Molecular Mechanism Study Of IL-2 And Orexin System Based On Molecular Simulation Methods

As one of the three major killers,cancer threatens human health in the 21^st century.Because of insensitive to radiotherapy and chemotherapy,poor prognosis,and high mortality rate,metastatic renal cell carcinoma and malignant melanoma are considered as malignant tumors that difficult to be cured.IL-2 emerged as a key cytokine driving the activation,differentiation,function of T cells and NK cells.Attribute to its effect on regulate immune response,IL-2 becomes the first method of cancer immunotherapy.However IL-2 has lots of disadvantages in clinic therapy,it is important to find a safer and more efficient IL-2 substitution.The main goal of this thesis is to insight into the molecular mechanism of IL-2/IL-2R system through the method of computer-aided drug design?CADD?.In this project we successfully set up the conformational structures of IL-2 wild type and its mutant D10 with their receptors complexes through protein database searches.Compared the binding free energy and molecular interaction of each system,we summarized the key residues responsible for IL-2/D10 recognizing their receptors and we also found that IL-2 driving its biological activity via binding with IL-2R?.Then we built a chemical database consisting of 1,123 compounds,and a docking study was conducted to training the mode of chemical molecule with IL-2R?/IL-2R?.The top 1%in docking scores were reserved and we analyzed the interaction and mechanism of their binding.The analysis showed that residues R36,H128,and Y129 are the key residues for the chemicals binding to IL-2R?.It is disappointed that the chemicals couldn't have high affinity with IL-2R due to the poor hydrophobic surface.The method and results in this project laid solid foundations to the research and development of IL-2 mutant and chemical IL-2 substitution.The other independent part of this thesis is about Orexin system.It is estimated that more and more adults have sleep problems caused by pressure,fast-paced life.The cause notwithstanding,insomnia has a very high societal cost due to lost work time as well as increases risk of injury and related disease.Since its discovery in 1998,the orexin system consists of two GPCRs,OX1R and OX2R,and two neuropeptide agonists,OX-A and OX-B,has considered as a potential therapeutic target for the treatment of sleep/weak disorders.In other words,orexin receptor antagonists also become new strategy for the treatment of insomnia.However,there is only one dual-antagonist named Suvorexant obtained FDA's permission to put into market in 2014.In our study,the models of Orexin/OXR complex were established successfully and then we put our eyes on the molecular mechanism between orexin peptide OX-A and OX-B with their receptor OX1R and OX2R.We summarized the key residues contributed for orexin system recognition are Q85?Q87 in OX2R?,K280,and H303 as well as D162 and R281 which could form“Salt-bridge”with orexin.After that,the orexin antagonists obtained from references were docked into the binding site of OX1R and OX2R.The best conformation of each molecules was used to analyze ligand-receptor interactions.Residues Q85?Q87 in OX2R?,K280,and H303 are the key residues for antagonists binding with OXR.Based on the docking results,OXR antagonists'pharmacophore models were built.Each pharmacophore model composed of one hydrophobic feature,one aromatic feature,and two hydrogen bond acceptor feature.These conclusions and methods will provide theoretical guide for further study of Orexin/OXR system under the reality of absence of crystal structure reported,and also provided some hints for the design of new orexin receptor antagonists.