Cleavage of the glycosylphosphatidylinositol anchor affects the reactivity of thy-1 with antibodies.
Thy-1 protein, a member of the Ig superfamily, is bound to the cell membrane by a glycosylphosphatidylinositol (GPI) anchor. We demonstrate that following anchor cleavage by phospholipase C, the reactivity of the solubilized Thy-1 with several mAbs is lost, and its reactivity with polyclonal anti-Thy-1 Abs is markedly decreased. Hence, solubilized Thy-1 cannot be detected by a range of mAbs. In contrast, enzymatic cleavage of biotinylated Thy-1 yields an intact solubilized protein that can be detected by streptavidin. These results exclude a possible proteolytic degradation of solubilized Thy-1 and suggest that the marked decrease in Thy-1 immunoreactivity following delipidation is due to conformational changes in the Thy-1 protein. We further demonstrate that addition of phospholipase C to preformed Ab-Ag complexes causes dissociation and removal of Thy-1 from the complex, indicating that delipidation of Thy-1 induces a conformational change in Thy-1 that is sufficient to dissociate bound Ab. The possibility should therefore be considered that the GPI anchor affects the conformation of a protein to which it is linked.
Kukulansky
T
T
Department of Human Microbiology, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel.
Abramovitch
S
S
Hollander
N
N
D000818:Animals; D017261:Glycosylphosphatidylinositols / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D012995:Solubility; D018800:Thy-1 Antigens / Q000276:immunology*; D010738:Type C Phospholipases / Q000378:metabolism
D017261:Glycosylphosphatidylinositols; D018800:Thy-1 Antigens; D010738:Type C Phospholipases; D043265:Phosphatidylinositol Diacylglycerol-Lyase