cAMP signaling pathway controls glycogen metabolism in Neurospora crassa by regulating the glycogen synthase gene expression and phosphorylation

Freitas, Fernanda Zanolli; Paula, Renato M. de; Barbosa, Luiz Carlos Bertucci; Terenzi, Héctor Francisco; Bertolini, Maria Célia

doi:10.1016/j.fgb.2009.10.011

Cited by 32 publications

(30 citation statements)

References 51 publications

(57 reference statements)

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“…This may explain the decrease in glycogen levels observed in cells exposed to heat shock [4]–[6]. gsn expression and GSN phosphorylation are also regulated by the cAMP-protein kinase A (PKA) signaling pathway [7]. Thus, the regulation of glycogen metabolism in N. crassa involves different proteins whose activation may be influenced by different signaling pathways.…”

Section: Introductionmentioning

confidence: 99%

Ambient pH Controls Glycogen Levels by Regulating Glycogen Synthase Gene Expression in Neurospora crassa. New Insights into the pH Signaling Pathway

Cupertino

Freitas

Paula³

et al. 2012

PLoS ONE

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Glycogen is a polysaccharide widely distributed in microorganisms and animal cells and its metabolism is under intricate regulation. Its accumulation in a specific situation results from the balance between glycogen synthase and glycogen phosphorylase activities that control synthesis and degradation, respectively. These enzymes are highly regulated at transcriptional and post-translational levels. The existence of a DNA motif for the Aspergillus nidulans pH responsive transcription factor PacC in the promoter of the gene encoding glycogen synthase (gsn) in Neurospora crassa prompted us to investigate whether this transcription factor regulates glycogen accumulation. Transcription factors such as PacC in A. nidulans and Rim101p in Saccharomyces cerevisiae play a role in the signaling pathway that mediates adaptation to ambient pH by inducing the expression of alkaline genes and repressing acidic genes. We showed here that at pH 7.8 pacC was over-expressed and gsn was down-regulated in wild-type N. crassa coinciding with low glycogen accumulation. In the pacCKO strain the glycogen levels and gsn expression at alkaline pH were, respectively, similar to and higher than the wild-type strain at normal pH (5.8). These results characterize gsn as an acidic gene and suggest a regulatory role for PACC in gsn expression. The truncated recombinant protein, containing the DNA-binding domain specifically bound to a gsn DNA fragment containing the PacC motif. DNA-protein complexes were observed with extracts from cells grown at normal and alkaline pH and confirmed by ChIP-PCR analysis. The PACC present in these extracts showed equal molecular mass, indicating that the protein is already processed at normal pH, in contrast to A. nidulans. Together, these results show that the pH signaling pathway controls glycogen accumulation by regulating gsn expression and suggest the existence of a different mechanism for PACC activation in N. crassa.

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Section: Introductionmentioning

confidence: 99%

Ambient pH Controls Glycogen Levels by Regulating Glycogen Synthase Gene Expression in Neurospora crassa. New Insights into the pH Signaling Pathway

Cupertino

Freitas

Paula³

et al. 2012

PLoS ONE

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“…In addition, different signaling pathways could be involved establishing a signaling network that results in hyper accumulation of the reserve carbohydrates. Previous work has demonstrated the involvement of the cAMP-PKA signaling pathway [26] and the SNF-1 protein kinase [41] in glycogen metabolism regulation in N. crassa , which are described as involved in the response of S. cerevisiae to high pH [39, 42]. We hypothesize that both of these pathways likely contribute to the pH signaling pathway in N. crassa in order to maintain proper levels of the reserve carbohydrate in a pH-independent response.…”

Section: Discussionmentioning

confidence: 99%

“…Cellular extracts were clarified and the supernatants were used for glycogen, trehalose and protein quantification. Glycogen content was quantified according to [26] and trehalose was quantified following the protocol described by [27], with modifications. Glycogen was precipitated with cold ethanol and digested with α-amylase and amyloglucosidase and trehalose was digested with a partially purified trehalase from Humicola grisea [28].…”

Section: Methodsmentioning

confidence: 99%

Regulation of the reserve carbohydrate metabolism by alkaline pH and calcium in Neurospora crassa reveals a possible cross-regulation of both signaling pathways

