title: Molecular basis of amplification in Drosophila phototransduction: roles for G protein, phospholipase C, and diacylglycerol kinase.
abstract: In Drosophila photoreceptors, the amplification responsible for generating quantum bumps in response to photoisomerization of single rhodopsin molecules has been thought to be mediated downstream of phospholipase C (PLC), since bump amplitudes were reportedly unaffected in mutants with greatly reduced levels of either G protein or PLC. We now find that quantum bumps in such mutants are reduced approximately 3- to 5-fold but are restored to near wild-type values by mutations in the rdgA gene encoding diacylglycerol kinase (DGK) and also by depleting intracellular ATP. The results demonstrate that amplification requires activation of multiple G protein and PLC molecules, identify DGK as a key enzyme regulating amplification, and implicate diacylglycerol as a messenger of excitation in Drosophila phototransduction.
authors.affiliation: Department of Anatomy, Cambridge University, Downing Street, Cambridge, United Kingdom.
authors.forename: R C
authors.initials: RC
authors.lastname: Hardie
authors.forename: F
authors.initials: F
authors.lastname: Martin
authors.forename: G W
authors.initials: GW
authors.lastname: Cochrane
authors.forename: M
authors.initials: M
authors.lastname: Juusola
authors.forename: P
authors.initials: P
authors.lastname: Georgiev
authors.forename: P
authors.initials: P
authors.lastname: Raghu
mesh_terms: D000255:Adenosine Triphosphate / Q000235:genetics / Q000378:metabolism; D000818:Animals; D003623:Dark Adaptation / Q000235:genetics; D019852:Diacylglycerol Kinase / Q000235:genetics*; D015536:Down-Regulation / Q000235:genetics; D004331:Drosophila melanogaster / Q000201:enzymology* / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D019204:GTP-Binding Proteins / Q000235:genetics*; D020962:Heterotrimeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D008564:Membrane Potentials / Q000235:genetics; D009154:Mutation / Q000235:genetics; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D017956:Photoreceptor Cells, Invertebrate / Q000166:cytology / Q000201:enzymology*; D012243:Rhodopsin / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D012684:Sensory Thresholds / Q000502:physiology; D014157:Transcription Factors / Q000172:deficiency / Q000235:genetics; D010738:Type C Phospholipases / Q000172:deficiency / Q000235:genetics*; D014785:Vision, Ocular / Q000235:genetics*
chemical_list: D005656:Fungal Proteins; C100530:PIP2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D000255:Adenosine Triphosphate; D012243:Rhodopsin; D019852:Diacylglycerol Kinase; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins; D043265:Phosphatidylinositol Diacylglycerol-Lyase