Emergence of Orai3 activity during cardiac hypertrophy

Cardiovasc Res. 2015 Mar 1;105(3):248-59. doi: 10.1093/cvr/cvu207. Epub 2014 Sep 11.


Aims: Stromal interaction molecule 1 (STIM1) has been shown to control a calcium (Ca(2+)) influx pathway that emerges during the hypertrophic remodelling of cardiomyocytes. Our aim was to determine the interaction of Orai1 and Orai3 with STIM1 and their role in the constitutive store-independent and the store-operated, STIM1-dependent, Ca(2+) influx in cardiomyocytes.

Methods and results: We characterized the expression profile of Orai proteins and their interaction with STIM1 in both normal and hypertrophied adult rat ventricular cardiomyocytes. Orai1 and 3 protein levels were unaltered during the hypertrophic process and both proteins co-immunoprecipitated with STIM1. The level of STIM1 and Orai1 were significantly greater in the macromolecular complex precipitated by the Orai3 antibody in hypertrophied cardiomyocytes. We then used a non-viral method to deliver Cy3-tagged siRNAs in vivo to adult ventricular cardiomyocytes and silence Orai channel candidates. Cardiomyocytes were subsequently isolated then the voltage-independent, i.e. store-independent and store-operated Ca(2+) entries were measured on Fura-2 AM loaded Cy3-labelled and control isolated cardiomyocytes. The whole cell patch-clamp technique was used to measure Orai-mediated currents. Specific Orai1 and Orai3 knockdown established Orai3, but not Orai1, as the critical partner of STIM1 carrying these voltage-independent Ca(2+) entries in the adult hypertrophied cardiomyocytes. Orai3 also drove an arachidonic acid-activated inward current.

Conclusion: Cardiac Orai3 is the essential partner of STIM1 and drives voltage-independent Ca(2+) entries in adult cardiomyocytes. Arachidonic acid-activated currents, which are supported by Orai3, are present in adult cardiomyocytes and increased during hypertrophy.

Keywords: Calcium; Cardiac hypertrophy; Orai; STIM1; SiRNA.

Publication types

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

MeSH terms

  • Animals
  • Arachidonic Acid / pharmacology
  • Calcium Channel Agonists / pharmacology
  • Calcium Channels / drug effects
  • Calcium Channels / genetics
  • Calcium Channels / metabolism*
  • Calcium Signaling
  • Cells, Cultured
  • Disease Models, Animal
  • Hypertrophy, Left Ventricular / genetics
  • Hypertrophy, Left Ventricular / metabolism*
  • Hypertrophy, Left Ventricular / pathology
  • Male
  • Membrane Glycoproteins / metabolism
  • Membrane Potentials
  • Myocytes, Cardiac / drug effects
  • Myocytes, Cardiac / metabolism*
  • Myocytes, Cardiac / pathology
  • ORAI1 Protein
  • Protein Binding
  • RNA Interference
  • Rats, Wistar
  • Stromal Interaction Molecule 1
  • Time Factors
  • Transfection


  • Calcium Channel Agonists
  • Calcium Channels
  • Membrane Glycoproteins
  • ORAI1 Protein
  • Orai1 protein, rat
  • Orai3 protein, rat
  • Stim1 protein, rat
  • Stromal Interaction Molecule 1
  • Arachidonic Acid