A multivalent PDZ-domain protein assembles signalling complexes in a G- protein-coupled cascade

Abstract

How are signalling molecules organized into different pathways within the same cell? In Drosophila, the inaD gene encodes a protein consisting of five PDZ domains which serves as a scaffold to assemble different components of the phototransduction cascade, including the principal light-activated lon channels the effector phosphollpase C-β and protein kinase C. Null inaD mutants have a dramatically reorganized subcellular distribution of signalling molecules, and n total loss of transduction complexes. Also, mutants defective in a single PDZ domain produce signalling complexes that lack the target protein and display corresponding defects in their physiology. A picture omerges of a highly organized unit of signalling, a 'transducisome', with PDZ domains functioning as key elements in the organization of transduction complexes in vivo.