Mannose-6-Phosphate Receptor (M6PR)

M6PR is a receptor for mannose-6-phosphate groups on lysosomal enzymes. The receptor forms a homodimer or homotetramer for intracellular targeting of lysosomal enzymes and export of newly synthesized lysosomal enzymes into the cell secretions. The receptor is an integral membrane protein which localizes to the trans-Golgi reticulum, endosomes, and the plasma membrane. Two distinct mannose 6-phosphate receptors have been identified: one is cation-independent and has an apparent molecular weight of 215,000. The second, the cation-dependent mannose 6-phosphate receptor, or small mannose 6-phosphate receptor, has an apparent molecular weight of only 46,000 and requires divalent cations for high-affinity binding with its ligand.