Parenchymal damage and myeloid inflammation link the Rag GTPase – mTORC1 axis to mammalian aging [young]

The mechanistic target of rapamycin complex 1 (mTORC1) controls cellular anabolism in response to nutrient sufficiency and growth factor signaling, and genetic and pharmacological inhibition of mTORC1 extends longevity across eukaryotes. Up to date, mouse models to analyze the mechanisms of aging governed by mTORC1 has been limited by detrimental pleiotropic consequences of genetically-increased mTORC1 activity in mice. RragcS74N/+, RragcS74C/+ and RragcT89N/+ knock-in mice endogenously express active mutant variants of RagC, a GTPase that signaling nutrient sufficiency to mTORC1. Rragcmutant/+ mice show an only moderate increase in nutrient signaling to mTORC1, and after one year of life exhibit multiple features of a premature aging phenotype that include prominent senescence in peripheral organs, parenchymal expression of inflammatory and chemo-attractant molecules, increased myeloid inflammation and extensive features of inflammaging. In vivo transplantation and ex vivo functional experiments with bone marrow-derived cells show that myeloid cells are abnormally activated by parenchymal signals evoked from Rragcmut/+ organs, to where myeloid cells extravasate to inflict additional inflammatory damage. Therapeutic suppression of myeloid inflammation in old Rragcmut/+ attenuates features of premature aging and extends longevity. We provide the first genetic link of elevated nutrient – mTORC1 activity and premature aging in mammals, and provide support for a two-component model in which increased nutrient signaling drives parenchymal damage and myeloid inflammation precipitates organ deterioration and accelerated aging.