Yeast AMP-activated Protein Kinase Monitors Glucose Concentration Changes and Absolute Glucose Levels

• Published in: The Journal of biological chemistry Vol. 289; no. 18; pp. 12863 - 12875
• Main Authors: Bendrioua, Loubna, Smedh, Maria, Almquist, Joachim, Cvijovic, Marija, Jirstrand, Mats, Goksör, Mattias, Adiels, Caroline B., Hohmann, Stefan
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 02.05.2014; American Society for Biochemistry and Molecular Biology
• Subjects: AMP-activated Kinase (AMPK); AMP-Activated Protein Kinases - genetics; AMP-Activated Protein Kinases - metabolism; Biochemistry and Molecular Biology; Biokemi och molekylärbiologi; Cell Nucleus - metabolism; Cytoplasm - metabolism; Dynamic Control; Fluorescence Recovery After Photobleaching; Glucose - metabolism; Glucose - pharmacology; Green Fluorescent Proteins - genetics; Green Fluorescent Proteins - metabolism; Microfluidics - methods; Microscopy, Fluorescence; Nuclear Translocation; Phosphorylation; Protein Transport - drug effects; Protein-Serine-Threonine Kinases - genetics; Protein-Serine-Threonine Kinases - metabolism; Repressor Proteins - genetics; Repressor Proteins - metabolism; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; Signal Transduction; Yeast Physiology; Dynamic Control; AMP-activated Kinase (AMPK); Signal Transduction; Nuclear Translocation; Glucose Metabolism; Yeast Physiology
• ISSN: 0021-9258; 1083-351X; 1083-351X
• DOI: 10.1074/jbc.M114.547976

Analysis of the time-dependent behavior of a signaling system can provide insight into its dynamic properties. We employed the nucleocytoplasmic shuttling of the transcriptional repressor Mig1 as readout to characterize Snf1-Mig1 dynamics in single yeast cells. Mig1 binds to promoters of target genes and mediates glucose repression. Mig1 is predominantly located in the nucleus when glucose is abundant. Upon glucose depletion, Mig1 is phosphorylated by the yeast AMP-activated kinase Snf1 and exported into the cytoplasm. We used a three-channel microfluidic device to establish a high degree of control over the glucose concentration exposed to cells. Following regimes of glucose up- and downshifts, we observed a very rapid response reaching a new steady state within less than 1 min, different glucose threshold concentrations depending on glucose up- or downshifts, a graded profile with increased cell-to-cell variation at threshold glucose concentrations, and biphasic behavior with a transient translocation of Mig1 upon the shift from high to intermediate glucose concentrations. Fluorescence loss in photobleaching and fluorescence recovery after photobleaching data demonstrate that Mig1 shuttles constantly between the nucleus and cytoplasm, although with different rates, depending on the presence of glucose. Taken together, our data suggest that the Snf1-Mig1 system has the ability to monitor glucose concentration changes as well as absolute glucose levels. The sensitivity over a wide range of glucose levels and different glucose concentration-dependent response profiles are likely determined by the close integration of signaling with the metabolism and may provide for a highly flexible and fast adaptation to an altered nutritional status. Little is known about the signaling dynamics of AMP-activated protein kinase. We define the dynamics of yeast AMPK signaling under different glucose concentrations. The Snf1-Mig1 signaling system monitors glucose concentration changes and absolute glucose levels to adjust the metabolism to a wide range of conditions. This description of AMPK signaling dynamics will stimulate studies defining the integration of signaling and metabolism.