Surfactant Protein A (SP-A)1 And SP-A2 Differentially Affect F-Actin Levels in The Alveolar Macrophage

Abstract

Surfactant protein A (SP-A) is an important molecule playing multiple roles in lung innate immunity. SP-A interacts with the alveolar macrophage (AM) and regulates several of its functions. There is increasing evidence that SP-A regulates the AM actin cytoskeleton. Here we used AM from SP-A humanized transgenic mice where each expresses a different human SP-A variant to investigate the impact human SP-A1 and SP-A2 have on F-actin. We found that SP-A2 AM compared to SP-A1 AM: a) exhibit a different pattern of F-actin fluorescence after staining with Alexa Fluor 488 phalloidin and reduced F-actin levels as assessed by measurements of fluorescence per pixel; b) show a lower F-actin to G-actin (F: G) ratio as assessed by Western blot analysis of different cell fractions; and c) have reduced levels of Arp3 protein, as assessed by mining existing relevant proteomics data. Arp3 regulates branched-actin polymerization. These together indicate a differential role of SP-A genetics on the actin cytoskeleton.