乳腺癌相关的细胞内信号通路

乳腺癌是女性中常见的恶性肿瘤之一.乳腺癌的发生、发展、转移及耐药性的产生与细胞内的信号通路密切相关,其中雌激素受体(estrogen receptor,ER)信号通路、胰岛素样生长因子受体（insulin-like growth factor receptor,IGFR)信号通路和表皮生长因子受体（epidermal growth factor receptor,EGFR）信号通路尤为重要．深入了解ER、IGFR和EGFR三条信号通路的作用机制及它们之间的交叉对话对于寻找新的更有效的肿瘤治疗靶点至关重要．本文综述了近年来有关ER、IGFR和EGFR三条信号通路研究进展及这三条通路与乳腺癌关系．     

Cellular Signaling Pathways and Posttranslational Modifications Mediated by Nematode Effector Proteins

Plant-parasitic cyst and root-knot nematodes synthesize and secrete a suite of effector proteins into infected host cells and tissues. These effectors are the major virulence determinants mediating the transformation of normal root cells into specialized feeding structures. Compelling evidence indicates that these effectors directly hijack or manipulate refined host physiological processes to promote the successful parasitism of host plants. Here, we provide an update on recent progress in elucidating the molecular functions of nematode effectors. In particular, we emphasize how nematode effectors modify plant cell wall structure, mimic the activity of host proteins, alter auxin signaling, and subvert defense signaling and immune responses. In addition, we discuss the emerging evidence suggesting that nematode effectors target and recruit various components of host posttranslational machinery in order to perturb the host signaling networks required for immunity and to regulate their own activity and subcellular localization.The root-knot (Meloidogyne spp.) and cyst (Globodera and Heterodera spp.) nematodes are sedentary endoparasites of the root system in a wide range of plant species. These obligate parasites engage in intricate relationships with their host plants that result in the transformation of normal root cells into specialized feeding sites, which provide the nematodes with all the nutrients required for their development. The initiation and maintenance of functional feeding cells by root-knot nematodes (giant cells) and cyst nematodes (syncytia) seems to be a dynamic process involving active dialogue between the nematodes and their host plants. The nematodes use their stylet, a needle-like apparatus, to deliver effector proteins into the host cells (Williamson and Hussey, 1996; Davis et al., 2004). These effector proteins are mainly synthesized in the nematode esophageal glands, which consist of one dorsal cell and two subventral cells. The activity of these glands is developmentally regulated, with secretions from the two subventral glands being most dynamic during the early stage of infection, consisting of root penetration, migration, and feeding site initiation. Secretions from the single dorsal cell seem to be more active during the sedentary stage of nematode feeding (Hussey and Mims, 1990).Recent progress in the functional characterization of effector proteins from a number of phytonematodes has elucidated diverse mechanisms through which these effectors facilitate the nematode parasitism of host plants. One such mechanism involves depolymerization of the main structural polysaccharide constituents of the plant cell wall by using a diverse collection of extracellular effector proteins (Davis et al., 2011; Wieczorek, 2015). Another mechanism includes the molecular mimicry of host proteins in both form and function (Gheysen and Mitchum, 2011). This strategy could be highly successful when the nematode-secreted effectors imitate host functions to subvert cellular processes in favor of nematodes while escaping the regulation of host cellular processes. Another mechanism of effector action is the modulation of central components of auxin signaling to apparently generate unique patterns of auxin-responsive gene expression, leading to numerous physiological and developmental changes required for feeding site formation and development (Cabrera et al., 2015). In addition, cyst and root-knot nematodes have evolved to efficiently suppress defense responses during their prolonged period of sedentary biotrophic interaction with their hosts. Accordingly, a large number of nematode effectors are engaged in suppressing host immune responses and defense signaling (Hewezi and Baum, 2013; Goverse and Smant, 2014). Finally, there is accumulating evidence that nematode effector proteins target and exploit the host posttranslational machinery to the parasite’s advantage. Posttranslational modifications (PTMs) are tightly controlled and highly specific processes that enable rapid cellular responses to specific stimuli without the requirement of new protein synthesis (Kwon et al., 2006). Phosphorylation, ubiquitination, and histone modifications, among others, have recently been identified as fundamental cellular processes controlling immune signaling pathways (Stulemeijer and Joosten, 2008; Howden and Huitema, 2012; Marino et al., 2012; Salomon and Orth, 2013). This finding underscores the importance of targeting and coopting host posttranslational machinery by pathogen effectors to exert their virulence functions. Here, we review recent progress in the functional characterization of nematode effector proteins and the parasitic strategies that involve modifications of the plant cell wall, molecular mimicry of host factors, alteration of auxin signaling, subversion of defense signaling, and targeting and utilizing the host posttranslational machinery.     

