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Börzsei R, Zsidó BZ, Bálint M, Helyes Z, Pintér E, Hetényi C. Exploration of Somatostatin Binding Mechanism to Somatostatin Receptor Subtype 4. Int J Mol Sci 2022; 23:ijms23136878. [PMID: 35805885 PMCID: PMC9266823 DOI: 10.3390/ijms23136878] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 06/15/2022] [Accepted: 06/16/2022] [Indexed: 02/04/2023] Open
Abstract
Somatostatin (also named as growth hormone-inhibiting hormone or somatotropin release-inhibiting factor) is a regulatory peptide important for the proper functioning of the endocrine system, local inflammatory reactions, mood and motor coordination, and behavioral responses to stress. Somatostatin exerts its effects via binding to G-protein-coupled somatostatin receptors of which the fourth subtype (SSTR4) is a particularly important receptor mediating analgesic, anti-inflammatory, and anti-depressant effects without endocrine actions. Thus, SSTR4 agonists are promising drug candidates. Although the knowledge of the atomic resolution-binding modes of SST would be essential for drug development, experimental elucidation of the structures of SSTR4 and its complexes is still awaiting. In the present study, structures of the somatostatin–SSTR4 complex were produced using an unbiased, blind docking approach. Beyond the static structures, the binding mechanism of SST was also elucidated in the explicit water molecular dynamics (MD) calculations, and key binding modes (external, intermediate, and internal) were distinguished. The most important residues on both receptor and SST sides were identified. An energetic comparison of SST binding to SSTR4 and 2 offered a residue-level explanation of receptor subtype selectivity. The calculated structures show good agreement with available experimental results and indicate that somatostatin binding is realized via prerequisite binding modes and an induced fit mechanism. The identified binding modes and the corresponding key residues provide useful information for future drug design targeting SSTR4.
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Affiliation(s)
- Rita Börzsei
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, 7624 Pécs, Hungary; (R.B.); (B.Z.Z.); (M.B.); (Z.H.); (E.P.)
- János Szentágothai Research Centre & Centre for Neuroscience, University of Pécs, 7624 Pécs, Hungary
| | - Balázs Zoltán Zsidó
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, 7624 Pécs, Hungary; (R.B.); (B.Z.Z.); (M.B.); (Z.H.); (E.P.)
- János Szentágothai Research Centre & Centre for Neuroscience, University of Pécs, 7624 Pécs, Hungary
| | - Mónika Bálint
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, 7624 Pécs, Hungary; (R.B.); (B.Z.Z.); (M.B.); (Z.H.); (E.P.)
- János Szentágothai Research Centre & Centre for Neuroscience, University of Pécs, 7624 Pécs, Hungary
| | - Zsuzsanna Helyes
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, 7624 Pécs, Hungary; (R.B.); (B.Z.Z.); (M.B.); (Z.H.); (E.P.)
- János Szentágothai Research Centre & Centre for Neuroscience, University of Pécs, 7624 Pécs, Hungary
- Algonist Gmbh, 1030 Vienna, Austria
- PharmInVivo Ltd., 7624 Pécs, Hungary
| | - Erika Pintér
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, 7624 Pécs, Hungary; (R.B.); (B.Z.Z.); (M.B.); (Z.H.); (E.P.)
- János Szentágothai Research Centre & Centre for Neuroscience, University of Pécs, 7624 Pécs, Hungary
- Algonist Gmbh, 1030 Vienna, Austria
- PharmInVivo Ltd., 7624 Pécs, Hungary
| | - Csaba Hetényi
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, 7624 Pécs, Hungary; (R.B.); (B.Z.Z.); (M.B.); (Z.H.); (E.P.)
