Structure and Functional Characterization of a Novel Human Low‐Voltage Activated Calcium Channel

• Published in: Journal of neurochemistry 1999-02, Vol.72 (2), p.791-799
• Main Authors: Williams, Mark E., Washburn, Mark S., Hans, Michael, Urrutia, Arturo, Brust, Paul F., Prodanovich, Patricia, Harpold, Michael M., Stauderman, Kenneth A.
• Format: Article
• Language: English
• Subjects: 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester - pharmacology; Amiloride - pharmacology; Animals; Barium - pharmacology; Benzimidazoles - pharmacology; Biological and medical sciences; Blotting, Northern; Cadmium - pharmacology; Calcium - pharmacokinetics; Calcium Channel Agonists - pharmacology; Calcium Channel Blockers - pharmacology; Calcium Channels - chemistry; Calcium Channels - genetics; Calcium Channels, T-Type; Cell membranes. Ionic channels. Membrane pores; Cell structures and functions; Cells, Cultured; Cloning, Molecular; Diuretics - pharmacology; DNA, Complementary; Electric Stimulation; Electrophysiology; Fundamental and applied biological sciences. Psychology; Human embryonic kidney 293 cells; Humans; Ion Channel Gating - drug effects; Ion Channel Gating - physiology; Kidney - cytology; Kinetics; Membrane Potentials - drug effects; Membrane Potentials - physiology; Mibefradil; Molecular and cellular biology; Molecular Sequence Data; Nickel - pharmacology; Nimodipine - pharmacology; Oocytes - physiology; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; RNA, Messenger - analysis; Sequence Homology, Amino Acid; Tetrahydronaphthalenes - pharmacology; Transcription, Genetic - physiology; T‐type; Verapamil - pharmacology; Voltage‐gated; Xenopus; α1H
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1046/j.1471-4159.1999.0720791.x

: We have isolated and characterized overlapping cDNAs encoding a novel, voltage‐gated Ca2+ channel α1 subunit, α1H, from a human medullary thyroid carcinoma cell line. The α1H subunit is structurally similar to previously described α1 subunits. Northern blot analysis indicates that α1H mRNA is expressed throughout the brain, primarily in the amygdala, caudate nucleus, and putamen, as well as in several nonneuronal tissues, with relatively high levels in the liver, kidney, and heart. Ba2+ currents recorded from human embryonic kidney 293 cells transiently expressing α1H activated at relatively hyperpolarized potentials (‐50 mV), rapidly inactivated (τ = 17 ms), and slowly deactivated. Similar results were observed in Xenopus oocytes expressing α1H. Singlechannel measurements in human embryonic kidney 293 cells revealed a single‐channel conductance of ~9 pS. These channels are blocked by Ni2+ (IC50 = 6.6 μM) and the T‐type channel antagonists mibefradil (~50% block at 1 μM) and amiloride (IC50 = 167 μM). Thus, α1H‐containing channels exhibit biophysical and pharmacological properties characteristic of low voltage‐activated, or T‐type, Ca2+ channels.