Theoretical Studies On Adrenergic Receptor Agonists And Antagonists

Objective:Adrenergic receptors are a class of the G protein-coupled receptors.The members of this receptor class mediate a wide variety of physiological responses,including vasodilatation,vasoconstriction,heart rate modulation,regulation of lipolysis and blood clotting.Therefore,adrenergic receptors have been found to play a very important role in physiological and pharmacological modulation and have received wide attention.Thus,these diverse and important functions make the adrenergic receptors a tempting pharmaceutical target.The aim of this research is to develop the theoretical methods which are used to identify the adrenergic receptor agonists and antagonists.And it is hope that these theoretical methods can provide a theoretical basis for the structure-based drug design of adrenergic receptor agonists and antagonists.Methods:The amino acidic sequences of the human al A,α1B,α1D,α2A,α2B,α2C,β1 and β3 adrenergic receptors were retrieved from PubMed database.The models of the above subtype adrenergic receptors were built by homology modeling method,using the X-ray structure of human β2 adrenergic receptor as template.The conservative regions,loop regions and side chains of the above subtype adrenergic receptors were achieved using ORCHESTRAR approach,which was embedded into SYBYL8.0 software packages.The resultant homology models were then optimized using the Schrodinger Suite 2009 Update 1 software packages and PROCHECK program was used to access the stereochemical parameters of the above structures.Several known agonists and antagonists were then docked into the active site of adrenergic receptors using Glide,which was embedded into Schrodinger Suite 2009 Update 1 software package.And the differences between agonist and antagonist binding characteristics were investigated to establish the theoretical methods.The reliability and specificity of the theoretical methods were then tested by negative drugs and negative receptors.In molecular dynamics simulation studies,the al A andβ3 receptor complexes were inserted into the DPPC bilayer.The whole systems were then subjected to carry out molecular dynamics simulation by Desmond software package.The complexes were firstly equilibrated for 4ns under NPT condition.Finally,5 ns molecular dynamics simulations were performed under NPT condition.Results:The predicted 3D structure of adrenergic receptors share high homology with the template.PROCHECK program shows that resultant homology model have acceptable stereochemical parameters.The docking models of agonists and antagonists appear to provide agreement with site directed mutagenesis results.Molecular docking studies show that agonists mainly occupy PI site,which plays crucial role in activation of adrenergic receptor.But antagonists mainly occupy extracellular loop(PII site).Most agonists can at least exhibit hydrogen bonds with above three conservative residues,while the requirements of hydrogen bonds of antagonists are not as strict as agonists.The negative drugs and negative receptors tests show that the above theoretical methods are reliable and specific.Key atom-to-atom distances as well as hydrogen bonds between ligands and three conservative residues were investigated in molecular dynamics simulation.The molecular dynamics simulation results are consist with molecular docking studies.And it can indicate that the theoretical standards are rational.Moreover,the molecular dynamics simulation shows that alA and β3 agonist-receptor complexes have"activated conformation" and "non-unactivated conformation".But the antagonist-receptor complexes do not have that conformation changes.Conclusions:In this research,adrenergic receptors which were modeled using homology modeling method are rational.The "agonist-bound" models and"antagonist-bound" models are agreement with site directed mutagenesis results.Molecular docking and molecular dynamics simulation studies show that agonists and antagonists can occupy different sites of adrenergic receptors.And the requirements of hydrogen bonds for agonists and antagonists are also different.Agonists can exhibit hydrogen bonds between three conservative residues,but antagonists may not exhibit hydrogen bonds with three conservative residues.The knowledge of this research can be used for virtual screening to discover more novel potential agonists and antagonists for adrenergic receptors.