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Rigatti M.,Pat and Jim Calhoun Center for Cardiovascular Research | Rigatti M.,The Richard rlin Center For Cell Analysis And Omodeling | Le A.V.,Pat and Jim Calhoun Center for Cardiovascular Research | Le A.V.,The Richard rlin Center For Cell Analysis And Omodeling | And 6 more authors.
Cellular Signalling | Year: 2015

Changes in heart rate and contractility in response to sympathetic stimulation occur via activation of cAMP dependent protein kinase A (PKA), leading to phosphorylation of numerous substrates that alter Ca2+ cycling. Phosphorylation of these substrates is coordinated by A-kinase anchoring proteins (AKAPs), which recruit PKA to specific substrates [1]. Phosphorylation of the PKA substrate phospholamban (PLB) is a critical determinant of Ca2+ re-entry into the sarcoplasmic reticulum and is coordinated by AKAP7δ/γ [2,3]. Here, we further these findings by showing that phosphorylation of PLB requires interaction with AKAP7δ/γ and that this interaction occurs only when PLB is unphosphorylated. Additionally, we find that two mutants of PLB (R9C and δ14), which are associated with dilated cardiomyopathy in humans, prevent association with AKAP7δ/γ and display reduced phosphorylation in vitro. This finding implicates the AKAP7δ/γ-PLB interaction in the pathology of the disease phenotype. Further exploration of the AKAP7δ/γ-PLB association demonstrated a phosphorylation state-dependence of the interaction. Computational modeling revealed that this mode of interaction allows for small amounts of AKAP and PKA (100-200nM) to regulate the phosphorylation of large quantities of PLB (50μM). Our results confirm that AKAP7γ/δ binding to PLB is important for phosphorylation of PLB, and describe a novel phosphorylation state-dependent binding mechanism that explains how phosphorylation of highly abundant PKA substrates can be regulated by AKAPs present at ~100-200 fold lower concentrations. •AKAP7δ/γ links PKA to phospholamban, enhancing phosphorylation of phospholabman•This interaction is disrupted in several defined human mutations•Phosphorylation of phospholamban decreases the affinity for AKAP7δ/γ, allowing for state-dependent binding•Computational analysis suggests that state-dependent binding allows AKAP7δ/γ-bound PKA to phosphorylated phospholamban. © 2015 Elsevier Inc.

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