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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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Domains of the TF protein important in regulating its own palmitoylation. Virology 2019; 531:31-39. [PMID: 30852269 DOI: 10.1016/j.virol.2019.02.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 02/21/2019] [Accepted: 02/22/2019] [Indexed: 11/23/2022]
Abstract
Sindbis virus particles contain the viral proteins capsid, E1 and E2, and low levels of a small membrane protein called TF. TF is produced during a (-1) programmed ribosomal frameshifting event during the translation of the structural polyprotein. TF from Sindbis virus-infected cells is present in two palmitoylated states, basal and maximal; unpalmitoylated TF is not detectable. Mutagenesis studies demonstrated that without palmitoylation, TF is not incorporated into released virions, suggesting palmitoylation of TF is a regulated step in virus assembly. In this work, we identified Domains within the TF protein that regulate its palmitoylation state. Mutations and insertions in Domain III, a region proposed to be in the cytoplasmic loop of TF, increase levels of unpalmitoylated TF found during an infection but still unpalmitoylated TF was not incorporated into virions. Mutations in Domain IV, the TF unique region, are likely to impact the balance between basal and maximal palmitoylation.
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Rodenburg RNP, Snijder J, van de Waterbeemd M, Schouten A, Granneman J, Heck AJR, Gros P. Stochastic palmitoylation of accessible cysteines in membrane proteins revealed by native mass spectrometry. Nat Commun 2017; 8:1280. [PMID: 29097667 PMCID: PMC5668376 DOI: 10.1038/s41467-017-01461-z] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 09/19/2017] [Indexed: 01/09/2023] Open
Abstract
Palmitoylation affects membrane partitioning, trafficking and activities of membrane proteins. However, how specificity of palmitoylation and multiple palmitoylations in membrane proteins are determined is not well understood. Here, we profile palmitoylation states of three human claudins, human CD20 and cysteine-engineered prokaryotic KcsA and bacteriorhodopsin by native mass spectrometry. Cysteine scanning of claudin-3, KcsA, and bacteriorhodopsin shows that palmitoylation is independent of a sequence motif. Palmitoylations are observed for cysteines exposed on the protein surface and situated up to 8 Å into the inner leaflet of the membrane. Palmitoylation on multiple sites in claudin-3 and CD20 occurs stochastically, giving rise to a distribution of palmitoylated membrane-protein isoforms. Non-native sites in claudin-3 indicate that membrane-protein function imposed evolutionary restraints on native palmitoylation sites. These results suggest a generic, stochastic membrane-protein palmitoylation process that is determined by the accessibility of palmitoyl-acyl transferases to cysteines on membrane-embedded proteins, and not by a preferred substrate-sequence motif.
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Affiliation(s)
- Remco N P Rodenburg
- Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Dept. of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584CH, Utrecht, The Netherlands
| | - Joost Snijder
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Padualaan 8, 3584CH, Utrecht, The Netherlands
| | - Michiel van de Waterbeemd
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Padualaan 8, 3584CH, Utrecht, The Netherlands
| | - Arie Schouten
- Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Dept. of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584CH, Utrecht, The Netherlands
| | - Joke Granneman
- Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Dept. of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584CH, Utrecht, The Netherlands
| | - Albert J R Heck
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Padualaan 8, 3584CH, Utrecht, The Netherlands.
| | - Piet Gros
- Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Dept. of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584CH, Utrecht, The Netherlands.
