Impaired cardiac contractility in mice lacking both the AE3 Cl -/HCO3- exchanger and the NKCC1 Na +-K+-2Cl- cotransporter: Effects on Ca 2+ handling and protein phosphatases

Vikram Prasad, Ilona Bodi, Jamie W. Meyer, Yigang Wang, Muhammad Ashraf, Sandra J. Engle, Thomas Doetschman, Karena Sisco, Michelle L. Nieman, Marian L. Miller, John N. Lorenz, Gary E. Shull

Research output: Contribution to journalArticle

23 Scopus citations

Abstract

To analyze the cardiac functions of AE3, we disrupted its gene (Slc4a3) in mice. Cl-/HCO3- exchange coupled with Na +-dependent acid extrusion can mediate pH-neutral Na+ uptake, potentially affecting Ca2+ handling via effects on Na +/Ca2+ exchange. AE3 null mice appeared normal, however, and AE3 ablation had no effect on ischemia-reperfusion injury in isolated hearts or cardiac performance in vivo. The NKCC1 Na+-K+-2Cl - cotransporter also mediates Na+ uptake, and loss of NKCC1 alone does not impair contractility. To further stress the AE3-deficient myocardium, we combined the AE3 and NKCC1 knock-outs. Double knock-outs had impaired contraction and relaxation both in vivo and in isolated ventricular myocytes. Ca2+ transients revealed an apparent increase in Ca 2+ clearance in double null cells. This was unlikely to result from increased Ca2+ sequestration, since the ratio of phosphorylated phospholamban to total phospholamban was sharply reduced in all three mutant hearts. Instead, Na+/Ca2+ exchanger activity was found to be enhanced in double null cells. Systolic Ca2+ was unaltered, however, suggesting more direct effects on the contractile apparatus of double null myocytes. Expression of the catalytic subunit of protein phosphatase 1 was increased in all mutant hearts. There was also a dramatic reversal, between single null and double null hearts, in the carboxymethylation and localization to the myofibrillar fraction, of the catalytic subunit of protein phosphatase 2A, which corresponded to the loss of normal contractility in double null hearts. These data show that AE3 and NKCC1 affect Ca2+ handling, PLN regulation, and expression and localization of major cardiac phosphatases and that their combined loss impairs cardiac function.

Original languageEnglish (US)
Pages (from-to)31303-31314
Number of pages12
JournalJournal of Biological Chemistry
Volume283
Issue number46
DOIs
StatePublished - Nov 14 2008
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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    Prasad, V., Bodi, I., Meyer, J. W., Wang, Y., Ashraf, M., Engle, S. J., Doetschman, T., Sisco, K., Nieman, M. L., Miller, M. L., Lorenz, J. N., & Shull, G. E. (2008). Impaired cardiac contractility in mice lacking both the AE3 Cl -/HCO3- exchanger and the NKCC1 Na +-K+-2Cl- cotransporter: Effects on Ca 2+ handling and protein phosphatases. Journal of Biological Chemistry, 283(46), 31303-31314. https://doi.org/10.1074/jbc.M803706200