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The effect of overexpression of auxiliary Ca 2+ channel subunits on native Ca 2+ channel currents in undifferentiated mammalian NG108–15 cells
Author(s) -
Wyatt Christopher N.,
Page Karen M.,
Berrow Nicholas S.,
Brice Nicola L.,
Dolphin Annette C.
Publication year - 1998
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1998.347bk.x
Subject(s) - protein subunit , depolarization , transfection , r type calcium channel , endogeny , voltage dependent calcium channel , calcium channel , microbiology and biotechnology , chemistry , biophysics , n type calcium channel , heterologous expression , biology , hek 293 cells , calcium , t type calcium channel , biochemistry , recombinant dna , receptor , gene , organic chemistry
1 High voltage activated (HVA) Ca 2+ channels are composed of a pore‐forming α1 subunit and the accessory β and α2‐δ subunits. However, the subunit composition of low voltage activated (LVA), or T‐type, Ca 2+ channels has yet to be elucidated. We have examined whether native calcium channels in NG108–15 mouse neuroblastoma × rat glioma hybrid cells, which express predominantly LVA currents when undifferentiated, are modulated by overexpression of accessory calcium channel subunits. 2 Endogenous α1A, B, C, D and E, and low levels of β and α2‐δ subunit protein were demonstrated in undifferentiated NG108–15 cells. 3 The α2‐δ, β2a or β1b accessory subunits were overexpressed by transfection of the cDNAs into these cells, and the effect examined on the endogenous Ca 2+ channel currents. Heterologous expression, particularly of α2‐δ but also of β2a subunits clearly affected the profile of these currents. Both subunits induced a sustained component in the currents evoked by depolarizing voltages above −30 mV, and α2‐δ additionally caused a depolarization in the voltage dependence of current activation, suggesting that it also affected the native T‐type currents. In contrast, β1b overexpression had no effect on the endogenous Ca 2+ currents, despite immunocytochemical evidence for its expression in the transfected cells. 4 These results suggest that in NG108–15 cells, overexpression of the Ca 2+ channel accessory subunits α2‐δ and β2a induce a sustained component of HVA current, and α2‐δ also influences the voltage dependence of activation of the LVA current. It is possible that native T‐type α1 subunits are not associated with β subunits.