A TRANSCRIPTION INHIBITOR, ACTINOMYCIN-D, PARTIALLY INHIBITS THE RHABDOMERAL RENEWAL INDUCED BY A DIACYLGLYCEROL LIPASE INHIBITOR, U-57908 IN CRAB RETINAS

1. A previous study implies that diacylglycerols (DAGs) released by th e phototransduction cascade in photoreceptors of a crab, Leptograpsus, activate protein kinase Cs (PKCs). PKCs were suggested to phosphoryla te nuclear proteins that regulate the transcription of rhabdomeral mem brane precursors. 2. We show that a transcription inhibitor, actinomyc in D, reduces the rhabdomeral renewal induced by a diacylglycerol lipa se inhibitor, U-57908, but does not eliminate it. 3. Within the partic ular experimental protocol, rhabdomeral maintenance and renewal by con trols are inhibited by actinomycin D in an absence of U-57908. 4. We c onclude that although rhabdomeral renewal induced by PKC activation in volves the regulation of transcription, multiple pathways are implicat ed. 5. An alternative route for the degradation of DAGs by phosphoryla tion is eliminated because a specific inhibitor of DAG kinases, R-5902 2, exerts no effect.6. U-57908 promotes photoreceptor shrinkage which is not compromised by actinomycin D. Shrinkage occurs independently of rhabdomeral renewal, suggesting a further consequence of PKC activati on.