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Xu W, Ma X, Wang Q, Ye J, Wang N, Ye Z, Chen T. GCN5L1 regulates pulmonary surfactant production by modulating lamellar body biogenesis and trafficking in mouse alveolar epithelial cells. Cell Mol Biol Lett 2023; 28:90. [PMID: 37936104 PMCID: PMC10631113 DOI: 10.1186/s11658-023-00506-0] [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: 06/05/2023] [Accepted: 10/25/2023] [Indexed: 11/09/2023] Open
Abstract
BACKGROUND The pulmonary surfactant that lines the air-liquid surface within alveoli is a protein-lipid mixture essential for gas exchange. Surfactant lipids and proteins are synthesized and stored in the lamellar body (LB) before being secreted from alveolar type II (AT2) cells. The molecular and cellular mechanisms that regulate these processes are incompletely understood. We previously identified an essential role of general control of amino acid synthesis 5 like 1 (GCN5L1) and the biogenesis of lysosome-related organelle complex 1 subunit 1 (BLOS1) in surfactant system development in zebrafish. Here, we explored the role of GCN5L1 in pulmonary surfactant regulation. METHOD GCN5L1 knockout cell lines were generated with the CRISPR/Cas9 system. Cell viability was analyzed by MTT assay. Released surfactant proteins were measured by ELISA. Released surfactant lipids were measured based on coupled enzymatic reactions. Gene overexpression was mediated through lentivirus. The RNA levels were detected through RNA-sequencing (RNA-seq) and quantitative reverse transcription (qRT)- polymerase chain reaction (PCR). The protein levels were detected through western blotting. The cellular localization was analyzed by immunofluorescence. Morphology of the lamellar body was analyzed through transmission electron microscopy (TEM), Lysotracker staining, and BODIPY phosphatidylcholine labeling. RESULTS Knocking out GCN5L1 in MLE-12 significantly decreased the release of surfactant proteins and lipids. We detected the downregulation of some surfactant-related genes and misregulation of the ROS-Erk-Foxo1-Cebpα axis in mutant cells. Modulating the activity of the axis or reconstructing the mitochondrial expression of GCN5L1 could partially restore the expression of these surfactant-related genes. We further showed that MLE-12 cells contained many LB-like organelles that were lipid enriched and positive for multiple LB markers. These organelles were smaller in size and accumulated in the absence of GCN5L1, indicating both biogenesis and trafficking defects. Accumulated endogenous surfactant protein (SP)-B or exogenously expressed SP-B/SP-C in adenosine triphosphate-binding cassette transporterA3 (ABCA3)-positive organelles was detected in mutant cells. GCN5L1 localized to the mitochondria and LBs. Reconstruction of mitochondrial GCN5L1 expression rescued the organelle morphology but failed to restore the trafficking defect and surfactant release, indicating specific roles associated with different subcellular localizations. CONCLUSIONS In summary, our study identified GCN5L1 as a new regulator of pulmonary surfactant that plays a role in the biogenesis and positioning/trafficking of surfactant-containing LBs.
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Affiliation(s)
- Wenqin Xu
- Central Laboratory, Yijishan Hospital of Wannan Medical College, Wuhu, China
- Anhui Province Key Laboratory of Non-Coding RNA Basic and Clinical Transformation, Wannan Medical College, Wuhu, China
- Clinical Research Center for Critical Respiratory Medicine of Anhui Province, Wannan Medical College, Wuhu, China
| | - Xiaocui Ma
- Henan Clinical Research Center of Childhood Diseases, Children's Hospital Affiliated to Zhengzhou University, Zhengzhou, China
| | - Qing Wang
- Central Laboratory, Yijishan Hospital of Wannan Medical College, Wuhu, China
- Anhui Province Key Laboratory of Non-Coding RNA Basic and Clinical Transformation, Wannan Medical College, Wuhu, China
- Clinical Research Center for Critical Respiratory Medicine of Anhui Province, Wannan Medical College, Wuhu, China
| | - Jingjing Ye
- Central Laboratory, Yijishan Hospital of Wannan Medical College, Wuhu, China
- Anhui Province Key Laboratory of Non-Coding RNA Basic and Clinical Transformation, Wannan Medical College, Wuhu, China
- Clinical Research Center for Critical Respiratory Medicine of Anhui Province, Wannan Medical College, Wuhu, China
| | - Nengqian Wang
- Department of Pediatrics, Yijishan Hospital of Wannan Medical College, Wuhu, China
| | - Zhenzhen Ye
- Department of Pediatrics, Yijishan Hospital of Wannan Medical College, Wuhu, China
| | - Tianbing Chen
- Central Laboratory, Yijishan Hospital of Wannan Medical College, Wuhu, China.
