PP54 Sigma-AldrichIgG, Mouse

The Epstein-Barr virus (EBV) nuclear antigen 3 family of protein is critical for the EBV-induced primary B-cell growth transformation process. Using a yeast two-hybrid screen we identified 22 novel cellular partners of the EBNA3s. Most importantly, among the newly identified partners, five are known to play direct and important roles in transcriptional regulation. Of these, the Myc-interacting zinc finger protein-1 (MIZ-1) is a transcription factor initially characterized as a binding partner of MYC. MIZ-1 activates the transcription of a number of target genes including the cell cycle inhibitor CDKN2B. Focusing on the EBNA3A/MIZ-1 interaction we demonstrate that binding occurs in EBV-infected cells expressing both proteins at endogenous physiological levels and that in the presence of EBNA3A, a significant fraction of MIZ-1 translocates from the cytoplasm to the nucleus. Moreover, we show that a trimeric complex composed of a MIZ-1 recognition DNA element, MIZ-1 and EBNA3A can be formed, and that interaction of MIZ-1 with nucleophosmin (NPM), one of its coactivator, is prevented by EBNA3A. Finally, we show that, in the presence of EBNA3A, expression of the MIZ-1 target gene, CDKN2B, is downregulated and repressive H3K27 marks are established on its promoter region suggesting that EBNA3A directly counteracts the growth inhibitory action of MIZ-1.

We have developed an immortalized oral epithelial cell line, ROE2, from fetal transgenic rats harboring temperature-sensitive simian virus 40 large T-antigen gene. The cells grew continuously at either a permissive temperature of 33°C or an intermediate temperature of 37°C. At the nonpermissive temperature of 39°C, on the other hand, growth decreased significantly, and the Sub-G1 phase of the cell cycle increased, indicating that the cells undergo apoptosis at a nonpermissive temperature. Histological and immunocytochemical analyses revealed that ROE2 cells at 37°C had a stratified epithelial-like morphology and expressed cytokeratins Krt4 and Krt13, marker proteins for oral nonkeratinized epithelial cells. Global-scale comprehensive microarray analysis, coupled with bioinformatics tools, demonstrated a significant gene network that was obtained from the upregulated genes. The gene network contained 16 genes, including Cdkn1a, Fos, Krt13, and Prdm1, and was associated mainly with the biological process of skin development in the category of biological functions, organ development. These four genes were validated by quantitative real-time polymerase chain reaction, and the results were nearly consistent with the microarray data. It is therefore anticipated that this cell line will be useful as an in vitro model for studies such as physiological functions, as well as for gene expression in oral epithelial cells.

Emerging evidence suggests that the tumor microenvironment plays a critical role in regulating cancer stem cells (CSCs) and tumor progression through both autocrine and paracrine signaling. Elevated production of bone morphogenetic proteins (BMPs) from human ovarian cancer cells and stroma has been shown to increase CSC proliferation and tumor growth. Here, we report that Lin28, a stem cell factor, binds to BMP4 mRNA in epithelial ovarian carcinoma cells, thereby promoting BMP4 expression at the post-transcriptional level. As co-expression of Lin28 and Oct4 (another stem cell factor) has been implicated in ovarian cancer CSCs, we also determined that high levels of Lin28 are associated with an unfavorable prognosis when co-expressed with high levels of Oct4. Together, these findings uncover a new level of regulation of BMP4 expression and imply a novel Lin28/Oct4/BMP4-mediated mechanism of regulating ovarian tumor cell growth, thus holding potential for the development of new strategies for the diagnosis and treatment of ovarian cancer.

