A New Conotoxin Affecting Sodium Current Inactivation Interacts with the δ-Conotoxin Receptor Site

Michael Fainzilber,Johannes C Lodder,Karel S Kits,Ora Kofman,Ilya Vinnitsky,Jurphaas Van Rietschoten,Eliahu Zlotkin,Dalia Gordon

doi:10.1074/jbc.270.3.1123

Michael Fainzilber, Johannes C Lodder + Show 6 more

Open Access

https://doi.org/10.1074/jbc.270.3.1123

Copy DOI

Abstract

We describe a new peptide conotoxin affecting sodium current inactivation, that competes on binding with delta-conotoxin TxVIA (delta TxVIA). The amino acid sequence of the new toxin, designated conotoxin NgVIA (NgVIA), is SKCFSOGTFCGIKOGLCCSVRCFSLFCISFE (where O is trans-4-hydroxyproline). The primary structure of NgVIA has an identical cysteine framework and similar hydrophobicity as delta TxVIA but differs in its net charge. NgVIA competes with delta TxVIA on binding to rat brain synaptosomes and molluscan central nervous system and strongly inhibits sodium current inactivation in snail neurons, as does delta TxVIA. In contrast to delta TxVIA, NgVIA is a potent paralytic toxin in vertebrate systems, its binding appears to be voltage-dependent, and it synergically increases veratridine-induced sodium influx to rat brain synaptosomes. delta TxVIA acts as a partial antagonist to NgVIA in rat brain in vivo. NgVIA appears to act via a receptor site distinct from that of delta TxVIA but similar to that of Conus striatus toxin. This new toxin provides a lead for structure-function relationship studies in the delta-conotoxins and will enable analysis of the functional significance of this complex of receptor sites in gating mechanisms of sodium channels.

Highlights

From the Wepartment of Cell and Animal Biology, Silberman Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel, the §Graduate School Neurosciences Amsterdam, Research Institute of Neuroscience, Faculty of Biology, Vrije Unioersiteit, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands, the IlBeer-Sheva Mental Health Center and Department of Behavioral Sciences, Ben-Gurion University, Beer-Sheva, Israel, and the **Faculty of Medicine, Department of Biochemistry, University of Aix-Marseille II, Bd
We describe a new peptide conotoxin affecting sodium current inactivation, that competes on binding with o-conotoxin TxVIA (OTxVIA)
NgVIA competes with OTxVIA on binding to rat brain synaptosomes and molluscan central nervous system and strongly inhibits sodium current inactivation in snail neurons, as does 0TxVIA

Summary

Introduction

NgVIA appears to act via a receptor site distinct from that of OTxVIAbut similar to that of Conus striatus toxin This new toxin provides a lead for structure-function relationship studies in the o-conotoxins and will enable analysis of the functional significance of this complex of receptor sites in gating mechanisms of sodium channels. Voltage-dependent sodium channels are integral plasma membrane proteins responsible for the rapidly rising phase of action potentials in most excitable tissues and as such are targeted by many neurotoxins These toxins occupy at least six identified (receptor sites 1-5 (Catterall, 1986), and receptor site 6 (Fainzilber et al, 1994) and two unidentified (CsTx1 and GPT (Catterall, 1992)) receptor sites on the rat brain sodium channel and have been used as tools for functional mapping and characterization of the channel (Catterall, 1986, 1992; Fainzilber et al, 1994).

Objectives

Results

Conclusion