ 150/199-3′UTR分别与miR-142-5p mimics、miR-199a-5p mimics共转染,过表达组的荧光素酶活性均极显著低于阴性对照组。同时miR-145-5p能够显著抑制psiCHECK-2-PERK-m145/ 150-3′UTR荧光素酶活性。这些结果表明miR-142-5p、miR-145-5p和miR-199a-5p均有可能分别靶向ATF6、IRE1、XBP1,而其中miR-142-5p可能同时靶向这三个关键基因调控内质网信号通路。通过qRT- PCR和Western blot分析发现,过表达miR-142-5p后显著抑制ATF6的mRNA和蛋白表达,表明miR- 142-5p靶向ATF6参与调控内质网应激信号通路。【结论】验证了靶向内质网应激通路关键基因ATF6的miRNA- miR-142-5p,为进一步研究miR-142-5p通过调控ATF6的表达而影响内质网应激信号通路奠定了基础。     

外泌体microRNA在猪成熟和闭锁卵泡中的表达差异及功能分析

【目的】通过分析成熟卵泡液外泌体（mature follicular fiuid Exosomes, mffEXs）和闭锁卵泡液外泌体（atretic follicular fiuid Exosomes, affEXs）miRNA的表达差异,探索卵泡液外泌体（EXs）miRNA在卵泡发育和闭锁过程中的调控作用。【方法】本研究通过抽提4—6 mm猪成熟发育和闭锁卵泡的卵泡液分离外泌体,进行粒径分析及Western Blot检测对EXs进行鉴定,接下来对特征性EXs携带的miRNA测序和功能富集分析,筛选关键信号通路和差异基因。最后,将mffEXs和affEXs作为添加剂进行颗粒细胞培养,利用Q-PCR检测技术分析关键基因的表达,验证两类卵泡液内EXs miRNA在卵泡发育中的调控功能。【结果】成功分离了mffEXs和affEXs,对比mffEXs测序结果,affEXs中有90个miRNA上调表达,220个miRNA下调表达,表明了卵泡液中的miRNA表达水平与调控卵泡发育有关;KEGG富集分析结果显示两类卵泡的差异信号通路主要集中在Ras、cAMP、P53和MAPK等信号通路,涉及调控卵母细胞发育、减数分裂以及颗粒细胞细胞周期等生物学功能。在闭锁卵泡中,上调表达的ssc-let-7a和ssc-miR-133a-3p分别潜在靶向调控细胞周期蛋白依赖性激酶（CDK1）和胰岛素生长因子（IGF1）,抑制了G1和G2/M期的运转和类固醇激素代谢,促使颗粒细胞周期运转受阻和颗粒细胞凋亡,引起卵泡闭锁的发生;下调的ssc-miR-21-5p潜在靶向肿瘤抑癌基因（P53）,抑制细胞周期运转,促使颗粒细胞凋亡。在体外培养的颗粒细胞中分别添加mffEXs和affEXs,Q-PCR结果显示CDK1在mffEXs中显著上调表达,而P53显著下调表达,表明了测序分析结果的可靠性。这些结果均显示了affEXs中miRNA表达水平的变化促使颗粒细胞凋亡和细胞周期阻滞,引起卵泡闭锁。【结论】猪affEXs携带miRNA增加了对CDK1、IGF1和P53的表达调控,抑制颗粒细胞细胞周期运转和类固醇激素代谢等信号通路,引起颗粒细胞凋亡,导致卵泡闭锁。     

Correction

The following sentence was omitted from the acknowledgment section of our report "Independent human MAP kinase signal transduction pathways defined by MEK and MKK isoforms" (3 Feb., p. 682)(1) because of an error. "A. Lin and M. Karin are acknowledged for informing us abut the presence of an upstream in-frame initiation codon in the sequence of human MKK4/JNKK/SEK1 before publication."     

加味丹参饮抑制p38MAPK表达保护缺氧/复氧乳鼠心肌细胞损伤的实验研究

目的 观察加味丹参饮含药血清对缺氧/复氧（hypoxia/reoxygenation,H/R）乳鼠心肌细胞p38 MAPK蛋白表达的影响,以探讨其保护心肌的作用机制。方法 将20只SD乳鼠的心肌细胞进行原代培养,建立H/R模型并随机分为H/R组、SB203580（p38MAPK阻断剂组）、加味丹参饮含药血清组,正常心肌细胞组作为对照组。采用T淋巴细胞化学染色法鉴定心肌细胞,罗丹明B（Rhodamine B）染色法观察细胞形态,MTT比色法检测含药血清对乳鼠心肌细胞的毒性,Western-blot法检测MKK3（促分裂原活化蛋白激酶-激酶3）、MKK6（促分裂原活化蛋白激酶-激酶6）、p38MAPK、phospho-p38MAPK蛋白表达。结果 与正常血清对照组比较,H/R组MKK3、MKK6的蛋白表达增多,p38MAPK通路阻断剂SB203580和加味丹参饮均不能减少其表达;p38MAPK、phospho-p38MAPK在H/R时表达均增加（P<0.01）,而SB203580和加味丹参饮含药血清均能减少其表达（P<0.01）。结论 加味丹参饮含药血清预处理可通过抑制缺氧,复氧心肌细胞p38MAPK信号通路发挥保护作用,抑制p38MAPK表达及其磷酸化,减轻心肌细胞损伤,起到保护心肌细胞的作用。     

