Hung-Jung Wang

Cholesterol Depletion Reduces Helicobacter pylori CagA Translocation and CagA-Induced Responses in AGS Cells

ABSTRACT Infection with Helicobacter pylori cagA-positive strains is associated with gastritis, ulcerations, and gastric cancer. CagA is translocated into infected epithelial cells by a type IV secretion system and can be tyrosine phosphorylated, inducing signal transduction and motogenic responses in epithelial cells. Cellular cholesterol, a vital component of the membrane, contributes to membrane dynamics and functions and is important in VacA intoxication and phagocyte evasion during H. pylori infection. In this investigation, we showed that cholesterol extraction by methyl-β-cyclodextrin reduced the level of CagA translocation and phosphorylation. Confocal microscope visualization revealed that a significant portion of translocated CagA was colocalized with the raft marker GM1 and c-Src during infection. Moreover, GM1 was rapidly recruited into sites of bacterial attachment by live-cell imaging analysis. CagA and VacA were cofractionated with detergent-resistant membranes (DRMs), suggesting that the distribution of CagA and VacA is associated with rafts in infected cells. Upon cholesterol depletion, the distribution shifted to non-DRMs. Accordingly, the CagA-induced hummingbird phenotype and interleukin-8 induction were blocked by cholesterol depletion. Raft-disrupting agents did not influence bacterial adherence but did significantly reduce internalization activity in AGS cells. Together, these results suggest that delivery of CagA into epithelial cells by the bacterial type IV secretion system is mediated in a cholesterol-dependent manner.

Vacuolating Toxin Production in Clinical Isolates of Helicobacter pylori with Different vacA Genotypes

A vacuolating cytotoxin encoded by vacA in Helicobacter pylori is known as a potential virulent determinant. The relationship between different vacA alleles, vacuolating ability, and H. pylori-related diseases was investigated. Genetic analysis of 119 isolates from Taiwanese patients revealed that 104 strains were s1a/m2, 13 strains were characterized as the s1a/m1T type, which was more homologous to the s1a/m1 strains, and 2 were characterized as the s1a/m1Tm2 chimeric type. Production of high-grade cytotoxin among 11 strains with s1a/m1T was higher (72.7%) than among 66 strains with s1a/m2 (21.2%) (P < .01). Peptic ulcer occurred in 76.9% of 13 patients with s1a/m1T strains compared with 46.2% of 104 patients with s1a/m2 strains (P < .05). These results suggest that s1a/m1T strains are associated with increased cytotoxic activity and higher ulcer prevalence than are s1a/m2 strains.

Helicobacter pylori cholesteryl glucosides interfere with host membrane phase and affect type IV secretion system function during infection in AGS cells

Helicobacter pylori infection is an aetiological cause of gastric disorders worldwide. H. pylori has been shown to assimilate and convert host cholesterol into cholesteryl glucosides (CGs) by cholesterol‐α‐glucosyltransferase encoded by capJ. Here, we show that CapJ‐deficient (ΔcapJ) H. pylori resulted in greatly reduced type IV secretion system (TFSS)‐associated activities, including the hummingbird phenotype of AGS cells, IL‐8 production, CagA translocation/phosphorylation and CagA‐mediated signalling events. Complementation of the ΔcapJ mutation with wild type cagJ or by adding CGs‐containing lysates or exogenous fluorophore‐tagged CGs reversed the mutant phenotypes. We also show that the wild‐type but not ΔcapJ H. pylori recruited raft‐associated components to sites of bacterial attachment. Fluorescence recovery after photobleaching (FRAP) analysis of AGS cells treated with fluorescence‐tagged cholesterol/CGs revealed that there was a higher proportion of CGs associated with immobile fractions. CGs‐associated membranes were also more resistant to a cold detergent extraction. Thus, we propose that CGs synthesized by H. pylori around host‐pathogen contact sites partition in detergent‐resistant membranes (DRMs), alters lateral‐phase segregation in membrane and reorganizes membrane architecture. These processes together promote the formation of a functional TFSS and H. pylori infection.

Structure-based inhibitor discovery of Helicobacter pylori dehydroquinate synthase.

Dehydroquinate synthase (DHQS) is a nicotinamide adenine dinucleotide (NAD)-dependent enzyme that converts 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP) into 3-dehydroquinate (DHQ). Since it catalyzes the second key step in the shikimate pathway, which is crucial for the aromatic amino acid metabolism in bacteria, fungi, and plants, but not in mammals, DHQS is a potential target for new antimicrobial agents, anti-parasitic agents and herbicides. The crystal structure of Helicobacter pylori DHQS (HpDHQS) complexed with NAD has been determined at 2.4-A resolution and was found to possess an N-terminal Rossmann-fold domain and a C-terminal alpha-helical domain. Structural comparison reveals that the binary complex adopts an open-state conformation and shares conserved residues in the binding pocket. Virtual docking of compounds into the active site of the HpDHQS structure using the GOLD docking program led to the identification of several inhibitors. The most active compound had an IC(50) value of 61 microM, which may serve as a lead for potent inhibitors.

