Picornavirus 2B, a non-structural protein required for effective viral replication, has been implicated in cell membrane permeabilization during the late phases of infection. Here, we have approached the molecular mechanism of this process by assessing the pore-forming activity of an overlapping peptide library that spanned the complete 2B sequence. At non-cytopathic concentrations, only the P3 peptide, spanning 2B residues 35–55, effectively assembled hydrophilic pores that allowed diffusion of low molecular mass solutes across the cell plasma membrane (IC50 ≈ 4 × 10−7 M) and boundary liposome bilayers (starting at peptide to lipid molar ratios > 1:104). Circular dichroism data were consistent with its capacity to fold as a helix in a membrane-like environment. Furthermore, addition of this peptide to a sealed plasma-membrane model, consisting of retinal rod outer segments patch-clamped in a whole-cell configuration, induced ion channel activity within seconds at concentrations as low as 10−8 M. Thus, we have established a “one-helix” 2B version that possesses the intrinsic pore-forming activity required to directly and effectively permeabilize the cell plasma membrane. We conclude that 2B viroporin can be classified as a genuine pore-forming toxin of viral origin, which is produced intracellularly at certain times post infection
We acknowledge the financial support of the DGICYT project numbers BFU2006-02182/BMC (to V.M. and L.C.) and BFU2005-06095/BMC (to S.S.M. and J.L.N.). Further support to J.L.N. was obtained from the Basque Government (AE2004-1-2) and the University of the Basque Country (042.310-13552). The CBM was awarded an institutional grant by the Fundación Ramón Areces. Financial support to G.R. included grants from the Ministero del'Università e della Ricerca (MIUR), Roma and from the “Comitato dei sostenitori dell'Università di Ferrara” (Project “Trasporto di carica fotoindotto in materiali funzionali”).
Peer reviewed