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Isu UH, Polasa A, Moradi M. Differential Behavior of Conformational Dynamics in Active and Inactive States of Cannabinoid Receptor 1. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.17.589939. [PMID: 38659869 PMCID: PMC11042334 DOI: 10.1101/2024.04.17.589939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
The cannabinoid receptor CB1 is a G protein-coupled receptor that regulates critical physiological processes including pain, appetite, and cognition. Understanding the conformational dynamics of CB1 associated with transitions between inactive and active signaling states is imperative for developing targeted modulators. Using microsecond-level all-atom molecular dynamics simulations, we identified marked differences in the conformational ensembles of inactive and active CB1 states in apo conditions. The inactive state exhibited substantially increased structural heterogeneity and plasticity compared to the more rigidified active state in the absence of stabilizing ligands. Transmembrane helices TM3 and TM7 were identified as distinguishing factors modulating the state-dependent dynamics. TM7 displayed amplified fluctuations selectively in the inactive state simulations attributed to disruption of conserved electrostatic contacts anchoring it to surrounding helices in the active state. Additionally, we identified significant reorganization of key salt bridge and hydrogen bond networks known to control CB1 activation between states. For instance, a conserved D213-Y224 hydrogen bond and D184-K192 salt bridge interactions showed marked rearrangements between the states. Collectively, these findings reveal the specialized role of TM7 in directing state-dependent CB1 dynamics through electrostatic switch mechanisms. By elucidating the intrinsic enhanced flexibility of inactive CB1, this study provides valuable insights into the conformational landscape enabling functional transitions. Our perspective advances understanding of CB1 activation mechanisms and offers opportunities for structure-based drug discovery targeting the state-specific conformational dynamics of this receptor.
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2
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Abstract
Advances in the structural biology of G-protein Coupled Receptors have resulted in a significant step forward in our understanding of how this important class of drug targets function at the molecular level. However, it has also become apparent that they are very dynamic molecules, and moreover, that the underlying dynamics is crucial in shaping the response to different ligands. Molecular dynamics simulations can provide unique insight into the dynamic properties of GPCRs in a way that is complementary to many experimental approaches. In this chapter, we describe progress in three distinct areas that are particularly difficult to study with other techniques: atomic level investigation of the conformational changes that occur when moving between the various states that GPCRs can exist in, the pathways that ligands adopt during binding/unbinding events and finally, the influence of lipids on the conformational dynamics of GPCRs.
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Affiliation(s)
- Naushad Velgy
- Department of Biochemistry, Structural Bioinformatics and Computational Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - George Hedger
- Department of Biochemistry, Structural Bioinformatics and Computational Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Philip C Biggin
- Department of Biochemistry, Structural Bioinformatics and Computational Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK.
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3
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Janero DR, Korde A, Makriyannis A. Ligand-Assisted Protein Structure (LAPS): An Experimental Paradigm for Characterizing Cannabinoid-Receptor Ligand-Binding Domains. Methods Enzymol 2017; 593:217-235. [DOI: 10.1016/bs.mie.2017.06.022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
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Janero DR, Yaddanapudi S, Zvonok N, Subramanian KV, Shukla VG, Stahl E, Zhou L, Hurst D, Wager-Miller J, Bohn LM, Reggio PH, Mackie K, Makriyannis A. Molecular-interaction and signaling profiles of AM3677, a novel covalent agonist selective for the cannabinoid 1 receptor. ACS Chem Neurosci 2015; 6:1400-10. [PMID: 25978068 DOI: 10.1021/acschemneuro.5b00090] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The cannabinoid 1 receptor (CB1R) is one of the most abundant G protein-coupled receptors (GPCRs) in the central nervous system. CB1R involvement in multiple physiological processes, especially neurotransmitter release and synaptic function, has made this GPCR a prime drug discovery target, and pharmacological CB1R activation has been demonstrated to be a tenable therapeutic modality. Accordingly, the design and profiling of novel, drug-like CB1R modulators to inform the receptor's ligand-interaction landscape and molecular pharmacology constitute a prime contemporary research focus. For this purpose, we report utilization of AM3677, a designer endocannabinoid (anandamide) analogue derivatized with a reactive electrophilic isothiocyanate functionality, as a covalent, CB1R-selective chemical probe. The data demonstrate that reaction of AM3677 with a cysteine residue in transmembrane helix 6 of human CB1R (hCB1R), C6.47(355), is a key feature of AM3677's ligand-binding motif. Pharmacologically, AM3677 acts as a high-affinity, low-efficacy CB1R agonist that inhibits forskolin-stimulated cellular cAMP formation and stimulates CB1R coupling to G protein. AM3677 also induces CB1R endocytosis and irreversible receptor internalization. Computational docking suggests the importance of discrete hydrogen bonding and aromatic interactions as determinants of AM3677's topology within the ligand-binding pocket of active-state hCB1R. These results constitute the initial identification and characterization of a potent, high-affinity, hCB1R-selective covalent agonist with utility as a pharmacologically active, orthosteric-site probe for providing insight into structure-function correlates of ligand-induced CB1R activation and the molecular features of that activation by the native ligand, anandamide.
