Host-derived peptide signals regulate Pseudomonas aeruginosa virulence stress via the ParRS and CprRS two-component systems

Pseudomonas aeruginosa, a versatile bacterium, has dual significance because of its beneficial roles in environmental soil processes and its detrimental effects as a nosocomial pathogen that causes clinical infections. Understanding adaptability to environmental stress is essential. This investigation delves into the complex interplay of two-component system (TCS), specifically ParRS and CprRS, as P. aeruginosa interprets host signals and navigates stress challenges. In this study, through phenotypic and proteomic analyses, the nuanced contributions of ParRS and CprRS to the pathogenesis and resilience mechanisms were elucidated. Furthermore, the indispensable roles of the ParS and CprS extracellular sensor domains in orchestrating signal perception remain unknown. Structural revelations imply a remarkable convergence of TCS sensors in interacting with host peptides, suggesting evolutionary strategies for bacterial adaptation. This pioneering work not only established links between cationic antimicrobial peptide (CAMP) resistance-associated TCSs and virulence modulation in nosocomial bacteria, but also transcended conventional boundaries. These implications extend beyond clinical resistance, permeating into the realm of soil revitalization and environmental guardianship. As it unveils P. aeruginosa intricacies, this study assumes a mantle of guiding strategies to mitigate clinical hazards, harness environmental advantages, and propel sustainable solutions forward.

Nucleotide binding as an allosteric regulatory mechanism for Akkermansia muciniphila β-N-acetylhexosaminidase Am2136

β-N-acetylhexosaminidases (EC3.2.1.52), which belong to the glycosyl hydrolase family GH20, are important enzymes for oligosaccharides modification. Numerous microbial β-N-acetylhexosaminidases have been investigated for applications in biology, biomedicine and biotechnology. Akkermansia muciniphila is an anaerobic intestinal commensal bacterium which possesses specific β-N-acetylhexosaminidases for gut mucosal layer colonization and mucin degradation. In this study, we assessed the in vitro mucin glycan cleavage activity of the A. muciniphila β-N-acetylhexosaminidase Am2136 and demonstrated its ability that hydrolyzing the β-linkages joining N-acetylglucosamine to a wide variety of aglycone residues, which indicated that Am2136 may be a generalist β-N-acetylhexosaminidase. Structural and enzyme activity assay experiments allowed us to probe the essential function of the inter-domain interactions in β23-β33. Importantly, we revealed that the hydrolysis activity of Am2136 was enhanced by nucleotides. We further speculated that this activation mechanism might be associated with the conformational motions between domain III and IV. To our knowledge, this is the first report of nucleotide effector regulated β-N-acetylhexosaminidase, to reveal its novel biological functions. These findings contribute to understanding the distinct properties within the GH20 family and lay a certain foundation to develop controllable glycan hydrolyzing catalysts.Abbreviations: OD600 - optical cell densities at 600 nm; LB - Luria-Bertani; IPTG - isopropyl β-D-1-thiogalactopyranoside; PMSF - phenylmethanesulfonyl fluoride; rmsd - root mean square deviation; GlcNAc - N-acetyl-β-D-glucosamine; GalNAc - N-acetyl-β-D-galactosamine; Gal - galactose.

Structural analysis of the sulfatase AmAS from Akkermansia muciniphila

Akkermansia muciniphila, an anaerobic Gram-negative bacterium, is a major intestinal commensal bacterium that can modulate the host immune response. It colonizes the mucosal layer and produces nutrients for the gut mucosa and other commensal bacteria. It is believed that mucin desulfation is the rate-limiting step in the mucin-degradation process, and bacterial sulfatases that carry out mucin desulfation have been well studied. However, little is known about the structural characteristics of A. muciniphila sulfatases. Here, the crystal structure of the premature form of the A. muciniphila sulfatase AmAS was determined. Structural analysis combined with docking experiments defined the critical active-site residues that are responsible for catalysis. The loop regions I–V were proposed to be essential for substrate binding. Structure-based sequence alignment and structural superposition allow further elucidation of how different subclasses of formylglycine-dependent sulfatases (FGly sulfatases) adopt the same catalytic mechanism but exhibit diverse substrate specificities. These results advance the understanding of the substrate-recognition mechanisms of A. muciniphila FGly-type sulfatases. Structural variations around the active sites account for the different substrate-binding properties. These results will enhance the understanding of the roles of bacterial sulfatases in the metabolism of glycans and host–microbe interactions in the human gut environment.

