Molecular events initiating exit of a copper-transporting ATPase ATP7B from the trans-Golgi network

J Biol Chem. 2012 Oct 19;287(43):36041-50. doi: 10.1074/jbc.M112.370403. Epub 2012 Aug 16.

Abstract

The copper-transporting ATPase ATP7B has a dual intracellular localization: the trans-Golgi network (TGN) and cytosolic vesicles. Changes in copper levels, kinase-mediated phosphorylation, and mutations associated with Wilson disease alter the steady-state distribution of ATP7B between these compartments. To identify a primary molecular event that triggers ATP7B exit from the TGN, we characterized the folding, activity, and trafficking of the ATP7B variants with mutations within the regulatory N-terminal domain (N-ATP7B). We found that structural changes disrupting the inter-domain contacts facilitate ATP7B exit from the TGN. Mutating Ser-340/341 in the N-ATP7B individually or together to Ala, Gly, Thr, or Asp produced active protein and shifted the steady-state localization of ATP7B to vesicles, independently of copper levels. The Ser340/341G mutant had a lower kinase-mediated phosphorylation under basal conditions and no copper-dependent phosphorylation. Thus, negative charges introduced by copper-dependent phosphorylation are not obligatory for ATP7B trafficking from the TGN. The Ser340/341A mutation did not alter the overall fold of N-ATP7B, but significantly decreased interactions with the nucleotide-binding domain, mimicking consequences of copper binding to N-ATP7B. We propose that structural changes that specifically alter the inter-domain contacts initiate exit of ATP7B from the TGN, whereas increased phosphorylation may be needed to maintain an open interface between the domains.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / genetics
  • Adenosine Triphosphatases / metabolism*
  • Amino Acid Substitution
  • Cation Transport Proteins / genetics
  • Cation Transport Proteins / metabolism*
  • Copper-Transporting ATPases
  • HEK293 Cells
  • Hepatolenticular Degeneration / genetics
  • Hepatolenticular Degeneration / metabolism
  • Humans
  • Mutation, Missense
  • Phosphorylation / physiology
  • Protein Structure, Tertiary
  • Protein Transport / physiology
  • Transport Vesicles / genetics
  • Transport Vesicles / metabolism*
  • trans-Golgi Network / genetics
  • trans-Golgi Network / metabolism*

Substances

  • Cation Transport Proteins
  • Adenosine Triphosphatases
  • ATP7B protein, human
  • Copper-Transporting ATPases