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Updated: May 3, 2026
Measurement of Carbon Dioxide Production from Radiolabeled Substrates in Drosophila melanogaster
Published on: June 27, 2016
Decrease in cytochrome c oxidase reserve capacity diminishes robustness of Drosophila melanogaster and shortens
Vladimir Klichko1, Barbara H Sohal2, Svetlana N Radyuk1
1*Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275, U.S.A.
Abstract:
The phenotypic effects of under- and over-expression of CcO (cytochrome c oxidase) regulatory subunits IV and Vb were examined in Drosophila melanogaster in order to test further the hypothesis that suppression of the activities of mitochondrial ETC (electron-transport chain) oxidoreductases retards the aging process and extends lifespan. Underexpression of both CcO subunits, induced by RNAi, resulted in decreases in the respective mRNA and protein levels, CcO holoenzyme activity, rate of mitochondrial respiration, walking speed and the lifespan of fruitflies. Overexpression of CcO IV or Vb in young fruitflies increased the amount of mRNA, but had no effect on the protein level or CcO catalytic activity. On the other hand, in older fruitflies, overexpression of CcO Vb, but not CcO IV, elevated the mRNA and protein amounts as well as the CcO holoenzyme activity, thereby preventing the typical age-related decline in CcO activity. Nevertheless, lifespans of the fruitflies overexpressing CcO IV or Vb were neither extended nor shortened. Our results demonstrate that: (i) the suppression of CcO function exerts deleterious rather than benign effects on fitness and survival, and (ii) the structure/function of CcO, an ETC oxidoreductase, can be 're-engineered' in vivo.
Insights
Suppressing cytochrome c oxidase (CcO) function harms fruitfly survival, contrary to aging theories. Re-engineering CcO activity in vivo shows complex effects on lifespan and fitness.
Area of Science:
- Mitochondrial biology
- Aging research
- Genetics
Background:
- The hypothesis that suppressing mitochondrial electron-transport chain (ETC) oxidoreductase activity retards aging is widely studied.
- Cytochrome c oxidase (CcO) is a key enzyme in the mitochondrial ETC, crucial for cellular respiration.
- Understanding CcO's role in aging requires examining the effects of its regulatory subunits.
Purpose of the Study:
- To investigate the phenotypic consequences of altering CcO regulatory subunits IV and Vb in Drosophila melanogaster.
- To test the hypothesis that reduced ETC activity, specifically CcO function, might extend lifespan.
- To explore the potential for in vivo re-engineering of CcO structure and function.
Main Methods:
- RNA interference (RNAi) was used to induce underexpression of CcO subunits IV and Vb.
- Overexpression studies were conducted in both young and old Drosophila.
- Measurements included mRNA and protein levels, CcO holoenzyme activity, mitochondrial respiration rates, and lifespan.
Main Results:
- Underexpression of CcO subunits led to decreased mRNA, protein, CcO activity, respiration, walking speed, and lifespan.
- Overexpression of CcO IV or Vb in young flies increased mRNA but not protein or activity.
- Overexpression of CcO Vb in older flies increased mRNA, protein, and activity, counteracting age-related decline, but did not alter lifespan.
Conclusions:
- Suppression of CcO function has detrimental effects on fitness and survival, challenging the proposed benefits of reduced ETC activity.
- The study demonstrates that CcO, an ETC oxidoreductase, can be functionally modified in vivo.
- CcO's role in aging is complex, with specific subunit manipulations yielding varied outcomes without lifespan extension.
