Insulin determines the effects of TGF-beta on HNF4alpha transcription and epithelial-to-mesenchymal transition in hepatocytes

Feng, R.; Tong, C.; Lin, T.; Liu, H.; Shao, C.; Li, Y.; Sticht, C.; Kan, K.; Li, X.; Liu, R.; Wang, S.; Munker, S.; Niess, H.; Meyer, C.; Liebe, R.; Ebert, M. P.; Dooley, S.; Wang, H.; Ding, H.; Weng, H.-L.

doi:10.1101/2023.01.12.523351

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bioRxiv · 10.1101/2023.01.12.523351

Insulin determines the effects of TGF-beta on HNF4alpha transcription and epithelial-to-mesenchymal transition in hepatocytes

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Abstract

To date, epithelial-to-mesenchymal transition (EMT) has been observed in cultured hepatocytes, but not in vivo. TGF-{beta} is supposed to initiate EMT in hepatocytes by inhibiting HNF4 through the SMAD2/3 complex. We report that TGF-{beta} does not directly inhibit HNF4, but contributes to its transcriptional regulation by SMAD2/3 recruiting acetyltransferase CBP/p300 to the HNF4 promoter. The recruitment of CBP/p300 is indispensable for C/EBPa binding, another essential requirement for constitutive HNF4 expression in hepatocytes. In contrast to the observed induction of HNF4, SMAD2/3 inhibits C/EBP transcription. Therefore, long-term TGF-{beta} incubation results in C/EBP depletion, which abrogates HNF4 expression. Intriguingly, SMAD2/3 inhibitory binding to the C/EBP promoter is abolished by insulin. Thus, maintaining a high insulin concentration in culture medium ensures constitutive HNF4 and thereby prevents TGF-{beta}-induced hepatocyte EMT. Furthermore, insulin inhibits TGF-{beta}-induced SMAD2/3 binding to the promoters of core EMT transcription factors e.g., SNAI1. SNAI1 transcription requires both SMAD2/3 and FOXO1 in nuclei. Insulin inhibits SNAI1 transcription through impeding SMAD2/3 binding to its promoter and inducing FOXO1 phosphorylation. Hence, insulin is the key factor that prevents TGF-{beta}-induced EMT in hepatocytes.

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Feng, R., Tong, C., Lin, T., Liu, H., Shao, C., Li, Y., Sticht, C., Kan, K., Li, X., Liu, R., Wang, S., Munker, S., Niess, H., Meyer, C., Liebe, R., Ebert, M. P., Dooley, S., Wang, H., Ding, H., Weng, H.-L.. 2023-01-12. Insulin determines the effects of TGF-beta on HNF4alpha transcription and epithelial-to-mesenchymal transition in hepatocytes. https://doi.org/10.1101/2023.01.12.523351

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