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Puri S, Kenyon BM, Hamrah P. Immunomodulatory Role of Neuropeptides in the Cornea. Biomedicines 2022; 10:1985. [PMID: 36009532 PMCID: PMC9406019 DOI: 10.3390/biomedicines10081985] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 08/11/2022] [Accepted: 08/12/2022] [Indexed: 12/21/2022] Open
Abstract
The transparency of the cornea along with its dense sensory innervation and resident leukocyte populations make it an ideal tissue to study interactions between the nervous and immune systems. The cornea is the most densely innervated tissue of the body and possesses both immune and vascular privilege, in part due to its unique repertoire of resident immune cells. Corneal nerves produce various neuropeptides that have a wide range of functions on immune cells. As research in this area expands, further insights are made into the role of neuropeptides and their immunomodulatory functions in the healthy and diseased cornea. Much remains to be known regarding the details of neuropeptide signaling and how it contributes to pathophysiology, which is likely due to complex interactions among neuropeptides, receptor isoform-specific signaling events, and the inflammatory microenvironment in disease. However, progress in this area has led to an increase in studies that have begun modulating neuropeptide activity for the treatment of corneal diseases with promising results, necessitating the need for a comprehensive review of the literature. This review focuses on the role of neuropeptides in maintaining the homeostasis of the ocular surface, alterations in disease settings, and the possible therapeutic potential of targeting these systems.
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Affiliation(s)
- Sudan Puri
- Center for Translational Ocular Immunology, Tufts Medical Center, Tufts University School of Medicine, Boston, MA 02111, USA
- Department of Ophthalmology, Tufts Medical Center, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Brendan M. Kenyon
- Center for Translational Ocular Immunology, Tufts Medical Center, Tufts University School of Medicine, Boston, MA 02111, USA
- Program in Neuroscience, Graduate School of Biomedical Sciences, Tufts University, Boston, MA 02111, USA
| | - Pedram Hamrah
- Center for Translational Ocular Immunology, Tufts Medical Center, Tufts University School of Medicine, Boston, MA 02111, USA
- Department of Ophthalmology, Tufts Medical Center, Tufts University School of Medicine, Boston, MA 02111, USA
- Program in Neuroscience, Graduate School of Biomedical Sciences, Tufts University, Boston, MA 02111, USA
- Departments of Immunology and Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA
- Cornea Service, Tufts New England Eye Center, Boston, MA 02111, USA
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2
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The neuropeptide galanin adopts an irregular secondary structure. Biochem Biophys Res Commun 2022; 626:121-128. [PMID: 35994823 DOI: 10.1016/j.bbrc.2022.08.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 08/11/2022] [Indexed: 11/22/2022]
Abstract
Human galanin is a 30-residue neuropeptide targeted for development of analgesics, antidepressants, and anticonvulsants. While previous work from our group and others has already produced significant insights into galanin's N-terminal region, no extant structures of galanin in databases include its full-length sequence and the function of its C-terminus remains ambiguous. We report the NMR solution structure of full-length human galanin C-terminal amide, determined from 2D 1H-1H COSY, TOCSY, and ROESY NMR data. Galanin adopts an irregular helical structure across its N-terminus, likely the average of several coiling states. We present the NMR structure of a peptide encompassing the C-terminus of galanin as a stand-alone fragment. The C-terminus of full-length galanin appears to indirectly assist the intramolecular association of hydrophobic sidechains within its N-terminus, remotely rigidifying their position when compared to previously studied N-terminal galanin fragments. By contrast, there is flexibility in the C-terminus of galanin, characterized by two i to i + 2 hydrogen-bonded turns within an otherwise dynamic backbone. The C-terminal portion of the peptide renders it soluble, and plays a hitherto undescribed biophysical role in pre-organizing the galanin receptor binding epitope. We speculate that hydrophilic microdomains of signaling peptides, hormones, and perhaps intrinsically disordered proteins may also function similarly.
