Glutathione S-transferase omega 2 regulates cell growth and the expression of E-cadherin via post-transcriptional down-regulation of ß-catenin in human esophageal squamous cells.

Glutathione S-transferase omega 2 (GSTO2), which belongs to the superfamily of GST omega class, lacks any appreciable GST activity. Although GSTO2 exhibits thioltransferase and glutathione dehydrogenase activities, its precise expression and physiological functions are still unclear. In the present study, we found that GSTO2 is exclusively expressed in the basal cell layer in Ki67-negative non-proliferative cells in the human esophageal mucosa. GSTO2 overexpression in esophageal squamous cell carcinoma (ESCC) cell lines inhibited cell growth and colony formation, and GSTO2-transfected cells formed smaller tumors in nude mice compared with mock-transfected cells. Interestingly, GSTO2 induction suppressed the expressions of E-cadherin and ß-catenin at the cell-cell contact site. We quantified the phosphorylation levels of key proteins of MAPK signaling pathway and identified phosphorylation of p38. Additionally, HSP27, a downstream molecule of p38, was accelerated in GSTO2-transfected cells, unlike in mock-transfected cells. When GSTO2-transfected cells were treated with a p38 inhibitor, the expression of ß-catenin and the membrane localization of E-cadherin was recovered. We next examined GSTO2 expression in 61 ESCC tissues using quantitative reverse transcription polymerase chain reaction and immunostaining. The results showed that GSTO2 mRNA and protein were significantly reduced in ESCC compared with normal tissues. When human ESCC cell lines were treated with 5-aza-2'-deoxycytidine, a DNA-methyltransferase inhibitor, GSTO2 transcription was induced, suggesting that aberrant hypermethylation is the cause of the down-regulated expression. Our results indicate that GSTO2 expression inhibits the membrane localization of E-cadherin, probably by modulation of the p38 signaling pathway. Down-regulation of GSTO2 by DNA hypermethylation contributes to the growth and progression of ESCC.

Vinexin family (SORBS) proteins play different roles in stiffness-sensing and contractile force generation.

Vinexin, c-Cbl associated protein (CAP) and Arg-binding protein 2 (ArgBP2) constitute an adaptor protein family called the vinexin (SORBS) family that is targeted to focal adhesions (FAs). Although numerous studies have focused on each of the SORBS proteins and partially elucidated their involvement in mechanotransduction, a comparative analysis of their function has not been well addressed. Here, we established mouse embryonic fibroblasts that individually expressed SORBS proteins and analysed their functions in an identical cell context. Both vinexin-α and CAP co-localized with vinculin at FAs and promoted the appearance of vinculin-rich FAs, whereas ArgBP2 co-localized with α-actinin at the proximal end of FAs and punctate structures on actin stress fibers (SFs), and induced paxillin-rich FAs. Furthermore, both vinexin-α and CAP contributed to extracellular matrix stiffness-dependent vinculin behaviors, while ArgBP2 stabilized α-actinin on SFs and enhanced intracellular contractile forces. These results demonstrate the differential roles of SORBS proteins in mechanotransduction.

Disruption of the TWEAK/Fn14 pathway prevents 5-fluorouracil-induced diarrhea in mice.

AIM: To clarify the roles of TWEAK and its receptor Fn14 in 5-fluorouracil (5-FU)-induced diarrhea. METHODS: Diarrhea was induced in wild-type (WT), Fn14 knockout (KO), and IL-13 receptor (IL-13R)α1 KO BALB/c mice using a single injection of 5-FU. Histological analysis, cytokine analysis, and flow cytometry was performed on ileal tissues and cells. Murine colon carcinoma-bearing mice were co-treated with an anti-TWEAK antibody and 5-FU. Embryonic fibroblast response to cytokines was also analyzed. RESULTS: 5-FU induced high Fn14 expression in epithelial cells. The severity of 5-FU-induced diarrhea was lower in Fn14 KO mice compared with WT mice. Administration of anti-TWEAK antibody reduced 5-FU-induced diarrhea without affecting the antitumor effects of 5-FU in vivo. 5-FU-induced expression of IL-13, IL-17A, TNF-α, and IFN-γ in the ileum was Fn14 dependent. The severity of 5-FU-induced diarrhea was lower in IL-13Rα1 KO mice, indicating major role for IL-13 signaling via IL-13Rα1 in pathogenesis. We found that IL-13Rα2, an IL-13 neutralizing/cell protective receptor, was strongly induced by IL-33 in vitro and in vivo. IL-13Rα2 was upregulated in the ileum of 5-FU-treated Fn14 KO mice. Thus, the deletion of Fn14 upregulated IL-13Rα2 expression, which reduced IL-13 expression and activity. CONCLUSION: Disruption of the TWEAK/Fn14 pathway affects several interconnected pathways, including those associated with IL-13, IL-33, and IL-13Rα2, to attenuate 5-FU-induced intestinal side effects.

