Helicobacter pylori Exploits Host Membrane Phosphatidylserine for Delivery, Localization, and Pathophysiological Action of the CagA Oncoprotein

SummaryWhen delivered into gastric epithelial cells via type IV secretion, Helicobacter pylori CagA perturbs host cell signaling and thereby promotes gastric carcinogenesis. However, the mechanisms of CagA delivery, localization, and action remain poorly understood. We show that direct contact of H. pylori with epithelial cells induces externalization of the inner leaflet enriched host phospholipid, phosphatidylserine, to the outer leaflet of the host plasma membrane. CagA, which is exposed on the bacterial surface via type IV secretion, interacts with the externalized phosphatidylserine to initiate its entry into cells. CagA delivery also requires energy-dependent host cell processes distinct from known endocytic pathways. Within polarized epithelial cells, CagA is tethered to the inner leaflet of the plasma membrane through interaction with phosphatidylserine and binds the polarity-regulating host kinase PAR1/MARK to induce junctional and polarity defects. Thus, host membrane phosphatidylserine plays a key role in the delivery, localization, and pathophysiological action of CagA

Effects of a Chemically Synthesized Leucine-Rich Amelogenin Peptide (csLRAP) on Chondrogenic and Osteogenic Cells

福岡歯科大学2017年

CENP-A Phosphorylation by Aurora-A in Prophase Is Required for Enrichment of Aurora-B at Inner Centromeres and for Kinetochore Function

AbstractThe Aurora (Ipl1)-related kinases are universal regulators of mitosis. We now show that Aurora-A, in addition to Aurora-B, regulates kinetochore function in human cells. A two-hybrid screen identified the kinetochore component CENP-A as a protein that interacts with Aurora-A. Aurora-A phosphorylated CENP-A in vitro on Ser-7, a residue also known to be targeted by Aurora-B. Depletion of Aurora-A or Aurora-B by RNA interference revealed that CENP-A is initially phosphorylated in prophase in a manner dependent on Aurora-A, and that this reaction appears to be required for the subsequent Aurora-B-dependent phosphorylation of CENP-A as well as for the restriction of Aurora-B to the inner centromere in prometaphase. Prevention of CENP-A phosphorylation also led to chromosome misalignment during mitosis as a result of a defect in kinetochore attachment to microtubules. Our observations suggest that phosphorylation of CENP-A on Ser-7 by Aurora-A in prophase is essential for kinetochore function

Conversion of Helicobacter pylori CagA from senescence inducer to oncogenic driver through polarity-dependent regulation of p21

The Helicobacter pylori CagA bacterial oncoprotein plays a critical role in gastric carcinogenesis. Upon delivery into epithelial cells, CagA causes loss of polarity and activates aberrant Erk signaling. We show that CagA-induced Erk activation results in senescence and mitogenesis in nonpolarized and polarized epithelial cells, respectively. In nonpolarized epithelial cells, Erk activation results in oncogenic stress, up-regulation of the p21Waf1/Cip1 cyclin-dependent kinase inhibitor, and induction of senescence. In polarized epithelial cells, CagA-driven Erk signals prevent p21Waf1/Cip1 expression by activating a guanine nucleotide exchange factor–H1–RhoA–RhoA-associated kinase–c-Myc pathway. The microRNAs miR-17 and miR-20a, induced by c-Myc, are needed to suppress p21Waf1/Cip1 expression. CagA also drives an epithelial-mesenchymal transition in polarized epithelial cells. These findings suggest that CagA exploits a polarity-signaling pathway to induce oncogenesis

Helicobacter pylori CagA Triggers Expression of the Bactericidal Lectin REG3γ via Gastric STAT3 Activation