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3
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Duan J, Shen DD, Zhao T, Guo S, He X, Yin W, Xu P, Ji Y, Chen LN, Liu J, Zhang H, Liu Q, Shi Y, Cheng X, Jiang H, Eric Xu H, Zhang Y, Xie X, Jiang Y. Molecular basis for allosteric agonism and G protein subtype selectivity of galanin receptors. Nat Commun 2022; 13:1364. [PMID: 35292680 PMCID: PMC8924211 DOI: 10.1038/s41467-022-29072-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 02/24/2022] [Indexed: 12/12/2022] Open
Abstract
Peptide hormones and neuropeptides are complex signaling molecules that predominately function through G protein-coupled receptors (GPCRs). Two unanswered questions remaining in the field of peptide-GPCR signaling systems pertain to the basis for the diverse binding modes of peptide ligands and the specificity of G protein coupling. Here, we report the structures of a neuropeptide, galanin, bound to its receptors, GAL1R and GAL2R, in complex with their primary G protein subtypes Gi and Gq, respectively. The structures reveal a unique binding pose of galanin, which almost ‘lays flat’ on the top of the receptor transmembrane domain pocket in an α-helical conformation, and acts as an ‘allosteric-like’ agonist via a distinct signal transduction cascade. The structures also uncover the important features of intracellular loop 2 (ICL2) that mediate specific interactions with Gq, thus determining the selective coupling of Gq to GAL2R. ICL2 replacement in Gi-coupled GAL1R, μOR, 5-HT1AR, and Gs-coupled β2AR and D1R with that of GAL2R promotes Gq coupling of these receptors, highlighting the dominant roles of ICL2 in Gq selectivity. Together our results provide insights into peptide ligand recognition and allosteric activation of galanin receptors and uncover a general structural element for Gq coupling selectivity. The basis for the diverse peptide-binding modes and the G protein selectivity of peptide GPCRs remains elusive. Here, the authors offer a structural basis for allosteric-like agonism and G protein selectivity of a neuropeptide GPCR, galanin receptor.
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Affiliation(s)
- Jia Duan
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Dan-Dan Shen
- Department of Biophysics and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Tingting Zhao
- School of Chinese Materia Medica, Nanjing University of Chinese Medicine, Nanjing, 210046, China.,CAS Key Laboratory of Receptor Research, National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Shimeng Guo
- School of Chinese Materia Medica, Nanjing University of Chinese Medicine, Nanjing, 210046, China.,CAS Key Laboratory of Receptor Research, National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Xinheng He
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Wanchao Yin
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Peiyu Xu
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Yujie Ji
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Li-Nan Chen
- Department of Biophysics and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Jinyu Liu
- School of Chinese Materia Medica, Nanjing University of Chinese Medicine, Nanjing, 210046, China.,CAS Key Laboratory of Receptor Research, National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Huibing Zhang
- Department of Biophysics and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Qiufeng Liu
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Yi Shi
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Xi Cheng
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Hualiang Jiang
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China.,University of Chinese Academy of Sciences, Beijing, 100049, China.,School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210, China
| | - H Eric Xu
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China. .,University of Chinese Academy of Sciences, Beijing, 100049, China. .,School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210, China.
| | - Yan Zhang
- Department of Biophysics and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China. .,Liangzhu Laboratory, Zhejiang University Medical Center, Hangzhou, Zhejiang, China. .,MOE Frontier Science Center for Brain Research and Brain-Machine Integration, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China. .,Key Laboratory of Immunity and Inflammatory Diseases of Zhejiang Province, Hangzhou, Zhejiang, China.
| | - Xin Xie
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China. .,School of Chinese Materia Medica, Nanjing University of Chinese Medicine, Nanjing, 210046, China. .,CAS Key Laboratory of Receptor Research, National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China. .,State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China. .,School of Pharmaceutical Science and Technology, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, 310024, China.
| | - Yi Jiang
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China. .,School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210, China. .,Lingang Laboratory, Shanghai, 200031, China.
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4
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Dong Z, Guan L, Wang C, Xu H, Li Z, Li F. Reconstruction of a helical trimer by the second transmembrane domain of human copper transporter 2 in micelles and the binding of the trimer to silver. RSC Adv 2016. [DOI: 10.1039/c5ra24889b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The second transmembrane domain of human copper transporter 2 (hCtr2-TMD2) forms a trimer with a weaker intermolecular interaction and a lower affinity for Ag(I) than hCtr1-TMD2 trimer.
