The intracellular NADH level regulates atrophic nonunion pathogenesis through the CtBP2-p300-Runx2 transcriptional complex

Wentao Zhang^1,2*, Ning Duan^2*, Qian Zhang³, Tao Song², Zhong Li², Xun Chen^2✉, Kunzheng Wang^1✉

1. Department of Orthopedics, the Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710005, Shaanxi, China;
2. Department of Orthopaedics, Hong-Hui Hospital, Xi'an Jiaotong University, Xi'an 710054, Shaanxi, China;
3. The second department of surgery room, Shaanxi Provincial Tumor Hospital, Xi'an 710061, Shaanxi, China.
* These authors contribute equally to this work.

Abstract

Atrophic nonunion, a complicated failure of fracture healing, is still obscure regarding its molecular pathological mechanisms. Carboxyl-terminal binding proteins (CtBPs), an NADH-sensitive transcriptional corepressor family, are involved in many diseases, such as cancer and inflammation. Here, we found that CtBP2, but not CtBP1, was significantly overexpressed in atrophic nonunion tissues compared to healthy controls. Using a mass spectrometry assay, we found that CtBP2 can form a complex with histone acetyltransferase p300 and transcription factor Runx2. The lower NADH level in atrophic nonunion tissues disrupted CtBP2 dimerization and enhanced the blockage of the accessibility of the p300-Runx2 complex to the promoters of a series of bone-related target genes, such as OSC, ALPL, COL1A1, IBSP, SPP1 and MMP13. The expression of these genes can be reversed by a forced increase in NADH with CoCl₂ treatment. In conclusion, our study revealed that NADH levels determine the expression of bone formation and development of related genes through affecting the dissociation or binding of CtBP2 to the p300-Runx2 complex. These results represent a conserved mechanism, by which CtBP2 serves as a NADH-dependent repressor of the p300-Runx2 transcriptional complex and thus affects bone formation.

Keywords: atrophic nonunion, CtBP2, p300, Runx2, NADH/NAD ratio

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How to cite this article:
Zhang W, Duan N, Zhang Q, Song T, Li Z, Chen X, Wang K. The intracellular NADH level regulates atrophic nonunion pathogenesis through the CtBP2-p300-Runx2 transcriptional complex. Int J Biol Sci 2018; 14(14):2023-2036. doi:10.7150/ijbs.28302. Available from http://www.ijbs.com/v14p2023.htm