Localization of the Death Effector Domain of Fas-Associated Death Domain Protein into the Membrane of Escherichia coli Induces Reactive Oxygen Species-Involved Cell Death

Signaling Transduction Network Elucidation of ACE 2 Regulating Apostichopus japonicus Autolysis by Using Integrative TMT Proteomics and Transcriptomics

This study aims to reveal the transduction signaling network that triggers sea cucumber (Apostichopus japonicus) autolysis. The tandem mass tag (TMT) proteomics and transcriptomic techniques were used to analyze expression differences between inhibited and activated sea cucumber autolysis. Flow cytometry was used to identify apoptosis. Western blotting and RT-PCR verified the signaling pathway. The results showed that the angiotensin-converting enzyme 2 (ACE 2) activator (diminazene, DIZE) maintained the health of A. japonicus. The ACE 2 inhibitor (captopril, Capt) accelerated the autolysis. Based on the multiomics analysis, the ACE 2 activator activated the downstream NF-κB pathway to prevent the sea cucumber apoptosis. The Capt activated apoptosis initiation. Apoptosis occurred through the regulation of TNF and PI3K-Akt signaling pathways, which downregulate NF-κB. Akt was identified as an intermediate signaling protein downstream of ACE 2 that regulates autolysis in A. japonicus. Compared to A. japonicus in the ultraviolet-irradiated and Capt groups, the Akt inhibitor (perifosine, KRX) significantly reduced the expression of the PI3K-Akt and NF-κB pathways, thereby inhibiting the autolysis process. Additionally, DIZE attenuated ROS levels, thereby inhibiting the autolysis of A. japonicus. This study provides better insight into the autolysis mechanism of A. japonicus.

Engineering microbial cell viability for enhancing chemical production by second codon engineering

Microbial cell factories offer a promising strategy for the sustainable production of industrial chemicals from renewable biomass feedstock. However, their performance is often limited by poor microbial cell viability (MCV). Here, MCV was engineered to enhance chemical production by optimizing the regulation of lifespan-specific genes to reduce the accumulation of reactive oxygen species (ROS). In Escherichia coli, MCV was improved by reducing ROS accumulation using second codon engineering to regulate hypoxia-inducible transcription factor (arcA), resulting in lysine production up to 213 g L^-1 with its productivity 5.90 g L^-1·h^-1. In Saccharomyces cerevisiae, MCV was increased by decreasing ROS accumulation using second codon engineering to fine-tune ceramide synthase (lag1), leading to glucaric acid production up to 9.50 g L^-1 with its productivity 0.057 g L^-1·h^-1. These results demonstrate that engineering MCV is a potential strategy to boost the performance of microbial cell factories in industrial processes.

Cholecystokinin octapeptide antagonizes apoptosis in human retinal pigment epithelial cells

Although cholecystokinin octapeptide-8 is important for neurological function, its neuroprotective properties remain unclear. We speculated that cholecystokinin octapeptide-8 can protect human retinal pigment epithelial cells against oxidative injury. In this study, retinal pigment epithelial cells were treated with peroxynitrite to induce oxidative stress. Peroxynitrite triggered apoptosis in these cells, and increased the expression of Fas-associated death domain, Bax, caspa-se-8 and Bcl-2. These changes were suppressed by treatment with cholecystokinin octapeptide-8. These results suggest that cholecystokinin octapeptide-8 can protect human retinal pigment epithelial cells against apoptosis induced by peroxynitrite.

A novel protein Jpk induces bacterial cell death through reactive oxygen species

Jpk, a trans-acting regulatory factor associating with the position-specific regulatory element of Hoxa-7, has been reported to induce cell death in both prokaryotic and eukaryotic cells upon overexpression. The N- and C-terminal deleted variants of Jpk were constructed and then the toxicity of each construct was analyzed by checking the viability of the cells and the concomitant morphological changes through electron microscopy following the expression. The N-terminus of Jpk harboring transmembrane domain seemed to be more toxic to bacterial cell than C-terminus and the morphology of bacterial cells expressing N-terminal Jpk was similar to that induced by full length Jpk. The toxicity caused by Jpk protein in bacterial cell was through the production of ROS, which was decreased by an antioxidant (DTT) in a concentration dependent manner. The finding described in this study provides valuable clues on the relationship between Jpk toxicity and ROS generation.

Overexpression of reactive cysteine-containing 2-nitrobenzoate nitroreductase (NbaA) and its mutants alters the sensitivity of Escherichia coli to reactive oxygen species by reprogramming a regulatory network of disulfide-bonded proteins

The effects of redox-sensitive proteins on Escherichia coli were investigated by overexpressing Pseudomonas 2-nitrobenzoate nitroreductase (NbaA) and its mutants. Overexpression of wild-type and mutant NbaA proteins significantly altered the sensitivity of E. coli to antibiotics and reactive oxygen species regardless of the enzyme activity for reduction of 2-nitrobenzoic acid. The overexpressed proteins rendered cells 100-10000-fold more sensitive to superoxide anion (O2(•-))-generating paraquat and 10-100-fold more resistant to H2O2. A significant increase in intracellular levels of O2(•-), but not H2O2, was observed during expression of wild-type and truncated (Δ65-74, Δ193-216, and Δ65-74Δ193-216) NbaA. From two-dimensional nonreducing/reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis and mass spectrometry analyses, 29 abundant proteins in the cytoplasm were identified to form interchain disulfide bonds, when cells were exposed to polymyxin B. Of them, down-regulation and modifications of SodB, KatE, and KatG were strongly associated with elevated cellular O2(•-) levels. Western blotting showed up-regulation of cell death signal sensor, CpxA, and down-regulation of cytoplasmic superoxide dismutase, SodB, with ∼2-fold up-regulation of heterodimeric integration host factor, Ihf. Activity gel assays revealed significant reduction of glyceraldehyde-3-phosphate dehydrogenase with constant levels of 6-phosphogluconate dehydrogenase. These changes would support a high level of NADPH to reduce H2O2-induced disulfide bonds by forced expression of thioredoxin A via thioredoxin reductase. Thus, overexpression of wild-type and truncated NbaA partially compensates for the lack of KatE and KatG to degrade H2O2, thereby enhancing disulfide bond formation in the cytoplasm, and modifies a regulatory network of disulfide-bonded proteins to increase intracellular O2(•-) levels.