sFRP1 Expression Induces miRNAs That Modulate Wnt Signaling in Chronic Myeloid Leukemia Cells

Molecular Biology - Chronic myeloid leukemia is a clonal hematopoietic stem cell disease characterized by myeloid expansion. The hallmark of the disease is the Philadelphia chromosome, which...     

A Synthetic Lethal Interaction between APC/C and Topoisomerase Poisons Uncovered by Proteomic Screens

1. Download : Download full-size image

     

黑色素瘤相关抗原MAAT1p15与LRP6的相互作用及其对Wnt信号通路的调控

为了深入研究Wnt信号的传导机制 ,利用GAL4酵母双杂交系统 ,以Wnt受体LRP6的胞内区为诱饵蛋白 ,筛选小鼠 11 5d胚胎cDNA文库 ,发现了一个新的LRP6相互作用蛋白 :黑色素瘤相关抗原MAAT1p15 (melanoma associatedantigenrecognizedbycytotoxicTlymphocytesp15 ) .免疫共沉淀方法证明了LRP6胞内区和MAAT1p15在哺乳动物细胞中也存在相互作用 .荧光素酶报告系统分析实验显示 ,MAAT1p15能够明显增强Wnt1和LRP6响应的下游基因的转录活性 ,提示MAAT1p15可能是LRP6的一个辅助蛋白     

Poliovirus-1 Inactivation and Interaction with Biofilm: a Pilot-Scale Study

A pilot-scale study was initiated to examine the behavior of viruses pulse injected into a distribution system. The influence of a free-chlorine residual and that of virus preadsorption to clay particles was evaluated by tracing the viruses both in the water flow and after elution from the biofilm. These experiments demonstrated, first, that virus preadsorption on 40 mg of Na-montmorillonite per liter increased the residence time of the viruses within the pilot plant by roughly three times and, second, that preadsorption to clay did not prevent viruses from being inactivated by chlorine. Moreover, with no clay added, a greater amount of viruses was recovered from the biofilm than from the water flow (by a factor of 2 or 10 in the absence or presence of chlorine, respectively), indicating a tendency for virus accumulation within biofilms.     

Multivesicular GSK3 Sequestration upon Wnt Signaling Is Controlled by p120-Catenin/Cadherin Interaction with LRP5/6

1. Download : Download high-res image (303KB)
2. Download : Download full-size image

     

Ethanol Induces Apoptosis in Cerebellar Granule Neurons by Inhibiting Insulin-Like Growth Factor 1 Signaling

Abstract: The ability of ethanol to interfere with insulin-like growth factor 1 (IGF-1)-mediated cell survival was examined in primary cultured cerebellar granule neurons. Cells underwent apoptosis when switched from medium containing 25 m M K⁺ to one containing 5 m M K⁺. IGF-1 protected granule neurons from apoptosis in medium containing 5 m M K⁺. Ethanol inhibited IGF-1-mediated neuronal survival but did not inhibit IGF-1 receptor binding or the neurotrophic action of elevated K⁺, and failed to potentiate cell death in the presence of 5 m M K⁺. Inhibition of neuronal survival by ethanol was not reversed by increasing the concentration of IGF-1. Significant inhibition by ethanol (15–20%) was observed at 1 m M and was half-maximal at 45 m M . The inhibition of IGF-1 protection by ethanol corresponded to a marked reduction in the phosphorylation of insulin receptor substrate 1, the binding of phosphatidylinositol 3-kinase (PI 3-kinase), and a block of IGF-1-stimulated PI 3-kinase activity. The neurotrophic response of IGF-1 was also inhibited by the PI 3-kinase inhibitor LY294002, the protein kinase C inhibitor chelerythrine chloride, and the protein kinase A inhibitor KT5720, but unaffected by the mitogen-activated protein kinase kinase inhibitor PD 98059. These data demonstrate that ethanol promotes cell death in cerebellar granule neurons by inhibiting the antiapoptotic action of IGF-1.     

