I-cell disease is a particularly severe form of lysosomal storage disease. Multiple enzymes are lacking in the lysosome and the organelle becomes stuffed with nondegraded material and therefore generates a so-called inclusion body. I-cell disease is inherited; it is caused by a single gene defect in the N-acetylglucosamine phosphotransferase that is required for the formation of mannose 6-phosphate (M6P) residues on lysosomal enzymes in the cis-Golgi. This enzyme recognizes soluble lysosomal enzymes as a class and hence a defect in this protein affects the targeting of a large number of proteins. What other defect(s) would cause the same phenotype? (Select all correct answers may be more than one)
A) a defect in clathrin function
B) a defect in the mannose 6-phosphate receptor
C) a defect in the phosphodiesterase that removes the GlcNAc group that initially covers the phosphate group on mannose 6-phosphate.
D) a defect in KDEL receptor