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Metabolic respiration induces AMPK- and Ire1p-dependent activation of the p38-Type HOG MAPK pathway.

Adhikari H, Cullen PJ - PLoS Genet. (2014)

Bottom Line: Such cross-modulation was critical to optimize the differentiation response.The human fungal pathogen Candida albicans showed a similar regulatory circuit.Thus, an evolutionarily conserved regulatory axis links metabolic respiration and AMPK to Ire1p, which regulates a differentiation response involving the modulated activity of ERK and p38 MAPK pathways.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, State University of New York at Buffalo, Buffalo, New York, United States of America.

ABSTRACT
Evolutionarily conserved mitogen activated protein kinase (MAPK) pathways regulate the response to stress as well as cell differentiation. In Saccharomyces cerevisiae, growth in non-preferred carbon sources (like galactose) induces differentiation to the filamentous cell type through an extracellular-signal regulated kinase (ERK)-type MAPK pathway. The filamentous growth MAPK pathway shares components with a p38-type High Osmolarity Glycerol response (HOG) pathway, which regulates the response to changes in osmolarity. To determine the extent of functional overlap between the MAPK pathways, comparative RNA sequencing was performed, which uncovered an unexpected role for the HOG pathway in regulating the response to growth in galactose. The HOG pathway was induced during growth in galactose, which required the nutrient regulatory AMP-dependent protein kinase (AMPK) Snf1p, an intact respiratory chain, and a functional tricarboxylic acid (TCA) cycle. The unfolded protein response (UPR) kinase Ire1p was also required for HOG pathway activation in this context. Thus, the filamentous growth and HOG pathways are both active during growth in galactose. The two pathways redundantly promoted growth in galactose, but paradoxically, they also inhibited each other's activities. Such cross-modulation was critical to optimize the differentiation response. The human fungal pathogen Candida albicans showed a similar regulatory circuit. Thus, an evolutionarily conserved regulatory axis links metabolic respiration and AMPK to Ire1p, which regulates a differentiation response involving the modulated activity of ERK and p38 MAPK pathways.

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Role of increased metabolic respiration and Snf1p in activation of the HOG pathway.A) Immunoblot showing P∼Hog1p levels in cells grown in glucose (YEPD), galactose (YEP-GAL) or glucose and galactose (YEPD+2% GAL). B) Wild-type cells (PC6016) and the gal3Δ, gal4Δ, gal7Δ and gal10Δ mutants grown in YEP-GAL. C) P∼Hog1 levels in cells grown under the indicated conditions for 3 h with or without antimycin, ANT. D) Wild type (PC538) and the aco1Δ (PC3912), fum1Δ (PC6152), mdh1Δ (PC6153) and kgd1Δ (PC6155) and idh1Δ (PC6154) mutants were grown in galactose for 5.5 hrs. E) Wild-type cells (PC538), and the snf1Δ (PC560), mig1Δ (PC4843) and snf1Δ mig1Δ (PC6076) mutants were grown in YEP-GAL medium for 5.5 hrs.
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pgen-1004734-g003: Role of increased metabolic respiration and Snf1p in activation of the HOG pathway.A) Immunoblot showing P∼Hog1p levels in cells grown in glucose (YEPD), galactose (YEP-GAL) or glucose and galactose (YEPD+2% GAL). B) Wild-type cells (PC6016) and the gal3Δ, gal4Δ, gal7Δ and gal10Δ mutants grown in YEP-GAL. C) P∼Hog1 levels in cells grown under the indicated conditions for 3 h with or without antimycin, ANT. D) Wild type (PC538) and the aco1Δ (PC3912), fum1Δ (PC6152), mdh1Δ (PC6153) and kgd1Δ (PC6155) and idh1Δ (PC6154) mutants were grown in galactose for 5.5 hrs. E) Wild-type cells (PC538), and the snf1Δ (PC560), mig1Δ (PC4843) and snf1Δ mig1Δ (PC6076) mutants were grown in YEP-GAL medium for 5.5 hrs.

Mentions: Glucose is the preferred carbon source in yeast [86], [87]. When glucose is abundant, yeast cells exclusively utilize that nutrient over non-preferred carbon sources like galactose. Glucose repression prevents the transport and utilization of other carbon sources [86], [88]–[90]. As shown above, glucose added to cells grown on galactose resulted in attenuation of the HOG response (Fig. 2F). To further test whether glucose prevents the HOG response to galactose, cells were grown in media containing both glucose and galactose as a carbon source. Under this condition, HOG pathway signaling was also attenuated (Fig. 3A). These experiments indicate that galactose metabolism is required for HOG pathway activation. Consistent with this possibility, mutants defective for galactose transport and utilization (Fig. 3B; gal3Δ, gal4Δ, gal7Δ, and gal10Δ [88], [90]–[93]) were defective for HOG pathway activation.


