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Královič-Kanjaková N, Asi Shirazi A, Hubčík L, Klacsová M, Keshavarzi A, Martínez JC, Combet S, Teixeira J, Uhríková D. Polymyxin B-Enriched Exogenous Lung Surfactant: Thermodynamics and Structure. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:6847-6861. [PMID: 38501650 DOI: 10.1021/acs.langmuir.3c03746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/20/2024]
Abstract
The use of an exogenous pulmonary surfactant (EPS) to deliver other relevant drugs to the lungs is a promising strategy for combined therapy. We evaluated the interaction of polymyxin B (PxB) with a clinically used EPS, the poractant alfa Curosurf (PSUR). The effect of PxB on the protein-free model system (MS) composed of four phospholipids (diC16:0PC/16:0-18:1PC/16:0-18:2PC/16:0-18:1PG) was examined in parallel to distinguish the specificity of the composition of PSUR. We used several experimental techniques (differential scanning calorimetry, small- and wide-angle X-ray scattering, small-angle neutron scattering, fluorescence spectroscopy, and electrophoretic light scattering) to characterize the binding of PxB to both EPS. Electrostatic interactions PxB-EPS are dominant. The results obtained support the concept of cationic PxB molecules lying on the surface of the PSUR bilayer, strengthening the multilamellar structure of PSUR as derived from SAXS and SANS. A protein-free MS mimics a natural EPS well but was found to be less resistant to penetration of PxB into the lipid bilayer. PxB does not affect the gel-to-fluid phase transition temperature, Tm, of PSUR, while Tm increased by ∼+ 2 °C in MS. The decrease of the thickness of the lipid bilayer (dL) of PSUR upon PxB binding is negligible. The hydrophobic tail of the PxB molecule does not penetrate the bilayer as derived from SANS data analysis and changes in lateral pressure monitored by excimer fluorescence at two depths of the hydrophobic region of the bilayer. Changes in dL of protein-free MS show a biphasic dependence on the adsorbed amount of PxB with a minimum close to the point of electroneutrality of the mixture. Our results do not discourage the concept of a combined treatment with PxB-enriched Curosurf. However, the amount of PxB must be carefully assessed (less than 5 wt % relative to the mass of the surfactant) to avoid inversion of the surface charge of the membrane.
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Affiliation(s)
- Nina Královič-Kanjaková
- Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University Bratislava, 832 32 Bratislava, Slovakia
| | - Ali Asi Shirazi
- Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University Bratislava, 832 32 Bratislava, Slovakia
| | - Lukáš Hubčík
- Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University Bratislava, 832 32 Bratislava, Slovakia
| | - Mária Klacsová
- Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University Bratislava, 832 32 Bratislava, Slovakia
| | - Atoosa Keshavarzi
- Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University Bratislava, 832 32 Bratislava, Slovakia
| | | | - Sophie Combet
- Laboratoire Léon-Brillouin (LLB), UMR12 CEA, CNRS, Université Paris-Saclay, F-91191 Gif-sur-Yvette CEDEX, France
| | - José Teixeira
- Laboratoire Léon-Brillouin (LLB), UMR12 CEA, CNRS, Université Paris-Saclay, F-91191 Gif-sur-Yvette CEDEX, France
| | - Daniela Uhríková
- Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University Bratislava, 832 32 Bratislava, Slovakia
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Walther FJ, Waring AJ. Structure and Function of Canine SP-C Mimic Proteins in Synthetic Surfactant Lipid Dispersions. Biomedicines 2024; 12:163. [PMID: 38255268 PMCID: PMC10813813 DOI: 10.3390/biomedicines12010163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 01/03/2024] [Accepted: 01/08/2024] [Indexed: 01/24/2024] Open
Abstract
Lung surfactant is a mixture of lipids and proteins and is essential for air breathing in mammals. The hydrophobic surfactant proteins B and C (SP-B and SP-C) assist in reducing surface tension in the lung alveoli by organizing the surfactant lipids. SP-B deficiency is life-threatening, and a lack of SP-C can lead to progressive interstitial lung disease. B-YL (41 amino acids) is a highly surface-active, sulfur-free peptide mimic of SP-B (79 amino acids) in which the four cysteine residues are replaced by tyrosine. Mammalian SP-C (35 amino acids) contains two cysteine-linked palmitoyl groups at positions 5 and 6 in the N-terminal region that override the β-sheet propensities of the native sequence. Canine SP-C (34 amino acids) is exceptional because it has only one palmitoylated cysteine residue at position 4 and a phenylalanine at position 5. We developed canine SP-C constructs in which the palmitoylated cysteine residue at position 4 is replaced by phenylalanine (SP-Cff) or serine (SP-Csf) and a glutamic acid-lysine ion-lock was placed at sequence positions 20-24 of the hydrophobic helical domain to enhance its alpha helical propensity. AI modeling, molecular dynamics, circular dichroism spectroscopy, Fourier Transform InfraRed spectroscopy, and electron spin resonance studies showed that the secondary structure of canine SP-Cff ion-lock peptide was like that of native SP-C, suggesting that substitution of phenylalanine for cysteine has no apparent effect on the secondary structure of the peptide. Captive bubble surfactometry demonstrated higher surface activity for canine SP-Cff ion-lock peptide in combination with B-YL in surfactant lipids than with canine SP-Csf ion-lock peptide. These studies demonstrate the potential of canine SP-Cff ion-lock peptide to enhance the functionality of the SP-B peptide mimic B-YL in synthetic surfactant lipids.
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Affiliation(s)
- Frans J. Walther
- Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, CA 90502, USA
- Department of Pediatrics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Alan J. Waring
- Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, CA 90502, USA
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
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Waring AJ, Whitelegge JP, Sharma SK, Gordon LM, Walther FJ. Emulation of the structure of the Saposin protein fold by a lung surfactant peptide construct of surfactant Protein B. PLoS One 2022; 17:e0276787. [PMID: 36327300 PMCID: PMC9632872 DOI: 10.1371/journal.pone.0276787] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 10/14/2022] [Indexed: 11/06/2022] Open
Abstract
The three-dimensional structure of the synthetic lung Surfactant Protein B Peptide Super Mini-B was determined using an integrative experimental approach, including mass spectrometry and isotope enhanced Fourier-transform infrared (FTIR) spectroscopy. Mass spectral analysis of the peptide, oxidized by solvent assisted region-specific disulfide formation, confirmed that the correct folding and disulfide pairing could be facilitated using two different oxidative structure-promoting solvent systems. Residue specific analysis by isotope enhanced FTIR indicated that the N-terminal and C-terminal domains have well defined α-helical amino acid sequences. Using these experimentally derived measures of distance constraints and disulfide connectivity, the ensemble was further refined with molecular dynamics to provide a medium resolution, residue-specific structure for the peptide construct in a simulated synthetic lung surfactant lipid multilayer environment. The disulfide connectivity combined with the α-helical elements stabilize the peptide conformationally to form a helical hairpin structure that resembles critical elements of the Saposin protein fold of the predicted full-length Surfactant Protein B structure.
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Affiliation(s)
- Alan J. Waring
- Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, California, United States of America
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Julian P. Whitelegge
- Jane & Terry Semel Institute for Neuroscience and Human Behavior, Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Shantanu K. Sharma
- Materials and Process Simulation Center, California Institute of Technology, Pasadena, California, United States of America
| | - Larry M. Gordon
- Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, California, United States of America
| | - Frans J. Walther
- Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, California, United States of America
- Department of Pediatrics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
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4
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The lung surfactant activity probed with molecular dynamics simulations. Adv Colloid Interface Sci 2022; 304:102659. [PMID: 35421637 DOI: 10.1016/j.cis.2022.102659] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Revised: 03/18/2022] [Accepted: 03/31/2022] [Indexed: 01/17/2023]
Abstract
The surface of pulmonary alveolar subphase is covered with a mixture of lipids and proteins. This lung surfactant plays a crucial role in lung functioning. It shows a complex phase behavior which can be altered by the interaction with third molecules such as drugs or pollutants. For studying multicomponent biological systems, it is of interest to couple experimental approach with computational modelling yielding atomic-scale information. Simple two, three, or four-component model systems showed to be useful for getting more insight in the interaction between lipids, lipids and proteins or lipids and proteins with drugs and impurities. These systems were studied theoretically using molecular dynamic simulations and experimentally by means of the Langmuir technique. A better understanding of the structure and behavior of lung surfactants obtained from this research is relevant for developing new synthetic surfactants for efficient therapies, and may contribute to public health protection.
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Structural hallmarks of lung surfactant: Lipid-protein interactions, membrane structure and future challenges. Arch Biochem Biophys 2021; 703:108850. [PMID: 33753033 DOI: 10.1016/j.abb.2021.108850] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 02/20/2021] [Accepted: 03/16/2021] [Indexed: 11/23/2022]
Abstract
Lung surfactant (LS) is an outstanding example of how a highly regulated and dynamic membrane-based system has evolved to sustain a wealth of structural reorganizations in order to accomplish its biophysical function, as it coats and stabilizes the respiratory air-liquid interface in the mammalian lung. The present review dissects the complexity of the structure-function relationships in LS through an updated description of the lipid-protein interactions and the membrane structures that sustain its synthesis, secretion, interfacial performance and recycling. We also revise the current models and the biophysical techniques employed to study the membranous architecture of LS. It is important to consider that the structure and functional properties of LS are often studied in bulk or under static conditions, in spite that surfactant function is strongly connected with a highly dynamic behaviour, sustained by very polymorphic structures and lipid-lipid, lipid-protein and protein-protein interactions that reorganize in precise spatio-temporal coordinates. We have tried to underline the evidences available of the existence of such structural dynamism in LS. A last important aspect is that the synthesis and assembly of LS is a strongly regulated intracellular process to ensure the establishment of the proper interactions driving LS surface activity, while protecting the integrity of other cell membranes. The use of simplified lipid models or partial natural materials purified from animal tissues could be too simplistic to understand the true molecular mechanisms defining surfactant function in vivo. In this line, we will bring into the attention of the reader the methodological challenges and the questions still open to understand the structure-function relationships of LS at its full biological relevance.
