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Walther FJ, Waring AJ. Structure and Function of Canine SP-C Mimic Proteins in Synthetic Surfactant Lipid Dispersions. Biomedicines 2024; 12:163. [PMID: 38255268 PMCID: PMC10813813 DOI: 10.3390/biomedicines12010163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 01/03/2024] [Accepted: 01/08/2024] [Indexed: 01/24/2024] Open
Abstract
Lung surfactant is a mixture of lipids and proteins and is essential for air breathing in mammals. The hydrophobic surfactant proteins B and C (SP-B and SP-C) assist in reducing surface tension in the lung alveoli by organizing the surfactant lipids. SP-B deficiency is life-threatening, and a lack of SP-C can lead to progressive interstitial lung disease. B-YL (41 amino acids) is a highly surface-active, sulfur-free peptide mimic of SP-B (79 amino acids) in which the four cysteine residues are replaced by tyrosine. Mammalian SP-C (35 amino acids) contains two cysteine-linked palmitoyl groups at positions 5 and 6 in the N-terminal region that override the β-sheet propensities of the native sequence. Canine SP-C (34 amino acids) is exceptional because it has only one palmitoylated cysteine residue at position 4 and a phenylalanine at position 5. We developed canine SP-C constructs in which the palmitoylated cysteine residue at position 4 is replaced by phenylalanine (SP-Cff) or serine (SP-Csf) and a glutamic acid-lysine ion-lock was placed at sequence positions 20-24 of the hydrophobic helical domain to enhance its alpha helical propensity. AI modeling, molecular dynamics, circular dichroism spectroscopy, Fourier Transform InfraRed spectroscopy, and electron spin resonance studies showed that the secondary structure of canine SP-Cff ion-lock peptide was like that of native SP-C, suggesting that substitution of phenylalanine for cysteine has no apparent effect on the secondary structure of the peptide. Captive bubble surfactometry demonstrated higher surface activity for canine SP-Cff ion-lock peptide in combination with B-YL in surfactant lipids than with canine SP-Csf ion-lock peptide. These studies demonstrate the potential of canine SP-Cff ion-lock peptide to enhance the functionality of the SP-B peptide mimic B-YL in synthetic surfactant lipids.
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Affiliation(s)
- Frans J. Walther
- Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, CA 90502, USA
- Department of Pediatrics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Alan J. Waring
- Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, CA 90502, USA
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
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2
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Morán‐Lalangui M, Coutinho A, Prieto M, Fedorov A, Pérez‐Gil J, Loura LMS, García‐Álvarez B. Exploring protein-protein interactions and oligomerization state of pulmonary surfactant protein C (SP-C) through FRET and fluorescence self-quenching. Protein Sci 2024; 33:e4835. [PMID: 37984447 PMCID: PMC10731621 DOI: 10.1002/pro.4835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 11/03/2023] [Accepted: 11/06/2023] [Indexed: 11/22/2023]
Abstract
Pulmonary surfactant (PS) is a lipid-protein complex that forms films reducing surface tension at the alveolar air-liquid interface. Surfactant protein C (SP-C) plays a key role in rearranging the lipids at the PS surface layers during breathing. The N-terminal segment of SP-C, a lipopeptide of 35 amino acids, contains two palmitoylated cysteines, which affect the stability and structure of the molecule. The C-terminal region comprises a transmembrane α-helix that contains a ALLMG motif, supposedly analogous to a well-studied dimerization motif in glycophorin A. Previous studies have demonstrated the potential interaction between SP-C molecules using approaches such as Bimolecular Complementation assays or computational simulations. In this work, the oligomerization state of SP-C in membrane systems has been studied using fluorescence spectroscopy techniques. We have performed self-quenching and FRET assays to analyze dimerization of native palmitoylated SP-C and a non-palmitoylated recombinant version of SP-C (rSP-C) using fluorescently labeled versions of either protein reconstituted in different lipid systems mimicking pulmonary surfactant environments. Our results reveal that doubly palmitoylated native SP-C remains primarily monomeric. In contrast, non-palmitoylated recombinant SP-C exhibits dimerization, potentiated at high concentrations, especially in membranes with lipid phase separation. Therefore, palmitoylation could play a crucial role in stabilizing the monomeric α-helical conformation of SP-C. Depalmitoylation, high protein densities as a consequence of membrane compartmentalization, and other factors may all lead to the formation of protein dimers and higher-order oligomers, which could have functional implications under certain pathological conditions and contribute to membrane transformations associated with surfactant metabolism and alveolar homeostasis.
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Affiliation(s)
- Mishelle Morán‐Lalangui
- Department of Biochemistry and Molecular BiologyFaculty of Biology, Complutense UniversityMadridSpain
- Research Institute “Hospital 12 de Octubre (imas12)”MadridSpain
| | - Ana Coutinho
- iBB Institute for Bioengineering and Bioscience, IST, Universidade de LisboaLisbonPortugal
- Associate Lab i4HB, Institute for Health and Bioeconomy at IST, Universidade de LisboaLisbonPortugal
- Department of Chemistry and BiochemistryFaculty of Sciences, University of LisbonLisbonPortugal
| | - Manuel Prieto
- iBB Institute for Bioengineering and Bioscience, IST, Universidade de LisboaLisbonPortugal
- Associate Lab i4HB, Institute for Health and Bioeconomy at IST, Universidade de LisboaLisbonPortugal
| | - Alexander Fedorov
- iBB Institute for Bioengineering and Bioscience, IST, Universidade de LisboaLisbonPortugal
- Associate Lab i4HB, Institute for Health and Bioeconomy at IST, Universidade de LisboaLisbonPortugal
| | - Jesús Pérez‐Gil
- Department of Biochemistry and Molecular BiologyFaculty of Biology, Complutense UniversityMadridSpain
- Research Institute “Hospital 12 de Octubre (imas12)”MadridSpain
| | - Luís M. S. Loura
- Department of Chemistry, Coimbra Chemistry Centre, Institute of Molecular Sciences (CQC‐IMS)University of CoimbraCoimbraPortugal
- CNC Centre for Neuroscience and Cell Biology, University of CoimbraCoimbraPortugal
- Faculty of PharmacyUniversity of CoimbraCoimbraPortugal
| | - Begoña García‐Álvarez
- Department of Biochemistry and Molecular BiologyFaculty of Biology, Complutense UniversityMadridSpain
- Research Institute “Hospital 12 de Octubre (imas12)”MadridSpain
- Department of Biochemistry and Molecular BiologyFaculty of Chemistry, Complutense UniversityMadridSpain
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3
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Abstract
Pulmonary surfactant is a critical component of lung function in healthy individuals. It functions in part by lowering surface tension in the alveoli, thereby allowing for breathing with minimal effort. The prevailing thinking is that low surface tension is attained by a compression-driven squeeze-out of unsaturated phospholipids during exhalation, forming a film enriched in saturated phospholipids that achieves surface tensions close to zero. A thorough review of past and recent literature suggests that the compression-driven squeeze-out mechanism may be erroneous. Here, we posit that a surfactant film enriched in saturated lipids is formed shortly after birth by an adsorption-driven sorting process and that its composition does not change during normal breathing. We provide biophysical evidence for the rapid formation of an enriched film at high surfactant concentrations, facilitated by adsorption structures containing hydrophobic surfactant proteins. We examine biophysical evidence for and against the compression-driven squeeze-out mechanism and propose a new model for surfactant function. The proposed model is tested against existing physiological and pathophysiological evidence in neonatal and adult lungs, leading to ideas for biophysical research, that should be addressed to establish the physiological relevance of this new perspective on the function of the mighty thin film that surfactant provides.
