Eukaryotic cells coordinately control anabolic and catabolic processes to maintain cell and tissue homeostasis. The mechanistic target of rapamycin complex 1 (mTORC1) promotes nutrient-consuming anabolic processes, such as protein synthesis1. Here, we show that accompanying an increase in protein synthesis, mTORC1 activation also promotes an increased capacity for protein degradation. Cells with activated mTORC1 exhibited elevated levels of intact and active proteasomes through a global increase in the expression of genes encoding proteasome subunits. The increase in proteasome gene expression, cellular proteasome content, and rates of protein turnover downstream of mTORC1 were all dependent on induction of the transcription factor nuclear factor erythroid-derived 2-related factor 1 (NFE2L1 or NRF1). Genetic activation of mTORC1 through loss of the tuberous sclerosis complex tumor suppressors or physiological activation of mTORC1 in response to growth factors or feeding resulted in increased NRF1 expression in cells and tissues. We find that this NRF1-dependent elevation of proteasome levels serves to increase the intracellular pool of amino acids, which thereby influences rates of new protein synthesis. Therefore, mTORC1 signaling increases the efficiency of proteasome-mediated protein degradation for both quality control and as a mechanism to supply substrate for sustained protein synthesis.

Drugs targeting metabotropic glutamate receptor 5 (mGluR5) have therapeutic potential in autism spectrum disorders (ASD), including tuberous sclerosis complex (TSC). The question whether inhibition or potentiation of mGluR5 could be beneficial depends, among other factors, on the specific indication. To facilitate the development of mGluR5 treatment strategies, we tested the therapeutic utility of mGluR5 negative and positive allosteric modulators (an mGluR5 NAM and PAM) for TSC, using a mutant mouse model with neuronal loss of Tsc2 that demonstrates disease-related phenotypes, including behavioral symptoms of ASD and epilepsy. This model uniquely enables the in vivo characterization and rescue of the electrographic seizures associated with TSC. We demonstrate that inhibition of mGluR5 corrects hyperactivity, seizures, and elevated de novo synaptic protein synthesis. Conversely, positive allosteric modulation of mGluR5 results in the exacerbation of hyperactivity and epileptic phenotypes. The data suggest a meaningful therapeutic potential for mGluR5 NAMs in TSC, which warrants clinical exploration and the continued development of mGluR5 therapies.

IntroductionLymphangioleiomyomatosis (LAM) occurs either associated with tuberous sclerosis complex (TSC) or as sporadic disease (S-LAM). Risk factors for development of S-LAM are unknown. We hypothesised that DNA sequence variants outside of TSC2/TSC1 might be associated with susceptibility for S-LAM and performed a genome-wide association study (GWAS).MethodsGenotyped and imputed data on 5 426 936 single nucleotide polymorphisms (SNPs) in 426 S-LAM subjects were compared, using conditional logistic regression, with similar data from 852 females from COPDGene in a matched case–control design. For replication studies, genotypes for 196 non-Hispanic White female S-LAM subjects were compared with three different sets of controls. RNA sequencing and immunohistochemistry analyses were also performed.ResultsTwo noncoding genotyped SNPs met genome-wide significance: rs4544201 and rs2006950 (p=4.2×10−8 and 6.1×10−9, respectively), which are in the same 35 kb linkage disequilibrium block on chromosome 15q26.2. This association was replicated in an independent cohort. NR2F2 (nuclear receptor subfamily 2 group F member 2), a nuclear receptor and transcription factor, was the only nearby protein-coding gene. NR2F2 expression was higher by RNA sequencing in one abdominal LAM tumour and four kidney angiomyolipomas, a LAM-related tumour, compared with all cancers from The Cancer Genome Atlas. Immunohistochemistry showed strong nuclear expression in both LAM and angiomyolipoma tumours.ConclusionsSNPs on chromosome 15q26.2 are associated with S-LAM, and chromatin and expression data suggest that this association may occur through effects on NR2F2 expression, which potentially plays an important role in S-LAM development.