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.[1]References
- Novel Ca2+ channels underlying transduction in Drosophila photoreceptors: implications for phosphoinositide-mediated Ca2+ mobilization. Hardie, R.C., Minke, B. Trends Neurosci. (1993) [Pubmed]
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