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Affiliation(s)
- Fred Possmayer
- Department of Biochemistry, Western University, London, Ontario N6A 3K7, Canada
- Department of Obstetrics/Gynaecology, Western University, London, Ontario N6A 3K7, Canada
| | - Yi Y Zuo
- Department of Mechanical Engineering, University of Hawaii at Manon, Honolulu, Hawaii 96822, United States
- Department of Pediatrics, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii 96826, United States
| | - Ruud A W Veldhuizen
- Department of Physiology & Pharmacology, Western University, London, Ontario N6A 5C1, Canada
- Department of Medicine, Western University, London, Ontario N6A 3K7, Canada
- Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
| | - Nils O Petersen
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
- Department of Chemistry, Western University, London, Ontario N6A 5B7, Canada
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4
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A comprehensive mini-review on amyloidogenesis of different SARS-CoV-2 proteins and its effect on amyloid formation in various host proteins. 3 Biotech 2022; 12:322. [PMID: 36254263 PMCID: PMC9558030 DOI: 10.1007/s13205-022-03390-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Accepted: 09/30/2022] [Indexed: 11/21/2022] Open
Abstract
Amyloidogenesis is the inherent ability of proteins to change their conformation from native state to cross β-sheet rich fibrillar structures called amyloids which result in a wide range of diseases like Parkinson's disease, Alzheimer’s disease, Finnish familial amyloidosis, ATTR amyloidosis, British and Danish dementia, etc. COVID-19, on the other hand is seen to have many similarities in symptoms with other amyloidogenic diseases and the overlap of these morbidities and symptoms led to the proposition whether SARS-CoV-2 proteins are undergoing amyloidogenesis and whether it is resulting in or aggravating amyloidogenesis of any human host protein. Thus the SARS-CoV-2 proteins in infected cells, i.e., Spike (S) protein, Nucleocapsid (N) protein, and Envelope (E) protein were tested via different machinery and amyloidogenesis in them were proven. In this review, we will analyze the pathway of amyloid formation in S-protein, N-protein, E-protein along with the effect that SARS-CoV-2 is creating on various host proteins leading to the unexpected onset of many morbidities like COVID-induced Acute Respiratory Distress Syndrome (ARDS), Parkinsonism in young COVID patients, formation of fibrin microthrombi in heart, etc., and their future implications.
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5
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Extraction methods significantly impact pea protein composition, structure and gelling properties. Food Hydrocoll 2021. [DOI: 10.1016/j.foodhyd.2021.106678] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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6
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Sinha N, Thakur AK. Likelihood of amyloid formation in COVID-19-induced ARDS. Trends Microbiol 2021; 29:967-969. [PMID: 33795156 PMCID: PMC8007089 DOI: 10.1016/j.tim.2021.03.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 03/11/2021] [Accepted: 03/12/2021] [Indexed: 12/02/2022]
Abstract
Severe coronavirus disease 2019 (COVID-19) infection leads to multifactorial acute respiratory distress syndrome (ARDS), with little therapeutic success. The pathophysiology associated with ARDS or post-ARDS is not yet well understood. We hypothesize that amyloid formation occurring due to protein homeostasis disruption can be one of the complications associated with COVID-19-induced-ARDS.
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Affiliation(s)
- Nabodita Sinha
- Department of Biological Sciences and Bioengineering, Indian Institute of Technology Kanpur, UP 208016, India
| | - Ashwani K Thakur
- Department of Biological Sciences and Bioengineering, Indian Institute of Technology Kanpur, UP 208016, India.
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7
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Ghosh DK, Ranjan A. The metastable states of proteins. Protein Sci 2020; 29:1559-1568. [PMID: 32223005 PMCID: PMC7314396 DOI: 10.1002/pro.3859] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 03/23/2020] [Accepted: 03/24/2020] [Indexed: 12/26/2022]
Abstract
The intriguing process of protein folding comprises discrete steps that stabilize the protein molecules in different conformations. The metastable state of protein is represented by specific conformational characteristics, which place the protein in a local free energy minimum state of the energy landscape. The native-to-metastable structural transitions are governed by transient or long-lived thermodynamic and kinetic fluctuations of the intrinsic interactions of the protein molecules. Depiction of the structural and functional properties of metastable proteins is not only required to understand the complexity of folding patterns but also to comprehend the mechanisms of anomalous aggregation of different proteins. In this article, we review the properties of metastable proteins in context of their stability and capability of undergoing atypical aggregation in physiological conditions.
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Affiliation(s)
- Debasish Kumar Ghosh
- Computational and Functional Genomics Group, Centre for DNA Fingerprinting and DiagnosticsUppal, HyderabadTelanganaIndia
| | - Akash Ranjan
- Computational and Functional Genomics Group, Centre for DNA Fingerprinting and DiagnosticsUppal, HyderabadTelanganaIndia
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8
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Johansson J, Curstedt T. Synthetic surfactants with SP-B and SP-C analogues to enable worldwide treatment of neonatal respiratory distress syndrome and other lung diseases. J Intern Med 2019; 285:165-186. [PMID: 30357986 DOI: 10.1111/joim.12845] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Treatment of neonatal respiratory distress syndrome (RDS) using animal-derived lung surfactant preparations has reduced the mortality of handling premature infants with RDS to a 50th of that in the 1960s. The supply of animal-derived lung surfactants is limited and only a part of the preterm babies is treated. Thus, there is a need to develop well-defined synthetic replicas based on key components of natural surfactant. A synthetic product that equals natural-derived surfactants would enable cost-efficient production and could also facilitate the development of the treatments of other lung diseases than neonatal RDS. Recently the first synthetic surfactant that contains analogues of the two hydrophobic surfactant proteins B (SP-B) and SP-C entered clinical trials for the treatment of neonatal RDS. The development of functional synthetic analogues of SP-B and SP-C, however, is considerably more challenging than anticipated 30 years ago when the first structural information of the native proteins became available. For SP-B, a complex three-dimensional dimeric structure stabilized by several disulphides has necessitated the design of miniaturized analogues. The main challenge for SP-C has been the pronounced amyloid aggregation propensity of its transmembrane region. The development of a functional non-aggregating SP-C analogue that can be produced synthetically was achieved by designing the amyloidogenic native sequence so that it spontaneously forms a stable transmembrane α-helix.
