An innate pathogen sensing strategy involving ubiquitination of bacterial surface proteins.

Sensing of pathogens by ubiquitination is a critical arm of cellular immunity. However, universal ubiquitination targets on microbes remain unidentified. Here, using in vitro, ex vivo, and in vivo studies, we identify the first protein-based ubiquitination substrates on phylogenetically diverse bacteria by unveiling a strategy that uses recognition of degron-like motifs. Such motifs form a new class of intra-cytosolic pathogen-associated molecular patterns (PAMPs). Their incorporation enabled recognition of nonubiquitin targets by host ubiquitin ligases. We find that SCFFBW7 E3 ligase, supported by the regulatory kinase, glycogen synthase kinase 3ß, is crucial for effective pathogen detection and clearance. This provides a mechanistic explanation for enhanced risk of infections in patients with chronic lymphocytic leukemia bearing mutations in F-box and WD repeat domain containing 7 protein. We conclude that exploitation of this generic pathogen sensing strategy allows conservation of host resources and boosts antimicrobial immunity.

Comparative study of cyto- and genotoxic potential with mechanistic insights of tungsten oxide nano- and microparticles in lung carcinoma cells.

The exigency of semiconductor and super capacitor tungsten oxide nanoparticles (WO3 NPs) is increasing in various sectors. However, limited information on their toxicity and biological interactions are available. Hence, we explored the underlying mechanisms of toxicity induced by WO3 NPs and their microparticles (MPs) using different concentrations (0-300 µg ml-1 ) in human lung carcinoma (A549) cells. The mean size of WO3 NPs and MPs by transmission electron microscopy was 53.84 nm and 3.88 µm, respectively. WO3 NPs induced reduction in cell viability, membrane damage and the degree of induction was size- and dose-dependent. There was a significant increase in the percentage tail DNA and micronuclei formation at 200 and 300 µg ml-1 after 24 hours of exposure. The DNA damage induced by WO3 NPs could be attributed to increased oxidative stress and inflammation through reactive oxygen species generation, which correlated with the depletion of reduced glutathione content, catalase and an increase in malondialdehyde levels. Cellular uptake studies unveiled that both the particles were attached/surrounded to the cell membrane according to their size. In addition, NP inhibited the progression of the cell cycle in the G2 /M phase. Other studies such as caspase-9 and -3 and Annexin-V-fluorescein isothiocyanate revealed that NPs induced intrinsic apoptotic cell death at 200 and 300 µg ml-1 concentrations. However, in comparison to NPs, WO3 MPs did not incite any toxic effects at the tested concentrations. Under these experimental conditions, the no-observed-significant-effect level of WO3 NPs was determined to be ≤200 µg ml-1 in A549 cells.