In vivo identification and manipulation of the Ca2+ selectivity filter in the Drosophila transient receptor potential channel

J Neurosci. 2007 Jan 17;27(3):604-15. doi: 10.1523/JNEUROSCI.4099-06.2007.

Abstract

Null mutations in the transient receptor potential (trp) gene eliminate the major, Ca2+-selective component of the light-sensitive conductance in Drosophila photoreceptors. Although it is the prototypical member of the TRP ion channel superfamily, conclusive evidence that TRP is a pore-forming channel subunit in vivo is lacking. We show here that mutating a specific acidic residue (Asp621) in the putative pore virtually eliminated Ca2+ permeation in vivo and altered other biophysical properties of the native TRP conductance. The results identify Asp621 as a critical residue of the TRP Ca2+ selectivity filter, provide the first rigorous demonstration that a TRP protein is a pore-forming subunit in any native system, and point to the likely location of the pore in mammalian canonical TRP channels. The specific elimination of Ca2+ permeation in TRP also provided a unique opportunity to address the roles of Ca2+ influx in vivo. We found that Asp621 mutations profoundly affected several key aspects of the light response and caused light-dependent retinal degeneration.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Animals, Genetically Modified
  • Aspartic Acid / genetics
  • Calcium / metabolism*
  • Calcium Channels / genetics
  • Calcium Channels / metabolism
  • Drosophila Proteins / biosynthesis*
  • Drosophila Proteins / genetics
  • Drosophila melanogaster
  • Molecular Sequence Data
  • Mutation
  • Photoreceptor Cells, Invertebrate / physiology
  • Retinal Degeneration / genetics
  • Retinal Degeneration / metabolism
  • Transient Receptor Potential Channels / biosynthesis
  • Transient Receptor Potential Channels / genetics*
  • Transient Receptor Potential Channels / physiology*

Substances

  • Calcium Channels
  • Drosophila Proteins
  • Transient Receptor Potential Channels
  • Aspartic Acid
  • Calcium