Molecular cloning and characterization of the human voltage-gated calcium channel alpha(2)delta-4 subunit.
The voltage-gated calcium channel is composed of a pore-forming alpha(1) subunit and several regulatory subunits: alpha(2)delta, beta, and gamma. We report here the identification of a novel alpha(2)delta subunit, alpha(2)delta-4, from the expressed sequence tag database followed by its cloning and characterization. The novel alpha(2)delta-4 subunit gene contains 39 exons spanning about 130 kilobases and is co-localized with the CHCNA1C gene (alpha(1C) subunit) on human chromosome 12p13.3. Alternative splicing of the alpha(2)delta-4 gene gives rise to four potential variants, a through d. The open reading frame of human alpha(2)delta-4a is composed of 3363 base pairs encoding a protein with 1120 residues and a calculated molecular mass of 126 kDa. The alpha(2)delta-4a subunit shares 30, 32, and 61% identity with the human calcium channel alpha(2)delta-1, alpha(2)delta-2, and alpha(2)delta-3 subunits, respectively. Primary sequence comparison suggests that alpha(2)delta-4 lacks the gabapentin binding motifs characterized for alpha(2)delta-1 and alpha(2)delta-2; this was confirmed by a [(3)H]gabapentin-binding assay. In human embryonic kidney 293 cells, the alpha(2)delta-4 subunit associated with Ca(V)1.2 and beta(3) subunits and significantly increased Ca(V)1.2/beta(3)-mediated Ca(2+) influx. Immunohistochemical study revealed that the alpha(2)delta-4 subunit has limited distribution in special cell types of the pituitary, adrenal gland, colon, and fetal liver. Whether the alpha(2)delta-4 subunit plays a distinct physiological role in select endocrine tissues remains to be demonstrated.
Qin
Ning
N
Johnson & Johnson Pharmaceutical Research and Development, Spring House, Pennsylvania 19477-0776, USA. nqin@prius.jnj.com
Yagel
Susan
S
Momplaisir
Mary-Lou
ML
Codd
Ellen E
EE
D'Andrea
Michael R
MR
D000085:Acetates / Q000494:pharmacology; D017398:Alternative Splicing; D000588:Amines; D000595:Amino Acid Sequence; D001483:Base Sequence; D001692:Biological Transport; D015152:Blotting, Northern; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000235:genetics* / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000378:metabolism; D002478:Cells, Cultured; D002874:Chromosome Mapping; D002881:Chromosomes, Human, Pair 12; D003001:Cloning, Molecular; D003509:Cyclohexanecarboxylic Acids; D005091:Exons; D000077206:Gabapentin; D006801:Humans; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D021122:Protein Subunits; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D005680:gamma-Aminobutyric Acid
D000085:Acetates; D000588:Amines; C498838:CACNA2D4 protein, human; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D003509:Cyclohexanecarboxylic Acids; C419385:L-type calcium channel alpha(1C); D021122:Protein Subunits; D005680:gamma-Aminobutyric Acid; D000077206:Gabapentin; D002118:Calcium