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Affiliation(s)
- Zhe Dong
- State Key Laboratory of Supramolecular Structure and Materials
- Jilin University
- Changchun 130012
- P. R. China
| | - Liping Guan
- State Key Laboratory of Supramolecular Structure and Materials
- Jilin University
- Changchun 130012
- P. R. China
| | - Chunyu Wang
- State Key Laboratory of Supramolecular Structure and Materials
- Jilin University
- Changchun 130012
- P. R. China
| | - Haoran Xu
- Key Laboratory for Molecular Enzymology & Engineering
- The Ministry of Education
- Jilin University
- Changchun 130012
- P. R. China
| | - Zhengqiang Li
- Key Laboratory for Molecular Enzymology & Engineering
- The Ministry of Education
- Jilin University
- Changchun 130012
- P. R. China
| | - Fei Li
- State Key Laboratory of Supramolecular Structure and Materials
- Jilin University
- Changchun 130012
- P. R. China
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5
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Solution NMR studies on the orientation of membrane-bound peptides and proteins by paramagnetic probes. Molecules 2013; 18:7407-35. [PMID: 23799448 PMCID: PMC6269851 DOI: 10.3390/molecules18077407] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 06/13/2013] [Accepted: 06/20/2013] [Indexed: 12/24/2022] Open
Abstract
Many peptides and proteins are attached to or immersed in a biological membrane. In order to understand their function not only the structure but also their topology in the membrane is important. Solution NMR spectroscopy is one of the most often used approaches to determine the orientation and localization of membrane-bound peptides and proteins. Here we give an application-oriented overview on the use of paramagnetic probes for the investigation of membrane-bound peptides and proteins. The examples discussed range from the large pool of antimicrobial peptides, bacterial toxins, cell penetrating peptides to domains of larger proteins or the calcium regulating protein phospholamban. Topological information is obtained in all these examples by the use of either attached or freely mobile paramagnetic tags. For some examples information obtained from the paramagnetic probes was included in the structure determination.
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6
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Jurkowski W, Yazdi S, Elofsson A. Ligand binding properties of human galanin receptors. Mol Membr Biol 2012; 30:206-16. [DOI: 10.3109/09687688.2012.750384] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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7
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8
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Webling KEB, Runesson J, Bartfai T, Langel Ü. Galanin receptors and ligands. Front Endocrinol (Lausanne) 2012; 3:146. [PMID: 23233848 PMCID: PMC3516677 DOI: 10.3389/fendo.2012.00146] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Accepted: 11/08/2012] [Indexed: 12/13/2022] Open
Abstract
The neuropeptide galanin was first discovered 30 years ago. Today, the galanin family consists of galanin, galanin-like peptide (GALP), galanin-message associated peptide (GMAP), and alarin and this family has been shown to be involved in a wide variety of biological and pathological functions. The effect is mediated through three GPCR subtypes, GalR1-3. The limited number of specific ligands to the galanin receptor subtypes has hindered the understanding of the individual effects of each receptor subtype. This review aims to summarize the current data of the importance of the galanin receptor subtypes and receptor subtype specific agonists and antagonists and their involvement in different biological and pathological functions.
