Fig. 6. INAD coordinates the Drosophila melanogaster phototransduction cascade. (A) Domain structure of INAD; arrows indicate putative protein-protein interactions. (B) Diagram of the Drosophila phototransduction cascade. The full photoreceptor cell is at top left. At top right, a section of the cell is expanded to show the stacking of rhabdomeres. Below, a schematic representation of the signaling pathway coordinated by INAD. INAD is indicated by five yellow PDZ domains connected by a black line. Abbreviations for proteins that form the phototransduction signaling cascade are as follows: TRP/TRPL, transient-receptor-potential-type Ca²⁺ channels; G_q, the G subunit of the heterotrimeric G protein involved in the Drosophila phototransduction pathway; PLC, phospholipase Cß; PKC, eye-specific protein kinase C; CaM, calmodulin.