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Affiliation(s)
- J Johansson
- Department of Neurobiology, Care Sciences and Society, Section for Neurogeriatrics, Karolinska Institutet, Huddinge, Sweden
| | - T Curstedt
- Laboratory for Surfactant Research, Department of Molecular Medicine and Surgery, Karolinska Institutet at Karolinska University Hospital, Stockholm, Sweden
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9
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Yang J, Huang J, Zeng H, Chen L. Surface pressure affects B-hordein network formation at the air–water interface in relation to gastric digestibility. Colloids Surf B Biointerfaces 2015; 135:784-792. [DOI: 10.1016/j.colsurfb.2015.08.035] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 07/28/2015] [Accepted: 08/20/2015] [Indexed: 01/12/2023]
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10
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Carvalheda CA, Campos SRR, Baptista AM. The Effect of Membrane Environment on Surfactant Protein C Stability Studied by Constant-pH Molecular Dynamics. J Chem Inf Model 2015; 55:2206-17. [PMID: 26397014 DOI: 10.1021/acs.jcim.5b00076] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Pulmonary surfactant protein C (SP-C) is a small peptide with two covalently linked fatty acyl chains that plays a crucial role in the formation and stabilization of the pulmonary surfactant reservoirs during the compression and expansion steps of the respiratory cycle. Although its function is known to be tightly related to its highly hydrophobic character and key interactions maintained with specific lipid components, much is left to understand about its molecular mechanism of action. Also, although it adopts a mainly helical structure while associated with the membrane, factors as pH variation and deacylation have been shown to affect its stability and function. In this work, the conformational behavior of both the acylated and deacylated SP-C isoforms was studied in a DPPC bilayer under different pH conditions using constant-pH molecular dynamics simulations. Our findings show that both protein isoforms are remarkably stable over the studied pH range, even though the acylated isoform exhibits a labile helix-turn-helix motif rarely observed in the other isoform. We estimate similar tilt angles for the two isoforms over the studied pH range, with a generally higher degree of internalization of the basic N-terminal residues in the deacylated case, and observe and discuss some protonation-conformation coupling effects. Both isoforms establish contacts with the surrounding lipid molecules (preferentially with the sn-2 ester bonds) and have a local effect on the conformational behavior of the surrounding lipid molecules, the latter being more pronounced for acylated SP-C.
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Affiliation(s)
- Catarina A Carvalheda
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa , Av. da República, 2780-157 Oeiras, Portugal
| | - Sara R R Campos
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa , Av. da República, 2780-157 Oeiras, Portugal
| | - António M Baptista
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa , Av. da República, 2780-157 Oeiras, Portugal
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11
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Sáenz A, Presto J, Lara P, Akinyi-Oloo L, García-Fojeda B, Nilsson I, Johansson J, Casals C. Folding and Intramembraneous BRICHOS Binding of the Prosurfactant Protein C Transmembrane Segment. J Biol Chem 2015; 290:17628-41. [PMID: 26041777 DOI: 10.1074/jbc.m114.630343] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2014] [Indexed: 12/19/2022] Open
Abstract
Surfactant protein C (SP-C) is a novel amyloid protein found in the lung tissue of patients suffering from interstitial lung disease (ILD) due to mutations in the gene of the precursor protein pro-SP-C. SP-C is a small α-helical hydrophobic protein with an unusually high content of valine residues. SP-C is prone to convert into β-sheet aggregates, forming amyloid fibrils. Nature's way of solving this folding problem is to include a BRICHOS domain in pro-SP-C, which functions as a chaperone for SP-C during biosynthesis. Mutations in the pro-SP-C BRICHOS domain or linker region lead to amyloid formation of the SP-C protein and ILD. In this study, we used an in vitro transcription/translation system to study translocon-mediated folding of the WT pro-SP-C poly-Val and a designed poly-Leu transmembrane (TM) segment in the endoplasmic reticulum (ER) membrane. Furthermore, to understand how the pro-SP-C BRICHOS domain present in the ER lumen can interact with the TM segment of pro-SP-C, we studied the membrane insertion properties of the recombinant form of the pro-SP-C BRICHOS domain and two ILD-associated mutants. The results show that the co-translational folding of the WT pro-SP-C TM segment is inefficient, that the BRICHOS domain inserts into superficial parts of fluid membranes, and that BRICHOS membrane insertion is promoted by poly-Val peptides present in the membrane. In contrast, one BRICHOS and one non-BRICHOS ILD-associated mutant could not insert into membranes. These findings support a chaperone function of the BRICHOS domain, possibly together with the linker region, during pro-SP-C biosynthesis in the ER.
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Affiliation(s)
- Alejandra Sáenz
- From the Department of Biochemistry and Molecular Biology I, Complutense University of Madrid, 28040 Madrid, Spain, the Centro de Investigación Biomédica en Red de Enfermedades Respiratorias (CIBERES), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Jenny Presto
- the Center for Alzheimer Research, NVS (Neurobiology, Care Sciences, and Society) Department, Karolinska Institutet, S-141 57 Huddinge, Sweden, and
| | - Patricia Lara
- the Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, S-10691 Stockholm, Sweden
| | - Laura Akinyi-Oloo
- the Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, S-10691 Stockholm, Sweden
| | - Belén García-Fojeda
- the Centro de Investigación Biomédica en Red de Enfermedades Respiratorias (CIBERES), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - IngMarie Nilsson
- the Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, S-10691 Stockholm, Sweden
| | - Jan Johansson
- the Center for Alzheimer Research, NVS (Neurobiology, Care Sciences, and Society) Department, Karolinska Institutet, S-141 57 Huddinge, Sweden, and
| | - Cristina Casals
- From the Department of Biochemistry and Molecular Biology I, Complutense University of Madrid, 28040 Madrid, Spain, the Centro de Investigación Biomédica en Red de Enfermedades Respiratorias (CIBERES), Instituto de Salud Carlos III, 28029 Madrid, Spain,
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12
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Biverstål H, Dolfe L, Hermansson E, Leppert A, Reifenrath M, Winblad B, Presto J, Johansson J. Dissociation of a BRICHOS trimer into monomers leads to increased inhibitory effect on Aβ42 fibril formation. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1854:835-43. [PMID: 25891900 DOI: 10.1016/j.bbapap.2015.04.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Revised: 03/17/2015] [Accepted: 04/09/2015] [Indexed: 11/18/2022]
Abstract
The BRICHOS domain is associated with human amyloid disease, and it efficiently prevents amyloid fibril formation of the amyloid β-peptide (Aβ) in vitro and in vivo. Recombinant human prosurfactant protein C (proSP-C) BRICHOS domain forms a homotrimer as observed by x-ray crystallography, analytical ultracentrifugation, native polyacrylamide gel electrophoresis, analytical size exclusion chromatography and electrospray mass spectrometry. It was hypothesized that the trimer is an inactive storage form, as a putative substrate-binding site identified in the monomer, is buried in the subunit interface of the trimer. We show here increased dissociation of the BRICHOS trimer into monomers, by addition of detergents or of bis-ANS, known to bind to the putative substrate-binding site, or by introducing a Ser to Arg mutation expected to interfere with trimer formation. This leads to increased capacity to delay Aβ(42) fibril formation. Cross-linking of the BRICHOS trimer with glutaraldehyde, in contrast, renders it unable to affect Aβ(42) fibril formation. Moreover, proSP-C BRICHOS expressed in HEK293 cells is mainly monomeric, as detected by proximity ligation assay. Finally, proteolytic cleavage of BRICHOS in a loop region that is cleaved during proSP-C biosynthesis results in increased capacity to delay Aβ(42) fibril formation. These results indicate that modulation of the accessibility of the substrate-binding site is a means to regulate BRICHOS activity.