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Affiliation(s)
- Kristin E. B. Webling
- Department of Neurochemistry, Arrhenius Laboratories for Natural Science, Stockholm UniversityStockholm, Sweden
- *Correspondence: Kristin E. B. Webling, Department of Neurochemistry, Arrhenius Laboratories for Natural Science, Stockholm University, Svante Arrheniusv. 21A, 10691 Stockholm, Sweden. e-mail:
| | - Johan Runesson
- Department of Neurochemistry, Arrhenius Laboratories for Natural Science, Stockholm UniversityStockholm, Sweden
| | - Tamas Bartfai
- Molecular and Integrative Neurosciences Department, The Scripps Research InstituteLa Jolla, CA, USA
| | - Ülo Langel
- Department of Neurochemistry, Arrhenius Laboratories for Natural Science, Stockholm UniversityStockholm, Sweden
- Institute of Technology, University of TartuTartu, Estonia
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9
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Lundström L, Sollenberg UE, Bartfai T, Langel Ü. Molecular characterization of the ligand binding site of the human galanin receptor type 2, identifying subtype selective interactions. J Neurochem 2007; 103:1774-84. [DOI: 10.1111/j.1471-4159.2007.04959.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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10
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Lee K, Lee D, Park Y, Kang DI, Shin S, Hahm KS, Kim Y. Interactions between the plasma membrane and the antimicrobial peptide HP (2-20) and its analogues derived from Helicobacter pylori. Biochem J 2006; 394:105-14. [PMID: 16255716 PMCID: PMC1386008 DOI: 10.1042/bj20051574] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
HP (2-20), a 19-residue peptide derived from the N-terminus of Helicobacter pylori ribosomal protein L1, has antimicrobial activity but is not cytotoxic to human erythrocytes. We synthesized several peptide analogues to investigate the effects of substitutions on structure and antimicrobial activity. Replacement of Gln16 and Asp18 with tryptophan [anal-3 (analogue-3)] caused a dramatic increase in lytic activities against bacteria and fungi. By contrast, a decrease in amphiphilicity caused by replacement of Phe5 or Leu11 with serine was accompanied by a reduction in antimicrobial activity. Analysis of the tertiary structures of the peptides in SDS micelles by NMR spectroscopy revealed that they have a well-defined a-helical structure. Among the analogues, anal-3 has the longest a-helix, from Val4 to Trp18. The enhanced hydrophobicity and increased a-helicity results in enhanced antimicrobial activity in anal-3 without an increase in haemolytic activity. Fluorescence experiments proved that the bacterial-cell selectivity of the anal-3 peptide is due to its high binding affinity for negatively charged phospholipids in bacterial cells. Results showing the effect of spin-labels on the NMR spectra indicated that the side chains in the hydrophobic phase of the amphiphilic a-helix are buried on the surface of the micelle and the tryptophan indole ring is anchored in the membrane surface. Because anal-3 shows high selectivity towards bacterial and fungal cells, it may provide an avenue for the development of new antibiotics.
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Affiliation(s)
- Kwang H. Lee
- *Department of Chemistry and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
| | - Dong G. Lee
- †School of Life Science and Biotechnology, College of Natural Sciences, Kyungpook National University, Taegu 702-701, Korea
| | - Yoonkyung Park
- ‡Department of Bio-Materials, Graduate School and Research Center for Proteineous Materials, Chosun University, Gwangju 501-759, Korea
| | - Dong-Il Kang
- *Department of Chemistry and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
| | - Song Y. Shin
- ‡Department of Bio-Materials, Graduate School and Research Center for Proteineous Materials, Chosun University, Gwangju 501-759, Korea
| | - Kyung-Soo Hahm
- ‡Department of Bio-Materials, Graduate School and Research Center for Proteineous Materials, Chosun University, Gwangju 501-759, Korea
| | - Yangmee Kim
- *Department of Chemistry and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
- To whom correspondence should be addressed (email )
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11
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Brunecky R, Lee S, Rzepecki PW, Overduin M, Prestwich GD, Kutateladze AG, Kutateladze TG. Investigation of the binding geometry of a peripheral membrane protein. Biochemistry 2006; 44:16064-71. [PMID: 16331966 PMCID: PMC2516348 DOI: 10.1021/bi051127+] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A growing number of modules including FYVE domains target key signaling proteins to membranes through specific recognition of lipid headgroups and hydrophobic insertion into bilayers. Despite the critical role of membrane insertion in the function of these modules, the structural mechanism of membrane docking and penetration remains unclear. In particular, the three-dimensional orientation of the inserted proteins with respect to the membrane surface is difficult to define quantitatively. Here, we determined the geometry of the micelle penetration of the early endosome antigen 1 (EEA1) FYVE domain by obtaining NMR-derived restraints that correlate with the distances between protein backbone amides and spin-labeled probes. The 5- and 14-doxyl-phosphatidylcholine spin-labels were incorporated into dodecylphosphocholine (DPC) micelles, and the reduction of amide signal intensities of the FYVE domain due to paramagnetic relaxation enhancement was measured. The vector of the FYVE domain insertion was estimated relative to the molecular axis by minimizing the paramagnetic restraints obtained in phosphatidylinositol 3-phosphate (PI3P)-enriched micelles containing only DPC or mixed with phosphatidylserine (PS). Additional distance restraints were obtained using a novel spin-label mimetic of PI(3)P that contains a nitroxyl radical near the threitol group of the lipid. Conformational changes indicative of elongation of the membrane insertion loop (MIL) were detected upon micelle interaction, in which the hydrophobic residues of the loop tend to move deeper into the nonpolar core of micelles. The micelle insertion mechanism of the FYVE domain defined in this study is consistent with mutagenesis data and chemical shift perturbations and demonstrates the advantage of using the spin-label NMR approach for investigating the binding geometry by peripheral membrane proteins.