Background: Most of what is known about the Helicobacter pylori (H. pylori) cytotoxin, CagA, pertains to a much-vaunted role as a determinant of gastric inflammation and cancer. Little attention has been devoted to potential roles of CagA in the majority of H. pylori infected individuals not showing oncogenic progression, particularly in relation to host tolerance. Regenerating islet-derived (REG)3c encodes a secreted C-type lectin that exerts direct bactericidal activity against Grampositive bacteria in the intestine. Here, we extend this paradigm of lectin-mediated innate immunity, showing that REG3c expression is triggered by CagA in the H. pylori-infected stomach. Methodology/Principal Findings: In human gastric mucosal tissues, REG3c expression was significantly increased in CagApositive, compared to CagA-negative H. pylori infected individuals. Using transfected CagA-inducible gastric MKN28 cells, we recapitulated REG3c induction in vitro, also showing that tyrosine phosphorylated, not unphosphorylated CagA triggers REG3c transcription. In concert with induced REG3c, pro-inflammatory signalling downstream of the gp130 cytokine coreceptor via the signal transducer and activator of transcription (STAT)3 and transcription of two cognate ligands, interleukin(IL)-11 and IL-6, were significantly increased. Exogenous IL-11, but not IL-6, directly stimulated STAT3 activation and REG3c transcription. STAT3 siRNA knockdown or IL-11 receptor blockade respectively abrogated or subdued CagAdependent REG3c mRNA induction, thus demonstrating a requirement for uncompromised signalling via the IL-11/STAT

CEACAM6 is upregulated by <i>Helicobacter pylori</i> CagA and is a biomarker for early gastric cancer

Early detection of gastric cancers saves lives, but remains a diagnostic challenge. In this study, we aimed to identify cell-surface biomarkers of early gastric cancer. We hypothesized that a subset of plasma membrane proteins induced by the Helicobacter pylori oncoprotein CagA will be retained in early gastric cancers through non-oncogene addiction. An inducible system for expression of CagA was used to identify differentially upregulated membrane protein transcripts in vitro. The top hits were then analyzed in gene expression datasets comparing transcriptome of gastric cancer with normal tissue, to focus on markers retained in cancer. Among the transcripts enriched upon CagA induction in vitro, a significant elevation of CEACAM6 was noted in gene expression datasets of gastric cancer. We used quantitative digital immunohistochemistry to measure CEACAM6 protein levels in tissue microarrays of gastric cancer. We demonstrate an increase in CEACAM6 in early gastric cancers, when compared to matched normal tissue, with an AUC of 0.83 for diagnostic validity. Finally, we show that a fluorescently conjugated CEACAM6 antibody binds avidly to freshly resected gastric cancer xenograft samples and can be detected by endoscopy in real time. Together, these results suggest that CEACAM6 upregulation is a cell surface response to H. pylori CagA, and is retained in early gastric cancers. They highlight a novel link between CEACAM6 expression and CagA in gastric cancer, and suggest CEACAM6 to be a promising biomarker to aid with the fluorescent endoscopic diagnosis of early neoplastic lesions in the stomach

CO Multi-line Imaging of Nearby Galaxies (COMING) IV. Overview of the Project

Observations of the molecular gas in galaxies are vital to understanding the evolution and star-forming histories of galaxies. However, galaxies with molecular gas maps of their whole discs having sufficient resolution to distinguish galactic structures are severely lacking. Millimeter wavelength studies at a high angular resolution across multiple lines and transitions are particularly needed, severely limiting our ability to infer the universal properties of molecular gas in galaxies. Hence, we conducted a legacy project with the 45 m telescope of the Nobeyama Radio Observatory, called the CO Multi-line Imaging of Nearby Galaxies (COMING), which simultaneously observed 147 galaxies with high far-infrared flux in $^{12}$CO, $^{13}$CO, and C$^{18}$O $J=1-0$ lines. The total molecular gas mass was derived using the standard CO-to-H$_2$ conversion factor and found to be positively correlated with the total stellar mass derived from the WISE $3.4 \mu$m band data. The fraction of the total molecular gas mass to the total stellar mass in galaxies does not depend on their Hubble types nor the existence of a galactic bar, although when galaxies in individual morphological types are investigated separately, the fraction seems to decrease with the total stellar mass in early-type galaxies and vice versa in late-type galaxies. No differences in the distribution of the total molecular gas mass, stellar mass, and the total molecular gas to stellar mass ratio was observed between barred and non-barred galaxies, which is likely the result of our sample selection criteria, in that we prioritized observing FIR bright (and thus molecular gas-rich) galaxies.Comment: Accepted for publication in PASJ; 47 pages, 5 tables, 29 figures. On-line supplementary images are available at this URL (https://astro3.sci.hokudai.ac.jp/~radio/coming/publications/). CO data is available at the Japanese Virtual Observatory (JVO) website (https://jvo.nao.ac.jp/portal/nobeyama/coming.do) and the project website (https://astro3.sci.hokudai.ac.jp/~radio/coming/data/

