Production and characterization of soluble human TNFRI-Fc and human HO-1(HMOX1) transgenic pigs by using the F2A peptide

Generation of transgenic pigs for xenotransplantation is one of the most promising technologies for resolving organ shortages. Human heme oxygenase-1 (hHO-1/HMOX1) can protect transplanted organs by its strong anti-oxidative, anti-apoptotic, and anti-inflammatory effects. Soluble human TNFRI-Fc (shTNFRI-Fc) can inhibit the binding of human TNF-α (hTNF-α) to TNF receptors on porcine cells, and thereby, prevent hTNF-α-mediated inflammation and apoptosis. Herein, we successfully generated shTNFRI-Fc-F2A-HA-hHO-1 transgenic (TG) pigs expressing both shTNFRI-Fc and hemagglutinin-tagged-human heme oxygenase-1 (HA-hHO-1) by using an F2A self-cleaving peptide. shTNFRI-Fc and HA-hHO-1 transgenes containing the F2A peptide were constructed under the control of the CAG promoter. Transgene insertion and copy number in the genome of transgenic pigs was confirmed by polymerase chain reaction (PCR) and Southern blot analysis. Expressions of shTNFRI-Fc and HA-hHO-1 in TG pigs were confirmed using PCR, RT-PCR, western blot, ELISA, and immunohistochemistry. shTNFRI-Fc and HA-hHO-1 were expressed in various organs, including the heart, lung, and spleen. ELISA assays detected shTNFRI-Fc in the sera of TG pigs. For functional analysis, fibroblasts isolated from a shTNFRI-Fc-F2A-HA-hHO-1 TG pig (i.e., #14; 1 × 10⁵ cells) were cultured with hTNF-α (20 ng/mL) and cycloheximide (10 μg/mL). The viability of shTNFRI-Fc-F2A-HA-hHO-1 TG pig fibroblasts was significantly higher than that of the wild type (wild type vs. shTNFRI-Fc-F2A-HA-hHO-1 TG at 24 h, 31.6 ± 3.2 vs. 60.4 ± 8.3 %, respectively; p < 0.05). Caspase-3/-7 activity of the shTNFRI-Fc-F2A-HA-hHO-1 TG pig fibroblasts was lower than that of the wild type pig fibroblasts (wild type vs. shTNFRI-Fc-F2A-HA-hHO-1 TG at 12 h, 812,452 ± 113,078 RLU vs. 88,240 ± 10,438 RLU, respectively; p < 0.05). These results show that shTNFRI-Fc and HA-hHO-1 TG pigs generated by the F2A self-cleaving peptide express both shTNFRI-Fc and HA-hHO-1 molecules, which provides protection against oxidative and inflammatory injury. Utilization of the F2A self-cleaving peptide is a promising tool for generating multiple TG pigs for xenotransplantation.     

Positive regulation of apoptosis signal-regulating kinase 1 by hD53L1

Apoptosis signal-regulating kinase 1 (ASK1) is a mitogen-activated protein kinase kinase kinase family member that plays a central role in cytokine- and stress-induced apoptosis by activating c-Jun N-terminal kinase and p38 signaling cascades. ASK1-induced apoptotic activity is up-regulated by two cellular factors, Daxx and TRAF2, through direct protein-protein interactions. Daxx and TRAF2 are death receptor-associated proteins in Fas and tumor necrosis factor-alpha pathways, respectively. Recent studies suggest that calcium signaling may regulate ASK1 pathway. Here we report that human D53L1, a member of the tumor protein D52 family involved in cell proliferation and calcium signaling, up-regulates the ASK1-induced apoptosis. The human D53L1 physically interacts with the C-terminal regulatory domain of ASK1 and promotes ASK1-induced apoptotic activity by activating caspase signaling in mammalian cells. In luciferase reporter assays, hD53L1 activates c-Jun N-terminal kinase-mediated transactivation in the presence of ASK1. Expression of hD53L1 enhances autophosphorylation and kinase activity of ASK1 but has no effect on ASK1 oligomerization that is necessary for kinase activity and on binding of ASK1 to MKK6, a downstream factor of ASK1. Taken together, these results suggest that activation of ASK1 by hD53L1 may provide a novel mechanism for ASK1 regulation.     

