Identification of a novel melatonin-binding nuclear receptor: vitamin D receptor.
J Pineal Res. 2019 Oct 20:e12618. doi: 10.1111/jpi.12618.
Fang N1, Hu C2, Sun W2, Xu Y2, Gu Y1, Wu L1, Peng Q1, Reiter RJ3, Liu L1.
- 1 Department of Trauma Orthopaedics, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China.
- 2 State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.
- 3 Department of Cellular & Structural Biology, UT Health Science Center, Floyd Curl Drive, 7703, San Antonio, Texas, USA.
There have been some indications of interactions between Melatonin and Vitamin D
Previous studies confirmed that melatonin regulates Runx2 expression but the mechanism is unclear. There is a direct interaction between Runx2 and the vitamin D receptor (VDR). Herein, we observed a direct interaction between melatonin and the VDR but not Runx2 using isothermal titration calorimetry. Furthermore, this direct binding was detected only in the C-terminal ligand binding domain (LBD) of the VDR but not in the N-terminal DNA binding domain (DBD) or the hinge region. Spectrophotometry indicated that melatonin and vitamin D3 (VD3) had similar uptake rates, but melatonin's uptake was significantly inhibited by VD3 until the concentration of melatonin was obviously higher than that of VD3 in a preosteoblastic cell line MC3T3-E1. GST pull down and yeast two-hybrid assay showed that the interactive smallest fragments were on the 319-379 position of Runx2 and the N-terminus 110-amino acid DBD of the VDR. Electrophoretic mobility shift assay (EMSA) demonstrated that Runx2 facilitated the affinity between the VDR and its specific DNA substrate, which was further documented by a fluorescent EMSA assay where Cy3 labeled Runx2 co-localized with the VDR-DNA complex. Another fluorescent EMSA assay confirmed that the binding of the VDR to Runx2 was significantly enhanced with an increasing concentrations of the VDR, especially in the presence of melatonin; it was further documented using a co-immunoprecipitation assay that this direct interaction was markedly enhanced by melatonin treatment in the MC3T3-E1 cells. Thus, the VDR is a novel melatonin-binding nuclear receptor, and melatonin indirectly regulates Runx2 when it directly binds to the LBD and the DBD of the VDR, respectively.
Wikipedia
Runt-related transcription factor 2 also known as core-binding factor subunit alpha-1 is a protein that in humans is encoded by the RUNX2 gene. RUNX2 is a key transcription factor associated with osteoblast differentiation.