In vivo identification and manipulation of the Ca2+ selectivity filter in the Drosophila transient receptor potential channel.
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.
Liu
Che H
CH
Department of Physiology Development and Neuroscience, Cambridge University, Cambridge CB2 3DY, United Kingdom.
Wang
Tao
T
Postma
Marten
M
Obukhov
Alexander G
AG
Montell
Craig
C
Hardie
Roger C
RC
D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D001224:Aspartic Acid / Q000235:genetics; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000096:biosynthesis* / Q000235:genetics; D004331:Drosophila melanogaster; D008969:Molecular Sequence Data; D009154:Mutation; D017956:Photoreceptor Cells, Invertebrate / Q000502:physiology; D012162:Retinal Degeneration / Q000235:genetics / Q000378:metabolism; D050051:Transient Receptor Potential Channels / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology*
D015220:Calcium Channels; D029721:Drosophila Proteins; D050051:Transient Receptor Potential Channels; D001224:Aspartic Acid; D002118:Calcium