Unfolded Protein Response Pathway Coupled to Activation of Slt2 MAP Kinase Pathway in the Budding Yeast Saccharomyces cerevisiae
Mentor 1
Madhusudan Dey
Location
Union Wisconsin Room
Start Date
5-4-2019 1:30 PM
End Date
5-4-2019 3:30 PM
Description
Noelle Regina Klitzke, Chandrima Ghosh, Anthony Thomas Pulvino, and Madhusudan Dey
Proteins are workhorses in our body. They must fold into the proper shape to do their biological function. Folding occurs in the cytoplasm or inside the endoplasmic reticulum (ER). If proteins misfold or unfold inside the ER, a condition known as the “ER stress”, cells activate a network of signaling pathways, collectively known as the unfolded protein response (UPR). UPR mitigate ER stress and is conserved from yeast to human. A simple assay to identify a candidate protein essential for UPR in the budding yeast Saccharomyces cerevisiae is that the respective protein deletion mutant is sensitivity to an ER stressor tunicamycin (an inhibitor of N-linked protein glycosylation) or dithiothreitol (an inhibitor of disulfide bond formation). Combined with this assay, the adaptive molecular response of an active UPR includes up-regulation of a transcription factor Hac1 in yeast cells or Xbp1 in human cells. Hac1/Xbp1 in turn actives the expressions of protein foldases or molecular chaperones to enhance the protein folding capacity of cells. We found that yeast cell lacking the mitogen-activated protein (MAP) kinase Slt2 was severely sensitive to tunicamycin. Consistently, our molecular studies showed that the Hac1 protein expression was significantly decreased in the slt2 delta strain. In contrast, we found that the Hac1-induced expression of a molecular chaperone Kar2 remained unchanged in the slt2 delta strain. These data suggest that the reduced level of Hac1 protein was sufficient to activate the expression of Kar2, but to fully activate the UPR. While the Slt2 MAP kinase is known to regulate the cell wall integrity (CWI) signaling, our results demonstrate a functional link between the UPR and the MAP kinase signaling pathways.
Unfolded Protein Response Pathway Coupled to Activation of Slt2 MAP Kinase Pathway in the Budding Yeast Saccharomyces cerevisiae
Union Wisconsin Room
Noelle Regina Klitzke, Chandrima Ghosh, Anthony Thomas Pulvino, and Madhusudan Dey
Proteins are workhorses in our body. They must fold into the proper shape to do their biological function. Folding occurs in the cytoplasm or inside the endoplasmic reticulum (ER). If proteins misfold or unfold inside the ER, a condition known as the “ER stress”, cells activate a network of signaling pathways, collectively known as the unfolded protein response (UPR). UPR mitigate ER stress and is conserved from yeast to human. A simple assay to identify a candidate protein essential for UPR in the budding yeast Saccharomyces cerevisiae is that the respective protein deletion mutant is sensitivity to an ER stressor tunicamycin (an inhibitor of N-linked protein glycosylation) or dithiothreitol (an inhibitor of disulfide bond formation). Combined with this assay, the adaptive molecular response of an active UPR includes up-regulation of a transcription factor Hac1 in yeast cells or Xbp1 in human cells. Hac1/Xbp1 in turn actives the expressions of protein foldases or molecular chaperones to enhance the protein folding capacity of cells. We found that yeast cell lacking the mitogen-activated protein (MAP) kinase Slt2 was severely sensitive to tunicamycin. Consistently, our molecular studies showed that the Hac1 protein expression was significantly decreased in the slt2 delta strain. In contrast, we found that the Hac1-induced expression of a molecular chaperone Kar2 remained unchanged in the slt2 delta strain. These data suggest that the reduced level of Hac1 protein was sufficient to activate the expression of Kar2, but to fully activate the UPR. While the Slt2 MAP kinase is known to regulate the cell wall integrity (CWI) signaling, our results demonstrate a functional link between the UPR and the MAP kinase signaling pathways.
