PHYSICAL CHEMISTRY B一 pubs. acs. org/JPCB Molecular Insights into the D1R Agonist and d2R/D3R Antagonist Effects of the Natural Product (-) -Stepholidine: Molecular Modeling and dynamics simulations Bian.ts Wei Li. t, peng Du, Kun Qian Yu, *+ and Wei Fu*+,? Department of Medicinal Chemistry Key Laboratory of Smart Drug Delivery, Ministry of Education PLA, School of Pharmacy, Fudan University, Shanghai 201203, China Drug Discovery and Design Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China S Supporting Information ABSTRACT:(-)-Stepholidine(1SPD), an active ingredier of the Chinese herb Stephania, is the first compound found to ave a dual function as a dopamine receptor DI agonist and ary dynamical beh of DI and d2R and their interaction modes with -spd were a investigated in our previous study. Recently, the pharmaco- logical effect of 1-SPD on D3R was elucidated as an antagonist. This new discovery in combination with the explosion of structural biology in GPCR superfamily prompted us to I-SPD perform a more comprehensive investigation on the special pharmacological profiles of 1-SPD on dopamine receptors. In this study, the integration of homology modeling, automated molecular docking, and MD simulations was used to probe the agonistic and antagonistic mechanism of 1-SPD on DIR, D2R, and D3R. Our analyses showed that hydrogen bonding of the hydroxyl group on the d ring of I-SPD with side chain of N6.55 which, in combination with hydrophobic stacking between 13.40, F6.44 and w6.48, is the key feature to mediate the agonist effect of 1-SPD on DiR, whereas the absence of hydrophobic stacking between 13.40, F6.44, and W6. 48 in D2R and D3R excludes receptor activation. Finally, the agonistic and antagonistic mechanisms of 1-SPD and an activation model of dir were proposed on the basis of these findings. The present study could guide future experimental works on these receptors and has the significance to the design of functionally selective drugs targeting dopamine receptors. ■| NTRODUCTION these inactive-state receptors as template is also problematic. G-protein-coupled receptors( GPCRs)are the largest family of The newly available active-state structures of BAR, P1 AR, and integral membrane proteins that mediate most of physiological AzA receptor thus provide a solid basis for the elucidation of the and environmental conformational changes associated with agonist binding esponses to hormones, neurotransmitters, and environmental stimulants. GPCRs constitute the largest class of therapeutic Dopamine(DA), the endogenous ligand of dopaminergic targets as evidenced by the fact that at least one-fourth of drugs neurotransmission systems, has been associated with many on the market exert their therapeutic activity by modulating physiological functions such as fine movement coordination, hodopsin-like GPCRs. In the past 3 years, there were cognition, and emotion. DA exerts its effects by activating five remarkable advances in the crystallography of G-protein- distinct dopamine receptors(Drs) which belong to the GPCR oupled receptors (GPCRs). Highlights have included the superfamily and are classified into two subfamilies:D1-like characterization of the crystal structures of antagonist-bound (DIR and DSR)and D2-like(D2r, D3R, and D4R) based on and agonist-bound GPCRs: the human B2 adrenergic receptor pharmacological and functional characteristics. It has bee (2AR),- the turkey B,AR,the human A2A adenosine established that DRs are primary targets of antipsychotic drugs receptor,",the human chemokine receptor CXCR4, and the used to treat psychomotor diseases such as schizophre human dopamine D3 receptor. The availability of such high debilitating mental illness which affects 0.5-1.5% of the resolution crystal structures can greatly help to guide the worldwide population. The pathogenesis of schizophrenia is structure-based GPCR drug discovery. However, with the suggested to be related to dysfunction of the DiR in the medial inactive-state structures of B,AR, PAR, and axa receptor medicinal chemists could probably only be able to develop Received: May ligands that stabilize the inactive conformation. The agonisti Revised: 122 nechanism of GPCRs based on homology modeling taking Published: June 15, 2012 ACS Publications 2012 American Chemical Society 121 dx. dolora/10.1021/p30492351Phys. Chem. 62012116,8121-8130Molecular Insights into the D1R