Investigating the interaction of AKAPs with PLN to mediate phosphorylation processes

A common characteristic of cardiomyopathy is dysregulated Ca2+-cycling. During Ca2+-cycling, Sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) reuptakes Ca2+ into the sarcoplasmic reticulum (SR). SERCA is inhibited by Phospholamban (PLN). PLN inhibition is reversed through phosphorylation of Ser16 by protein kinase-A (PKA) when anchored to A-kinase anchoring proteins (AKAPs). Previous studies identified 3 human PLN-mutants –R9C, R14Del, and L39stop– causing cardiomyopathy. We were interested in the mechanisms by which wild-type PLN (PLN-WT) and PLN-mutants are phosphorylated through AKAPs-PLN-PKA interactions. Using publically-available RNA-seq and proteomic data we identified muscle AKAP (mAKAP) to be expressed in the heart. Immunofluorescent data showed mAKAP to be expressed in the SR and co-localizing with PLN. Immunoprecipitation in co-transfected HEKs showed pull-down of mAKAP and PLN-WT/mutants. We showed PLN-mutants exhibit altered protein phosphorylation and mAKAP-PLN interactions. In conclusion, we determined a possible link between mAKAP and PLN for the regulation of PLN phosphorylation by PKA.M.Sc.2019-03-26 00:00:0