Molecular characterization of a neuronal low-voltage-activated T-type calcium channel.
The molecular diversity of voltage-activated calcium channels was established by studies showing that channels could be distinguished by their voltage-dependence, deactivation and single-channel conductance. Low-voltage-activated channels are called 'T' type because their currents are both transient (owing to fast inactivation) and tiny (owing to small conductance). T-type channels are thought to be involved in pacemaker activity, low-threshold calcium spikes, neuronal oscillations and resonance, and rebound burst firing. Here we report the identification of a neuronal T-type channel. Our cloning strategy began with an analysis of Genbank sequences defined as sharing homology with calcium channels. We sequenced an expressed sequence tag (EST), then used it to clone a full-length complementary DNA from rat brain. Northern blot analysis indicated that this gene is expressed predominantly in brain, in particular the amygdala, cerebellum and thalamus. We mapped the human gene to chromosome 17q22, and the mouse gene to chromosome 11. Functional expression of the channel was measured in Xenopus oocytes. Based on the channel's distinctive voltage dependence, slow deactivation kinetics, and 7.5-pS single-channel conductance, we conclude that this channel is a low-voltage-activated T-type calcium channel.
Perez-Reyes
E
E
Department of Physiology, and Cardiovascular Institute, Loyola University Medical Center, Maywood, Illinois 60153, USA. eperez@luc.edu
Cribbs
L L
LL
Daud
A
A
Lacerda
A E
AE
Barclay
J
J
Williamson
M P
MP
Fox
M
M
Rees
M
M
Lee
J H
JH
D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D015220:Calcium Channels / Q000235:genetics* / Q000378:metabolism; D020746:Calcium Channels, L-Type; D002478:Cells, Cultured; D002874:Chromosome Mapping; D002886:Chromosomes, Human, Pair 17; D003001:Cloning, Molecular; D018076:DNA, Complementary; D016208:Databases, Factual; D004594:Electrophysiology; D006801:Humans; D015640:Ion Channel Gating; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism; D009154:Mutation; D051381:Rats; D016415:Sequence Alignment; D014981:Xenopus
D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D018076:DNA, Complementary