Myasthenia gravis following human papillomavirus vaccination: a case report

DNA methyltransferase 1 (EC 2.1.1.37), encoded by DNMT1 gene, is one of key enzymes in maintaining DNA methylation patterns of the human genome. It plays a crucial role in embryonic development, imprinting and genome stability, cell differentiation. The dysfunction of this group of enzymes can lead to a variety of human genetic disorders. Until now, mutations in DNMT1 have been found to be associated with two distinct phenotypes. Mutations in exon 20 of this gene leads to hereditary sensory and autonomic neuropathy type IE, and mutations in exon 21 cause autosomal dominant cerebellar ataxia, deafness and narcolepsy. Here we report a novel DNMT1 mutation in a sporadic case of a Chinese patient with cerebellar ataxia, multiple motor and sensory neuropathy, hearing loss and psychiatric manifestations. Furthermore, we elucidated its pathogenic effect through molecular genetics studies and revealed that this defective DNMT1 function is responsible for the phenotypes in this individual. Our findings expand the spectrum of DNMT1-related disorders and provide a good example of precision medicine through the combination of exome sequencing and clinical testing.     

Vibrio vulnificus-induced death of Jurkat T-cells requires activation of p38 mitogen-activated protein kinase by NADPH oxidase-derived reactive oxygen species

Vibrio vulnificus, a pathogenic bacterium causing primary septicemia, exhibited cytotoxicity towards Jurkat cells of T-lymphocytes through intracellular reactive oxygen species (ROS) production. Pretreatment of Jurkat T-cells with diphenyleneiodonium chloride (DPI) abolished V. vulnificus-induced ROS generation and bacterial ability to cause cell death. Jurkat T-cells expressing dominant-negative protein of Rac subunit of NADPH oxidase (NOX) did not show increased ROS production and cell death by V. vulnificus. Vibrio vulnificus also triggered phosphorylation of mitogen-activated protein kinases (MAPKs) including p38 and ERK1/2 in Jurkat T-cells. Experiments using inhibitors or small interfering RNAs for each MAPK showed that both MAPKs are involved in V. vulnificus-induced cell death. DPI only blocked the phosphorylation of p38 MAPK in Jurkat T-cells exposed by V. vulnificus. This study demonstrates that V. vulnificus induces death of Jurkat T-cells via ROS-dependent activation of p38 MAPK, and that NOX plays a major role in ROS generation in V. vulnificus-exposed cells.     

Acetylation of malate dehydrogenase 1 promotes adipogenic differentiation via activating its enzymatic activity

Acetylation is one of the most crucial post-translational modifications that affect protein function. Protein lysine acetylation is catalyzed by acetyltransferases, and acetyl-CoA functions as the source of the acetyl group. Additionally, acetyl-CoA plays critical roles in maintaining the balance between carbohydrate metabolism and fatty acid synthesis. Here, we sought to determine whether lysine acetylation is an important process for adipocyte differentiation. Based on an analysis of the acetylome during adipogenesis, various proteins displaying significant quantitative changes were identified by LC-MS/MS. Of these identified proteins, we focused on malate dehydrogenase 1 (MDH1). The acetylation level of MDH1 was increased up to 6-fold at the late stage of adipogenesis. Moreover, overexpression of MDH1 in 3T3-L1 preadipocytes induced a significant increase in the number of cells undergoing adipogenesis. The introduction of mutations to putative lysine acetylation sites showed a significant loss of the ability of cells to undergo adipogenic differentiation. Furthermore, the acetylation of MDH1 dramatically enhanced its enzymatic activity and subsequently increased the intracellular levels of NADPH. These results clearly suggest that adipogenic differentiation may be regulated by the acetylation of MDH1 and that the acetylation of MDH1 is one of the cross-talk mechanisms between adipogenesis and the intracellular energy level.     