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Oseliero Filho PL, Gerbelli BB, Fornasier F, Chaves Filho AB, Yoshinaga MY, Miyamoto S, Mortara L, Lacerda CD, Cuccovia IM, Pimentel AS, Oliveira CLP. Structure and Thermotropic Behavior of Bovine- and Porcine-Derived Exogenous Lung Surfactants. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:14514-14529. [PMID: 33210931 DOI: 10.1021/acs.langmuir.0c02224] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Two commercial exogenous pulmonary surfactants, Curosurf and Survanta, are investigated. Their thermotropic behavior and associated structural changes for the samples in bulk are characterized and described. For Survanta, the obtained results of differential scanning calorimetry showed a thermogram with three peaks on heating and only a single peak on cooling. Curosurf on the other hand, presents calorimetric thermograms with only one peak in both the heating and cooling scans. This distinct thermotropic behavior between the two pulmonary surfactants, a consequence of their particular compositions, is associated with structural changes that were evaluated by simultaneous small- and wide-angle X-ray scattering experiments with in situ temperature variation. Interestingly, for temperatures below ∼35 °C for Curosurf and ∼53 °C for Survanta, the scattering data indicated the coexistence of two lamellar phases with different carbon chain organizations. For temperatures above these limits, the coexistence of phases disappears, giving rise to a fluid phase in both pulmonary surfactants, with multilamelar vesicles for Curosurf and unilamellar vesicles for Survanta. This process is quasi-reversible under cooling, and advanced data analysis for the scattering data indicated differences in the structural and elastic properties of the pulmonary surfactants. The detailed and systematic investigation shown in this work expands on the knowledge of the structure and thermodynamic behavior of Curosurf and Survanta, being relevant from both physiological and biophysical perspectives and also providing a basis for further studies on other types of pulmonary surfactants.
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Affiliation(s)
| | - Barbara Bianca Gerbelli
- Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo André, SP 09210-580, Brazil
| | - Franccesca Fornasier
- Departamento de Química, Pontifícia Universidade Católica do Rio de Janeiro, Rio de Janeiro, RJ 22453-900, Brazil
| | - Adriano B Chaves Filho
- Instituto de Química, Universidade de São Paulo, Avenida Prof. Lineu Prestes, Butantã, São Paulo, SP 05508-000, Brazil
| | - Marcos Yukio Yoshinaga
- Instituto de Química, Universidade de São Paulo, Avenida Prof. Lineu Prestes, Butantã, São Paulo, SP 05508-000, Brazil
| | - Sayuri Miyamoto
- Instituto de Química, Universidade de São Paulo, Avenida Prof. Lineu Prestes, Butantã, São Paulo, SP 05508-000, Brazil
| | - Laura Mortara
- Instituto de Química, Universidade de São Paulo, Avenida Prof. Lineu Prestes, Butantã, São Paulo, SP 05508-000, Brazil
| | - Caroline Dutra Lacerda
- Instituto de Química, Universidade de São Paulo, Avenida Prof. Lineu Prestes, Butantã, São Paulo, SP 05508-000, Brazil
| | - Iolanda Midea Cuccovia
- Instituto de Química, Universidade de São Paulo, Avenida Prof. Lineu Prestes, Butantã, São Paulo, SP 05508-000, Brazil
| | - André Silva Pimentel
- Departamento de Química, Pontifícia Universidade Católica do Rio de Janeiro, Rio de Janeiro, RJ 22453-900, Brazil
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Johansson J, Curstedt T. Synthetic surfactants with SP-B and SP-C analogues to enable worldwide treatment of neonatal respiratory distress syndrome and other lung diseases. J Intern Med 2019; 285:165-186. [PMID: 30357986 DOI: 10.1111/joim.12845] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Treatment of neonatal respiratory distress syndrome (RDS) using animal-derived lung surfactant preparations has reduced the mortality of handling premature infants with RDS to a 50th of that in the 1960s. The supply of animal-derived lung surfactants is limited and only a part of the preterm babies is treated. Thus, there is a need to develop well-defined synthetic replicas based on key components of natural surfactant. A synthetic product that equals natural-derived surfactants would enable cost-efficient production and could also facilitate the development of the treatments of other lung diseases than neonatal RDS. Recently the first synthetic surfactant that contains analogues of the two hydrophobic surfactant proteins B (SP-B) and SP-C entered clinical trials for the treatment of neonatal RDS. The development of functional synthetic analogues of SP-B and SP-C, however, is considerably more challenging than anticipated 30 years ago when the first structural information of the native proteins became available. For SP-B, a complex three-dimensional dimeric structure stabilized by several disulphides has necessitated the design of miniaturized analogues. The main challenge for SP-C has been the pronounced amyloid aggregation propensity of its transmembrane region. The development of a functional non-aggregating SP-C analogue that can be produced synthetically was achieved by designing the amyloidogenic native sequence so that it spontaneously forms a stable transmembrane α-helix.
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Affiliation(s)
- J Johansson
- Department of Neurobiology, Care Sciences and Society, Section for Neurogeriatrics, Karolinska Institutet, Huddinge, Sweden
| | - T Curstedt
- Laboratory for Surfactant Research, Department of Molecular Medicine and Surgery, Karolinska Institutet at Karolinska University Hospital, Stockholm, Sweden
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8
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Martínez‐Calle M, Olmeda B, Dietl P, Frick M, Pérez‐Gil J. Pulmonary surfactant protein SP‐B promotes exocytosis of lamellar bodies in alveolar type II cells. FASEB J 2018. [DOI: 10.1096/fj.201701462rr] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Marta Martínez‐Calle
- Department of Biochemistry and Molecular BiologyFaculty of BiologyComplutense UniversityMadridSpain
- Research Institute “Hospital 12 de Octubre”Complutense UniversityMadridSpain
| | - Bárbara Olmeda
- Department of Biochemistry and Molecular BiologyFaculty of BiologyComplutense UniversityMadridSpain
- Research Institute “Hospital 12 de Octubre”Complutense UniversityMadridSpain
| | - Paul Dietl
- Institute of General PhysiologyUlm UniversityUlmGermany
| | - Manfred Frick
- Institute of General PhysiologyUlm UniversityUlmGermany
| | - Jesús Pérez‐Gil
- Department of Biochemistry and Molecular BiologyFaculty of BiologyComplutense UniversityMadridSpain
- Research Institute “Hospital 12 de Octubre”Complutense UniversityMadridSpain
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9
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Sunde M, Pham CLL, Kwan AH. Molecular Characteristics and Biological Functions of Surface-Active and Surfactant Proteins. Annu Rev Biochem 2017; 86:585-608. [PMID: 28125290 DOI: 10.1146/annurev-biochem-061516-044847] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Many critical biological processes take place at hydrophobic:hydrophilic interfaces, and a wide range of organisms produce surface-active proteins and peptides that reduce surface and interfacial tension and mediate growth and development at these boundaries. Microorganisms produce both small lipid-associated peptides and amphipathic proteins that allow growth across water:air boundaries, attachment to surfaces, predation, and improved bioavailability of hydrophobic substrates. Higher-order organisms produce surface-active proteins with a wide variety of functions, including the provision of protective foam environments for vulnerable reproductive stages, evaporative cooling, and gas exchange across airway membranes. In general, the biological functions supported by these diverse polypeptides require them to have an amphipathic nature, and this is achieved by a diverse range of molecular structures, with some proteins undergoing significant conformational change or intermolecular association to generate the structures that are surface active.
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Affiliation(s)
- Margaret Sunde
- Discipline of Pharmacology, School of Medical Sciences and Australian Institute for Nanoscale Science and Technology, University of Sydney, NSW 2006, Australia; ,
| | - Chi L L Pham
- Discipline of Pharmacology, School of Medical Sciences and Australian Institute for Nanoscale Science and Technology, University of Sydney, NSW 2006, Australia; ,
| | - Ann H Kwan
- School of Life and Environmental Sciences and Australian Institute for Nanoscale Science and Technology, University of Sydney, NSW 2006, Australia;
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10
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All-atom molecular dynamics simulations of lung surfactant protein B: Structural features of SP-B promote lipid reorganization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:3082-3092. [DOI: 10.1016/j.bbamem.2016.09.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 08/30/2016] [Accepted: 09/20/2016] [Indexed: 01/07/2023]
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Walther FJ, Gordon LM, Waring AJ. Design of Surfactant Protein B Peptide Mimics Based on the Saposin Fold for Synthetic Lung Surfactants. Biomed Hub 2016; 1. [PMID: 28503550 PMCID: PMC5424708 DOI: 10.1159/000451076] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Surfactant protein (SP)-B is a 79-residue polypeptide crucial for the biophysical and physiological function of endogenous lung surfactant. SP-B is a member of the saposin or saposin-like proteins (SAPLIP) family of proteins that share an overall three-dimensional folding pattern based on secondary structures and disulfide connectivity and exhibit a wide diversity of biological functions. Here, we review the synthesis, molecular biophysics and activity of synthetic analogs of saposin proteins designed to mimic those interactions of the parent proteins with lipids that enhance interfacial activity. Saposin proteins generally interact with target lipids as either monomers or multimers via well-defined amphipathic helices, flexible hinge domains, and insertion sequences. Based on the known 3D-structural motif for the saposin family, we show how bioengineering techniques may be used to develop minimal peptide constructs that maintain desirable structural properties and activities in biomedical applications. One important application is the molecular design, synthesis and activity of Saposin mimics based on the SP-B structure. Synthetic lung surfactants containing active SP-B analogs may be potentially useful in treating diseases of surfactant deficiency or dysfunction including the neonatal respiratory distress syndrome and acute lung injury/acute respiratory distress syndrome.