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Affiliation(s)
- Henrik Biverstål
- Karolinska Institutet, Department of NVS, Center for Alzheimer Research, Division of Neurogeriatrics, 141 57 Huddinge, Sweden.
| | - Lisa Dolfe
- Karolinska Institutet, Department of NVS, Center for Alzheimer Research, Division of Neurogeriatrics, 141 57 Huddinge, Sweden
| | - Erik Hermansson
- Karolinska Institutet, Department of NVS, Center for Alzheimer Research, Division of Neurogeriatrics, 141 57 Huddinge, Sweden
| | - Axel Leppert
- Karolinska Institutet, Department of NVS, Center for Alzheimer Research, Division of Neurogeriatrics, 141 57 Huddinge, Sweden
| | - Mara Reifenrath
- Karolinska Institutet, Department of NVS, Center for Alzheimer Research, Division of Neurogeriatrics, 141 57 Huddinge, Sweden
| | - Bengt Winblad
- Karolinska Institutet, Department of NVS, Center for Alzheimer Research, Division of Neurogeriatrics, 141 57 Huddinge, Sweden
| | - Jenny Presto
- Karolinska Institutet, Department of NVS, Center for Alzheimer Research, Division of Neurogeriatrics, 141 57 Huddinge, Sweden
| | - Jan Johansson
- Karolinska Institutet, Department of NVS, Center for Alzheimer Research, Division of Neurogeriatrics, 141 57 Huddinge, Sweden; Department of Anatomy, Physiology and Biochemistry, The Biomedical Centre, Swedish University of Agricultural Sciences, Box 575, 751 23 Uppsala, Sweden; Institute of Mathematics and Natural Sciences, Tallinn University, Narva mnt 25, Tallinn 101 20, Estonia
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13
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Roldan N, Goormaghtigh E, Pérez-Gil J, Garcia-Alvarez B. Palmitoylation as a key factor to modulate SP-C–lipid interactions in lung surfactant membrane multilayers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:184-91. [DOI: 10.1016/j.bbamem.2014.10.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2014] [Revised: 09/16/2014] [Accepted: 10/01/2014] [Indexed: 11/24/2022]
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14
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Walther FJ, Waring AJ, Hernández-Juviel JM, Ruchala P, Wang Z, Notter RH, Gordon LM. Surfactant protein C peptides with salt-bridges ("ion-locks") promote high surfactant activities by mimicking the α-helix and membrane topography of the native protein. PeerJ 2014; 2:e485. [PMID: 25083348 PMCID: PMC4106191 DOI: 10.7717/peerj.485] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Accepted: 06/23/2014] [Indexed: 11/20/2022] Open
Abstract
Background. Surfactant protein C (SP-C; 35 residues) in lungs has a cationic N-terminal domain with two cysteines covalently linked to palmitoyls and a C-terminal region enriched in Val, Leu and Ile. Native SP-C shows high surface activity, due to SP-C inserting in the bilayer with its cationic N-terminus binding to the polar headgroup and its hydrophobic C-terminus embedded as a tilted, transmembrane α-helix. The palmitoylcysteines in SP-C act as ‘helical adjuvants’ to maintain activity by overriding the β-sheet propensities of the native sequences. Objective. We studied SP-C peptides lacking palmitoyls, but containing glutamate and lysine at 4-residue intervals, to assess whether SP-C peptides with salt-bridges (“ion-locks”) promote surface activity by mimicking the α-helix and membrane topography of native SP-C. Methods. SP-C mimics were synthesized that reproduce native sequences, but without palmitoyls (i.e., SP-Css or SP-Cff, with serines or phenylalanines replacing the two cysteines). Ion-lock SP-C molecules were prepared by incorporating single or double Glu−–Lys+ into the parent SP-C’s. The secondary structures of SP-C mimics were studied with Fourier transform infrared (FTIR) spectroscopy and PASTA, an algorithm that predicts β-sheet propensities based on the energies of the various β-sheet pairings. The membrane topography of SP-C mimics was investigated with orientated and hydrogen/deuterium (H/D) exchange FTIR, and also Membrane Protein Explorer (MPEx) hydropathy analysis. In vitro surface activity was determined using adsorption surface pressure isotherms and captive bubble surfactometry, and in vivo surface activity from lung function measures in a rabbit model of surfactant deficiency. Results. PASTA calculations predicted that the SP-Css and SP-Cff peptides should each form parallel β-sheet aggregates, with FTIR spectroscopy confirming high parallel β-sheet with ‘amyloid-like’ properties. The enhanced β-sheet properties for SP-Css and SP-Cff are likely responsible for their low surfactant activities in the in vitro and in vivo assays. Although standard 12C-FTIR study showed that the α-helicity of these SP-C sequences in lipids was uniformly increased with Glu−–Lys+ insertions, elevated surfactant activity was only selectively observed. Additional results from oriented and H/D exchange FTIR experiments indicated that the high surfactant activities depend on the SP-C ion-locks recapitulating both the α-helicity and the membrane topography of native SP-C. SP-Css ion-lock 1, an SP-Css with a salt-bridge for a Glu−–Lys+ ion-pair predicted from MPEx hydropathy calculations, demonstrated enhanced surfactant activity and a transmembrane helix simulating those of native SP-C. Conclusion. Highly active SP-C mimics were developed that replace the palmitoyls of SP-C with intrapeptide salt-bridges and represent a new class of synthetic surfactants with therapeutic interest.
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Affiliation(s)
- Frans J Walther
- Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center , Torrance, CA , United States of America ; Department of Pediatrics, David Geffen School of Medicine, University of California at Los Angeles , Los Angeles, CA , United States of America
| | - Alan J Waring
- Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center , Torrance, CA , United States of America ; Department of Pediatrics, David Geffen School of Medicine, University of California at Los Angeles , Los Angeles, CA , United States of America ; Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles , Los Angeles, CA , United States of America ; Department of Physiology & Biophysics, School of Medicine, University of California , Irvine, CA , United States of America
| | - José M Hernández-Juviel
- Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center , Torrance, CA , United States of America
| | - Piotr Ruchala
- Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles , Los Angeles, CA , United States of America
| | - Zhengdong Wang
- Department of Pediatrics, University of Rochester , Rochester, NY , United States of America
| | - Robert H Notter
- Department of Pediatrics, University of Rochester , Rochester, NY , United States of America
| | - Larry M Gordon
- Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center , Torrance, CA , United States of America
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15
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Glasser SW, Maxfield MD, Ruetschilling TL, Akinbi HT, Baatz JE, Kitzmiller JA, Page K, Xu Y, Bao EL, Korfhagen TR. Persistence of LPS-induced lung inflammation in surfactant protein-C-deficient mice. Am J Respir Cell Mol Biol 2013; 49:845-54. [PMID: 23795648 DOI: 10.1165/rcmb.2012-0374oc] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Pulmonary surfactant protein-C (SP-C) gene-targeted mice (Sftpc(-/-)) develop progressive lung inflammation and remodeling. We hypothesized that SP-C deficiency reduces the ability to suppress repetitive inflammatory injury. Sftpc(+/+) and Sftpc(-/-) mice given three doses of bacterial LPS developed airway and airspace inflammation, which was more intense in the Sftpc(-/-) mice at 3 and 5 days after the final dose. Compared with Sftpc(+/+)mice, inflammatory injury persisted in the lungs of Sftpc(-/-) mice 30 days after the final LPS challenge. Sftpc(-/-) mice showed LPS-induced airway goblet cell hyperplasia with increased detection of Sam pointed Ets domain and FoxA3 transcription factors. Sftpc(-/-) type II alveolar epithelial cells had increased cytokine expression after LPS exposure relative to Sftpc(+/+) cells, indicating that type II cell dysfunction contributes to inflammatory sensitivity. Microarray analyses of isolated type II cells identified a pattern of enhanced expression of inflammatory genes consistent with an intrinsic low-level inflammation resulting from SP-C deficiency. SP-C-containing clinical surfactant extract (Survanta) or SP-C/phospholipid vesicles blocked LPS signaling through the LPS receptor (Toll-like receptor [TLR] 4/CD14/MD2) in human embryonic kidney 293T cells, indicating that SP-C blocks LPS-induced cytokine production by a TLR4-dependent mechanism. Phospholipid vesicles alone did not modify the TLR4 response. In vivo deficiency of SP-C leads to inflammation, increased cytokine production by type II cells, and persistent inflammation after repetitive LPS stimulation.
