The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Alan J Waring - One of the best experts on this subject based on the ideXlab platform.
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design of Surfactant protein b peptide mimics based on the saposin fold for synthetic Lung Surfactants
Biomedicine Hub, 2016Co-Authors: Frans J Walther, Larry M. Gordon, Alan J WaringAbstract: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 (SA
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combined effect of synthetic protein mini b and cholesterol on a model Lung Surfactant mixture at the air water interface
Biochimica et Biophysica Acta, 2016Co-Authors: Aishik Chakraborty, Alan J Waring, Prajnaparamita DharAbstract:Abstract The overall goal of this work is to study the combined effects of Mini-B, a 34 residue synthetic analog of the Lung Surfactant protein SP-B, and cholesterol, a neutral lipid, on a model binary lipid mixture containing dipalmitolphosphatidylcholine (DPPC) and palmitoyl-oleoyl-phosphatidylglycerol (POPG), that is often used to mimic the primary phospholipid composition of Lung Surfactants. Using surface pressure vs. mean molecular area isotherms, fluorescence imaging and analysis of lipid domain size distributions; we report on changes in the structure, function and stability of the model lipid-protein films in the presence and absence of varying composition of cholesterol. Our results indicate that at low cholesterol concentrations, Mini-B can prevent cholesterol's tendency to lower the line tension between lipid domain boundaries, while maintaining Mini-B's ability to cause reversible collapse resulting in the formation of surface associated reservoirs. Our results also show that lowering the line tension between domains can adversely impact monolayer folding mechanisms. We propose that small amounts of cholesterol and synthetic protein Mini-B can together achieve the seemingly opposing requirements of efficient LS: fluid enough to flow at the air–water interface, while being rigid enough to oppose irreversible collapse at ultra-low surface tensions.
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effects of the Lung Surfactant protein b construct mini b on lipid bilayer order and topography
European Biophysics Journal, 2012Co-Authors: Dharamaraju Palleboina, Valerie Booth, Alan J Waring, Robert H Notter, Michael R MorrowAbstract:The hydrophobic Lung Surfactant protein, SP-B, is essential for survival. Cycling of Lung volume during respiration requires a surface-active lipid–protein layer at the alveolar air–water interface. SP-B may contribute to Surfactant layer maintenance and renewal by facilitating contact and transfer between the surface layer and bilayer reservoirs of Surfactant material. However, only small effects of SP-B on phospholipid orientational order in model systems have been reported. In this study, N-terminal (SP-B8–25) and C-terminal (SP-B63–78) helices of SP-B, either linked as Mini-B or unlinked but present in equal amounts, were incorporated into either model phospholipid mixtures or into bovine lipid extract Surfactant in the form of vesicle dispersions or mechanically oriented bilayer samples. Deuterium and phosphorus nuclear magnetic resonance (NMR) were used to characterize effects of these peptides on phospholipid chain orientational order, headgroup orientation, and the response of lipid–peptide mixtures to mechanical orientation by mica plates. Only small effects on chain orientational order or headgroup orientation, in either vesicle or mechanically oriented samples, were seen. In mechanically constrained samples, however, Mini-B and its component helices did have specific effects on the propensity of lipid–peptide mixtures to form unoriented bilayer populations which do not exchange with the oriented fraction on the timescale of the NMR experiment. Modification of local bilayer orientation, even in the presence of mechanical constraint, may be relevant to the transfer of material from bilayer reservoirs to a flat surface-active layer, a process that likely requires contact facilitated by the formation of highly curved protrusions.
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orientation and depth of Surfactant protein b c terminal helix in Lung Surfactant bilayers
Biochimica et Biophysica Acta, 2012Co-Authors: Philippe Bertani, Tranchin Yang, Jennifer Rendell, Valerie Booth, Larry M. Gordon, Verica Vidovic, Burkhard Bechinger, Alan J WaringAbstract:Abstract SP-B CTERM is a cationic amphipathic helical peptide and functional fragment composed of residues 63 to 78 of Surfactant protein B (SP-B). Static oriented and magic angle spinning solid state NMR, along with molecular dynamics simulation was used to investigate its structure, orientation, and depth in lipid bilayers of several compositions, namely POPC, DPPC, DPPC/POPC/POPG, and bovine Lung Surfactant extract (BLES). In all lipid environments the peptide was oriented parallel to the membrane surface. While maintaining this approximately planar orientation, SP-B CTERM exhibited a flexible topology controlled by subtle variations in lipid composition. SP-B CTERM -induced lipid realignment and/or conformational changes at the level of the head group were observed using 31 P solid-state NMR spectroscopy. Measurements of the depth of SP-B CTERM indicated the peptide center positions ~8 A more deeply than the phosphate headgroups, a topology that may allow the peptide to promote functional lipid structures without causing micellization upon compression.
