Cardiomyocytes from AKAP7 knockout mice respond normally to adrenergic stimulation

Proc Natl Acad Sci U S A. 2012 Oct 16;109(42):17099-104. doi: 10.1073/pnas.1215219109. Epub 2012 Oct 3.

Abstract

Protein kinase A (PKA) is activated during sympathetic stimulation of the heart and phosphorylates key proteins involved in cardiac Ca(2+) handling, including the L-type Ca(2+) channel (Ca(V)1.2) and phospholamban (PLN). This results in acceleration and amplification of the beat-to-beat changes in cytosolic Ca(2+) in cardiomyocytes and, in turn, an increased rate and force of contraction. PKA is held in proximity to its substrates by protein scaffolds called A kinase anchoring proteins (AKAPs). It has been suggested that the short and long isoforms of AKAP7 (also called AKAP15/18) localize PKA in complexes with Ca(V)1.2 and PLN, respectively. We generated an AKAP7 KO mouse in which all isoforms were deleted and tested whether Ca(2+) current, intracellular Ca(2+) concentration, or Ca(2+) reuptake were impaired in isolated adult ventricular cardiomyocytes following stimulation with the β-adrenergic agonist isoproterenol. KO cardiomyocytes responded normally to adrenergic stimulation, as measured by whole-cell patch clamp or a fluorescent intracellular Ca(2+) indicator. Phosphorylation of Ca(V)1.2 and PLN were also unaffected by genetic deletion of AKAP7. Immunoblot and RT-PCR revealed that only the long isoforms of AKAP7 were detectable in ventricular cardiomyocytes. The results indicate that AKAP7 is not required for regulation of Ca(2+) handling in mouse cardiomyocytes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • A Kinase Anchor Proteins / genetics
  • A Kinase Anchor Proteins / metabolism*
  • Adrenergic beta-Agonists / pharmacology*
  • Animals
  • Blotting, Southern
  • Calcium / metabolism*
  • Cyclic AMP-Dependent Protein Kinases / metabolism*
  • DNA Primers / genetics
  • Immunoblotting
  • Immunoprecipitation
  • Isoproterenol / pharmacology*
  • Mice
  • Mice, Knockout
  • Myocardial Contraction / physiology*
  • Myocytes, Cardiac / drug effects*
  • Myocytes, Cardiac / metabolism
  • Patch-Clamp Techniques
  • Phosphorylation
  • Reverse Transcriptase Polymerase Chain Reaction

Substances

  • A Kinase Anchor Proteins
  • Adrenergic beta-Agonists
  • Akap7 protein, mouse
  • DNA Primers
  • Cyclic AMP-Dependent Protein Kinases
  • Isoproterenol
  • Calcium