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

• Published in: Biochimica et biophysica acta Vol. 1762; no. 1; pp. 115 - 123
• Main Authors: Visch, Henk-Jan, Koopman, Werner J.H., Leusink, Anouk, van Emst-de Vries, Sjenet E., van den Heuvel, Lambertus W.P.J., Willems, Peter H.G.M., Smeitink, Jan A.M.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 2006
• Subjects: Adenosine Triphosphate - agonists; Adenosine Triphosphate - biosynthesis; Adult; ATP; Bradykinin; Bradykinin - pharmacology; Calcium - metabolism; Calcium Signaling - drug effects; Cells, Cultured; Child; Child, Preschool; Complex I deficiency; Electron Transport Complex I - deficiency; Endoplasmic Reticulum - metabolism; ER calcium content; Fibroblasts - pathology; Humans; Infant; Infant, Newborn; Mitochondria; Mitochondria - metabolism; ER calcium content; [Ca 2+] M; ANT; Complex I deficiency; IMM; OXPHOS; Bk; BHQ; SERCA; ER; [ATP] M; [Ca 2+] C; Δ ψ; Mitochondria; CGP37157; Bradykinin; IP 3; ATP
• ISSN: 0925-4439; 0006-3002; 1879-260X
• DOI: 10.1016/j.bbadis.2005.09.001

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.