The Constrained Maximal Expression Level Owing to Haploidy Shapes Gene Content on the Mammalian X Chromosome.

X chromosomes are unusual in many regards, not least of which is their nonrandom gene content. The causes of this bias are commonly discussed in the context of sexual antagonism and the avoidance of activity in the male germline. Here, we examine the notion that, at least in some taxa, functionally biased gene content may more profoundly be shaped by limits imposed on gene expression owing to haploid expression of the X chromosome. Notably, if the X, as in primates, is transcribed at rates comparable to the ancestral rate (per promoter) prior to the X chromosome formation, then the X is not a tolerable environment for genes with very high maximal net levels of expression, owing to transcriptional traffic jams. We test this hypothesis using The Encyclopedia of DNA Elements (ENCODE) and data from the Functional Annotation of the Mammalian Genome (FANTOM5) project. As predicted, the maximal expression of human X-linked genes is much lower than that of genes on autosomes: on average, maximal expression is three times lower on the X chromosome than on autosomes. Similarly, autosome-to-X retroposition events are associated with lower maximal expression of retrogenes on the X than seen for X-to-autosome retrogenes on autosomes. Also as expected, X-linked genes have a lesser degree of increase in gene expression than autosomal ones (compared to the human/Chimpanzee common ancestor) if highly expressed, but not if lowly expressed. The traffic jam model also explains the known lower breadth of expression for genes on the X (and the Z of birds), as genes with broad expression are, on average, those with high maximal expression. As then further predicted, highly expressed tissue-specific genes are also rare on the X and broadly expressed genes on the X tend to be lowly expressed, both indicating that the trend is shaped by the maximal expression level not the breadth of expression per se. Importantly, a limit to the maximal expression level explains biased tissue of expression profiles of X-linked genes. Tissues whose tissue-specific genes are very highly expressed (e.g., secretory tissues, tissues abundant in structural proteins) are also tissues in which gene expression is relatively rare on the X chromosome. These trends cannot be fully accounted for in terms of alternative models of biased expression. In conclusion, the notion that it is hard for genes on the Therian X to be highly expressed, owing to transcriptional traffic jams, provides a simple yet robustly supported rationale of many peculiar features of X's gene content, gene expression, and evolution

Corrosion-resistant materials for liquid LiPb fusion blanket in elevated temperature operation

The corrosion tests of CVD-SiC, FeCrAl alloy (APMT, Fe-22Cr-5Al) and ODS FeCrAlZr alloy (NF12, Fe-11.6Cr-6.2Al) were performed in liquid LiPb up to 1173 K for 250 h. High-purity LiPb was synthesized by melting and mixing of Pb and Li granules at 623 K under vacuum condition. CVD-SiC revealed corrosion resistance, though SiC chemically reacted with impurities dissolved in liquid LiPb and formed complex oxides. The α-Al2O3 layer which was formed on the surfaces of the FeCrAl alloys by the pre-oxidation treatment chemically reacted with liquid LiPb at 1023 K and 1173 K, and the layer chemically transformed into γ-LiAlO2