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Affiliation(s)
- Frans J Walther
- Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA.,Department of Pediatrics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Larry M Gordon
- Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA
| | - Alan J Waring
- Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA.,Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
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Braide-Moncoeur O, Tran NT, Long JR. Peptide-based synthetic pulmonary surfactant for the treatment of respiratory distress disorders. Curr Opin Chem Biol 2016; 32:22-8. [DOI: 10.1016/j.cbpa.2016.02.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Revised: 02/18/2016] [Accepted: 02/21/2016] [Indexed: 12/31/2022]
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13
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Chavarha M, Loney RW, Rananavare SB, Hall SB. Hydrophobic surfactant proteins strongly induce negative curvature. Biophys J 2016; 109:95-105. [PMID: 26153706 DOI: 10.1016/j.bpj.2015.05.030] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 04/23/2015] [Accepted: 05/28/2015] [Indexed: 01/31/2023] Open
Abstract
The hydrophobic surfactant proteins SP-B and SP-C greatly accelerate the adsorption of vesicles containing the surfactant lipids to form a film that lowers the surface tension of the air/water interface in the lungs. Pulmonary surfactant enters the interface by a process analogous to the fusion of two vesicles. As with fusion, several factors affect adsorption according to how they alter the curvature of lipid leaflets, suggesting that adsorption proceeds via a rate-limiting structure with negative curvature, in which the hydrophilic face of the phospholipid leaflets is concave. In the studies reported here, we tested whether the surfactant proteins might promote adsorption by inducing lipids to adopt a more negative curvature, closer to the configuration of the hypothetical intermediate. Our experiments used x-ray diffraction to determine how the proteins in their physiological ratio affect the radius of cylindrical monolayers in the negatively curved, inverse hexagonal phase. With binary mixtures of dioleoylphosphatidylethanolamine (DOPE) and dioleoylphosphatidylcholine (DOPC), the proteins produced a dose-related effect on curvature that depended on the phospholipid composition. With DOPE alone, the proteins produced no change. With an increasing mol fraction of DOPC, the response to the proteins increased, reaching a maximum 50% reduction in cylindrical radius at 5% (w/w) protein. This change represented a doubling of curvature at the outer cylindrical surface. The change in spontaneous curvature, defined at approximately the level of the glycerol group, would be greater. Analysis of the results in terms of a Langmuir model for binding to a surface suggests that the effect of the lipids is consistent with a change in the maximum binding capacity. Our findings show that surfactant proteins can promote negative curvature, and support the possibility that they facilitate adsorption by that mechanism.
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Affiliation(s)
- Mariya Chavarha
- Department of Biochemistry & Molecular Biology, Oregon Health & Science University, Portland, Oregon; Department of Medicine, Oregon Health & Science University, Portland, Oregon; Department of Physiology & Pharmacology, Oregon Health & Science University, Portland, Oregon
| | - Ryan W Loney
- Department of Biochemistry & Molecular Biology, Oregon Health & Science University, Portland, Oregon; Department of Medicine, Oregon Health & Science University, Portland, Oregon; Department of Physiology & Pharmacology, Oregon Health & Science University, Portland, Oregon
| | | | - Stephen B Hall
- Department of Biochemistry & Molecular Biology, Oregon Health & Science University, Portland, Oregon; Department of Medicine, Oregon Health & Science University, Portland, Oregon; Department of Physiology & Pharmacology, Oregon Health & Science University, Portland, Oregon.
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Baoukina S, Tieleman DP. Computer simulations of lung surfactant. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2431-2440. [PMID: 26922885 DOI: 10.1016/j.bbamem.2016.02.030] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Revised: 02/21/2016] [Accepted: 02/23/2016] [Indexed: 01/26/2023]
Abstract
Lung surfactant lines the gas-exchange interface in the lungs and reduces the surface tension, which is necessary for breathing. Lung surfactant consists mainly of lipids with a small amount of proteins and forms a monolayer at the air-water interface connected to bilayer reservoirs. Lung surfactant function involves transfer of material between the monolayer and bilayers during the breathing cycle. Lipids and proteins are organized laterally in the monolayer; selected species are possibly preferentially transferred to bilayers. The complex 3D structure of lung surfactant and the exact roles of lipid organization and proteins remain important goals for research. We review recent simulation studies on the properties of lipid monolayers, monolayers with phase coexistence, monolayer-bilayer transformations, lipid-protein interactions, and effects of nanoparticles on lung surfactant. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Róg.
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Affiliation(s)
- Svetlana Baoukina
- Department of Biological Sciences and Centre for Molecular Simulation, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada.
| | - D Peter Tieleman
- Department of Biological Sciences and Centre for Molecular Simulation, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada.
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Hemming J, Hughes BR, Rennie AR, Tomas S, Campbell RA, Hughes AV, Arnold T, Botchway SW, Thompson KC. Environmental Pollutant Ozone Causes Damage to Lung Surfactant Protein B (SP-B). Biochemistry 2015; 54:5185-97. [PMID: 26270023 PMCID: PMC4571829 DOI: 10.1021/acs.biochem.5b00308] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Revised: 07/30/2015] [Indexed: 11/28/2022]
Abstract
Lung surfactant protein B (SP-B) is an essential protein found in the surfactant fluid at the air-water interface of the lung. Exposure to the air pollutant ozone could potentially damage SP-B and lead to respiratory distress. We have studied two peptides, one consisting of the N-terminus of SP-B [SP-B(1-25)] and the other a construct of the N- and C-termini of SP-B [SP-B(1-25,63-78)], called SMB. Exposure to dilute levels of ozone (~2 ppm) of monolayers of each peptide at the air-water interface leads to a rapid reaction, which is evident from an increase in the surface tension. Fluorescence experiments revealed that this increase in surface tension is accompanied by a loss of fluorescence from the tryptophan residue at the interface. Neutron and X-ray reflectivity experiments show that, in contrast to suggestions in the literature, the peptides are not solubilized upon oxidation but rather remain at the interface with little change in their hydration. Analysis of the product material reveals that no cleavage of the peptides occurs, but a more hydrophobic product is slowly formed together with an increased level of oligomerization. We attributed this to partial unfolding of the peptides. Experiments conducted in the presence of phospholipids reveal that the presence of the lipids does not prevent oxidation of the peptides. Our results strongly suggest that exposure to low levels of ozone gas will damage SP-B, leading to a change in its structure. The implication is that the oxidized protein will be impaired in its ability to interact at the air-water interface with negatively charged phosphoglycerol lipids, thus compromising what is thought to be its main biological function.
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Affiliation(s)
- Joanna
M. Hemming
- Department of Biological Sciences
and Institute of Structural and Molecular Biology, Birkbeck College, University of London, Malet Street, London WC1E
7HX, U.K.
| | - Brian R. Hughes
- Department of Biological Sciences
and Institute of Structural and Molecular Biology, Birkbeck College, University of London, Malet Street, London WC1E
7HX, U.K.
| | - Adrian R. Rennie
- Materials Physics, Department
of
Physics and Astronomy, Uppsala University, 75120 Uppsala, Sweden
| | - Salvador Tomas
- Department of Biological Sciences
and Institute of Structural and Molecular Biology, Birkbeck College, University of London, Malet Street, London WC1E
7HX, U.K.
| | - Richard A. Campbell
- Institut Laue-Langevin, 71 Avenue des Martyrs, CS20156, 38042 Grenoble Cedex 09, France
| | - Arwel V. Hughes
- ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory,
Harwell Oxford, Didcot, Oxfordshire OX11 0QX, U.K.
| | - Thomas Arnold
- Diamond
Light Source, Harwell
Science and Innovation Campus, Didcot OX11 0DE, U.K.
| | - Stanley W. Botchway
- STFC, Lasers
for Science Facility,
Central Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory,
Harwell Oxford, Didcot, Oxfordshire OX11 0FA, U.K.
| | - Katherine C. Thompson
- Department of Biological Sciences
and Institute of Structural and Molecular Biology, Birkbeck College, University of London, Malet Street, London WC1E
7HX, U.K.
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Olmeda B, García‐Álvarez B, Gómez MJ, Martínez‐Calle M, Cruz A, Pérez‐Gil J. A model for the structure and mechanism of action of pulmonary surfactant protein B. FASEB J 2015; 29:4236-47. [DOI: 10.1096/fj.15-273458] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 06/15/2015] [Indexed: 11/11/2022]
Affiliation(s)
- Bárbara Olmeda
- Departmento de Bioquímica, Facultad de BiologíaUniversidad ComplutenseMadridSpain
| | | | - Manuel J. Gómez
- Centro de Astrobiología (INTA‐CSIC), Torrejón de ArdozMadridSpain
| | - Marta Martínez‐Calle
- Departmento de Bioquímica, Facultad de BiologíaUniversidad ComplutenseMadridSpain
| | - Antonio Cruz
- Departmento de Bioquímica, Facultad de BiologíaUniversidad ComplutenseMadridSpain
| | - Jesús Pérez‐Gil
- Departmento de Bioquímica, Facultad de BiologíaUniversidad ComplutenseMadridSpain
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17
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Fernandes F, Coutinho A, Prieto M, Loura LMS. Electrostatically driven lipid-protein interaction: Answers from FRET. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:1837-48. [PMID: 25769805 DOI: 10.1016/j.bbamem.2015.02.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 02/23/2015] [Indexed: 12/13/2022]
Abstract
Electrostatics govern the association of a large number of proteins with cellular membranes. In some cases, these proteins present specialized lipid-binding modules or membrane targeting domains while in other cases association is achieved through nonspecific interaction of unstructured clusters of basic residues with negatively charged lipids. Given its spatial resolution in the nanometer range, Förster resonance energy transfer (FRET) is a powerful tool to give insight into protein-lipid interactions and provide molecular level information which is difficult to retrieve with other spectroscopic techniques. In this review we present and discuss the basic formalisms of both hetero- and homo-FRET pertinent to the most commonly encountered problems in lipid-protein interaction studies and highlight some examples of implementations of different FRET methodologies to characterize lipid/protein systems in which electrostatic interactions play a crucial role. This article is part of a Special Issue entitled: Lipid-protein interactions.
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Affiliation(s)
- Fábio Fernandes
- Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
| | - Ana Coutinho
- Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal; Dep. Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
| | - Manuel Prieto
- Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
| | - Luís M S Loura
- Faculdade de Farmácia, Universidade de Coimbra, Pólo das Ciências da Saúde, Azinhaga de Santa Comba, 3000-548 Coimbra, Portugal; Centro de Química de Coimbra, Largo D. Dinis, Rua Larga, 3004-535 Coimbra, Portugal.
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18
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Composition, structure and mechanical properties define performance of pulmonary surfactant membranes and films. Chem Phys Lipids 2014; 185:153-75. [PMID: 25260665 DOI: 10.1016/j.chemphyslip.2014.09.002] [Citation(s) in RCA: 183] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 09/06/2014] [Accepted: 09/11/2014] [Indexed: 12/30/2022]
Abstract
The respiratory surface in the mammalian lung is stabilized by pulmonary surfactant, a membrane-based system composed of multiple lipids and specific proteins, the primary function of which is to minimize the surface tension at the alveolar air-liquid interface, optimizing the mechanics of breathing and avoiding alveolar collapse, especially at the end of expiration. The goal of the present review is to summarize current knowledge regarding the structure, lipid-protein interactions and mechanical features of surfactant membranes and films and how these properties correlate with surfactant biological function inside the lungs. Surfactant mechanical properties can be severely compromised by different agents, which lead to surfactant inhibition and ultimately contributes to the development of pulmonary disorders and pathologies in newborns, children and adults. A detailed comprehension of the unique mechanical and rheological properties of surfactant layers is crucial for the diagnostics and treatment of lung diseases, either by analyzing the contribution of surfactant impairment to the pathophysiology or by improving the formulations in surfactant replacement therapies. Finally, a short review is also included on the most relevant experimental techniques currently employed to evaluate lung surfactant mechanics, rheology, and inhibition and reactivation processes.