- János Szentágothai Research Centre & Centre for Neuroscience, University of Pécs, 7624 Pécs, Hungary
- Correspondence:
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Nagarajan SK, Babu S, Kulkarni SA, Vadivelu A, Devaraju P, Sohn H, Madhavan T. Understanding the influence of lipid bilayers and ligand molecules in determining the conformational dynamics of somatostatin receptor 2. Sci Rep 2021. [PMID: 33828200 DOI: 10.1038/s41598‐021‐87422‐5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Somatostatin receptor 2 (SSTR2) is a G-protein coupled receptor (GPCR) that controls numerous cellular processes including cell-to-cell signaling. In this study, we report how the lipid and ligand molecules influence the conformational dynamics of the membrane-bound SSTR2. Molecular simulations of different holo and apoenzyme complexes of SSTR2 in the presence and absence of a lipid bilayer were performed, observed, and correlated with previously reported studies. We identified the important SSTR2 residues that take part in the formation of the SSTR2-ligand complex. On analyzing the molecular simulation trajectories, we identified that the residue D3.32 is crucial in determining the bioactive conformation of SSTR2 ligands in the binding site. Based on the results, we suggest that designing a novel SSTR2 ligand with an H-bond donor group at the R1 position, and hydrophobic groups at R2 and R3 might have higher activity and SSTR2-selectivity. We analyzed the simulated systems to identify other important structural features involved in SSTR2-ligand binding and to observe the different conformational changes that occur in the protein after the ligand binding. Additionally, we studied the conformational dynamics of N- and C-terminal regions of SSTR2 in the presence and absence of the lipid bilayer. Both the systems were compared to understand the influence of lipid molecules in the formation of secondary structural domains by these extracellular regions. The comparative study revealed that the secondary structural elements formed by C-terminal residues in presence of lipid molecules is crucial for the functioning of SSTR2. Our study results highlight the structural complexities involved in the functioning of SSTR upon binding with the ligands in the presence and absence of lipid bilayer, which is essential for designing novel drug targets.
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Affiliation(s)
- Santhosh Kumar Nagarajan
- Computational Biology Lab, Department of Genetic Engineering, School of Bioengineering, SRM Institute of Science and Technology, SRM Nagar, Kattankulathur, Chennai, 603203, India
| | - Sathya Babu
- Computational Biology Lab, Department of Genetic Engineering, School of Bioengineering, SRM Institute of Science and Technology, SRM Nagar, Kattankulathur, Chennai, 603203, India
| | - Seema A Kulkarni
- Department of Food and Process Engineering, School of Bioengineering, SRM Institute of Science and Technology, SRM Nagar, Kattankulathur, Chennai, 603203, India
| | - Aanand Vadivelu
- Computational Biology Lab, Department of Genetic Engineering, School of Bioengineering, SRM Institute of Science and Technology, SRM Nagar, Kattankulathur, Chennai, 603203, India
| | - Panneer Devaraju
- Unit of Vector Biology and Control, ICMR-Vector Control Research Centre, Indian Council of Medical Research (ICMR), Puducherry, India
| | - Honglae Sohn
- Department of Chemistry and Department of Carbon Materials, Chosun University, Gwangju, South Korea.
| | - Thirumurthy Madhavan
- Computational Biology Lab, Department of Genetic Engineering, School of Bioengineering, SRM Institute of Science and Technology, SRM Nagar, Kattankulathur, Chennai, 603203, India.
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Understanding the influence of lipid bilayers and ligand molecules in determining the conformational dynamics of somatostatin receptor 2. Sci Rep 2021; 11:7677. [PMID: 33828200 PMCID: PMC8027056 DOI: 10.1038/s41598-021-87422-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Accepted: 03/26/2021] [Indexed: 11/11/2022] Open
Abstract
Somatostatin receptor 2 (SSTR2) is a G-protein coupled receptor (GPCR) that controls numerous cellular processes including cell-to-cell signaling. In this study, we report how the lipid and ligand molecules influence the conformational dynamics of the membrane-bound SSTR2. Molecular simulations of different holo and apoenzyme complexes of SSTR2 in the presence and absence of a lipid bilayer were performed, observed, and correlated with previously reported studies. We identified the important SSTR2 residues that take part in the formation of the SSTR2-ligand complex. On analyzing the molecular simulation trajectories, we identified that the residue D3.32 is crucial in determining the bioactive conformation of SSTR2 ligands in the binding site. Based on the results, we suggest that designing a novel SSTR2 ligand with an H-bond donor group at the R1 position, and hydrophobic groups at R2 and R3 might have higher activity and SSTR2-selectivity. We analyzed the simulated systems to identify other important structural features involved in SSTR2-ligand binding and to observe the different conformational changes that occur in the protein after the ligand binding. Additionally, we studied the conformational dynamics of N- and C-terminal regions of SSTR2 in the presence and absence of the lipid bilayer. Both the systems were compared to understand the influence of lipid molecules in the formation of secondary structural domains by these extracellular regions. The comparative study revealed that the secondary structural elements formed by C-terminal residues in presence of lipid molecules is crucial for the functioning of SSTR2. Our study results highlight the structural complexities involved in the functioning of SSTR upon binding with the ligands in the presence and absence of lipid bilayer, which is essential for designing novel drug targets.
