Abstract 14225: Reorganized PKA-AKAP Associations in the Failing Human Heart
Background: The cAMP pathway, with the cAMP-dependent protein kinase (PKA) in a key role, acts directly downstream of adrenergic receptors to mediate cardiac function at several levels through phosphorylation of multiple proteins (e.g. modulation of contractility, heart rate, repolarization times). To improve local organization, the regulatory subunit of PKA (PKA-R) is associated with A-kinase anchoring proteins (AKAPs), a protein family that tightly localizes PKA's activity to distinct loci within the cell. Sympathetic hyperactivity that chronically enhances adrenergic signaling in the heart ultimately triggers development of heart failure. We propose that PKA-AKAP complex formation is hampered in failing hearts, potentially leading to disturbed signaling and contractility.
Methods and results: Total cellular protein was isolated from human left ventricular free wall tissue of healthy hearts (N=6, C) and explanted hearts compromised through dilated cardiomyopathy (N=6, DCM). Using beads with immobilized cAMP, chemical proteomics strategies were applied to enrich for specific low abundant cyclic nucleotide signalling proteins which are key elements for contractility and electrical conduction. Different label-free quantitation methods were used to quantitatively compare C and DCM. As proposed, PKA regulatory subunit levels were indeed decreased in DCM conditions (PKA-RI, -RII both 2-fold down). In contrast, levels of cGMP pathway components were increased (PKG 3-fold up, PDE2 2.5-fold down). This could explain the altered cAMP signal transduction efficacy. Most striking was the observation that under DCM conditions, PKA RI and RII redistributed to a different set of AKAPs. From the 8 different AKAP isoforms that could be identified, increased association of PKA to AKAP2 (11-fold up), AKAP7 (5-fold up) and SPHKAP (11-fold up) was found in DCM hearts.
Conclusion: Altogether our data suggest that during human heart failure PKA activity is not only reduced but also redistributed to distinct different loci in the failing cardiomyocytes.
- © 2010 by American Heart Association, Inc.