Binding specificity of lung surfactant protein SP-D for glucosylceramide

The specificities of the binding of lung surfactant protein SP-D to glycolipids were examined using 125I-labeled SP-D as a probe. When the binding study was performed on TLC plates, SP-D bound exclusively to GlcCer, whereas it failed to bind to GalCer, GM1, GM2, asialo-GM1, asialo-GM2, sulfatide, Forssman antigen, ceramide dihexoside, ceramide trihexoside, globoside, paragloboside or ceramide. Excess native SP-D competed with 125I-SP-D for the binding to GlcCer. Antibody to rat SP-D inhibited 125I-SP-D binding to GlcCer. Ca2+ was absolutely required for the binding of SP-D to GlcCer; Mg2+ failed to substitute for Ca2+. SP-D bound to ceramide monohexoside in glycolipids isolated from rat lung and bronchoalveolar lavage fluids of rats.