A Novel Human R25C-phospholamban Mutation Is Associated With Super-Inhibition of Calcium Cycling and Ventricular Arrhythmia

Cardiovasc Res. 2015 Jul 1;107(1):164-74. doi: 10.1093/cvr/cvv127. Epub 2015 Apr 7.

Abstract

Aims: Depressed sarcoplasmic reticulum (SR) Ca(2+) cycling, a universal characteristic of human and experimental heart failure, may be associated with genetic alterations in key Ca(2+)-handling proteins. In this study, we identified a novel PLN mutation (R25C) in dilated cardiomyopathy (DCM) and investigated its functional significance in cardiomyocyte Ca(2+)-handling and contractility.

Methods and results: Exome sequencing identified a C73T substitution in the coding region of PLN in a family with DCM. The four heterozygous family members had implantable cardiac defibrillators, and three developed prominent ventricular arrhythmias. Overexpression of R25C-PLN in adult rat cardiomyocytes significantly suppressed the Ca(2+) affinity of SR Ca(2+)-ATPase (SERCA2a), resulting in decreased SR Ca(2+) content, Ca(2+) transients, and impaired contractile function, compared with WT-PLN. These inhibitory effects were associated with enhanced interaction of R25C-PLN with SERCA2, which was prevented by PKA phosphorylation. Accordingly, isoproterenol stimulation relieved the depressive effects of R25C-PLN in cardiomyocytes. However, R25C-PLN also elicited increases in the frequency of Ca(2+) sparks and waves as well as stress-induced aftercontractions. This was accompanied by increased Ca(2+)/calmodulin-dependent protein kinase II activity and hyper-phosphorylation of RyR2 at serine 2814.

Conclusion: The findings demonstrate that human R25C-PLN is associated with super-inhibition of SERCA2a and Ca(2+) transport as well as increased SR Ca(2+) leak, promoting arrhythmogenesis under stress conditions. This is the first mechanistic evidence that increased PLN inhibition may impact both SR Ca(2+) uptake and Ca(2+) release activities and suggests that the human R25C-PLN may be a prognostic factor for increased ventricular arrhythmia risk in DCM carriers.

Keywords: Calcium cycling; Dilated cardiomyopathy; Mutation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Animals
  • Arrhythmias, Cardiac / etiology*
  • Calcium / metabolism*
  • Calcium-Binding Proteins / genetics*
  • Cardiomyopathy, Dilated / genetics
  • Cells, Cultured
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • HEK293 Cells
  • Humans
  • Isoproterenol / pharmacology
  • Male
  • Middle Aged
  • Mutation*
  • Myocytes, Cardiac / metabolism
  • Rats
  • Ryanodine Receptor Calcium Release Channel / metabolism
  • Sarcoplasmic Reticulum / metabolism
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases / metabolism

Substances

  • Calcium-Binding Proteins
  • Ryanodine Receptor Calcium Release Channel
  • phospholamban
  • Cyclic AMP-Dependent Protein Kinases
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases
  • Isoproterenol
  • Calcium