Rapamycin is an inhibitor of the mechanistic Target of Rapamycin pathway (mTOR). This drug
has anti-carcinogenic and pro-longevity characteristics. We, and others, have shown that
rapamycin could also be considered as a treatment for mitochondrial disorders since feeding
rapamycin to genetic models for mitochondrial disorders improve the pathology associated with
the diseases. However, resistance to rapamycin hinders the efficacy of such treatment.
Molecular genetic analysis in D. melanogaster provides unique approaches to uncover the basic
mechanism of insensitivity of rapamycin. In this context, we have discovered that introgressed
strains of Drosophila harboring mitochondrial DNA form D. simulans in a D. melanogaster
nuclear DNA do not respond to rapamycin treatment while wild type D. melanogaster or wild
type D. simulans respond to the drug. In addition, we discovered that rapamycin beneficial effect
on mitochondrial function requires a shift of metabolism, in particular, the catabolism of proteins.
Wild type D. melanogaster fed a diet rich on proteins, or lacking proteins do not respond to the
increase on metabolic rate mediated by rapamycin. Metabolomics analysis and preliminary
molecular genetics analysis with mutants for the glutamate dehydrogenase, the enzyme that
catabolize glutamate into alpha-ketoglutarate, have identified the critical role of the glutamine,
glutamate and alpha-ketoglutarate anapleourotic (Gln-Glu-aKG) pathway in the response to
rapamycin. Based on our observations and the documented effects of the sensitivity and the
resistance to rapamycin, in this proposal we will test the hypothesis that rapamycin sensitivity
depends upon the qualitative used of the Gln-Glu-aKG pathway by the cell. To test this
hypothesis, we will use a combination of introgressed mitochondrial DNAs strains, with and
without mutations on genes that codify for several members of the the Gln-Glu-aKG pathway.
We will study the sensitivity and resistance to rapamycin treatment by exposing the
aforementioned strains to rapamycin treatment in the presence and absence of amino acids
supplementation. We will complement those analyses with metabolomics assays that will depict
the metabolic space of the resistance to rapamycin. Overall, this proposal aims to identified the
hallmarks of the insensitivity to rapamycin treatment using a unique set of tools provided with
the use of mitochondria introgressed strains.