Coexpression of cloned alpha(1B), beta(2a), and alpha(2)/delta subunits produces non-inactivating calcium currents similar to those found in bovine chromaffin cells

• Published in: The Journal of neuroscience Vol. 20; no. 5; p. 1685
• Main Authors: Cahill, A L, Hurley, J H, Fox, A P
• Format: Journal Article
• Language: English
• Published: United States 01.03.2000
• Subjects: Alternative Splicing - physiology; Animals; Calcium - metabolism; Calcium Channel Blockers - pharmacology; Calcium Channels, N-Type - chemistry; Calcium Channels, N-Type - genetics; Calcium Channels, N-Type - metabolism; Cattle; Cells, Cultured; Chromaffin Cells - chemistry; Chromaffin Cells - physiology; Cloning, Molecular; DNA, Complementary; Electrophysiology; Female; Humans; Ion Channel Gating - drug effects; Ion Channel Gating - genetics; Kidney - cytology; Molecular Sequence Data; omega-Conotoxin GVIA - pharmacology; Oocytes - physiology; Rats; Sequence Homology, Amino Acid; Xenopus laevis
• ISSN: 1529-2401

Chromaffin cells express N-type calcium channels identified on the basis of their high sensitivity to block by omega-conotoxin GVIA (omega-CgTx GVIA). In contrast to neuronal N-type calcium currents that inactivate during long depolarizations and that require negative holding potentials to remove inactivation, many chromaffin cells exhibit N-type calcium channel currents that show little inactivation during maintained depolarizations and that exhibit no decrease in channel availability at depolarized holding potentials. N-type calcium channels are thought to be produced by combination of the pore-forming alpha(1B) subunit and accessory beta and alpha(2)/delta subunits. To examine the molecular composition of the non-inactivating N-type calcium channel, we cloned the alpha(1B) and accessory beta (beta(1b), beta(1c,) beta(2a), beta(2b), and beta(3a)) subunits found in bovine chromaffin cells. Expression of the subunits in either Xenopus oocytes or human embryonic kidney 293 cells produced high-threshold calcium currents that were blocked by omega-CgTx GVIA. Coexpression of bovine alpha(1B) with beta(1b), beta(1c), beta(2b), or beta(3a) produced currents that were holding potential dependent. In contrast, coexpression of bovine alpha(1B) with beta(2a) produced holding potential-independent calcium currents that closely mimicked native non-inactivating currents, suggesting that non-inactivating N-type channels consist of bovine alpha(1B), alpha(2)/delta, and beta(2a).