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lipid protein interactions alter line tensions and domain size distributions in Lung Surfactant monolayers
Biophysical Journal, 2012Co-Authors: Prajnaparamita Dhar, Alan J Waring, Elizabeth Eck, Jacob N Israelachvili, Dong Woog Lee, Younjin Min, Arun Ramachandran, Joseph A ZasadzinskiAbstract:The size distribution of domains in phase-separated Lung Surfactant monolayers influences monolayer viscoelas- ticity and compressibility which, in turn, influence monolayer collapse and set the compression at which the minimum surface tension is reached. The Surfactant-specific protein SP-B decreases the mean domain size and polydispersity as shown by fluorescence microscopy. From the images, the line tension and dipole density difference are determined by comparing the measured size distributions with a theory derived by minimizing the free energy associated with the domain energy and mixing entropy. We find that SP-B increases the line tension, dipole density difference, and the compressibility modulus at surface pressures up to the squeeze-out pressure. The increase in line tension due to SP-B indicates the protein avoids domain bound- aries due to its solubility in the more fluid regions of the film.
Joseph A Zasadzinski - One of the best experts on this subject based on the ideXlab platform.
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interfacial curvature effects on the monolayer morphology and dynamics of a clinical Lung Surfactant
Proceedings of the National Academy of Sciences of the United States of America, 2018Co-Authors: Amit K Sachan, Joseph A ZasadzinskiAbstract:The morphology of Surfactant monolayers is typically studied on the planar surface of a Langmuir trough, even though most physiological interfaces are curved at the micrometer scale. Here, we show that, as the radius of a clinical Lung Surfactant monolayer-covered bubble decreases to ∼100 µm, the monolayer morphology changes from dispersed circular liquid-condensed (LC) domains in a continuous liquid-expanded (LE) matrix to a continuous LC linear mesh separating discontinuous LE domains. The curvature-associated morphological transition cannot be readily explained by current liquid crystal theories based on isotropic domains. It is likely due to the anisotropic bending energy of the LC phase of the saturated phospholipids that are common to all natural and clinical Lung Surfactants. This continuous LC linear mesh morphology is also present on bilayer vesicles in solution. Surfactant adsorption and the dilatational modulus are also strongly influenced by the changes in morphology induced by interfacial curvature. The changes in morphology and dynamics may have physiological consequences for Lung stability and function as the morphological transition occurs at alveolar dimensions.
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lipid protein interactions alter line tensions and domain size distributions in Lung Surfactant monolayers
Biophysical Journal, 2012Co-Authors: Prajnaparamita Dhar, Alan J Waring, Elizabeth Eck, Jacob N Israelachvili, Dong Woog Lee, Younjin Min, Arun Ramachandran, Joseph A ZasadzinskiAbstract:The size distribution of domains in phase-separated Lung Surfactant monolayers influences monolayer viscoelas- ticity and compressibility which, in turn, influence monolayer collapse and set the compression at which the minimum surface tension is reached. The Surfactant-specific protein SP-B decreases the mean domain size and polydispersity as shown by fluorescence microscopy. From the images, the line tension and dipole density difference are determined by comparing the measured size distributions with a theory derived by minimizing the free energy associated with the domain energy and mixing entropy. We find that SP-B increases the line tension, dipole density difference, and the compressibility modulus at surface pressures up to the squeeze-out pressure. The increase in line tension due to SP-B indicates the protein avoids domain bound- aries due to its solubility in the more fluid regions of the film.
