Статті в журналах: "Protein-Lipid/ Surfactant Interaction"

1

Tazhibayeva, Sagdat, Kuanyshbek Musabekov, Zhenis Kusainova, Ardak Sapieva, and Nurlan Musabekov. "Complex Formation of Polyacrylic Acid with Surfactants of Different Hydrophobicity." Applied Mechanics and Materials 752-753 (April 2015): 212–16. http://dx.doi.org/10.4028/www.scientific.net/amm.752-753.212.

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Complex formation processes of polyelectrolytes with surfactant ions are close model to protein - lipid interactions in living organisms. Furthermore, polymer – surfactant complexes are widely used as stabilizers of industrial dispersions and structurants of soil. When using the polymer-surfactant complexes the hydrophilic-lipophilic balance has the great importance. The interaction of polyacrylic acid with alkylammonium salts of different hydrophobicity: cetyltrimethylammonium bromide, dilaurildimethylammonium bromide and dioctadecyldimethylammonium chloride was studied by potentiometry, spectrophotometry, viscometry and electrophoresis methods. It was established that the complex formation of polyacrylic acid with cationic surfactants is carried out due to the electrostatic interaction between carboxyl groups of the polymer and cations of surfactants, which stabilized by hydrophobic interactions between their non-polar parts. The phenomenon of hysteresis in the change of the reduced viscosity of system surfactant /polyacrylic acid with temperature variation in the range of 20-60 °C was found. The possibility of using the complex formation process for water purification from CTAB has been shown. The degree of purification is 99.6-99.8%.

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2

Parsi, Kurosh. "Interaction of detergent sclerosants with cell membranes." Phlebology: The Journal of Venous Disease 30, no. 5 (May 14, 2014): 306–15. http://dx.doi.org/10.1177/0268355514534648.

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Commonly used detergent sclerosants including sodium tetradecyl sulphate (STS) and polidocanol (POL) are clinically used to induce endovascular fibrosis and vessel occlusion. They achieve this by lysing the endothelial lining of target vessels. These agents are surface active (surfactant) molecules that interfere with cell membranes. Surfactants have a striking similarity to the phospholipid molecules of the membrane lipid bilayer. By adsorbing at the cell membrane, surfactants disrupt the normal architecture of the lipid bilayer and reduce the surface tension. The outcome of this interaction is concentration dependent. At high enough concentrations, surfactants solubilise cell membranes resulting in cell lysis. At lower concentrations, these agents can induce a procoagulant negatively charged surface on the external aspect of the cell membrane. The interaction is also influenced by the ionic charge, molecular structure, pH and the chemical nature of the diluent (e.g. saline vs. water). The ionic charge of the surfactant molecule can influence the effect on plasma proteins and the protein contents of cell membranes. STS, an anionic detergent, denatures the tertiary complex of most proteins and in particular the clinically relevant clotting factors. By contrast, POL has no effect on proteins due to its non-ionic structure. These agents therefore exhibit remarkable differences in their interaction with lipid membranes, target cells and circulating proteins with potential implications in a range of clinical applications.

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3

Augusto, Luis, Karine Le Blay, Genevieve Auger, Didier Blanot, and Richard Chaby. "Interaction of bacterial lipopolysaccharide with mouse surfactant protein C inserted into lipid vesicles." American Journal of Physiology-Lung Cellular and Molecular Physiology 281, no. 4 (October 1, 2001): L776—L785. http://dx.doi.org/10.1152/ajplung.2001.281.4.l776.

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Infection of the respiratory tract is a frequent cause of lung pathologies, morbidity, and death. When bacterial endotoxin [lipopolysaccharide (LPS)] reaches the alveolar spaces, it encounters the lipid-rich surfactant that covers the epithelium. Although binding of hydrophilic surfactant protein (SP) A and SP-D with LPS has been established, nothing has been reported to date on possible cross talks between LPS and hydrophobic SP-B and SP-C. We designed a new binding technique based on the incorporation of surfactant components to lipid vesicles and the separation of unbound from vesicle-bound LPS on a density gradient. We found that among the different hydrophobic components of mouse surfactant separated by gel filtration or reverse-phase HPLC, only SP-C exhibited the capacity to bind to a tritium-labeled LPS. The binding of LPS to vesicles containing SP-C was saturable, temperature dependent, related to the concentrations of SP-C and LPS, and inhibitable by distinct unlabeled LPSs. Unlike SP-A and SP-D, the binding of SP-C to LPS did not require calcium ions. This LPS binding capacity of SP-C may represent another antibacterial defense mechanism of the lung.

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Seifert, M., D. Breitenstein, U. Klenz, M. C. Meyer, and H. J. Galla. "Solubility versus Electrostatics: What Determines Lipid/Protein Interaction in Lung Surfactant." Biophysical Journal 93, no. 4 (August 2007): 1192–203. http://dx.doi.org/10.1529/biophysj.107.106765.

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Herbein, Joel F., Jordan Savov, and Jo Rae Wright. "Binding and uptake of surfactant protein D by freshly isolated rat alveolar type II cells." American Journal of Physiology-Lung Cellular and Molecular Physiology 278, no. 4 (April 1, 2000): L830—L839. http://dx.doi.org/10.1152/ajplung.2000.278.4.l830.

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Alveolar type II cells secrete, internalize, and recycle pulmonary surfactant, a lipid and protein complex that increases alveolar compliance and participates in pulmonary host defense. Surfactant protein (SP) D, a collagenous C-type lectin, has recently been described as a modulator of surfactant homeostasis. Mice lacking SP-D accumulate surfactant in their alveoli and type II cell lamellar bodies, organelles adapted for recycling and secretion of surfactant. The goal of current study was to characterize the interaction of SP-D with rat type II cells. Type II cells bound SP-D in a concentration-, time-, temperature-, and calcium-dependent manner. However, SP-D binding did not alter type II cell surfactant lipid uptake. Type II cells internalized SP-D into lamellar bodies and degraded a fraction of the SP-D pool. Our results also indicated that SP-D binding sites on type II cells may differ from those on alveolar macrophages. We conclude that, in vitro, type II cells bind and recycle SP-D to lamellar bodies, but SP-D may not directly modulate surfactant uptake by type II cells.

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Cifuentes, J., J. Ruiz-Oronoz, C. Myles, B. Nieves, W. A. Carlo, and S. Matalon. "Interaction of surfactant mixtures with reactive oxygen and nitrogen species." Journal of Applied Physiology 78, no. 5 (May 1, 1995): 1800–1805. http://dx.doi.org/10.1152/jappl.1995.78.5.1800.

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Increased concentrations of partially reduced oxygen and nitrogen reactive species damage the alveolar epithelium and either cause or exacerbate surfactant deficiency. For this reason, there is a quest to identify surfactant replacement mixtures, which in addition to repleting depleted surfactant stores can also reduce the steady-state concentrations of reactive species in the alveolar space. Herein, we evaluated the ability of natural lung surfactant (NLS) and two mixtures (Exosurf and Survanta) used clinically for the correction of surfactant deficiency to scavenge hydroxyl radical-type species (.OH), generated either by the decomposition of peroxynitrite or by Fenton reagents (FeCl3 + H2O2). Exosurf or Survanta decreased .OH only when present at high lipid concentrations (6.5 mM). On the other hand, 40 microM of NLS decreased .OH concentrations from 75 +/- 2 to 53 +/- 2 microM (P < 0.05), most likely because of the interaction of .OH with protein sulfhydryl groups. Similarly, 40 microM of NLS incubated with a bolus of H2O2 (400 microM) decreased the H2O2 concentration in the supernatant by approximately 50%, due to the presence of catalase-type activity. In contrast to NLS, neither Exosurf nor Survanta scavenged H2O2, even when present at millimolar lipid concentrations. We concluded that Exosurf and Survanta contain limited antioxidant activity compared with NLS.

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7

Reilly, Kim E., Alan J. Mautone, and Richard Mendelsohn. "Fourier-transform infrared spectroscopy studies of lipid/protein interaction in pulmonary surfactant." Biochemistry 28, no. 18 (September 1989): 7368–73. http://dx.doi.org/10.1021/bi00444a033.

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Palaniyar, Nades, Ross A. Ridsdale, Stephen A. Hearn, Fred Possmayer, and George Harauz. "Formation of membrane lattice structures and their specific interactions with surfactant protein A." American Journal of Physiology-Lung Cellular and Molecular Physiology 276, no. 4 (April 1, 1999): L642—L649. http://dx.doi.org/10.1152/ajplung.1999.276.4.l642.

