Title

Biophysical properties of Nav1.8/Nav1.2 chimeras and inhibition by μo-conotoxin MrVIB

RIS ID

105248

Publication Details

Knapp, O., Nevin, S. T., Yasuda, T., Lawrence, N., Lewis, R. J. & Adams, D. J. (2012). Biophysical properties of Nav1.8/Nav1.2 chimeras and inhibition by μo-conotoxin MrVIB. British Journal of Pharmacology, 166 (7), 2148-2160.

Abstract

BACKGROUND AND PURPOSE Voltage-gated sodium channels are expressed primarily in excitable cells and play a pivotal role in the initiation and propagation of action potentials. Nine subtypes of the pore-forming α-subunit have been identified, each with a distinct tissue distribution, biophysical properties and sensitivity to tetrodotoxin (TTX). Nav1.8, a TTX-resistant (TTX-R) subtype, is selectively expressed in sensory neurons and plays a pathophysiological role in neuropathic pain. In comparison with TTX-sensitive (TTX-S) Navα-subtypes in neurons, Nav1.8 is most strongly inhibited by the µO-conotoxin MrVIB from Conus marmoreus. To determine which domain confers Nav1.8 α-subunit its biophysical properties and MrVIB binding, we constructed various chimeric channels incorporating sequence from Nav1.8 and the TTX-S Nav1.2 using a domain exchange strategy. EXPERIMENTAL APPROACH Wild-type and chimeric Nav channels were expressed in Xenopus oocytes, and depolarization-activated Na+ currents were recorded using the two-electrode voltage clamp technique. KEY RESULTS MrVIB (1 µM) reduced Nav1.2 current amplitude to 69 ± 12%, whereas Nav1.8 current was reduced to 31 ± 3%, confirming that MrVIB has a binding preference for Nav1.8. A similar reduction in Na+ current amplitude was observed when MrVIB was applied to chimeras containing the region extending from S6 segment of domain I through the S5-S6 linker of domain II of Nav1.8. In contrast, MrVIB had only a small effect on Na+ current for chimeras containing the corresponding region of Nav1.2. CONCLUSIONS AND IMPLICATIONS Taken together, these results suggest that domain II of Nav1.8 is an important determinant of MrVIB affinity, highlighting a region of the α-subunit that may allow further nociceptor-specific ligand targeting.

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Link to publisher version (DOI)

http://dx.doi.org/10.1111/j.1476-5381.2012.01955.x