Agonist and D2R/D3R Antagonist Effects of the Natural Product (−)-Stepholidine: Molecular Modeling and Dynamics Simulations Bian Li,†,§ Wei Li,†,§ Peng Du,†,§ Kun Qian Yu,*,‡ and Wei Fu*,† † Department of Medicinal Chemistry & Key Laboratory of Smart Drug Delivery, Ministry of Education & PLA, School of Pharmacy, Fudan University, Shanghai 201203, China ‡ Drug Discovery and Design Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China *S Supporting Information ABSTRACT: (−)-Stepholidine (l-SPD), an active ingredient of the Chinese herb Stephania, is the first compound found to have a dual function as a dopamine receptor D1 agonist and D2 antagonist. The preliminary dynamical behaviors of D1R and D2R and their interaction modes with l-SPD were investigated in our previous study. Recently, the pharmaco￾logical effect of l-SPD on D3R was elucidated as an antagonist. This new discovery in combination with the explosion of structural biology in GPCR superfamily prompted us to perform a more comprehensive investigation on the special pharmacological profiles of l-SPD on dopamine receptors. In this study, the integration of homology modeling, automated molecular docking, and MD simulations was used to probe the agonistic and antagonistic mechanism of l-SPD on D1R, D2R, and D3R. Our analyses showed that hydrogen bonding of the hydroxyl group on the D ring of l-SPD with side chain of N6.55 which, in combination with hydrophobic stacking between I3.40, F6.44 and W6.48, is the key feature to mediate the agonist effect of l-SPD on D1R, whereas the absence of hydrophobic stacking between I3.40, F6.44, and W6.48 in D2R and D3R excludes receptor activation. Finally, the agonistic and antagonistic mechanisms of l-SPD and an activation model of D1R were proposed on the basis of these findings. The present study could guide future experimental works on these receptors and has the significance to the design of functionally selective drugs targeting dopamine receptors. ■ INTRODUCTION G-protein-coupled receptors (GPCRs) are the largest family of integral membrane proteins that mediate most of physiological responses to hormones, neurotransmitters, and environmental stimulants. GPCRs constitute the largest class of therapeutic targets as evidenced by the fact that at least one-fourth of drugs on the market exert their therapeutic activity by modulating rhodopsin-like GPCRs.1 In the past 3 years, there were remarkable advances in the crystallography of G-protein￾coupled receptors (GPCRs). Highlights have included the characterization of the crystal structures of antagonist-bound and agonist-bound GPCRs: the human β2 adrenergic receptor (β2AR),2−5 the turkey β1AR,6,7 the human A2A adenosine receptor,8,9 the human chemokine receptor CXCR4,10 and the human dopamine D3 receptor.11 The availability of such high￾resolution crystal structures can greatly help to guide the structure-based GPCR drug discovery. However, with the inactive-state structures of β2AR, β1AR, and A2A receptor, medicinal chemists could probably only be able to develop ligands that stabilize the inactive conformation. The agonistic mechanism of GPCRs based on homology modeling taking these inactive-state receptors as template is also problematic. The newly available active-state structures of β2AR, β1AR, and A2A receptor thus provide a solid basis for the elucidation of the conformational changes associated with agonist binding. Dopamine (DA), the endogenous ligand of dopaminergic neurotransmission systems, has been associated with many physiological functions such as fine movement coordination, cognition, and emotion. DA exerts its effects by activating five distinct dopamine receptors (DRs) which belong to the GPCR superfamily and are classified into two subfamilies: D1-like (D1R and D5R) and D2-like (D2R, D3R, and D4R) based on their pharmacological and functional characteristics. It has been established that DRs are primary targets of antipsychotic drugs used to treat psychomotor diseases such as schizophrenia, a debilitating mental illness which affects 0.5−1.5% of the worldwide population.12 The pathogenesis of schizophrenia is suggested to be related to dysfunction of the D1R in the medial Received: May 21, 2012 Revised: June 14, 2012 Published: June 15, 2012 Article pubs.acs.org/JPCB © 2012 American Chemical Society 8121 dx.doi.org/10.1021/jp3049235 | J. Phys. Chem. B 2012, 116, 8121−8130