title: Effect of synthetic aβ peptide oligomers and fluorinated solvents on Kv1.3 channel properties and membrane conductance.
abstract: The impact of synthetic amyloid β (1-42) (Aβ(1-42)) oligomers on biophysical properties of voltage-gated potassium channels Kv 1.3 and lipid bilayer membranes (BLMs) was quantified for protocols using hexafluoroisopropanol (HFIP) or sodium hydroxide (NaOH) as solvents prior to initiating the oligomer formation. Regardless of the solvent used Aβ(1-42) samples contained oligomers that reacted with the conformation-specific antibodies A11 and OC and had similar size distributions as determined by dynamic light scattering. Patch-clamp recordings of the potassium currents showed that synthetic Aβ(1-42) oligomers accelerate the activation and inactivation kinetics of Kv 1.3 current with no significant effect on current amplitude. In contrast to oligomeric samples, freshly prepared, presumably monomeric, Aβ(1-42) solutions had no effect on Kv 1.3 channel properties. Aβ(1-42) oligomers had no effect on the steady-state current (at -80 mV) recorded from Kv 1.3-expressing cells but increased the conductance of artificial BLMs in a dose-dependent fashion. Formation of amyloid channels, however, was not observed due to conditions of the experiments. To exclude the effects of HFIP (used to dissolve lyophilized Aβ(1-42) peptide), and trifluoroacetic acid (TFA) (used during Aβ(1-42) synthesis), we determined concentrations of these fluorinated compounds in the stock Aβ(1-42) solutions by (19)F NMR. After extensive evaporation, the concentration of HFIP in the 100× stock Aβ(1-42) solutions was ∼1.7 μM. The concentration of residual TFA in the 70× stock Aβ(1-42) solutions was ∼20 μM. Even at the stock concentrations neither HFIP nor TFA alone had any effect on potassium currents or BLMs. The Aβ(1-42) oligomers prepared with HFIP as solvent, however, were more potent in the electrophysiological tests, suggesting that fluorinated compounds, such as HFIP or structurally-related inhalational anesthetics, may affect Aβ(1-42) aggregation and potentially enhance ability of oligomers to modulate voltage-gated ion channels and biological membrane properties.
authors.affiliation: Department of Physiology and Biophysics, University of California Irvine, Irvine, Calfornia, United States of America.
authors.forename: Maria I
authors.initials: MI
authors.lastname: Lioudyno
authors.forename: Matteo
authors.initials: M
authors.lastname: Broccio
authors.forename: Yuri
authors.initials: Y
authors.lastname: Sokolov
authors.forename: Suhail
authors.initials: S
authors.lastname: Rasool
authors.forename: Jessica
authors.initials: J
authors.lastname: Wu
authors.forename: Michael T
authors.initials: MT
authors.lastname: Alkire
authors.forename: Virginia
authors.initials: V
authors.lastname: Liu
authors.forename: J Ashot
authors.initials: JA
authors.lastname: Kozak
authors.forename: Philip R
authors.initials: PR
authors.lastname: Dennison
authors.forename: Charles G
authors.initials: CG
authors.lastname: Glabe
authors.forename: Mathias
authors.initials: M
authors.lastname: Lösche
authors.forename: James E
authors.initials: JE
authors.lastname: Hall
mesh_terms: D016229:Amyloid beta-Peptides / Q000138:chemical synthesis / Q000494:pharmacology*; D004553:Electric Conductivity; D054879:Halogenation; D007700:Kinetics; D051664:Kv1.3 Potassium Channel / Q000378:metabolism*; D008027:Light; D008051:Lipid Bilayers / Q000378:metabolism*; D008567:Membranes, Artificial; D018408:Patch-Clamp Techniques; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000494:pharmacology*; D020005:Propanols / Q000737:chemistry; D012542:Scattering, Radiation; D012972:Sodium Hydroxide / Q000737:chemistry; D012997:Solvents / Q000737:chemistry*; D006845:Hydrocarbons, Fluorinated
chemical_list: D016229:Amyloid beta-Peptides; D051664:Kv1.3 Potassium Channel; D008051:Lipid Bilayers; D008567:Membranes, Artificial; D010446:Peptide Fragments; D020005:Propanols; D012972:Sodium Hydroxide; D012997:Solvents; C075222:amyloid beta-protein (1-42); C001337:hexafluoroisopropanol; D006845:Hydrocarbons, Fluorinated