- Anhui Province Key Laboratory of Non-Coding RNA Basic and Clinical Transformation, Wannan Medical College, Wuhu, China.
- Clinical Research Center for Critical Respiratory Medicine of Anhui Province, Wannan Medical College, Wuhu, China.
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Waring AJ, Whitelegge JP, Sharma SK, Gordon LM, Walther FJ. Emulation of the structure of the Saposin protein fold by a lung surfactant peptide construct of surfactant Protein B. PLoS One 2022; 17:e0276787. [PMID: 36327300 PMCID: PMC9632872 DOI: 10.1371/journal.pone.0276787] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 10/14/2022] [Indexed: 11/06/2022] Open
Abstract
The three-dimensional structure of the synthetic lung Surfactant Protein B Peptide Super Mini-B was determined using an integrative experimental approach, including mass spectrometry and isotope enhanced Fourier-transform infrared (FTIR) spectroscopy. Mass spectral analysis of the peptide, oxidized by solvent assisted region-specific disulfide formation, confirmed that the correct folding and disulfide pairing could be facilitated using two different oxidative structure-promoting solvent systems. Residue specific analysis by isotope enhanced FTIR indicated that the N-terminal and C-terminal domains have well defined α-helical amino acid sequences. Using these experimentally derived measures of distance constraints and disulfide connectivity, the ensemble was further refined with molecular dynamics to provide a medium resolution, residue-specific structure for the peptide construct in a simulated synthetic lung surfactant lipid multilayer environment. The disulfide connectivity combined with the α-helical elements stabilize the peptide conformationally to form a helical hairpin structure that resembles critical elements of the Saposin protein fold of the predicted full-length Surfactant Protein B structure.
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Affiliation(s)
- Alan J. Waring
- Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, California, United States of America
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Julian P. Whitelegge
- Jane & Terry Semel Institute for Neuroscience and Human Behavior, Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Shantanu K. Sharma
- Materials and Process Simulation Center, California Institute of Technology, Pasadena, California, United States of America
| | - Larry M. Gordon
- Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, California, United States of America
| | - Frans J. Walther
- Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, California, United States of America
- Department of Pediatrics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
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The lung surfactant activity probed with molecular dynamics simulations. Adv Colloid Interface Sci 2022; 304:102659. [PMID: 35421637 DOI: 10.1016/j.cis.2022.102659] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Revised: 03/18/2022] [Accepted: 03/31/2022] [Indexed: 01/17/2023]
Abstract
The surface of pulmonary alveolar subphase is covered with a mixture of lipids and proteins. This lung surfactant plays a crucial role in lung functioning. It shows a complex phase behavior which can be altered by the interaction with third molecules such as drugs or pollutants. For studying multicomponent biological systems, it is of interest to couple experimental approach with computational modelling yielding atomic-scale information. Simple two, three, or four-component model systems showed to be useful for getting more insight in the interaction between lipids, lipids and proteins or lipids and proteins with drugs and impurities. These systems were studied theoretically using molecular dynamic simulations and experimentally by means of the Langmuir technique. A better understanding of the structure and behavior of lung surfactants obtained from this research is relevant for developing new synthetic surfactants for efficient therapies, and may contribute to public health protection.
