The Q-rich/PST domain of the AHR regulates both ligand-induced nuclear transport and nucleocytoplasmic shuttling

Sci Rep. 2016 Aug 18:6:32009. doi: 10.1038/srep32009.

Abstract

The aryl hydrocarbon receptor (AHR) shuttles continuously between cytoplasm and nucleus, unless ligand-binding triggers association with the AHR nuclear translocator (ARNT) and subsequent binding to cognate DNA motifs. We have now identified Val 647 as mandatory residue for export from the nucleus and AHR-function. This residue prevents inactivation of the receptor as a consequence of nuclear sequestration via constitutive import. Concomitantly mutants lacking this residue are exclusively localised in the nucleus. Although ligands accelerate nuclear import transiently, stable nuclear transition depends on a motif adjacent to Val 647 that comprises residues 650-661. Together, this defined region within the Q-rich domain regulates intracellular trafficking of the AHR in context of both nucleocytoplasmic shuttling and receptor activation. Nuclear export therefore depends on the previously characterised N-terminal NES and the newly identified motif that includes V647. Nucleocytoplasmic distribution of full-length human AHR is further affected by a section of the PST domain that shows sequence similarities with nuclear export signals. In concert, these motifs maintain a predominant cytoplasmic compartmentalisation, receptive for ligand binding.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Basic Helix-Loop-Helix Transcription Factors / metabolism*
  • Cell Line
  • Cell Nucleus / metabolism*
  • Cytoplasm / metabolism*
  • HEK293 Cells
  • Humans
  • Ligands
  • Nuclear Export Signals
  • Protein Domains
  • Protein Transport*
  • Receptors, Aryl Hydrocarbon / metabolism*

Substances

  • AHR protein, human
  • Basic Helix-Loop-Helix Transcription Factors
  • Ligands
  • Nuclear Export Signals
  • Receptors, Aryl Hydrocarbon