Dominant-negative synthesis suppression of voltage-gated calcium channel Cav2.2 induced by truncated constructs.

Raghib, Ayesha, Bertaso, Federica, Davies, Anthony, Page, Karen M., Meir, Alon, Bogdanov, Yuri and Dolphin, Annette C. (2001) Dominant-negative synthesis suppression of voltage-gated calcium channel Cav2.2 induced by truncated constructs. Journal of Neuroscience, 21 (11), 8495-8504. (doi:10.1523/jneurosci.21-21-08495.2001).

Abstract

Voltage-gated calcium channel α1 subunits consist of four domains (I–IV), each with six transmembrane segments. A number of truncated isoforms have been identified to occur as a result of alternative splicing or mutation. We have examined the functional consequences for expression of full-length Cav2.2 (α1B) of its coexpression with truncated constructs of Cav2.2. Domains I-II or domains III-IV, when expressed individually, together with the accessory subunits β1b and α2δ-1, did not form functional channels. When they were coexpressed, low-density whole-cell currents and functional channels with properties similar to wild-type channels were observed. However, when domain I-II, domain III-IV, or domain I alone were coexpressed with full-length Cav2.2, they markedly suppressed its functional expression, although at the single channel level, when channels were recorded, there were no differences in their biophysical properties. Furthermore, when it was coexpressed with either domain I-II or domain I, the fluorescence of green fluorescent protein (GFP)–Cav2.2 and expression of Cav2.2 protein was almost abolished. Suppression does not involve sequestration of the Cavβ subunit, because loss of GFP–Cav2.2 expression also occurred in the absence of β subunit, and the effect of domain I-II or domain I could not be mimicked by the cytoplasmic I-II loop of Cav2.2. It requires transmembrane segments, because the isolated Cav2.2 N terminus did not have any effect. Our results indicate that the mechanism of suppression of Cav2.2 by truncated constructs containing domain I involves inhibition of channel synthesis, which may represent a role of endogenously expressed truncated Cav isoforms.

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Contributors

Author: Yuri Bogdanov

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