title: Modulation of Kv4.2 channels by a peptide isolated from the venom of the giant bird-eating tarantula Theraphosa leblondi.
abstract: In order to find new peptide inhibitors for voltage-dependent potassium (Kv) channels, we examined the effects of venom from Theraphosa leblondi on Kv channel-mediated currents with the whole-cell patch-clamp technique. Both A-type currents in cultured hippocampal neurons and A-type currents recorded from HEK 293 cells transiently expressing recombinant Kv4.2 channels were selectively inhibited by T. leblondi venom. No venom activity was observed on recombinant Kv1.3, Kv1.4, Kv2.1 or Kv3.4 channels. We purified and sequenced three novel homologous peptides from this venom, which are related to previously identified Kv4 channel-specific peptide inhibitors and were named T. leblondi toxin (TLTx) 1, 2 and 3. The mode of action of TLTx1 on recombinant Kv4.2 channels was studied in more detail. TLTx1 inhibited Kv4.2-mediated currents with an IC50 of approximately 200 nM, and macroscopic current inactivation was slowed in the presence of TLTx1. Notably, TLTx1 also caused a shallower voltage dependence of Kv4.2 peak conductance and a shift of the activation midpoint to more positive potentials (DeltaV1/2 = +35 mV). TLTx1 caused a noticable slowing of Kv4.2 activation kinetics, and Kv4.2 deactivation kinetics were accelerated by TLTx1 as infered from Rb+ tail current measurements. Chimeric Kv2.1(4.2L3-4) channels, in which the linker region between S3 and S4 of the TLTx1-insensitive Kv2.1 channel was replaced by the corresponding Kv4.2 domain, were sensitive to TLTx1. Apparently, TLTx1 can act as a gating modifier of Kv4.2 channels.
authors.affiliation: Institut für Neurale Signalverarbeitung, Zentrum für Molekulare Neurobiologie der Universität Hamburg, Martinistrasse 52, Hamburg 20246, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Ebbinghaus
authors.forename: Christian
authors.initials: C
authors.lastname: Legros
authors.forename: Andreas
authors.initials: A
authors.lastname: Nolting
authors.forename: Catherine
authors.initials: C
authors.lastname: Guette
authors.forename: Marie-Louise
authors.initials: ML
authors.lastname: Celerier
authors.forename: Olaf
authors.initials: O
authors.lastname: Pongs
authors.forename: Robert
authors.initials: R
authors.lastname: Bähring
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002478:Cells, Cultured; D005591:Chemical Fractionation; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D005616:French Guiana; D006801:Humans; D007700:Kinetics; D013058:Mass Spectrometry; D051379:Mice; D008969:Molecular Sequence Data; D009474:Neurons / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects* / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D051672:Shal Potassium Channels; D013111:Spider Venoms / Q000378:metabolism / Q000494:pharmacology*; D013112:Spiders / Q000737:chemistry*
chemical_list: C497018:KCND2 protein, human; C497019:Kcnd2 protein, mouse; D010455:Peptides; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D051672:Shal Potassium Channels; D013111:Spider Venoms