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Liekkinen J, de Santos Moreno B, Paananen RO, Vattulainen I, Monticelli L, Bernardino de la Serna J, Javanainen M. Understanding the Functional Properties of Lipid Heterogeneity in Pulmonary Surfactant Monolayers at the Atomistic Level. Front Cell Dev Biol 2020; 8:581016. [PMID: 33304898 PMCID: PMC7701215 DOI: 10.3389/fcell.2020.581016] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 10/16/2020] [Indexed: 01/11/2023] Open
Abstract
Pulmonary surfactant is a complex mixture of lipids and proteins lining the interior of the alveoli, and constitutes the first barrier to both oxygen and pathogens as they progress toward blood circulation. Despite decades of study, the behavior of the pulmonary surfactant at the molecular scale is poorly understood, which hinders the development of effective surfactant replacement therapies, useful in the treatment of several lung-related diseases. In this work, we combined all-atom molecular dynamics simulations, Langmuir trough measurements, and AFM imaging to study synthetic four-component lipid monolayers designed to model protein-free pulmonary surfactant. We characterized the structural and dynamic properties of the monolayers with a special focus on lateral heterogeneity. Remarkably, simulations reproduce almost quantitatively the experimental data on pressure-area isotherms and the presence of lateral heterogeneities highlighted by AFM. Quite surprisingly, the pressure-area isotherms do not show a plateau region, despite the presence of liquid-condensed nanometer-sized domains at surface pressures larger than 20 mN/m. In the simulations, the liquid-condensed domains were small and transient, but they did not coalesce to yield a separate phase. They were only slightly enriched in DPPC and cholesterol, and their chemical composition remained very similar to the overall composition of the monolayer membrane. Instead, they differed from liquid-expanded regions in terms of membrane thickness (in agreement with AFM data), diffusion rates, as well as acyl chain packing and orientation. We hypothesize that such lateral heterogeneities are crucial for lung surfactant function, as they allow both efficient packing, to achieve low surface tension, and sufficient fluidity, critical for rapid adsorption to the air–liquid interface during the breathing cycle.
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Affiliation(s)
- Juho Liekkinen
- Department of Physics, University of Helsinki, Helsinki, Finland
| | - Berta de Santos Moreno
- National Heart & Lung Institute, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - Riku O Paananen
- Helsinki Eye Lab, Ophthalmology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Ilpo Vattulainen
- Department of Physics, University of Helsinki, Helsinki, Finland.,Computational Physics Laboratory, Tampere University, Tampere, Finland.,MEMPHYS - Centre for Biomembrane Physics, Odense, Denmark
| | - Luca Monticelli
- Molecular Microbiology and Structural Biochemistry (MMSB), UMR 5086 CNRS & University of Lyon, Lyon, France
| | | | - Matti Javanainen
- Computational Physics Laboratory, Tampere University, Tampere, Finland.,Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czechia
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Dupuis JH, Wang S, Song C, Yada RY. The role of disulfide bonds in a Solanum tuberosum saposin-like protein investigated using molecular dynamics. PLoS One 2020; 15:e0237884. [PMID: 32841243 PMCID: PMC7447066 DOI: 10.1371/journal.pone.0237884] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Accepted: 08/04/2020] [Indexed: 01/31/2023] Open
Abstract
The Solanum tuberosum plant specific insert (StPSI) has a defensive role in potato plants, with the requirements of acidic pH and anionic lipids. The StPSI contains a set of three highly conserved disulfide bonds that bridge the protein’s helical domains. Removal of these bonds leads to enhanced membrane interactions. This work examined the effects of their sequential removal, both individually and in combination, using all-atom molecular dynamics to elucidate the role of disulfide linkages in maintaining overall protein tertiary structure. The tertiary structure was found to remain stable at both acidic (active) and neutral (inactive) pH despite the removal of disulfide linkages. The findings include how the dimer structure is stabilized and the impact on secondary structure on a residue-basis as a function of disulfide bond removal. The StPSI possesses an extensive network of inter-monomer hydrophobic interactions and intra-monomer hydrogen bonds, which is likely the key to the stability of the StPSI by stabilizing local secondary structure and the tertiary saposin-fold, leading to a robust association between monomers, regardless of the disulfide bond state. Removal of disulfide bonds did not significantly impact secondary structure, nor lead to quaternary structural changes. Instead, disulfide bond removal induces regions of amino acids with relatively higher or lower variation in secondary structure, relative to when all the disulfide bonds are intact. Although disulfide bonds are not required to preserve overall secondary structure, they may have an important role in maintaining a less plastic structure within plant cells in order to regulate membrane affinity or targeting.
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Affiliation(s)
- John H. Dupuis
- Food, Nutrition, and Health Program, Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Shenlin Wang
- College of Chemistry and Molecular Engineering and Beijing NMR Center, Peking University, Beijing, People's Republic of China
| | - Chen Song
- Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, People’s Republic of China
| | - Rickey Y. Yada
- Food, Nutrition, and Health Program, Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
- * E-mail:
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Liekkinen J, Enkavi G, Javanainen M, Olmeda B, Pérez-Gil J, Vattulainen I. Pulmonary Surfactant Lipid Reorganization Induced by the Adsorption of the Oligomeric Surfactant Protein B Complex. J Mol Biol 2020; 432:3251-3268. [DOI: 10.1016/j.jmb.2020.02.028] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 02/22/2020] [Accepted: 02/24/2020] [Indexed: 12/11/2022]
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