Constitutive activity of the light-sensitive channels TRP and TRPL in the Drosophila diacylglycerol kinase mutant, rdgA.
Mutations in the Drosophila retinal degeneration A (rdgA) gene, which encodes diacylglycerol kinase (DGK), result in early onset retinal degeneration and blindness. Whole-cell recordings revealed that light-sensitive Ca2+ channels encoded by the trp gene were constitutively active in rdgA photoreceptors. Early degeneration was rescued in rdgA;trp double mutants, lacking TRP channels; however, the less Ca2+-permeable light-sensitive channels (TRPL) were constitutively active instead. No constitutive activity was seen in rdgA;trpI;trp mutants lacking both classes of channel, although, like rdgA;trp, these still showed a residual slow degeneration. Responses to light were restored in rdgA;trp but deactivated abnormally slowly, indicating that DGK is required for response termination. The findings suggest that early degeneration in rdgA is caused by uncontrolled Ca2+ influx and support the proposal that diacylglycerol or its metabolites are messengers of excitation in Drosophila photoreceptors.
Raghu
P
P
Department of Anatomy, Cambridge University, United Kingdom.
Usher
K
K
Jonas
S
S
Chyb
S
S
Polyanovsky
A
A
Hardie
R C
RC
D000818:Animals; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019852:Diacylglycerol Kinase / Q000235:genetics / Q000378:metabolism*; D004330:Drosophila / Q000235:genetics; D029721:Drosophila Proteins; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D010786:Photoreceptor Cells / Q000378:metabolism*; D012162:Retinal Degeneration / Q000235:genetics* / Q000378:metabolism; D050052:TRPC Cation Channels; D050051:Transient Receptor Potential Channels; D014785:Vision, Ocular / Q000235:genetics / Q000502:physiology
D015220:Calcium Channels; D002148:Calmodulin-Binding Proteins; D029721:Drosophila Proteins; D008565:Membrane Proteins; D050052:TRPC Cation Channels; D050051:Transient Receptor Potential Channels; C096351:transient receptor potential cation channel, subfamily C, member 1; C074192:trpl protein, Drosophila; D019852:Diacylglycerol Kinase