Background Sodium taurocholate co -transportering polypeptide (NTCP, SLC10A1 ) is a vital bile acid transporter and the functional receptor of hepatitis B and D virus. The oligomerization of NTCP is important for the structural study of its interaction with HBV preS1 peptide. Methods Recombinant NTCPs were expressed in Sf9 host cell using baculoviruses. Function of recombinant NTCP was verified by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) method. A quantitative fluorescence resonance energy transfer (FRET) method was established to analyze the interaction between NTCP wild type (WT) and mutants. Co-immunoprecipitation (Co-IP) was used to test the interaction between NTCP variants. Results Sub-cellular location of recombinant NTCPs varies with the modification of NTCP. Bands of monomer, dimer and oligomers were shown in gel analysis of NTCP. Significant FRET was observed between cyan florescence protein (CFP) tagged NTCP and yellow florescence protein (YFP) tagged NTCP. FRET efficiency between CFP- and YFP-NTCP S267F mutants was lower than WT. Co-IP results showed that S267F interacts with WT NTCP when co-expressed in cell. Conclusion Dimer is the predominant form of NTCP expressed in Sf9 when solubilized with detergent. FRET and Co-IP analysis support that NTCP forms oligomers in Sf9 cell. General significance Our results showed that NTCP formed oligomers in Sf9 cell. Meanwhile the FRET analysis of NTCP variants further elucidated the molecular mechanism of NTCP oligomerization.
Lei Ming,Lin Hui,Shi Deyao,Hong Pan,Song Hui,Herman Bomansaan,Liao Zhiwei,Yang Cao
Background Intervertebral disc degeneration (IVDD) is the major cause of low-back pain. Histone deacetylase 9 (HDAC9) was dramatically decreased in the degenerative nucleus pulposus (NP) samples of patients with intervertebral disc degeneration (IVDD) according to bioinformatics analysis of Gene Expression Omnibus (GEO) GSE56081 dataset. This study aims to investigate the role of HDAC9 in IVDD progression.Methods The contribution of HDAC9 to the progression of IVDD was assessed using HDAC9 knockout (HDAC9KO) mice and NP-targeted HDAC9-overexpressing mice by IVD injection of adenovirus-mediated HDAC9 under a Col2a1 promoter. Magnetic resonance imaging (MRI) and histological analysis were used to examine the degeneration of IVD. NP cells were isolated from mice to investigate the effects of HDAC9 on apoptosis and viability. mRNA-seq and coimmunoprecipitation/mass spectrometry (co-IP/MS) analysis were used to analyze the HDAC9-regulated factors in the primary cultured NP cells.Results HDAC9 was statistically decreased in the NP tissues in aged mice. HDAC9KO mice spontaneously developed age-related IVDD compared with wild-type (HDAC9WT) mice. In addition, overexpression of HDAC9 in NP cells alleviated IVDD symptoms in a surgically-induced IVDD mouse model. In an in vitro assay, knockdown of HDAC9 inhibited cell viability and promoted cell apoptosis of NP cells, and HDAC9 overexpression had the opposite effects in NP cells isolated from HDAC9KO mice. Results of mRNA-seq and co-IP/MS analysis revealed the possible proteins and signaling pathways regulated by HDAC9 in NP cells. RUNX family transcription factor 3 (RUNX3) was screened out for further study, and RUNX3 was found to be deacetylated and stabilized by HDAC9. Knockdown of RUNX3 restored the effects of HDAC9 silencing on NP cells by inhibiting apoptosis and increasing viability.Conclusion Our results suggest that HDAC9 plays an important role in the development and progression of IVDD. It might be required to protect NP cells against the loss of cell viability and apoptosis by inhibiting RUNX3 acetylation and expression during IVDD. Together, our findings suggest that HDAC9 may be a potential therapeutic target in IVDD.Graphical Abstract
Zhenxiu Liu,Lin Chen,Mingyun Chen,Lang Linghu,Zhihua Liao,Min Chen,Guowei Wang
Background Farnesoid X receptor (FXR) is a vital receptor for bile acids and plays an important role in the treatment of cholestatic liver disease. In addition to traditional bile acid-based steroidal agonists, synthetic alkaloids are the most commonly reported non-steroidal FXR agonists. Sarmentol H is a nor-sesquiterpenoid obtained from Sedum sarmentosum Bunge, and in vitro screening experiments have shown that it might be related to the regulation of the FXR pathway in a previous study. Purpose To investigate the therapeutic effects of sarmentol H on cholestasis and to determine whether sarmentol H directly targets FXR to mitigate cholestasis. Furthermore, this study aimed to explore the key amino acid residues involved in the binding of sarmentol H to FXR through site-directed mutagenesis. Methods An intrahepatic cholestasis mouse model was established to investigate the therapeutic effects of sarmentol H on cholestasis. In vitro experiments, including Co-Ip and FXR-EcRE-Luc assays, were performed to assess whether sarmentol H activates FXR by recruiting the receptor coactivator SRC1. CETSA, SIP, DARTS, and ITC were used to determine the binding of sarmentol H to FXR protein. The key amino acid residues for sarmentol H binding to FXR were analyzed by molecular docking and site-directed mutagenesis. Finally, we conducted in vivo experiments on wild-type and Fxr −/− mice to further validate the anticholestatic target of sarmentol H. Results Sarmentol H had significant ameliorative effects on the pathological conditions of cholestatic mice induced with ANIT. In vitro experiments suggested that it is capable of activating FXR and regulating downstream signaling pathways by recruiting SRC1. The target validation experiments showed that sarmentol H had the ability to bind to FXR as a ligand (K D = 2.55 μmol/L) and enhance the stability of its spatial structure. Moreover, site-directed mutagenesis revealed that THR292 and TYR365 were key binding sites for sarmentol H and FXR. Furthermore, knockout of the Fxr gene resulted in a significantly higher degree of ANIT-induced cholestatic liver injury than that in wild-type cholestatic mice, and the amelioration of cholestasis or regulatory effects on FXR downstream genes by sarmentol H also disappeared in Fxr −/− cholestatic mice. Conclusion Sarmentol H is an FXR agonist. This is the first study to show that it exerts a significant therapeutic effect on cholestatic mice, and can directly bind to FXR and activate it by recruiting the coactivator SRC1.
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