title: Ion channel activity of the CSFV p7 viroporin in surrogates of the ER lipid bilayer.
abstract: Viroporins comprise a family of non-structural proteins that play significant and diverse roles during the replication cycle of many animal viruses. Consequently, they have become promising targets for inhibitory drug and vaccine development. Structure–function traits common to all members of the family are their small size (ca. 60–120 aa), high hydrophobicity, and the presence of helical domains that transverse the membrane and assemble into oligomeric-permeating structures therein. The possibility that viroporins show in particular conditions any kind of specificity in the transport of ions and small solutes remains a point of contention in the field. Here we have approached this issue using the Classical Swine Fever Virus (CSFV) protein p7 viroporin as a model. We have previously reported that CSFV-p7 induces release of ANTS (MW: 427.33) from lipid vesicles that emulate the Endoplasmic Reticulum (ER) membrane, and that this process is dependent on pH, modulated by the lipid composition, and recreated by a C-terminal transmembrane helix. Here we have assayed CSFV-p7 for its capacity to form ion-conducting channels in ER-like planar lipid membranes, and established whether this activity is subject to regulation by the same factors. The analysis of electrophysiological recordings in ER membrane surrogates suggests that CSFV-p7 forms pores wide enough to allow ANTS release. Moreover, we were able to discriminate between two pore structures with slightly different sizes and opposite ion selectivities. The fact that the relative abundances of each pore type depend crucially on membrane composition strengthens the view that the physicochemical properties of the lipid bilayers present in the cell endomembrane system modulate viroporin activity.
authors.affiliation: Biophysics Unit (CSIC, UPV/EHU), Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain.
authors.forename: Eneko
authors.initials: E
authors.lastname: Largo
authors.affiliation: Laboratory of Molecular Biophysics, Department of Physics, University Jaume I, 12071 Castellón, Spain.
authors.forename: Carmina
authors.initials: C
authors.lastname: Verdiá-Báguena
authors.affiliation: Laboratory of Molecular Biophysics, Department of Physics, University Jaume I, 12071 Castellón, Spain.
authors.forename: Vicente M
authors.initials: VM
authors.lastname: Aguilella
authors.affiliation: Biophysics Unit (CSIC, UPV/EHU), Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain.
authors.forename: José L
authors.initials: JL
authors.lastname: Nieva
authors.affiliation: Laboratory of Molecular Biophysics, Department of Physics, University Jaume I, 12071 Castellón, Spain. Electronic address: alcaraza@uji.es.
authors.forename: Antonio
authors.initials: A
authors.lastname: Alcaraz
mesh_terms: D040761:Biomimetic Materials; D002784:Cholesterol / Q000737:chemistry; D006692:Classical Swine Fever Virus / Q000737:chemistry; D004721:Endoplasmic Reticulum / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D007473:Ion Channels; D017136:Ion Transport; D008051:Lipid Bilayers / Q000737:chemistry*; D008958:Models, Molecular; D009281:Naphthalenes / Q000737:chemistry; D010713:Phosphatidylcholines / Q000737:chemistry; D010714:Phosphatidylethanolamines / Q000737:chemistry; D010716:Phosphatidylinositols / Q000737:chemistry; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D053835:Unilamellar Liposomes / Q000737:chemistry*; D054334:Viral Regulatory and Accessory Proteins / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D005456:Fluorescent Dyes; D007473:Ion Channels; D008051:Lipid Bilayers; D009281:Naphthalenes; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010716:Phosphatidylinositols; D053835:Unilamellar Liposomes; D054334:Viral Regulatory and Accessory Proteins; C483858:phosphatidylethanolamine; D002784:Cholesterol; C046465:8-amino-1,3,6-naphthalenetrisulfonic acid
keywords: Ion channels; Lipid vesicles; Planar membranes; Viroporins