A Calcium-activated Cation Current by an Alternatively Spliced Form of Trp3 in the Heart

• Published in: The Journal of biological chemistry Vol. 275; no. 50; pp. 39055 - 39060
• Main Authors: Ohki, Gaku, Miyoshi, Taku, Murata, Mitsunobu, Ishibashi, Kenichi, Imai, Masashi, Suzuki, Makoto
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.12.2000; American Society for Biochemistry and Molecular Biology
• Subjects: Adenosine Triphosphate - pharmacology; Alternative Splicing; Amino Acid Sequence; Amino Acids - chemistry; Animals; Blotting, Northern; Blotting, Western; Brain - metabolism; Calcium - metabolism; Calcium Channels - genetics; Calcium Channels - metabolism; cation currents; Cations; Chlorides - pharmacology; Cloning, Molecular; DNA, Complementary - metabolism; Enzyme Inhibitors - pharmacology; Gadolinium - pharmacology; Indicators and Reagents - pharmacology; Ionomycin - pharmacology; Ionophores - pharmacology; Meglumine - pharmacology; Molecular Sequence Data; Myocardium - metabolism; Oocytes - metabolism; Patch-Clamp Techniques; Phorbol Esters - pharmacology; Potassium - pharmacology; Rats; Reverse Transcriptase Polymerase Chain Reaction; Ruthenium Red - pharmacology; Sequence Homology, Amino Acid; Sodium - pharmacology; Tetraethylammonium - pharmacology; Thapsigargin - pharmacology; Tissue Distribution; Trp3 protein; TRPC Cation Channels; Xenopus
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M003606200

To investigate a cDNA encoding cation current, we isolated an alternatively spliced form of a rat Trp3, designated Trp3sv. Trp3sv encodes 736 amino acids with a unique N terminus and six transmembrane segments. Expression of the cRNA inXenopus oocytes was successfully performed. The cation selective current appeared after the addition of ionomycin or induced by prolonged depolarization but not by hyperpolarization. This induction was not observed by a treatment with thapsigargin, phorbol ester, or ATP. Na+, K+, tetraethylammonium, and divalent cations were permeable, while N-methylglucamine and chloride were nominally impermeable ions. The currents were not inhibited by flufenamate ruthenium red but nonspecifically by 2 mm Gd3+. Northern as well as Western blot suggested lower levels of the expression observed in some organs, while reverse transcriptase-polymerase chain reaction suggested that it widely spread among various organs. Therefore, we may conclude that N-terminal spliced valiant of Trp3, Trp3sv, encodes a calcium-activated cation channel in various organs.