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Affiliation(s)
- Roman Brunecky
- Department of Pharmacology, University of Colorado Health Sciences Center, Aurora, Colorado 80045, USA
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12
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Halskau O, Underhaug J, Frøystein NA, Martínez A. Conformational flexibility of alpha-lactalbumin related to its membrane binding capacity. J Mol Biol 2005; 349:1072-86. [PMID: 15913646 DOI: 10.1016/j.jmb.2005.04.020] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2005] [Revised: 04/04/2005] [Accepted: 04/12/2005] [Indexed: 10/25/2022]
Abstract
Different folding states of the small, globular milk protein bovine alpha-lactalbumin (BLA) induced by the anionic surfactant sodium dodecylsulphate (SDS) have been examined by fluorescence spectroscopy, CD and NMR. The solution structure of the protein in the absence of SDS was also determined, indicating fluidity even under native conditions. BLA is partly denatured to a molten globule (MG)-like state by micromolar concentrations of SDS, and the transitions from native to MG-like state are dependent on pH, the protein being more sensitive to the surfactant at pH 6.5. As indicated by measurements of the intrinsic emission fluorescence, the tertiary structure disappears at lower concentrations of SDS than most of the secondary structure, as estimated from CD data. The MG-like state induced by low concentrations of SDS is not observable by NMR, and is probably fluctuating and/or aggregating. At higher concentrations of SDS above the critic concentration of micelles, an NMR-observable state reappears. This micelle-associated conformer was partially assigned, and found to bear strong resemblance to the acid-tri-fluoroethanol state, retaining weakened versions of the A and C helix of native BLA. We discuss the results in terms of the inherent flexibility of the protein, and its ability to form multiple folding states and to bind to membranes. Also, we propose that proteins with stable MG-like conformers can have these states stabilized by low levels of compounds with surfactant properties in vivo.
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Affiliation(s)
- Oyvind Halskau
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009 Bergen, Norway
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13
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Tyndall JDA, Pfeiffer B, Abbenante G, Fairlie DP. Over One Hundred Peptide-Activated G Protein-Coupled Receptors Recognize Ligands with Turn Structure. Chem Rev 2005; 105:793-826. [PMID: 15755077 DOI: 10.1021/cr040689g] [Citation(s) in RCA: 176] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Joel D A Tyndall
- Center for Drug Design and Development, Institute for Molecular Bioscience, University of Queensland, Brisbane, Qld 4072, Australia
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14
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Bartfai T, Lu X, Badie-Mahdavi H, Barr AM, Mazarati A, Hua XY, Yaksh T, Haberhauer G, Ceide SC, Trembleau L, Somogyi L, Kröck L, Rebek J. Galmic, a nonpeptide galanin receptor agonist, affects behaviors in seizure, pain, and forced-swim tests. Proc Natl Acad Sci U S A 2004; 101:10470-5. [PMID: 15240875 PMCID: PMC478593 DOI: 10.1073/pnas.0403802101] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The pharmacological exploitation of the galanin receptors as drug targets for treatment of epilepsy, depression, and pain has been hampered by the lack of workable compounds for medicinal chemists from random screening of large chemical libraries. The present work uses the tripeptidomimetic galnon and displays its presumed pharmacophores on a rigid molecular scaffold. The scaffold is related to marine natural products and presents three functional groups near one another in space, in a manner reminiscent of a protein surface. An active compound, Galmic, was identified from a small synthetic library and tested in vitro and in vivo for its affinity and efficacy at galanin receptors. Galmic has micromolar affinity for GalR1 receptors (Ki = 34.2 microM) and virtually no affinity for GalR2 receptors. In vitro, Galmic, like galanin, suppresses long-term potentiation in the dentate gyrus; it blocks status epilepticus when injected intrahippocampally or administered i.p. Galmic applied i.p. shows antidepressant-like effects in the forced-swim test, and it is a potent inhibitor of flinching behavior in the inflammatory pain model induced by formalin injection. These data further implicate brain and spinal cord galanin receptors as drug targets and provide an example of a systemically active compound based on a scaffold that mimics protein surfaces.