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Affiliation(s)
- David R. Janero
- Center for Drug Discovery and Departments of Chemistry and Chemical Biology and Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts 02115, United States
| | - Suma Yaddanapudi
- Center for Drug Discovery and Departments of Chemistry and Chemical Biology and Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts 02115, United States
| | - Nikolai Zvonok
- Center for Drug Discovery and Departments of Chemistry and Chemical Biology and Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts 02115, United States
| | - Kumar V. Subramanian
- Center for Drug Discovery and Departments of Chemistry and Chemical Biology and Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts 02115, United States
| | - Vidyanand G. Shukla
- Center for Drug Discovery and Departments of Chemistry and Chemical Biology and Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts 02115, United States
| | - Edward Stahl
- Departments of Molecular Therapeutics and Neuroscience, Scripps Research Institute, Jupiter, Florida 33458, United States
| | - Lei Zhou
- Departments of Molecular Therapeutics and Neuroscience, Scripps Research Institute, Jupiter, Florida 33458, United States
| | - Dow Hurst
- Center for Drug Discovery, University of North Carolina at Greensboro, Greensboro, North Carolina 27402, United States
| | - James Wager-Miller
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana 47405, United States
| | - Laura M. Bohn
- Departments of Molecular Therapeutics and Neuroscience, Scripps Research Institute, Jupiter, Florida 33458, United States
| | - Patricia H. Reggio
- Center for Drug Discovery, University of North Carolina at Greensboro, Greensboro, North Carolina 27402, United States
| | - Ken Mackie
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana 47405, United States
| | - Alexandros Makriyannis
- Center for Drug Discovery and Departments of Chemistry and Chemical Biology and Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts 02115, United States
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Karpinsky-Semper D, Tayou J, Levay K, Schuchardt BJ, Bhat V, Volmar CH, Farooq A, Slepak VZ. Helix 8 and the i3 loop of the muscarinic M3 receptor are crucial sites for its regulation by the Gβ5-RGS7 complex. Biochemistry 2015; 54:1077-88. [PMID: 25551629 PMCID: PMC4318586 DOI: 10.1021/bi500980d] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
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The muscarinic M3 receptor (M3R)
is a Gq-coupled receptor and is
known to interact with many intracellular regulatory proteins. One
of these molecules is Gβ5-RGS7, the permanently associated heterodimer
of G protein β-subunit Gβ5 and RGS7, a regulator of G
protein signaling. Gβ5-RGS7 can attenuate M3R-stimulated release
of Ca2+ from intracellular stores or enhance the influx
of Ca2+ across the plasma membrane. Here we show that deletion
of amino acids 304–345 from the central portion of the i3 loop
renders M3R insensitive to regulation by Gβ5-RGS7. In addition
to the i3 loop, interaction of M3R with Gβ5-RGS7 requires helix
8. According to circular dichroism spectroscopy, the peptide corresponding
to amino acids 548–567 in the C-terminus of M3R assumes an
α-helical conformation. Substitution of Thr553 and Leu558 with
Pro residues disrupts this α-helix and abolished binding to
Gβ5-RGS7. Introduction of the double Pro substitution into full-length
M3R (M3RTP/LP) prevents trafficking of the receptor to
the cell surface. Using atropine or other antagonists as pharmacologic
chaperones, we were able to increase the level of surface expression
of the TP/LP mutant to levels comparable to that of wild-type M3R.