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Biological membranes exist in many forms, one of which is known as tubular myelin (TM). This pulmonary surfactant membranous structure contains elongated tubes that form square lattices. To understand the interaction of surfactant protein (SP) A and various lipids commonly found in TM, we undertook a series of transmission-electron-microscopic studies using purified SP-A and lipid vesicles made in vitro and also native surfactant from bovine lung. Specimens from in vitro experiments were negatively stained with 2% uranyl acetate, whereas fixed native surfactant was delipidated, embedded, and sectioned. We found that dipalmitoylphosphatidylcholine-egg phosphatidylcholine (1:1 wt/wt) bilayers formed corrugations, folds, and predominantly 47-nm-square latticelike structures. SP-A specifically interacted with these lipid bilayers and folds. We visualized other proteolipid structures that could act as intermediates for reorganizing lipids and SP-As. Such a reorganization could lead to the localization of SP-A in the lattice corners and could explain, in part, the formation of TM-like structures in vivo.

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He, Peng, Shannon Faris, Reddy Sudheer Sagabala, Payel Datta, Zihan Xu, Brian Callahan, Chunyu Wang, Benoit Boivin, Fuming Zhang, and Robert J. Linhardt. "Cholesterol Chip for the Study of Cholesterol–Protein Interactions Using SPR." Biosensors 12, no. 10 (September 25, 2022): 788. http://dx.doi.org/10.3390/bios12100788.

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Cholesterol, an important lipid in animal membranes, binds to hydrophobic pockets within many soluble proteins, transport proteins and membrane bound proteins. The study of cholesterol–protein interactions in aqueous solutions is complicated by cholesterol’s low solubility and often requires organic co-solvents or surfactant additives. We report the synthesis of a biotinylated cholesterol and immobilization of this derivative on a streptavidin chip. Surface plasmon resonance (SPR) was then used to measure the kinetics of cholesterol interaction with cholesterol-binding proteins, hedgehog protein and tyrosine phosphatase 1B.

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10

CRUZ, Antonio, Cristina CASALS, Kevin M. W. KEOUGH, and Jesús PÉREZ-GIL. "Different modes of interaction of pulmonary surfactant protein SP-B in phosphatidylcholine bilayers." Biochemical Journal 327, no. 1 (October 1, 1997): 133–38. http://dx.doi.org/10.1042/bj3270133.

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Pulmonary surfactant-associated protein B (SP-B) has been incorporated into vesicles of dipalmitoyl phosphatidylcholine (DPPC) or egg yolk phosphatidylcholine (PC) by two different procedures to characterize the dependence of lipid–protein interactions on the method of reconstitution. In method A the protein was dissolved in a small volume of either methanol or 60% (v/v) acetonitrile and injected into an aqueous phase containing phospholipid vesicles. In method B the vesicles were prepared by injection of a mixture of phospholipid and SP-B dissolved in methanol or aqueous acetonitrile. Both methods of reconstitution led to the extensive interaction of SP-B with PC bilayers as demonstrated by co-migration during centrifugation, marked protection against proteolysis, change in the fluorescence emission intensity of SP-B, and protection of SP-B tryptophan fluorescence from quenching by acrylamide. SP-B promoted the rapid adsorption of DPPC on an air/liquid interface irrespective of the method of protein reconstitution. However, the interfacial adsorption activity of SP-B reconstituted by method B remained stable for hours, but that of SP-B prepared by method A decreased with time. Electron microscopy showed that the injection of SP-B into an aqueous phase containing PC or DPPC vesicles (method A) induced a rapid aggregation of vesicles. By contrast, a much longer time was required for detecting vesicle aggregation when the protein was reconstituted by co-injection of SP-B and phospholipids (method B). The presence of 5% (w/w) SP-B in DPPC bilayers prepared by method B broadened the differential scanning calorimetry thermogram and decreased the enthalpy of the transition. In contrast, the injection of SP-B into preformed DPPC vesicles (method A) did not influence the gel-to-liquid phase transition of DPPC bilayers. Taken together, these results indicate that the mode and extent of interaction of SP-B with surfactant phospholipids depends on the conditions of preparation of lipid/protein samples, and that care should be taken in the interpretation of findings from reconstituted systems on the role of these surfactant proteins in the alveolar space.

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11

Augusto, Luis A., Monique Synguelakis, Jan Johansson, Thierry Pedron, Robert Girard, and Richard Chaby. "Interaction of Pulmonary Surfactant Protein C with CD14 and Lipopolysaccharide." Infection and Immunity 71, no. 1 (January 2003): 61–67. http://dx.doi.org/10.1128/iai.71.1.61-67.2003.

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ABSTRACT In addition to their effects on alveolar surface tension, some components of lung surfactant also have immunological functions. We found recently that the hydrophobic lung surfactant protein SP-C specifically binds to the lipid A region of lipopolysaccharide (LPS). In this study, we show that SP-C also interacts with CD14. Four observations showed cross talk between the three molecules SP-C, LPS, and CD14. (i) Like LBP, SP-C allows the binding of a fluorescent LPS to cells expressing CD14 (the other surfactant components were ineffective). (ii) Recombinant radiolabeled CD14 and SP-C (or a synthetic analog of SP-C) interact in a dose-dependent manner. (iii) LPS blocks the binding of radiolabeled CD14 to SP-C-coated wells. (iv) SP-C enhances the binding of radiolabeled CD14 to LPS-coated wells. These results, obtained with native murine SP-C and with three synthetic analogs, suggest that LPS and CD14 interact with the same region of SP-C and that binding of SP-C modifies the conformation of CD14 or the accessibility of its LPS-binding site, allowing it to bind LPS. This ability of SP-C to interact with the pattern recognition molecule CD14 extends the possible immunological targets of SP-C to a large panel of microorganisms that can enter the airways.

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12

Bates, Sandra R., Jian-Qin Tao, Kathleen Notarfrancesco, Kristine DeBolt, Henry Shuman, and Aron B. Fisher. "Effect of surfactant protein A on granular pneumocyte surfactant secretion in vitro." American Journal of Physiology-Lung Cellular and Molecular Physiology 285, no. 5 (November 2003): L1055—L1065. http://dx.doi.org/10.1152/ajplung.00271.2002.

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Surfactant secretion by lung type II cells occurs when lamellar bodies (LBs) fuse with the plasma membrane and surfactant is released into the alveolar lumen. Surfactant protein A (SP-A) blocks secretagogue-stimulated phospholipid (PL) release, even in the presence of surfactant-like lipid. The mechanism of action is not clear. We have shown previously that an antibody to LB membranes (MAb 3C9) can be used to measure LB membrane trafficking. Although the ATP-stimulated secretion of PL was blocked by SP-A, the cell association of iodinated MAb 3C9 was not altered, indicating no effect on LB movement. FM1-43 is a hydrophobic dye used to monitor the formation of fusion pores. After secretagogue exposure, the threefold enhancement of the number of FM1-43 fluorescent LBs (per 100 cells) was not altered by the presence of SP-A. Finally, there was no evidence of a large PL pool retained on the cell surface through interaction with SP-A. Thus SP-A exposure does not affect these stages in the surfactant secretory pathway of type II cells.

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PLASENCIA, Inés, Antonio CRUZ, Cristina CASALS, and Jesús PÉREZ-GIL. "Superficial disposition of the N-terminal region of the surfactant protein SP-C and the absence of specific SP-B–SP-C interactions in phospholipid bilayers." Biochemical Journal 359, no. 3 (October 25, 2001): 651–59. http://dx.doi.org/10.1042/bj3590651.