et al. 2017

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BackgroundGlycogen and trehalose are storage carbohydrates and their levels in microorganisms vary according to environmental conditions. In Neurospora crassa, alkaline pH stress highly influences glycogen levels, and in Saccharomyces cerevisiae, the response to pH stress also involves the calcineurin signaling pathway mediated by the Crz1 transcription factor. Recently, in yeast, pH stress response genes were identified as targets of Crz1 including genes involved in glycogen and trehalose metabolism. In this work, we present evidence that in N. crassa the glycogen and trehalose metabolism is modulated by alkaline pH and calcium stresses. ResultsWe demonstrated that the pH signaling pathway in N. crassa controls the accumulation of the reserve carbohydrates glycogen and trehalose via the PAC-3 transcription factor, which is the central regulator of the signaling pathway. The protein binds to the promoters of most of the genes encoding enzymes of glycogen and trehalose metabolism and regulates their expression. We also demonstrated that the reserve carbohydrate levels and gene expression are both modulated under calcium stress and that the response to calcium stress may involve the concerted action of PAC-3. Calcium activates growth of the Δpac-3 strain and influences its glycogen and trehalose accumulation. In addition, calcium stress differently regulates glycogen and trehalose metabolism in the mutant strain compared to the wild-type strain. While glycogen levels are decreased in both strains, the trehalose levels are significantly increased in the wild-type strain and not affected by calcium in the mutant strain when compared to mycelium not exposed to calcium.ConclusionsWe previously reported the role of PAC-3 as a transcription factor involved in glycogen metabolism regulation by controlling the expression of the gsn gene, which encodes an enzyme of glycogen synthesis. In this work, we extended the investigation by studying in greater detail the effects of pH on the metabolism of the reserve carbohydrate glycogen and trehalose. We also demonstrated that calcium stress affects the reserve carbohydrate levels and the response to calcium stress may require PAC-3. Considering that the reserve carbohydrate metabolism may be subjected to different signaling pathways control, our data contribute to the understanding of the N. crassa responses under pH and calcium stresses.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-017-3832-1) contains supplementary material, which is available to authorized users.

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“…Besides reversible changes in their activities, glycogen levels are also correlated with physiological conditions. In addition, other proteins may also be involved in glycogen accumulation because protein activation resulting from different signaling pathways affects glycogen storage (3,4).In N. crassa, glycogen content reaches a maximal level at the end of the exponential growth phase. However, under stress conditions, such as heat shock, glycogen content drops rapidly (5, 6).…”

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A Genome-wide Screen for Neurospora crassa Transcription Factors Regulating Glycogen Metabolism

Gonçalves

Cupertino

Freitas

et al. 2011

Molecular & Cellular Proteomics

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Transcription factors play a key role in transcription regulation as they recognize and directly bind to defined sites in promoter regions of target genes, and thus modulate differential expression. The overall process is extremely dynamic, as they have to move through the nucleus and transiently bind to chromatin in order to regulate gene transcription. To identify transcription factors that affect glycogen accumulation in Neurospora crassa, we performed a systematic screen of a deletion strains set generated by the Neurospora Knockout Project and available at the Fungal Genetics Stock Center. In a wild-type strain of N. crassa, glycogen content reaches a maximal level at the end of the exponential growth phase, but upon heat stress the glycogen content rapidly drops. The gene encoding glycogen synthase (gsn) is transcriptionally downregulated when the mycelium is exposed to the same stress condition. We identified 17 deleted strains having glycogen accumulation profiles different from that of the wild-type strain under both normal growth and heat stress conditions. Most of the transcription factors identified were annotated as hypothetical protein, however some of them, such as the PacC, XlnR, and NIT2 proteins, were biochemically well-characterized either in N. crassa or in other fungi. The fungus Neurospora crassa has been widely used as a model organism for the understanding of fundamental aspects of eukaryotic biology. The knowledge of its genome sequence (1) has allowed the identification of proteins required for gene regulation, such as the transcriptional regulatory proteins. An examination of the classes of transcription factors in the N. crassa genome reveals that the organism carries elements shared by simple and complex metazoan models (2). The availability of a set of deletion strains, each carrying a deletion in a specific ORF encoding a transcription factor, allows the screening for genes linked to a particular phenotype. Here we used this mutant strains set to identify transcription factors that either directly or indirectly regulate glycogen metabolism in N. crassa.In many organisms, glycogen is a carbon and energy reserve carbohydrate with an intricate metabolism regulation that senses nutrient availability and other environmental conditions. The amount of glycogen found in a particular situation results from the balance between glycogen synthase and glycogen phosphorylase activities. These enzymes regulate, respectively, the synthesis and degradation of this compound and they are both regulated by phosphorylation. Besides reversible changes in their activities, glycogen levels are also correlated with physiological conditions. In addition, other proteins may also be involved in glycogen accumulation because protein activation resulting from different signaling pathways affects glycogen storage (3,4).In N. crassa, glycogen content reaches a maximal level at the end of the exponential growth phase. However, under stress conditions, such as heat shock, glycogen content drops rapidly (5, 6). The ...

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cAMP signaling pathway controls glycogen metabolism in Neurospora crassa by regulating the glycogen synthase gene expression and phosphorylation

Cited by 32 publications

References 51 publications

Ambient pH Controls Glycogen Levels by Regulating Glycogen Synthase Gene Expression in Neurospora crassa. New Insights into the pH Signaling Pathway

Ambient pH Controls Glycogen Levels by Regulating Glycogen Synthase Gene Expression in Neurospora crassa. New Insights into the pH Signaling Pathway

Regulation of the reserve carbohydrate metabolism by alkaline pH and calcium in Neurospora crassa reveals a possible cross-regulation of both signaling pathways

A Genome-wide Screen for Neurospora crassa Transcription Factors Regulating Glycogen Metabolism

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