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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenosine Triphosphate / genetics
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Adenosine Triphosphate / metabolism
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Animals
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Dark Adaptation / genetics
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Diacylglycerol Kinase / genetics*
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Down-Regulation / genetics
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Drosophila melanogaster / enzymology*
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Drosophila melanogaster / genetics
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Fungal Proteins / genetics
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GTP-Binding Protein alpha Subunits, Gq-G11
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GTP-Binding Proteins / genetics*
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Heterotrimeric GTP-Binding Proteins / genetics
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Heterotrimeric GTP-Binding Proteins / metabolism
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Membrane Potentials / genetics
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Mutation / genetics
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Phosphatidylinositol Diacylglycerol-Lyase
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Photoreceptor Cells, Invertebrate / cytology
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Photoreceptor Cells, Invertebrate / enzymology*
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Rhodopsin / genetics
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Saccharomyces cerevisiae Proteins*
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Sensory Thresholds / physiology
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Transcription Factors / deficiency
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Transcription Factors / genetics
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Type C Phospholipases / deficiency
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Type C Phospholipases / genetics*
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Vision, Ocular / genetics*
Substances
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Fungal Proteins
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PIP2 protein, S cerevisiae
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Saccharomyces cerevisiae Proteins
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Transcription Factors
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Adenosine Triphosphate
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Rhodopsin
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Diacylglycerol Kinase
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Type C Phospholipases
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GTP-Binding Proteins
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GTP-Binding Protein alpha Subunits, Gq-G11
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Heterotrimeric GTP-Binding Proteins
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Phosphatidylinositol Diacylglycerol-Lyase