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A dansylated form of porcine surfactant-associated protein C (Dns-SP-C), bearing a single dansyl group at its N-terminal end, has been used to characterize the lipid–protein and protein–protein interactions of SP-C reconstituted in phospholipid bilayers, using fluorescence spectroscopy. The fluorescence emission spectrum of Dns-SP-C in phospholipid bilayers is similar to the spectrum of dansyl-phosphatidylethanolamine, and indicates that the N-terminal end of the protein is located at the surface of the membranes and is exposed to the aqueous environment. In membranes containing phosphatidylglycerol (PG), the fluorescence of Dns-SP-C shows a 3-fold increase with respect to the fluorescence of phosphatidylcholine (PC), suggesting that electrostatic lipid–protein interactions induce important effects on the structure and disposition of the N-terminal segment of the protein in these membranes. This effect saturates above 20% PG molar content in the bilayers. The parameters for the interaction of Dns-SP-C with PC or PG have been estimated from the changes induced in the fluorescence emission spectrum of the protein. The protein had similar Kd values for its interaction with the different phospholipids tested, of the order of a few micromolar. Cooling of Dns-SP-C-containing dipalmitoyl PC bilayers to temperatures below the phase transition of the phospholipid produced a progressive blue-shift of the fluorescence emission of the protein. This effect is interpreted as a consequence of the transfer of the N-terminal segment of the protein into less polar environments that originate during protein lateral segregation. This suggests that conformation and interactions of the N-terminal segment of SP-C could be important in regulating the lateral distribution of the protein in surfactant bilayers and monolayers. Potential SP-B–SP-C interactions have been explored by analysing fluorescence resonance energy transfer (RET) from the single tryptophan in porcine SP-B to dansyl in Dns-SP-C. RET has been detected in samples where native SP-B and Dns-SP-C were concurrently reconstituted in PC or PG bilayers. However, the analysis of the dependence of RET on the protein density excluded specific SP-B–Dns-SP-C associations.

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Van Iwaarden, J. F., J. C. Pikaar, J. Storm, E. Brouwer, J. Verhoef, R. S. Oosting, L. M. G. van Golde, and J. A. G. van Strijp. "Binding of surfactant protein A to the lipid A moiety of bacterial lipopolysaccharides." Biochemical Journal 303, no. 2 (October 15, 1994): 407–11. http://dx.doi.org/10.1042/bj3030407.

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Surfactant protein A (SP-A) enhances the phagocytosis of opsonized and non-opsonized bacteria by alveolar macrophages, but it is not known with which component of the bacterial surface it associates. We investigated the interaction of SP-A with lipopolysaccharides (LPS), which are important biologically active constituents of the outer membranes of Gram-negative bacteria. Flow cytometry was used to study the binding of fluorescein isothiocyanate-labelled SP-A either to LPS of various chain lengths coupled to magnetic beads or to Gram-negative bacteria. The binding of SP-A to LPS-coated beads was saturable, both time- and concentration-dependent, and required both Ca2+ and Na+. SP-A bound to the lipid A moiety of LPS and to LPS from either the Re-mutant of Salmonella minnesota or the J5-mutant of Escherichia coli. In contrast, it did not bind to O111 LPS of E. coli, suggesting that SP-A binds only to rough LPS. The binding of SP-A to LPS was not affected by mannan and heparin or by deglycosylation of the SP-A, indicating that the carbohydrate-binding domain and the carbohydrate moiety of SP-A are not involved in its interaction with LPS. We also observed saturable and concentration-dependent binding of SP-A to the live J5 mutant of whole E. coli, but not to its O111 mutant. In addition, Re LPS aggregated in the presence of SP-A, Ca2+ and Na+. We conclude that SP-A associates with LPS via the lipid A moiety of rough LPS and may be involved in the anti-bacterial defences of the lung.

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Kalina, M., H. Blau, S. Riklis, and V. Kravtsov. "Interaction of surfactant protein A with bacterial lipopolysaccharide may affect some biological functions." American Journal of Physiology-Lung Cellular and Molecular Physiology 268, no. 1 (January 1, 1995): L144—L151. http://dx.doi.org/10.1152/ajplung.1995.268.1.l144.

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Cultured alveolar type II cells and alveolar macrophages were found to secrete colony-stimulating factors (CSF) into the medium. Surfactant protein A (SP-A; 0.1-5 micrograms/ml) and bacterial lipopolysaccharide (LPS; 10-20 micrograms/ml) were found to upregulate the secretion of CSF (seven-fold) from these cells. However, a reversal of the stimulatory effect was observed when the two agents were added simultaneously to the cells. SP-A-enhanced phagocytosis of bacteria by alveolar macrophages was also inhibited by simultaneous addition of SP-A and LPS. Thus some biological activities attributed to either SP-A or LPS are inhibited in the simultaneous presence of the two agents. We therefore investigated the possibility of interaction and binding between SP-A and LPS molecules. Our biochemical data that include immunoblots and enzyme-linked immunosorbent assay support the notion that SP-A is capable of binding LPS, and this interaction is time and concentration dependent. The binding was partially inhibited (60%) by antibody to SP-A. The binding was calcium independent and was not affected by excess carbohydrates such as methyl alpha-D-mannopyranoside or heparin. Lipid A, the hydrophobic component of LPS, however, inhibited the SP-A-LPS interaction and also caused a partial reversal of the binding. Thus these results indicate that lipid A is associated with this binding. The biological implication of SP-A-LPS interaction, especially during inflammatory responses, is discussed.

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16

Miles, P. R., L. Bowman, K. M. K. Rao, J. E. Baatz, and L. Huffman. "Pulmonary surfactant inhibits LPS-induced nitric oxide production by alveolar macrophages." American Journal of Physiology-Lung Cellular and Molecular Physiology 276, no. 1 (January 1, 1999): L186—L196. http://dx.doi.org/10.1152/ajplung.1999.276.1.l186.

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The objectives of this investigation were 1) to report that pulmonary surfactant inhibits lipopolysaccharide (LPS)-induced nitric oxide (⋅ NO) production by rat alveolar macrophages, 2) to study possible mechanisms for this effect, and 3) to determine which surfactant component(s) is responsible. ⋅ NO produced by the cells in response to LPS is due to an inducible ⋅ NO synthase (iNOS). Surfactant inhibits LPS-induced ⋅ NO formation in a concentration-dependent manner; ⋅ NO production is inhibited by ∼50 and ∼75% at surfactant levels of 100 and 200 μg phospholipid/ml, respectively. The inhibition is not due to surfactant interference with the interaction of LPS with the cells or to disruption of the formation of iNOS mRNA. Also, surfactant does not seem to reduce ⋅ NO formation by directly affecting iNOS activity or by acting as an antioxidant or radical scavenger. However, in the presence of surfactant, there is an ∼80% reduction in the amount of LPS-induced iNOS protein in the cells. LPS-induced ⋅ NO production is inhibited by Survanta, a surfactant preparation used in replacement therapy, as well as by natural surfactant. ⋅ NO formation is not affected by the major lipid components of surfactant or by two surfactant-associated proteins, surfactant protein (SP) A or SP-C. However, the hydrophobic SP-B inhibits ⋅ NO formation in a concentration-dependent manner; ⋅ NO production is inhibited by ∼50 and ∼90% at SP-B levels of 1–2 and 10 μg/ml, respectively. These results show that lung surfactant inhibits LPS-induced ⋅ NO production by alveolar macrophages, that the effect is due to a reduction in iNOS protein levels, and that the surfactant component responsible for the reduction is SP-B.

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Sylvester, Alexander, Lauren MacEachern, Valerie Booth, and Michael R. Morrow. "Interaction of the C-Terminal Peptide of Pulmonary Surfactant Protein B (SP-B) with a Bicellar Lipid Mixture Containing Anionic Lipid." PLoS ONE 8, no. 8 (August 26, 2013): e72248. http://dx.doi.org/10.1371/journal.pone.0072248.

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Tripathi, Manish Kumar, Mohammad Yasir, Pushpendra Singh, and Rahul Shrivastava. "A Comparative Study to Explore the Effect of Different Compounds in Immune Proteins of Human Beings Against Tuberculosis: An In-silico Approach." Current Bioinformatics 15, no. 2 (March 10, 2020): 155–64. http://dx.doi.org/10.2174/1574893614666190226153553.

