No abstract

Wilson disease protein, ATP7B maintains copper homeostasis in the liver. ATP7B traffics from trans-Golgi network to endolysosomes to export excess copper. Regulation of ATP7B trafficking to and fro endolysosomes is not well understood. We investigated the fate of ATP7B, post-copper export. At high copper ATP7B traffics primarily to acidic, active hydrolase (Cathepsin-B) positive endolysosomes and upon subsequent copper chelation, returns to trans-Golgi network. At high copper, ATP7B co-localizes with endolysosomal markers and with core member of retromer complex, VPS35. Knocking down VPS35 did not abrogate copper export function of ATP7B or its copper-responsive anterograde trafficking to vesicles; rather upon subsequent copper chelation, ATP7B failed to relocalize to TGN that was rescued by overexpressing wtVPS35. Overexpressing mutants of retromer complex associated proteins, Rab7 and COMMD1 yielded similar non-recycling phenotype of ATP7B. At high copper, VPS35 and ATP7B are juxtaposed on the same endolysosome and form a large complex that is stabilized by in-vivo photoamino acid labeling and UV-crosslinking. We demonstrate that retromer regulates endolysosome to TGN trafficking of copper transporter ATP7B and it is dependent upon intracellular copper.

No abstract

No abstract