The intracellular distal tail of the Na+/H+ exchanger NHE1 is intrinsically disordered: implications for NHE1 trafficking

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  • Ann-Beth Nørholm, LUKKET: 2012 Institut for Lægemiddeldesign og Farm, Denmark
  • Ruth Hendus-Altenburger, Cell and developmental biology, Denmark
  • Gabriel Peder Bjerre, Cell and developmental biology, Denmark
  • Magnus Kjærgaard
  • Stine F Pedersen
  • ,
  • Birthe Brandt Kragelund, Biomolecular Sciences, Denmark
Intrinsic disorder is important for protein regulation, yet its role in regulation of ion transport proteins is essentially uninvestigated. The ubiquitous plasma membrane carrier protein Na(+)/H(+) Exchanger isoform 1 (NHE1) plays pivotal roles in cellular pH and volume homeostasis, and its dysfunction is implicated in several clinically important diseases. This study shows, for the first time for any carrier protein, that the distal part of the C-terminal intracellular tail (the cdt, residues V686-Q815) from human (h) NHE1 is intrinsically disordered. Further, we experimentally demonstrated the presence of a similar region of intrinsic disorder (ID) in NHE1 from the teleost fish Pleuronectes americanus (paNHE1), and bioinformatic analysis suggested ID to be conserved in the NHE1 family. The sequential variation in structure propensity as determined by NMR, but not the amplitude, was largely conserved between the h- and paNHE1cdt. This suggests that both proteins contain molecular recognition features (MoRFs), i.e., local, transiently formed structures within an ID region. The functional relevance of the most conserved MoRF was investigated by introducing a point mutation that significantly disrupted the putative binding feature. When this mutant NHE1 was expressed in full length NHE1 in AP1 cells, it exhibited impaired trafficking to the plasma membrane. This study demonstrated that the distal regulatory domain of NHE1 is intrinsically disordered yet contains conserved regions of transient structure. We suggest that normal NHE1 function depends on a protein recognition element within the ID region that may be linked to NHE1 trafficking via an acidic ER export motif.
Original languageEnglish
JournalBiochemistry
Volume50
Issue17
Pages (from-to)3469-80
Number of pages12
ISSN0006-2960
DOIs
Publication statusPublished - 3 May 2011
Externally publishedYes

    Research areas

  • Amino Acid Motifs, Animals, Cation Transport Proteins, Cell Line, Cell Membrane, Computational Biology, Conserved Sequence, Fish Proteins, Flounder, Glycosylation, Humans, Molecular Sequence Data, Mutation, Nuclear Magnetic Resonance, Biomolecular, Protein Structure, Secondary, Protein Transport, Scattering, Small Angle, Sequence Alignment, Sodium-Hydrogen Antiporter, Species Specificity, X-Ray Diffraction

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