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overcoming rapid inactivation of Lung Surfactant analogies between competitive adsorption and colloid stability
Biochimica et Biophysica Acta, 2010Co-Authors: Joseph A Zasadzinski, Patrick Christopher Stenger, Ian C Shieh, Prajnaparamita DharAbstract:Abstract Lung Surfactant (LS) is a mixture of lipids and proteins that line the alveolar air–liquid interface, lowering the interfacial tension to levels that make breathing possible. In acute respiratory distress syndrome (ARDS), inactivation of LS is believed to play an important role in the development and severity of the disease. This review examines the competitive adsorption of LS and surface-active contaminants, such as serum proteins, present in the alveolar fluids of ARDS patients, and how this competitive adsorption can cause normal amounts of otherwise normal LS to be ineffective in lowering the interfacial tension. LS and serum proteins compete for the air–water interface when both are present in solution either in the alveolar fluids or in a Langmuir trough. Equilibrium favors LS as it has the lower equilibrium surface pressure, but the smaller proteins are kinetically favored over multi-micron LS bilayer aggregates by faster diffusion. If albumin reaches the interface, it creates an energy barrier to subsequent LS adsorption that slows or prevents the adsorption of the necessary amounts of LS required to lower surface tension. This process can be understood in terms of classic colloid stability theory in which an energy barrier to diffusion stabilizes colloidal suspensions against aggregation. This analogy provides qualitative and quantitative predictions regarding the origin of Surfactant inactivation. An important corollary is that any additive that promotes colloid coagulation, such as increased electrolyte concentration, multivalent ions, hydrophilic non-adsorbing polymers such as PEG, dextran, etc. added to LS, or polyelectrolytes such as chitosan, also promotes LS adsorption in the presence of serum proteins and helps reverse Surfactant inactivation. The theory provides quantitative tools to determine the optimal concentration of these additives and suggests that multiple additives may have a synergistic effect. A variety of physical and chemical techniques including isotherms, fluorescence microscopy, electron microscopy and X-ray diffraction show that LS adsorption is enhanced by this mechanism without substantially altering the structure or properties of the LS monolayer.
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more than a monolayer relating Lung Surfactant structure and mechanics to composition
Biophysical Journal, 2004Co-Authors: Coralie Alonso, Heidi E Warriner, Timothy Alig, Joonsung Yoon, Frank Bringezu, Joseph A ZasadzinskiAbstract:Survanta, a clinically used bovine Lung Surfactant extract, in contact with Surfactant in the subphase, shows a coexistence of discrete monolayer islands of solid phase coexisting with continuous multilayer “reservoirs” of fluid phase adjacent to the air-water interface. Exchange between the monolayer, the multilayer reservoir, and the subphase determines Surfactant mechanical properties such as the monolayer collapse pressure and surface viscosity by regulating solid-fluid coexistence. Grazing incidence x-ray diffraction shows that the solid phase domains consist of two-dimensional crystals similar to those formed by mixtures of dipalmitoylphosphatidylcholine and palmitic acid. The condensed domains grow as the surface pressure is increased until they coalesce, trapping protrusions of liquid matrix. At ∼40 mN/m, a plateau exists in the isotherm at which the solid phase fraction increases from ∼60 to 90%, at which the surface viscosity diverges. The viscosity is driven by the percolation of the solid phase domains, which depends on the solid phase area fraction of the monolayer. The high viscosity may lead to high monolayer collapse pressures, help prevent atelectasis, and minimize the flow of Lung Surfactant out of the alveoli due to surface tension gradients.
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nanostructure changes in Lung Surfactant monolayers induced by interactions between palmitoyloleoylphosphatidylglycerol and Surfactant protein b
Langmuir, 2003Co-Authors: Junqi Ding, Ivo Doudevski, Heidi E Warriner, Timothy Alig, Joseph A Zasadzinski, Alan J Waring, Mark A ShermanAbstract:Developing synthetic Lung Surfactants to replace animal extracts requires a fundamental understanding of the roles of the various lipids and proteins in native Lung Surfactant. We used Brewster angle microscopy (BAM), atomic force microscopy (AFM), and Langmuir isotherms to study the influence of palmitoyloleoylphosphatidylglycerol (POPG) in monolayers of dipalmitoylphosphatidylcholine and palmitic acid mixtures with or without dSP-B1-25, a peptide dimer based on the first 25 amino acids of Surfactant protein B (SP-B). At surface pressures between 30 and 40 mN/m, only monolayers containing POPG and dSP-B1-25 showed plateaus in the isotherm similar to those in Survanta, a bovine extract replacement Lung Surfactant that contains native SP-B and SP-C proteins. BAM images show distinct morphological changes in the fluid phase during these plateaus, while AFM images of deposited monolayers show that multilayer structures, which we named “nanosilos”, form in the fluid phase at the plateau. These nanosilos are from 50 to 300 nm in diameter and from 5 to 8 nm in height and are similar to those observed in deposited Survanta monolayers. We propose that POPG and SP-B interact to stabilize the monolayer composition by trapping POPG in three-dimensional surface-associated aggregates at high surface pressures, preventing the irreversible loss of POPG and SP-B to the subphase.
