Clostridium septicum produces a single lethal factor, alpha toxin (AT), which is a cytolytic protein with a molecular mass of approximately 48 kDa. The 48 kDa toxin was found to be an inactive protoxin (ATpro) which could be activated via a carboxy-terminal cleavage with trypsin. The cleavage site was located approximately 4 kDa from the carboxy-terminus. Proteolytically activated ATpro had a specific activity of approximately 1.5 x 10(6) haemolytic units mg-1. The trypsin-activated toxin (ATact) was haemolytic, stimulated a prelytic release of potassium ions from erythrocytes which was followed by haemoglobin release, induced channel formation in planar membranes and aggregated into a complex of M(r) > 210,000 on erythrocyte membranes. ATpro did not exhibit these properties. ATact formed pores with a diameter of at least 1.3-1.6 nm. We suggest that pore formation on target cell membranes is responsible for the cytolytic activity of alpha toxin.

The high-mobility group box protein 1 (HMGB1) is increasingly recognized as an important inflammatory mediator. In some cases, the release of HMGB1 is regulated by poly(ADP-ribose) polymerase-1 (PARP-1), but the mechanism is still unclear. In this study, we report that PARP-1 activation contributes to LPS-induced PARylation of HMGB1, but the PARylation of HMGB1 is insufficient to direct its migration from the nucleus to the cytoplasm; PARP-1 regulates the translocation of HMGB1 to the cytoplasm through upregulating the acetylation of HMGB1. In mouse bone marrow–derived macrophages, genetic and pharmacological inhibition of PARP-1 suppressed LPS-induced translocation and release of HMGB1. Increased PARylation was accompanied with the nucleus-to-cytoplasm translocation and release of HMGB1 upon LPS exposure, but PARylated HMGB1 was located at the nucleus, unlike acetylated HMGB1 localized at the cytoplasm in an import assay. PARP inhibitor and PARP-1 depletion decreased the activity ratio of histone acetyltransferases to histone deacetylases that elevated after LPS stimulation and impaired LPS-induced acetylation of HMGB1. In addition, PARylation of HMGB1 facilitates its acetylation in an in vitro enzymatic reaction. Furthermore, reactive oxygen species scavenger (N-acetyl-l-cysteine) and the ERK inhibitor (FR180204) impaired LPS-induced PARP activation and HMGB1 release. Our findings suggest that PARP-1 regulates LPS-induced acetylation of HMGB1 in two ways: PARylating HMGB1 to facilitate the latter acetylation and increasing the activity ratio of histone acetyltransferases to histone deacetylases. These studies revealed a new mechanism of PARP-1 in regulating the inflammatory response to endotoxin.

PRR11 is a potential candidate oncogene that has been implicated in the pathogenesis of lung cancer, however the role of PRR11 in gastric cancer is currently unclear. In the present study, we investigated the role of PRR11 in gastric cancer by evaluating its expression status in samples from a cohort of 216 patients with gastric cancer. PRR11 was found to be overexpressed in 107 (49.5%) patients by immunohistochemistry of tissue microarrays generated using the patient samples. Furthermore, PRR11 overexpression was found to correlate significantly with clinicopathologic features such as tumor invasion, tumor differentiation, and disease stage. Survival analysis of the cohort revealed that PRR11 is an independent prognostic factor for gastric cancer patients. PRR11 was stably silenced in a gastric carcinoma cell line using an shRNA-based approach, and treated cells showed decreased cellular proliferation and colony formation in vitro and cell growth in vivo, companied by decreased expression of CTHRC1 and increased expression of LXN, proteins involved in tumor progression. Evaluation of human gastric cancer samples demonstrated that PRR11 expression was also associated with increased CTHRC1 and decreased LXN expression. These data indicate that PRR11 may be widely activated in human gastric cancer and are consistent with the hypothesis that PRR11 functions as an oncogene in the development and progression of gastric cancer.

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