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16
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Carvalheda CA, Campos SRR, Machuqueiro M, Baptista AM. Structural Effects of pH and Deacylation on Surfactant Protein C in an Organic Solvent Mixture: A Constant-pH MD Study. J Chem Inf Model 2013; 53:2979-89. [DOI: 10.1021/ci400479c] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Catarina A. Carvalheda
- Instituto de Tecnologia Química
e Biológica, Universidade Nova de Lisboa, Av. da República, EAN, 2780-157 Oeiras, Portugal
| | - Sara R. R. Campos
- Instituto de Tecnologia Química
e Biológica, Universidade Nova de Lisboa, Av. da República, EAN, 2780-157 Oeiras, Portugal
| | - Miguel Machuqueiro
- Centro de Química e Bioquímica, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, C8, 1749-016 Lisboa, Portugal
| | - António M. Baptista
- Instituto de Tecnologia Química
e Biológica, Universidade Nova de Lisboa, Av. da República, EAN, 2780-157 Oeiras, Portugal
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17
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Abstract
The assembly of proteins into amyloid fibrils can be an element of both protein aggregation diseases and a functional unit in healthy biological pathways. In both cases, it must be kept under tight control to prevent undesired aggregation. In normophysiology, proteins can self-chaperone amyloidogenic segments by restricting their conformational flexibility in an overall stabilizing protein fold. However, some aggregation-prone segments cannot be controlled in this manner and require additional regulatory elements to limit fibrillation. The present review summarizes different molecular mechanisms that proteins use to control their own assembly into fibrils, such as the inclusion of a chaperoning domain or a blocking segment in the proform, the controlled release of an amyloidogenic region from the folded protein, or the adjustment of fibrillation propensity according to pH. Autoregulatory elements can control disease-related as well as functional fibrillar protein assemblies and distinguish a group of self-regulating amyloids across a wide range of biological functions and organisms.
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18
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BRICHOS domain associated with lung fibrosis, dementia and cancer - a chaperone that prevents amyloid fibril formation? FEBS J 2011; 278:3893-904. [DOI: 10.1111/j.1742-4658.2011.08209.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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19
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Nakahara H, Lee S, Shibata O. Specific interaction restrains structural transitions of an amphiphilic peptide in pulmonary surfactant model systems: An in situ PM-IRRAS investigation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:1263-71. [DOI: 10.1016/j.bbamem.2010.02.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Revised: 02/06/2010] [Accepted: 02/12/2010] [Indexed: 10/19/2022]
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20
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Walther FJ, Waring AJ, Hernandez-Juviel JM, Gordon LM, Wang Z, Jung CL, Ruchala P, Clark AP, Smith WM, Sharma S, Notter RH. Critical structural and functional roles for the N-terminal insertion sequence in surfactant protein B analogs. PLoS One 2010; 5:e8672. [PMID: 20084172 PMCID: PMC2805716 DOI: 10.1371/journal.pone.0008672] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Accepted: 12/18/2009] [Indexed: 01/14/2023] Open
Abstract
Background Surfactant protein B (SP-B; 79 residues) belongs to the saposin protein superfamily, and plays functional roles in lung surfactant. The disulfide cross-linked, N- and C-terminal domains of SP-B have been theoretically predicted to fold as charged, amphipathic helices, suggesting their participation in surfactant activities. Earlier structural studies with Mini-B, a disulfide-linked construct based on the N- and C-terminal regions of SP-B (i.e., ∼residues 8–25 and 63–78), confirmed that these neighboring domains are helical; moreover, Mini-B retains critical in vitro and in vivo surfactant functions of the native protein. Here, we perform similar analyses on a Super Mini-B construct that has native SP-B residues (1–7) attached to the N-terminus of Mini-B, to test whether the N-terminal sequence is also involved in surfactant activity. Methodology/Results FTIR spectra of Mini-B and Super Mini-B in either lipids or lipid-mimics indicated that these peptides share similar conformations, with primary α-helix and secondary β-sheet and loop-turns. Gel electrophoresis demonstrated that Super Mini-B was dimeric in SDS detergent-polyacrylamide, while Mini-B was monomeric. Surface plasmon resonance (SPR), predictive aggregation algorithms, and molecular dynamics (MD) and docking simulations further suggested a preliminary model for dimeric Super Mini-B, in which monomers self-associate to form a dimer peptide with a “saposin-like” fold. Similar to native SP-B, both Mini-B and Super Mini-B exhibit in vitro activity with spread films showing near-zero minimum surface tension during cycling using captive bubble surfactometry. In vivo, Super Mini-B demonstrates oxygenation and dynamic compliance that are greater than Mini-B and compare favorably to full-length SP-B. Conclusion Super Mini-B shows enhanced surfactant activity, probably due to the self-assembly of monomer peptide into dimer Super Mini-B that mimics the functions and putative structure of native SP-B.
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Affiliation(s)
- Frans J Walther
- Los Angeles Biomedical Research Institute at Harbor, University of California Los Angeles Medical Center, Torrance, California, USA.
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21
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Johansson H, Eriksson M, Nordling K, Presto J, Johansson J. The Brichos domain of prosurfactant protein C can hold and fold a transmembrane segment. Protein Sci 2009; 18:1175-82. [PMID: 19472327 DOI: 10.1002/pro.123] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Prosurfactant protein C (proSP-C) is a 197-residue integral membrane protein, in which the C-terminal domain (CTC, positions 59-197) is localized in the endoplasmic reticulum (ER) lumen and contains a Brichos domain (positions 94-197). Mature SP-C corresponds largely to the transmembrane (TM) region of proSP-C. CTC binds to SP-C, provided that it is in nonhelical conformation, and can prevent formation of intracellular amyloid-like inclusions of proSP-C that harbor mutations linked to interstitial lung disease (ILD). Herein it is shown that expression of proSP-C (1-58), that is, the N-terminal propeptide and the TM region, in HEK293 cells results in virtually no detectable protein, while coexpression of CTC in trans yields SDS-soluble monomeric proSP-C (1-58). Recombinant human (rh) CTC binds to cellulose-bound peptides derived from the nonpolar TM region, but not the polar cytosolic part, of proSP-C, and requires >/=5-residues for maximal binding. Binding of rhCTC to a nonhelical peptide derived from SP-C results in alpha-helix formation provided that it contains a long TM segment. Finally, rhCTC and rhCTC Brichos domain shows very similar substrate specificities, but rhCTC(L188Q), a mutation linked to ILD is unable to bind all peptides analyzed. These data indicate that the Brichos domain of proSP-C is a chaperone that induces alpha-helix formation of an aggregation-prone TM region.
