title: Dynamic scaffolding in a G protein-coupled signaling system.
abstract: The INAD scaffold organizes a multiprotein complex that is essential for proper visual signaling in Drosophila photoreceptor cells. Here we show that one of the INAD PDZ domains (PDZ5) exists in a redox-dependent equilibrium between two conformations--a reduced form that is similar to the structure of other PDZ domains, and an oxidized form in which the ligand-binding site is distorted through formation of a strong intramolecular disulfide bond. We demonstrate transient light-dependent formation of this disulfide bond in vivo and find that transgenic flies expressing a mutant INAD in which PDZ5 is locked in the reduced state display severe defects in termination of visual responses and visually mediated reflex behavior. These studies demonstrate a conformational switch mechanism for PDZ domain function and suggest that INAD behaves more like a dynamic machine rather than a passive scaffold, regulating signal transduction at the millisecond timescale through cycles of conformational change.
authors.affiliation: Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390-9050, USA.
authors.forename: Prashant
authors.initials: P
authors.lastname: Mishra
authors.forename: Michael
authors.initials: M
authors.lastname: Socolich
authors.forename: Mark A
authors.initials: MA
authors.lastname: Wall
authors.forename: Jennifer
authors.initials: J
authors.lastname: Graves
authors.forename: ZiFen
authors.initials: Z
authors.lastname: Wang
authors.forename: Rama
authors.initials: R
authors.lastname: Ranganathan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D001522:Behavior, Animal / Q000502:physiology; D004220:Disulfides / Q000737:chemistry; D029721:Drosophila Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000033:anatomy & histology / Q000502:physiology; D005136:Eye Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008027:Light; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D054731:PDZ Domains; D018408:Patch-Clamp Techniques; D017956:Photoreceptor Cells, Invertebrate / Q000502:physiology; D017434:Protein Structure, Tertiary; D015290:Second Messenger Systems / Q000502:physiology*; D016415:Sequence Alignment; D015398:Signal Transduction; D014785:Vision, Ocular
chemical_list: D004220:Disulfides; D029721:Drosophila Proteins; D005136:Eye Proteins; C091568:inaD protein, Drosophila; D019204:GTP-Binding Proteins