Localization of signaling complexes with channels and clustered receptors. (a) A cartoon representation of neuronal receptor clustering and regulation. PDZ domain–containing proteins are responsible for clustering several types of glutamate receptors (see text for details). Evidence is now also accumulating in support of the regulation of receptor activity through targeted kinases and phosphatases, as illustrated by the interaction of the AKAP yotiao with PKA, PP1, and the NR1 subunit of the NMDA receptor. (b) The targeting and clustering of receptors and channels with intracellular signaling molecules responsible for phototransduction in Drosophila eye. The PDZ domains of InaD target PLC-β, PKC, and calmodulin to the membrane and cluster the TRP channels with these signaling molecules. Homomeric and heteromeric InaD interactions facilitate the formation of this transducisome complex.