Abstract
The properties of the rat brain α1E Ca2+ channel subunit and its modulation by accessory rat brain α2-δ and β1b subunits were studied by transient transfection in a mammalian cell line in order to attempt to reconcile the debate as to whether α1E forms a low-voltage-activated (LVA) or high-voltage-activated (HVA) Ca2+ channel and to examine its pharmacology in detail. α1E alone was capable of forming an ion-conducting pore in COS-7 cells. The properties of heteromultimeric α1E/α2-δ/β1b channels were largely dictated by the presence of the β1b subunit, which increased current density and tended to produce a hyperpolarizing shift in the voltage dependence of activation and inactivation. α1E/α2-δ/β1b channels did not appear to be regulated by Ca2+-induced inactivation. α1E was shown to exhibit a unique pharmacological profile. ω-Agatoxin IVA blocked the current in a dose-dependent manner with an IC50 of approximately 50 nM and a maximum inhibition of about 80%, whilst ω-conotoxin MVIIC was without effect. The 1,4-dihydropyridine (DHP) antagonist nicardipine (1 μM) produced an inhibition of 51 ± 7%, whereas the DHP agonist S-(–)BAY K 8644 was without effect. Our findings suggest a re-evaluation of the classification of the α1E Ca2+ channel subunit; we propose that rat brain α1E forms a novel Ca2+ channel with properties more similar to a subtype of LVA than HVA Ca2+ current.
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Received: 30 August 1996 / Received after revision and accepted: 28 October 1996
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Stephens, G., Page, K., Burley, J. et al. Functional expression of rat brain cloned α1E calcium channels in COS-7 cells. Pfluegers Arch 433, 523–532 (1997). https://doi.org/10.1007/s004240050308
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DOI: https://doi.org/10.1007/s004240050308