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19
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Lopez-Rodriguez E, Pérez-Gil J. Structure-function relationships in pulmonary surfactant membranes: from biophysics to therapy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:1568-85. [PMID: 24525076 DOI: 10.1016/j.bbamem.2014.01.028] [Citation(s) in RCA: 179] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2013] [Revised: 01/22/2014] [Accepted: 01/27/2014] [Indexed: 01/01/2023]
Abstract
Pulmonary surfactant is an essential lipid-protein complex to maintain an operative respiratory surface at the mammalian lungs. It reduces surface tension at the alveolar air-liquid interface to stabilise the lungs against physical forces operating along the compression-expansion breathing cycles. At the same time, surfactant integrates elements establishing a primary barrier against the entry of pathogens. Lack or deficiencies of the surfactant system are associated with respiratory pathologies, which treatment often includes supplementation with exogenous materials. The present review summarises current models on the molecular mechanisms of surfactant function, with particular emphasis in its biophysical properties to stabilise the lungs and the molecular alterations connecting impaired surfactant with diseased organs. It also provides a perspective on the current surfactant-based strategies to treat respiratory pathologies. This article is part of a Special Issue entitled: Membrane Structure and Function: Relevance in the Cell's Physiology, Pathology and Therapy.
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Affiliation(s)
- Elena Lopez-Rodriguez
- Departamento de Bioquimica y Biologia Molecular, Facultad de Biologia, Universidad Complutense de Madrid, Madrid, Spain; Institute for Functional and Applied Anatomy, Hannover Medical School, Hannover, Germany; Biomedical Research in End Stage and Obstructive Lung Disease Hannover (BREATH), German Center for Lung Research, Hannover, Germany
| | - Jesús Pérez-Gil
- Departamento de Bioquimica y Biologia Molecular, Facultad de Biologia, Universidad Complutense de Madrid, Madrid, Spain
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van Zyl JM, Smith J. Surfactant treatment before first breath for respiratory distress syndrome in preterm lambs: comparison of a peptide-containing synthetic lung surfactant with porcine-derived surfactant. Drug Des Devel Ther 2013; 7:905-16. [PMID: 24039400 PMCID: PMC3769412 DOI: 10.2147/dddt.s47270] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND In a recent study utilizing a saline-lavaged adult rabbit model, we described a significant improvement in systemic oxygenation and pulmonary shunt after the instillation of a novel synthetic peptide-containing surfactant, Synsurf. Respiratory distress syndrome in the preterm lamb more closely resembles that of the human infant, as their blood gas, pH values, and lung mechanics deteriorate dramatically from birth despite ventilator support. Moreover, premature lambs have lungs which are mechanically unstable, with the advantage of being able to measure multiple variables over extended periods. Our objective in this study was to investigate if Synsurf leads to improved systemic oxygenation, lung mechanics, and histology in comparison to the commercially available porcine-derived lung surfactant Curosurf® when administered before first breath in a preterm lamb model. MATERIALS AND METHODS A Cesarean section was performed under general anesthesia on 18 time-dated pregnant Dohne Merino ewes at 129-130 days gestation. The premature lambs were delivered and ventilated with an expiratory tidal volume of 6-8 mL/kg for the first 30 minutes and thereafter at 8-10 mL/kg. In a randomized controlled trial, the two surfactants tested were Synsurf and Curosurf®, both at a dose of 100 mg/kg phospholipids (1,2-dipalmitoyl-L-α-phosphatidylcholine; 90% in Synsurf, 40% in Curosurf®). A control group of animals was treated with normal saline. Measurements of physiological variables, blood gases, and lung mechanics were made before and after surfactant and saline replacement and at 15, 30, 45, 60, 90, 120, 180, 240 and 300 minutes after treatment. The study continued for 5 hours. RESULTS Surfactant treatment led to a significant improvement in oxygenation within 30 minutes, with the Synsurf group and the Curosurf® group having significantly higher ratios between arterial partial pressure of oxygen/fraction of inspired oxygen (PaO2/FiO2; P = 0.021) compared to that of the control (saline-treated) animals. Dynamic compliance improved in the three groups over time, with no intergroup differences. All of the surfactant-treated animals survived, and one in the saline group died before the study ended. Histology between groups was not different, showing mild-moderate injury patterns. DISCUSSION Treatment with surfactants before first breath clearly resulted in improved systemic oxygenation within 30 minutes of instillation. Both Synsurf- and Curosurf®-treated animals experienced similar and more sustained improvement in oxygenation and decreased calculated shunt compared to saline-treated animals.
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Affiliation(s)
- Johann M van Zyl
- Division of Pharmacology, Department of Medicine, Faculty of Medicine and Health Sciences, Stellenbosch University, Tygerberg, South Africa.
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21
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Chavarha M, Loney RW, Kumar K, Rananavare SB, Hall SB. Differential effects of the hydrophobic surfactant proteins on the formation of inverse bicontinuous cubic phases. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:16596-604. [PMID: 23140329 PMCID: PMC3514604 DOI: 10.1021/la3025364] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Prior studies have shown that the biological mixture of the two hydrophobic surfactant proteins, SP-B and SP-C, produces faster adsorption of the surfactant lipids to an air/water interface, and that they induce 1-palmitoyl-2-oleoyl phosphatidylethanolamine (POPE) to form inverse bicontinuous cubic phases. Previous studies have shown that SP-B has a much greater effect than SP-C on adsorption. If the two proteins induce faster adsorption and formation of the bicontinuous structures by similar mechanisms, then they should also have different abilities to form the cubic phases. To test this hypothesis, we measured small-angle X-ray scattering on the individual proteins combined with POPE. SP-B replicated the dose-related ability of the combined proteins to induce the cubic phases at temperatures more than 25 °C below the point at which POPE alone forms the curved inverse-hexagonal phase. With SP-C, diffraction from cubic structures was either absent or present at very low intensities only with larger amounts of protein. The correlation between the structural effects of inducing curved structures and the functional effects on the rate of adsorption fits with the model in which SP-B promotes adsorption by facilitating formation of an inversely curved, rate-limiting structure.
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Affiliation(s)
- Mariya Chavarha
- Departments of Biochemistry & Molecular Biology, Medicine, and Physiology & Pharmacology, Oregon Health & Science University, Portland, OR 97239-3098
| | - Ryan W. Loney
- Departments of Biochemistry & Molecular Biology, Medicine, and Physiology & Pharmacology, Oregon Health & Science University, Portland, OR 97239-3098
| | - Kamlesh Kumar
- Departments of Biochemistry & Molecular Biology, Medicine, and Physiology & Pharmacology, Oregon Health & Science University, Portland, OR 97239-3098
| | | | - Stephen B. Hall
- Departments of Biochemistry & Molecular Biology, Medicine, and Physiology & Pharmacology, Oregon Health & Science University, Portland, OR 97239-3098
- To whom correspondence should be addressed: Stephen B. Hall, Pulmonary & Critical Care Medicine, Mail Code UHN-67, Oregon Health & Science University, Portland, Oregon 97239-3098, Telephone: (503) 494-6667,
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22
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Olmeda B, García-Álvarez B, Pérez-Gil J. Structure–function correlations of pulmonary surfactant protein SP-B and the saposin-like family of proteins. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2012; 42:209-22. [DOI: 10.1007/s00249-012-0858-9] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Revised: 08/18/2012] [Accepted: 09/03/2012] [Indexed: 02/06/2023]
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23
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Topology and lipid selectivity of pulmonary surfactant protein SP-B in membranes: Answers from fluorescence. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:1717-25. [DOI: 10.1016/j.bbamem.2012.03.008] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Revised: 03/12/2012] [Accepted: 03/13/2012] [Indexed: 01/13/2023]
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24
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Casals C, Cañadas O. Role of lipid ordered/disordered phase coexistence in pulmonary surfactant function. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:2550-62. [PMID: 22659676 DOI: 10.1016/j.bbamem.2012.05.024] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Revised: 05/03/2012] [Accepted: 05/22/2012] [Indexed: 12/27/2022]
Abstract
The respiratory epithelium has evolved to produce a complicated network of extracellular membranes that are essential for breathing and, ultimately, survival. Surfactant membranes form a stable monolayer at the air-liquid interface with bilayer structures attached to it. By reducing the surface tension at the air-liquid interface, surfactant stabilizes the lung against collapse and facilitates inflation. The special composition of surfactant membranes results in the coexistence of two distinct micrometer-sized ordered/disordered phases maintained up to physiological temperatures. Phase coexistence might facilitate monolayer folding to form three-dimensional structures during exhalation and hence allow the film to attain minimal surface tension. These folded structures may act as a membrane reserve and attenuate the increase in membrane tension during inspiration. The present review summarizes what is known of ordered/disordered lipid phase coexistence in lung surfactant, paying attention to the possible role played by domain boundaries in the monolayer-to-multilayer transition, and the correlations of biophysical inactivation of pulmonary surfactant with alterations in phase coexistence.
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Affiliation(s)
- Cristina Casals
- Departamento de Bioquimica y Biologia Molecular, Universidad Complutense de Madrid, Madrid, Spain.
