Increased glutaminyl cyclase activity in brains of Alzheimer's disease individuals.

Glutaminyl cyclases (QC) catalyze the formation of neurotoxic pGlu-modified amyloid-ß peptides found in the brains of people with Alzheimer's disease (AD). Reports of several-fold increases in soluble QC (sQC) expression in the brain and peripheral circulation of AD individuals has prompted the development of QC inhibitors as potential AD therapeutics. There is, however, a lack of standardized quantitative data on QC expression in human tissues, precluding inter-laboratory comparison and validation. We tested the hypothesis that QC is elevated in AD tissues by quantifying levels of sQC protein and activity in post-mortem brain tissues from AD and age-matched control individuals. We found a modest but statistically significant increase in sQC protein, which paralleled a similar increase in enzyme activity. In plasma samples sourced from the Australian Imaging, Biomarker and Lifestyle study we determined that QC activity was not different between the AD and control group, though a modest increase was observed in female AD individuals compared to controls. Plasma QC activity was further correlated with levels of circulating monocytes in AD individuals. These data provide quantitative evidence that alterations in QC expression are associated with AD pathology.

Bioinformatic analysis and experimental identification of blood biomarkers for chronic nonunion.

BACKGROUND: Incomplete fracture healing may lead to chronic nonunion; thus, determining fracture healing is the primary issue in the clinical treatment. However, there are no validated early diagnostic biomarkers for assessing chronic nonunion. In this study, bioinformatics analysis combined with an experimental verification strategy was used to identify blood biomarkers for chronic nonunion. METHODS: First, differentially expressed genes in chronic nonunion were identified by microarray data analysis. Second, Dipsaci Radix (DR), a traditional Chinese medicine for fracture treatment, was used to screen the drug target genes. Third, the drug-disease network was determined, and biomarker genes were obtained. Finally, the potential blood biomarkers were verified by ELISA and qPCR methods. RESULTS: Fifty-five patients with open long bone fractures (39 healed and 16 nonunion) were enrolled in this study, and urgent surgical debridement and the severity of soft tissue injury had a significant effect on the prognosis of fracture. After the systems pharmacology analysis, six genes, including QPCT, CA1, LDHB, MMP9, UGCG, and HCAR2, were chosen for experimental validation. We found that all six genes in peripheral blood mononuclear cells (PBMCs) and serum were differentially expressed after injury, and five genes (QPCT, CA1, MMP9, UGCG, and HCAR2) were significantly lower in nonunion patients. Further, CA1, MMP9, and QPCT were markedly increased after DR treatment. CONCLUSION: CA1, MMP9, and QPCT are biomarkers of nonunion patients and DR treatment targets. However, HCAR2 and UGCG are biomarkers of nonunion patients but not DR treatment targets. Therefore, our findings may provide valuable information for nonunion diagnosis and DR treatment. TRIAL REGISTRATION: ISRCTN, ISRCTN13271153. Registered 05 April 2020-Retrospectively registered.

Transpeptidation-Mediated Assembly of Tripartite Split Green Fluorescent Protein for Label-Free Assay of Sortase Activity.

Transpeptidation of surface proteins catalyzed by the transpeptidase sortase plays a critical role in the infection process of Gram-positive pathogen, and probing sortase activity and screening its inhibitors are of great significance to fundamental biological research and pharmaceutical development, especially novel antivirulence drug design. Herein, we developed a novel fluorescent biosensor to detect sortase activity based on a transpeptidation-triggered assembly of tripartite split green fluorescent protein (split GFP). Peptide P1, composed the 10th ß-sheet of GFP (GFP10) and the sortase A (SrtA) recognition sequence (LPETX), and peptide P2, the 11th ß-sheet of GFP (GFP11) with oligoglycine at N-terminal, were designed and synthesized, respectively. Existence of SrtA enables P1 and P2 to ligate into one peptide, which could spontaneously bind to GFP1-9 (the 1st to 9th ß-sheets of GFP) and assemble into functional GFP. Thus, the sortase-catalyzed transpeptidation can switch on the fluorescence signal of GFP. The method was successfully applied to detect SrtA activity with a low detection limit of 0.16 nM and for its inhibition measurement. Moreover, the feasibility of the proposed assay was further expanded to detect SrtA in human blood and further Gram-positive pathogens analysis in frozen food. Our method, using tripartite split GFP as a readout, is facile, label-free, and sensitive and exhibits great potential as a promising platform for sortase detection and inhibitor screening.

Increased glutaminyl cyclase expression in peripheral blood of Alzheimer's disease patients.

N-truncated and N-modified forms of amyloid-ß (Aß) peptide are found in diffused and dense core plaques in Alzheimer's disease (AD) brain. Among them, the most abundant N-truncated peptide starts with pyroglutamyl at residue 3 (AßpE3). AßpE3 has increased aggregation potential and toxicity and its abundance has been reported to correlate with the severity of the clinical phenotype in AD patients. N-terminal glutamate conversion generating AßpE3 is catalyzed by glutaminyl cyclase. This enzyme was found to be upregulated in the cortex of patients with AD. In the present study, we investigated glutaminyl cyclase mRNA and protein expression in peripheral blood from AD patients and age-matched controls. Higher levels of glutaminyl cyclase mRNA and protein were present in AD patients compared with controls. Interestingly, we observed a correlation between glutaminyl cyclase expression and the severity of dementia (value of Mini-Mental State Examination). Therefore, we propose glutaminyl cyclase dosage in peripheral blood as a potential biomarker of AD.

A universal immuno-PCR platform for comparative and ultrasensitive quantification of dual affinity-tagged proteins in complex matrices.

Protein detection in complex biological fluids and matrices has become a widely diversified field utilizing a number of different technologies. The quantification of target proteins in complex media such as serum remains a challenge for most technologies such as mass spectrometry, ELISA and western blot. Quantitative Immuno-PCR has been heavily used for antigen detection in immunoassays, but minimally so for quantifying affinity-tagged proteins expressed or circulating in complex matrices--despite its high sensitivity and robustness--because it suffers from detrimental background effects arising from its extreme detection power. We report the development of a universal qIPCR-based platform for the reproducible detection of dual affinity-tagged protein analytes in crude complex matrices such as serum and cell culture media or lysates. The system uses a couple of high-affinity antibodies against two affinity tags (GFP and HA) for the detection of dual-tagged proteins. The dual-tagged analyte is immuno-captured by one of its tags, while the second tag is bound by a detection device consisting of a new kind of self-assembled antibody-DNA conjugate. The new qIPCR platform enabled picomolar quantification of dual-tagged sortase in crude serum in 4 h including the PCR step.