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Affiliation(s)
- Hanna Johansson
- Department of Anatomy, Physiology and Biochemistry, SLU, The Biomedical Centre, Uppsala, Sweden
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22
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Glasser SW, Witt TL, Senft AP, Baatz JE, Folger D, Maxfield MD, Akinbi HT, Newton DA, Prows DR, Korfhagen TR. Surfactant protein C-deficient mice are susceptible to respiratory syncytial virus infection. Am J Physiol Lung Cell Mol Physiol 2009; 297:L64-72. [PMID: 19304906 DOI: 10.1152/ajplung.90640.2008] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Patients with mutations in the pulmonary surfactant protein C (SP-C) gene develop interstitial lung disease and pulmonary exacerbations associated with viral infections including respiratory syncytial virus (RSV). Pulmonary infection with RSV caused more severe interstitial thickening, air space consolidation, and goblet cell hyperplasia in SP-C-deficient (Sftpc(-/-)) mice compared with SP-C replete mice. The RSV-induced pathology resolved more slowly in Sftpc(-/-) mice with lung inflammation persistent up to 30 days postinfection. Polymorphonuclear leukocyte and macrophage counts were increased in the bronchoalveolar lavage (BAL) fluid of Sftpc(-/-) mice. Viral titers and viral F and G protein mRNA were significantly increased in both Sftpc(-/-) and heterozygous Sftpc(+/-) mice compared with controls. Expression of Toll-like receptor 3 (TLR3) mRNA was increased in the lungs of Sftpc(-/-) mice relative to Sftpc(+/+) mice before and after RSV infection. Consistent with the increased TLR3 expression, BAL inflammatory cells were increased in the Sftpc(-/-) mice after exposure to a TLR3-specific ligand, poly(I:C). Preparations of purified SP-C and synthetic phospholipids blocked poly(I:C)-induced TLR3 signaling in vitro. SP-C deficiency increases the severity of RSV-induced pulmonary inflammation through regulation of TLR3 signaling.
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Affiliation(s)
- Stephan W Glasser
- Division of Pulmonary Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229-3039, USA.
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23
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Stenger PC, Alonso C, Zasadzinski JA, Waring AJ, Jung CL, Pinkerton KE. Environmental tobacco smoke effects on lung surfactant film organization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1788:358-70. [PMID: 19118518 DOI: 10.1016/j.bbamem.2008.11.021] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Revised: 11/13/2008] [Accepted: 11/14/2008] [Indexed: 01/05/2023]
Abstract
Adsorption of the clinical lung surfactants (LS) Curosurf or Survanta from aqueous suspension to the air-water interface progresses from multi-bilayer aggregates through multilayer films to a coexistence between multilayer and monolayer domains. Exposure to environmental tobacco smoke (ETS) alters this progression as shown by Langmuir isotherms, fluorescence microscopy and atomic force microscopy (AFM). After 12 h of LS exposure to ETS, AFM images of Langmuir-Blodgett deposited films show that ETS reduces the amount of material near the interface and alters how surfactant is removed from the interface during compression. For Curosurf, ETS prevents refining of the film composition during cycling; this leads to higher minimum surface tensions. ETS also changes the morphology of the Curosurf film by reducing the size of condensed phase domains from 8-12 microm to approximately 2 microm, suggesting a decrease in the line tension between the domains. The minimum surface tension and morphology of the Survanta film are less impacted by ETS exposure, although the amount of material associated with the film is reduced in a similar way to Curosurf. Fluorescence and mass spectra of Survanta dispersions containing native bovine SP-B treated with ETS indicate the oxidative degradation of protein aromatic amino acid residue side chains. Native bovine SP-C isolated from ETS exposed Survanta had changes in molecular mass consistent with deacylation of the lipoprotein. Fourier Transform Infrared Spectroscopy (FTIR) characterization of the hydrophobic proteins from ETS treated Survanta dispersions show significant changes in the conformation of SP-B and SP-C that correlate with the altered surface activity and morphology of the lipid-protein film.
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Affiliation(s)
- Patrick C Stenger
- Department of Chemical Engineering, University of California, Santa Barbara, CA 93106-5080, USA
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24
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Plasencia I, Baumgart F, Andreu D, Marsh D, Pérez-Gil J. Effect of acylation on the interaction of the N-Terminal segment of pulmonary surfactant protein SP-C with phospholipid membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:1274-82. [DOI: 10.1016/j.bbamem.2008.02.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2007] [Revised: 01/22/2008] [Accepted: 02/07/2008] [Indexed: 02/02/2023]
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25
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HASEGAWA T, ITOH Y, KASUYA A. Experimental Optimization of p-Polarized MAIR Spectrometry Performed on a Fourier Transform Infrared Spectrometer. ANAL SCI 2008; 24:105-9. [DOI: 10.2116/analsci.24.105] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Takeshi HASEGAWA
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology
- PRESTO, Japan Science and Technology Agency
| | - Yuki ITOH
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology
| | - Akiyoshi KASUYA
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology
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26
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Mulugeta S, Maguire JA, Newitt JL, Russo SJ, Kotorashvili A, Beers MF. Misfolded BRICHOS SP-C mutant proteins induce apoptosis via caspase-4- and cytochrome c-related mechanisms. Am J Physiol Lung Cell Mol Physiol 2007; 293:L720-9. [PMID: 17586700 DOI: 10.1152/ajplung.00025.2007] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Several mutations within the BRICHOS domain of surfactant protein C (SP-C) have been linked to interstitial lung disease. Recent studies have suggested that these mutations cause misfolding of the proprotein (proSP-C), which initiates the unfolded protein response to resolve improper folding or promote protein degradation. We have reported that in vitro expression of one of these proteins, the exon 4 deletion mutant (hSP-CΔexon4), causes endoplasmic reticulum (ER) stress, inhibits proteasome function, and activates caspase-3-mediated apoptosis. To further elucidate mechanisms and common pathways for cellular dysfunction, various assays were performed by transiently expressing two SP-C BRICHOS domain mutant (BRISPC) proteins (hSP-CΔexon4, hSP-CL188Q) and control proteins in lung epithelium-derived A549 and kidney epithelium-derived (HEK-293) GFPu-1 cell lines. Compared with controls, cells expressing either BRICHOS mutant protein consistently exhibited increased formation of insoluble aggregates, enhanced promotion of inositol-requiring enzyme 1-dependent splicing of X-box binding protein-1 (XBP-1), significant inhibition of proteasome activity, enhanced induction of mitochondrial cytochrome c release, and increased activations of caspase-4 and caspase-3, leading to apoptosis. These results suggest common cellular responses, including initiation of cell-death signaling pathways, to these lung disease-associated BRISPC proteins.
