Abstract
Quiescence is the prevailing state of many cell types under homeostatic conditions. Yet, surprisingly little is known about how quiescent cells respond to energetic and metabolic challenges. To better understand compensatory responses of quiescent cells to metabolic stress, we established, in human primary dermal fibroblasts, an experimental ‘energy restriction’ model. Quiescence was achieved by short-term culture in serum-deprived media and ATP supply restricted using a combination of glucose transport inhibitors and mitochondrial uncouplers. In aggregate, these measures led to markedly reduced intracellular ATP levels while not compromising cell viability over the observation period of 48 h. Analysis of the transcription factor (TF) landscape induced by this treatment revealed alterations in several signal transduction nodes beyond the expected biosynthetic adaptations. These included increased abundance of NF-κB regulated TFs and altered TF subsets regulated by Akt and p53. The observed changes in gene regulation and corresponding alterations in key signaling nodes are likely to contribute to cell survival at intracellular ATP concentrations substantially below those achieved by growth factor deprivation alone. This experimental model provides a benchmark for the investigation of cell survival pathways and related molecular targets that are associated with restricted energy supply associated with biological aging and metabolic diseases.
Highlights
Metabolic challenges due to limitations in nutrient uptake or mitochondrial dysfunction trigger adaptations that determine cell fate and survival
Much of the current understanding of metabolic stress responses is based on work with cycling cultured cells, or, in the case of aging, with cells subjected to replicative senescence (Toussaint et al, 2000; Bernard et al, 2004; Coppe et al, 2008; Chien et al, 2011)
The experimental approach taken in this study introduces a facile model to reveal targets, mechanisms and molecular network adjustments reflective of adaptive cell stress responses and extending beyond previously known pathways
Summary
Metabolic challenges due to limitations in nutrient uptake or mitochondrial dysfunction trigger adaptations that determine cell fate and survival. Metabolic challenges common in disease and aging are accompanied by adaptive changes in TF activity, as exemplified by increased Nuclear Factor kappaB (NF-κB) transcriptional activity. To mimic quiescence and low biosynthetic rates prevalent in vivo, we limited in the present study the exogenous growth factor supply to cultured human fibroblasts for 24 h (serum deprivation). Genomewide transcriptional profiling revealed a distinct shift in the TF landscape in response to combined nutrient and ATP deprivation. Our results establish an experimental approach to dissect signaling networks in energy-deprived quiescent cells and highlight distinct signaling nodes that may contribute to cell survival in metabolically challenged cells and tissues
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