Endoplasmic reticulum-mitochondria crosstalk in NIX-mediated murine cell death

J Clin Invest. 2009 Jan;119(1):203-12. doi: 10.1172/JCI36445. Epub 2008 Dec 8.


Transcriptional upregulation of the proapoptotic BCL2 family protein NIX limits red blood cell formation and can cause heart failure by inducing cell death, but the requisite molecular events are poorly defined. Here, we show complementary mechanisms for NIX-mediated cell death involving direct and ER/sarcoplasmic reticulum-mediated (ER/SR-mediated) mitochondria disruption. Endogenous cardiac NIX and recombinant NIX localize both to the mitochondria and to the ER/SR. In genetic mouse models, cardiomyocyte ER/SR calcium stores are proportional to the level of expressed NIX. Whereas Nix ablation was protective in a mouse model of apoptotic cardiomyopathy, genetic correction of the decreased SR calcium content of Nix-null mice restored sensitivity to cell death and reestablished cardiomyopathy. Nix mutants specific to ER/SR or mitochondria activated caspases and were equally lethal, but only ER/SR-Nix caused loss of the mitochondrial membrane potential. These results establish a new function for NIX as an integrator of transcriptional and calcium-mediated signals for programmed cell death.

Publication types

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

MeSH terms

  • Animals
  • Calcium / metabolism
  • Calcium Signaling / physiology
  • Cell Death / physiology*
  • Cell Line
  • Endoplasmic Reticulum / metabolism*
  • Humans
  • Membrane Potential, Mitochondrial / physiology
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Mice
  • Mice, Knockout
  • Mitochondria / metabolism*
  • Mitochondrial Proteins / genetics
  • Mitochondrial Proteins / metabolism*
  • Myocytes, Cardiac / cytology
  • Myocytes, Cardiac / metabolism
  • Rats
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Sarcoplasmic Reticulum / metabolism
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases / genetics
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases / metabolism
  • Transcription, Genetic


  • Membrane Proteins
  • Mitochondrial Proteins
  • Nix protein, mouse
  • Recombinant Proteins
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases
  • Calcium