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Nagarajan S, Babu S, Sohn H, Madhavan T. Molecular-Level Understanding of the Somatostatin Receptor 1 (SSTR1)-Ligand Binding: A Structural Biology Study Based on Computational Methods. ACS OMEGA 2020; 5:21145-21161. [PMID: 32875251 PMCID: PMC7450625 DOI: 10.1021/acsomega.0c02847] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 07/31/2020] [Indexed: 06/11/2023]
Abstract
Somatostatin receptor 1 (SSTR1), a subtype of somatostatin receptors, is involved in various signaling mechanisms in different parts of the human body. Like most of the G-protein-coupled receptors (GPCRs), the available information on the structural features of SSTR1 responsible for the biological activity is scarce. In this study, we report a molecular-level understanding of SSTR1-ligand binding, which could be helpful in solving the structural complexities involved in SSTR1 functioning. Based on a three-dimensional quantitative structure-activity relationship (3D-QSAR) study using comparative molecular field analysis (CoMFA) and comparative molecular similarity index analysis (CoMSIA), we have identified that an electronegative, less-bulkier, and hydrophobic atom substitution can substantially increase the biological activity of SSTR1 ligands. A density functional theory (DFT) study has been followed to study the electron-related properties of the SSTR1 ligands and to validate the results obtained via the 3D-QSAR study. 3D models of SSTR1-ligand systems have been embedded in lipid-lipid bilayer membranes to perform molecular dynamics (MD) simulations. Analysis of the MD trajectories reveals important information about the crucial residues involved in SSTR1-ligand binding and various conformational changes in the protein that occur after ligand binding. Additionally, we have identified the probable ligand-binding site of SSTR1 and validated it using MD. We have also studied the favorable conditions that are essential for forming the most stable and lowest-energy bioactive conformation of the ligands inside the binding site. The results of the study could be useful in constructing more potent and novel SSTR1 antagonists and agonists.
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Affiliation(s)
- Santhosh
Kumar Nagarajan
- Computational
Biology Lab, Department of Genetic Engineering, School of Bioengineering, SRM Institute of Science and Technology, SRM Nagar, Kattankulathur, Chennai 603203, India
| | - Sathya Babu
- Computational
Biology Lab, Department of Genetic Engineering, School of Bioengineering, SRM Institute of Science and Technology, SRM Nagar, Kattankulathur, Chennai 603203, India
| | - Honglae Sohn
- Department
of Chemistry and Department of Carbon Materials, Chosun University, Gwangju, South Korea
| | - Thirumurthy Madhavan
- Computational
Biology Lab, Department of Genetic Engineering, School of Bioengineering, SRM Institute of Science and Technology, SRM Nagar, Kattankulathur, Chennai 603203, India
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Kumar Nagarajan S, Babu S, Sohn H, Devaraju P, Madhavan T. Toward a better understanding of the interaction between somatostatin receptor 2 and its ligands: a structural characterization study using molecular dynamics and conceptual density functional theory. J Biomol Struct Dyn 2018; 37:3081-3102. [PMID: 30079808 DOI: 10.1080/07391102.2018.1508368] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
This study is a part of the extensive research intending to provide the structural insights on somatostatin and its receptor. Herein, we have studied the structural complexity involved in the binding of somatostatin receptor 2 (SSTR2) with its agonists and antagonist. A 3D QSAR study based on comparative molecular field analysis and comparative molecular similarity analysis (CoMSIA) discerned that a SSTR2 ligand with electronegative, less-bulkier, and hydrogen atom donating/accepting substitutions is important for their biological activity. A conceptual density functional theory (DFT) study was followed to study the chemical behavior of the ligands based on the molecular descriptors derived using the Fukui's molecular orbital theory. We have performed molecular dynamics simulations of receptor-ligand complexes for 100 ns to analyze the dynamic stability of the backbone Cα atoms of the receptor and strength and approachability of the receptor-ligand complex. The findings of this study could be efficacious in the further studies understanding intricate structural features of the somatostatin receptors and in discovering novel subtype-specific ligands with higher affinity. Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Santhosh Kumar Nagarajan
- a Department of Genetic Engineering School of Bioengineering , SRM Institute of Science and Technology , Kattankulathur, Chennai , India
| | - Sathya Babu
- a Department of Genetic Engineering School of Bioengineering , SRM Institute of Science and Technology , Kattankulathur, Chennai , India
| | - Honglae Sohn
- b Department of Chemistry and Department of Carbon Materials , Chosun University , Gwangju , South Korea
| | - Panneer Devaraju
- c Division of Microbiology and Molecular Biology , Vector Control Research Centre, Indian Council of Medical Research , Pondicherry , India
| | - Thirumurthy Madhavan
- a Department of Genetic Engineering School of Bioengineering , SRM Institute of Science and Technology , Kattankulathur, Chennai , India
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