Metabolic respiration induces AMPK- and Ire1p-dependent activation of the p38-Type HOG MAPK pathway.

Adhikari H, Cullen PJ - PLoS Genet. (2014)

Role of increased metabolic respiration and Snf1p in activation of the HOG pathway.A) Immunoblot showing P∼Hog1p levels in cells grown in glucose (YEPD), galactose (YEP-GAL) or glucose and galactose (YEPD+2% GAL). B) Wild-type cells (PC6016) and the gal3Δ, gal4Δ, gal7Δ and gal10Δ mutants grown in YEP-GAL. C) P∼Hog1 levels in cells grown under the indicated conditions for 3 h with or without antimycin, ANT. D) Wild type (PC538) and the aco1Δ (PC3912), fum1Δ (PC6152), mdh1Δ (PC6153) and kgd1Δ (PC6155) and idh1Δ (PC6154) mutants were grown in galactose for 5.5 hrs. E) Wild-type cells (PC538), and the snf1Δ (PC560), mig1Δ (PC4843) and snf1Δ mig1Δ (PC6076) mutants were grown in YEP-GAL medium for 5.5 hrs.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4214603&req=5

pgen-1004734-g003: Role of increased metabolic respiration and Snf1p in activation of the HOG pathway.A) Immunoblot showing P∼Hog1p levels in cells grown in glucose (YEPD), galactose (YEP-GAL) or glucose and galactose (YEPD+2% GAL). B) Wild-type cells (PC6016) and the gal3Δ, gal4Δ, gal7Δ and gal10Δ mutants grown in YEP-GAL. C) P∼Hog1 levels in cells grown under the indicated conditions for 3 h with or without antimycin, ANT. D) Wild type (PC538) and the aco1Δ (PC3912), fum1Δ (PC6152), mdh1Δ (PC6153) and kgd1Δ (PC6155) and idh1Δ (PC6154) mutants were grown in galactose for 5.5 hrs. E) Wild-type cells (PC538), and the snf1Δ (PC560), mig1Δ (PC4843) and snf1Δ mig1Δ (PC6076) mutants were grown in YEP-GAL medium for 5.5 hrs.
Mentions: Glucose is the preferred carbon source in yeast [86], [87]. When glucose is abundant, yeast cells exclusively utilize that nutrient over non-preferred carbon sources like galactose. Glucose repression prevents the transport and utilization of other carbon sources [86], [88]–[90]. As shown above, glucose added to cells grown on galactose resulted in attenuation of the HOG response (Fig. 2F). To further test whether glucose prevents the HOG response to galactose, cells were grown in media containing both glucose and galactose as a carbon source. Under this condition, HOG pathway signaling was also attenuated (Fig. 3A). These experiments indicate that galactose metabolism is required for HOG pathway activation. Consistent with this possibility, mutants defective for galactose transport and utilization (Fig. 3B; gal3Δ, gal4Δ, gal7Δ, and gal10Δ [88], [90]–[93]) were defective for HOG pathway activation.

Bottom Line: Such cross-modulation was critical to optimize the differentiation response.The human fungal pathogen Candida albicans showed a similar regulatory circuit.Thus, an evolutionarily conserved regulatory axis links metabolic respiration and AMPK to Ire1p, which regulates a differentiation response involving the modulated activity of ERK and p38 MAPK pathways.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, State University of New York at Buffalo, Buffalo, New York, United States of America.

ABSTRACT
Evolutionarily conserved mitogen activated protein kinase (MAPK) pathways regulate the response to stress as well as cell differentiation. In Saccharomyces cerevisiae, growth in non-preferred carbon sources (like galactose) induces differentiation to the filamentous cell type through an extracellular-signal regulated kinase (ERK)-type MAPK pathway. The filamentous growth MAPK pathway shares components with a p38-type High Osmolarity Glycerol response (HOG) pathway, which regulates the response to changes in osmolarity. To determine the extent of functional overlap between the MAPK pathways, comparative RNA sequencing was performed, which uncovered an unexpected role for the HOG pathway in regulating the response to growth in galactose. The HOG pathway was induced during growth in galactose, which required the nutrient regulatory AMP-dependent protein kinase (AMPK) Snf1p, an intact respiratory chain, and a functional tricarboxylic acid (TCA) cycle. The unfolded protein response (UPR) kinase Ire1p was also required for HOG pathway activation in this context. Thus, the filamentous growth and HOG pathways are both active during growth in galactose. The two pathways redundantly promoted growth in galactose, but paradoxically, they also inhibited each other's activities. Such cross-modulation was critical to optimize the differentiation response. The human fungal pathogen Candida albicans showed a similar regulatory circuit. Thus, an evolutionarily conserved regulatory axis links metabolic respiration and AMPK to Ire1p, which regulates a differentiation response involving the modulated activity of ERK and p38 MAPK pathways.

Show MeSH