Hans-joachim Galla - One of the best experts on this subject based on the ideXlab platform.
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size influences the effect of hydrophobic nanoparticles on Lung Surfactant model systems
Biophysical Journal, 2014Co-Authors: Mridula Dwivedi, Rakesh Kumar Harishchandra, Olga Koshkina, Michael Maskos, Hans-joachim GallaAbstract:The alveolar Lung Surfactant (LS) is a complex lipid protein mixture that forms an interfacial monolayer reducing the surface tension to near zero values and thus preventing the Lungs from collapse. Due to the expanding field of nanotechnology and the corresponding unavoidable exposure of human beings from the air, it is crucial to study the potential effects of nanoparticles (NPs) on the structural organization of the Lung Surfactant system. In the present study, we investigated both, the domain structure in pure DPPC monolayers as well as in Lung Surfactant model systems. In the pure lipid system we found that two different sized hydrophobic polymeric nanoparticles with diameter of ∼12 nm and ∼136 nm have contrasting effect on the functional and structural behavior. The small nanoparticles inserted into fluid domains at the LE-LC phase transition are not visibly disturbing the phase transition but disrupting the domain morphology of the LE phase. The large nanoparticles led to an expanded isotherm and to a significant decrease in the line tension and thus to a drastic disruption of the domain structures at a much lower number of nanoparticles with respect to the lipid. The surface activity of the model LS films again showed drastic variations due to presence of different sized NPs illustrated by the film balance isotherms and the atomic force microscopy. AFM revealed laterally profuse multilayer protrusion formation on compression but only in the presence of 136 nm sized nanoparticles. Moreover we investigated the vesicle insertion process into a preformed monolayer. A severe inhibition was observed only in the presence of ∼136 nm NPs compared to minor effects in the presence of ∼12 nm NPs. Our study clearly shows that the size of the nanoparticles made of the same material determines the interaction with biological membranes.
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nanoparticle interaction with model Lung Surfactant monolayers
Journal of the Royal Society Interface, 2010Co-Authors: Rakesh Kumar Harishchandra, Mohammed Saleem, Hans-joachim GallaAbstract:One of the most important functions of the Lung Surfactant monolayer is to form the first line of defence against inhaled aerosols such as nanoparticles (NPs), which remains largely unexplored. We report here, for the first time, the interaction of polyorganosiloxane NPs (AmorSil20: 22 nm in diameter) with lipid monolayers characteristic of alveolar Surfactant. To enable a better understanding, the current knowledge about an established model surface film that mimics the surface properties of the Lung is reviewed and major results originating from our group are summarized. The pure lipid components dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylglycerol have been used to study the biophysical behaviour of their monolayer films spread at the air–water interface in the presence of NPs. Film balance measurements combined with video-enhanced fluorescence microscopy have been used to investigate the formation of domain structures and the changes in the surface pattern induced by NPs. We are able to show that NPs are incorporated into lipid monolayers with a clear preference for defect structures at the fluid–crystalline interface leading to a considerable monolayer expansion and fluidization. NPs remain at the air–water interface probably by coating themselves with lipids in a self-assembly process, thereby exhibiting hydrophobic surface properties. We also show that the domain structure in lipid layers containing Surfactant protein C, which is potentially responsible for the proper functioning of Surfactant material, is considerably affected by NPs.
