Wilson's disease results from impaired copper excretion due to ATP7B mutation. In which organelle does ATP7B normally incorporate copper into ceruloplasmin and direct excess copper into bile?

• A Endoplasmic reticulum
• B Lysosomes
• C Mitochondria
• D Golgi apparatus ✓

Explanation

ATP7B is a copper-transporting P-type ATPase located primarily in the trans-Golgi network of hepatocytes. In the Golgi, it pumps copper into the lumen for incorporation into apo-ceruloplasmin (converting it to holo-ceruloplasmin) and for packaging into vesicles that fuse with the canalicular membrane to excrete copper into bile. When copper load is excessive, ATP7B translocates to a pericanalicular position to enhance biliary copper excretion. In Wilson's disease, defective ATP7B prevents biliary excretion; copper accumulates in hepatocytes, overflows into plasma (as non-ceruloplasmin-bound free copper), and deposits in the brain (basal ganglia), cornea (Kayser-Fleischer rings), and kidneys.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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