Enhanced amino acid utilization sustains growth of cells lacking Snf1/AMPK

Abstract

The metabolism of proliferating cells shows common features even in evolutionary distant organisms such as mammals and yeasts, for example the requirement for anabolic processes under tight control of signaling pathways. Analysis of the rewiring of metabolism, which occurs following the dysregulation of signaling pathways, provides new knowledge about the mechanisms underlying cell proliferation. The key energy regulator in yeast Snf1 and its mammalian ortholog AMPK have earlier been shown to have similar functions at glucose limited conditions and here we show that they also have analogies when grown with glucose excess. We show that loss of Snf1 in cells growing in 2% glucose induces an extensive transcriptional reprogramming, enhances glycolytic activity, fatty acid accumulation and reliance on amino acid utilization for growth. Strikingly, we demonstrate that Snf1/AMPK-deficient cells remodel their metabolism fueling mitochondria and show glucose and amino acids addiction, a typical hallmark of cancer cells.

SNF1 controls the glycolytic flux and mitochondrial respiration

“…This phenotype highlights the importance of SNF1 at low glucose concentrations. However, it was also reported that at 2% glucose, snf1Δ cells grown in synthetic medium showed similar glucose consumption as the WT strain (BY4741), but glucose consumption increased at 5% concentration, relative to the WT strain (Nicastro et al, ). Differences from previous reports could be due to the different medium used.…”

“…However, a clear relationship between the Crabtree effect and Snf1p has not been found yet. Cell glucose uptake is the main factor associated with the Crabtree effect and is regulated by hexose transporters mainly (Huberts et al, ), and in turn, the Snf1p/Mig1p pathway regulates transcriptionally some hexose transporters (Kuttykrishnan, Sabina, Langton, Johnston, & Brent, ; Nicastro et al, ). These data imply that Snf1p could regulate the glycolytic flux and the Crabtree effect, and our results support this idea.…”

“…Snf1p is a catabolic regulator that is activated by the increase in the ADP/ATP ratio (Mayer et al, ) or through phosphorylation by the kinases Sak1p, Elm3p, and Tos3p (Hong, Leiper, Woods, Carling, & Carlson, ; Kim, Hong, & Carlson, ; Liu, Xu, & Carlson, ). Snf1p activation has been linked to several catabolic pathways regulation such as mitochondrial respiration (Wright & Poyton, ), fatty acid metabolism (Zhang, Galdieri, & Vancura, ), and glycolysis (Nicastro et al, ). In this regard, the deletion of SNF1 gene has profound effects on glucose metabolism.…”

Snf1 Phosphorylates Adenylate Cyclase and Negatively Regulates Protein Kinase A-dependent Transcription in Saccharomyces cerevisiae

“…To detect possible new targets of Snf1, we chose to use a co-immunoprecipitation/MS approach, immunoprecipitating myc-tagged Snf1 and detecting co-immunoprecipitated proteins with mass spectrometry after resolution with SDS-PAGE. We performed this experiment with protein extracts of exponentially growing cells in 2% glucose, because we already demonstrated that in this condition Snf1 is at least partially functional (22,25).…”

“…In response to high glucose concentrations, Snf1 is inactivated through dephosphorylation of Thr 210 by the Glc7 protein phosphatase (also known as PP1), which is targeted to Snf1 by the adaptor subunit Reg1 (20,21). However, recent studies highlighted Snf1 function also in glucose-repressed conditions, as well as its partial activation and its role in the regulation of cell cycle (22)(23)(24)(25). The most studied function of Snf1 is the regulation of transcription, involving more than 400 genes (26).…”