However, M3R-stimulated calcium signaling is still severely compromised.
These results show that the interaction of M3R with Gβ5-RGS7
requires helix 8 and the central portion of the i3 loop.
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Affiliation(s)
- Darla Karpinsky-Semper
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine , 1600 NW 10th Avenue, RMSB6024A, Miami, Florida 33136, United States
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Cohen LS, Fracchiolla KE, Becker J, Naider F. Invited review GPCR structural characterization: Using fragments as building blocks to determine a complete structure. Biopolymers 2014; 102:223-43. [DOI: 10.1002/bip.22490] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 03/24/2014] [Accepted: 03/27/2014] [Indexed: 12/30/2022]
Affiliation(s)
- Leah S. Cohen
- Department of Chemistry; The College of Staten Island, City University of New York (CUNY); Staten Island NY 10314
| | - Katrina E. Fracchiolla
- Department of Chemistry; The College of Staten Island, City University of New York (CUNY); Staten Island NY 10314
| | - Jeff Becker
- Department of Microbiology; University of Tennessee; Knoxville TN 37996
| | - Fred Naider
- Department of Chemistry; The College of Staten Island, City University of New York (CUNY); Staten Island NY 10314
- Department of Biochemistry; The Graduate Center; CUNY NY 10016-4309
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de Jesus AJ, Allen TW. The determinants of hydrophobic mismatch response for transmembrane helices. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:851-63. [PMID: 22995244 DOI: 10.1016/j.bbamem.2012.09.012] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Revised: 09/06/2012] [Accepted: 09/07/2012] [Indexed: 10/27/2022]
Abstract
Hydrophobic mismatch arises from a difference in the hydrophobic thickness of a lipid membrane and a transmembrane protein segment, and is thought to play an important role in the folding, stability and function of membrane proteins. We have investigated the possible adaptations that lipid bilayers and transmembrane α-helices undergo in response to mismatch, using fully-atomistic molecular dynamics simulations totaling 1.4 μs. We have created 25 different tryptophan-alanine-leucine transmembrane α-helical peptide systems, each composed of a hydrophobic alanine-leucine stretch, flanked by 1-4 tryptophan side chains, as well as the β-helical peptide dimer, gramicidin A. Membrane responses to mismatch include changes in local bilayer thickness and lipid order, varying systematically with peptide length. Adding more flanking tryptophan side chains led to an increase in bilayer thinning for negatively mismatched peptides, though it was also associated with a spreading of the bilayer interface. Peptide tilting, bending and stretching were systematic, with tilting dominating the responses, with values of up to ~45° for the most positively mismatched peptides. Peptide responses were modulated by the number of tryptophan side chains due to their anchoring roles and distributions around the helices. Potential of mean force calculations for local membrane thickness changes, helix tilting, bending and stretching revealed that membrane deformation is the least energetically costly of all mismatch responses, except for positively mismatched peptides where helix tilting also contributes substantially. This comparison of energetic driving forces of mismatch responses allows for deeper insight into protein stability and conformational changes in lipid membranes.
