title: The visual G protein of fly photoreceptors interacts with the PDZ domain assembled INAD signaling complex via direct binding of activated Galpha(q) to phospholipase cbeta.
abstract: Visual transduction in the compound eye of flies is a well-established model system for the study of G protein-coupled transduction pathways. Pivotal components of this signaling pathway, including the principal light-activated Ca(2+) channel transient receptor potential, an eye-specific protein kinase C, and the norpA-encoded phospholipase Cbeta, are assembled into a supramolecular signaling complex by the modular PDZ domain protein INAD. We have used immunoprecipitation assays to study the interaction of the heterotrimeric visual G protein with this INAD signaling complex. Light-activated Galpha(q)- guanosine 5'-O-(thiotriphosphate) and AlF(4)(-)-activated Galpha(q), but not Gbetagamma, form a stable complex with the INAD signaling complex. This interaction requires the presence of norpA-encoded phospholipase Cbeta, indicating that phospholipase Cbeta is the target of activated Galpha(q). Our data establish that the INAD signaling complex is a light-activated target of the phototransduction pathway, with Galpha(q) forming a molecular on-off switch that shuttles the visual signal from activated rhodopsin to INAD-linked phospholipase Cbeta.
authors.affiliation: Department of Cell, Institute of Zoology, University of Karlsruhe, D-76128 Karlsruhe, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Bähner
authors.forename: P
authors.initials: P
authors.lastname: Sander
authors.forename: R
authors.initials: R
authors.lastname: Paulsen
authors.forename: A
authors.initials: A
authors.lastname: Huber
mesh_terms: D000818:Animals; D004175:Diptera; D004330:Drosophila; D029721:Drosophila Proteins; D005136:Eye Proteins / Q000737:chemistry / Q000378:metabolism*; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D019204:GTP-Binding Proteins / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism*; D008297:Male; D054799:Phospholipase C beta; D017956:Photoreceptor Cells, Invertebrate / Q000378:metabolism*; D011485:Protein Binding; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000378:metabolism*
chemical_list: D029721:Drosophila Proteins; D005136:Eye Proteins; D007527:Isoenzymes; C091568:inaD protein, Drosophila; D010738:Type C Phospholipases; D054799:Phospholipase C beta; D019204:GTP-Binding Proteins; D043802:GTP-Binding Protein alpha Subunits, Gq-G11