Confirmation of Decreased Rates of Cerebral Protein Synthesis In Vivo in a Mouse Model of Tuberous Sclerosis Complex

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder that results in intellectual disability and, in ∼50% of patients, autism spectrum disorder. The protein products that are altered in TSC (TSC1 and TSC2) form a complex to inhibit the mammalian target of rapamycin [mTOR; mTOR complex 1 (mTORC1)] pathway. This pathway has been shown to affect the process of mRNA translation through its action on ribosomal protein S6 and 4-elongation binding protein 1. It is thought that mutations in the TSC proteins lead to upregulation of the mTORC1 pathway and consequently an increase in protein synthesis. Unexpectedly, our previous study of a mouse model of TSC (Tsc2(Djk)(+/−)) demonstrated decreased in vivo rates of protein synthesis throughout the brain. In the present study, we confirm those results in another Tsc2(+/−) mouse model, one with a different mutation locus and on a mixed background (Tsc2(Mjg)(+/−)). We also examine mTORC1 signaling and possible effects of prior isoflurane anesthesia. Because measurements of protein synthesis rates in vivo require surgical preparation of the animal and anesthesia, we examine mTORC1 signaling pathways both under baseline conditions and following recovery from anesthesia. Our results demonstrate regionally selective effects of prior anesthesia. Overall, our results in both in vivo models suggest divergences from the central hypothesis regarding TSC and show the importance of studying protein synthesis in vivo.