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Structure and Functional Characterization of a Novel Human Low‐Voltage Activated Calcium Channel
Author(s) -
Williams Mark E.,
Washburn Mark S.,
Hans Michael,
Urrutia Arturo,
Brust Paul F.,
Prodanovich Patricia,
Harpold Michael M.,
Stauderman Kenneth A.
Publication year - 1999
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1999.0720791.x
Subject(s) - xenopus , mibefradil , voltage dependent calcium channel , hek 293 cells , r type calcium channel , biology , voltage gated ion channel , protein subunit , microbiology and biotechnology , ion channel , t type calcium channel , biophysics , chemistry , medicine , endocrinology , calcium , receptor , biochemistry , gene
: We have isolated and characterized overlapping cDNAsencoding a novel, voltage‐gated Ca 2+ channel α 1 subunit, α 1H , from a human medullary thyroid carcinoma cellline. The α 1H subunit is structurally similar to previouslydescribed α 1 subunits. Northern blot analysis indicates thatα 1H mRNA is expressed throughout the brain, primarily in theamygdala, caudate nucleus, and putamen, as well as in several nonneuronaltissues, with relatively high levels in the liver, kidney, and heart.Ba 2+ currents recorded from human embryonic kidney 293 cellstransiently expressing α 1H activated at relativelyhyperpolarized potentials (‐50 mV), rapidly inactivated (τ = 17 ms), andslowly deactivated. Similar results were observed in Xenopus oocytesexpressing α 1H . Singlechannel measurements in human embryonickidney 293 cells revealed a single‐channel conductance of ~9 pS. Thesechannels are blocked by Ni 2+ (IC 50 = 6.6 μ M )and the T‐type channel antagonists mibefradil (~50% block at 1 μ M )and amiloride (IC 50 = 167 μ M ). Thus,α 1H ‐containing channels exhibit biophysical andpharmacological properties characteristic of low voltage‐activated, or T‐type,Ca 2+ channels.