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Functional differences between cardiac and renal isoforms of the rat Na + ‐Ca 2+ exchanger NCX1 expressed in Xenopus oocytes
Author(s) -
Ruknudin Abdul,
He Suiwen,
Lederer W. J.,
Schulze Dan H.
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.00599.x
Subject(s) - xenopus , gene isoform , sodium calcium exchanger , chemistry , sodium–hydrogen antiporter , microbiology and biotechnology , medicine , calcium , biology , sodium , gene , biochemistry , organic chemistry
1 The transcript of the Na + ‐Ca 2+ exchanger gene NCX1 undergoes alternative splicing to produce tissue‐specific isoforms. The cloned NCX1 isoforms were expressed in Xenopus oocytes and studied using a two‐electrode voltage clamp method to measure Na + ‐Ca 2+ exchanger activity. 2 The cardiac isoform (NCX1.1) expressed in oocytes was less sensitive to depolarizing voltages and to activation by [Ca 2+ ] i than the renal isoform (NCX1.3). 3 The cardiac isoform of NCX1 is more sensitive to activation by protein kinase A (PKA) than the renal isoform which may be explained by preferential phosphorylation. The cardiac isoform of NCX1 is phosphorylated to a greater extent than the renal isoform. 4 The action of PKA phosphorylation which increases the activity of the cardiac isoform of the Na + ‐Ca 2+ exchanger in oocytes was confirmed in adult rat ventricular cardiomyocytes by measuring Na + ‐dependent Ca 2+ flux. 5 We conclude that alternative splicing of NCX1 confers distinct functional characteristics to tissue‐specific isoforms of the Na + ‐Ca 2+ exchanger.