E339...R416 salt bridge of nucleoprotein as a feasible target for influenza virus inhibitors.

The nucleoprotein (NP) of the influenza virus exists as trimers, and its tail-loop binding pocket has been suggested as a potential target for antiinfluenza therapeutics. The possibility of NP as a drug target was validated by the recent reports that nucleozin and its analogs can inhibit viral replication by inducing aggregation of NP trimers. However, these inhibitors were identified by random screening, and the binding site and inhibition mechanism are unclear. We report a rational approach to target influenza virus with a new mechanism--disruption of NP-NP interaction. Consistent with recent work, E339A, R416A, and deletion mutant Δ402-428 were unable to support viral replication in the absence of WT NP. However, only E339A and R416A could form hetero complex with WT NP, but the complex was unable to bind the RNA polymerase, leading to inhibition of viral replication. These results demonstrate the importance of the E339…R416 salt bridge in viral survival and establish the salt bridge as a sensitive antiinfluenza target. To provide further support, we showed that peptides encompassing R416 can disrupt NP-NP interaction and inhibit viral replication. Finally we performed virtual screening to target E339…R416, and some small molecules identified were shown to disrupt the formation of NP trimers and inhibit replication of WT and nucleozin-resistant strains. This work provides a new approach to design antiinfluenza drugs.

Design and synthesis of glyco-peptides as anti-cancer agents targeting thrombin-protease activated receptor-1 interaction.

Thrombin activates protease-activated receptor-1 (PAR-1) through binding to exosite I and the active site to promote tumor growth. We have developed a new class of anti-cancer glyco-peptides to target exosite I selectively without affecting the active-site-mediated coagulation activity and showed the importance of glycans for the stability and anti-cancer activity of the glyco-peptides.

Rationally designed divalent caffeic amides inhibit amyloid-ß fibrillization, induce fibril dissociation, and ameliorate cytotoxicity.

One of the pathologic hallmarks in Alzheimer's disease (AD) is extracellular senile plaques composed of amyloid-ß (Aß) fibrils. Blocking Aß self-assembly or disassembling Aß aggregates by small molecules would be potential therapeutic strategies to treat AD. In this study, we synthesized a series of rationally designed divalent compounds and examined their effects on Aß fibrillization. A divalent amide (2) derived from two molecules of caffeic acid with a propylenediamine linker of ∼5.0 Šin length, which is close to the distance of adjacent ß sheets in Aß fibrils, showed good potency to inhibit Aß(1-42) fibrillization. Furthermore, compound 2 effectively dissociated the Aß(1-42) preformed fibrils. The cytotoxicity induced by Aß(1-42) aggregates in human neuroblastoma was reduced in the presence of 2, and feeding 2 to Aß transgenic C. elegans rescued the paralysis phenotype. In addition, the binding and stoichiometry of 2 to Aß(1-40) were demonstrated by using electrospray ionization-traveling wave ion mobility-mass spectrometry, while molecular dynamic simulation was conducted to gain structural insights into the Aß(1-40)-2 complex.

Structural Investigation of Park's Nucleotide on Bacterial Translocase MraY: Discovery of Unexpected MraY Inhibitors.

Systematic structural modifications of the muramic acid, peptide, and nucleotide moieties of Park's nucleotide were performed to investigate the substrate specificity of B. subtilis MraY (MraYBS). It was found that the simplest analogue of Park's nucleotide only bearing the first two amino acids, l-alanine-iso-d-glutamic acid, could function as a MraYBS substrate. Also, the acid group attached to the Cα of iso-d-glutamic acid was found to play an important role for substrate activity. Epimerization of the C4-hydroxyl group of muramic acid and modification at the 5-position of the uracil in Park's nucleotide were both found to dramatically impair their substrate activity. Unexpectedly, structural modifications on the uracil moiety changed the parent molecule from a substrate to an inhibitor, blocking the MraYBS translocation. One unoptimized inhibitor was found to have a Ki value of 4 ± 1 µM against MraYBS, more potent than tunicamycins.