Targeting Host Cell Furin Proprotein Convertases as a Therapeutic Strategy against Bacterial Toxins and Viral Pathogens

Ge Wei,Sergey A. Shiryaev,Jeffrey W. Smith,Nicholas A. Nelson,Tomas Mustelin,Amélie Parent ,Roxane Desjardins,Robert Day,Alex Y. Strongin,Robert Liddington ,Michele F. Rega,Albert G. Remacle,Mojgan Sabet,Donald G. Guiney,Maurizio Pellecchia,Martin Fugère ,Boris I. Ratnikov,Alexei Y. Savinov,Massimo Bottini,Michal Lebl

doi:10.1074/jbc.m703847200

Abstract

Pathogens or their toxins, including influenza virus, Pseudomonas, and anthrax toxins, require processing by host proprotein convertases (PCs) to enter host cells and to cause disease. Conversely, inhibiting PCs is likely to protect host cells from multiple furin-dependent, but otherwise unrelated, pathogens. To determine if this concept is correct, we designed specific nanomolar inhibitors of PCs modeled from the extended cleavage motif TPQRERRRKKR downward arrowGL of the avian influenza H5N1 hemagglutinin. We then confirmed the efficacy of the inhibitory peptides in vitro against the fluorescent peptide, anthrax protective antigen (PA83), and influenza hemagglutinin substrates and also in mice in vivo against two unrelated toxins, anthrax and Pseudomonas exotoxin. Peptides with Phe/Tyr at P1' were more selective for furin. Peptides with P1' Thr were potent against multiple PCs. Our strategy of basing the peptide sequence on a furin cleavage motif known for an avian flu virus shows the power of starting inhibitor design with a known substrate. Our results confirm that inhibiting furin-like PCs protects the host from the distinct furin-dependent infections and lay a foundation for novel, host cell-focused therapies against acute diseases.

Highlights

Expressed in all examined tissues and cell lines and is mainly localized in the trans-Golgi network
Derivatization of the Furin Cleavage Sequence—Furin and related proprotein convertases (PCs) are directly implicated in many pathogenic states, because they process membrane fusion proteins and pro-toxins of a variety of pathogenic bacteria and viruses, including anthrax and the highly pathogenic H5N1 avian influenza
Our results show that both protective antigen-83 (PA83) and the HA precursor (HA0) from the H5N1 influenza virus [13, 14] are sensitive to the processing by several individual PCs as opposed to furin alone (Fig. 1)

Summary

Introduction

Expressed in all examined tissues and cell lines and is mainly localized in the trans-Golgi network. Evidence suggests that the inhibition of cellular furin prevents aggressive disease [2, 5]. These results lead to the logical suggestion that furin is a promising drug target in infectious diseases; an experimental confirmation, has been limited because research efforts have been focused primarily on anthrax [5,6,7]. Arg-based peptides such as hexa- and nona-D-Arg [8] have either low or no therapeutic potential because of their intrinsic ability to cross-react with multiple, pathogen and host, proteinase and non-proteinase targets, which are unrelated to furin (6, 9 –11). Our results suggest that furin antagonists can provide host protection against multiple furin-dependent, but otherwise unrelated pathogens

Methods

Results

Conclusion