title: Phosphorylation state-dependent interaction between AKAP7δ/γ and phospholamban increases phospholamban phosphorylation.
abstract: 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 Ca(2+) 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 Ca(2+) 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.
authors.affiliation: Pat and Jim Calhoun Center for Cardiovascular Research, UCONN Health, 263 Farmington Ave, Farmington, CT 06030, USA; The Richard D. Berlin Center for Cell Analysis & Modeling, UCONN Health, 400 Farmington Ave, Farmington, CT 06030, USA.
authors.forename: Marc
authors.initials: M
authors.lastname: Rigatti
authors.affiliation: Pat and Jim Calhoun Center for Cardiovascular Research, UCONN Health, 263 Farmington Ave, Farmington, CT 06030, USA; The Richard D. Berlin Center for Cell Analysis & Modeling, UCONN Health, 400 Farmington Ave, Farmington, CT 06030, USA.
authors.forename: Andrew V
authors.initials: AV
authors.lastname: Le
authors.affiliation: Pat and Jim Calhoun Center for Cardiovascular Research, UCONN Health, 263 Farmington Ave, Farmington, CT 06030, USA; The Richard D. Berlin Center for Cell Analysis & Modeling, UCONN Health, 400 Farmington Ave, Farmington, CT 06030, USA.
authors.forename: Claire
authors.initials: C
authors.lastname: Gerber
authors.affiliation: Pat and Jim Calhoun Center for Cardiovascular Research, UCONN Health, 263 Farmington Ave, Farmington, CT 06030, USA; The Richard D. Berlin Center for Cell Analysis & Modeling, UCONN Health, 400 Farmington Ave, Farmington, CT 06030, USA.
authors.forename: Ion I
authors.initials: II
authors.lastname: Moraru
authors.affiliation: Pat and Jim Calhoun Center for Cardiovascular Research, UCONN Health, 263 Farmington Ave, Farmington, CT 06030, USA; The Richard D. Berlin Center for Cell Analysis & Modeling, UCONN Health, 400 Farmington Ave, Farmington, CT 06030, USA. Electronic address: dodge@uchc.edu.
authors.forename: Kimberly L
authors.initials: KL
authors.lastname: Dodge-Kafka
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D009154:Mutation; D032386:Myoblasts, Cardiac / Q000378:metabolism*; D010766:Phosphorylation / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D012519:Sarcoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D000099211:Phospholamban
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002135:Calcium-Binding Proteins; D017868:Cyclic AMP-Dependent Protein Kinases; D000099211:Phospholamban; C526078:Akap7 protein, rat
keywords: AKAP; Anchoring; Phospholamban; Phosphorylation; Scaffold