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8
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Solution- and solid-state NMR studies of GPCRs and their ligands. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:1462-75. [DOI: 10.1016/j.bbamem.2010.10.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2010] [Revised: 10/02/2010] [Accepted: 10/05/2010] [Indexed: 12/29/2022]
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9
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Zhu L, Frenkel D, Bolhuis PG. Role of fluctuations in ligand binding cooperativity of membrane receptors. PHYSICAL REVIEW LETTERS 2011; 106:168103. [PMID: 21599417 DOI: 10.1103/physrevlett.106.168103] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Indexed: 05/30/2023]
Abstract
Signal transduction upon binding of a ligand to a membrane protein can occur not only via allosteric conformational changes but also through fluctuations. We report a numerical study on the influence of conformational fluctuations on the cooperativity of a binding reaction in a simple model of an integral membrane receptor consisting of transmembrane helices. We find that small fluctuations lateral as well as perpendicular to the membrane can increase the cooperativity, with the former more dominant. Moreover, too much fluctuation induces negative cooperativity. Proteins with fewer than four helices do not show positive cooperativity under any circumstances. This behavior is rather robust, and independent of the receptor topology or ligand size. Fluctuations measured in all-atom molecular dynamics simulations of a G-protein coupled receptor fall within the predicted region of maximum cooperativity.
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Affiliation(s)
- Lizhe Zhu
- Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Amsterdam, The Netherlands
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10
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Caroccia KE, Estephan R, Cohen LS, Arshava B, Hauser M, Zerbe O, Becker JM, Naider F. Expression and biophysical analysis of a triple-transmembrane domain-containing fragment from a yeast G protein-coupled receptor. Biopolymers 2011; 96:757-71. [DOI: 10.1002/bip.21614] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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11
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Singh SN, Bakshi K, Mercier RW, Makriyannis A, Pavlopoulos S. Binding between a distal C-terminus fragment of cannabinoid receptor 1 and arrestin-2. Biochemistry 2011; 50:2223-34. [PMID: 21306178 DOI: 10.1021/bi1018144] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Internalization of G-protein-coupled receptors is mediated by phosphorylation of the C-terminus, followed by binding with the cytosolic protein arrestin. To explore structural factors that may play a role in internalization of cannabinoid receptor 1 (CB1), we utilize a phosphorylated peptide derived from the distal C-terminus of CB1 (CB1(5P)(454-473)). Complexes formed between the peptide and human arrestin-2 (wt-arr2(1-418)) were compared to those formed with a truncated arrestin-2 mutant (tr-arr2(1-382)) using isothermal titration calorimetry and nuclear magnetic resonance spectroscopy. The pentaphosphopeptide CB1(5P)(454-473) adopts a helix-loop conformation, whether binding to full-length arrestin-2 or its truncated mutant. This structure is similar to that of a heptaphosphopeptide, mimicking the distal segment of the rhodopsin C-tail (Rh(7P)(330-348)), binding to visual arrestin, suggesting that this adopted structure bears functional significance. Isothermal titration calorimetry (ITC) experiments show that the CB1(5P)(454-473) peptide binds to tr-arr2(1-382) with higher affinity than to the full-length wt-arr2(1-418). As the observed structure of the bound peptides is similar in either case, we attribute the increased affinity to a more exposed binding site on the N-domain of the truncated arrestin construct. The transferred NOE data from the bound phosphopeptides are used to predict a model describing the interaction with arrestin, using the data driven HADDOCK docking program. The truncation of arrestin-2 provides scope for positively charged residues in the polar core of the protein to interact with phosphates present in the loop of the CB1(5P)(454-473) peptide.
