TRP TRAPPED IN FLY SIGNALING WEB

In the Drosophila eye, photoactivation of rhodopsin leads to the openi ng of the light-sensitive cation influx channels TRP and TRPL. This re sponse is extremely rapid and results in depolarization of the photore ceptor cells followed by Ca2+-mediated feedback regulation of the visu al signaling cascade, The mechanisms that facilitate the rapid kinetic s of activation and feedback regulation are poorly understood. However , the recent discovery that most of the proteins that function in fly phototransduction associate into a supramolecular complex permits a re -evaluation of the mechanisms underlying the activation and regulation of the cascade. The central player in the signaling complex is INAD, a protein with five protein-interaction motifs known as PDZ domains. T he INAD complex does not appear to be a particle, but a massive signal ing web composed of an INAD polymer with which some of the target prot eins associate through complex multivalent interactions.