title: Two tarantula peptides inhibit activation of multiple sodium channels.
abstract: Two peptides, ProTx-I and ProTx-II, from the venom of the tarantula Thrixopelma pruriens, have been isolated and characterized. These peptides were purified on the basis of their ability to reversibly inhibit the tetrodotoxin-resistant Na channel, Na(V) 1.8, and are shown to belong to the inhibitory cystine knot (ICK) family of peptide toxins interacting with voltage-gated ion channels. The family has several hallmarks: cystine bridge connectivity, mechanism of channel inhibition, and promiscuity across channels within and across channel families. The cystine bridge connectivity of ProTx-II is very similar to that of other members of this family, i.e., C(2) to C(16), C(9) to C(21), and C(15) to C(25). These peptides are the first high-affinity ligands for tetrodotoxin-resistant peripheral nerve Na(V) channels, but also inhibit other Na(V) channels (IC(50)'s < 100 nM). ProTx-I and ProTx-II shift the voltage dependence of activation of Na(V) 1.5 to more positive voltages, similar to other gating-modifier ICK family members. ProTx-I also shifts the voltage dependence of activation of Ca(V) 3.1 (alpha(1G), T-type, IC(50) = 50 nM) without affecting the voltage dependence of inactivation. To enable further structural and functional studies, synthetic ProTx-II was made; it adopts the same structure and has the same functional properties as the native peptide. Synthetic ProTx-I was also made and exhibits the same potency as the native peptide. Synthetic ProTx-I, but not ProTx-II, also inhibits K(V) 2.1 channels with 10-fold less potency than its potency on Na(V) channels. These peptides represent novel tools for exploring the gating mechanisms of several Na(V) and Ca(V) channels.
authors.affiliation: Department of Ion Channels, Merck Research Laboratories, Rahway, New Jersey, USA.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Middleton
authors.forename: Vivien A
authors.initials: VA
authors.lastname: Warren
authors.forename: Richard L
authors.initials: RL
authors.lastname: Kraus
authors.forename: Jeremy C
authors.initials: JC
authors.lastname: Hwang
authors.forename: Chou J
authors.initials: CJ
authors.lastname: Liu
authors.forename: Ge
authors.initials: G
authors.lastname: Dai
authors.forename: Richard M
authors.initials: RM
authors.lastname: Brochu
authors.forename: Martin G
authors.initials: MG
authors.lastname: Kohler
authors.forename: Ying-Duo
authors.initials: YD
authors.lastname: Gao
authors.forename: Victor M
authors.initials: VM
authors.lastname: Garsky
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Bogusky
authors.forename: John T
authors.initials: JT
authors.lastname: Mehl
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Cohen
authors.forename: McHardy M
authors.initials: MM
authors.lastname: Smith
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002121:Calcium Channel Blockers / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D002460:Cell Line; D004220:Disulfides / Q000737:chemistry; D004594:Electrophysiology; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D026902:Potassium Channel Blockers / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D026941:Sodium Channel Blockers / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D015222:Sodium Channels / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013111:Spider Venoms / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*
chemical_list: D002121:Calcium Channel Blockers; D004220:Disulfides; D010455:Peptides; D026902:Potassium Channel Blockers; C470625:ProTx-I peptide; C470626:ProTx-II peptide; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D013111:Spider Venoms