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solubility versus electrostatics what determines lipid protein interaction in Lung Surfactant
Biophysical Journal, 2007Co-Authors: Michael Seifert, Daniel Breitenstein, U Klenz, Michaela C Meyer, Hans-joachim GallaAbstract: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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multilayer structures in lipid monolayer films containing Surfactant protein c effects of cholesterol and pope
Biophysical Journal, 2005Co-Authors: Stefan Malcharek, Andreas Hinz, Lutz Hilterhaus, Hans-joachim GallaAbstract:The influence of cholesterol and POPE on Lung Surfactant model systems consisting of DPPC/DPPG (80:20) and DPPC/DPPG/Surfactant protein C (80:20:0.4) has been investigated. Cholesterol leads to a condensation of the monolayers, whereas the isotherms of model Lung Surfactant films containing POPE exhibit a slight expansion combined with an increased compressibility at medium surface pressure (10-30 mN/m). An increasing amount of liquid-expanded domains can be visualized by means of fluorescence light microscopy in Lung Surfactant monolayers after addition of either cholesterol or POPE. At surface pressures of 50 mN/m, protrusions are formed which differ in size and shape as a function of the content of cholesterol or POPE, but only if SP-C is present. Low amounts of cholesterol (10 mol %) lead to an increasing number of protrusions, which also grow in size. This is interpreted as a stabilizing effect of cholesterol on bilayers formed underneath the monolayer. Extreme amounts of cholesterol (30 mol %), however, cause an increased monolayer rigidity, thus preventing reversible multilayer formation. In contrast, POPE, as a nonbilayer lipid thought to stabilize the edges of protrusions, leads to more narrow protrusions. The lateral extension of the protrusions is thereby more influenced than their height.
Kenneth B. M. Reid - One of the best experts on this subject based on the ideXlab platform.
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major house dust mite allergens dermatophagoides pteronyssinus 1 and dermatophagoides farinae 1 degrade and inactivate Lung Surfactant proteins a and d
Journal of Biological Chemistry, 2007Co-Authors: Farouk Shakib, Kenneth B. M. Reid, Howard ClarkAbstract:Lung Surfactant proteins (SP) A and D are calcium-dependent carbohydrate-binding proteins. In addition to playing multiple roles in innate immune defense such as bacterial aggregation and modulation of leukocyte function, SP-A and SP-D have also been implicated in the allergic response. They interact with a wide range of inhaled allergens, competing with their binding to cell-sequestered IgE resulting in inhibition of mast cell degranulation, and exogenous administration of SP-A and SP-D diminishes allergic hypersensitivity in vivo. House dust mite allergens are a major cause of allergic asthma in the western world, and here we confirm the interaction of SP-A and SP-D with two major mite allergens, Dermatophagoides pteronyssinus 1 and Dermatophagoides farinae 1, and show that the cysteine protease activity of these allergens results in the degradation of SP-A and SP-D under physiological conditions, with multiple sites of cleavage. A recombinant fragment of SP-D that is effective in diminishing allergic hypersensitivity in mouse models of dust mite allergy was more susceptible to degradation than the native full-length protein. Degradation was enhanced in the absence of calcium, with different sites of cleavage, indicating that the calcium associated with SP-A and SP-D influences accessibility to the allergens. Degradation of SP-A and SP-D was associated with diminished binding to carbohydrates and to D. pteronyssinus 1 itself and diminished capacity to agglutinate bacteria. Thus, the degradation and consequent inactivation of SP-A and SP-D may be a novel mechanism to account for the potent allergenicity of these common dust mite allergens.
