Differences in the Alveolar Macrophage Proteome in Transgenic Mice Expressing Human SP-A1 and SP-A2 - Differences in the Alveolar Macrophage Proteome in Transgenic Mice Expressing Human SP-A1 and SP-A2 - Open Access Pub

Surfactant protein A (SP-A) plays a number of roles in lung host defense and innate immunity. There are two human genes, SFTPA1 and SFTPA2, and evidence indicates that the function of SP-A1 and SP-A2 proteins differ in several respects. To investigate the impact of SP-A1 and SP-A2 on the alveolar macrophage (AM) phenotype, we generated humanized transgenic (hTG) mice on the SP-A knockout (KO) background, each expressing human SP-A1 or SP-A2. Using two-dimensional difference gel electrophoresis (2D-DIGE) we studied the AM cellular proteome. We compared mouse lines expressing high levels of SP-A1, high levels of SP-A2, low levels of SP-A1, and low levels of SP-A2, with wild type (WT) and SP-A KO mice. AM from mice expressing high levels of SP-A2 were the most similar to WT mice, particularly for proteins related to actin and the cytoskeleton, as well as proteins regulated by Nrf2. The expression patterns from mouse lines expressing higher levels of the transgenes were almost the inverse of one another – the most highly expressed proteins in SP-A2 exhibited the lowest levels in the SP-A1 mice and vice versa. The mouse lines where each expressed low levels of SP-A1 or SP-A2 transgene had very similar protein expression patterns suggesting that responses to low levels of SP-A are independent of SP-A genotype, whereas the responses to higher amounts of SP-A are genotype-dependent. Together these observations indicate that in vivo exposure to SP-A1 or SP-A2 differentially affects the proteomic expression of AMs, with SP-A2 being more similar to WT. DOI10.14302/issn.2326-0793.jpgr-13-207 Surfactant protein-A (SP-A) is a member of the collectin family with an N-terminal collagen-like domain and a C-terminal carbohydrate recognition domain (CRD) that binds to many macromolecules, pathogens, and allergens 1, 2. Most mammals possess a single SP-A gene, but humans and primates have two functional SP-A genes (SFTPA1 and SFTPA2). The human SP-A monomer is a 35kDa protein of 248 amino acids. In the coding region, the gene-specific differences of SP-A1 and SP-A2 consist of four amino acids 3, 4. SP-A influences host defense function in a variety of ways. It recognizes and binds to pathogen-associated molecular patterns. These interactions are complex and may involve binding sites in addition to the CRD. Direct interaction with pathogens constitutes one aspect of its host defense function, but SP-A also aids in the clearance of particulates, allergens, and debris 5, 6, 7, 8, 9. SP-A also influences the alveolar macrophage (AM) by regulating many cytokines, including