Evaluating Intracellular Signaling Pathways as Biomarkers for Environmental Contaminant Exposures

The number of biomarkers being evaluated as environmental indicatorscontinues to increase even as proposed assessments expand incomplexity. One key to a rational consolidation may lie in clearlyidentifying and characterizing those biochemical pathways sharedamong many biomarkers which are sensitive to environmental perturbation.Recent studies suggest that signal transduction pathways whichare common to many cell types and species may provide multipletargets for the toxic effects of heavy metals. Such intracellularcommunication pathways might provide a useful framework forunderstanding hormetic effects and for predicting responsesto complex contaminant mixtures. Preliminary in vitro experimentstested the effects of mercuric chloride (HgCl₂) and cadmiumchloride (CdCl₂) on signal transduction in cells of the teleostimmune system. Concentrations of inorganic mercury µMsuppressed DNA synthesis and induced rapid influx of radiolabelledcalcium within ten minutes as well as tyrosine phosphorylationof numerous cellular proteins within one minute. Lower concentrations(0.1 – 1 µM) of HgCl₂ which activated cell growthalso induced a slow rise over two minutes in intracellular calciumin cells loaded with the calcium indicator dye, fura-2, butdid not produce detectable tyrosine phosphorylation of leukocyteproteins. Although CdCl₂ >10 µM also suppressed DNAsynthesis, this environmental metal failed to activate cellgrowth or to induce tyrosine kinase activity at any concentrationtested. Future experiments will assess how cells which are exposedto both metals integrate these mixed signals. This approachmay provide a means of predicting cellular responses to multiplecontaminants over broad dose ranges     

WASP Family Proteins Act between Cytoskeleton and Cellular Signaling Pathways

This review considers the proteins of the WASP (Wiskott-Aldrich syndrome protein) family and their role in the regulation of actin-based motility. It contains detailed classification of the WASP family proteins and data on their subcellular localization. Impairments of expression of the WASP family proteins cause certain cell pathologies. The review also deals with domain organization of these proteins and proteins interacting with various domains of the WASP proteins. Special attention is given to analysis of the role of the WASP family proteins in initiating directed actin assembly in the leading edge of the migrating cell and on the surface of some bacteria. Putative pathways of regulation of WASP proteins by various protein ligands and their links with cell signaling systems are considered.     

细菌的小分子信号转导

细菌利用多种小分子进行胞内和胞外的信号转导。它们通过对这些小分子的监测来感知胞外环境的变化,并通过识别这些环境刺激因子将胞外信号跨膜传递到细胞内,转化为胞内第二信使,从而产生相应的生理反应来适应环境的变化。该文介绍细菌群体感应信号转导和胞内环二核苷酸信号转导途径,讨论这两种信号转导途径如何共同调控生物膜的形成、多细胞化和致病能力等诸多细菌细胞生理行为,以及这两种途径之间可能存在的联系。     

A Two-Pulse Cellular Stimulation Test Elucidates Variability and Mechanisms in Signaling Pathways

Mammalian cells respond in a variable manner when provided with physiological pulses of ligand, such as low concentrations of acetylcholine present for just tens of seconds or TNFα for just tens of minutes. For a two-pulse stimulation, some cells respond to both pulses, some do not respond, and yet others respond to only one or the other pulse. Are these different response patterns the result of the small number of ligands being able to only stochastically activate the pathway at random times or an output pattern from a deterministic algorithm responding differently to different stimulation intervals? If the response is deterministic in nature, what parameters determine whether a response is generated or skipped? To answer these questions, we developed a two-pulse test that utilizes different rest periods between stimulation pulses. This “rest-period test” revealed that cells skip responses predictably as the rest period is shortened. By combining these experimental results with a mathematical model of the pathway, we further obtained mechanistic insight into potential sources of response variability. Our analysis indicates that in both intracellular calcium and NFκB signaling, response variability is consistent with extrinsic noise (cell-to-cell variability in protein levels), a short-term memory of stimulation, and high Hill coefficient processes. Furthermore, these results support recent works that have emphasized the role of deterministic processes for explaining apparently stochastic cellular response variability and indicate that even weak stimulations likely guide mammalian cells to appropriate fates rather than leaving outcomes to chance. We envision that the rest-period test can be applied to other signaling pathways to extract mechanistic insight.     

