A novel long N-terminal isoform of human L-type Ca2+ channel is up-regulated by protein kinase C.
Human L-type voltage-dependent Ca(2+) channels (alpha(1C), or Ca(v)1.2) are up-regulated by protein kinase C (PKC) in native tissues, but in heterologous systems this modulation is absent. In rat and rabbit, alpha(1C) has two N-terminal (NT) isoforms, long and short, with variable initial segments of 46 and 16 amino acids, respectively. The initial 46 amino acids of the long-NT alpha(1C) are crucial for PKC regulation. However, only a short-NT human alpha(1C) is known. We assumed that a long-NT isoform of human alpha(1C) may exist. By homology screening of human genomic DNA, we identified a stretch (termed exon 1a) highly homologous to rabbit long-NT, separated from the next known exon of alpha(1C) (exon 1b, which encodes the alternative, short-NT) by an approximately 80 kb-long intron. The predicted 46-amino acid protein sequence is highly homologous to rabbit long-NT. Reverse transcriptase PCR showed the presence of exon 1a transcript in human cardiac RNA. Expression of human long-NT alpha(1C) in Xenopus oocytes produced Ca(2+) channel enhanced by a PKC activator, whereas the short-NT alpha(1C) was inhibited. The long-NT isoform may be the Ca(2+) channel enhanced by PKC-activating transmitters in human tissues.
Blumenstein
Yakov
Y
Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Ramat Aviv 69978, Israel.
Kanevsky
Nataly
N
Sahar
Gideon
G
Barzilai
Rachel
R
Ivanina
Tatiana
T
Dascal
Nathan
N
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D020746:Calcium Channels, L-Type / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D017931:DNA Primers; D005786:Gene Expression Regulation; D014644:Genetic Variation; D006801:Humans; D007700:Kinetics; D008168:Lung / Q000378:metabolism; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D020033:Protein Isoforms / Q000737:chemistry* / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D020746:Calcium Channels, L-Type; D017931:DNA Primers; D010446:Peptide Fragments; D020033:Protein Isoforms; D011994:Recombinant Proteins; D011493:Protein Kinase C