Cholesterol glucosylation by Helicobacter pylori delays internalization and arrests phagosome maturation in macrophages.

BACKGROUND/PURPOSE Helicobacter pylori colonizes the human stomach and contributes to chronic inflammation of the gastric mucosa. H. pylori persistence occurs because of insufficient eradication by phagocytic cells. A key factor of H. pylori, cholesterol-α-glucosyltransferase encoded by capJ that extracts host cholesterol and converts it to cholesteryl glucosides, is important to evade host immunity. Here, we examined whether phagocytic trafficking in macrophages was perturbed by capJ-carrying H. pylori. METHODS J774A.1 cells were infected with H. pylori at a multiplicity of infection of 50. Live-cell imaging and confocal microscopic analysis were applied to monitor the phagocytic trafficking events. The viability of H. pylori inside macrophages was determined by using gentamicin colony-forming unit assay. The phagocytic routes were characterized by using trafficking-intervention compounds. RESULTS Wild type (WT) H. pylori exhibited more delayed entry into macrophages and also arrested phagosome maturation more than did capJ knockout mutant. Pretreatment of genistein and LY294002 prior to H. pylori infection reduced the internalization of WT but not capJ-knockout H. pylori in macrophages. CONCLUSION Cholesterol glucosylation by H. pylori interferes with phagosome trafficking via a lipid-raft and PI3K-dependent manner, which retards engulfment of bacteria for prolonged intracellular survival of H. pylori.

Helicobacter pylori cholesterol glucosylation modulates autophagy for increasing intracellular survival in macrophages

Cholesterol‐α‐glucosyltransferase (CGT) encoded by the type 1 capsular polysaccharide biosynthesis protein J (capJ) gene of Helicobacter pylori converts cellular cholesterol into cholesteryl glucosides. H. pylori infection induces autophagy that may increase bacterial survival in epithelial cells. However, the role of H. pylori CGT that exploits lipid rafts in interfering with autophagy for bacterial survival in macrophages has not been investigated. Here, we show that wild‐type H. pylori carrying CGT modulates cholesterol to trigger autophagy and restrain autophagosome fusion with lysosomes, permitting a significantly higher bacterial burden in macrophages than that in a capJ‐knockout (∆CapJ) mutant. Knockdown of autophagy‐related protein 12 impairs autophagosome maturation and decreases the survival of internalised H. pylori in macrophages. These results demonstrate that CGT plays a crucial role in the manipulation of the autophagy process to impair macrophage clearance of H. pylori.

Abstract 3359: JMJD5 regulates PKM2 nuclear translocation and reprograms HIF-1α-mediated glucose metabolism

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA JMJD5, a JmjC-domain containing dioxygenase, is important for embryonic development and cancer growth. Here, we show that JMJD5 is up-regulated by hypoxia and is crucial for hypoxia-induced cell proliferation. JMJD5 interacts directly with PKM2, pyruvate kinase M2, to modulate metabolic flux in cancer cells. The JMJD5-PKM2 interaction resides at the intersubunit interface region of PKM2, which hinders PKM2 tetramerization and blocks pyruvate kinase activity. This interaction also influences translocation of PKM2 into the nucleus and promotes HIF-1α-mediated transactivation. JMJD5 knockdown inhibits the transcription of the PKM2-HIF-1α target genes involved in glucose metabolism, resulting in a reduction of glucose uptake and lactate secretion in cancer cells. JMJD5, along with PKM2 and HIF-1α are all recruited to the HRE (hypoxia response element) site in the LDHA and PKM2 loci, and mediates the recruitment of the latter two proteins. Our data uncovers a new mechanism whereby PKM2 can be regulated by factor-binding induced homo/hetero-oligomeric restructuring, paving the way to cell metabolic reprogram. Citation Format: Hung-Jung Wang, Ya-Ju Hsieh, Wen-Chi Cheng, Chun-Pu Lin, Yu-Shan Lin, So-Fang Yang, Chung-Ching Chen, Yoshihiro Izumiya, Jau-Song Yu, Hsing-Jien Kung, Wen-Ching Wang. JMJD5 regulates PKM2 nuclear translocation and reprograms HIF-1α-mediated glucose metabolism. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3359. doi:10.1158/1538-7445.AM2014-3359