Inhibition of glycosyl-phosphatidylinositol anchor formation by mannosamine

Many eucaryotic cell surface proteins are anchored to the plasma membrane via a glycosyl-phosphatidylinositol (GPI), of which the core region is highly conserved from protozoa to mammalian cells. Previous studies showed that mannosamine blocked the expression of a recombinant GPI-anchored protein in Madin-Darby canine kidney cells and converted this protein to an unpolarized secretory product. In the present study, we examined the effect of mannosamine on the formation of the glycan portion of the GPI anchor precursors.