Abstract
mTOR is a highly conserved eukaryotic protein kinase that coordinates cell growth and metabolism and plays a critical role in cancer, immunity, and aging. It remains unclear how mTOR signaling in individual tissues contributes to whole-organism processes because mTOR inhibitors, like the natural product Rapamycin, are administered systemically and target multiple tissues simultaneously. We developed a chemical-genetic system, termed selecTOR, that restricts the activity of a Rapamycin analog to specific cell populations through targeted expression of a mutant FKBP12 protein. This analog has reduced affinity for its obligate binding partner FKBP12, which reduces its ability to inhibit mTOR in wild-type cells and tissues. Expression of the mutant FKBP12, which contains an expanded binding pocket, rescues the activity of this Rapamycin analog. Using this system, we show that selective mTOR inhibition can be achieved in S. cerevisiae and human cells, and we validate the utility of our system in an intact metazoan model organism by identifying the tissues responsible for a Rapamycin-induced developmental delay in Drosophila.
Significance Statement mTOR plays a number of critical organismal roles, including in cell growth, development, immunity and aging, but dissecting the tissue-specific influences of mTOR has proven challenging. This work describes a simple system for identifying the specific tissues and cells responsible for the diverse functions of mTOR, and we show that our system can be used in organisms ranging from yeast to humans.
Competing Interest Statement
K.M.S. is an inventor on patents owned by UCSF covering mTOR targeting small molecules licensed to Calithera Biosciences and Revolution Medicines. K.M.S. has consulting agreements for the following companies, which involve monetary and/or stock compensation: Revolution Medicines, Black Diamond Therapeutics, BridGene Biosciences, Denali Therapeutics, Dice Molecules, eFFECTOR Therapeutics, Erasca, Genentech/Roche, Janssen Pharmaceuticals, Kumquat Biosciences, Kura Oncology, Mitokinin, Type6 Therapeutics, Venthera, Wellspring Biosciences (Araxes Pharma), Turning Point, Ikena, Initial Therapeutics and BioTheryX.
Footnotes
Competing Interest Statement: K.M.S. is an inventor on patents owned by UCSF covering mTOR targeting small molecules licensed to Calithera Biosciences and Revolution Medicines. K.M.S. has consulting agreements for the following companies, which involve monetary and/or stock compensation: Revolution Medicines, Black Diamond Therapeutics, BridGene Biosciences, Denali Therapeutics, Dice Molecules, eFFECTOR Therapeutics, Erasca, Genentech/Roche, Janssen Pharmaceuticals, Kumquat Biosciences, Kura Oncology, Mitokinin, Type6 Therapeutics, Venthera, Wellspring Biosciences (Araxes Pharma), Turning Point, Ikena, Initial Therapeutics and BioTheryX.
Figure 6 and related text updated to include additional Drosophila driver lines. Conclusions regarding the role of the ring gland updated to reflect these new data. Supplemental files updated.