Plasma nontargeted peptidomics discovers potential biomarkers for major depressive disorder.

PURPOSE: There are great demands for identifying biomarkers of major depressive disorder (MDD), a common mental illness with a prevalence of approximately 6%. Finding potential biomarkers to aid MDD diagnosis is in high demand. EXPERIMENTAL DESIGN: In this study, a combination of pretreatment methods named salt-out assisted liquid-liquid extraction (SALLE) and nontargeted peptidomics based on nano-LC-Orbitrap/MS was primarily employed to discover the candidate peptide markers from the plasma of 238 subjects. RESULTS: Many peptides were enriched and identified from the plasma, 42 of which showed significant differences between MDD patients and controls by univariate statistical analysis. A binary logistic regression (BLR) model combined four peptide markers (P1, P9, P17, P29) was established, yielding an overall prediction accuracy of 91.7% and 82.2% in the discovery and validation sets, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: In conclusion, the excellent performance of the BLR model in both discovery and validation sets demonstrates the robustness of the four peptide markers panel. It is very valuable for quantification of the absolute content of four peptides and further verification.

Disaggregation of Amylin Aggregate by Novel Conformationally Restricted Aminobenzoic Acid containing α/ß and α/γ Hybrid Peptidomimetics.

Diabetes has emerged as a threat to the current world. More than ninety five per cent of all the diabetic population has type 2 diabetes mellitus (T2DM). Aggregates of Amylin hormone, which is co-secreted with insulin from the pancreatic ß-cells, inhibit the activities of insulin and glucagon and cause T2DM. Importance of the conformationally restricted peptides for drug design against T2DM has been invigorated by recent FDA approval of Symlin, which is a large conformationally restricted peptide. However, Symlin still has some issues including solubility, oral bioavailability and cost of preparation. Herein, we introduced a novel strategy for conformationally restricted peptide design adopting a minimalistic approach for cost reduction. We have demonstrated efficient inhibition of amyloid formation of Amylin and its disruption by a novel class of conformationally restricted ß-sheet breaker hybrid peptidomimetics (BSBHps). We have inserted ß, γ and δ -aminobenzoic acid separately into an amyloidogenic peptide sequence, synthesized α/ß, α/γ and α/δ hybrid peptidomimetics, respectively. Interestingly, we observed the aggregation inhibitory efficacy of α/ß and α/γ BSBHps, but not of α/δ analogues. They also disrupt existing amyloids into non-toxic forms. Results may be useful for newer drug design against T2DM as well as other amyloidoses and understanding amyloidogenesis.

Inhibition of enterovirus 71 replication by an α-hydroxy-nitrile derivative NK-1.9k.

Enterovirus 71 (EV71) is one of the major etiological agents of human hand-foot-and-mouth disease (HFMD) worldwide. EV71 infection in young children and people with immunodeficiency causes severe symptoms with a high fatality rates. However, there is still no approved drugs to treat such infections. Based on our previous report of a peptide-aldehyde anti-EV71 protease, we present here a highly specific α-hydroxy-nitrile derivative NK-1.9k, which inhibited the proliferation of multiple EV71 strains and coxsackievirus A16 (CVA16) in various cells with EC50 of 37.0 nM with low cytotoxicity (CC50 > 200 µM). The hydroxy-nitrile covalent warhead conferred NK-1.9k high potency and selectivity to interact with the cysteine residue of the active site of the viral protease. We also documented the resistance to NK-1.9k with a N69S mutation in EV71 3Cpro. The combination of NK-1.9k and EV71 polymerase or entry inhibitors produced strong synergistic antiviral effects. Collectively, our findings suggest our compounds can potentially be developed as drugs for the treatment of HFMD.

Identification of Peptide Mimics of a Glycan Epitope on the Surface of Parasitic Nematode Larvae.

Phage display was used to identify peptide mimics of an immunologically protective nematode glycan (CarLA) by screening a constrained C7C peptide library for ligands that bound to an anti-CarLA mAb (PAB1). Characterisation of these peptide mimotopes revealed functional similarities with an epitope that is defined by PAB1. Mimotope vaccinations of mice with three selected individual phage clones facilitated the induction of antibody responses that recognised the purified, native CarLA molecule which was obtained from Trichostrongylus colubriformis. Furthermore, these mimotopes are specifically recognised by antibodies in the saliva of animals that were immune to natural polygeneric nematode challenge. This shows that antibodies to the PAB1 epitope form part of the mucosal polyclonal anti-CarLA antibody response of nematode immune host animals. This demonstrates that the selected peptide mimotopes are of biological relevance. These peptides are the first to mimic the PAB1 epitope of CarLA, a defined larval glycan epitope which is conserved between many nematode species.

Design-Based Peptidomimetic Ligand Discovery to Target HIV TAR RNA Using Comparative Analysis of Different Docking Methods.

Discovering molecules capable of binding to HIV trans-activation responsive region (TAR) RNA thereby disrupting its interaction with Tat protein is an attractive strategy for developing novel antiviral drugs. Computational docking is considered as a useful tool for predicting binding affinity and conducting virtual screening. Although great progress in predicting protein-ligand interactions has been achieved in the past few decades, modeling RNA-ligand interactions is still largely unexplored due to the highly flexible nature of RNA. In this work, we performed molecular docking study with HIV TAR RNA using previously identified cyclic peptide L22 and its analogues with varying affinities toward HIV-1 TAR RNA. Furthermore, sarcosine scan was conducted to generate derivatives of CGP64222, a peptide-peptoid hybrid with inhibitory activity on Tat/TAR RNA interaction. Each compound was docked using CDOCKER, Surflex-Dock and FlexiDock to compare the effectiveness of each method. It was found that FlexiDock energy values correlated well with the experimental Kd values and could be used to predict the affinity of the ligands toward HIV-1 TAR RNA with a superior accuracy. Our results based on comparative analysis of different docking methods in RNA-ligand modeling will facilitate the structure-based discovery of HIV TAR RNA ligands for antiviral therapy.