Multiple effects of SERCA2b mutations associated with Darier's disease

Darier's disease (DD) is an autosomal dominant disorder caused by mutations in the ATP2A2 gene, encoding sarco/endoplasmic reticulum Ca2+-ATPase pump type 2b isoform (SERCA2b). Although >100 mutations in the ATP2A2 gene were identified, no apparent relation between genotype/phenotype emerged. In this work, we analyzed 12 DD-associated mutations from all of the regions of SERCA2b to study the underlying pathologic mechanism of DD and to elucidate the role of dimerization in SERCA2b activity. Most mutations markedly affected protein expression, partially because of enhanced proteasome-mediated degradation. All of the mutants showed lower activity than the wild type pump. Notably, several mutants that cause relatively severe phenotype of DD inhibited the activity of the endogenous and the co-expressed wild type SERCA2b. Importantly, these effects were not attributed to changes in passive Ca2+ leak, inositol 1,4,5-trisphosphate receptor activity, or sensitivity to inositol 1,4,5-trisphosphate. Rather, co-immunoprecipitation experiments showed that SERCA2b monomers interact to influence the activity of each other. These findings reveal multiple molecular mechanisms to account for the plethora of pathologic states observed in DD and provide the first evidence for the importance of SERCA2b dimerization in pump function in vivo.     

Laminar shear stress up-regulates peroxiredoxins (PRX) in endothelial cells: PRX 1 as a mechanosensitive antioxidant

Shear stress plays a significant role in endothelial cell biology and atherosclerosis development. Previous work by our group has shown that fluid flow stimulates important functional changes in cells through protein expression regulation. Peroxiredoxins (PRX) are a family of antioxidant enzymes but have yet to be investigated in response to shear stress. Studies have shown that oscillatory shear stress (OS) increases reactive oxygen species (ROS) levels in endothelial cells, whereas laminar shear stress (LS) blocks this response. We hypothesized that PRX are responsible for the anti-oxidative effect of LS. To test this hypothesis, bovine aortic endothelial cells (BAEC) were subjected to LS (15 dyn/cm(2)), OS (+/-5 dyn/cm(2), 1 Hz), or static conditions for 24 h. Using Western blot and immunofluorescence staining, all six isoforms of PRX were identified in BAEC. When compared with OS and static, exposure to chronic LS up-regulated PRX 1 levels intracellularly. LS also increased expression of PRX 5 relative to static controls, but not OS. PRX exhibited broad subcellular localization, with distribution in the cytoplasm, Golgi, mitochondria, and intermediate filaments. In addition, PRX 1 knock down, using specific small interference RNA, attenuated LS-dependent reactive oxygen species reduction in BAEC. However, PRX 5 depletion did not. Together, these results suggest that PRX 1 is a novel mechanosensitive antioxidant, playing an important role in shear-dependent regulation of endothelial biology and atherosclerosis.     

Protein disulfide isomerase is cleaved by caspase-3 and -7 during apoptosis

Apoptotic signals are typically accompanied by activation of aspartate-specific cysteine proteases called caspases, and caspase-3 and -7 play crucial roles in the execution of apoptosis. Previously, using the proteomic approach, protein disulfide isomerase (PDI) was found to be a candidate substrate of caspase-7. This abundant 55 kDa protein introduces disulfide bonds into proteins (via its oxidase activity) and catalyzes the rearrangement of incorrect disulfide bonds (via its isomerase activity). PDI is abundant in the ER but is also found in non-ER locations. In this study we demonstrated that PDI is cleaved by caspase-3 and -7 in vitro. In addition, in vivo experiment showed that it is cleaved during etoposide-induced apoptosis in HL-60 cells. Subcellular fractionation showed that PDI was also present in the cytosol. Furthermore, only cytosolic PDI was clearly digested by caspase-3 and -7. It was also confirmed by confocal image analysis that PDI and caspase-7 partially co-localize in both resting and apoptotic MCF-7 cells. Overexpression of cytosolic PDI (ER retention sequence deleted) inhibited cell death after an apoptotic stimulus. These data indicate that cytosolic PDI is a substrate of caspase-3 and -7, and that it has an anti-apoptotic action.