胃癌SOCS-1基因异常甲基化及其意义

目的：探讨SOCS-1基因在胃癌和癌旁组织中的表达及其启动子甲基化状态与胃癌发生、发展和转移等的关系。方法：采集45例胃癌病人的肿瘤标本、18例癌旁胃粘膜组织以及10例正常胃粘膜组织,运用甲基化特异性PCR反应研究胃癌组织中SOCS-1基因CpG岛甲基化状态,同时运用实时定量PCR分析SOCS-1基因的表达。结果：45例胃癌标本中有21例（46．7％）SOCS-1基因呈CpG岛甲基化,癌旁组织中为2例（11．1％）,而10例正常胃粘膜组织中则未发现SOCS-1基因CpG岛甲基化;SOCS-1基因CpG岛甲基化组的SOCS-1基因表达量与无SOCS-1基因CpG岛甲基化组相比,其基因相对表达量明显减少（P〈0．05）,表明SOCS-1基因CpG岛甲基化可抑制SOCS-1基因表达。与病人临床病理特征相结合比较,发现SOCS-1基因CpG岛甲基化与年龄、性别无关,与肿瘤分化程度及TNM分期等因素有关。结论：在胃癌中存在SOCS-1基因CpG岛甲基化,且由于CpG岛甲基化而促使基因表达抑制。SOCS-1基因CpG岛甲基化在胃癌的发生、发展中可能具有一定的意义。     

p53 dynamics control cell fate

Cells transmit information through molecular signals that often show complex dynamical patterns. The dynamic behavior of the tumor suppressor p53 varies depending on the stimulus; in response to double-strand DNA breaks, it shows a series of repeated pulses. Using a computational model, we identified a sequence of precisely timed drug additions that alter p53 pulses to instead produce a sustained p53 response. This leads to the expression of a different set of downstream genes and also alters cell fate: Cells that experience p53 pulses recover from DNA damage, whereas cells exposed to sustained p53 signaling frequently undergo senescence. Our results show that protein dynamics can be an important part of a signal, directly influencing cellular fate decisions.     

17β-Estradiol Regulates Cultured Immature Boar Sertoli Cell Proliferation via the cAMP-ERK1/2 Pathway and the Estrogen Receptor β

Estrogen plays an important role in regulating Sertoli cell number in the testis. The objective of the study was to identify whether 17β-estradiol affected the proliferation of cultured, immature boar Sertoli cells via the estrogen receptor β （ERβ） and the cAMP-extracellular signal-regulated kinase （ERK1/2） pathway. Low levels （10-10-10-8 mol L-1） of 17β-estradiol increased cell number, but high levels （10-7-10-6 mol L-1） decreased it （P〈0.05）. Sertoli cell number began to recover for an additional 24 h in the medium without 17β-estradiol （10-6 mol L-l） （P〉0.05）. The effects of 17β-estradiol （10-9 mol L-1） peaked at the first 24 h （P〈0.05）. 17β-estradiol activated ERK1/2 from 5 min to 24 h, but the activiy of ERK1/2 began to decrease after 4 h. Both PD98059 and U0126, two ERK inhibitors, blocked cell division （P〈0.05）. 17β-estradiol （10-10-10-6 mol L-1） dose-dependently increased cAMP production （P 〈 0.05）, and both 17β-estradiol （10-9 mol L-1） and forskolin, which increases cAMP levels, induced cell proliferation and activated ERK1/2 （P〈 0.05）. Rp-cAMP, an antagonist of cAMP, blocked this 17β-estradiol activity （P〈 0.05）. Two estrogen receptor antagonists, ICI 182780 and ERβ antagonist （ERβAnt）, reduced Sertoli cell number, cAMP production and ERK1/2 activation （P〈 0.05）, but ERaAnt did not （P〉 0.05）. Therefore, 17β- estradiol mainly promotes pig Sertoli cell proliferation via ERβ to induce cAMP production and ERK activation to promote cell proliferation.     

Using engineered scaffold interactions to reshape MAP kinase pathway signaling dynamics

Scaffold proteins link signaling molecules into linear pathways by physically assembling them into complexes. Scaffolds may also have a higher-order role as signal-processing hubs, serving as the target of feedback loops that optimize signaling amplitude and timing. We demonstrate that the Ste5 scaffold protein can be used as a platform to systematically reshape output of the yeast mating MAP kinase pathway. We constructed synthetic positive- and negative-feedback loops by dynamically regulating recruitment of pathway modulators to an artificial binding site on Ste5. These engineered circuits yielded diverse behaviors: ultrasensitive dose response, accelerated or delayed response times, and tunable adaptation. Protein scaffolds provide a flexible platform for reprogramming cellular responses and could be exploited to engineer cells with novel therapeutic and biotechnological functions.