Genome-Wide Pathway Analysis Reveals Different Signaling Pathways between Secreted Lactoferrin and Intracellular Delta-Lactoferrin

Human lactoferrin (LF) is a multifunctional protein involved in immunomodulation, cellular growth, and differentiation. In addition to its secreted form (sLF), an alternative form (ΔLF) lacking the signal sequence has been found to be downregulated in cancer. Although the signaling pathways mediated by LF have been studied in a few cell models, there have been no relevant systemic approaches. Therefore, this study was carried out to identify and compare signaling networks provoked by the two LF isoforms. For this, the two forms were overexpressed in HEK293 cells using the Flp-In T-Rex system, after which genome-wide expression analysis of 18,367 genes was conducted. Pathway analysis of the genes showing altered expression identified pathways which are responsible for cell survival and apoptosis. In addition, the pathways mediated by the two LF forms were within distantly related networks. GPCR, PI3K complex, and POU5F1, which are involved in receptor-mediated pathways, were centered in the sLF network, whereas RIF1, NOS3, and RNPS1, which are involved in intracellular signaling, were centered in the ΔLF network. These results suggest that structural differences between the LF isoforms, mainly glycosylation, determine the fate of LF signaling. Furthermore, these findings provide information relating to the role of ΔLF which is downregulated during carcinogenesis.     

PrPc介导的细胞信号转导

朊病毒病的发生是由于细胞正常朊蛋白PrPc转变成了异常构象的PrPc形式。PrPc的生理学功能目前尚不完全明确,可能与铜离子代谢、脂质摄取以及细胞信号传递有关。PrPc可以与小窝蛋白相互作用而活化Fyn非受体酪氨酸激酶从而引起下游信号通路的转导;可以作为受体与PrPc键合多肽结合后激活cAMP／PKA信号通路;以及引起细胞内钙离子浓度变化而活化信号通路。     

三丁基锡引起的集成式细胞内信号应答反应

海洋环境污染物三丁基锡(tributyltin,TBT)引起的细胞内信号通路应答十分复杂,是一种集成式网络反应(integrated network-like intracellular response)。各种细胞因子及它们之间的作用关系构成类似集成电路样网络式分子反应,组成了细胞内一个个相对独立、又互相关联的反应模块。该文综述了TBT引起的细胞内信号通路转导的集成式网络反应现象,旨在为综合评价污染物危害性提供参考。     

巨噬细胞免疫调变信号——PKA与PKC对MAPK信号通路的调节

以前的研究工作表明,细菌脂多糖（ＬＰＳ）可以调变抑制性巨噬细胞为增强Ｔ、Ｂ淋巴细胞及ＮＫ细胞活性,同时又能保持或增强其抗肿瘤效应。忆报道了在这一复杂的免疫调变过程中伴随有蛋白激酶Ｃ（ＰＫＣ）和促分裂原活化蛋白激酶（ＭＡＰＫ）信号转导通路的激活。为了探索免疫调变过程中其他信号对ＭＡＰＫ通路的影响,以ＬＰＳ调变小鼠腹腔抑制性巨噬细胞为模型,研究了ｃＡＭＰ／ＰＫＡ和佛波酯（ＰＭＡ）／ＰＫＣ信号对ＭＡＰＫ     

Cross Talk Between Substance P and Melittin-Activated Cellular Signaling Pathways in Rat Lactotroph-Enriched Cell Cultures