Structural and biochemical analysis of 1-Cys peroxiredoxin ScPrx1 from Saccharomyces cerevisiae mitochondria

BACKGROUND

ScPrx1 is a yeast mitochondrial 1-Cys peroxiredoxins (Prx), a type of Prx enzyme which require thiol-containing reducing agents to resolve its peroxidatic cysteine. ScPrx1 plays important role in protection against oxidative stress. Mitochondrial thioredoxin ScTrx3 and glutathione have been reported to be the physiological electron donor for ScPrx1. However, the mechanism underlying their actions, especially the substrate recognition of ScPrx1 requires additional elucidation.

METHODS

The structure of ScPrx1 was obtained through crystallization experiments. The oligomeric state of ScPrx1 was monitored by Blue-Native PAGE. Mutations were generated by the QuikChange PCR-based method. The ScPrx1 activity assay was carried out by measuring the change of 340 nm absorption of the NADPH oxidation.

RESULTS

ScPrx1 exist as a homodimer in solution. The structure adopts a typical Prx-fold core which is preceded by an N-terminal β-hairpin and has a C-terminal extension. Mutations (Glu94Ala, Arg198Ala and Trp126) close to the active site could enhance the catalytic efficiency of ScPrx1 while His83Ala and mutations on α4-β6 region exhibited reduced activity. The biochemical data also show that the deletion or mutations on ScPrx1 C-terminal have 2-4.56 fold increased activity.

CONCLUSION

We inferred that conformational changes of ScPrx1 C-terminal segment were important for its reaction, and the α4-β6 loop regions around the ScPrx1 active sites were important for the catalytic function of ScPrx1. Collectively, these structural features provides a basis for understanding the diverse reductant species usage in different 1-Cys Prxs.

Knockdown of human serine/threonine kinase 33 suppresses human small cell lung carcinoma by blocking RPS6/BAD signaling transduction

Small cell lung cancer (SCLC) is characterized by rapid growth rate and a tendency to metastasize to distinct sites of patients' bodies. The human serine/threonine kinase 33 (STK33) gene has shown its potency as a therapeutic target for prevention of lung carcinomas including non-small cell lung cancer (NSCLC), but its function in the oncogenesis and development of SCLC remains unrevealed. In the current study, it was hypothesized that STK33 played a key role in the proliferation, survival, and invasion of SCLC cells. The expression of STK33 in human SCLC cell lines NCI-H466 and DMS153 was inhibited by specific shRNA. The cell proliferation, cell apoptosis, and cell invasion of the cells were assessed with a series of in vitro assays. To explore the mechanism through which STK33 gene exerted its function in the carcinogenesis of SCLC cells, the effect of STK33 knockdown on the activity of S6K1/RPS6/BAD signaling was detected. Then the results were further confirmed with STK33 inhibitor ML281 and in vivo assays. The results demonstrated that inhibition of STK33 in SCLC cells suppressed the cell proliferation and invasion while induced cell apoptosis. Associated with the change in the phenotypic features, knockdown of STK33 also decreased the phosphorylation of RPS6 and BAD while increased the expression of cleaved caspase 9, indicating that apoptosis induced by STK33 suppression was mediated via mitochondrial pathway. Similar to the results of STK33 knockdown, incubating NCI-H466 cells with STK33 inhibitor also reduced the cell viability by suppressing RPS6/BAD pathways. Additionally, STK33 knockdown also inhibited tumor growth and RPS6/BAD activity in mice models. Findings outlined in our study were different from that in NSCLC to some extent: knockdown of STK33 in SCLC cells induced the apoptosis through mitochondrial pathway but independent of S6K1 function, inferring that the function of STK33 might be cancer type specific.

