Lethal, hereditary mutants of phospholamban elude phosphorylation by protein kinase A.
The sarcoplasmic reticulum calcium pump (SERCA) and its regulator, phospholamban, are essential components of cardiac contractility. Phospholamban modulates contractility by inhibiting SERCA, and this process is dynamically regulated by β-adrenergic stimulation and phosphorylation of phospholamban. Herein we reveal mechanistic insight into how four hereditary mutants of phospholamban, Arg(9) to Cys, Arg(9) to Leu, Arg(9) to His, and Arg(14) deletion, alter regulation of SERCA. Deletion of Arg(14) disrupts the protein kinase A recognition motif, which abrogates phospholamban phosphorylation and results in constitutive SERCA inhibition. Mutation of Arg(9) causes more complex changes in function, where hydrophobic substitutions such as cysteine and leucine eliminate both SERCA inhibition and phospholamban phosphorylation, whereas an aromatic substitution such as histidine selectively disrupts phosphorylation. We demonstrate that the role of Arg(9) in phospholamban function is multifaceted: it is important for inhibition of SERCA, it increases the efficiency of phosphorylation, and it is critical for protein kinase A recognition in the context of the phospholamban pentamer. Given the synergistic consequences on contractility, it is not surprising that the mutants cause lethal, hereditary dilated cardiomyopathy.
Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
Delaine K
DK
Ceholski
Catharine A
CA
Trieber
Charles F B
CF
Holmes
Howard S
HS
Young
D000595:Amino Acid Sequence; D000818:Animals; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002311:Cardiomyopathy, Dilated / Q000235:genetics / Q000473:pathology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D006579:Heterozygote; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010766:Phosphorylation; D011817:Rabbits; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D000099211:Phospholamban
D002135:Calcium-Binding Proteins; D017868:Cyclic AMP-Dependent Protein Kinases; D011994:Recombinant Proteins; D000099211:Phospholamban