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Direct PKA‐PDE interactions lead to localized cAMP signaling domains in adult cardiomyocytes (1013.7)
Author(s) -
Boras Britton,
Taylor Susan,
McCulloch Andrew
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.28.1_supplement.1013.7
Subject(s) - protein kinase a , phospholamban , serca , microbiology and biotechnology , endoplasmic reticulum , ryanodine receptor , chemistry , phosphodiesterase , biophysics , phosphorylation , signal transduction , biology , biochemistry , atpase , enzyme
The β‐adrenergic pathway in cardiomyocytes activates protein kinase A (PKA) to phosphoregulate several Ca2+ handling proteins, including L‐type Ca2+ channels, ryanodine receptors, and sarco/endoplasmic reticulum Ca2+‐ATPases (SERCA) (via phospholamban), resulting in inotropic, lusitropic and chronotropic responses. Based on PKA kinetics measured in vitro, almost all PKA should be activated by basal concentrations of cAMP, limiting its dynamic range in response to a stimulus event. Several studies have postulated a role for local degradation of cAMP by phosphodiesterases (PDE) in maintaining microdomains with lower cAMP concentrations around A kinase anchoring proteins (AKAP), which bind both PKA and PDE. In this study we use 3‐D diffusional modeling around cell geometries from transmission electron microscopy (TEM) images to show that local clustering of PDEs is insufficient to maintain cAMP microdomains necessary for lower PKA basal activation. We instead propose a new model for PKA activation which incorporates direct binding between PDE’s and the regulatory subunit of PKA as a pathway to stimulate PDE activity and inhibit PKA activation. We used in vitro kinetic experiments with 3H tagged cAMP and purified PKA and PDE to quantify this interaction and explore its specificity both for PKA and PDE isoforms. Grant Funding Source : Supported by: NIH 5 T32 HL 105373‐2