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Background: The lungs are directly exposed to pollutants, pathogens, allergens, and chemicals, which might lead to physiological disorders. During the Bhopal gas disaster, the lungs of the victims were exposed to various chemicals. Here, using molecular modelling studies, we describe the effects of these chemicals (Dimethyl urea, Trimethyl urea, Trimethyl isocyanurate, Alphanaphthol, Butylated hydroxytoluene and Carbaryl) on pulmonary immune proteins. Objective: In the current study, we performed molecular modelling methods like molecular docking and molecular dynamics simulation studies to identify the effects of hydrolytic products of MIC and dumped residues on the pulmonary immune proteins. Methods: Molecular docking studies of (Dimethyl urea, Trimethyl urea, Trimethyl isocyanurate, Alphanaphthol, Butylated hydroxytoluene and Carbaryl) on pulmonary immune proteins was performed using the Autodock 4.0 tool, and gromacs was used for the molecular dynamics simulation studies to get an insight into the possible mode of protein-ligand interactions. Further, in silico ADMET studies was performed using the TOPKAT protocol of discovery studio. Results: From docking studies, we found that surfactant protein-D is inhibited most by the chemicals alphanaphthol (dock score, -5.41Kcal/mole), butylated hydroxytoluene (dock score,-6.86 Kcal/mole), and carbaryl (dock score,-6.1 Kcal/mole). To test their stability, the obtained dock poses were placed in a lipid bilayer model system mimicking the pulmonary surface. Molecular dynamics simulations suggest a stable interaction between surfactant protein-D and carbaryl. Conclusion: This, study concludes that functioning of surfactant protein-D is directly or indirectly affected by the carbaryl chemical, which might account for the increased susceptibility of Bhopal gas disaster survivors to pulmonary tuberculosis.

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Sandin, Suzanne I., and Eva de Alba. "Quantitative Studies on the Interaction between Saposin-like Proteins and Synthetic Lipid Membranes." Methods and Protocols 5, no. 1 (February 16, 2022): 19. http://dx.doi.org/10.3390/mps5010019.

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Members of the saposin-fold protein family and related proteins sharing a similar fold (saposin-like proteins; SAPLIP) are peripheral-membrane binding proteins that perform essential cellular functions. Saposins and SAPLIPs are abundant in both plant and animal kingdoms, and peripherally bind to lipid membranes to play important roles in lipid transfer and hydrolysis, defense mechanisms, surfactant stabilization, and cell proliferation. However, quantitative studies on the interaction between proteins and membranes are challenging due to the different nature of the two components in relation to size, structure, chemical composition, and polarity. Using liposomes and the saposin-fold member saposin C (sapC) as model systems, we describe here a method to apply solution NMR and dynamic light scattering to study the interaction between SAPLIPs and synthetic membranes at the quantitative level. Specifically, we prove with NMR that sapC binds reversibly to the synthetic membrane in a pH-controlled manner and show the dynamic nature of its fusogenic properties with dynamic light scattering. The method can be used to infer the optimal pH for membrane binding and to determine an apparent dissociation constant (KDapp) for protein-liposome interaction. We propose that these experiments can be applied to other proteins sharing the saposin fold.

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SIDOBRE, Stéphane, Germain PUZO, and Michel RIVIÈRE. "Lipid-restricted recognition of mycobacterial lipoglycans by human pulmonary surfactant protein A: a surface-plasmon-resonance study." Biochemical Journal 365, no. 1 (July 1, 2002): 89–97. http://dx.doi.org/10.1042/bj20011659.

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The human pulmonary surfactant protein A (hSP-A), a member of the mammalian collectin family, is thought to play a key defensive role against airborne invading pulmonary pathogens, among which is Mycobacterium tuberculosis, the aetiologic agent of tuberculosis. hSP-A has been shown to promote the uptake and the phagocytosis of pathogenic bacilli through the recognition and the binding of carbohydrate motifs on the invading pathogen surface. Recently we identified lipomannan and mannosylated lipoarabinomannan (ManLAM), two major mycobacterial cell-wall lipoglycans, as potential ligands for binding of hSP-A. We demonstrated that both the terminal mannose residues and the fatty acids are critical for binding, whereas the inner arabinosyl and mannosyl domains do not participate. In the present study we developed a surface-plasmon-resonance assay to analyse the molecular basis for the recognition of ManLAM by hSP-A and to try to define further the role of the lipidic aglycone moiety. Binding of ManLAM to immobilized hSP-A was consistent with the simplest one-to-one interaction model involving a single class of carbohydrate-binding site. This observation strongly suggests that the lipid moiety of ManLAM does not directly interact with hSP-A, but is rather responsible for the macromolecular organization of the lipoglycan, which may be necessary for efficient recognition of the terminal mannosyl epitopes. The indirect, structural role of the lipoglycan lipidic component is further supported by the complete lack of interaction with hSP-A in the presence of a low concentration of mild detergent.

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Ladanyi, Erna, I. R. Miller, D. Möbius, Ronit Popovits-Biro, Y. Marikovsky, P. von Wichert, B. Müller, and K. Stalder. "Electrochemical and immunoelectron microscopy evidence of lipid-protein interaction in Langmuir-Blodgett films of the human lung surfactant." Thin Solid Films 180, no. 1-2 (November 1989): 15–21. http://dx.doi.org/10.1016/0040-6090(89)90049-7.

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22

Erpenbeck, Veit J., Delphine C. Malherbe, Stefanie Sommer, Andreas Schmiedl, Wolfram Steinhilber, Andrew J. Ghio, Norbert Krug, Jo Rae Wright, and Jens M. Hohlfeld. "Surfactant protein D increases phagocytosis and aggregation of pollen-allergen starch granules." American Journal of Physiology-Lung Cellular and Molecular Physiology 288, no. 4 (April 2005): L692—L698. http://dx.doi.org/10.1152/ajplung.00362.2004.

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Recent studies have shown that surfactant components, in particular the collectins surfactant protein (SP)-A and -D, modulate the phagocytosis of various pathogens by alveolar macrophages. This interaction might be important not only for the elimination of pathogens but also for the elimination of inhaled allergens and might explain anti-inflammatory effects of SP-A and SP-D in allergic airway inflammation. We investigated the effect of surfactant components on the phagocytosis of allergen-containing pollen starch granules (PSG) by alveolar macrophages. PSG were isolated from Dactylis glomerata or Phleum pratense, two common grass pollen allergens, and incubated with either rat or human alveolar macrophages in the presence of recombinant human SP-A, SP-A purified from patients suffering from alveolar proteinosis, a recombinant fragment of human SP-D, dodecameric recombinant rat SP-D, or the commercially available surfactant preparations Curosurf and Alveofact. Dodecameric rat recombinant SP-D enhanced binding and phagocytosis of the PSG by alveolar macrophages, whereas the recombinant fragment of human SP-D, SP-A, or the surfactant lipid preparations had no effect. In addition, recombinant rat SP-D bound to the surface of the PSG and induced aggregation. Binding, aggregation, and enhancement of phagocytosis by recombinant rat SP-D was completely blocked by EDTA and inhibited by d-maltose and to a lesser extent by d-galactose, indicating the involvement of the carbohydrate recognition domain of SP-D in these functions. The modulation of allergen phagocytosis by SP-D might play an important role in allergen clearance from the lung and thereby modulate the allergic inflammation of asthma.

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23

Liu, Siyu, Tianyu Wei, Hongyun Lu, Xiayu Liu, Ying Shi, and Qihe Chen. "Interactions between Mannosylerythritol Lipid-A and Heat-Induced Soy Glycinin Aggregates: Physical and Chemical Characteristics, Functional Properties, and Structural Effects." Molecules 27, no. 21 (October 31, 2022): 7393. http://dx.doi.org/10.3390/molecules27217393.

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Protein-surfactant interactions have a significant influence on food functionality, which has attracted increasing attention. Herein, the effect of glycolipid mannosylerythritol lipid-A (MEL-A) on the heat-induced soy glycinin (11S) aggregates was investigated by measuring the structure, binding properties, interfacial behaviors, and emulsification characteristics of the aggregates. The results showed that MEL-A led to a decrease in the surface tension, viscoelasticity, and foaming ability of the 11S aggregates. In addition, MEL-A with a concentration above critical micelle concentration (CMC) reduced the random aggregation of 11S protein after heat treatment, thus facilitating the formation of self-assembling core-shell particles composed of a core of 11S aggregates covered by MEL-A shells. Infrared spectroscopy, circular dichroism spectroscopy, fluorescence spectroscopy, and isothermal titration calorimetry also confirmed that the interaction forces between MEL-A and 11S were driven by hydrophobic interactions between the exposed hydrophobic groups of the protein and the fatty acid chains or acetyl groups of MEL-A, as well as the hydrogen bonding between mannosyl-D-erythritol groups of MEL-A and amino acids of 11S. The findings of this study indicated that such molecular interactions are responsible for the change in surface behavior and the enhancement of foaming stability and emulsifying property of 11S aggregates upon heat treatment.

