Supernumerary subunits of mitochondrial complex I and resistance to viral infection – VIROXPHOS

-Molecular and cellular biology (construction of vectors, cell and tissue imaging appraoches)
-Transgenesis and gene editing in mosquitoes
-RNAi-mediated silencing of gene expression

in progress

in progress

in preparation

Over the past decades, we have observed worldwide increases in numbers of infections by mosquito borne diseases caused by viruses such as Dengue (DENV), Zika (ZIKV) and Chikungunya. Currently, there are no effective treatments or vaccines available for most mosquito borne viruses. Aedes mosquitoes are crucial components of the transmission cycle of these arthropod-borne viruses (arboviruses) and can be an important target to help avert outbreaks. Vector population control is still utilized but its real impact on virus transmission is unclear. Alternatively, strategies that affect virus-vector interactions have been proposed to reduce transmission by affecting the ability of mosquitoes to acquire, maintain and transmit the virus. These strategies require mechanistic understanding about the virus replication cycle and antiviral mechanisms acting during infection in vector mosquitoes.

We have recently shown that RNA interference, the main antiviral defense in insects, does not participate in the control of DENV or ZIKV in the midgut of mosquitoes. While investigating the mechanism of resistance in this tissue, we observed that 7 accessory/supernumerary subunits of complex I of the mitochondrial respiratory chain are differentially expressed between DENV resistant and susceptible mosquitoes. The function of these supernumerary subunits remains unclear but they may affect different aspects of complex I function, localization and regulation, and possibly mitochondrial morphology. Complex I may affect antiviral responses or directly affect viral replication. In favor of the first hypothesis, mitochondria are a platform for antiviral signaling in vertebrates that could be affected by changes in complex I. Nevertheless, components of antiviral pathways present in mammalian mitochondria are not conserved in mosquitoes and other invertebrates. Thus, it is also possible that complex I directly regulates some aspect of cell physiology that affects viral replication. Hence, the major goal of this proposal is to characterize the functions of supernumerary subunits of Complex I and how they regulate resistance to viruses. We will use the power of genetic tools available in the Drosophila model to dissect the function of the 7 supernumerary subunits of complex I that differentially expressed between resistant and susceptible mosquitoes. In Drosophila, we will also investigate how these subunits impact virus infections and the activation of known innate antiviral pathways. In parallel, we will continue to characterize the biology of DENV and ZIKV infections in the gut of mosquitoes when we target supernumerary subunits or interfere with complex I function.

The project is exploring uncharted territory on the function of supernumerary subunits of complex I and their potential involvement in a respiration code that modulates specific outputs of oxidative phosphorylation in eukaryotic cells. It will involve collaboration between three laboratories with complementary sets of expertise in virus-host interactions and immunity in drosophila and mosquitoes (Imler and Marques teams) and in mitochondrial bioenergetics and energy metabolism (Mourier team). It is possible that our results will also have implication for the overall cell-intrinsic responses to these viruses since recent reports indicate that the mitochondria and cellular respiration are important for the infection cycle of DENV in mammalian cells.