Molecular characterization of renal calcium channel beta-subunit transcripts.
An apical, hormone-regulated, calcium entry channel in the distal convoluted tubule and/or connecting tubule (DCT/CNT) is thought to play an important role in controlling renal calcium excretion. We previously identified a gene transcript encoding the pore-forming alpha 1-subunit of a calcium channel (alpha 1A, or CaCh4) which may be a candidate for such a molecule. The properties of voltage-dependent calcium channels are known to be modulated by their beta-subunits. To identify the accessory beta-subunit of DCT/CNT calcium channels, degenerate primers based on published beta-subunit sequences were used to amplify rat kidney cDNA by the polymerase chain reaction (PCR), and the products were subcloned and sequenced. Alternatively spliced transcripts of three beta-subunit genes (beta 2, beta 3, and beta 4) were identified. Northern blot analysis indicated that beta 4-subunit is preferentially expressed in kidney cortex. Transcripts of all three beta-subunit genes were detected by PCR in microdissected nephron segments, but only beta 4-subunit was found in DCT/CNT. As the beta 4- and alpha 1A-subunits colocalize to the DCT/CNT, we hypothesize that they may be constituent subunits of a renal calcium channel regulated by a hormone(s).
Yu
A S
AS
Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115.
Boim
M
M
Hebert
S C
SC
Castellano
A
A
Perez-Reyes
E
E
Lytton
J
J
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015220:Calcium Channels / Q000737:chemistry / Q000235:genetics*; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D015870:Gene Expression; D007668:Kidney / Q000378:metabolism*; D007684:Kidney Tubules / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D009399:Nephrons / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014018:Tissue Distribution; D014158:Transcription, Genetic
D015220:Calcium Channels; D017931:DNA Primers; D018076:DNA, Complementary; D012333:RNA, Messenger