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Mitochondrial antibodies--heterogeneity and effects on mitochondrial respiration
Abstract:
Sera containing antimitochondrial antibodies (MTA) were tested for binding to intact mitochondria, sonic fragments (SMP), Complex I + III and to oligomycin sensitive ATPase (OS-ATPase) from bovine heart by indirect immunofluorescence. Antigens capable of binding to MTA were present in mitochondria and its fragments tested. Maximum binding was observed with SMP. It appears that one or more antigen binding sites are present on the matrix side of the inner mitochondrial membrane or some location exterior to the inner membrane. Normal human serum or sera containing MTA did not effect the respiration of intact mitochondria or sonic particles. However, NADH-cytochrome c reductase activity of complex I + III was enhanced by 10-60% by sera containing MTA antibodies.
Insights
Sera with antimitochondrial antibodies (MTA) bind to mitochondrial components, particularly sonic fragments (SMP). These antibodies enhance NADH-cytochrome c reductase activity, suggesting a role in mitochondrial function.
Area of Science:
- Immunology
- Biochemistry
- Cell Biology
Background:
- Mitochondria are crucial for cellular energy production.
- Antimitochondrial antibodies (MTA) are associated with certain autoimmune diseases.
- The precise targets and functions of MTA within mitochondria require further elucidation.
Purpose of the Study:
- To investigate the binding characteristics of MTA to various mitochondrial fractions.
- To determine the effect of MTA on mitochondrial respiratory chain enzyme activity.
Main Methods:
- Indirect immunofluorescence was used to detect antibody binding to intact mitochondria, sonic fragments (SMP), Complex I + III, and oligomycin-sensitive ATPase (OS-ATPase) from bovine heart.
- Mitochondrial respiration and NADH-cytochrome c reductase activity were measured in the presence of normal human serum and sera containing MTA.
Main Results:
- Antigens binding MTA were found in all tested mitochondrial fractions, with maximum binding observed in SMP.
- Antibody binding sites may be located on the matrix side or exterior to the inner mitochondrial membrane.
- MTA did not affect the respiration of intact mitochondria or SMP.
- Sera containing MTA enhanced NADH-cytochrome c reductase activity of Complex I + III by 10-60%.
Conclusions:
- Mitochondrial components, especially SMP, are targets for MTA.
- MTA may modulate the activity of specific mitochondrial enzymes like NADH-cytochrome c reductase.
- These findings contribute to understanding the immunobiology of mitochondria and potential roles of MTA in disease pathogenesis.