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Affiliation(s)
- Surafel Mulugeta
- Pulmonary, Allergy, and Critical Care Division, Univ. of Pennsylvania School of Medicine, Vernon & Shirley Hill Pavilion, Suite H418, 380 South Univ. Ave., Philadelphia, PA 19104, USA.
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27
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Meister A, Nicolini C, Waldmann H, Kuhlmann J, Kerth A, Winter R, Blume A. Insertion of lipidated Ras proteins into lipid monolayers studied by infrared reflection absorption spectroscopy (IRRAS). Biophys J 2006; 91:1388-401. [PMID: 16731561 PMCID: PMC1518660 DOI: 10.1529/biophysj.106.084624] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2006] [Accepted: 05/15/2006] [Indexed: 11/18/2022] Open
Abstract
Ras proteins have to be associated with the inner leaflet of the plasma membrane to perform their signaling functions. This membrane targeting and binding is controlled by post-translational covalent attachment of farnesyl and palmitoyl chains to cysteines in the membrane anchor region of the N- and H-Ras isoforms. Two N-Ras lipoproteins were investigated, namely a farnesylated and hexadecylated protein, presenting the natural hydrophobic modifications and a doubly hexadecylated construct, respectively. The proteins are surface active and form a Gibbs monolayer at the air-D2O interface. The contours of the amide-I bands were analyzed using infrared reflection absorption spectroscopy (IRRAS). Langmuir monolayers of a mixture of POPC, brain sphingomyelin, and cholesterol were used as half of a model biomembrane to study the insertion of these N-Ras proteins. They insert with their hydrophobic anchors into lipid monolayers but at higher surface pressures (30 mN/m); the farnesylated and hexadecylated protein desorbs completely from the monolayer, whereas the doubly hexadecylated protein remains incorporated. During the insertion process, changes in the orientation of the protein secondary structure were detected by comparison with simulated IRRA spectra, based on the information on the relative orientation of the secondary structure elements from the protein crystal structure data.
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Affiliation(s)
- Annette Meister
- Institut für Physikalische Chemie, Martin-Luther-Universität Halle-Wittenberg, Halle, Germany
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28
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Li J, Liepinsh E, Almlén A, Thyberg J, Curstedt T, Jörnvall H, Johansson J. Structure and influence on stability and activity of the N-terminal propeptide part of lung surfactant protein C. FEBS J 2006; 273:926-35. [PMID: 16478467 DOI: 10.1111/j.1742-4658.2006.05124.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Mature lung surfactant protein C (SP-C) corresponds to residues 24-58 of the 21 kDa proSP-C. A late processing intermediate, SP-Ci, corresponding to residues 12-58 of proSP-C, lacks the surface activity of SP-C, and the SP-Ci alpha-helical structure does not unfold in contrast to the metastable nature of the SP-C helix. The NMR structure of an analogue of SP-Ci, SP-Ci(1-31), with two palmitoylCys replaced by Phe and four Val replaced by Leu, in dodecylphosphocholine micelles and in ethanol shows that its alpha-helix vs. that of SP-C is extended N-terminally. The Arg-Phe part in SP-Ci that is cleaved to generate SP-C is localized in a turn structure, which is followed by a short segment in extended conformation. Circular dichroism spectroscopy of SP-Ci(1-31) in microsomal or surfactant lipids shows a mixture of helical and extended conformation at pH 6, and a shift to more unordered structure at pH 5. Replacement of the N-terminal hexapeptide segment SPPDYS (known to constitute a signal in intracellular targeting) of SP-Ci with AAAAAA results in a peptide that is mainly unstructured, independent of pH, in microsomal and surfactant lipids. Addition of a synthetic dodecapeptide, corresponding to the propeptide part of SP-Ci, to mature SP-C results in slower aggregation kinetics and altered amyloid fibril formation, and reduces the surface activity of phospholipid-bound SP-C. These data suggest that the propeptide part of SP-Ci prevents unfolding by locking the N-terminal part of the helix, and that acidic pH results in structural disordering of the region that is proteolytically cleaved to generate SP-C.
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Affiliation(s)
- Jing Li
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
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29
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Ramírez E, Santana A, Cruz A, Plasencia I, López GE. Molecular dynamics of surfactant protein C: from single molecule to heptameric aggregates. Biophys J 2006; 90:2698-705. [PMID: 16443648 PMCID: PMC1414559 DOI: 10.1529/biophysj.105.073270] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Surfactant protein C (SP-C) is a membrane-associated protein essential for normal respiration. It has been found that the alpha-helix form of SP-C can undergo, under certain conditions, a transformation from an alpha-helix to a beta-strand conformation that closely resembles amyloid fibrils, which are possible contributors to the pathogenesis of pulmonary alveolar proteinosis. Molecular dynamics simulations using the NAMD2 package were performed for systems containing from one to seven SP-C molecules to study their behavior in water. The results of our simulations show that unfolding of the protein occurs at the amino terminal, and despite this unfolding, no transition from alpha-helix to beta-strand was observed.
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Affiliation(s)
- Eunice Ramírez
- Department of Chemistry, University of Puerto Rico, Mayagüez, Puerto Rico 00681
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30
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Ng AW, Bidani A, Heming TA. Innate host defense of the lung: effects of lung-lining fluid pH. Lung 2005; 182:297-317. [PMID: 15742242 DOI: 10.1007/s00408-004-2511-6] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/02/2004] [Indexed: 10/25/2022]
Abstract
Lung-lining fluid (LLF) is a primary constituent of the pulmonary host defense system. It is distributed continuously throughout the respiratory tract but is heterogeneous regarding its chemistry and physiology between the conducting airways and alveoli. The conducting airways are lined with airway surface liquid (ASL), a mucus gel-aqueous sol complex that interacts functionally with epithelial cilia as the mucociliary escalator. The alveoli are lined with alveolar subphase fluid (AVSF) and pulmonary surfactant. AVSF sterility is maintained in part by the phagocytic activity of resident alveolar macrophages. Normal ASL and AVSF are both more acidic than blood plasma. However, the details of acid-base regulation differ between the two media. Appreciable transepithelial acid-base flux is possible across the airway epithelium, whereas the alveolar epithelium is relatively impermeable to transepithelial acid-base flux. Moreover, one must consider the influence of resident macrophages on AVSF pH. Resident macrophages occupy a sizable fraction of AVSF by volume and are a substantial source of metabolic H+. The buffering capacities of ASL and AVSF probably are largely due to secreted peptides (e.g., ASL mucins and AVSF surfactant proteins). Acid-base exchange between the extracellular hydrophase and intracellular buffering systems of resident macrophages represents an additional buffer pool for AVSF. The pH of ASL and AVSF can be depressed by disease or inflammation. Low pH is predicted to suppress microbe clearance from the airways and alveoli, increase pathogen survival in both regions, and alter mediator release by resident macrophages and recruited leukocytes thereby increasing the propensity for bystander cell injury. Overall, ASL/AVSF pH is expected to be a major determinant of lung host defense responses.
