Hypersensitive immunoassay by using Escherichia coli outer membrane with autodisplayed Z-domains

In this work, the Z-domain of protein A was autodisplayed on the surface of the Escherichia coli outer membrane as a fusion protein of AIDA-1, and then layered on a microplate in order to develop a hypersensitive immunoassay. By using microplates with controlled hydrophilicity the formation of outer membrane layer was carried out, and the driving force for the layer formation was proven to be a hydrophobic interactions. Through the orientation control of the immobilized antibodies by using autodisplayed Z-domains, the limit of detection (LOD) and the sensitivity of this new immunoassay were determined to have improved as much as 30-fold compared to the conventional ELISA. The applicability of the new immunoassay for medical diagnosis was demonstrated by the detection of C-reactive protein (CRP) which is known to be a biomarker protein for inflammatory diseases.     

Inhibition of Snail1-DNA-PKcs Protein-Protein Interface Sensitizes Cancer Cells and Inhibits Tumor Metastasis

Our previous study suggested that the DNA-dependent protein kinase catalytic subunit (DNA-PKcs) interacts with Snail1, which affects genomic instability, sensitivity to DNA-damaging agents, and migration of tumor cells by reciprocal regulation between DNA-PKcs and Snail1. Here, we further investigate that a peptide containing 7-amino acid sequences (amino acids 15–21) of Snail1 (KPNYSEL, SP) inhibits the endogenous interaction between DNA-PKcs and Snail1 through primary interaction with DNA-PKcs. SP restored the inhibited DNA-PKcs repair activity and downstream pathways. On the other hand, DNA-PKcs-mediated phosphorylation of Snail1 was inhibited by SP, which resulted in decreased Snail1 stability and Snail1 functions. However, these phenomena were only shown in p53 wild-type cells, not in p53-defective cells. From these results, it is suggested that interfering with the protein interaction between DNA-PKcs and Snail1 might be an effective strategy for sensitizing cancer cells and inhibiting tumor migration, especially in both Snail1-overexpressing and DNA-PKcs-overexpressing cancer cells with functional p53.