GABAA receptors are ligand-gated Cl- channels, and the intracellular Cl- concentration governs whether GABA function is excitatory or inhibitory. During early brain development, GABA undergoes functional switch from excitation to inhibition: GABA depolarizes immature neurons but hyperpolarizes mature neurons due to a developmental decrease of intracellular Cl- concentration. This GABA functional switch is mainly mediated by the up-regulation of KCC2, a potassium-chloride cotransporter that pumps Cl- outside neurons. However, the upstream factor that regulates KCC2 expression is unclear.We report here that KCC2 is unexpectedly regulated by neuroligin-2 (NL2), a cell adhesion molecule specifically localized at GABAergic synapses. The expression of NL2 precedes that of KCC2 in early postnatal development. Upon knockdown of NL2, the expression level of KCC2 is significantly decreased, and GABA functional switch is significantly delayed during early development. Overexpression of shRNA-proof NL2 rescues both KCC2 reduction and delayed GABA functional switch induced by NL2 shRNAs. Moreover, NL2 appears to be required to maintain GABA inhibitory function even in mature neurons, because knockdown NL2 reverses GABA action to excitatory. Gramicidin-perforated patch clamp recordings confirm that NL2 directly regulates the GABA equilibrium potential. We further demonstrate that knockdown of NL2 decreases dendritic spines through down-regulating KCC2.Our data suggest that in addition to its conventional role as a cell adhesion molecule to regulate GABAergic synaptogenesis, NL2 also regulates KCC2 to modulate GABA functional switch and even glutamatergic synapses. Therefore, NL2 may serve as a master regulator in balancing excitation and inhibition in the brain.

The RNA binding protein Lin28 and its paralog Lin28B are associated with advanced human malignancies. Blocking the biogenesis of let-7 miRNA, a tumor suppressor, by Lin28/Lin28B has been thought to underlie their roles in cancer. Here we report that the mRNA for the human epidermal growth factor receptor 2 (HER2), a HER-family receptor tyrosine kinase known to play a critical role in cell proliferation and survival and also a major therapeutic target in breast cancer, is among several targets of Lin28 regulation. We show that Lin28 stimulates HER2 expression at the posttranscriptional level, and that enforced Lin28 expression promotes cancer cell growth via multiple mechanisms. Consistent with its pleiotropic role in regulating gene expression, Lin28 overexpression in primary breast tumors is a powerful predictor of poor prognosis, representing the first report on the impact of Lin28 expression on clinical outcome in human cancer. While revealing another layer of regulation of HER2 expression in addition to gene amplification, our studies also suggest novel mechanistic insights linking Lin28 expression to disease outcome and imply that targeting multiple pathways is a common mechanistic theme of Lin28-mediated regulation in cancer.

Engagement of α(5)β(1)-integrin by fibronectin (FN) acutely enhances Cav1.2 channel (Ca(L)) current in rat arteriolar smooth muscle and human embryonic kidney cells (HEK293-T) expressing Ca(L). Using coimmunoprecipitation strategies, we show that coassociation of Ca(L) with α(5)- or β(1)-integrin in HEK293-T cells is specific and depends on cell adhesion to FN. In rat arteriolar smooth muscle, coassociations between Ca(L) and α(5)β(1)-integrin and between Ca(L) and phosphorylated c-Src are also revealed and enhanced by FN treatment. Using site-directed mutagenesis of Ca(L) heterologously expressed in HEK293-T cells, we identified two regions of Ca(L) required for these interactions: 1) COOH-terminal residues Ser(1901) and Tyr(2122), known to be phosphorylated by protein kinase A (PKA) and c-Src, respectively; and 2) two proline-rich domains (PRDs) near the middle of the COOH terminus. Immunofluorescence confocal imaging revealed a moderate degree of wild-type Ca(L) colocalization with β(1)-integrin on the plasma membrane. Collectively, our results strongly suggest that 1) upon ligation by FN, Ca(L) associates with α(5)β(1)-integrin in a macromolecular complex including PKA, c-Src, and potentially other protein kinases; 2) phosphorylation of Ca(L) at Y(2122) and/or S(1901) is required for association of Ca(L) with α(5)β(1)-integrin; and 3) c-Src, via binding to PRDs that reside in the II-III linker region and/or the COOH terminus of Ca(L), mediates current potentiation following α(5)β(1)-integrin engagement. These findings provide new evidence for how interactions between α(5)β(1)-integrin and FN can modulate Ca(L) entry and consequently alter the physiological function of multiple types of excitable cells.