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Lung Surfactant proteins a and d can inhibit specific ige binding to the allergens of aspergillus fumigatus and block allergen induced histamine release from human basophils
Clinical and Experimental Immunology, 2007Co-Authors: Taruna Madan, Uday Kishore, Jiu Yao Wang, Peter Strong, Ashok Shah, Paul Eggleton, S S Aggrawal, P U Sarma, Kenneth B. M. ReidAbstract:Aspergillus fumigatus is an opportunistic fungal pathogen which, in the immunocompetent host, causes allergic disorders such as allergic rhinitis, allergic sinusitis, hypersensitivity pneumonitis, and allergic bronchopulmonary Aspergillosis (ABPA). In the present study, the interaction of 3-week culture filtrate (3wcf) allergens and various purified glycosylated and non-glycosylated allergens of A. fumigatus with Lung Surfactant proteins, SP-A and SP-D, was investigated. Purified SP-A and SP-D, isolated from human bronchoalveolar lavage fluid, bound to the 3wcf allergens and purified allergens, gp55 and gp45, in a carbohydrate-specific and calcium-dependent manner. Both SP-A and SP-D did not bind to deglycosylated allergens, suggesting that the ability of SP-A and SP-D to bind certain allergens is mediated through their carbohydrate recognition domains, interacting with the carbohydrate residues on the allergen. Both SP-A and SP-D could inhibit the ability of allergen-specific IgE from Aspergillosis patients to bind these allergens, suggesting that SP-A and SP-D may be involved in the modulation of allergic sensitization and/or development of allergic reactions. The view that SP-A and SP-D play a protective role against airborne allergens is further supported by the demonstration of their ability to inhibit A. fumigatus allergen-induced histamine release from allergic patients' basophils.
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structures and functions of mammalian collectins
Results and problems in cell differentiation, 2001Co-Authors: Uday Kishore, Kenneth B. M. ReidAbstract:Protein-carbohydrate interactions serve multiple functions in the immune system. Many animal lectins (sugar binding proteins) mediate both pathogen recognition and cell-pathogen interactions using structurally related calcium-dependent carbohydrate recognition domains (C-type CRDs). The collectins are a group of mammalian lectins containing collagen regions. They include mannose-binding lectin (MBL), Lung Surfactant protein A (SP-A), Lung Surfactant protein D (SP-D), bovine conglutinin (BC), and collectin-43 (CL-43). Pathogen recognition by these collectins is mediated by binding of terminal monosaccharide residues characteristic of bacterial and fungal cell surfaces. The broad selectivity of the monosaccharide binding site and the geometrical arrangement of the multiple CRDs in the intact collectins explain the ability of these proteins to bind tightly to arrays of carbohydrate structures normally found on the surfaces of the micro-organisms and thus mediate discrimination between self and non-self.
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crystal structure of the trimeric α helical coiled coil and the three lectin domains of human Lung Surfactant protein d
Structure, 1999Co-Authors: Kjell Hakansson, Hansjurgen Hoppe, Kenneth B. M. ReidAbstract:Abstract Background: Human Lung Surfactant protein D (hSP-D) belongs to the collectin family of C-type lectins and participates in the innate immune surveillance against microorganisms in the Lung through recognition of carbohydrate ligands present on the surface of pathogens. The involvement of this protein in innate immunity and the allergic response make it the subject of much interest. Results: We have determined the crystal structure of a trimeric fragment of hSP-D at 2.3 A resolution. The structure comprises an α-helical coiled-coil and three carbohydrate-recognition domains (CRDs). An interesting deviation from symmetry was found in the projection of a single tyrosine sidechain into the centre of the coiled-coil; the asymmetry of this residue influences the orientation of one of the adjacent CRDs. The cleft between the three CRDs presents a large positively charged surface. Conclusions: The fold of the CRD of hSP-D is similar to that of the mannan-binding protein (MBP), but its orientation relative to the α-helical coiled-coil region differs somewhat to that seen in the MBP structure. The novel central packing of the tyrosine sidechain within the coiled-coil and the resulting asymmetric orientation of the CRDs has unexpected functional implications. The positively charged surface might facilitate binding to negatively charged structures, such as lipopolysaccharides.
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deficient hydrophilic Lung Surfactant proteins a and d with normal Surfactant phospholipid molecular species in cystic fibrosis
American Journal of Respiratory Cell and Molecular Biology, 1999Co-Authors: Anthony D Postle, Kenneth B. M. Reid, Ann Mander, Jiu Yao Wang, Sarah Wright, Maria Moustaki, J O WarnerAbstract:Chronic bacterial colonization of the Lungs, with an excessive inflammatory response, is the major cause of morbidity and mortality in cystic fibrosis. Lung Surfactant exhibits a spectrum of potential immunomodulatory properties: phospholipid components inhibit cellular inflammatory responses, whereas the hydrophilic Surfactant proteins A (SP-A) and D (SP-D) are integral components of the innate host defense response of the Lungs against bacterial infection. Consequently, alteration to the relative proportions of Lung Surfactant components may alter the susceptibility of the Lungs to bacterial colonization. In this study, bronchoalveolar lavage (BAL) samples were collected at diagnostic fiberoptic bronchoscopy from 11 control children, 13 children with cystic fibrosis, and 11 children with acute Lung infection. Electrospray ionization mass spectrometry analysis demonstrated negligible changes to the molecular species or total BAL concentrations of phosphatidylcholine, phosphatidylglycerol, or phosphatidyl...