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25
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Loura LMS, Prieto M. Lateral Membrane Heterogeneity Probed by FRET Spectroscopy and Microscopy. SPRINGER SERIES ON FLUORESCENCE 2012. [DOI: 10.1007/4243_2012_59] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Vibrational circular-dichroism spectroscopy of homologous cyclic peptides designed to fold into β helices of opposite chirality. Biointerphases 2011; 6:1-7. [DOI: 10.1116/1.3548075] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Dohm MT, Brown NJ, Seurynck-Servoss SL, de la Serna JB, Barron AE. Mimicking SP-C palmitoylation on a peptoid-based SP-B analogue markedly improves surface activity. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:1663-78. [DOI: 10.1016/j.bbamem.2010.04.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Revised: 04/20/2010] [Accepted: 04/26/2010] [Indexed: 02/01/2023]
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Hydrophobic surfactant proteins induce a phosphatidylethanolamine to form cubic phases. Biophys J 2010; 98:1549-57. [PMID: 20409474 DOI: 10.1016/j.bpj.2009.12.4302] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Revised: 12/02/2009] [Accepted: 12/15/2009] [Indexed: 11/21/2022] Open
Abstract
The hydrophobic surfactant proteins SP-B and SP-C promote rapid adsorption of pulmonary surfactant to an air/water interface. Previous evidence suggests that they achieve this effect by facilitating the formation of a rate-limiting negatively curved stalk between the vesicular bilayer and the interface. To determine whether the proteins can alter the curvature of lipid leaflets, we used x-ray diffraction to investigate how the physiological mixture of these proteins affects structures formed by 1-palmitoyl-2-oleoyl phosphatidylethanolamine, which by itself undergoes the lamellar-to-inverse hexagonal phase transition at 71 degrees C. In amounts as low as 0.03% (w:w) and at temperatures as low as 57 degrees C, the proteins induce formation of bicontinuous inverse cubic phases. The proteins produce a dose-related shift of diffracted intensity to the cubic phases, with minimal evidence of other structures above 0.1% and 62 degrees C, but no change in the lattice-constants of the lamellar or cubic phases. The induction of the bicontinuous cubic phases, in which the individual lipid leaflets have the same saddle-shaped curvature as the hypothetical stalk-intermediate, supports the proposed model of how the surfactant proteins promote adsorption.
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29
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Dohm MT, Mowery BP, Czyzewski AM, Stahl SS, Gellman SH, Barron AE. Biophysical mimicry of lung surfactant protein B by random nylon-3 copolymers. J Am Chem Soc 2010; 132:7957-67. [PMID: 20481635 PMCID: PMC2981085 DOI: 10.1021/ja909734n] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Non-natural oligomers have recently shown promise as functional analogues of lung surfactant proteins B and C (SP-B and SP-C), two helical and amphiphilic proteins that are critical for normal respiration. The generation of non-natural mimics of SP-B and SP-C has previously been restricted to step-by-step, sequence-specific synthesis, which results in discrete oligomers that are intended to manifest specific structural attributes. Here we present an alternative approach to SP-B mimicry that is based on sequence-random copolymers containing cationic and lipophilic subunits. These materials, members of the nylon-3 family, are prepared by ring-opening polymerization of beta-lactams. The best of the nylon-3 polymers display promising in vitro surfactant activities in a mixed lipid film. Pulsating bubble surfactometry data indicate that films containing the most surface-active polymers attain adsorptive and dynamic-cycling properties that surpass those of discrete peptides intended to mimic SP-B. Attachment of an N-terminal octadecanoyl unit to the nylon-3 copolymers, inspired by the post-translational modifications found in SP-C, affords further improvements by reducing the percent surface area compression to reach low minimum surface tension. Cytotoxic effects of the copolymers are diminished relative to that of an SP-B-derived peptide and a peptoid-based mimic. The current study provides evidence that sequence-random copolymers can mimic the in vitro surface-active behavior of lung surfactant proteins in a mixed lipid film. These findings raise the possibility that random copolymers might be useful for developing a lung surfactant replacement, which is an attractive prospect given that such polymers are easier to prepare than are sequence-specific oligomers.
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Affiliation(s)
- Michelle T. Dohm
- Department of Chemistry, Northwestern University, 2145 N. Sheridan Rd., Evanston, Illinois 60208-3100
| | - Brendan P. Mowery
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin, 53706
| | - Ann M. Czyzewski
- Department of Chemical and Biological Engineering, Northwestern University, 2145 N. Sheridan Rd., Evanston, Illinois 60208-3100
| | - Shannon S. Stahl
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin, 53706
| | - Samuel H. Gellman
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin, 53706
| | - Annelise E. Barron
- Department of Chemical and Biological Engineering, Northwestern University, 2145 N. Sheridan Rd., Evanston, Illinois 60208-3100
- Department of Bioengineering, Stanford University, W300B James H. Clark Center, 318 Campus Drive, Stanford, California 94305-5440
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Dohm MT, Seurynck-Servoss SL, Seo J, Zuckermann RN, Barron AE. Close mimicry of lung surfactant protein B by "clicked" dimers of helical, cationic peptoids. Biopolymers 2010; 92:538-53. [PMID: 19777571 DOI: 10.1002/bip.21309] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A family of peptoid dimers developed to mimic SP-B is presented, where two amphipathic, cationic helices are linked by an achiral octameric chain. SP-B is a vital therapeutic protein in lung surfactant replacement therapy, but its large-scale isolation or chemical synthesis is impractical. Enhanced biomimicry of SP-B's disulfide-bonded structure has been previously attempted via disulfide-mediated dimerization of SP-B(1-25) and other peptide mimics, which improved surface activity relative to the monomers. Herein, the effects of disulfide- or "click"-mediated (1,3-dipolar cycloaddition) dimerization, as well as linker chemistry, on the lipid-associated surfactant activity of a peptoid monomer are described. Results revealed that the 'clicked' peptoid dimer enhanced in vitro surface activity in a DPPC:POPG:PA lipid film relative to its disulfide-bonded and monomeric counterparts in both surface balance and pulsating bubble surfactometry studies. On the pulsating bubble surfactometer, the film containing the "clicked" peptoid dimer outperformed all presented peptoid monomers and dimers, and two SP-B derived peptides, attaining an adsorbed surface tension of 22 mN m(-1), and maximum and minimum cycling values of 42 mN m(-1) and near-zero, respectively.
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Affiliation(s)
- Michelle T Dohm
- Department of Chemistry, Northwestern University, 2145 N. Sheridan Road, Evanston, IL 60208-3100, USA
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Walther FJ, Waring AJ, Hernandez-Juviel JM, Gordon LM, Wang Z, Jung CL, Ruchala P, Clark AP, Smith WM, Sharma S, Notter RH. Critical structural and functional roles for the N-terminal insertion sequence in surfactant protein B analogs. PLoS One 2010; 5:e8672. [PMID: 20084172 PMCID: PMC2805716 DOI: 10.1371/journal.pone.0008672] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Accepted: 12/18/2009] [Indexed: 01/14/2023] Open
Abstract
Background Surfactant protein B (SP-B; 79 residues) belongs to the saposin protein superfamily, and plays functional roles in lung surfactant. The disulfide cross-linked, N- and C-terminal domains of SP-B have been theoretically predicted to fold as charged, amphipathic helices, suggesting their participation in surfactant activities. Earlier structural studies with Mini-B, a disulfide-linked construct based on the N- and C-terminal regions of SP-B (i.e., ∼residues 8–25 and 63–78), confirmed that these neighboring domains are helical; moreover, Mini-B retains critical in vitro and in vivo surfactant functions of the native protein. Here, we perform similar analyses on a Super Mini-B construct that has native SP-B residues (1–7) attached to the N-terminus of Mini-B, to test whether the N-terminal sequence is also involved in surfactant activity. Methodology/Results FTIR spectra of Mini-B and Super Mini-B in either lipids or lipid-mimics indicated that these peptides share similar conformations, with primary α-helix and secondary β-sheet and loop-turns. Gel electrophoresis demonstrated that Super Mini-B was dimeric in SDS detergent-polyacrylamide, while Mini-B was monomeric. Surface plasmon resonance (SPR), predictive aggregation algorithms, and molecular dynamics (MD) and docking simulations further suggested a preliminary model for dimeric Super Mini-B, in which monomers self-associate to form a dimer peptide with a “saposin-like” fold. Similar to native SP-B, both Mini-B and Super Mini-B exhibit in vitro activity with spread films showing near-zero minimum surface tension during cycling using captive bubble surfactometry. In vivo, Super Mini-B demonstrates oxygenation and dynamic compliance that are greater than Mini-B and compare favorably to full-length SP-B. Conclusion Super Mini-B shows enhanced surfactant activity, probably due to the self-assembly of monomer peptide into dimer Super Mini-B that mimics the functions and putative structure of native SP-B.
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Affiliation(s)
- Frans J Walther
- Los Angeles Biomedical Research Institute at Harbor, University of California Los Angeles Medical Center, Torrance, California, USA.
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Frey SL, Pocivavsek L, Waring AJ, Walther FJ, Hernandez-Juviel JM, Ruchala P, Lee KYC. Functional importance of the NH2-terminal insertion sequence of lung surfactant protein B. Am J Physiol Lung Cell Mol Physiol 2009; 298:L335-47. [PMID: 20023175 DOI: 10.1152/ajplung.00190.2009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Lung surfactant protein B (SP-B) is required for proper surface activity of pulmonary surfactant. In model lung surfactant lipid systems composed of saturated and unsaturated lipids, the unsaturated lipids are removed from the film at high compression. It is thought that SP-B helps anchor these lipids closely to the monolayer in three-dimensional cylindrical structures termed "nanosilos" seen by atomic force microscopy imaging of deposited monolayers at high surface pressures. Here we explore the role of the SP-B NH(2) terminus in the formation and stability of these cylindrical structures, specifically the distribution of lipid stack height, width, and density with four SP-B truncation peptides: SP-B 1-25, SP-B 9-25, SP-B 11-25, and SP-B 1-25Nflex (prolines 2 and 4 substituted with alanine). The first nine amino acids, termed the insertion sequence and the interface seeking tryptophan residue 9, are shown to stabilize the formation of nanosilos while an increase in the insertion sequence flexibility (SP-B 1-25Nflex) may improve peptide functionality. This provides a functional understanding of the insertion sequence beyond anchoring the protein to the two-dimensional membrane lining the lung, as it also stabilizes formation of nanosilos, creating reversible repositories for fluid lipids at high compression. In lavaged, surfactant-deficient rats, instillation of a mixture of SP-B 1-25 (as a monomer or dimer) and synthetic lung lavage lipids quickly improved oxygenation and dynamic compliance, whereas SP-B 11-25 surfactants showed oxygenation and dynamic compliance values similar to that of lipids alone, demonstrating a positive correlation between formation of stable, but reversible, nanosilos and in vivo efficacy.
