title: Cardiomyocytes from AKAP7 knockout mice respond normally to adrenergic stimulation.
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.
authors.affiliation: Department of Pharmacology, University of Washington, Seattle, WA 98195, USA.
authors.forename: Brian W
authors.initials: BW
authors.lastname: Jones
authors.forename: Sylvain
authors.initials: S
authors.lastname: Brunet
authors.forename: Merle L
authors.initials: ML
authors.lastname: Gilbert
authors.forename: C Blake
authors.initials: CB
authors.lastname: Nichols
authors.forename: Thomas
authors.initials: T
authors.lastname: Su
authors.forename: Ruth E
authors.initials: RE
authors.lastname: Westenbroek
authors.forename: John D
authors.initials: JD
authors.lastname: Scott
authors.forename: William A
authors.initials: WA
authors.lastname: Catterall
authors.forename: G Stanley
authors.initials: GS
authors.lastname: McKnight
mesh_terms: D054758:A Kinase Anchor Proteins / Q000235:genetics / Q000378:metabolism*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D015139:Blotting, Southern; D002118:Calcium / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D015151:Immunoblotting; D047468:Immunoprecipitation; D007545:Isoproterenol / Q000494:pharmacology*; D051379:Mice; D018345:Mice, Knockout; D009200:Myocardial Contraction / Q000502:physiology*; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D054758:A Kinase Anchor Proteins; D000318:Adrenergic beta-Agonists; C487791:Akap7 protein, mouse; D017931:DNA Primers; D017868:Cyclic AMP-Dependent Protein Kinases; D007545:Isoproterenol; D002118:Calcium