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Affiliation(s)
- Tamas Bartfai
- Department of Neuropharmacology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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15
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Bárány-Wallje E, Andersson A, Gräslund A, Mäler L. NMR solution structure and position of transportan in neutral phospholipid bicelles. FEBS Lett 2004; 567:265-9. [PMID: 15178334 DOI: 10.1016/j.febslet.2004.04.079] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2004] [Revised: 04/21/2004] [Accepted: 04/21/2004] [Indexed: 11/16/2022]
Abstract
Transportan is a chimeric cell-penetrating peptide constructed from the peptides galanin and mastoparan, which has the ability to internalize living cells carrying a hydrophilic load. In this study, we have determined the NMR solution structure and investigated the position of transportan in neutral bicelles. The structure revealed a well-defined alpha-helix in the C-terminal mastoparan part of the peptide and a weaker tendency to form an alpha-helix in the N-terminal domain. The position of the peptide in relation to the membrane, as studied by adding paramagnetic probes, shows that the peptide lies parallel to, and in the head-group region of the membrane surface. This result is supported by amide proton secondary chemical shifts.
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Affiliation(s)
- Elsa Bárány-Wallje
- Department of Biochemistry and Biophysics, The Arrhenius Laboratories, Stockholm University, S-10691 Stockholm, Sweden
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16
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Li H, Li F, Qian ZM, Sun H. Structure and topology of the transmembrane domain 4 of the divalent metal transporter in membrane-mimetic environments. ACTA ACUST UNITED AC 2004; 271:1938-51. [PMID: 15128303 DOI: 10.1111/j.1432-1033.2004.04104.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The divalent metal transporter (DMT1) is a 12-transmembrane domain protein responsible for dietary iron uptake in the duodenum and iron acquisition from transferrin in peripheral tissues. The transmembrane domain 4 (TM4) of DMT1 has been shown to be crucial for its biological function. Here we report the 3D structure and topology of the DMT1-TM4 peptide by NMR spectroscopy with simulated annealing calculations in membrane-mimetic environments, e.g. 2,2,2-trifluoroethanol and SDS micelles. The 3D structures of the peptide are similar in both environments, with nonordered and flexible N- and C-termini flanking an ordered helical region. The final set of the 16 lowest energy structures is particularly well defined in the region of residues Leu9-Phe20 in 2,2,2-trifluoroethanol, with a mean pairwise root mean square deviation of 0.23 +/- 0.10 A for the backbone heavy atoms and 0.82 +/- 0.17 A for all heavy atoms. In SDS micelles, the length of the helix is dependent on pH values. In particular, the C-terminus becomes well-structured at low pH (4.0), whereas the N-terminal segment (Arg1-Gly7) is flexible and poorly defined at all pH values studied. The effects of 12-doxylPtdCho spin-label and paramagnetic metal ions on NMR signal intensities demonstrated that both the N-terminus and helical region of the TM4 are embedded into the interior of SDS micelles. Unexpectedly, we observed that amide protons exchanged much faster in SDS than in 2,2,2-trifluoroethanol, indicating that there is possible solvent accessibility in the structure. The paramagnetic metal ions broaden NMR signals from residues both situated in aqueous phase and in the helical region. From these results we speculate that DMT1-TM4s may self-assemble to form a channel through which metal ions are likely to be transported. These results might provide an insight into the structure-function relationship for the integral DMT1.