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Affiliation(s)
- Shelli L Frey
- Department of Chemistry, Institute for Biophysical Dynamics and James Franck Institute, The University of Chicago,929 E. 57 St., Chicago, IL 60637, USA
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Cabré EJ, Malmström J, Sutherland D, Pérez-Gil J, Otzen DE. Surfactant protein SP-B strongly modifies surface collapse of phospholipid vesicles: insights from a quartz crystal microbalance with dissipation. Biophys J 2009; 97:768-76. [PMID: 19651035 DOI: 10.1016/j.bpj.2009.04.057] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2009] [Revised: 04/26/2009] [Accepted: 04/29/2009] [Indexed: 01/04/2023] Open
Abstract
Pulmonary surfactant protein B (SP-B) facilitates the rapid transfer of phospholipids from bilayer stores into air-liquid interfacial films along the breathing cycle, and contributes to the formation of a surface-associated multilayer reservoir of surfactant to optimize the stability of the respiratory interface. To obtain more insights into the mechanisms underlying this transfer and multilayer formation, we established a simple model system that captures different features of SP-B action. We monitored the formation of supported planar bilayers from the collapse of intact phospholipid vesicles on a silica surface using a technique called quartz crystal microbalance with dissipation, which provides information on changes in membrane thickness and viscosity. At physiologically relevant concentrations, SP-B dramatically alters vesicle collapse. This manifests itself as a reduced buildup of intact vesicles on the surface before collapse, and allows the stepwise buildup of multilayered deposits. Accumulation of lipids in these multilayer deposits requires the presence of SP-B in both the receptor and the arriving membranes, surrounded by a comparable phospholipid charge. Thus, the quartz crystal microbalance with dissipation system provides a useful, simplified way to mimic the effect of surfactant protein on vesicle dynamics and permits a detailed characterization of the parameters governing reorganization of surfactant layers.
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Affiliation(s)
- Elisa J Cabré
- Departamento Bioquímica y Biología Molecular I, Facultad de Biología, Universidad Complutense, Madrid, Spain
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Cholesterol modulates the exposure and orientation of pulmonary surfactant protein SP-C in model surfactant membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:1907-15. [DOI: 10.1016/j.bbamem.2009.05.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Revised: 04/24/2009] [Accepted: 05/07/2009] [Indexed: 01/08/2023]
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Antharam VC, Elliott DW, Mills FD, Farver RS, Sternin E, Long JR. Penetration depth of surfactant peptide KL4 into membranes is determined by fatty acid saturation. Biophys J 2009; 96:4085-98. [PMID: 19450480 DOI: 10.1016/j.bpj.2008.12.3966] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Revised: 12/10/2008] [Accepted: 12/23/2008] [Indexed: 11/24/2022] Open
Abstract
KL(4) is a 21-residue functional peptide mimic of lung surfactant protein B, an essential protein for lowering surface tension in the alveoli. Its ability to modify lipid properties and restore lung compliance was investigated with circular dichroism, differential scanning calorimetry, and solid-state NMR spectroscopy. KL(4) binds fluid lamellar phase PC/PG lipid membranes and forms an amphipathic helix that alters lipid organization and acyl chain dynamics. The binding and helicity of KL(4) is dependent on the level of monounsaturation in the fatty acid chains. At physiologic temperatures, KL(4) is more peripheral and dynamic in fluid phase POPC/POPG MLVs but is deeply inserted into fluid phase DPPC/POPG vesicles, resulting in immobilization of the peptide. Substantial increases in the acyl chain order are observed in DPPC/POPG lipid vesicles with increasing levels of KL(4), and POPC/POPG lipid vesicles show small decreases in the acyl chain order parameters on addition of KL(4). Additionally, a clear effect of KL(4) on the orientation of the fluid phase PG headgroups is observed, with similar changes in both lipid environments. Near the phase transition temperature of the DPPC/POPG lipid mixtures, which is just below the physiologic temperature of lung surfactant, KL(4) causes phase separation with the DPPC remaining in a gel phase and the POPG partitioned between gel and fluid phases. The ability of KL(4) to differentially partition into lipid lamellae containing varying levels of monounsaturation and subsequent changes in curvature strain suggest a mechanism for peptide-mediated lipid organization and trafficking within the dynamic lung environment.
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Affiliation(s)
- Vijay C Antharam
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, USA
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Yang TC, McDonald M, Morrow MR, Booth V. The effect of a C-terminal peptide of surfactant protein B (SP-B) on oriented lipid bilayers, characterized by solid-state 2H- and 31P-NMR. Biophys J 2009; 96:3762-71. [PMID: 19413982 DOI: 10.1016/j.bpj.2009.02.027] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2008] [Revised: 01/29/2009] [Accepted: 02/03/2009] [Indexed: 02/02/2023] Open
Abstract
SP-B(CTERM), a cationic, helical peptide based on the essential lung surfactant protein B (SP-B), retains a significant fraction of the function of the full-length protein. Solid-state (2)H- and (31)P-NMR were used to examine the effects of SP-B(CTERM) on mechanically oriented lipid bilayer samples. SP-B(CTERM) modified the multilayer structure of bilayers composed of POPC, POPG, POPC/POPG, or bovine lipid extract surfactant (BLES), even at relatively low peptide concentrations. The (31)P spectra of BLES, which contains approximately 1% SP-B, and POPC/POPG with 1% SP-B(CTERM), look very similar, supporting a similarity in lipid interactions of SP-B(CTERM) and its parent protein, full-length SP-B. In the model systems, although the peptide interacted with both the oriented and unoriented fractions of the lipids, it interacted differently with the two fractions, as demonstrated by differences in lipid headgroup structure induced by the peptide. On the other hand, although SP-B(CTERM) induced similar disruptions in overall bilayer orientation in BLES, there was no evidence of lipid headgroup conformational changes in either the oriented or the unoriented fractions of the BLES samples. Notably, in the model lipid systems the peptide did not induce the formation of small, rapidly tumbling lipid structures, such as micelles, or of hexagonal phases, the observation of which would have provided support for functional mechanisms involving peptide-induced lipid flip-flop or stabilization of curved lipid structures, respectively.
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Affiliation(s)
- Tran-Chin Yang
- Department of Biochemistry, Memorial University of Newfoundland, St. John's, Canada
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Russell-Schulz B, Booth V, Morrow MR. Perturbation of DPPC/POPG bilayers by the N-terminal helix of lung surfactant protein SP-B: a (2)H NMR study. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 38:613-24. [PMID: 19224204 DOI: 10.1007/s00249-009-0415-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2008] [Revised: 01/30/2009] [Accepted: 02/02/2009] [Indexed: 12/21/2022]
Abstract
SP-B(8-25) is a synthetic peptide comprising the N-terminal helix of the essential lung surfactant protein SP-B. Rat lung oxygenation studies have shown that SP-B(8-25) retains some of the function of full-length SP-B. We have used deuterium nuclear magnetic resonance ((2)H-NMR) to examine the influence of SP-B(8-25) on the mixing properties of saturated PC and unsaturated PG lipids in model mixed lipid bilayers containing dipalmitoylphosphatidylcholine (DPPC) and palmitoyl-oleoyl-phosphatidylglycerol (POPG), in a molar ratio of 7:3. In the absence of the peptide, (2)H-NMR spectra of DPPC/POPG mixtures, with one or the other lipid component deuterated, indicate coexistence of large liquid crystal and gel domains over a range of about 10 degrees C through the liquid crystal to gel transition of the bilayer. Addition of SP-B(8-25) has little effect on the width of the transition but the spectra through the transition range cannot be resolved into distinct liquid crystal and gel spectral components suggesting that the peptide interferes with the tendency of the DPPC and POPG lipid components in this mixture to phase separate near the bilayer transition temperature. Quadrupole echo decay observations suggest that the peptide may also reduce differences in the correlation times for local reorientation of the two lipids. These observations suggest that SP-B(8-25) promotes a more thorough mixing of saturated PC and unsaturated PG components and may be relevant to understanding the behaviour of lung surfactant material under conditions of lateral compression which might be expected to enhance the propensity for saturated and unsaturated surfactant lipid components to segregate.
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Affiliation(s)
- Bretta Russell-Schulz
- Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St John's, NF, Canada
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Mills FD, Antharam VC, Ganesh OK, Elliott DW, McNeill SA, Long JR. The helical structure of surfactant peptide KL4 when bound to POPC: POPG lipid vesicles. Biochemistry 2008; 47:8292-300. [PMID: 18636713 PMCID: PMC2629594 DOI: 10.1021/bi702551c] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
KL 4 is a 21-residue peptide employed as a functional mimic of lung surfactant protein B, which successfully lowers surface tension in the alveoli. A mechanistic understanding of how KL 4 affects lipid properties has proven elusive as the secondary structure of KL 4 in lipid preparations has not been determined at high resolution. The sequence of KL 4 is based on the C-terminus of SP-B, a naturally occurring helical protein that binds to lipid interfaces. The spacing of the lysine residues in KL 4 precludes the formation of a canonical amphipathic alpha-helix; qualitative measurements using Raman, CD, and FTIR spectroscopies have given conflicting results as to the secondary structure of the peptide as well as its orientation in the lipid environment. Here, we present a structural model of KL 4 bound to lipid bilayers based on solid state NMR data. Double-quantum correlation experiments employing (13)C-enriched peptides were used to quantitatively determine the backbone torsion angles in KL 4 at several positions. These measurements, coupled with CD experiments, verify the helical nature of KL 4 when bound to lipids, with (phi, psi) angles that differ substantially from common values for alpha-helices of (-60, -45). The average torsion angles found for KL 4 bound to POPC:POPG lipid vesicles are (-105, -30); this deviation from ideal alpha-helical structure allows KL 4 to form an amphipathic helix at the lipid interface.
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Affiliation(s)
- Frank D Mills
- Department of Biochemistry and Molecular Biology and McKnight Brain Institute, University of Florida, Box 100245, Gainesville, Florida 32610-0245, USA
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Antharam VC, Farver RS, Kuznetsova A, Sippel KH, Mills FD, Elliott DW, Sternin E, Long JR. Interactions of the C-terminus of lung surfactant protein B with lipid bilayers are modulated by acyl chain saturation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:2544-54. [PMID: 18694722 DOI: 10.1016/j.bbamem.2008.07.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2008] [Revised: 07/02/2008] [Accepted: 07/17/2008] [Indexed: 01/14/2023]
Abstract
Lung surfactant protein B (SP-B) is critical to minimizing surface tension in the alveoli. The C-terminus of SP-B, residues 59-80, has much of the surface activity of the full protein and serves as a template for the development of synthetic surfactant replacements. The molecular mechanisms responsible for its ability to restore lung compliance were investigated with circular dichroism, differential scanning calorimetry, and (31)P and (2)H solid-state NMR spectroscopy. SP-B(59-80) forms an amphipathic helix which alters lipid organization and acyl chain dynamics in fluid lamellar phase 4:1 DPPC:POPG and 3:1 POPC:POPG MLVs. At higher levels of SP-B(59-80) in the POPC:POPG lipid system a transition to a nonlamellar phase is observed while DPPC:POPG mixtures remain in a lamellar phase. Deuterium NMR shows an increase in acyl chain order in DPPC:POPG MLVs on addition of SP-B(59-80); in POPC:POPG MLVs, acyl chain order parameters decrease. Our results indicate SP-B(59-80) penetrates deeply into DPPC:POPG bilayers and binds more peripherally to POPC:POPG bilayers. Similar behavior has been observed for KL(4), a peptide mimetic of SP-B which was originally designed using SP-B(59-80) as a template and has been clinically demonstrated to be successful in treating respiratory distress syndrome. The ability of these helical peptides to differentially partition into lipid lamellae based on their degree of monounsaturation and subsequent changes in lipid dynamics suggest a mechanism for lipid organization and trafficking within the dynamic lung environment.
