MTORC1 functions as a transcriptional regulator of autophagy by preventing nuclear transport of TFEB

Abstract

The mammalian target of rapamycin (MTOR) protein kinase complex is a key component of a pathway that regulates cell growth and proliferation in response to energy levels, hypoxia, nutrients and insulin. Inhibition of MTORC1 strongly induces autophagy by regulating the activity of the ULK protein kinase complex that is required for the formation of autophagosomes. However, the participation of MTORC1 in the expression of autophagy genes has not been characterized. Here we show that MTORC1 regulates nuclear localization and activity of the transcription factor EB (TFEB), a member of the bHLH leucine-zipper family of transcription factors that drives expression of autophagy and lysosomal genes. Under normal nutrient conditions, TFEB is phosphorylated in Ser211 in an MTORC1-dependent manner. This phosphorylation promotes association of TFEB with members of the YWHA (14-3-3) family of proteins and retention of the transcription factor in the cytosol. Pharmacological or genetic inhibition of MTORC1 causes dissociation of the TFEB/YWHA complex and rapid transport of TFEB to the nucleus where it increases transcription of multiple genes implicated in autophagy and lysosomal function. Active TFEB also associates with late endosomal/lysosomal membranes through interaction with the LAMTOR/RRAG/MTORC1 complex. Our results unveil a novel role for MTORC1 in the maintenance of cellular homeostasis by regulating autophagy at the transcriptional level.

Advanced glycation end‐products suppress autophagic flux in podocytes by activating mammalian target of rapamycin and inhibiting nuclear translocation of transcription factor EB

“…The former is a novel agent with stronger capacity to inhibit mTOR activity compared with rapamycin 11, 26.…”

MiT/TFE transcription factors are activated during mitophagy downstream of Parkin and Atg5

“…In the current model of TFEB activation upon nutrient depletion, regulation of TFEB phosphorylation at residues S142 and S211 by mTORC1 plays a critical role, particularly as dephosphorylation of S211 is predicted to expose a nuclear import sequence that is otherwise occluded by 14-3-3 binding (Martina et al, 2012; Roczniak-Ferguson et al, 2012; Settembre et al, 2012). As occurs upon mTOR inhibition (Settembre et al, 2011(Settembre et al, , 2012, Parkin-mediated TFEB nuclear accumulation corresponds with TFEB dephosphorylation.…”

“…To corroborate these findings, we assessed the phosphorylation status of TFEB residues S142 and S211, established to be critical regulators of TFEB translocation and transcriptional activity through the actions of mTORC1 and extracellular signal-regulated kinase 2 (Settembre et al, 2011(Settembre et al, , 2012Martina et al, 2012;Roczniak-Ferguson et al, 2012). Immunoblotting of phospho-S142 and indirect analysis of phospho-S211 via coimmunoprecipitation of 14-3-3 bound to TFEB-GFP revealed a pronounced decrease in the former but little to no reduction in F for quantification.…”

Erratum: TFEB controls cellular lipid metabolism through a starvation-induced autoregulatory loop

“…Most importantly, the absence of TFEB results in an impairment of lipid catabolism and in a more severe metabolic derangement in obese animals, while TFEB overexpression causes the opposite effects and rescues obesity and associated metabolic syndrome. TFEB mRNA expression is induced by starvation by a post-transcriptional switch that controls TFEB nuclear translocation [29][30][31] , which allows TFEB to rapidly respond to nutrient availability, and a positive transcriptional autoregulatory component for a sustained response. Autoregulatory feedback circuits are used by eukaryotic cells to convert a graded input into a binary (ON/OFF) response in eukaryotic gene circuits [32][33][34] .…”