Crown gall -- a plant tumour with biological activities

Petroleum ether, acetone, 80% MeOH and water extracts of crown gall, a plant tumour, obtained from Eucalyptus globulus tree were screened for cytotoxic, antioxidant, antiinflammatory, embryotoxic, antitumour-promoting and antimicrobial activities. In terms of bioactivity the 80% MeOH extract was most effective followed by the acetone extract. The petroleum ether extract showed weak to moderate cytotoxic activity in dose-dependent manner against PC12 cells, mouse L fibroblasts and 1321N1 glia cells, whereas the hydroalcohol extract had no or a weak cytotoxic effect. The 80% MeOH extract exhibited strong antioxidant activity. Based on the in vitro HET-CAM assay all the extracts were effective against inflammation. The extracts did not show any embryotoxic effect at the concentrations tested. Antitumour-promoting activity (100% inhibition; 100 microg/mL) was observed in the 80% MeOH and acetone extracts. In the antimicrobial screening all extracts displayed predominantly antifungal activity against Candida sp. The extracts also showed various levels of antibacterial activity against E. faecalis, Ps. aeruginosa, Bac. subtilis and Staph. epidermidis. From the results of the investigations it can be concluded that crown gall is a valuable plant tumour tissue having interesting biological activities.

Cancer chemoprevention by ginseng in mouse liver and other organs

Oral administration of red ginseng extracts (1% in diet for 40 weeks) resulted in the significant suppression of spontaneous liver tumor formation in C3H/He male mice. Average number of tumors per mouse in control group was 1.06, while that in red ginseng extracts-treated group was 0.33 (p<0.05). Incidence of liver tumor development was also lower in red ginseng extracts-treated group, although the difference from control group was not statistically significant. Anti-carcinogenic activity of white ginseng extracts, besides red ginseng extracts, was also investigated. In the present study, the administration of white ginseng extracts was proven to suppress tumor promoter-induced phenomena in vitro and in vivo. It is of interest that oral administration of the extracts of Ren-Shen-Yang- Rong-Tang, a white ginseng-containing Chinese medicinal prescription, resulted in the suppression of skin tumor promotion by 12-o-tetradecanoylphorbol-13-acetate in 7,12-dimethylbenz[a]anthracene-initiated CD-1 mice. These results suggest the usefulness of ginseng in the field of cancer prevention.

Inhibitory effects of 6-O-acylated L-ascorbic acids possessing a straight- or branched-acyl chain on Epstein-Barr virus activation

6-O-Acylated L-ascorbic acids possessing a straight- or branched-acyl chain of varying length from C(4) to C(18) have been synthesized and evaluated their anti-tumor promoting effects on the activation of the Epstein-Barr virus early antigen. The derivatives having a straight- or branched-acyl chain of C(6) to C(11) carbon atoms exhibited marked effects.

Lignans as anti-tumor-promoter from the seeds of Hernandia ovigera

Seven lignans (2-8) isolated from the seeds of Hernandia ovigera L. (Hernandiaceae) were tested for their inhibitory effects on Epstein-Barr virus early antigen activation induced by 12-O-tetradecanoylphorbol 13-acetate in Raji cells. Using a primary screening test, all the lignans showed inhibitory activity with IC50 470-590 mol ratio/32 pmol TPA. The data demonstrated that these lignans might be valuable anti-tumor-promoters.

Antitumor promoting activities of 3-O-acyl-(-)epigallocatechins

As an exploratory investigation of antitumor promoting compounds, 3-O-acyl-(-)-epigallocatechins possessing a straight-, branched-, phenyl-inserted- or 1,4-phenylene-inserted-acyl chain of varying length from C4 to C18 were synthesized and evaluated their inhibitory effects against the activation of the Epstein-Barr virus early antigen (EBV-EA). It was indicated that the epigallocatechin derivatives having the straight- or branched-acyl chain of C8 to C11 carbon atoms achieve marked effects.

Inhibitory effect of flavonoids from citrus plants on Epstein-Barr virus activation and two-stage carcinogenesis of skin tumors

To search for possible anti-tumor promoters, thirteen flavones (1-13) obtained from the peel of Citrus plants were examined for their inhibitory effects on the Epstein-Barr virus early antigen (EBV-EA) activation by a short-term in vitro assay. Of these flavones, 3,5,6,7,8,3',4'-heptamethoxyflavone (HPT) (13) exhibited significant inhibitory effects on the EBV-EA activation induced by the tumor promoter, 12-O-tetradecanoylphorbol 13-acetate (TPA). Further, compound 13 exhibited remarkable inhibitory effects on mouse skin tumor promotion in an in vivo two-stage carcinogenesis test.

Conversion of quassinoids for enhancement of inhibitory effect against Epstein-Barr virus early antigen activation. Introduction of lipophilic side chain and esterification of diosphenol

Introduction of a senecioyl group into shinjulactones B and C, and esterification of the diosphenol moiety in brusatol and brucein A enhanced inhibitory effect against Epstein-Barr virus early antigen activation.