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Affiliation(s)
- Hongyan Li
- Department of Chemistry and Open Laboratory of Chemical Biology, The University of Hong Kong, China
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17
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Dagar S, Onyüksel H, Akhter S, Krishnadas A, Rubinstein I. Human galanin expresses amphipathic properties that modulate its vasoreactivity in vivo. Peptides 2003; 24:1373-80. [PMID: 14706552 DOI: 10.1016/j.peptides.2003.08.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The purpose of this study was to determine whether human galanin, a pleiotropic 30-amino acid neuropeptide, expresses amphipathic properties in vitro and, if so, whether these properties modulate its vasoactive effects in the intact peripheral microcirculation. We found that human galanin aggregates in an aqueous solution and forms micelles with a critical micellar concentration (CMC) of 0.4 microM. In addition, the peptide interacted with model membrane as indicated by long and significant increase of the surface pressure of the biomimetic monolayer membrane in vitro. Interactions of human galanin with sterically stabilized phospholipid micelles (SMM) were not associated with a significant change in peptide conformation. Using intravital microscopy, we found that suffusion of human galanin alone elicited significant concentration-dependent vasoconstriction in the intact hamster cheek pouch. This response was amplified when human galanin in SSM was suffused onto the cheek pouch. The effects of human galanin alone and in SSM were mediated by galanin receptors because galantide, a galanin receptor antagonist, abrogated galanin-induced vasoconstriction. Collectively, these data show that human galanin expresses amphipathic properties in the presence of phospholipids which in turn amplifies its vasoactive effects in the intact peripheral microcirculation.
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Affiliation(s)
- Sumeet Dagar
- Department of Biopharmaceutical Sciences, University of Illinois at Chicago, Chicago, IL, USA
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18
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Li H, Li F, Sun H, Qian ZM. Membrane-inserted conformation of transmembrane domain 4 of divalent-metal transporter. Biochem J 2003; 372:757-66. [PMID: 12646040 PMCID: PMC1223444 DOI: 10.1042/bj20030075] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2003] [Revised: 02/18/2003] [Accepted: 03/19/2003] [Indexed: 11/17/2022]
Abstract
Divalent-metal transporter 1 (DMT1) is involved in the intestinal iron absorption and in iron transport in the transferrin cycle. It transports metal ions at low pH ( approximately 5.5), but not at high pH (7.4), and the transport is a proton-coupled process. Previously it has been shown that transmembrane domain 4 (TM4) is crucial for the function of this protein. Here we provide the first direct experimental evidence for secondary-structural features and membrane insertions of a 24-residue peptide, corresponding to TM4 of DMT1 (DMTI-TM4), in various membrane-mimicking environments by the combined use of CD and NMR spectroscopies. The peptide mainly adopts an alpha-helical structure in trifluoroethanol, SDS and dodecylphosphocholine micelles, and dimyristoyl phosphatidylcholine and dimyristoyl phosphatidylglycerol small unilamellar vesicles. It has been demonstrated from both Halpha secondary shifts and nuclear-Overhauser-enhancement (NOE) connectivities that the peptide is well folded into an alpha-helix from Val(8) to Lys(23) in SDS micelles at pH 4.0, whereas the N-terminus is highly flexible. The alpha-helical content estimated from NMR data is in agreement with that extracted from CD simulations. The highest helicity was observed in the anionic phospholipids [1,2-dimyristoyl- sn -glycero-3-[phospho-rac -(1-glycerol)]], indicating that electrostatic attraction is important for peptide binding and insertion into the membranes. The secondary-structural transition of the peptide occurred at pH 4.3 in the 2,2,2-trifluoroethanol (TFE) water mixed solvent, whereas at a higher pH value (5.6) in SDS micelles, DMT1-TM4 exhibited a more stable structure in SDS micelles than that in TFE in terms of changing the pH and temperature. PAGE did not show high-molecular-mass aggregates in SDS micelles. The position of the peptide relative to SDS micelles was probed by the effects of 5- and 16-doxylstearic acids on the intensities of the peptide proton resonances. The results showed that the majority of the peptide is inserted into the hydrophobic interior of SDS micelles, whereas the C-terminal residues are surface-exposed. The ability of DMT1-TM4 to assume transmembrane features may be crucial for its biological function in vivo.
