Phosphorylation state-dependent interaction between AKAP7?/? 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 AKAP7?/? [2,3]. Here, we further these findings by showing that phosphorylation of PLB requires interaction with AKAP7?/? and that this interaction occurs only when PLB is unphosphorylated. Additionally, we find that two mutants of PLB (R9C and ?14), which are associated with dilated cardiomyopathy in humans, prevent association with AKAP7?/? and display reduced phosphorylation in vitro. This finding implicates the AKAP7?/?-PLB interaction in the pathology of the disease phenotype. Further exploration of the AKAP7?/?-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 (50?M). Our results confirm that AKAP7?/? 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.

SUBMITTER: Rigatti M 

PROVIDER: S-EPMC4787601 | biostudies-literature | 2015 Sep

REPOSITORIES: biostudies-literature