Differential effects of human SP-A1 and SP-A2 variants on phospholipid monolayers containing surfactant protein B.
Surfactant protein A (SP-A), the most abundant protein in the lung alveolar surface, has multiple activities, including surfactant-related functions. SP-A is required for the formation of tubular myelin and the lung surface film. The human SP-A locus consists of two functional SP-A genes, SP-A1 and SP-A2, with a number of alleles characterized for each gene. We have found that the human in vitro expressed variants, SP-A1 (6A(2)) and SP-A2 (1A(0)), and the coexpressed SP-A1/SP-A2 (6A(2)/1A(0)) protein have a differential influence on the organization of phospholipid monolayers containing surfactant protein B (SP-B). Lipid films containing SP-B and SP-A2 (1A(0)) showed surface features similar to those observed in lipid films with SP-B and native human SP-A. Fluorescence images revealed the presence of characteristic fluorescent probe-excluding clusters coexisting with the traditional lipid liquid-expanded and liquid-condensed phase. Images of the films containing SP-B and SP-A1 (6A(2)) showed different distribution of the proteins. The morphology of lipid films containing SP-B and the coexpressed SP-A1/SP-A2 (6A(2)/1A(0)) combined features of the individual films containing the SP-A1 or SP-A2 variant. The results indicate that human SP-A1 and SP-A2 variants exhibit differential effects on characteristics of phospholipid monolayers containing SP-B. This may differentially impact surface film activity.
Wang
Guirong
G
Department of Cellular and Molecular Physiology, H166, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA.
Taneva
Svetla
S
Keough
Kevin M W
KM
Floros
Joanna
J
D000818:Animals; D006801:Humans; D008051:Lipid Bilayers / Q000737:chemistry*; D008560:Membrane Fluidity; D044367:Phase Transition; D010743:Phospholipids / Q000737:chemistry*; D020033:Protein Isoforms / Q000737:chemistry / Q000648:ultrastructure; D037662:Pulmonary Surfactant-Associated Protein A / Q000737:chemistry* / Q000648:ultrastructure*; D013045:Species Specificity; D013500:Surface Tension; D013552:Swine
D008051:Lipid Bilayers; D010743:Phospholipids; D020033:Protein Isoforms; D037662:Pulmonary Surfactant-Associated Protein A; C445842:SFTPA1 protein, human; C445843:SFTPA2 protein, human