Novel Ca2+ channels underlying transduction in Drosophila photoreceptors: implications for phosphoinositide-mediated Ca2+ mobilization.
Drosophila photoreceptors are excellent models for studies of the ubiquitous phosphoinositide signalling cascade. Recent studies suggest that light-induced phosphoinositide hydrolysis in Drosophila leads to the activation of two classes of channels. One is selective for Ca2+ and absent in the transient receptor potential mutant trp. The trp gene product, which shows some structural similarity to vertebrate voltage-gated Ca2+ channels, may thus define a novel family of second-messenger-operated Ca2+ channels generally responsible for the widespread but poorly understood phenomenon of phosphoinositide-mediated Ca2+ entry. The other channel is a non-selective cation channel that requires Ca2+ for activation. As well as being a major charge carrier for the light-induced current, Ca2+ influx via the trp-dependent channels appears to be required for refilling Ca2+ stores sensitive to inositol 1,4,5-trisphosphate and for feedback regulation (light adaptation) of the transduction cascade.
Hardie
R C
RC
Dept of Zoology, University of Cambridge, UK.
Minke
B
B
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology*; D004330:Drosophila / Q000502:physiology*; D010716:Phosphatidylinositols / Q000502:physiology*; D017956:Photoreceptor Cells, Invertebrate / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*
D015220:Calcium Channels; D010716:Phosphatidylinositols; D002118:Calcium