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The α 1I T‐type calcium channel exhibits faster gating properties when overexpressed in neuroblastoma/glioma NG 108‐15 cells
Author(s) -
Chemin Jean,
Monteil Arnaud,
Dubel Steve,
Nargeot Joël,
Lory Philippe
Publication year - 2001
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.0953-816x.2001.01796.x
Subject(s) - hek 293 cells , xenopus , gene isoform , protein subunit , alternative splicing , microbiology and biotechnology , gating , biology , voltage dependent calcium channel , cell culture , chemistry , biophysics , biochemistry , calcium , genetics , gene , organic chemistry
The recently cloned T‐type calcium channel α 1I (Ca v 3.3) displays atypically slow kinetics when compared to native T‐channels. Possible explanations might involve alternative splicing of the α 1I subunit, or the use of expression systems that do not provide a suitable environment (auxiliary subunit, phosphorylation, glycosylation…). In this study, two human α 1I splice variants, the α 1I‐a and α 1I‐b isoforms that harbour distinct carboxy‐terminal regions were studied using various expression systems. As the localization of the α 1I subunit is primarily restricted to neuronal tissues, its functional expression was conducted in the neuroblastoma/glioma cell line NG 108‐15, and the results compared to those obtained in HEK‐293 cells and Xenopus oocytes. In Xenopus oocytes, both isoforms exhibited very slow current kinetics compared to those obtained in HEK‐293 cells, but the α 1I‐b isoform generated faster currents than the α 1I‐a isoform. Both activation and inactivation kinetics of α 1I currents were significantly faster in NG 108‐15 cells, while deactivating tail currents were two times slower, compared to those obtained in HEK‐293 cells. Moreover, the α 1I‐b isoform showed significantly slower deactivation kinetics both in NG 1080‐15 and in HEK‐293 cells. Altogether, these data emphasize the advantage of combining several expression systems to reveal subtle differences in channel properties and further indicate that the major functional differences between both human α 1I isoforms are related to current kinetics. More importantly, these data suggest that the expression of the α 1I subunit in neuronal cells contributes to the ‘normalization’ of current kinetics to the more classical, fast‐gated T‐type Ca 2+ current.