Molecular cloning and functional expression of Ca_v3.1c, a T‐type calcium channel from human brain

Abstract

Low voltage-activated T-type calcium channels are encoded by a family of at least three genes, with additional diversity created by alternative splicing. This study describes the cloning of the human brain K K1G, which is a novel isoform, Ca v 3.1c. Comparison of this sequence to genomic sequences deposited in the GenBank allowed us to identify the intron/exon boundaries of the human CACNA1G gene. A full-length cDNA was constructed, then used to generate a stably-transfected mammalian cell line. The resulting currents were analyzed for their voltage-and time-dependent properties. These properties identify this gene as encoding a T-type Ca 2+ channel. z 2000 Federation of European Biochemical Societies.

Identification of R(−)‐isomer of efonidipine as a selective blocker of T‐type Ca2+ channels

“…Although the cause of the shift was not clarified, the differences in recording methods, that is, double microelectrodes vs whole cell patch, and 5 vs 40 mM external Ba 2 þ , partially contributed to the different voltage dependence of channel inactivation. Such altered voltage dependences of the a 1G channel in different expression and recording systems have been seen in previous reports (PerezReyes et al, 1998;Lee et al, 1999;Cribbs et al, 2000;Marksteiner et al, 2001).…”

“…In all, 33 nucleotide changes in the sequences were shown not to alter the coding amino-acid residues: C (9), G (15), G (816), T (927), G (951), C (954), C (1059), C (1542), G (1902), T (1908), G (1926), C (1929), A (2802), C (2805), C (2823), C (2829), C (3370), G (3819), G (3825), T (3828), C(3843), G (3846), T (4926), G (4929), C (4938), C (4947), G (5772), C (5778), G (5781), C (5793), C (5796), T (6054) and A (6846) were T, T, A, C, T, A, T, T, C, C, A, G, G, T, G, T, T, A, A, C, T, T, C, C, T, T, A, G, A, T, T, C and G in our clones, respectively. Thus, the insert of this clone contained a cDNA sequence encoding a splice variant of a 1G , a 1G-bce (Cribbs et al, 2000;Monteil et al, 2000).…”

T-type voltage-activated calcium channel Cav3.1, but not Cav3.2, is involved in the inhibition of proliferation and apoptosis in MCF-7 human breast cancer cells

“…These two isoforms possess comparable biophysical properties and are often co-expressed in various tissues. The two T-type channels open near the resting membrane potential, inactivate rapidly, exhibit slow deactivation, and have small unitary conductances (4,5,8). However, both isoforms reportedly demonstrate distinct kinetics of Ca 2+ entry in response to different action potential frequencies and duration (21).…”

“…However, both isoforms reportedly demonstrate distinct kinetics of Ca 2+ entry in response to different action potential frequencies and duration (21). Furthermore, while these subtypes show high sequence identity across their transmembrane-spanning regions, the amino and carboxy termini and intracellular loops exhibit a considerable divergence, making these regions possible targets for differential regulation (4,5). These findings suggest that these two isoforms may serve different functional roles in various tissues.…”

“…These properties may be particularly important in controlling intracellular Ca 2+ levels (3), especially for non-excitable tumor cells. At present, three isoforms of T-type Ca 2+ channel α1 subunits are known: Ca v 3.1 (α1G), Ca v 3.2 (α1H) and Ca v 3.3 (α1I) (4)(5)(6)(7)(8). Among them, the Ca v 3.1 and Ca v 3.2 channels resemble each other electrophysiologically.…”