Archives of neurology · 2005
Severe impairment of complex I-driven adenosine triphosphate synthesis in leber hereditary optic neuropathy cybrids.
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Baracca Alessandra, Solaini Giancarlo, Sgarbi Gianluca, Lenaz Giorgio, Baruzzi Agostino, Schapira Anthony H V, Martinuzzi Andrea, Carelli Valerio
Аннотация
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.
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.