Interaction of rabies virus glycoprotein fragments with the nicotinic acetylcholine receptor

Abstract

The rabies virus glycoprotein (RVG) interacts with Torpedo and muscle nicotinic acetylcholine receptors (nAChR). The field of Ligand Gated Ion Channels, such as the nicotinic receptors, has benefited greatly over the last decade due to the discovery of non-membrane bound Acetylcholine Binding Proteins (AChBP). Since nicotinic acetylcholine receptors and the ACHBP share significant sequence and structural homology in the neurotoxin binding domain, the AChBP could provide a useful model for studying the molecular basis of the RVG/nAChR interaction. In this study we investigated the interaction between RVG neurotoxin like peptide fragments and the AChBP. Surface Plasmon resonance (SPR) was used to assess binding kinetics to the AChPB. Electrophysiology experiments were used to compare these results to interactions between these RVG fragments and human nicotinic acetylcholine receptor subtypes. RVG fragments were shown to bind with micromolar affinity to the Lymnaea AChBP. SPR permits determination of on and off rates for binding of all 6 fragments. Our data show slow on rates (ka= 100-300 1/M•s) with off rates (kd = 0.01-0.004 1/ M•s) corresponding to binding with a dissociate rate (Kd of 25.4-60.3 micromolar). Voltage clamp electrophysiology data obtained using Xenopus oocytes shows similar Ki values for inhibition of acetylcholine induced responses on alpha4/beta2 nAChR.