title: Two tarantula venom peptides as potent and differential Na(V) channels blockers.
abstract: Voltage dependent sodium (Na(V)) channels are large membrane spanning proteins which lie in the basis of action potential generation and propagation in excitable cells and hence are essential mediators of neuronal signaling. Inhibition of Na(V) channel activity is one of the core mechanisms to treat conditions related to neuronal hyperexcitability, such as epilepsy in the clinic. Na(V) channel blockers are also extensively used to locally inhibit action potential generation and related pain perceptions in the form of local anesthetics. Here we describe the isolation, biochemical characterization, synthesis and in vitro characterization of two potent Na(V) channel blockers from the venom of the Paraphysa scrofa (Phrixotrichus auratus) tarantula spider. Both Voltage sensor toxin 3 (VSTx-3, κ-theraphotoxin-Gr4a) and GTx1-15 (Toxin Gtx1-15), were originally isolated from the venom of the related tarantula Grammostola rosea and described as K(V) and Ca(V) channel blockers, respectively. In our hands, GTx1-15 was shown to be a potent inhibitor of tetrodotoxin (TTX)-sensitive channels (IC₅₀ 0.007 μM for hNa(V)1.7 and 0.12 μM for hNa(V)1.3 channels), with very little effect on TTX-resistant (Na(V)1.5 and NaV1.8) channels. VSTx-3 was demonstrated to be a potent, TTX-sensitive sodium channel blocker and especially, potent blocker of Na(V)1.8 channels (IC₅₀ 0.19 μM for hNa(V)1.3, 0.43 μM for hNa(V)1.7 and 0.77 μM for hNa(V)1.8 channels). Such potent inhibitors with differential selectivity among Na(V) channel isoforms may be used as tools to study the roles of the different channels in processes related to hyperexcitability and as lead compounds to treat pathological pain conditions.
authors.affiliation: Alomone Labs Ltd, PO Box 4287, Jerusalem, Israel.
authors.forename: Ronit S
authors.initials: RS
authors.lastname: Cherki
authors.affiliation: Alomone Labs Ltd, PO Box 4287, Jerusalem, Israel.
authors.forename: Ela
authors.initials: E
authors.lastname: Kolb
authors.affiliation: Alomone Labs Ltd, PO Box 4287, Jerusalem, Israel.
authors.forename: Yael
authors.initials: Y
authors.lastname: Langut
authors.affiliation: Alomone Labs Ltd, PO Box 4287, Jerusalem, Israel.
authors.forename: Lior
authors.initials: L
authors.lastname: Tsveyer
authors.affiliation: Alomone Labs Ltd, PO Box 4287, Jerusalem, Israel.
authors.forename: Nissim
authors.initials: N
authors.lastname: Bajayo
authors.affiliation: Alomone Labs Ltd, PO Box 4287, Jerusalem, Israel. Electronic address: alon@alomone.com.
authors.forename: Alon
authors.initials: A
authors.lastname: Meir
mesh_terms: D000818:Animals; D001097:Arachnida / Q000737:chemistry*; D001483:Base Sequence; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D057809:HEK293 Cells; D006801:Humans; D020128:Inhibitory Concentration 50; D008969:Molecular Sequence Data; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000032:analysis / Q000235:genetics / Q000633:toxicity*; D017422:Sequence Analysis, DNA; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013111:Spider Venoms / Q000737:chemistry* / Q000302:isolation & purification; D061567:Voltage-Gated Sodium Channel Blockers / Q000032:analysis / Q000633:toxicity*
chemical_list: D010455:Peptides; D013111:Spider Venoms; D061567:Voltage-Gated Sodium Channel Blockers
keywords: Excitability; Na(V) channel; Pain; Tarantula venom