Fatty acids in a high-fat diet potentially induce gastric parietal-cell damage and metaplasia in mice.

BACKGROUND: Obesity is associated with risk of adenocarcinoma in the proximal stomach. We aimed to identify the links between dietary fat and gastric premalignant lesions. METHODS: C57BL/6 mice were fed high fat diet (HFD), and gastric mucosa was histologically analysed. Morphological changes were also analysed using an electron microscope. Transcriptome analysis of purified parietal cells was performed, and non-parietal gastric corpus epithelial cells were subjected to single-cell gene-expression profiling. Composition of gastric contents of HFD-fed mice was compared with that of the HFD itself. Lipotoxicity of free fatty acids (FFA) was examined in primary culture and organoid culture of mouse gastric epithelial cells in vitro, as well as in vivo, feeding FFA-rich diets. RESULTS: During ~8-20 weeks of HFD feeding, the parietal cells of the stomach displayed mitochondrial damage, and a total of 23% of the mice developed macroscopically distinct metaplastic lesions in the gastric corpus mucosa. Transcriptome analysis of parietal cells indicated that feeding HFD enhanced pathways related to cell death. Histological analysis and gene-expression profiling indicated that the lesions were similar to previously reported precancerous lesions identified as spasmolytic polypeptide-expressing metaplasia. FFAs, including linoleic acid with refluxed bile acids were detected in the stomachs of the HFD-fed mice. In vitro, FFAs impaired mitochondrial function and decreased the viability of parietal cells. In vivo, linoleic acid-rich diet, but not stearic acid-rich diet induced parietal-cell loss and metaplastic changes in mice. CONCLUSIONS: Dietary lipids induce parietal-cell damage and may lead to the development of precancerous metaplasia.

Aberrant DNA hypermethylation reduces the expression of the desmosome-related molecule periplakin in esophageal squamous cell carcinoma.

Periplakin (PPL), a member of the plakin family of proteins that localizes to desmosomes and intermediate filaments, is downregulated in human esophageal squamous cell carcinoma (ESCC). Little is known, however, about the molecular mechanism underlying the regulation of PPL expression and the contribution of PPL loss to the malignant property of the cancer is unclear. We demonstrated that PPL mRNA expression was significantly reduced in ESCC tissues compared with that in normal tissues. Therefore, we hypothesized that CpG hypermethylation is the cause of the downregulation of PPL. Bisulfite-pyrosequencing of 17 cases demonstrated that the frequency of PPL methylation was higher in ESCC tissues than in normal tissues. When human ESCC cell lines were treated with 5-aza-2'-deoxycytidine (5-aza-dC), a DNA-methyltransferase inhibitor, PPL transcription was induced. Human KYSE270 ESCC cells do not stratify under ordinary culture conditions and rarely produce desmosomes; however, the forced expression of PPL promoted cell stratification. PPL induction also promoted adhesion to extracellular matrix but delayed cell migration. The abundance of desmosome-like structures was greatly increased in PPL transfectant as determined by transmission electron microscopy. Very low expression of another desmosome protein EVPL in ESCC, even in PPL transfectant, also supported the significant role of PPL in desmosome formation and cell stratification. Our results first indicate that the downregulation of PPL mediated by DNA hypermethylation, which may play an important role in the loss of ESCC stratification and likely in metastatic phenotype.

