Role of pulmonary surfactant protein Sp-C dimerization on membrane fragmentation: An emergent mechanism involved in lung defense and homeostasis

Surfactant protein C (SP-C) is a protein present in the pulmonary surfactant system that is involved in the biophysical properties of this lipoprotein complex, but it also has a role in lung defense and homeostasis. In this article, we propose that the link between both functions could rely on the ability of SP-C to induce fragmentation of phospholipid membranes and generate small vesicles that serve as support to present different ligands to cells in the lungs. Our results using bimolecular fluorescence complementation and tunable resistive pulse sensing setups suggest that SP-C oligomerization could be the triggering event that causes membrane budding and nanovesiculation. As shown by fluorescence microscopy and flow cytometry, these vesicles are differentially assimilated by alveolar macrophages and alveolar type II cells, indicating distinct roles of these alveoli-resident cells in the processing of the SP-C- induced vesicles and their cargo. These results depict a more accurate picture of the mechanisms of this protein, which could be relevant for the comprehension of pulmonary pathologies and the development of new therapeutic approaches.

Automated summary

This article discusses the dual role of surfactant protein C (SP-C) in the pulmonary surfactant system, both in biophysical properties and lung defense. Results indicate that SP-C oligomerization may trigger membrane budding and nanovesiculation, leading to the presentation of different ligands to lung cells. Vesicles induced by SP-C are differentially assimilated by alveolar macrophages and alveolar type II cells, suggesting distinct roles of these cells in processing the vesicles. These findings provide insights into pulmonary pathologies and potential therapeutic approaches.