The α₂δ auxiliary subunit reduces affinity of ω-conotoxins for recombinant N-type (Ca_v2.2) calcium channels

Authors

Jorgen Mould, University of Queensland
Takahiro Yasuda, RMIT University
Christina I. Schroeder, University of Queensland
Aaron M. Beedle, University of Calgary
Clinton J. Doering, University of Calgary
Gerald W. Zamponi, University of Calgary
David J. Adams, University of QueenslandFollow
Richard J. Lewis, University of QueenslandFollow

RIS ID

105746

Publication Details

Mould, J., Yasuda, T., Schroeder, C. I., Beedle, A. M., Doering, C. J., Zamponi, G. W., Adams, D. J. & Lewis, R. J. (2004). The α₂δ auxiliary subunit reduces affinity of ω-conotoxins for recombinant N-type (Ca_v2.2) calcium channels. Journal of Biological Chemistry, 279 (33), 34705-34714.

Abstract

The ω-conotoxins from fish-hunting cone snails are potent inhibitors of voltage-gated calcium channels. The ω-conotoxins MVIIA and CVID are selective N-type calcium channel inhibitors with potential in the treatment of chronic pain. The β and α 2δ-1 auxiliary subunits influence the expression and characteristics of the α 1B subunit of N-type channels and are differentially regulated in disease states, including pain. In this study, we examined the influence of these auxiliary subunits on the ability of the ω-conotoxins GVIA, MVIIA, CVID and analogues to inhibit peripheral and central forms of the rat N-type channels. Although the β3 subunit had little influence on the on- and off-rates of ω-conotoxins, co-expression of α 2δ with α 1B significantly reduced on-rates and equilibrium inhibition at both the central and peripheral isoforms of the N-type channels. The α 2δ also enhanced the selectivity of MVIIA, but not CVID, for the central isoform. Similar but less pronounced trends were also observed for N-type channels expressed in human embryonic kidney cells. The influence of α 2δ was not affected by oocyte deglycosylation. The extent of recovery from the ω-conotoxin block was least for GVIA, intermediate for MVIIA, and almost complete for CVID. Application of a hyperpolarizing holding potential (-120 mV) did not significantly enhance the extent of CVID recovery. Interestingly, [R10K]MVIIA and [O10K]GVIA had greater recovery from the block, whereas [K10R]CVID had reduced recovery from the block, indicating that position 10 had an important influence on the extent of ω-conotoxin reversibility. Recovery from CVID block was reduced in the presence of α 2δ in human embryonic kidney cells and in oocytes expressing α 1B-b These results may have implications for the antinociceptive properties of ω-conotosins, given that the α 2δ subunit is up-regulated in certain pain states.