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24

Casals, C., E. Miguel, and J. Perez-Gil. "Tryptophan fluorescence study on the interaction of pulmonary surfactant protein A with phospholipid vesicles." Biochemical Journal 296, no. 3 (December 15, 1993): 585–93. http://dx.doi.org/10.1042/bj2960585.

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The fluorescence characteristics of surfactant protein A (SP-A) from porcine and human bronchoalveolar lavage were determined in the presence and absence of lipids. After excitation at either 275 or 295 nm, the fluorescence emission spectrum of both proteins was characterized by two maxima at about 326 and 337 nm, indicating heterogeneity in the emission of the two tryptophan residues of SP-A, and also revealing a partially buried character for these fluorophores. Interaction of both human and porcine SP-A with various phospholipid vesicles resulted in an increase in the fluorescence emission of tryptophan without any shift in the emission wavelength maxima. This change in intrinsic fluorescence was found to be more pronounced in the presence of dipalmitoyl phosphatidylcholine (DPPC) than with dipalmitoyl phosphatidylglycerol (DPPG), DPPC/DPPG (7:3, w/w) and 1-palmitoyl-sn-glycerol-3-phosphocholine (LPC). Intrinsic fluorescence of SP-A was almost completely unaffected in the presence of egg phosphatidylcholine (egg-PC). In addition, we demonstrated a shielding of the tryptophan fluorescence from quenching by acrylamide on interaction of porcine SP-A with DPPC, DPPG or LPC. This shielding was most pronounced in the presence of DPPC. In the case of human SP-A, shielding was only observed on interaction with DPPC. From the intrinsic fluorescence measurements as well as from the quenching experiments, we concluded that the interaction of some phospholipid vesicles with SP-A produces a conformational change on the protein molecule and that the interaction of SP-A with DPPC is stronger than with other phospholipids. This interaction appeared to be independent of Ca2+ ions. Physiological ionic strength was found to be required for the interaction of SP-A with negatively charged vesicles of either DPPG or DPPC/DPPG (7:3, w/w). Intrinsic fluorescence of SP-A was sensitive to the physical state of the DPPC vesicles. The increase in intrinsic fluorescence of SP-A in the presence of DPPC vesicles was much stronger when the vesicles were in the gel state than when they were in the liquid-crystalline state. The effect produced by SP-A on the lipid vesicles was also dependent on temperature. The aggregation of DPPC, DPPC/DPPG (7:3, w/w) or dimyristoyl phosphatidylglycerol (DMPG) was many times higher below the phase-transition temperature of the corresponding phospholipids. These results strongly indicate that the interaction of SP-A with phospholipid vesicles requires the lipids to be in the gel phase.

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25

Poulain, F. R., L. Allen, M. C. Williams, R. L. Hamilton, and S. Hawgood. "Effects of surfactant apolipoproteins on liposome structure: implications for tubular myelin formation." American Journal of Physiology-Lung Cellular and Molecular Physiology 262, no. 6 (June 1, 1992): L730—L739. http://dx.doi.org/10.1152/ajplung.1992.262.6.l730.

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Tubular myelin is one of several forms of lung surfactant and may play an important role in its surface activity. To determine possible mechanisms of tubular myelin formation, we studied the effects of purified surfactant proteins (SP-A, SP-B, and SP-C) on large unilamellar dipalmitoylphosphatidylcholine-egg phosphatidylglycerol (7/3; wt/wt) liposomes. We studied different types of membrane interaction induced by the apolipoproteins and correlated these with the observed changes in ultrastructure. Aggregation was assessed by measurement of light absorbance, lysis, and fusion by measurement of the fluorescence emitted by water-soluble and lipid-soluble probes, respectively. Mixtures of the apolipoproteins and liposomes were examined in ultrastructural studies by negative staining and by thin sectioning. We found that each protein had a pronounced and distinct effect on liposome structure. SP-A caused aggregation, whereas SP-B and SP-C also caused extensive leakage of liposome contents (lysis) and some degree of lipid mixing (fusion). The disruptive effects of SP-B and to a lesser extent those of SP-C were correlated by negative staining with the appearance of bilayer disks, which tended to aggregate into large sheets. There was a marked synergy between SP-A and SP-B in the process of membrane fusion in the presence of calcium, which correlated with an early (10 min) and extensive rearrangement of the structures seen by electron microscopy followed by a delayed (24 h) appearance of small amounts of tubular myelin.

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26

PLASENCIA, Ines, Luis RIVAS, Kevin M. W. KEOUGH, Derek MARSH, and Jesús PÉREZ-GIL. "The N-terminal segment of pulmonary surfactant lipopeptide SP-C has intrinsic propensity to interact with and perturb phospholipid bilayers." Biochemical Journal 377, no. 1 (January 1, 2004): 183–93. http://dx.doi.org/10.1042/bj20030815.

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In the present study, 13-residue peptides with sequences corresponding to the native N-terminal segment of pulmonary SP-C (surfactant protein C) have been synthesized and their interaction with phospholipid bilayers characterized. The peptides are soluble in aqueous media but associate spontaneously with bilayers composed of either zwitterionic (phosphatidylcholine) or anionic (phosphatidylglycerol) phospholipids. The peptides show higher affinity for anionic than for zwitterionic membranes. Interaction of the peptides with both zwitterionic and anionic membranes promotes phospholipid vesicle aggregation, and leakage of the aqueous content of the vesicles. The lipid–peptide interaction includes a significant hydrophobic component for both zwitterionic and anionic membranes, although the interaction with phosphatidylglycerol bilayers is also electrostatic in nature. The effects of the SP-C N-terminal peptides on the membrane structure are mediated by significant perturbations of the packing order and mobility of phospholipid acyl chain segments deep in the bilayer, as detected by differential scanning calorimetry and spin-label ESR. These results suggest that the N-terminal region of SP-C, even in the absence of acylation, possesses an intrinsic propensity to interact with and perturb phospholipid bilayers, thereby potentially facilitating SP-C promoting bilayer-monolayer transitions at the alveolar spaces.

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Sohma, H., N. Matsushima, T. Watanabe, A. Hattori, Y. Kuroki, and T. Akino. "Ca2+-dependent binding of annexin IV to surfactant protein A and lamellar bodies in alveolar type II cells." Biochemical Journal 312, no. 1 (November 15, 1995): 175–81. http://dx.doi.org/10.1042/bj3120175.

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Surfactant protein A (SP-A), a lung-specific glycoprotein in pulmonary surfactant, is synthesized and secreted from the alveolar type II cells. It has been shown that SP-A is a Ca(2+)-binding protein with several binding sites and that the high-affinity site(s) is located in the C-terminal region of SP-A. In the present study we isolated the proteins from bovine lung soluble fraction that bind to SP-A in a Ca(2+)-dependent manner using DEAE-Sephacel and SP-A-conjugated Sepharose 4B. At least three different protein bands with molecular masses of 24.5, 32, and 33 kDa were observed on SDS/PAGE. The main protein, with molecular mass of 32 kDa, was identified as annexin IV by the partial-amino-acid-sequence analyses and an immunoblot analysis with anti-(annexin IV) antiserum. We also found from the immunoblot analysis that the cytosolic fraction of isolated rat alveolar type II cells contains annexin IV. In addition, when rat lung cytosol was loaded on to the lung lamellar body-conjugated Sepharose 4B in the presence of Ca2+, two proteins, with molecular masses of 32 and 60 kDa on SDS/PAGE respectively, were eluted with EGTA. The 32 kDa protein was shown to be annexin IV by an immunoblot analysis with the antiserum against annexin IV. The lung annexin IV augmented the Ca(2+)-induced aggregation of the lung lamellar bodies from rats. However, the augmentation of aggregation of the lung lamellar bodies by annexin IV was attenuated when the lamellar bodies were preincubated with polyclonal anti-SP-A antibodies. SP-A bound to annexin IV under conditions where contaminated lipid was removed. These results suggest that SP-A bound to annexin IV based on protein-protein interaction, though both proteins are phospholipid-binding proteins. All these findings suggest that the interaction between SP-A and annexin IV may have some role in alveolar type II cells.

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28

Serrano, Alicia G., Elisa J. Cabré, José M. Oviedo, Antonio Cruz, Beatriz González, Alicia Palacios, Pilar Estrada та Jesús Pérez-Gil. "Production in Escherichia coli of a recombinant C-terminal truncated precursor of surfactant protein B (rproSP-BΔc). Structure and interaction with lipid interfaces". Biochimica et Biophysica Acta (BBA) - Biomembranes 1758, № 10 (жовтень 2006): 1621–32. http://dx.doi.org/10.1016/j.bbamem.2006.07.016.

