Helicobacter pylori infection combined with DENA revealed altered expression of p53 and 14-3-3 isoforms in Gulo−/− mice

AbstractUnlike most other mammals, human bodies do not have the ability to synthesize vitamin C inside of their own bodies. Therefore, humans must obtain vitamin C through daily diet. Gulo−/− mice strain is known with deficiency, in which vitamin C intake can be controlled by diet like human, and would be valuable for investigating the molecular mechanism of various diseases. In the present study, we established Gulo−/− mice model and investigated the differentially expressed proteins in stomach tissue of Gulo−/− mice after Helicobacter pylori-infected, and followed by DENA, using immunohistochemistry and proteomic approach. The results of immunohistochemistry analysis of stomach tissue showed that the tumor suppressor, p53 protein, expression was significantly decreased (p<0.05) but not messenger RNA (mRNA) transcriptional level, and 14-3-3ε, 14-3-3δ, Ki-67 and cleaved caspase 3 expressions were significantly increased (p<0.05) by H. Pylori infection, and followed by DENA treatment in Gulo−/− mice. Moreover, knockdown of 14-3-3 isoforms (14-3-3ε, 14-3-3σ, 14-3-3ζ and 14-3-3η) were significantly increased sub-G1 phase (characteristics of apoptosis) in AGS cells and, phenotypic changes like cell shrinkage, density and cleaved nuclei were also observed. Proteome analyses showed that 14-3-3σ, 14-3-3η, and tropomyosin alpha-1 chain were down-regulated, and Hspd1 protein and HSC70 were up-regulated after H. Pylori-infection, and followed by DENA. The combined results of immunohistochemistry and proteomic analysis suggest that H. pylori altered the p53 and 14-3-3 isoforms expression and DENA further enhanced the H. pylori effect, which might be involved in carcinogenesis and metastasis of gastric cancer on Gulo−/− mice

LONP1 and ClpP cooperatively regulate mitochondrial proteostasis for cancer cell survival

Mitochondrial proteases are key components in mitochondrial stress responses that maintain proteostasis and mitochondrial integrity in harsh environmental conditions, which leads to the acquisition of aggressive phenotypes, including chemoresistance and metastasis. However, the molecular mechanisms and exact role of mitochondrial proteases in cancer remain largely unexplored. Here, we identified functional crosstalk between LONP1 and ClpP, which are two mitochondrial matrix proteases that cooperate to attenuate proteotoxic stress and protect mitochondrial functions for cancer cell survival. LONP1 and ClpP genes closely localized on chromosome 19 and were co-expressed at high levels in most human cancers. Depletion of both genes synergistically attenuated cancer cell growth and induced cell death due to impaired mitochondrial functions and increased oxidative stress. Using mitochondrial matrix proteomic analysis with an engineered peroxidase (APEX)-mediated proximity biotinylation method, we identified the specific target substrates of these proteases, which were crucial components of mitochondrial functions, including oxidative phosphorylation, the TCA cycle, and amino acid and lipid metabolism. Furthermore, we found that LONP1 and ClpP shared many substrates, including serine hydroxymethyltransferase 2 (SHMT2). Inhibition of both LONP1 and ClpP additively increased the amount of unfolded SHMT2 protein and enhanced sensitivity to SHMT2 inhibitor, resulting in significantly reduced cell growth and increased cell death under metabolic stress. Additionally, prostate cancer patients with higher LONP1 and ClpP expression exhibited poorer survival. These results suggest that interventions targeting the mitochondrial proteostasis network via LONP1 and ClpP could be potential therapeutic strategies for cancer

ADSORPTION OF CARBON DIOXIDE ON THE CHEMICALLY MODIFIED ADSORBENTS

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