The LDL is inside of the cell in an intracellular vesicle
The CURL and LDL containing vesicle fuse
The vesicle containing the LDL then fuses with a vesicle call CURL. There is a low pH (pH 5) inside of the CURL because a H+ion ATPase (proton pump) causes protons to enter into the vesicle against a concentration gradient.
A Low pH causes the receptor to separate from the ligand because the low pH causes a change in their conformations.
A primary lysosome fuses with the LDL containing endocytotic vesicle and the receptors are recycled back to the plasma membrane by exocytosis.
lysosomal acid hydrolyases degrade the LDL