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29

Chiba, Hirofumi, Hitomi Sano, Daisuke Iwaki, Seiji Murakami, Hiroaki Mitsuzawa, Toru Takahashi, Masanori Konishi, Hiroki Takahashi, and Yoshio Kuroki. "Rat Mannose-Binding Protein A Binds CD14." Infection and Immunity 69, no. 3 (March 1, 2001): 1587–92. http://dx.doi.org/10.1128/iai.69.3.1587-1592.2001.

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ABSTRACT Lipopolysaccharide (LPS) has been known to induce inflammation by interacting with CD14, which serves as a receptor for LPS. Mannose-binding protein (MBP) belongs to the collectin subgroup of the C-type lectin superfamily, along with surfactant proteins SP-A and SP-D. We have recently demonstrated that SP-A modulates LPS-induced cellular responses by interaction with CD14 (H. Sano, H. Sohma, T. Muta, S. Nomura, D. R. Voelker, and Y. Kuroki, J. Immunol. 163:387–395, 2000) and that SP-D also interacts with CD14 (H. Sano, H. Chiba, D. Iwaki, H. Sohma, D. R. Voelker, and Y. Kuroki, J. Biol. Chem. 275:22442–22451, 2000). In this study, we examined whether MBP, a collectin highly homologous to SP-A and SP-D, could bind CD14. Recombinant rat MBP-A bound recombinant human soluble CD14 in a concentration-dependent manner. Its binding was not inhibited in the presence of excess mannose or EDTA. MBP-A bound deglycosylated CD14 treated with N-glycosidase F, neuraminidase, and O-glycosidase, indicating that MBP-A interacts with the peptide portion of CD14. Since LPS was also a ligand for the collectins, we compared the characteristics of binding of MBP-A to LPS with those of binding to CD14. MBP-A bound to lipid A fromSalmonella enterica serovar Minnesota and rough LPS (S. enterica serovar Minnesota Re595 and Escherichia coli J5, Rc), but not to smooth LPS (E. coli O26:B6 and O111:B4). Unlike CD14 binding, EDTA and excess mannose attenuated the binding of MBP-A to rough LPS. From these results, we conclude that CD14 is a novel ligand for MBP-A and that MBP-A utilizes a different mechanism for CD14 recognition from that for LPS.

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30

Xie, Qing-Mei, Jian-Su Shao та David H. Alpers. "Rat intestinal α1-antitrypsin secretion is regulated by triacylglycerol feeding". American Journal of Physiology-Gastrointestinal and Liver Physiology 276, № 6 (1 червня 1999): G1452—G1460. http://dx.doi.org/10.1152/ajpgi.1999.276.6.g1452.

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α1-Antitrypsin (AAT) is secreted by the enterocyte, but its regulation of expression, intramucosal distribution, and functional status are unclear. After corn oil gavage (plus Pluronic L-81 to block chylomicron release), rat intestine was examined for mRNA encoding AAT, immunoreactivity by light and electron microscopy, and protein content by Western blot. Species-specific antisera used were raised against both AAT and surfactant-like particle (SLP), a membrane secreted by the enterocyte in response to fat feeding. Purified luminal SLP was fractionated by Bio-Gel P-200 chromatography to assess its interaction with AAT. Triacylglycerol feeding maximally increased mucosal mRNA-encoding AAT and AAT intracellular protein content by 3 and 5 h, respectively. Immunocytochemistry revealed predominance of AAT in basolateral spaces around enterocytes and Pluronic-blocked extracellular accumulation of AAT, patterns nearly identical to those of secreted SLP. About 10% of AAT was reversibly associated with SLP. Luminal AAT was smaller (51 kDa) than mature AAT (55 kDa) and did not form a complex with pancreatic elastase. When the common bile duct was tied, excluding pancreatic proteases from the lumen, mature AAT that was cleaved by pancreatic elastase was secreted. The luminal secretion of AAT and its reversible association with SLP suggest an intracellular association and a possible role for AAT during lipid digestion and absorption.

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García-Verdugo, Ignacio, Fernando Sánchez-Barbero, Katrin Soldau, Peter S. Tobias, and Cristina Casals. "Interaction of SP-A (surfactant protein A) with bacterial rough lipopolysaccharide (Re-LPS), and effects of SP-A on the binding of Re-LPS to CD14 and LPS-binding protein." Biochemical Journal 391, no. 1 (September 26, 2005): 115–24. http://dx.doi.org/10.1042/bj20050529.

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SP-A (surfactant protein A) is a lipid-binding collectin primarily involved in innate lung immunity. SP-A interacts with the bacterial rough LPS (lipopolysaccharide) Re-LPS (Re595 mutant of LPS from Salmonella minnesota), but not with smooth LPS. In the present study, we first examined the characteristics of the interaction of human SP-A with Re-LPS. Fluorescence intensity and anisotropy measurements of FITC-labelled Re-LPS in the presence and absence of SP-A indicated that SP-A bound to Re-LPS in solution in a Ca2+-independent manner, with a dissociation constant of 2.8×10−8 M. In the presence of calcium, a high-mobility complex of SP-A and [3H]Rb-LPS (Rb mutant of LPS from Escherichia coli strain LCD 25) micelles was formed, as detected by sucrose density gradients. Re-LPS aggregation induced by SP-A was further characterized by light scattering. On the other hand, human SP-A inhibited TNF-α (tumour necrosis factor-α) secretion by human macrophage-like U937 cells stimulated with either Re-LPS or smooth LPS. We further examined the effects of human SP-A on the binding of Re-LPS to LBP (LPS-binding protein) and CD14. SP-A decreased the binding of Re-LPS to CD14, but not to LBP, as detected by cross-linking experiments with 125I-ASD-Re-LPS [125I-labelled sulphosuccinimidyl-2-(p-azidosalicylamido)-1,3-dithiopropionate derivative of Re-LPS] and fluorescence analysis with FITC-Re-LPS. When SP-A, LBP and CD14 were incubated together, SP-A reduced the ability of LBP to transfer 125I-ASD-Re-LPS to CD14. These SP-A effects were not due to the ability of SP-A to aggregate Re-LPS in the presence of calcium, since they were observed in both the absence and the presence of calcium. These studies suggest that SP-A could contribute to modulate Re-LPS responses by altering the competence of the LBP–CD14 receptor complex.

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Ogawa, A., C. L. Brown, M. A. Schlueter, B. J. Benson, J. A. Clements, and S. Hawgood. "Lung function, surfactant apoprotein content, and level of PEEP in prematurely delivered rabbits." Journal of Applied Physiology 77, no. 4 (October 1, 1994): 1840–49. http://dx.doi.org/10.1152/jappl.1994.77.4.1840.

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To study the in vivo activity of the surfactant apoproteins (SP-A, SP-B, SP-C), we administered surfactants with defined apoprotein compositions to prematurely delivered rabbit pups. Rabbits given simple phospholipid mixtures containing dipalmitoylphosphatidylcholine and phosphatidylglycerol supplemented with both SP-B and SP-C or either protein alone had significantly greater lung compliance during ventilation and lung expansion during a quasi-static pressure-volume maneuver than did saline-or lipid-treated controls. The response to the surfactants containing SP-B/C was markedly dependent on the level of end-expiratory pressure used during ventilation. When the rabbits were ventilated with a positive end-expiratory pressure (PEEP) of 4 cmH2O, lung function in the pups treated with SP-B/C was not significantly different from rabbit surfactant-treated controls. Addition of SP-A to the surfactants containing SP-B/C did not significantly further improve lung function if the pups were ventilated with a PEEP of 4 cmH2O. With a lower PEEP of 1 cmH2O, lung function in the pups given surfactants containing SP-B/C was no longer equivalent to the lung function of the rabbit surfactant-treated controls. At the lower PEEP, SP-A significantly improved lung function when it was added to surfactants containing SP-B and SP-C. No beneficial effect of SP-A was seen when the surfactant contained either SP-B or SP-C alone. We conclude that with assisted ventilation that includes a moderate level of PEEP, SP-B and SP-C significantly enhance the effect of a simple phospholipid mixture on the lung function of prematurely delivered rabbits. At lower levels of PEEP the effects of SP-B and SP-C on lung function are markedly reduced but can be restored by the addition of SP-A. Our results are consistent with the existence of cooperative protein-protein interactions in surfactant function in vivo and suggest that the response to a surfactant will be determined by both the ventilation strategy and the surfactant composition. composition.

