Exploring protein–protein interactions and oligomerization state of pulmonary surfactant protein C (SP-C) through FRET and fluorescence self-quenching
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 a...
| Autores: | , , , , , , |
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| Tipo de recurso: | artículo |
| Fecha de publicación: | 2023 |
| País: | España |
| Institución: | Universidad Complutense de Madrid (UCM) |
| Repositorio: | Docta Complutense |
| Idioma: | inglés |
| OAI Identifier: | oai:docta.ucm.es:20.500.14352/105402 |
| Acceso en línea: | https://hdl.handle.net/20.500.14352/105402 |
| Access Level: | acceso abierto |
| Palabra clave: | 577.112 577.2 FRET Oligomerization state Protein–protein interaction Pulmonary surfactant Self-quenching Surfactant protein C (SP-C) Bioquímica (Química) Biología molecular (Biología) 2302 Bioquímica 2415 Biología Molecular |
| Sumario: | 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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