Uffe Holmskov - One of the best experts on this subject based on the ideXlab platform.
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the sars coronavirus spike glycoprotein is selectively recognized by Lung Surfactant protein d and activates macrophages
Immunobiology, 2007Co-Authors: Rikke Lethlarsen, Fei Zhong, Vincent T K Chow, Uffe HolmskovAbstract:The severe acute respiratory syndrome coronavirus (SARS-CoV) infects host cells with its surface glycosylated spike-protein (S-protein). Here we expressed the SARS-CoV S-protein to investigate its interactions with innate immune mechanisms in the Lung. The purified S-protein was detected as a 210 kDa glycosylated protein. It was not secreted in the presence of tunicamycin and was detected as a 130 kDa protein in the cell lysate. The purified S-protein bound to Vero but not 293T cells and was itself recognized by Lung Surfactant protein D (SP-D), a collectin found in the Lung alveoli. The binding required Ca(2+) and was inhibited by maltose. The serum collectin, mannan-binding lectin (MBL), exhibited no detectable binding to the purified S-protein. S-protein binds and activates macrophages but not dendritic cells (DCs). It suggests that SARS-CoV interacts with innate immune mechanisms in the Lung through its S-protein and regulates pulmonary inflammation.
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expression and localization of Lung Surfactant protein a in human tissues
American Journal of Respiratory Cell and Molecular Biology, 2003Co-Authors: Jens Madsen, Ida Tornoe, Ole Haagen Nielsen, Claus Koch, Wolfram Steinhilber, Uffe HolmskovAbstract:Lung Surfactant protein A (SP-A) is a collectin produced by alveolar type II cells and Clara cells. It binds to carbohydrate structures on microorganisms, initiating effector mechanisms of innate immunity and modulating the inflammatory response in the Lung. Reverse transcriptase-polymerase chain reaction was performed on a panel of RNAs from human tissues for SP-A mRNA expression. The Lung was the main site of synthesis, but transcripts were readily amplified from the trachea, prostate, pancreas, and thymus. Weak expression was observed in the colon and salivary gland. SP-A sequences derived from Lung and thymus mRNA revealed the presence of both SP-A1 and SP-A2, whereas only SP-A2 expression was found in the trachea and prostate. Monoclonal antibodies were raised against SP-A and characterized. One of these (HYB 238-4) reacted in Western blotting with both reduced and unreduced SP-A, with N-deglycosylated and collagenase-treated SP-A, and with both recombinant SP-A1 and SP-A2. This antibody was used to demonstrate SP-A in immunohistochemistry of human tissues. Strong SP-A immunoreactivity was seen in alveolar type-II cells, Clara cells, and on and within alveolar macrophages, but no extrapulmonary SP-A immunoreactivity was observed. In contrast to Lung Surfactant protein D (SP-D), which is generally expressed on mucosal surfaces, SP-A seems to be restricted to the respiratory system.
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heritability estimates for the constitutional levels of the collectins mannan binding lectin and Lung Surfactant protein d a study of unselected like sexed mono and dizygotic twins at the age of 6 9 years
Immunology, 2002Co-Authors: Steffen Husby, Anne Maria Herskind, Jens Christian Jensenius, Uffe HolmskovAbstract:The collectins mannan-binding lectin (MBL) and Lung Surfactant protein D (SP-D) play a significant role in innate immunity. Structural as wells as promoter variants are known for MBL and different alleles correlate with low MBL concentrations in serum and predispose to infectious diseases. Structural variants are also known for SP-D but these have not been linked to disease states. The aim of the present study was to provide heritability estimates for the constitutional levels of MBL and SP-D in children. A population of 26 monozygotic (MZ) and 36 dizygotic (DZ) like-sexed twin pairs aged 6–9 years was studied. Intraclass correlations were significantly higher in MZ than in DZ twins, indicating substantial genetic influence on both MBL and SP-D levels. Biometric model fitting showed that the estimated heritability was 0·96 (95% CI 0·92–0·97) for MBL with the presence of non-additive genetic factors and non-shared environmental factors and 0·91 (95% CI 0·83–0·95) for SP-D with additive genetic and non-shared environmental factors. The data indicate quantitatively very strong genetic dependence for the serum levels of both MBL and SP-D.
