Evaluation of the thermogenic properties of the mitochondrial alternative oxidase expressed in Drosophila melanogaster

Author(s)

Geovana Siqueira Garcia

• Document type: Master's Dissertation
• Press: São José do Rio Preto. 2019-03-07.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências Letras e Ciências Exatas. São José do Rio Preto
• Defense date: 2019-02-19
• Advisor: Marcos Túlio Oliveira

Abstract

Alternative oxidase (AOX) is an enzyme that catalyzes a redox reaction similarly to complexes III and IV of the respiratory chain (RC), but without the proton pumping into the mitochondrial intermembrane space. It therefore does not contribute to the proton-motive force that leads to ATP production and so the energy is dissipated as heat. AOX is present in most metazoans, but not in vertebrates and insects, which independently lost throughout evolution its coding gene. When the enzyme was expressed transgenically in Drosophila melanogaster and other experimental models, AOX improved in the deleterious conditions associated to mitochondrial dysfunctions, presenting with a therapeutic potential. The beneficial effects, however, contrast with the lack of in-depth information about the biology of AOX in animals, especially in nature-like laboratory conditions. Considering this and the knowledge about its thermogenic function in plants, we aimed at investigating the effects of AOX expression in D. melanogaster under varying thermal conditions, testing the hypothesis that the enzyme generates an increase in organismal body temperature. We submitted different AOX-expressing lines to various temperatures, including severe stress conditions for analysis during development and during the adult stage. AOX promoted dose-dependent acceleration in development, significantly increased viability of eggs/larvae at low temperatures (12 and 15°C). It also promoted higher resistance to cold (0°C) and faster recovery after cold exposure in adults. Infrared thermography images of larvae showed an increase in larval body temperature. Although the data are consistent with the heat generation hypothesis, in vitro respirometry analysis in larval extracts did not show significant biochemical effects of AOX expression on mitochondrial oxygen consumption, which could explain any thermogenic mechanism. Therefore, AOX attenuates the effects of cold, through a complex role in animal metabolism, which warrants further investigation. (AU)

• FAPESP's process: 17/03806-7 - Evaluation of the thermogenic properties of the mitochondrial alternative oxidase expressed in Drosophila melanogaster
• Grantee: Geovana Siqueira Garcia
• Support Opportunities: Scholarships in Brazil - Master