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Rausch F, Schicht M, Paulsen F, Ngueya I, Bräuer L, Brandt W. "SP-G", a putative new surfactant protein--tissue localization and 3D structure. PLoS One 2012; 7:e47789. [PMID: 23094088 PMCID: PMC3475697 DOI: 10.1371/journal.pone.0047789] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Accepted: 09/17/2012] [Indexed: 12/30/2022] Open
Abstract
Surfactant proteins (SP) are well known from human lung. These proteins assist the formation of a monolayer of surface-active phospholipids at the liquid-air interface of the alveolar lining, play a major role in lowering the surface tension of interfaces, and have functions in innate and adaptive immune defense. During recent years it became obvious that SPs are also part of other tissues and fluids such as tear fluid, gingiva, saliva, the nasolacrimal system, and kidney. Recently, a putative new surfactant protein (SFTA2 or SP-G) was identified, which has no sequence or structural identity to the already know surfactant proteins. In this work, computational chemistry and molecular-biological methods were combined to localize and characterize SP-G. With the help of a protein structure model, specific antibodies were obtained which allowed the detection of SP-G not only on mRNA but also on protein level. The localization of this protein in different human tissues, sequence based prediction tools for posttranslational modifications and molecular dynamic simulations reveal that SP-G has physicochemical properties similar to the already known surfactant proteins B and C. This includes also the possibility of interactions with lipid systems and with that, a potential surface-regulatory feature of SP-G. In conclusion, the results indicate SP-G as a new surfactant protein which represents an until now unknown surfactant protein class.
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Affiliation(s)
- Felix Rausch
- Department of Bioorganic Chemistry, Leibniz Institute of Plant Biochemistry, Halle, Germany
| | - Martin Schicht
- Institute of Anatomy, Department II, Friedrich Alexander University Erlangen-Nuremberg, Erlangen, Germany
| | - Friedrich Paulsen
- Institute of Anatomy, Department II, Friedrich Alexander University Erlangen-Nuremberg, Erlangen, Germany
| | - Ivan Ngueya
- Institute of Anatomy, Department II, Friedrich Alexander University Erlangen-Nuremberg, Erlangen, Germany
| | - Lars Bräuer
- Institute of Anatomy, Department II, Friedrich Alexander University Erlangen-Nuremberg, Erlangen, Germany
| | - Wolfgang Brandt
- Department of Bioorganic Chemistry, Leibniz Institute of Plant Biochemistry, Halle, Germany
- * E-mail:
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Young FB, Butland SL, Sanders SS, Sutton LM, Hayden MR. Putting proteins in their place: Palmitoylation in Huntington disease and other neuropsychiatric diseases. Prog Neurobiol 2012; 97:220-38. [DOI: 10.1016/j.pneurobio.2011.11.002] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2011] [Revised: 11/01/2011] [Accepted: 11/08/2011] [Indexed: 01/02/2023]
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Protein palmitoylation and subcellular trafficking. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2981-94. [DOI: 10.1016/j.bbamem.2011.07.009] [Citation(s) in RCA: 257] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Revised: 07/06/2011] [Accepted: 07/12/2011] [Indexed: 02/07/2023]
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Beers MF, Hawkins A, Shuman H, Zhao M, Newitt JL, Maguire JA, Ding W, Mulugeta S. A novel conserved targeting motif found in ABCA transporters mediates trafficking to early post-Golgi compartments. J Lipid Res 2011; 52:1471-82. [PMID: 21586796 DOI: 10.1194/jlr.m013284] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The ATP binding cassette, class A (ABCA) proteins are homologous polytopic transmembrane transporters that function as lipid pumps at distinct subcellular sites in a variety of cells. Located within the N terminus of these transporters, there exists a highly conserved xLxxKN motif of unknown function. To define its role, human ABCA3 was employed as a primary model representing ABCA transporters, while mouse ABCA1 was utilized to support major findings. Transfection studies showed colocalization of both transporters with surfactant protein C (SP-C), a marker peptide for successful protein targeting to lysosomal-like organelles. In contrast, alanine mutation of xLxxKN resulted in endoplasmic reticulum retention. As proof of principle, swapping xLxxKN for the known lysosomal targeting motif of SP-C resulted in post-Golgi targeting of the SP-C chimera. However, these products failed to reach their terminal processing compartments, suggesting that the xLxxKN motif only serves as a Golgi exit signal. We propose a model whereby an N-terminal signal sequence, xLxxKN, directs ABCA transporters to a post-Golgi vesicular sorting station where additional signals may be required for selective delivery of individual transporters to final subcellular destinations.
