Project description:TORC1 regulates growth and metabolism, in part, by influencing transcriptional programs. Here, we identify REPTOR and REPTOR-BP as transcription factors downstream of TORC1 that are required for ∼ 90% of the transcriptional induction that occurs upon TORC1 inhibition in Drosophila. Thus, REPTOR and REPTOR-BP are major effectors of the transcriptional stress response induced upon TORC1 inhibition, analogous to the role of FOXO downstream of Akt. We find that, when TORC1 is active, it phosphorylates REPTOR on Ser527 and Ser530, leading to REPTOR cytoplasmic retention. Upon TORC1 inhibition, REPTOR becomes dephosphorylated in a PP2A-dependent manner, shuttles into the nucleus, joins its partner REPTOR-BP to bind target genes, and activates their transcription. In vivo functional analysis using knockout flies reveals that REPTOR and REPTOR-BP play critical roles in maintaining energy homeostasis and promoting animal survival upon nutrient restriction.
Project description:The first aim was to identify genes whose transcription is induced by rapamycin feeding in Drosophila S2 cells. Secondly, the goal was to find out which contribution the transcription factors REPTOR (=CG13624) and REPTOR-BP (REPTOR-binding partner, =CG18619) has to the observed changes in expression. We thus compared gene epxression between rapamycin and control treated S2 cells in GFP, REPTOR or REPTOR-BP knockdown cells.
Project description:Metabolic flexibility of muscle tissue describes the adaptive capacity to use different energy substrates according to their availability. The disruption of this ability associates with metabolic disease. Here, using a Drosophila model of systemic metabolic dysfunction triggered by yorkie-induced gut tumors, we show that the transcription factor REPTOR is an important regulator of energy metabolism in muscles. We present evidence that REPTOR is activated in muscles of adult flies with gut yorkie-tumors, where it modulates glucose metabolism. Further, in vivo studies indicate that sustained activity of REPTOR is sufficient in wildtype muscles to repress glycolysis and increase tricarboxylic acid (TCA) cycle metabolites. Consistent with the fly studies, higher levels of CREBRF, the mammalian ortholog of REPTOR, reduce glycolysis in mouse myotubes while promoting oxidative metabolism. Altogether, our results define a conserved function for REPTOR and CREBRF as key regulators of muscle energy metabolism.
Project description:The first aim was to identify genes whose transcription is induced by rapamycin feeding in Drosophila S2 cells. Secondly, the goal was to find out which contribution the transcription factors REPTOR (=CG13624) and REPTOR-BP (REPTOR-binding partner, =CG18619) has to the observed changes in expression. We thus compared gene epxression between rapamycin and control treated S2 cells in GFP, REPTOR or REPTOR-BP knockdown cells. 3 biological replicates from control knockdown plus/minus rapamycin and REPTOR knockdown plus/minus rapamycin; 2 biological replicates from REPTOR-BP knockdown cells plus/minus rapamycin; together those are 16 samples
Project description:The mechanistic target of rapamycin complex 1 (mTORC1) is a master regulator of cell growth that stimulates macromolecule synthesis through transcription, RNA processing, and post-translational modification of metabolic enzymes. However, the mechanisms of how mTORC1 orchestrates multiple steps of gene expression programs remain unclear. Here, we identify family with sequence similarity 120A (FAM120A) as a transcription co-activator that couples transcription and splicing of de novo lipid synthesis enzymes downstream of mTORC1-serine/arginine-rich protein kinase 2 (SRPK2) signaling. The mTORC1-activated SRPK2 phosphorylates splicing factor serine/arginine-rich splicing factor 1 (SRSF1), enhancing its binding to FAM120A. FAM120A directly interacts with a lipogenic transcription factor SREBP1 at active promoters, thereby bridging the newly transcribed lipogenic genes from RNA polymerase II to the SRSF1 and U1-70K-containing RNA-splicing machinery. This mTORC1-regulated, multi-protein complex promotes efficient splicing and stability of lipogenic transcripts, resulting in fatty acid synthesis and cancer cell proliferation. These results elucidate FAM120A as a critical transcription co-factor that connects mTORC1-dependent gene regulation programs for anabolic cell growth.
Project description:Glutamoptosis is the induction of apoptotic cell death as a consequence of the aberrant activation of glutaminolysis and mTORC1 signaling during nutritional imbalance in proliferating cells. The role of the bioenergetic sensor AMPK during glutamoptosis is not defined yet. Here, we show that AMPK reactivation blocks both the glutamine-dependent activation of mTORC1 and glutamoptosis in vitro and in vivo. We also show that glutamine is used for asparagine synthesis and the GABA shunt to produce ATP and to inhibit AMPK, independently of glutaminolysis. Overall, our results indicate that glutamine metabolism is connected with mTORC1 activation through two parallel pathways: an acute alpha-ketoglutarate-dependent pathway; and a secondary ATP/AMPK-dependent pathway. This dual metabolic connection between glutamine and mTORC1 must be considered for the future design of therapeutic strategies to prevent cell growth in diseases such as cancer.