The Signaling Mechanism of Arabidopsis CRY1 Involves Direct Interaction with COP1

Dark-grown transgenic Arabidopsis seedlings expressing the C-terminal domains (CCT) of the cryptochrome (CRY) blue light photoreceptors exhibit features that are normally associated only with light-grown seedlings, indicating that the signaling mechanism of Arabidopsis CRY is mediated through CCT. The phenotypic properties mediated by CCT are remarkably similar to those of the constitutive photomorphogenic1 (cop1) mutants. Here we show that Arabidopsis cryptochrome 1 (CRY1) and its C-terminal domain (CCT1) interacted strongly with the COP1 protein. Coimmunoprecipitation studies showed that CRY1 was bound to COP1 in extracts from both dark- and light-grown Arabidopsis. An interaction also was observed between the C-terminal domain of Arabidopsis phytochrome B and COP1, suggesting that phytochrome signaling also proceeds, at least in part, through direct interaction with COP1. These findings give new insight into the initial step in light signaling in Arabidopsis, providing a molecular link between the blue light receptor, CRY1, and COP1, a negative regulator of photomorphogenesis.     

Negative Feedback Regulation of Wnt4 Signaling by EAF1 and EAF2/U19

Previous studies indicated that EAF (ELL-associated factor) family members, EAF1 and EAF2/U19, play a role in cancer and embryogenesis. For example, EAF2/U19 may serve as a tumor suppressor in prostate cancer. At the same time, EAF2/U19 is a downstream factor in the non-canonical Wnt 4 signaling pathway required for eye development in Xenopus laevis, and along with EAF1, contributes to convergence and extension movements in zebrafish embryos through Wnt maintenance. Here, we used zebrafish embryos and mammalian cells to show that both EAF1 and EAF2/U19 were up-regulated by Wnt4 (Wnt4a). Furthermore, we found that EAF1 and EAF2/U19 suppressed Wnt4 expression by directly binding to the Wnt4 promoter as seen in chromatin immunoprecipitation assays. These findings indicate that an auto-regulatory negative feedback loop occurs between Wnt4 and the EAF family, which is conserved between zebrafish and mammalian. The rescue experiments in zebrafish embryos showed that early embryonic development required the maintenance of the appropriate levels of Wnt4a through the feedback loop. Others have demonstrated that the tumor suppressors p63, p73 and WT1 positively regulate Wnt4 expression while p21 has the opposite effect, suggesting that maintenance of appropriate Wnt4 expression may also be critical for adult tissue homeostasis and prevention against tumor initiation. Thus, the auto-regulatory negative feedback loop that controls expression of Wnt4 and EAF proteins may play an important role in both embryonic development and tumor suppression. Our findings provide the first convincing line of evidence that EAF and Wnt4 form an auto-regulatory negative feedback loop in vivo.     

Reciprocal Negative Regulation of PDK1 and ASK1 Signaling by Direct Interaction and Phosphorylation

Cell survival and death-inducing signals are tightly associated with each other, and the decision as to whether a cell survives or dies is determined by controlling the relationship between these signals. However, the mechanism underlying the reciprocal regulation of such signals remains unclear. In this study, we reveal a functional association between PDK1 (3-phosphoinositide-dependent protein kinase 1), a critical mediator of cell survival, and ASK1 (apoptosis signal-regulating kinase 1), an apoptotic stress-activated MAPKKK. The physical association between PDK1 and ASK1 is mediated through the pleckstrin homology domain of PDK1 and the C-terminal regulatory domain of ASK1 and is decreased by ASK1-activating stimuli, such as H₂O₂, tumor necrosis factor α, thapsigargin, and ionomycin, as well as insulin, a PDK1 stimulator. Wild-type PDK1, but not kinase-dead PDK1, negatively regulates ASK1 activity by phosphorylating Ser⁹⁶⁷, a binding site for 14-3-3 protein, on ASK1. PDK1 functionally suppresses ASK1-mediated AP-1 transactivation and H₂O₂-mediated apoptosis in a kinase-dependent manner. On the other hand, ASK1 has been shown to inhibit PDK1 functions, including PDK1-mediated regulation of apoptosis and cell growth, by phosphorylating PDK1 at Ser³⁹⁴ and Ser³⁹⁸, indicating that these putative phosphorylation sites are involved in the negative regulation of PDK1 activity. These results provide evidence that PDK1 and ASK1 directly interact and phosphorylate each other and act as negative regulators of their respective kinases in resting cells.     

Selective Protection of an ARF1-GTP Signaling Axis by a Bacterial Scaffold Induces Bidirectional Trafficking Arrest

1. Download : Download full-size image