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Affiliation(s)
- Hongyan Li
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Kowloon, Hung Hom, Peoples' Republic of China
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19
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Magzoub M, Eriksson LEG, Gräslund A. Comparison of the interaction, positioning, structure induction and membrane perturbation of cell-penetrating peptides and non-translocating variants with phospholipid vesicles. Biophys Chem 2003; 103:271-88. [PMID: 12727289 DOI: 10.1016/s0301-4622(02)00321-6] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Cell-penetrating peptides (CPPs) are able to translocate and carry cargo molecules across cell membranes. Using fluorescence techniques (polarization and quenching) and CD spectroscopy we studied the interaction, conformation and topology of two such peptides, transportan and 'penetratin' (pAntp), and two variants of differing translocating abilities, with small phospholipid vesicles of varying charge density. The induced structure of transportan is always helical independent of vesicle surface charge. pAntp and its two variants interact significantly only with negatively charged vesicles. The induced secondary structure depends on membrane charge and lipid/peptide ratio. The degree of membrane perturbation, evidenced by fluorescence polarization, of pAntp and its variants is related to their secondary structure. In the helical state, the peptides have little effect on the membrane. Under conditions where pAntp and its variants are converted into beta-structures, they cause membrane perturbation. Oriented CD suggests that the two CPPs (pAntp and transportan) in their helical state lie along the vesicle surface, while the two pAntp variants appear to penetrate deeper into the membrane.
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Affiliation(s)
- Mazin Magzoub
- Department of Biochemistry and Biophysics, The Arrhenius Laboratories, Stockholm University, SE-106 91 Stockholm, Sweden
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20
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Damberg P, Jarvet J, Gräslund A. Micellar systems as solvents in peptide and protein structure determination. Methods Enzymol 2001; 339:271-85. [PMID: 11462816 DOI: 10.1016/s0076-6879(01)39318-7] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Affiliation(s)
- P Damberg
- Department of Biophysics, Stockholm University, Stockholm S-106 91, Sweden
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21
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Epand RM, Vogel HJ. Diversity of antimicrobial peptides and their mechanisms of action. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1462:11-28. [PMID: 10590300 DOI: 10.1016/s0005-2736(99)00198-4] [Citation(s) in RCA: 980] [Impact Index Per Article: 39.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Antimicrobial peptides encompass a wide variety of structural motifs. Many peptides have alpha-helical structures. The majority of these peptides are cationic and amphipathic but there are also hydrophobic alpha-helical peptides which possess antimicrobial activity. In addition, some beta-sheet peptides have antimicrobial activity and even antimicrobial alpha-helical peptides which have been modified to possess a beta-structure retain part of their antimicrobial activity. There are also antimicrobial peptides which are rich in a certain specific amino acid such as Trp or His. In addition, antimicrobial peptides exist with thio-ether rings, which are lipopeptides or which have macrocyclic Cys knots. In spite of the structural diversity, a common feature of the cationic antimicrobial peptides is that they all have an amphipathic structure which allows them to bind to the membrane interface. Indeed, most antimicrobial peptides interact with membranes and may be cytotoxic as a result of disturbance of the bacterial inner or outer membranes. Alternatively, a necessary but not sufficient property of these peptides may be to be able to pass through the membrane to reach a target inside the cell. The interaction of these peptides with biological membranes is not just a function of the peptide but is also modulated by the lipid components of the membrane. It is not likely that this diverse group of peptides has a single mechanism of action, but interaction of the peptides with membranes is an important requirement for most, if not all, antimicrobial peptides.
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Affiliation(s)
- R M Epand
- Department of Biochemistry, McMaster University Health Sciences Centre, Hamilton, Ont., Canada
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22
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Schibli DJ, Hwang PM, Vogel HJ. The structure of the antimicrobial active center of lactoferricin B bound to sodium dodecyl sulfate micelles. FEBS Lett 1999; 446:213-7. [PMID: 10100843 DOI: 10.1016/s0014-5793(99)00214-8] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Lactoferricin B (LfcinB) is a 25-residue antimicrobial peptide released from bovine lactoferrin upon pepsin digestion. The antimicrobial center of LfcinB consists of six residues (RRWQWR-NH2), and it possesses similar bactericidal activity to LfcinB. The structure of the six-residue peptide bound to sodium dodecyl sulfate (SDS) micelles has been determined by NMR spectroscopy and molecular dynamics refinement. The peptide adopts a well defined amphipathic structure when bound to SDS micelles with the Trp sidechains separated from the Arg residues. Additional evidence demonstrates that the peptide is oriented in the micelle such that the Trp residues are more deeply buried in the micelle than the Arg and Gln residues.
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Affiliation(s)
- D J Schibli
- Department of Biological Sciences, University of Calgary, Canada
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