Peptidomimetic ethyl propenoate covalent inhibitors of the enterovirus 71 3C protease: a P2-P4 study.

Enterovirus 71 (EV71) is a highly infectious pathogen primarily responsible for Hand, Foot, and Mouth Disease, particularly among children. Currently, no approved antiviral drug has been developed against this disease. The EV71 3C protease is deemed an attractive drug target due to its crucial role in viral polyprotein processing. Rupintrivir, a peptide-based inhibitor originally developed to target the human rhinovirus 3C protease, was found to inhibit the EV71 3C protease. In this communication, we report the inhibitory activities of 30 Rupintrivir analogs against the EV71 3C protease. The most potent inhibitor, containing a P2 ring-constrained phenylalanine analog (compound 9), was found to be two-fold more potent than Rupintrivir (IC50 value 3.4 ± 0.4 versus 7.3 ± 0.8 µM). Our findings suggest that employing geometrically constrained residues in peptide-based protease inhibitors can potentially enhance their inhibitory activities.

Rapid purification of recombinant dengue and West Nile virus envelope Domain III proteins by metal affinity membrane chromatography.

Arthropod-borne flaviviruses such as dengue virus (DENV) and West Nile virus (WNV) pose significant health threats to the global community. Due to escalating numbers of DENV and WNV infections worldwide, development of an effective vaccine remains a global health priority. As flavivirus envelope Domain III (DIII) protein is highly immunogenic and capable of inducing neutralizing antibodies against wild-type virus, it is both a potential protein subunit vaccine candidate and a suitable diagnostic reagent. Here, we describe the use of metal affinity membrane chromatography as a rapid and improved alternative for the purification of recombinant DIII (rDIII) antigens from DENV serotypes 1-4 and WNV - New York, Sarafend, Wengler and Kunjin strains. Optimum conditions for the expression, solubilization, renaturation and purification of these proteins were established. The purified proteins were confirmed by MALDI-TOF mass spectrometry and ELISA using antibodies raised against the respective viruses. Biological function of the purified rDIII proteins was confirmed by their ability to generate DIII-specific antibodies in mice that could neutralize the virus.

Identification of cell surface markers glypican-4 and CD200 that differentiate human corneal endothelium from stromal fibroblasts.

PURPOSE: There is a lack of definitive cell surface markers to differentiate cultured human corneal endothelial cells (HCECs) from stromal fibroblasts, which could contaminate HCEC cultures. The aim of our study is to discover cell surface antigens on HCECs that can be used to identify and purify HCECs from stromal fibroblasts. METHODS: RNA sequencing (RNA-seq) was used to find differentially overexpressed genes in HCECs and commercial antibodies against these overexpressed antigens were screened by immunofluorescence assay. Similarly, 242 commercial antibodies against cell-surface antigens also were screened. Selected antibodies were used to sort HCECs from stromal fibroblasts by fluorescence-activated cell sorting (FACS). RESULTS: Two monoclonal antibodies, anti-GPC4 and anti-CD200, were identified to stain HCECs specifically. FACS was used successfully to sort HCECs away from stromal fibroblasts. Recovery efficiency of HCECs after sorting using anti-GPC4 antibody was higher compared to anti-CD200 antibody, but purity of HCECs culture using either antibody was comparable. CONCLUSIONS: Taken together, the anti-GPC4 and anti-CD200 antibodies can be useful for purification and identification of HCECs in cultures containing stromal fibroblasts.

Dephosphorylation of West Nile virus capsid protein enhances the processes of nucleocapsid assembly.

West Nile virus (WNV) capsid (C) protein is one of the three viral structural proteins and it encapsidates the viral RNA to form the nucleocapsid. It is known to be a multifunctional protein involved in assembly and apoptosis. WNV C protein was previously found to be phosphorylated in infected cells and bioinformatic analysis revealed 5 putative phosphorylation sites at serine 26, 36, 83, 99 and threonine 100. Phosphorylation was abolished through mutagenesis of these putative phosphorylation sites to investigate how phosphorylation could affect the processes of nucleocapsid assembly like RNA binding, oligomerization and cellular localization. It was found that phosphorylation attenuated its RNA binding activity. Although oligomerization was not inhibited by mutagenesis of the putative phosphorylation sites, the rate of dimerization and oligomerization was affected. Hypophosphorylation of C protein reduced its nuclear localization efficiency and hence enhanced cytoplasmic localization. This study also revealed that although WNV C is phosphorylated in infected cells, the relative level of phosphorylation is reduced over the course of an infection to promote RNA binding and nucleocapsid formation in the cytoplasm. This is the first report to describe how dynamic phosphorylation of WNV C protein modulates the processes involved in nucleocapsid assembly.

West Nile virus capsid protein interaction with importin and HDM2 protein is regulated by protein kinase C-mediated phosphorylation.

West Nile virus (WNV) capsid (C) protein was shown to enter the nucleus via importin-mediated pathway and induce apoptosis although the precise regulatory mechanisms for such events have remained elusive. In this study, it was shown that WNV C protein was phosphorylated by protein kinase C (PKC). PKC-mediated phosphorylation influenced nuclear trafficking of C protein by modulating the efficiency of C protein-importin-alpha binding. Combination of bio-informatics, site-directed mutagenesis, co-immunoprecipitation, immuno-fluorescence and mammalian two-hybrid analyses showed that phosphorylation at amino acid residues residing near (Ser83) or within (Ser99 and Thr100) the bipartite nuclear localization motif of WNV C protein was essential for efficient interaction between C protein and importin-alpha. In addition, phosphorylation of WNV C protein by PKC was shown to enhance its binding to HDM2 and could subsequently induce p53-dependent apoptosis. Collectively, this study highlighted that phosphorylation is an important post-translational modification required to execute the functions of C protein.