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Affiliation(s)
- Shubhadra N Singh
- Center for Drug Discovery, 360 Huntington Avenue, 116 Mugar Hall, Boston, Massachusetts 02115, United States
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12
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Tiburu EK, Tyukhtenko S, Zhou H, Janero DR, Struppe J, Makriyannis A. Human cannabinoid 1 GPCR C-terminal domain interacts with bilayer phospholipids to modulate the structure of its membrane environment. AAPS JOURNAL 2011; 13:92-8. [PMID: 21234731 DOI: 10.1208/s12248-010-9244-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Accepted: 11/21/2010] [Indexed: 02/08/2023]
Abstract
G protein-coupled receptors (GPCRs) play critical physiological and therapeutic roles. The human cannabinoid 1 GPCR (hCB1) is a prime pharmacotherapeutic target for addiction and cardiometabolic disease. Our prior biophysical studies on the structural biology of a synthetic peptide representing the functionally significant hCB1 transmembrane helix 7 (TMH7) and its cytoplasmic extension, helix 8 (H8), [hCB1(TMH7/H8)] demonstrated that the helices are oriented virtually perpendicular to each other in membrane-mimetic environments. We identified several hCB1(TMH7/H8) structure-function determinants, including multiple electrostatic amino-acid interactions and a proline kink involving the highly conserved NPXXY motif. In phospholipid bicelles, TMH7 structure, orientation, and topology relative to H8 are dynamically modulated by the surrounding membrane phospholipid bilayer. These data provide a contextual basis for the present solid-state NMR study to investigate whether intermolecular interactions between hCB1(TMH7/H8) and its phospholipid environment may affect membrane-bilayer structure. For this purpose, we measured (1)H-(13)C heteronuclear dipolar couplings for the choline, glycerol, and acyl-chain regions of dimyristoylphosphocholine in a magnetically aligned hCB1(TMH7/H8) bicelle sample. The results identify discrete regional interactions between hCB1(TMH7/H8) and membrane lipid molecules that increase phospholipid motion and decrease phospholipid order, indicating that the peptide's partial traversal of the bilayer alters membrane structure. These data offer new insight into hCB1(TMH7/H8) properties and support the concept that the membrane bilayer itself may serve as a mechanochemical mediator of hCB1/GPCR signal transduction. Since interaction with its membrane environment has been implicated in hCB1 function and its modulation by small-molecule therapeutics, our work should help inform hCB1 pharmacology and the design of hCB1-targeted drugs.
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Affiliation(s)
- Elvis K Tiburu
- Center for Drug Discovery and Department of Chemistry and Chemical Biology, Northeastern University, 360 Huntington Avenue, 116 Mugar Hall, Boston, Massachusetts 02115-5000, United States of America
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13
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Ramos J, Cruz VL, Martínez-Salazar J, Campillo NE, Páez JA. Dissimilar interaction of CB1/CB2 with lipid bilayers as revealed by molecular dynamics simulation. Phys Chem Chem Phys 2011; 13:3660-8. [DOI: 10.1039/c0cp01456g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Tyukhtenko S, Tiburu EK, Deshmukh L, Vinogradova O, Janero DR, Makriyannis A. NMR solution structure of human cannabinoid receptor-1 helix 7/8 peptide: candidate electrostatic interactions and microdomain formation. Biochem Biophys Res Commun 2009; 390:441-6. [PMID: 19766594 DOI: 10.1016/j.bbrc.2009.09.053] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2009] [Accepted: 09/14/2009] [Indexed: 10/20/2022]
Abstract
We report the NMR solution structure of a synthetic 40-mer (T(377)-E(416)) that encompasses human cannabinoid receptor-1 (hCB1) transmembrane helix 7 (TMH7) and helix 8 (H8) [hCB1(TMH7/H8)] in 30% trifluoroethanol/H(2)O. Structural features include, from the peptide's amino terminus, a hydrophobic alpha-helix (TMH7); a loop-like, 11 residue segment featuring a pronounced Pro-kink within the conserved NPxxY motif; a short amphipathic alpha-helix (H8) orthogonal to TMH7 with cationic and hydrophobic amino-acid clusters; and an unstructured C-terminal end. The hCB1(TMH7/H8) NMR solution structure suggests multiple electrostatic amino-acid interactions, including an intrahelical H8 salt bridge and a hydrogen-bond network involving the peptide's loop-like region. Potential cation-pi and cation-phenolic OH interactions between Y(397) in the TMH7 NPxxY motif and R(405) in H8 are identified as candidate structural forces promoting interhelical microdomain formation. This microdomain may function as a flexible molecular hinge during ligand-induced hCB1 conformer transitions.