Although human skin fibroblast (HSF) elastase has been characterized as a membrane-bound metalloproteinase, little is known about its structure, amino acid sequence, and encoding gene. As there are similarities in the molecular weights and inhibitory profiles of HSF elastase and neprilysin (neutral endopeptidase 24.11 (NEP)), in this study we tested the hypothesis that they are identical using immunoprecipitation and transfection methods. An immunoprecipitation study demonstrated that HSF elastase activity co-immunoprecipitated with anti-NEP in lysates of cultured HSF. Transfection of an NEP cDNA expression vector into COS-1 cells elicited the expression of HSF elastase and NEP activities in the transfected cells. These findings strongly suggest that HSF elastase is identical to NEP, which functions mainly in neuron-associated cells to degrade neuropeptides. Analysis of the expression pattern of NEP revealed that its expression was remarkably up-regulated at the gene, protein, and enzymatic activity levels during the replicative senescence of cultured HSF. Further, the activity of NEP was markedly enhanced in a pattern similar to elastase activity during the intrinsic aging of mouse skin, in UVA-exposed HSF as well as in HSF treated with conditioned medium from UVB-exposed human keratinocytes. Analysis of the cytokine profile for the stimulation of NEP and HSF elastase activities in HSF demonstrated that among the 11 cytokines tested, IL-1α, IL-1β, IL-6, IL-8, and GM-CSF had the potential to significantly stimulate both activities similarly, again supporting the identity of HSF elastase and NEP.

Decreased permeability to imipenem is the most frequent mechanism of imipenem resistance in Pseudomonas aeruginosa. We have determined the presence of OprD porin protein, an imipenem influx channel, in 70 carbapenem-resistant P. aeruginosa clinical isolates by Western blot analysis using rabbit anti-OprD polyclonal antibody. Ninety-eight percent (54 of 55 isolates) of imipenem-and meropenem-resistant P. aeruginosa clinical isolates were negative for OprD porin production. A small group of isolates resistant to imipenem but susceptible to meropenem (2 isolates) produced OprD protein but at a level 3-5 times lower than the wild type P. aeruginosa ATCC27853 strains. This study indicates that the loss of OprD porin protein was the main mechanism for imipenem resistance in P. aeruginosa clinical isolates. Determination of the status of OprD level in P. aeruginosa may help in the better selection of appropriate carbapenem antibiotics.

BACKGROUND: Repetitive exposure of the skin to UVA radiation elicits sagging more frequently than wrinkling, which is mainly attributed to its biochemical mechanism to up-regulate the expression of matrix-metalloproteinase (MMP)-1 and skin fibroblast elastase (SFE)/neutral endopeptidase (NEP), respectively. OBJECTIVE: In this study, we examined the effects of a potent antioxidant, astaxanthin (AX), on the induction of MMP-1 and SFE by UVA treatment of cultured human dermal fibroblasts. METHODS: Those effects were assessed by real-time RT-PCR, Western blotting and enzymic activity assays. RESULTS: UVA radiation elicited a significant increase in the gene expression of MMP-1 as well as SFE/NEP (to a lesser extent) which was followed by distinct increases in their protein and enzymatic activity levels. The addition of AX at concentrations of 4-8 microM immediately after UVA exposure significantly attenuated the induction of MMP-1 and SFE/NEP expression elicited by UVA at the gene, protein and activity levels although both the UVA stimulation and the subsequent AX inhibition were greater for MMP-1 than for SFE/NEP. Analysis of the UVA-induced release of cytokines revealed that UVA significantly stimulated only the secretion of IL-6 among the cytokines tested and that AX significantly diminished only the IL-6 secretion. CONCLUSION: These findings indicate that, based on different effective concentrations of AX, a major mode of action leading to the inhibition elicited by AX depends on inhibition of UVA effects of the reactive oxygen species-directed signaling cascade, but not on interruption of the IL-6-mediated signaling cascade. We hypothesize that AX would have a significant benefit on protecting against UVA-induced skin photo-aging such as sagging and wrinkles. 2010 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.

Lin28 is highly expressed in human and mouse embryonic stem (ES) cells. Here, we show that in mouse ES cells, specific repression of Lin28 results in decreased cell proliferation, while overexpression of Lin28 accelerates cell proliferation. Further, Lin28 associates specifically with ribonucleoprotein particles containing mRNAs for cyclins A and B and cdk4. Importantly, changes in Lin28 levels lead to corresponding changes in the levels of these proteins, and sequences from the 3' untranslated regions of cyclin B and cdk4 mRNAs exhibit stimulatory effects on translation of reporter genes in a Lin28-dependent fashion. Thus, we postulate that Lin28 may play a role in the regulation of translation of genes important for the growth and maintenance of pluripotent cells.