Calmodulin regulation of calcium stores in phototransduction of Drosophila.
Phototransduction in Drosophila occurs through the ubiquitous phosphoinositide-mediated signal transduction system. Major unresolved questions in this pathway are the identity and role of the internal calcium stores in light excitation and the mechanism underlying regulation of Ca2+ release from internal stores. Treatment of Drosophila photoreceptors with ryanodine and caffeine disrupted the current induced by light, whereas subsequent application of calcium-calmodulin (Ca-CaM) rescued the inactivated photoresponse. In calcium-deprived wild-type Drosophila and in calmodulin-deficient transgenic flies, the current induced by light was disrupted by a specific inhibitor of Ca-CaM. Furthermore, inhibition of Ca-CaM revealed light-induced release of calcium from intracellular stores. It appears that functional ryanodine-sensitive stores are essential for the photoresponse. Moreover, calcium release from these stores appears to be a component of Drosophila phototransduction, and Ca-CaM regulates this process.
Arnon
A
A
Department of Physiology and the Kühne Minerva Center for Studies of Visual Transduction, Hebrew University, Jerusalem 91120, Israel.
Cook
B
B
Montell
C
C
Selinger
Z
Z
Minke
B
B
D000818:Animals; D030801:Animals, Genetically Modified; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002147:Calmodulin / Q000378:metabolism*; D004330:Drosophila / Q000235:genetics / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D008027:Light; D018408:Patch-Clamp Techniques; D017956:Photoreceptor Cells, Invertebrate / Q000187:drug effects / Q000378:metabolism*; D012433:Ryanodine / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D019284:Thapsigargin / Q000494:pharmacology
D002147:Calmodulin; D004791:Enzyme Inhibitors; D012433:Ryanodine; D002110:Caffeine; D019284:Thapsigargin; D000252:Calcium-Transporting ATPases; D002118:Calcium