Cloning of a functional splice variant of L-type calcium channel beta 2 subunit from rat heart.
L-type Ca(2+) channels are heteromultimeric and finely tuned by auxiliary subunits in different tissues and regions. Among auxiliary subunits, beta subunit has been shown to play important roles in many functional aspects of Ca(2+) channel. Rat heart was reported to specifically express beta(2a) subunit. However, the slow inactivation rates of Ca(2+) currents recorded from recombinant Ca(2+) channels with the beta(2a) subunit, and the reported inability to detect beta(2a) subunit in rabbit heart by reverse transcription-PCR analysis raise the possibility of the existence of other beta subunits. We cloned a splice variant of beta(2) subunit from rat heart, using rapid amplification of cDNA 5' ends. The splice variant is highly similar to human beta(2c) subunit that was cloned from human ventricle. Northern blot analysis detected the rat beta(2c) subunit abundantly in rat heart and brain. The deduced amino acid sequence of the beta(2c) subunit was different from that of the beta(2a) subunit only in the N-terminal region. When the beta(2c) subunit was expressed along with alpha(1c) and alpha(2)delta subunits in baby hamster kidney cells, the inactivation rates were comparable with those from native cardiac myocytes, although those with the beta(2a) subunit were slow. Taken together, these observations suggest that the beta(2c) subunit is a functional beta(2) subunit expressed in heart and that the short N-terminal region plays a major role in modifying inactivation kinetics.
Yamada
Y
Y
Department of Cellular Physiology and Signal Transduction, Sapporo Medical University School of Medicine, Sapporo 060-8556, Japan.
Nagashima
M
M
Tsutsuura
M
M
Kobayashi
T
T
Seki
S
S
Makita
N
N
Horio
Y
Y
Tohse
N
N
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D001921:Brain / Q000378:metabolism; D019556:COS Cells; D015220:Calcium Channels / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000235:genetics* / Q000378:metabolism*; D002478:Cells, Cultured; D003001:Cloning, Molecular; D006224:Cricetinae; D018076:DNA, Complementary / Q000378:metabolism; D004594:Electrophysiology; D006801:Humans; D007700:Kinetics; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism*; D016366:Open Reading Frames; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid
C107597:CACNB2 protein, human; C491527:Cacnb2 protein, rat; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D018076:DNA, Complementary; D011994:Recombinant Proteins; D012313:RNA