The cation-independent mannose-6-phosphate/insulin-like growth factor II receptor has been observed to bind to soluble forms of glycosyl-phosphatidylinositol-linked molecules, one of mammalian origin (rat Thy-1) and two of protozoan origins. Of the two phosphate groups found on the soluble forms of the protozoan glycosyl-phosphatidylinositol-linked molecules: (i) the internal mannose-6-phosphate diester (which forms a part of the ethanolamine bridge) and (ii) the inositol-1,2 cyclic phosphate group (which arises after cleavage of the membrane associated form with phosphatidylinositol-specific phospholipase C), only the former appears to be recognized by the mannose-6-phosphate/insulin-like growth factor II receptor, as mild acid hydrolysis which destroys the latter has been observed not to affect the receptor binding site.
Green, P. J., Ferguson, M. A. J., Robinson, P. J., & Feizi, T. (1995). The cation-independent mannose-6-phosphate receptor binds to soluble GPI-linked proteins via mannose-6-phosphate. FEBS Letters, 360(1), 34-38. https://doi.org/10.1016/0014-5793(95)00050-J