The Trehalose Pathway Regulates Mitochondrial Respiratory Chain Content through Hexokinase 2 and cAMP in Saccharomyces cerevisiae

Hexokinase 2 (Hxk2) from Saccharomyces cerevisiae is a bifunctional enzyme, being both a catalyst in the cytosol and an important regulator of the glucose repression signal in the nucleus. Despite considerable recent progress, little is known about the regulatory mechanism that controls nuclear Hxk2 association with the SUC2 promoter chromatin and how this association is necessary for SUC2 gene repression. Our data indicate that in the SUC2 promoter context, Hxk2 functions through a variety of structurally unrelated factors, mainly the DNA-binding Mig1 and Mig2 repressors and the regulatory Snf1 and Reg1 factors. Hxk2 sustains the repressor complex architecture maintaining transcriptional repression at the SUC2 gene. Using chromatin immunoprecipitation assays, we discovered that the Hxk2 in its open configuration, at low glucose conditions, leaves the repressor complex that induces its dissociation and promotes SUC2 gene expression. In high glucose conditions, Hxk2 adopts a close conformation that promotes Hxk2 binding to the Mig1 protein and the reassembly of the SUC2 repressor complex. Additional findings highlight the possibility that Hxk2 constitutes an intracellular glucose sensor that operates by changing its conformation in response to cytoplasmic glucose levels that regulate its interaction with Mig1 and thus its recruitment to the repressor complex of the SUC2 promoter. Thus, our data indicate that Hxk2 is more intimately involved in gene regulation than previously thought.

supporting

confidence: 49%

Hexokinase 2 Is an Intracellular Glucose Sensor of Yeast Cells That Maintains the Structure and Activity of Mig1 Protein Repressor Complex

Vega¹,

Riera²,

Fernández-Cid³

et al. 2016

“…It has been shown that treatment of human preadipocytes with forskolin (which leads to an overactivation of the cAMP pathway) increased mitochondrial DNA copy number (10). In yeast, there is now a growing amount of evidence showing that overactivation of the Ras/ cAMP pathway leads to an increase in the cell mitochondrial content (11)(12)(13). Yeast has three A kinase catalytic subunits, which have greater than 75% identity and are encoded by the TPK (TPK1, TPK2, and TPK3) genes (14).…”

mentioning

confidence: 99%

Reactive Oxygen Species-mediated Regulation of Mitochondrial Biogenesis in the Yeast Saccharomyces cerevisiae

Chevtzoff

Yoboue

Galinier

et al. 2010

Self Cite

Mitochondrial biogenesis is a complex process. It necessitates the participation of both the nuclear and the mitochondrial genomes. This process is highly regulated, and mitochondrial content within a cell varies according to energy demand. In the yeast Saccharomyces cerevisiae, the cAMP pathway is involved in the regulation of mitochondrial biogenesis. An overactivation of this pathway leads to an increase in mitochondrial enzymatic content. Of the three yeast cAMP protein kinases, we have previously shown that Tpk3p is the one involved in the regulation of mitochondrial biogenesis. In this paper, we investigated the molecular mechanisms that govern this process. We show that in the absence of Tpk3p, mitochondria produce large amounts of reactive oxygen species that signal to the HAP2/3/4/5 nuclear transcription factors involved in mitochondrial biogenesis. We establish that an increase in mitochondrial reactive oxygen species production down-regulates mitochondrial biogenesis. It is the first time that a redox sensitivity of the transcription factors involved in yeast mitochondrial biogenesis is shown. Such a process could be seen as a mitochondria quality control process.Cells adapt to their energy needs by adjusting their mitochondrial enzymatic content, resulting in a capacity to modulate ATP turnover (1). This has been shown to occur in a wide range of cell types, from yeast (2) and HeLa cells (3) to skeletal muscle (4). Mitochondria have their own genome that encodes a few (13 in mammals and 8 in yeast) of the 100 proteins necessary for oxidative phosphorylation (5). The remaining proteins necessary for the biogenesis of oxidative phosphorylation complexes are encoded by the nuclear genome. Mitochondrial biogenesis thus depends on the coordination of nuclear and mitochondrial events. Moreover, mitochondria to nucleus signaling has been a longstanding question.In mammalian cells, it has been shown that the mitochondrial reactive oxygen species are involved in the activation of the serine/threonine protein kinase D, which in turn activates NF-B, leading to induction of SOD2 (mitochondrial superoxide dismutase) and consequently efficient detoxification from mitochondrial reactive oxygen species (6). In HeLa cells, respiratory uncoupling, which is well known to decrease mitochondrial reactive oxygen species (ROS) 2 production, activates NRF-1 (nuclear respiratory factor-1) (3). NRF-1 is a transcription factor encoded by nuclear DNA (7), and functional binding sites for NRF-1 have been described in several genes critical for mitochondrial biogenesis (8). Furthermore, during aging, it has been shown that while mitochondrial ROS production increases, there is a concomitant decrease in mitochondrial oxidative phosphorylation complex amount and activity (9). Altogether, these results point to a possible role of ROS as signaling molecules in the cross-talk between mitochondria and nucleus.In living cells, growth is the result of coupling between substrate catabolism and multiple metabolic processes taking place dur...

“…We made use of this strain in order to manipulate intracellular cAMP concentration to various extents and study the energy metabolism response to variations in the activity of the Ras/cAMP pathway. Extracellular cAMP concentrations of 1-3 mM were used that led to physiological variations of the intracellular cAMP concentration from 4 to 50 M (Table 1) (16,26,27). Under these conditions, no significant modification in cell proliferation was assessed (data not shown).…”

Section: Resultsmentioning

confidence: 99%

cAMP-induced Mitochondrial Compartment Biogenesis

Yoboue

Augier

Galinier

et al. 2012

Self Cite

Background: Mitochondrial biogenesis is a complex process, and its regulation is not well known. Results: cAMP-induced mitochondrial biogenesis through a decrease in the cellular phosphate potential is due to an increase in the glutathione redox status. Conclusion: Mitochondrial biogenesis is tightly linked to glutathione redox status. Significance: This is the first evidence for a glutathione redox control of a transcription factor involved in mitochondrial biogenesis.