Human disease-causing mutations disrupt an N-C-terminal interaction and channel function of bestrophin 1

J Biol Chem. 2009 Jun 12;284(24):16473-81. doi: 10.1074/jbc.M109.002246. Epub 2009 Apr 16.

Abstract

Mutations in the human bestrophin 1 (hBest1) chloride channel cause Best vitelliform macular dystrophy. Although mutations in its transmembrane domains were found to alter biophysical properties of the channel, the mechanism for disease-causing mutations in its N and C termini remains elusive. We hypothesized that these mutations lead to channel dysfunction through disruption of an N-C-terminal interaction. Here, we present data demonstrating that hBest1 N and C termini indeed interact both in vivo and in vitro. In addition, using a spectrum-based fluorescence resonance energy transfer method, we showed that functional hBest1 channels in the plasma membrane were multimers. Disease-causing mutations in the N terminus (R19C, R25C, and K30C) and the C terminus (G299E, D301N, and D312N) caused channel dysfunction and disruption of the N-C interaction. Consistent with the functional and biochemical results, mutants D301N and D312N clearly reduced fluorescence resonance energy transfer signal, indicating that the N-C interaction was indeed perturbed. These results suggest that hBest1 functions as a multimer in the plasma membrane, and disruption of the N-C interaction by mutations leads to hBest1 channel dysfunction.

Publication types

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

MeSH terms

  • Bestrophins
  • Cell Line
  • Cell Membrane / physiology
  • Chloride Channels / chemistry
  • Chloride Channels / genetics*
  • Chloride Channels / metabolism*
  • Eye Proteins / chemistry
  • Eye Proteins / genetics*
  • Eye Proteins / metabolism*
  • Fluorescence Resonance Energy Transfer
  • Humans
  • Kidney / cytology
  • Macular Degeneration / genetics*
  • Macular Degeneration / metabolism*
  • Macular Degeneration / physiopathology
  • Membrane Potentials / physiology
  • Patch-Clamp Techniques
  • Point Mutation
  • Protein Structure, Tertiary
  • Protein Subunits / chemistry
  • Protein Subunits / genetics
  • Protein Subunits / metabolism
  • Structure-Activity Relationship

Substances

  • BEST1 protein, human
  • Bestrophins
  • Chloride Channels
  • Eye Proteins
  • Protein Subunits