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Affiliation(s)
- Amelia W Ng
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
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31
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Shanmukh S, Biswas N, Waring AJ, Walther FJ, Wang Z, Chang Y, Notter RH, Dluhy RA. Structure and properties of phospholipid-peptide monolayers containing monomeric SP-B(1-25) II. Peptide conformation by infrared spectroscopy. Biophys Chem 2005; 113:233-44. [PMID: 15620508 DOI: 10.1016/j.bpc.2004.09.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2004] [Revised: 09/15/2004] [Accepted: 09/15/2004] [Indexed: 11/20/2022]
Abstract
The conformation and orientation of synthetic monomeric human sequence SP-B(1-25) (mSP-B(1-25)) was studied in films with phospholipids at the air-water (A/W) interface by polarization modulation infrared reflectance absorption spectroscopy (PM-IRRAS). Modified two-dimensional infrared (2D IR) correlation analysis was applied to PM-IRRAS spectra to define changes in the secondary structure and rates of reorientation of mSP-B(1-25) in the monolayer during compression. PM-IRRAS spectra and 2D IR correlation analysis showed that, in pure films, mSP-B(1-25) had a major alpha-helical conformation plus regions of beta-sheet structure. These alpha-helical regions reoriented later during film compression than beta structural regions, and became oriented normal to the A/W interface as surface pressure increased. In mixed films with 4:1 mol:mol acyl chain perdeuterated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/1,2-dioleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (sodium salt) (DPPC-d(62):DOPG), the IR spectra of mSP-B(1-25) showed that a significant, concentration-dependent conformational change occurred when mSP-B(1-25) was incorporated into a DPPC-d(62):DOPG monolayer. At an mSP-B(1-25) concentration of 10 wt.%, the peptide assumed a predominantly beta-sheet conformation with no contribution from alpha-helical structures. At lower, more physiological peptide concentrations, 2D IR correlation analysis showed that the propensity of mSP-B(1-25) to form alpha-helical structures was increased. In phospholipid films containing 5 wt.% mSP-B(1-25), a substantial alpha-helical peptide structural component was observed, but regions of alpha and beta structure reoriented together rather than independently during compression. In films containing 1 wt.% mSP-B(1-25), peptide conformation was predominantly alpha-helical and the helical regions reoriented later during compression than the remaining beta structural components. The increased alpha-helical structure of mSP-B(1-25) demonstrated here by PM-IRRAS and 2D IR correlation analysis in monolayers of 4:1 DPPC:DOPG containing 1 wt.% (and, to a lesser extent, 5 wt.%) peptide may be relevant for the formation of the intermediate order 'dendritic' surface phase observed in similar surface films by epi-fluorescence.
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Abstract
Surfactant protein C (SP-C) is a hydrophobic 35-amino acid peptide that co-isolates with the phospholipid fraction of lung surfactant. SP-C represents a structurally and functionally challenging protein for the alveolar type 2 cell, which must synthesize, traffic, and process a 191-197-amino acid precursor protein through the regulated secretory pathway. The current understanding of SP-C biosynthesis considers the SP-C proprotein (proSP-C) as a hybrid molecule that incorporates structural and functional features of both bitopic integral membrane proteins and more classically recognized luminal propeptide hormones, which are subject to post-translational processing and regulated exocytosis. Adding to the importance of a detailed understanding of SP-C biosynthesis has been the recent association of mutations in the proSP-C sequence with chronic interstitial pneumonias in children and adults. Many of these mutations involve either missense or deletion mutations located in a region of the proSP-C molecule that has structural homology to the BRI family of proteins linked to inherited degenerative dementias. This review examines the current state of SP-C biosynthesis with a focus on recent developments related to molecular and cellular mechanisms implicated in the emerging role of SP-C mutations in the pathophysiology of diffuse parenchymal lung disease.
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Affiliation(s)
- Michael F Beers
- Pulmonary and Critical Care Division, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6061, USA.
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33
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Li J, Hosia W, Hamvas A, Thyberg J, Jörnvall H, Weaver TE, Johansson J. The N-terminal Propeptide of Lung Surfactant Protein C is Necessary for Biosynthesis and Prevents Unfolding of a Metastable α-Helix. J Mol Biol 2004; 338:857-62. [PMID: 15111052 DOI: 10.1016/j.jmb.2004.03.051] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2003] [Revised: 03/07/2004] [Accepted: 03/12/2004] [Indexed: 11/18/2022]
Abstract
The lung surfactant-associated protein C (SP-C) consists mainly of a polyvaline alpha-helix, which is stable in a lipid membrane. However, in agreement with the predicted beta-strand conformation of a polyvaline segment, helical SP-C unfolds and transforms into beta-sheet aggregates and amyloid fibrils within a few days in aqueous organic solvents. SP-C fibril formation and aggregation have been associated with lung disease. Here, we show that in a recently isolated biosynthetic precursor of SP-C (SP-Ci), a 12 residue N-terminal propeptide locks the metastable polyvaline part in a helical conformation. The SP-Ci helix does not aggregate or unfold during several weeks of incubation, as judged by hydrogen/deuterium exchange and mass spectrometry. Hydrogen/deuterium exchange experiments further indicate that the propeptide reduces exchange in parts corresponding to mature SP-C. Finally, in an acidic environment, SP-Ci unfolds and aggregates into amyloid fibrils like SP-C. These data suggest a direct role of the N-terminal propeptide in SP-C biosynthesis.
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Affiliation(s)
- Jing Li
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden
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34
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Ng AW, Bidani A, Heming TA. Innate host defense of the lung: effects of lung-lining fluid pH. Lung 2004; 182:297-317. [PMID: 15742242 DOI: 10.1007/s00408004-2511-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/02/2004] [Indexed: 05/23/2023]
Abstract
Lung-lining fluid (LLF) is a primary constituent of the pulmonary host defense system. It is distributed continuously throughout the respiratory tract but is heterogeneous regarding its chemistry and physiology between the conducting airways and alveoli. The conducting airways are lined with airway surface liquid (ASL), a mucus gel-aqueous sol complex that interacts functionally with epithelial cilia as the mucociliary escalator. The alveoli are lined with alveolar subphase fluid (AVSF) and pulmonary surfactant. AVSF sterility is maintained in part by the phagocytic activity of resident alveolar macrophages. Normal ASL and AVSF are both more acidic than blood plasma. However, the details of acid-base regulation differ between the two media. Appreciable transepithelial acid-base flux is possible across the airway epithelium, whereas the alveolar epithelium is relatively impermeable to transepithelial acid-base flux. Moreover, one must consider the influence of resident macrophages on AVSF pH. Resident macrophages occupy a sizable fraction of AVSF by volume and are a substantial source of metabolic H+. The buffering capacities of ASL and AVSF probably are largely due to secreted peptides (e.g., ASL mucins and AVSF surfactant proteins). Acid-base exchange between the extracellular hydrophase and intracellular buffering systems of resident macrophages represents an additional buffer pool for AVSF. The pH of ASL and AVSF can be depressed by disease or inflammation. Low pH is predicted to suppress microbe clearance from the airways and alveoli, increase pathogen survival in both regions, and alter mediator release by resident macrophages and recruited leukocytes thereby increasing the propensity for bystander cell injury. Overall, ASL/AVSF pH is expected to be a major determinant of lung host defense responses.
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Affiliation(s)
- Amelia W Ng
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
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