Abstract: We have investigated the possible interaction (cross talk) between the phospholipase A₂ (PLA₂) and inositol 1,4,5-trisphosphate/protein kinase C (PKC) signaling pathways in rat lactotroph-enriched cell cultures. Melittin, a bee venom peptide, stimulated release of [³H]-arachidonic acid ([³H]AA) from [³H]AA-labeled enriched lactotrophs in a dose-dependent manner. Moreover, melittin and exogenous AA induced a redistribution of PKC catalytic activity and PKCα and β immunoreactivity from the soluble to the particulate fraction in resting and substance P (SP)-stimulated cells. Mellitin had no effect on phospholipase C (PLC) activity. Pretreatment of cell cultures with the PLA₂ inhibitors quinacrine and aristolochic acid resulted in a dose-dependent inhibition of melittin-stimulated PKC isozyme translocation as did the inhibitor of lipoxygenase, nordihydroguaiaretic acid, whereas the cyclooxygenase inhibitor indomethacin had no effect. SP and the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) dose-dependently increased levels of [³H]AA released from cells. Pretreatment of cell cultures with quinacrine reduced the effect of SP on [³H]AA formation. After long-term treatment (24 h) of cells with TPA, the effect of TPA on [³H]AA production was not different from control, whereas SP still displayed [³H]AA-releasing abilities although not at full scale. Pretreatment of cells with thapsigargin, U 73122, methoxyverapamil, and RHC 80267, an inhibitor of diacylglycerol lipase, all resulted in reduced SP-stimulated [³H]AA liberation. Treatment of cell cultures with pertussis toxin (PTX) reduced the release of [³H]AA induced by SP, whereas PTX had no effect on SP-stimulated generation of ³H-inositol phosphates. On the basis of these results, it is concluded that (1) the PLA₂ pathways interfere with the phosphoinositide-PLC signaling system at the level of PKC isozymes α and β, the product responsible for this interaction being either AA or a metabolite produced by the action of lipoxygenase; (2) SP and TPA are able to activate the PLA₂ pathway at a level at or beyond PLA₂, and this effect is mediated, in part, through PKCα and β species and (for SP) intracellular Ca²⁺ recruited from internal stores as well as from external sources; and (3) SP also activates PLA₂ through a PTX-sensitive pathway distinct from the one coupled to phosphoinositide-PLC, which is PTX insensitive.     

Effect of Redox Balance Alterations on Cellular Localization of LAT and Downstream T-Cell Receptor Signaling Pathways

The integral membrane protein linker for activation of T cells (LAT) is a central adapter protein in the T-cell receptor (TCR)-mediated signaling pathways. The cellular localization of LAT is extremely sensitive to intracellular redox balance alterations. Reduced intracellular levels of the antioxidant glutathione (GSH), a hallmark of chronic oxidative stress, resulted in the membrane displacement of LAT, abrogated TCR-mediated signaling and consequently hyporesponsiveness of T lymphocytes. The membrane displacement of LAT is accompanied by a considerable difference in the mobility of LAT upon native and nonreducing denaturing polyacrylamide gel electrophoresis analysis, a finding indicative of a conformational change. Targeted mutation of redox-sensitive cysteine residues within LAT created LAT mutants which remain membrane anchored under conditions of chronic oxidative stress. The expression of redox-insensitive LAT mutants allows for restoration of TCR-mediated signal transduction, whereas CD28-mediated signaling pathways remained impaired. These results are indicative that the membrane displacement of LAT as a result of redox balance alterations is a consequence of a conformational change interfering with the insertion of LAT into the plasma membrane. Conclusively, the data suggest a role for LAT as a crucial intermediate in the sensitivity of TCR signaling and hence T lymphocytes toward chronic oxidative stress.     

病毒感染对宿主TLRs模式识别与免疫应答信号的影响

TLRs是一类古老的天然模式识别分子,通过识别病毒的PAMPs,活化依赖和非依赖于MyD88的信号通路,诱导IFNs、促炎性细胞因子和趋化因子等分子的释放和表达,清除病毒的感染;同时,病毒为了感染宿主,采用多种免疫逃避策略干扰机体TLRs的信号,尤其调节MyD88、NF-κB、TRIF和IRFs等重要信号分子,以逃避机体天然PRRs的监视、识别和清除。因此,本文重点以VACV、HCV和HIV为例,介绍病毒感染对宿主TLRs模式识别与免疫应答信号的调节,以进一步理解病毒与宿主相互作用的复杂性,为病毒病的有效防治提供理论依据。