Differential regulation of glucose transport activity in yeast by specific cAMP signatures

Abstract

Successful colonization and survival in variable environments require a competitive advantage during the initial growth phase after experiencing nutrient changes. Starved yeast cells anticipate exposure to glucose by activating the Hxt5p (hexose transporter 5) glucose transporter, which provides an advantage during early phases after glucose resupply. cAMP and glucose FRET (fluorescence resonance energy transfer) sensors were used to identify three signalling pathways that co-operate in the anticipatory Hxt5p activity in glucose-starved cells: as expected the Snf1 (sucrose nonfermenting 1) AMP kinase pathway, but, surprisingly, the sugar-dependent G-protein-coupled Gpr1 (G-protein-coupled receptor 1)/cAMP/PKA (protein kinase A) pathway and the Pho85 (phosphate metabolism 85)/Plc (phospholipase C) 6/7 pathway. Gpr1/cAMP/PKA are key elements of a G-protein-coupled sugar response pathway that produces a transient cAMP peak to induce growth-related genes. A novel function of the Gpr1/cAMP/PKA pathway was identified in glucose-starved cells: during starvation the Gpr1/cAMP/PKA pathway is required to maintain Hxt5p activity in the absence of glucose-induced cAMP spiking. During starvation, cAMP levels remain low triggering expression of HXT5, whereas cAMP spiking leads to a shift to the high capacity Hxt isoforms.

Fluorescent sensors reporting the activity of ammonium transceptors in live cells

“…They offer new tools for genetic screens, for example, for identifying regulatory networks, or they can be used for screening chemical libraries to identify new drugs (Bermejo et al, 2013). The existing tools, that is, FRET sensors for small molecules allow us to monitor steady state levels and dynamic changes of analytes such as ions, signaling compounds, metabolites and substrates of proteases (Okumoto et al, 2012).…”

A yeast FRET biosensor enlightens cAMP signalling

“…We present a FRET-based biosensor for dynamic, single-cell cAMP detection in yeast. Although a different FRET-based cAMP EPAC biosensor for budding yeast was published recently 69,70 , we believe that our yEPAC has significant improvements. It shows an exceptionally high a FRET range, up to a normalized ratio change of 1.8.…”

Molecular and Kinetic Characterization of the Fermentative Behavior of <i>Saccharomyces cerevisiae</i> Strains Isolated from North Patagonia

“…When cells endure starvation periods, they might anticipate glucose re-exposure by expressing the Hxt5p transporter, an advantage that could enable cells to take up glucose instantly after new hexose supplementation. Cells presenting this improved metabolic pathway of energy management efficiency may outcompete other yeasts [41]. These transcriptional regulations are physiologically relevant suggesting an enhanced metabolism to endure stressing conditions.…”