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Seaton, Barbara A., Erika C. Crouch, Francis X. McCormack, James F. Head, Kevan L. Hartshorn, and Richard Mendelsohn. "Review: Structural determinants of pattern recognition by lung collectins." Innate Immunity 16, no. 3 (April 27, 2010): 143–50. http://dx.doi.org/10.1177/1753425910368716.

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Host defense roles for the lung collectins, surfactant protein A (SP-A) and surfactant protein D (SP-D), were first suspected in the 1980s when molecular characterization revealed their sequence homology to the acute phase reactant of serum, mannose-binding lectin. Surfactant protein A and SP-D have since been shown to play diverse and important roles in innate immunity and pulmonary homeostasis. Their location in surfactant ideally positions them to interact with air-space pathogens. Despite extensive structural similarity, the two proteins show many functional differences and considerable divergence in their interactions with microbial surface components, surfactant lipids, and other ligands. Recent crystallographic studies have provided many new insights relating to these observed differences. Although both proteins can participate in calcium-dependent interactions with sugars and other polyols, they display significant differences in the spatial orientation, charge, and hydrophobicity of their binding surfaces. Surfactant protein D appears particularly adapted to interactions with complex carbohydrates and anionic phospholipids, such as phosphatidylinositol. By contrast, SP-A shows features consistent with its preference for lipid ligands, including lipid A and the major surfactant lipid, dipalmitoylphosphatidylcholine. Current research suggests that structural biology approaches will help to elucidate the molecular basis of pulmonary collectin—ligand recognition and facilitate development of new therapeutics based upon SP-A and SP-D.

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Cañadas, Olga, Bárbara Olmeda, Alejandro Alonso, and Jesús Pérez-Gil. "Lipid–Protein and Protein–Protein Interactions in the Pulmonary Surfactant System and Their Role in Lung Homeostasis." International Journal of Molecular Sciences 21, no. 10 (May 25, 2020): 3708. http://dx.doi.org/10.3390/ijms21103708.

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Pulmonary surfactant is a lipid/protein complex synthesized by the alveolar epithelium and secreted into the airspaces, where it coats and protects the large respiratory air–liquid interface. Surfactant, assembled as a complex network of membranous structures, integrates elements in charge of reducing surface tension to a minimum along the breathing cycle, thus maintaining a large surface open to gas exchange and also protecting the lung and the body from the entrance of a myriad of potentially pathogenic entities. Different molecules in the surfactant establish a multivalent crosstalk with the epithelium, the immune system and the lung microbiota, constituting a crucial platform to sustain homeostasis, under health and disease. This review summarizes some of the most important molecules and interactions within lung surfactant and how multiple lipid–protein and protein–protein interactions contribute to the proper maintenance of an operative respiratory surface.

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35

Kuzmenko, A. I., H. Wu, J. P. Bridges, and F. X. McCormack. "Surfactant lipid peroxidation damages surfactant protein A and inhibits interactions with phospholipid vesicles." Journal of Lipid Research 45, no. 6 (March 16, 2004): 1061–68. http://dx.doi.org/10.1194/jlr.m300360-jlr200.

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36

Serrano, Alicia G., and Jesús Pérez-Gil. "Protein–lipid interactions and surface activity in the pulmonary surfactant system." Chemistry and Physics of Lipids 141, no. 1-2 (June 2006): 105–18. http://dx.doi.org/10.1016/j.chemphyslip.2006.02.017.

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Lipp, Michael M. "Monolayer Morphology and Collapse Induced by Lung Surfactant Protein: Observation Via Fluorescence and Atomic Force Microscopy." Proceedings, annual meeting, Electron Microscopy Society of America 54 (August 11, 1996): 322–23. http://dx.doi.org/10.1017/s0424820100164076.

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Understanding the role of lung surfactant specific proteins in lipid monolayers is essential for improved treatments for Respiratory Distress Syndrome, which is a leading cause of death in premature infants. Fluorescence (FM) and Atomic Force (AFM) microscopies reveal that the amino-terminal peptide of lung surfactant protein SP-B alters the behavior of palmitic acid (PA) monolayers, enhancing their in vivo performance. The combination of these techniques provides an excellent correlation between the protein-lipid interactions on the molecular level with the macroscopic properties of the monolayer.SP-B protein incorporates into monolayers of PA, an important component of natural and synthetic lung surfactants monolayers. The effect of the protein on the monolayer is evidenced in the isotherm data shown in Fig 1, in which the area per PA molecule, compressibility, and surface pressure at collapse all increase as a function of increasing protein concentration. The protein accomplishes this by inhibiting the formation of ordered phases of PA. This is seen via FM as a transition from a homogeneous, dark ordered phase without protein (Fig 2a) to a network of a disordered, bright phase (the fluorescent lipid probes used in this study prefer to partition into disordered phases, making them appear as bright regions in FM images) that separates ordered phase domains at coexistence (Fig. 2b). The network is stabilized by the low line tension between the bright phase and other lipid phases as confirmed by the formation of extended linear domains of bright phase in a dark background, or “stripe” phases (Fig. 3a) under certain subphase conditions. Similar stripe phases also occur in single component fluorescein-labeled SP-B monolayers (Fig 3b), implying that the protein is responsible for the reduction in line tension. The formation of the fluid phase network is responsible for the increased collapse resistance of these mixed monolayers. The mechanism of collapse shifts from a heterogeneous process of nucleation and growth of large rigid crystalline collapse phases (Fig. 4a) to a more homogeneous process with nucleation and growth of smaller domains distributed uniformly across the film (Fig. 4b). This is due to the protein-induced network breaking up and isolating the domains of ordered phase, effectively lowering the probability of finding a heterogeneous nucleation site within each domain (analagous to the classic experiments of Turnbull on supercooled microemulsions of metallic liquids). The partitioning of the protein into the bright phase network was confirmed through the use of a dual-probe system. Fluorescein-labeled SP-B was added to a PA monolayer incorporating a fluorescent lipid analogue that emits at a higher wavelength. Upon imaging the same region of a monolayer at the different wavelengths (Fig. 5a and 5b), the protein is seen to be located in the bright phase network regions as expected.

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Castillo-Sánchez, José Carlos, Antonio Cruz, and Jesús Pérez-Gil. "Structural hallmarks of lung surfactant: Lipid-protein interactions, membrane structure and future challenges." Archives of Biochemistry and Biophysics 703 (May 2021): 108850. http://dx.doi.org/10.1016/j.abb.2021.108850.

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39

Giudice, Rita Del, Nicolò Paracini, Tomas Laursen, Clement Blanchet, Felix Roosen-Runge, and Marité Cárdenas. "Expanding the Toolbox for Bicelle-Forming Surfactant–Lipid Mixtures." Molecules 27, no. 21 (November 7, 2022): 7628. http://dx.doi.org/10.3390/molecules27217628.

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Bicelles are disk-shaped models of cellular membranes used to study lipid–protein interactions, as well as for structural and functional studies on transmembrane proteins. One challenge for the incorporation of transmembrane proteins in bicelles is the limited range of detergent and lipid combinations available for the successful reconstitution of proteins in model membranes. This is important, as the function and stability of transmembrane proteins are very closely linked to the detergents used for their purification and to the lipids that the proteins are embedded in. Here, we expand the toolkit of lipid and detergent combinations that allow the formation of stable bicelles. We use a combination of dynamic light scattering, small-angle X-ray scattering and cryogenic electron microscopy to perform a systematic sample characterization, thus providing a set of conditions under which bicelles can be successfully formed.

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Hawgood, S. "Pulmonary surfactant apoproteins: a review of protein and genomic structure." American Journal of Physiology-Lung Cellular and Molecular Physiology 257, no. 2 (August 1, 1989): L13—L22. http://dx.doi.org/10.1152/ajplung.1989.257.2.l13.

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In recent years, as the complexity of the surfactant system has become more apparent, investigators with an increasingly diverse set of skills have been attracted to the study of this secretory product of the alveolar epithelium. In addition to advancing our knowledge of the mechanisms underlying the mechanical stability of the lung, recent studies of the surfactant system have also contributed information to less organ-specific biological phenomena such as exocytosis, endocytosis, cell differentiation and lipid-protein interactions in biomembranes. Pulmonary surfactant is not composed of a single class of molecules but, rather, is a collection of interrelated macromolecular lipoprotein complexes that differ in composition, structure, and function. The purpose of this review is to describe the structure of the lung-specific proteins that are associated with the phospholipids of surfactant in the alveolar space. The organization of the genes for the surfactant proteins is outlined and the affects of these proteins on the properties of phospholipid membranes are discussed.