Small-molecule-induced clustering of heparan sulfate promotes cell adhesion.

Adhesamine is an organic small molecule that promotes adhesion and growth of cultured human cells by binding selectively to heparan sulfate on the cell surface. The present study combined chemical, physicochemical, and cell biological experiments, using adhesamine and its analogues, to examine the mechanism by which this dumbbell-shaped, non-peptidic molecule induces physiologically relevant cell adhesion. The results suggest that multiple adhesamine molecules cooperatively bind to heparan sulfate and induce its assembly, promoting clustering of heparan sulfate-bound syndecan-4 on the cell surface. A pilot study showed that adhesamine improved the viability and attachment of transplanted cells in mice. Further studies of adhesamine and other small molecules could lead to the design of assembly-inducing molecules for use in cell biology and cell therapy.

Dlg5 interacts with the TGF-ß receptor and promotes its degradation.

Discs large homolog 5 (Dlg5) is a member of the membrane-associated guanylate kinase adaptor family of proteins and is involved in epithelial-to-mesenchymal transition via transforming growth factor-ß (TGF-ß) signaling. However, the mechanism underlying the regulation of TGF-ß signaling is unclear. We show here that Dlg5 interacts and colocalizes with both TGF-ß type I (TßRI) and type II (TßRII) receptors at the plasma membrane. TßRI activation is not required for this interaction. Furthermore, the overexpression of Dlg5 enhances the degradation of TßRI. Proteasome inhibitors inhibited this enhanced degradation. These results suggest that Dlg5 interacts with TßRs and promotes their degradation.

Role of Dlg5/lp-dlg, a membrane-associated guanylate kinase family protein, in epithelial-mesenchymal transition in LLc-PK1 renal epithelial cells.

Discs large homolog 5 (Dlg5) is a member of the membrane-associated guanylate kinase adaptor family of proteins, some of which are involved in the regulation of epithelial-to-mesenchymal transition (EMT). Dlg5 has been described as a susceptibility gene for Crohn's disease; however, the physiological function of Dlg5 is unknown. We show here that transforming growth factor-ß (TGF-ß)-induced EMT suppresses Dlg5 expression in LLc-PK1 cells. Depletion of Dlg5 expression by knockdown promoted the expression of the mesenchymal marker proteins, fibronectin and α-smooth muscle actin, and suppressed the expression of E-cadherin. In addition, activation of JNK and p38, which are stimulated by TGF-ß, was enhanced by Dlg5 depletion. Furthermore, inhibition of the TGF-ß receptor suppressed the effects of Dlg5 depletion. These observations suggest that Dlg5 is involved in the regulation of TGF-ßreceptor-dependent signals and EMT.

Protein kinase A-dependent increase in WAVE2 expression induced by the focal adhesion protein vinexin.

The focal adhesion protein vinexin is a member of a family of adaptor proteins that are thought to participate in the regulation of cell adhesion, cytoskeletal reorganization, and growth factor signaling. Here, we show that vinexin beta increases the amount of and reduces the mobility on SDS-PAGE of Wiskott-Aldrich syndrome protein family verprolin-homologous protein (WAVE) 2 protein, which is a key factor modulating actin polymerization in migrating cells. This mobility retardation disappeared after in vitro phosphatase treatment. Co-immunoprecipitation assays revealed the interaction of vinexin beta with WAVE2 as well as WAVE1 and N-WASP. Vinexin beta interacts with the proline-rich region of WAVE2 through the first and second SH3 domains of vinexin beta. Mutations disrupting the interaction impaired the ability of vinexin beta to increase the amount of WAVE2 protein. Treatments with proteasome inhibitors increased the amount of WAVE2, but did not have an additive effect with vinexin beta. Inhibition of protein kinase A (PKA) activity suppressed the vinexin-induced increase in WAVE2 protein, while activation of PKA increased WAVE2 expression without vinexin beta. These results suggest that vinexin beta regulates the proteasome-dependent degradation of WAVE2 in a PKA-dependent manner.