Severe impairment of complex I-driven adenosine triphosphate synthesis in leber hereditary optic neuropathy cybrids.

Abstract

BACKGROUND:

Leber hereditary optic neuropathy (LHON) is a maternally inherited form of central vision loss associated with mitochondrial DNA point mutations that affect the ND subunits of complex I.

OBJECTIVE:

To elucidate the bioenergetic consequences of complex I dysfunction in LHON.

DESIGN:

The biochemical phenotypes of LHON mutations have been investigated using the transmitochondrial cytoplasmic hybrid (cybrid) cell model derived from the osteocarcoma parental cell line 143B.TK-.

SETTING:

Research laboratories at neuroscience and biochemistry departments at the University of Bologna, Scientific Institute "E. Medea," and University of College Medical School.

PARTICIPANTS:

Fibroblast cell lines were obtained from patients affected with LHON, as defined by the presence of 1 pathogenic mutation, and from healthy volunteers as controls to construct cybrid cell lines.

MAIN OUTCOME MEASURES:

Complex I (glutamate-malate)- and complex II (succinate)-dependent adenosine triphosphate (ATP) synthesis, their respective respiratory rates, and total cellular ATP content were investigated using digitonin permeabilized cybrid cells. Multiple cybrid cell lines were constructed, introducing into osteosarcoma-derived rho(0) cells either wild-type or LHON mutant mitochondria carrying each of the 3 common mutations at positions 11778/ND4, 3460/ND1, and 14484/ND6.

RESULTS:

All 3 LHON mutations impaired ATP synthesis and the respiratory control ratio driven by complex I substrates. In contrast, succinate-driven ATP synthesis, respiration rates, and respiratory control ratios were not affected. However, the defective ATP synthesis with complex I substrates did not result in reduced ATP cellular content, indicating a compensatory mechanism.

CONCLUSIONS:

The LHON pathogenic mutations profoundly impair complex I-dependent synthesis of ATP, providing a common biochemical feature that may play a major role in LHON pathogenesis. Stratification of the results by mutation suggests that the 11778/ND4 mutation may induce an uncoupling of cybrid respiration, whereas the other 2 mutations impair the oxygen consumption rate.

• Authors: Alessandra Baracca, Giancarlo Solaini, Gianluca Sgarbi, Giorgio Lenaz, Agostino Baruzzi, Anthony H V Schapira, Andrea Martinuzzi, Valerio Carelli
• Journal: Archives of neurology (Arch Neurol) Vol. 62 Issue 5 Pg. 730-6 (May 2005) ISSN: 0003-9942 [Print] United States
• PMID: 15883259 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• DNA, Mitochondrial
• Glutamates
• Citric Acid
• Adenosine Triphosphate
• Succinic Acid
• Electron Transport Complex I

Topics

• Adenosine Triphosphate (metabolism)
• Cells, Cultured
• Citric Acid (metabolism)
• DNA, Mitochondrial (genetics)
• Electron Transport Complex I (genetics, metabolism)
• Fibroblasts (enzymology)
• Glutamates (metabolism)
• Humans
• Hybrid Cells
• Mutation
• Optic Atrophy, Hereditary, Leber (enzymology, genetics)
• Oxygen Consumption (genetics)
• Succinic Acid (metabolism)