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Bruni, R., H. W. Taeusch, and A. J. Waring. "Surfactant protein B: lipid interactions of synthetic peptides representing the amino-terminal amphipathic domain." Proceedings of the National Academy of Sciences 88, no. 16 (August 15, 1991): 7451–55. http://dx.doi.org/10.1073/pnas.88.16.7451.

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42

Sarker, Muzaddid, Alan J. Waring, Frans J. Walther, Kevin M. W. Keough, and Valerie Booth. "Interactions of SP-B Based Peptide with Lipid and Protein Components of Lung Surfactant." Biophysical Journal 96, no. 3 (February 2009): 609a. http://dx.doi.org/10.1016/j.bpj.2008.12.3221.

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43

Dhar, Prajnaparamita, Elizabeth Eck, Jacob N. Israelachvili, Dong Woog Lee, Younjin Min, Arun Ramachandran, Alan J. Waring, and Joseph A. Zasadzinski. "Lipid-Protein Interactions Alter Line Tensions and Domain Size Distributions in Lung Surfactant Monolayers." Biophysical Journal 102, no. 1 (January 2012): 56–65. http://dx.doi.org/10.1016/j.bpj.2011.11.4007.

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44

Dhand, Rajiv, Vijay K. Sharma, Andelle L. Teng, S. Krishnasamy, and Nicholas J. Gross. "Protein–Lipid Interactions and Enzyme Requirements for Light Subtype Generation on Cycling Reconstituted Surfactant." Biochemical and Biophysical Research Communications 244, no. 3 (March 1998): 712–19. http://dx.doi.org/10.1006/bbrc.1998.8325.

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45

Rodriguez-Capote, Karina, Kaushik Nag, Samuel Schürch, and Fred Possmayer. "Surfactant protein interactions with neutral and acidic phospholipid films." American Journal of Physiology-Lung Cellular and Molecular Physiology 281, no. 1 (July 1, 2001): L231—L242. http://dx.doi.org/10.1152/ajplung.2001.281.1.l231.

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The captive bubble tensiometer was employed to study interactions of phospholipid (PL) mixtures of dipalmitoylphosphatidylcholine (DPPC) and 1-palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine (POPC) or 1-palmitoyl-2-oleoyl- sn-glycero-3-[phospho- rac-(1-glycerol)] (POPG) at 50 μg/ml with physiological levels of the surfactant protein (SP) A SP-B, and SP-C alone and in combination at 37°C. All surfactant proteins enhanced lipid adsorption to equilibrium surface tension (γ), with SP-C being most effective. Kinetics were consistent with the presence of two adsorption phases. Under the conditions employed, SP-A did not affect the rate of film formation in the presence of SP-B or SP-C. Little difference in γmin was observed between the acidic POPG and the neutral POPC systems with SP-B or SP-C with and without SP-A. However, γmax was lower with the acidic POPG system during dynamic, but not during quasi-static, cycling. Considerably lower compression ratios were required to generate low γminvalues with SP-B than SP-C. DPPC-POPG-SP-B was superior to the neutral POPC-SP-B system. Although SP-A had little effect on film formation with SP-B, surface activity during compression was enhanced with both PL systems. In the presence of SP-C, lower compression ratios were required with the acidic system, and with this mixture, SP-A addition adversely affected surface activity. The results suggest specific interactions between SP-B and phosphatidylglycerol, and between SP-B and SP-A. These observations are consistent with the presence of a surface-associated surfactant reservoir which is involved in generating low γ during film compression and lipid respreading during film expansion.

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46

Douliez, Jean-Paul, Denise Sy, Françoise Vovelle, and Didier Marion. "Interaction of Surfactants and Polymer-Grafted Lipids with a Plant Lipid Transfer Protein, LTP1." Langmuir 18, no. 20 (October 2002): 7309–12. http://dx.doi.org/10.1021/la020163w.

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47

Khatami, Mohammad Hassan, Ivan Saika-Voivod, and Valerie Booth. "Experimental and Computational Studies of Pulmonary Surfactant Protein SP-B Interacting with Lipid Bilayers." Biophysical Journal 108, no. 2 (January 2015): 38a. http://dx.doi.org/10.1016/j.bpj.2014.11.236.

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48

Robichaud, Nicholas A. S., Mohammad Hassan Khatami, Ivan Saika-Voivod, and Valerie Booth. "All-Atom Molecular Dynamics Simulations of Dimeric Lung Surfactant Protein B in Lipid Multilayers." International Journal of Molecular Sciences 20, no. 16 (August 8, 2019): 3863. http://dx.doi.org/10.3390/ijms20163863.

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Although lung surfactant protein B (SP-B) is an essential protein that plays a crucial role in breathing, the details of its structure and mechanism are not well understood. SP-B forms covalent homodimers, and in this work we use all-atom molecular dynamics simulations to study dimeric SP-B’s structure and its behavior in promoting lipid structural transitions. Four initial system configurations were constructed based on current knowledge of SP-B’s structure and mechanism, and the protein maintained a helicity consistent with experiment in all systems. Several SP-B-induced lipid reorganization behaviors were observed, and regions of the protein particularly important for these activities included SP-B’s “central loop” and “hinge” regions. SP-B dimers with one subunit initially positioned in each of two adjacent bilayers appeared to promote close contact between two bilayers. When both subunits were initially positioned in the same bilayer, SP-B induced the formation of a defect in the bilayer, with water penetrating into the centre of the bilayer. Similarly, dimeric SP-B showed a propensity to interact with preformed interpores in the bilayer. SP-B dimers also promoted bilayer thinning and creasing. This work fleshes out the atomistic details of the dimeric SP-B structures and SP-B/lipid interactions that underlie SP-B’s essential functions.

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49

Kazi, Altaf S., Jian-Qin Tao, Sheldon I. Feinstein, Li Zhang, Aron B. Fisher, and Sandra R. Bates. "Role of the PI3-kinase signaling pathway in trafficking of the surfactant protein A receptor P63 (CKAP4) on type II pneumocytes." American Journal of Physiology-Lung Cellular and Molecular Physiology 299, no. 6 (December 2010): L794—L807. http://dx.doi.org/10.1152/ajplung.00372.2009.

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Surfactant protein A (SP-A) plays an important role in the maintenance of lung lipid homeostasis. Previously, an SP-A receptor, P63 (CKAP4), on type II pneumocyte plasma membranes (PM) was identified by chemical cross-linking techniques. An antibody to P63 blocked the specific binding of SP-A to pneumocytes and the ability of SP-A to regulate surfactant secretion. The current report shows that another biological activity of SP-A, the stimulation of surfactant uptake by pneumocytes, is inhibited by P63 antibody. cAMP exposure resulted in enrichment of P63 on the cell surface as shown by stimulation of SP-A binding, enhanced association of labeled P63 antibody with type II cells, and promotion of SP-A-mediated liposome uptake, all of which were inhibited by competing P63 antibody. Incubation of A549 and type II cells with SP-A also increased P63 localization on the PM. The phosphatidylinositol 3-kinase (PI3-kinase) signaling pathway was explored as a mechanism for the transport of this endoplasmic reticulum (ER)-resident protein to the PM. Treatment with LY-294002, an inhibitor of the PI3-kinase pathway, prevented the SP-A-induced PM enrichment of P63. Exposure of pneumocytes to SP-A or cAMP activated Akt (PKB). Blocking either PI3-kinase or Akt altered SP-A-mediated lipid turnover. The data demonstrate an important role for the PI3-kinase-Akt pathway in intracellular transport of P63. The results add to the growing body of evidence that P63 is critical for SP-A receptor-mediated interactions with type II pneumocytes and the resultant regulation of surfactant turnover.

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50

Baoukina, Svetlana, and D. Peter Tieleman. "Simulation Studies on Interactions of Lung Surfactant Protein SP-B with Lipid Monolayers and Vesicles." Biophysical Journal 98, no. 3 (January 2010): 90a. http://dx.doi.org/10.1016/j.bpj.2009.12.507.

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