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Affiliation(s)
- Vijay C Antharam
- Department of Biochemistry and Molecular Biology and McKnight Brain Institute, Box 100245, Gainesville, FL 32610-0245, USA
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40
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Pérez-Gil J. Structure of pulmonary surfactant membranes and films: the role of proteins and lipid-protein interactions. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:1676-95. [PMID: 18515069 DOI: 10.1016/j.bbamem.2008.05.003] [Citation(s) in RCA: 342] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 12/28/2007] [Revised: 04/07/2008] [Accepted: 05/06/2008] [Indexed: 01/13/2023]
Abstract
The pulmonary surfactant system constitutes an excellent example of how dynamic membrane polymorphism governs some biological functions through specific lipid-lipid, lipid-protein and protein-protein interactions assembled in highly differentiated cells. Lipid-protein surfactant complexes are assembled in alveolar pneumocytes in the form of tightly packed membranes, which are stored in specialized organelles called lamellar bodies (LB). Upon secretion of LBs, surfactant develops a membrane-based network that covers rapidly and efficiently the whole respiratory surface. This membrane-based surface layer is organized in a way that permits efficient gas exchange while optimizing the encounter of many different molecules and cells at the epithelial surface, in a cross-talk essential to keep the whole organism safe from potential pathogenic invaders. The present review summarizes what is known about the structure of the different forms of surfactant, with special emphasis on current models of the molecular organization of surfactant membrane components. The architecture and the behaviour shown by surfactant structures in vivo are interpreted, to some extent, from the interactions and the properties exhibited by different surfactant models as they have been studied in vitro, particularly addressing the possible role played by surfactant proteins. However, the limitations in structural complexity and biophysical performance of surfactant preparations reconstituted in vitro will be highlighted in particular, to allow for a proper evaluation of the significance of the experimental model systems used so far to study structure-function relationships in surfactant, and to define future challenges in the design and production of more efficient clinical surfactants.
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Affiliation(s)
- Jesús Pérez-Gil
- Departamento Bioquímica, Facultad de Biología, Universidad Complutense, Madrid, Spain.
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41
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Bräuer L, Johl M, Börgermann J, Pleyer U, Tsokos M, Paulsen FP. Detection and localization of the hydrophobic surfactant proteins B and C in human tear fluid and the human lacrimal system. Curr Eye Res 2008; 32:931-8. [PMID: 18027169 DOI: 10.1080/02713680701694369] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
PURPOSE To evaluate the expression and presence of the surfactant proteins (SP) B and C in the lacrimal apparatus at the ocular surface and in tear fluid. METHODS Expression of SP-B and SP-C was analyzed by RT-PCR in healthy lacrimal gland, conjunctiva, meibomian gland, accessory lacrimal glands, cornea, and nasolacrimal ducts. The deposition of the hydrophobic proteins SP-B and SP-C was determined by Western blot and immunohistochemistry in healthy tissues, tear fluid, and aqueous humor. RESULTS The presence of both SP-B and SP-C on mRNA and protein level was evidenced in healthy human lacrimal gland, conjunctiva, cornea, and nasolacrimal ducts. Moreover, both proteins were present in tear fluid but were absent in aqueous humor. Immunohistochemical investigations revealed production of both peptides by acinar epithelial cells of the lacrimal gland and additionally by accessory lacrimal glands of the eyelid as well as epithelial cells of the conjunctiva and nasolacrimal ducts. Immunohistochemically, healthy cornea and goblet cells revealed no reactivity. CONCLUSIONS Besides the recently detected surfactant-associated proteins SP-A and SP-D, our results show that SP-B and SP-C are also peptides of the tear film, the ocular surface, and the lacrimal apparatus. Based on the current knowledge of lowering surface tension in alveolar lung cells, a similar effect of SP-B and SP-C may be assumed concerning the tear film.
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Affiliation(s)
- Lars Bräuer
- Department of Anatomy and Cell Biology, Martin Luther University of Halle-Wittenberg, Halle/Saale, Germany.
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42
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Zeng Z, Li D, Xue W, Sun L. Structural models and surface equation of state for pulmonary surfactant monolayers. Biophys Chem 2007; 131:88-95. [DOI: 10.1016/j.bpc.2007.09.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Revised: 09/07/2007] [Accepted: 09/13/2007] [Indexed: 11/16/2022]
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Seifert M, Breitenstein D, Klenz U, Meyer MC, Galla HJ. Solubility versus electrostatics: what determines lipid/protein interaction in lung surfactant. Biophys J 2007; 93:1192-203. [PMID: 17513378 PMCID: PMC1929045 DOI: 10.1529/biophysj.107.106765] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mammalian lung surfactant is a complex lipid/protein mixture covering the alveolar interface and has the crucial function of reducing the surface tension at this boundary to minimal values. Surfactant protein SP-B plays an important role for this purpose and was the focus of many recent studies. However, the specificity of lipid/SP-B interactions is controversial. Since these investigations were accomplished at varying pH conditions (pH 5.5 and 7.0), we studied the specificity of these interactions in a dipalmitoylphosphatidylcholine (DPPC)/dipalmitoylphosphatidylglycerol (DPPG)/SP-B (4:1:0.2 mol %) model system at either pH. Mainly fluorescence microscopy and laterally resolved time-of-flight secondary ion mass spectrometry were used to reveal information about the phase behavior of the lipids and the molecular distribution of SP-B in the lipid mixture. DPPG forms separated condensed domains due to a strong hydrogen-bond network, from which the protein is mainly excluded. Considering the protein as an impurity of the lipid mixture leads to the principle of the zone melting process: an impurity is highly more soluble in a liquid phase than in a solid phase. The phase behavior effect of the lipids mainly outperforms the electrostatic interactions between DPPG and SP-B, leading to a more passively achieved colocalization of DPPC and SP-B.
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Affiliation(s)
- M Seifert
- Institute of Biochemistry and Tascon GmbH, 48149 Münster, Germany
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Seurynck-Servoss SL, Brown NJ, Dohm MT, Wu CW, Barron AE. Lipid composition greatly affects the in vitro surface activity of lung surfactant protein mimics. Colloids Surf B Biointerfaces 2007; 57:37-55. [PMID: 17287113 DOI: 10.1016/j.colsurfb.2007.01.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2006] [Revised: 01/02/2007] [Accepted: 01/03/2007] [Indexed: 10/23/2022]
Abstract
A crucial aspect of developing a functional, biomimetic lung surfactant (LS) replacement is the selection of the synthetic lipid mixture and surfactant proteins (SPs) or suitable mimics thereof. Studies elucidating the roles of different lipids and surfactant proteins in natural LS have provided critical information necessary for the development of synthetic LS replacements that offer performance comparable to the natural material. In this study, the in vitro surface-active behaviors of peptide- and peptoid-based mimics of the lung surfactant proteins, SP-B and SP-C, were investigated using three different lipid formulations. The lipid mixtures were chosen from among those commonly used for the testing and characterization of SP mimics--(1) dipalmitoyl phosphatidylcholine:palmitoyloleoyl phosphatidylglycerol 7:3 (w/w) (PCPG), (2) dipalmitoyl phosphatidylcholine:palmitoyloleoyl phosphatidylglycerol:palmitic acid 68:22:9 (w/w) (TL), and (3) dipalmitoyl phosphatidylcholine:palmitoyloleoyl phosphatidylcholine:palmitoyloleoyl phosphatidylglycerol:palmitoyloleoyl phosphatidylethanolamine:palmitoyloleoyl phosphatidylserine:cholesterol 16:10:3:1:3:2 (w/w) (IL). The lipid mixtures and lipid/peptide or lipid/peptoid formulations were characterized in vitro using a Langmuir-Wilhelmy surface balance, fluorescent microscopic imaging of surface film morphology, and a pulsating bubble surfactometer. Results show that the three lipid formulations exhibit significantly different surface-active behaviors, both in the presence and absence of SP mimics, with desirable in vitro biomimetic behaviors being greatest for the TL formulation. Specifically, the TL formulation is able to reach low-surface tensions at physiological temperature as determined by dynamic PBS and LWSB studies, and dynamic PBS studies show this to occur with a minimal amount of compression, similar to natural LS.
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Affiliation(s)
- Shannon L Seurynck-Servoss
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
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Blanco O, Pérez-Gil J. Biochemical and pharmacological differences between preparations of exogenous natural surfactant used to treat Respiratory Distress Syndrome: role of the different components in an efficient pulmonary surfactant. Eur J Pharmacol 2007; 568:1-15. [PMID: 17543939 DOI: 10.1016/j.ejphar.2007.04.035] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2006] [Revised: 04/10/2007] [Accepted: 04/17/2007] [Indexed: 12/01/2022]
Abstract
The pharmaceutical application of exogenous natural pulmonary surfactant preparations has shown its efficiency in the therapeutical treatment of infants with Respiratory Distress Syndrome. At the same time, the use of these preparations in patients with Acute Respiratory Distress Syndrome, although not still an effective therapy, shows promising results. The analysis of composition, structure and surface activity of some of the different natural surfactant preparations available today for clinical use reveals important differences, a fact that opens horizons in the optimization of new effective formulations in the treatment of the Acute Respiratory Distress Syndrome. The purpose of this review is to carry out an updating of the current models interpreting the role of the main components of pulmonary surfactant as a reference to evaluate the biochemical composition of the preparations of exogenous natural pulmonary surfactant currently in use and their apparent pharmacological effect.
