Gene expression profile of MAP kinase PTC1 mutant exposed to Aflatoxin B1: dysfunctions of gene expression in glucose utilization and sphingolipid metabolism

Abstract

Aflatoxin B 1 (AFB 1 ) is a harmful and cancer-causing mycotoxin generated by Aspergillus flavus. Its mechanism of toxicity has not been fully clarified and further research is required. In this study, we attempted to further clarify aflatoxin B 1 toxicity using the results of S. cerevisiae gene expression analysis. In a Ser/Thr phosphatase 2C disruptant (ptc1Δ) with weakened activity of anti-toxic components (cell wall and membrane), the addition of low concentrations of sodium dodecyl sulfate resulted in elevated susceptibility to AFB 1 . From the microarray results, expression changes in DNA synthesis or repair, sphingolipid metabolism, glucose metabolism, and cell wall-related genes were well detected. Our results indicate that AFB 1 causes sphingolipid metabolism disorder, leading to dysfunction in signal secretion and inhibition of efficient glucose metabolism, which supplies the materials for cell wall proteins and cellular components, resulting in repression of the stress response to external toxicants.

Gene expression profile of MAP kinase PTC1 mutant exposed to deoxynivalenol

“…We employed a PTC1 disruptant (ptc1) in this study, but detected almost no MAPK cascade genes. The result of this study indicated that the PTC1 mutation does not lead to noticeable changes in gene expression of MAPK cascades, and this trend corresponds to a previous study [20]. However, in both studies, CAT8 and gluconeogenesis-related genes regulated downstream of MAPK [31] were highly induced.…”

“…Gasch [21][22] reported two types of gene expression, which are related to cytotoxicity and DNA damage; the latter corresponds to our previous report of AFB 1 [20]. In this study, we focused on damage by DON under the same conditions reported for AFB 1 .…”

“…Table 1 shows the result of categorizing of functional genes; many of the detected genes listed were observed in several categories. Excluding the protein synthesis, the detection ratio between each cluster is roughly similar, although the detection numbers were smaller than that of the previous study about AFB 1 [20]. The genes that were categorized as protein synthesis were an especially small proportion of those counted in the AFB 1 study.…”

“…Ceramide synthesis inhibition causes sphingolipid depletion on the plasma membrane, and results in the dysfunction of folate transport [35]. Therefore, a sufficient effect can be expected, even in the AFB 1 condition in which gene repression of sphingolipid metabolism was observed [20]. It might be especially effective for animals that cannot produce folic acid.…”

“…Total RNA (500 ng for each sample) was processed for target preparation using a GeneChip 3' IVT Express kit (Affymetrix, Santa Clara, CA, USA) according to the manufacturer's instructions. Microarray hybridization was performed using a GeneChip Yeast Genome 2.0 array (Affymetrix), according to the procedure described in a previous study [20]. After normalization of the chip-set data using the MAS5 algorithm, three replicates of each treated condition were combined and summarized to single expression values.…”