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Affiliation(s)
- Michael F Beers
- Department of Medicine, Pulmonary, Allergy, and Critical Care Division, University of Pennsylvania, Philadelphia, PA, USA
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Gibbings DJ, Marcet-Palacios M, Sekar Y, Ng MCY, Befus AD. CD8 alpha is expressed by human monocytes and enhances Fc gamma R-dependent responses. BMC Immunol 2007; 8:12. [PMID: 17678538 PMCID: PMC2000912 DOI: 10.1186/1471-2172-8-12] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2007] [Accepted: 08/01/2007] [Indexed: 01/06/2023] Open
Abstract
Background CD8α enhances the responses of antigen-specific CTL activated through TCR through binding MHC class I, favoring lipid raft partitioning of TCR, and inducing intracellular signaling. CD8α is also found on dendritic cells and rat macrophages, but whether CD8α enhances responses of a partner receptor, like TCR, to activate these cells is not known. TCR and FcR, use analogous or occasionally interchangeable signaling mechanisms suggesting the possibility that CD8α co-activates FcR responses. Interestingly, CD8α+ monocytes are often associated with rat models of disease involving immune-complex deposition and FcR-mediated pathology, such as arthritis, glomerulonephritis, ischaemia, and tumors. While rat macrophages have been shown to express CD8α evidence for CD8α expression by mouse or human monocytes or macrophages was incomplete. Results We detected CD8α, but not CD8β on human monocytes and the monocytic cell line THP-1 by flow cytometry. Reactivity of anti-CD8α mAb with monocytes is at least partly independent of FcR as anti-CD8α mAb detect CD8α by western blot and inhibit binding of MHC class I tetramers. CD8α mRNA is also found in monocytes and THP-1 suggesting CD8α is synthesized by monocytes and not acquired from other CD8α+ cell types. Interestingly, CD8α from monocytes and blood T cells presented distinguishable patterns by 2-D electrophoresis. Anti-CD8α mAb alone did not activate monocyte TNF release. In comparison, TNF release by human monocytes stimulated in a FcR-dependent manner with immune-complexes was enhanced by inclusion of anti-CD8α mAb in immune-complexes. Conclusion Human monocytes express CD8α. Co-engagement of CD8α and FcR enhances monocyte TNF release, suggesting FcR may be a novel partner receptor for CD8α on innate immune cells.
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Affiliation(s)
- Derrick J Gibbings
- Pulmonary Research Group, Division of Pulmonary Medicine, Department of Medicine, University of Alberta, Canada
| | - Marcelo Marcet-Palacios
- Pulmonary Research Group, Division of Pulmonary Medicine, Department of Medicine, University of Alberta, Canada
| | - Yokananth Sekar
- Pulmonary Research Group, Division of Pulmonary Medicine, Department of Medicine, University of Alberta, Canada
| | - Marcus CY Ng
- Pulmonary Research Group, Division of Pulmonary Medicine, Department of Medicine, University of Alberta, Canada
| | - A Dean Befus
- Pulmonary Research Group, Division of Pulmonary Medicine, Department of Medicine, University of Alberta, Canada
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Ashbourne Excoffon KJD, Moninger T, Zabner J. The coxsackie B virus and adenovirus receptor resides in a distinct membrane microdomain. J Virol 2003; 77:2559-67. [PMID: 12551994 PMCID: PMC141093 DOI: 10.1128/jvi.77.4.2559-2567.2003] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The coxsackie B virus and adenovirus receptor (CAR) is a member of the immunoglobulin superfamily. In addition to activity as a viral receptor, it may play a role in cellular adhesion. We asked what determines the cell membrane microdomain of CAR. We found that CAR is localized to a novel lipid-rich microdomain similar to that of the low-density lipoprotein receptor (LDLR) but distinct from that of a CAR variant that exhibited traditional lipid raft localization via fusion to a glycosylphosphatidylinositol (GPI) tail. The cytoplasmic tail determines its membrane localization, since deletion of this domain resulted in mislocalization. Results indicate that CAR, CAR-LDLR, and LDLR reside in a novel lipid raft that is distinct from caveolin-1-containing caveolae and GPI-linked proteins. Residence in a lipid-rich domain provides a mechanism that allows CAR to interact with other cell adhesion proteins and yet function as an adenovirus receptor.
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