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localization of Lung Surfactant protein d on mucosal surfaces in human tissues
Journal of Immunology, 2000Co-Authors: Jens Madsen, Ida Tornoe, Claus Koch, Anette Kliem, Karsten Skjodt, Uffe HolmskovAbstract:Lung Surfactant protein-D (SP-D), a collectin mainly produced by alveolar type II cells, initiates the effector mechanisms of innate immunity on binding to microbial carbohydrates. A panel of mRNAs from human tissues was screened for SP-D mRNA by RT-PCR. The Lung was the main site of synthesis, but transcripts were readily amplified from trachea, brain, testis, salivary gland, heart, prostate gland, kidney, and pancreas. Minor sites of synthesis were uterus, small intestine, placenta, mammary gland, and stomach. The sequence of SP-D derived from parotid gland mRNA was identical with that of pulmonary SP-D. mAbs were raised against SP-D, and one was used to locate SP-D in cells and tissues by immunohistochemistry. SP-D immunoreactivity was found in alveolar type II cells, Clara cells, on and within alveolar macrophages, in epithelial cells of large and small ducts of the parotid gland, sweat glands, and lachrymal glands, in epithelial cells of the gall bladder and intrahepatic bile ducts, and in exocrine pancreatic ducts. SP-D was also present in epithelial cells of the skin, esophagus, small intestine, and urinary tract, as well as in the collecting ducts of the kidney. SP-D is generally present on mucosal surfaces and not restricted to a subset of cells in the Lung. The localization and functions of SP-D indicate that this collectin is the counterpart in the innate immune system of IgA in the adaptive immune system.
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isolation and characterization of a new member of the scavenger receptor superfamily glycoprotein 340 gp 340 as a Lung Surfactant protein d binding molecule
Journal of Biological Chemistry, 1997Co-Authors: Uffe Holmskov, Ida Tornoe, Claus Koch, Peter R Lawson, Borge Teisner, Antony C Willis, Cliff Morgan, Kenneth B. M. ReidAbstract:We have purified a previously unknown glycoprotein (designated gp-340) from human bronchioalveolar Lung washings from a patient with alveolar proteinosis. gp-340 was identified by its calcium-dependent binding to Lung Surfactant protein D (SP-D) and by its molecular mass of 340 kDa in the reduced state on SDS-polyacrylamide gel electrophoresis (PAGE). gp-340 was purified from the 10,000 × g pellet of the lavage fluid by ion-exchange and gel permeation chromatography. On SDS-PAGE, gp-340 showed an apparent molecular mass of 290 kDa in the unreduced state. On gel chromatography under non-dissociating conditions, the apparent molecular mass of gp-340 was >1000 kDa. The presence ofN-linked glycosylation was shown by digestion withN-glycosidase F, which reduced the apparent molecular mass of gp-340 under reducing condition to about 300 kDa. Partial amino acid sequence data showed the presence of scavenger-receptor type domains. Monoclonal and polyclonal antibodies were raised against gp-340, and their specificities were confirmed by Western blotting. The antibodies were used for immunohistochemical localization of gp-340 in the Lung, where it was found on the surface of and within alveolar macrophages. Direct binding between gp-340 and SP-D took place at physiological ionic strength, required the presence of calcium, and was not inhibited by maltose. The binding between SP-D and mannan also required the presence of calcium, but this interaction was completely inhibited by maltose. The same binding pattern was seen between gp-340 and recombinant human SP-D composed of the trimeric neck region and three carbohydrate recognition domains. These findings indicate that the binding between gp-340 and SP-D is a protein-protein interaction rather than a lectin-carbohydrate interaction and that the binding to gp-340 takes place via the carbohydrate recognition domain of SP-D. We conclude that gp-340 is a new member of the scavenger-receptor superfamily and likely to be a truncated form of a receptor for SP-D.
