Decreased agonist-stimulated mitochondrial ATP production caused by a pathological reduction in endoplasmic reticulum calcium content in human complex I deficiency

Biochim Biophys Acta. 2006 Jan;1762(1):115-23. doi: 10.1016/j.bbadis.2005.09.001. Epub 2005 Sep 16.


Although a large number of mutations causing malfunction of complex I (NADH:ubiquinone oxidoreductase) of the OXPHOS system is now known, their cell biological consequences remain obscure. We previously showed that the bradykinin (Bk)-induced increase in mitochondrial [ATP] ([ATP](M)) is significantly reduced in primary skin fibroblasts from a patient with an isolated complex I deficiency. The present work addresses the mechanism(s) underlying this impaired response. Luminometry of fibroblasts from 6 healthy subjects and 14 genetically characterized patients expressing mitochondria targeted luciferase revealed that the Bk-induced increase in [ATP](M) was significantly, but to a variable degree, decreased in 10 patients. The same variation was observed for the increases in mitochondrial [Ca(2+)] ([Ca(2+)](M)), measured with mitochondria targeted aequorin, and cytosolic [Ca(2+)] ([Ca(2+)](C)), measured with fura-2, and for the Ca(2+) content of the endoplasmic reticulum (ER), calculated from the increase in [Ca(2+)](C) evoked by thapsigargin, an inhibitor of the ER Ca(2+) ATPase. Regression analysis revealed that the increase in [ATP](M) was directly proportional to the increases in [Ca(2+)](C) and [Ca(2+)](M) and to the ER Ca(2+) content. Our findings provide evidence that a pathological reduction in ER Ca(2+) content is the direct cause of the impaired Bk-induced increase in [ATP](M) in human complex I deficiency.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / agonists*
  • Adenosine Triphosphate / biosynthesis*
  • Adult
  • Bradykinin / pharmacology
  • Calcium / metabolism*
  • Calcium Signaling / drug effects*
  • Cells, Cultured
  • Child
  • Child, Preschool
  • Electron Transport Complex I / deficiency*
  • Endoplasmic Reticulum / metabolism*
  • Fibroblasts / pathology
  • Humans
  • Infant
  • Infant, Newborn
  • Mitochondria / metabolism*


  • Adenosine Triphosphate
  • Electron Transport Complex I
  • Bradykinin
  • Calcium