Variable protein homeostasis in housekeeping and non-housekeeping pathways under mycotoxins stress

Abstract

Transcript levels are the primary factor determining protein levels, but for the majority of genes, fold changes in transcript levels are larger than the corresponding changes in protein levels, a phenomenon that is termed "protein homeostasis". However, this phenomenon is not well characterized in the context of environmental changes. In this study, we sequenced the entire transcriptome and proteome of chicken primary hepatocytes administered three mycotoxin treatments Aflatoxin B₁ (AFB₁), Ochoratoxin A (OTA) and Zearalenone (ZEN). Each mycotoxin induced unique set of differential expressed transcripts and proteins, suggesting variable cytotoxicity and biochemical action in cell. We found a weak positive correlation between transcript and protein changes, and the transcript changes were higher than the protein changes. Furthermore, we observed pathway-specific protein homeostasis pattern under mycotoxin stress. Specifically, the "Metabolism", "Transcription" and "Translation" pathways (housekeeping pathways) showed lower fold changes in protein/mRNA levels than non-housekeeping pathways such as "Cell growth and death" and "Immune system". Protein molecular weight had a weak negative effect on protein production, and this effect was stronger for non-housekeeping pathways. Overall, we hypothesize housekeeping pathways maintain stable protein production for baseline cellular function, whereas non-housekeeping pathways is associated with the fitness response to environmental stress.

Figure 1

Chicken hepatocytes cell viability from MTT assay under (A) AFB₁, (C) OTA and (E) ZEN administration. Each bar represents mean cell viability from five independent experiments with standard deviation. The gradient test for CYP1A4, CYP2D20 and CYP3A37 genes expression under different (B) AFB₁, (D) OTA and (F) ZEN concentration and duration. Each bar represents mean fold changes from three independent experiments with standard deviation.

Figure 2

Ven diagram plot for the (A) up-regulated and (B) down-regulated transcripts and (C) up-regulated and (D) down-regulated proteins among three mycotoxins.

Figure 3

Pearson’s correlation between transcript and protein level changes for AFB₁, OTA and ZEN. Transcript and protein changes are calculated by comparing mycotoxin treated samples and control samples.

Figure 4

Pearson’s correlation between transcript and protein level changes for four representative KEGG pathways in OTA treated samples. (A) Carbohydrate metabolism; (B) Nucleotide metabolism; (C) Cell growth and death; and (D) Immune system. Transcript and protein changes are calculated by comparing mycotoxin treated samples and control samples.

Figure 5

Pearson’s correlation between protein molecular weight and protein level changes under (A) AFB₁, (B) OTA and (C) ZEN treatment.