Diminished inhibition and facilitated activation of RyR2-mediated Ca 2+ release is a common defect of arrhythmogenic calmodulin mutations

FEBS J. 2019 Nov;286(22):4554-4578. doi: 10.1111/febs.14969. Epub 2019 Jul 12.

Abstract

A number of calmodulin (CaM) mutations cause severe cardiac arrhythmias, but their arrhythmogenic mechanisms are unclear. While some of the arrhythmogenic CaM mutations have been shown to impair CaM-dependent inhibition of intracellular Ca2+ release through the ryanodine receptor type 2 (RyR2), the impact of a majority of these mutations on RyR2 function is unknown. Here, we investigated the effect of 14 arrhythmogenic CaM mutations on the CaM-dependent RyR2 inhibition. We found that all the arrhythmogenic CaM mutations tested diminished CaM-dependent inhibition of RyR2-mediated Ca2+ release and increased store-overload induced Ca2+ release (SOICR) in HEK293 cells. Moreover, all the arrhythmogenic CaM mutations tested either failed to inhibit or even promoted RyR2-mediated Ca2+ release in permeabilized HEK293 cells with elevated cytosolic Ca2+ , which was markedly different from the inhibitory action of CaM wild-type. The CaM mutations also altered the Ca2+ -dependency of CaM binding to the RyR2 CaM-binding domain. These results demonstrate that diminished inhibition, and even facilitated activation, of RyR2-mediated Ca2+ release is a common defect of arrhythmogenic CaM mutations.

Keywords: arrhythmia; calmodulin; intracellular Ca2+ release; protein regulation; ryanodine receptor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arrhythmias, Cardiac / genetics*
  • Binding Sites
  • Calcium / metabolism*
  • Calcium Channels, L-Type / metabolism
  • Calcium Signaling*
  • Calmodulin / chemistry
  • Calmodulin / genetics*
  • Calmodulin / metabolism
  • HEK293 Cells
  • Humans
  • Mutation*
  • Protein Binding
  • Ryanodine Receptor Calcium Release Channel / chemistry
  • Ryanodine Receptor Calcium Release Channel / metabolism*
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases / metabolism

Substances

  • CACNA1C protein, human
  • Calcium Channels, L-Type
  • Calmodulin
  • Ryanodine Receptor Calcium Release Channel
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases
  • Calcium