Analysis On The Mechanism Of Endocrine Disrupting Chemicals And Preliminary Study On Simulation Method Based On Nuclear Receptor Dimerization Process

Endocrine disrupting chemicals(EDCs)can bind NR as a ligand by imitating or antagonizing natural hormones to form NR-ligand complex.The complex as homodimer or heterodimer in the nucleus,ultimately regulating transcription activity through the recruitment of coregulators.EDCs induce endocrine disrupting effects.There are a large number of known and unknown EDCs in the environment,however,the endocrine disrupting effects of most substances are ambiguous.Computer-aided virtual screening methods have gradually developed into an important substitutes for conventional in vivo and in vitro assays,which can be used for priority screening and reveal the interference mechanism of EDCs.However,the existing virtual screening studies mainly focus on ligand-receptor binding and coregulator recruitment,ignoring the dimerization process of nuclear receptors,resulting in low prediction accuracy.In this paper,two classical human nuclear receptors,estrogen receptor(ER)and androgen receptor(AR),are taken as research objects.Using computer-aided research methods such as molecular docking and classical molecular dynamics simulation(MD),EDCs was studied,and the interference mechanism of EDCs based on dimerization of nuclear receptor was analyzed.On the basis of ligand-receptor interaction,nuclear receptor dimerization,coregulator recruitment processes,a new virtual screening method was established to realize high-throughput recognition of EDCs based on molecular initiation mechanism,which improved the prediction accuracy.The main conclusions of this study are as follows:(1)Based on the ER crystal structure in PBD database,it was constructed into four interaction systems,namely ER monomer-ligand,ER monomer-ligand-coregulator,ER dimer-ligand and ER dimer-ligand-coregulator.The dimerization mechanism of EDCs was simulated by MD method.The ER monomer-ligand system simulated ligand-receptor binding process,ER monomer-ligand-coregulator system simulated ligand-receptor binding and cofactor recruitment process,ER dimer-ligand system simulated the process of ligand-receptor binding and dimerization,and ER dimer-ligand-coregulator system simulated the process of ligand-receptor binding,dimerization and coregulator recruitment process.Firstly,according to dynamic cross-correlation map(DCCM)analysis,it is found that dimerization process has obvious influence on the activity of EDCs.ER dimers show greater structural stability than monomers,which can be enhanced by recruiting coregulator.The key areas to regulate the dimerization process are the C-terminal of the 10thαhelix(H10)to the 11thαhelix(H11)region(H10-H11)and the 8th-9th loop region(L8-9).Furthermore,the influence mechanism of dimer interface on dimerization process was revealed.It was found that amino acids such as L509,R515 and K520 were the key amino acids causing dimerization by analyzing the interface of dimer.In addition,through the analysis of hydrogen bond occupancy ratio between coregulator and receptor,it was found that the conformational change of dimerization interface is transmitted to the C-terminal of H12,which leads to the differential recruitment of coregulators.On the basis of the above research,it is found that there is crosstalk among dimerization interface,ligand binding pocket and activation function region(AF2)of ER.Considering the three processes of ligand-receptor binding,nuclear receptor dimerization and coregulator recruitment,that is,estrogen activity simulation based on the whole process of molecular initiation,it has better correlation(R~2=0.7639)compared with ER monomer-coregulator system.(2)It is found that considering the dimerization process can significantly improve the prediction efficiency of estrogen effects,but it is not known whether it is still applicable in the face of various environmental pollutants.To study whether the above conclusions are applicable to environmental EDCs,bisphenols(BPs)and hydroxylated polybrominated diphenyl ethers(OH-PBDEs)are selected as typical environmental EDCs.The initial structure of ER was constructed,and the simulation and prediction studies including ligand-receptor binding,dimerization and coregulator recruitment were carried out.The results show that the system formed by EDCs and ER dimer is the most stable,and the recruitment of coregulator can further enhance the stability.The binding energy between ligand and ER-coregulator in the system of ER dimer-ligand-coregulator is highly correlated with estrogen efficacy.Based on this,a quantitative prediction model for estrogen effect of EDCs is established.Compared with monomer system,the prediction accuracy of estrogen effects improved from R~2=0.4679 to R~2=0.6218,and the prediction accuracy of anti-estrogen effects improved from R~2=0.4165 to R~2=0.7210.Therefore,it is necessary to consider the whole process of molecular initiation in the process of quantifying the activity of estrogen/anti-estrogen effects.(3)Furthermore,aiming at BPs and OH-PBDEs,the interference mechanism of environmental EDCs on the dimerization of AR is analyzed.The results showed that AR monomer-ligand-corepressor(COR)system can accurately predict the anti-androgen effects of compounds.Compared with AR dimer-ligand-COR system,the prediction ability was improved from R~2=0.0032 to R~2=0.6165.The results show that there are differences in dimerization interference mechanism between AR and ER.For AR,compounds with anti-androgen effects can directly bind to AR monomer or cause transcription inhibition by recruiting COR after binding.For the transcriptional activation of AR,ligand-receptor binding and coregulator recruitment are two important processes,dimerization is not necessary.