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Affiliation(s)
- Sergiy Tyukhtenko
- Department of Chemistry and Chemical Biology, Northeastern University, Center for Drug Discovery, Boston, MA 02115-5000, USA
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Tiburu EK, Gulla SV, Tiburu M, Janero DR, Budil DE, Makriyannis A. Dynamic conformational responses of a human cannabinoid receptor-1 helix domain to its membrane environment. Biochemistry 2009; 48:4895-904. [PMID: 19485422 DOI: 10.1021/bi802235w] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The influence of membrane environment on human cannabinoid 1 (hCB(1)) receptor transmembrane helix (TMH) conformational dynamics was investigated by solid-state NMR and site-directed spin labeling/EPR with a synthetic peptide, hCB(1)(T377-E416), corresponding to the receptor's C-terminal component, i.e., TMH7 and its intracellular alpha-helical extension (H8) (TMH7/H8). Solid-state NMR experiments with mechanically aligned hCB(1)(T377-E416) specifically (2)H- or (15)N-labeled at Ala380 and reconstituted in membrane-mimetic dimyristoylphosphocholine (DMPC) or 1-palmitoyl-2-oleoyl-sn-glycerophosphocholine (POPC) bilayers demonstrate that the conformation of the TMH7/H8 peptide is more heterogeneous in the thinner DMPC bilayer than in the thicker POPC bilayer. As revealed by EPR studies on hCB(1)(T377-E416) spin-labeled at Cys382 and reconstituted into the phospholipid bilayers, the spin label partitions actively between hydrophobic and hydrophilic environments. In the DMPC bilayer, the hydrophobic component dominates, regardless of temperature. Mobility parameters (DeltaH(0)(-1)) are 0.3 and 0.73 G for the peptide in the DMPC or POPC bilayer environment, respectively. Interspin distances of doubly labeled hCB(1)(T377-E416) peptide reconstituted into a TFE/H(2)O mixture or a POPC or DMPC bilayer were estimated to be 10.6 +/- 0.5, 16.8 +/- 1, and 11.6 +/- 0.8 A, respectively. The extent of coupling (>or=50%) between spin labels located at i and i + 4 in a TFE/H(2)O mixture or a POPC bilayer is indicative of an alpha-helical TMH conformation, whereas the much lower coupling (14%) when the peptide is in a DMPC bilayer suggests a high degree of peptide conformational heterogeneity. These data demonstrate that hCB(1)(T377-E416) backbone dynamics as well as spin-label rotameric freedom are sensitive to and altered by the peptide's phospholipid bilayer environment, which exerts a dynamic influence on the conformation of a TMH critical to signal transmission by the hCB(1) receptor.
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Affiliation(s)
- Elvis K Tiburu
- Center for Drug Discovery, Northeastern University, Boston, Massachusetts 02115-5000, USA
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16
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Tiburu EK, Tyukhtenko S, Deshmukh L, Vinogradova O, Janero DR, Makriyannis A. Structural biology of human cannabinoid receptor-2 helix 6 in membrane-mimetic environments. Biochem Biophys Res Commun 2009; 384:243-8. [PMID: 19397896 DOI: 10.1016/j.bbrc.2009.04.099] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Accepted: 04/19/2009] [Indexed: 10/20/2022]
Abstract
We detail the structure and dynamics of a synthetic peptide corresponding to transmembrane helix 6 (TMH6) of human cannabinoid receptor-2 (hCB2) in biomembrane-mimetic environments. The peptide's NMR structural biology is characterized by two alpha-helical domains bridged by a flexible, nonhelical hinge region containing a highly-conserved CWFP motif with an environmentally sensitive, Pro-based conformational switch. Buried within the peptide's flexible region, W(258) may hydrogen-bond with L(255) to help stabilize the Pro-kinked hCB2 TMH6 structure and position C(257) advantageously for interaction with agonist ligands. These characteristics of hCB2 TMH6 are potential structural features of ligand-induced hCB2 activation in vivo.
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Affiliation(s)
- Elvis K Tiburu
- Center for Drug Discovery and Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA 02115-5000, USA
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