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Affiliation(s)
- Odalys Blanco
- Chemical-Pharmacology-Toxicology Group, Direction of Health and Animal Production, National Center of Agropecuary Sanity, Havana, Cuba
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46
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Walther FJ, Waring AJ, Sherman MA, Zasadzinski JA, Gordon LM. Hydrophobic surfactant proteins and their analogues. Neonatology 2007; 91:303-10. [PMID: 17575474 DOI: 10.1159/000101346] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Lung surfactant is a complex mixture of phospholipids and four surfactant-associated proteins (SP-A, SP-B, SP-C and SP-D). Its major function in the lung alveolus is to reduce surface tension at the air-water interface in the terminal airways by the formation of a surface-active film enriched in surfactant lipids, hence preventing cellular collapse during respiration. Surfactant therapy using bovine or porcine lung surfactant extracts, which contain only polar lipids and native SP-B and SP-C, has dramatically improved the therapeutic outcomes of preterm infants with respiratory distress syndrome (RDS). One important goal of surfactant researchers is to replace animal-derived therapies with fully synthetic preparations based on SP-B and SP-C, produced by recombinant technology or peptide synthesis, and reconstituted with selected synthetic lipids. Here, we review recent research developments with peptide analogues of SP-B and SP-C, designed using either the known primary sequence and three-dimensional (3D) structure of the native proteins or, alternatively, the known 3D structures of closely homologous proteins. Such SP-B and SP-C mimics offer the possibility of studying the mechanisms of action of the respective native proteins, and may allow the design of optimized surfactant formulations for specific pulmonary diseases (e.g., acute lung injury (ALI) or acute respiratory distress syndrome (ARDS)). These synthetic surfactant preparations may also be a cost-saving therapeutic approach, with better quality control than may be obtained with animal-based treatments.
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Affiliation(s)
- Frans J Walther
- Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA.
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47
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Waring AJ, Walther FJ, Gordon LM, Hernandez-Juviel JM, Hong T, Sherman MA, Alonso C, Alig T, Braun A, Bacon D, Zasadzinski JA. The role of charged amphipathic helices in the structure and function of surfactant protein B. ACTA ACUST UNITED AC 2006; 66:364-74. [PMID: 16316452 DOI: 10.1111/j.1399-3011.2005.00300.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Surfactant protein B (SP-B) is essential for normal lung surfactant function. Theoretical models predict that the disulfide cross-linked, N- and C-terminal domains of SP-B fold as charged amphipathic helices, and suggest that these adjacent helices participate in critical surfactant activities. This hypothesis is tested using a disulfide-linked construct (Mini-B) based on the primary sequences of the N- and C-terminal domains. Consistent with theoretical predictions of the full-length protein, both isotope-enhanced Fourier transform infrared (FTIR) spectroscopy and molecular modeling confirm the presence of charged amphipathic alpha-helices in Mini-B. Similar to that observed with native SP-B, Mini-B in model surfactant lipid mixtures exhibits marked in vitro activity, with spread films showing near-zero minimum surface tensions during cycling using captive bubble surfactometry. In vivo, Mini-B shows oxygenation and dynamic compliance that compare favorably with that of full-length SP-B. Mini-B variants (i.e. reduced disulfides or cationic residues replaced by uncharged residues) or Mini-B fragments (i.e. unlinked N- and C-terminal domains) produced greatly attenuated in vivo and in vitro surfactant properties. Hence, the combination of structure and charge for the amphipathic alpha-helical N- and C-terminal domains are key to SP-B function.
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Affiliation(s)
- A J Waring
- Department of Medicine, Division of Infectious Diseases, UCLA School of Medicine, Center for Health Sciences, Los Angeles, CA 90095, USA.
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Serrano AG, Pérez-Gil J. Protein-lipid interactions and surface activity in the pulmonary surfactant system. Chem Phys Lipids 2006; 141:105-18. [PMID: 16600200 DOI: 10.1016/j.chemphyslip.2006.02.017] [Citation(s) in RCA: 208] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2005] [Accepted: 02/20/2006] [Indexed: 11/30/2022]
Abstract
Pulmonary surfactant is a lipid-protein complex, synthesized and secreted by the respiratory epithelium of lungs to the alveolar spaces, whose main function is to reduce the surface tension at the air-liquid interface to minimize the work of breathing. The activity of surfactant at the alveoli involves three main processes: (i) transfer of surface active molecules from the aqueous hypophase into the interface, (ii) surface tension reduction to values close to 0 mN/m during compression at expiration and (iii) re-extension of the surface active film upon expansion at inspiration. Phospholipids are the main surface active components of pulmonary surfactant, but the dynamic behaviour of phospholipids along the breathing cycle requires the necessary participation of some specific surfactant associated proteins. The present review summarizes the current knowledge on the structure, disposition and lipid-protein interactions of the hydrophobic surfactant proteins SP-B and SP-C, the two main actors participating in the surface properties of pulmonary surfactant. Some of the methodologies currently used to evaluate the surface activity of the proteins in lipid-protein surfactant preparations are also revised. Working models for the potential molecular mechanism of SP-B and SP-C are finally discussed. SP-B might act in surfactant as a sort of amphipathic tag, directing the lipid-protein complexes to insert and re-insert very efficiently into the air-liquid interface along successive breathing cycles. SP-C could be essential to maintain association of lipid-protein complexes with the interface at the highest compressed states, at the end of exhalation. The understanding of the mechanisms of action of these proteins is critical to approach the design and development of new clinical surfactant preparations for therapeutical applications.
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Affiliation(s)
- Alicia G Serrano
- Departamento de Bioquímica y Biología Molecular I, Facultad de Biología, Universidad Complutense, Jose Antonio Novais 2, Madrid, Spain
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Ryan MA, Akinbi HT, Serrano AG, Perez-Gil J, Wu H, McCormack FX, Weaver TE. Antimicrobial activity of native and synthetic surfactant protein B peptides. THE JOURNAL OF IMMUNOLOGY 2006; 176:416-25. [PMID: 16365435 DOI: 10.4049/jimmunol.176.1.416] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Surfactant protein B (SP-B) is secreted into the airspaces with surfactant phospholipids where it reduces surface tension and prevents alveolar collapse at end expiration. SP-B is a member of the saposin-like family of proteins, several of which have antimicrobial properties. SP-B lyses negatively charged liposomes and was previously reported to inhibit the growth of Escherichia coli in vitro; however, a separate study indicated that elevated levels of SP-B in the airspaces of transgenic mice did not confer resistance to infection. The goal of this study was to assess the antimicrobial properties of native SP-B and synthetic peptides derived from the native peptide. Native SP-B aggregated and killed clinical isolates of Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, and group B streptococcus by increasing membrane permeability; however, SP-B also lysed RBC, indicating that the membranolytic activity was not selective for bacteria. Both the antimicrobial and hemolytic activities of native SP-B were inhibited by surfactant phospholipids, suggesting that endogenous SP-B may not play a significant role in alveolar host defense. Synthetic peptides derived from native SP-B were effective at killing both Gram-positive and Gram-negative bacteria at low peptide concentrations (0.15-5.0 microM). The SP-B derivatives selectively lysed bacterial membranes and were more resistant to inhibition by phospholipids; furthermore, helix 1 (residues 7-22) retained significant antimicrobial activity in the presence of native surfactant. These results suggest that the role of endogenous SP-B in host defense may be limited; however, synthetic peptides derived from SP-B may be useful in the treatment of bacterial pneumonias.
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Affiliation(s)
- Marnie A Ryan
- Division of Pulmonary Biology, Cincinnati Children's Hospital Medical Center, and University of Cincinnati College of Medicine, OH 45229-3039, USA
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Cruz A, Vázquez L, Vélez M, Pérez-Gil J. Effect of pulmonary surfactant protein SP-B on the micro- and nanostructure of phospholipid films. Biophys J 2004; 86:308-20. [PMID: 14695272 PMCID: PMC1303794 DOI: 10.1016/s0006-3495(04)74106-5] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Monolayers of dipalmitoylphosphatidylcholine (DPPC) and DPPC/dipalmitoylphosphatidylglycerol (DPPG) (7:3, w/w) in the absence or in the presence of 2, 5, 10, or 20 weight percent of porcine surfactant protein SP-B were spread at the air-liquid interface of a surface balance, compressed up to surface pressures in the liquid-expanded/liquid-condensed (LE-LC) plateau of the isotherm, transferred onto mica supports, and analyzed by scanning force microscopy. In the absence of protein, the films showed micrometer-sized condensed domains with morphology and size that were analogous to those observed in situ at the air-liquid interface by epifluorescence microscopy. Scanning force microscopy permits examination of the coexisting phases at a higher resolution than previously achieved with fluorescent microscopy. Both LE and LC regions of DPPC films were heterogeneous in nature. LC microdomains contained numerous expanded-like islands whereas regions apparently liquid-expanded were covered by a condensed-like framework of interconnected nanodomains. Presence of increasing amounts of pulmonary surfactant protein SP-B affected the distribution of the LE and LC regions of DPPC and DPPC/DPPG films both at the microscopic and the nanoscopic level. The condensed microdomains became more numerous but their size decreased, resulting in an overall reduction of the amount of total LC phase in both DPPC and DPPC/DPPG films. At the nanoscopic level, SP-B also caused a marked reduction of the size of the condensed-like nanodomains in the LE phase and an increase in the length of the LE/LC interface. SP-B promotes a fine nanoscopic framework of lipid and lipid-protein nanodomains that is associated with a substantial mechanical resistance to film deformation and rupture as observed during film transference and manipulation. The effect of SP-B on the nanoscopic structure of the lipid films was greater in DPPC/DPPG than in pure DPPC films, indicating additional contributions of electrostatic lipid-protein interactions. The alterations of the nanoscopic structures of phospholipid films by SP-B provide the structural framework for the protein simultaneously sustaining structural stability as well as dynamical flexibility in surfactant films at the extreme conditions imposed by the respiratory mechanics. SP-B also formed segregated two-dimensional clusters that were associated with the boundaries between LC microdomains and the LE regions of DPPC and DPPC/DPPG films. The presence of these clusters at protein-to-lipid proportions above 2% by weight suggests that the concentration of SP-B in the surfactant lipid-protein complexes may be close to the solubility limit of the protein in the lipid films.
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Affiliation(s)
- Antonio Cruz
- Departamento de Bioquímica, Facultad de Biología, Universidad Complutense, 28040 Madrid, Spain
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