Ecdysteroid receptor (EcR) is associated with microtubules and with mitochondria in the cytoplasm of prothoracic gland cells of Rhodnius prolixus (Hemiptera).
We have shown previously that EcR in larval Rhodnius is present in the cytoplasm of various cell types and undergoes daily cycling in abundance in the cytoplasm (Vafopoulou and Steel, 2006. Cell Tissue Res 323:443-455). It is unknown which organelles are associated with EcR. Here, we report that cytoplasmic EcR in prothoracic gland cells is associated with both microtubules and mitochondria, and discuss the implications for both nuclear and non-genomic actions of EcR. EcR was localized immunohistochemically using several antibodies to EcR of Manduca and Drosophila and a confocal laser scanning microscope. Double labels were made to visualize EcR and (1) microtubules (using an antibody to tyrosylated alpha-tubulin) and (2) mitochondria (using a fluorescent MitoTracker probe), both after stabilization of microtubules with taxol. EcR co-localized with both tubulin and mitochondria. All the different EcR antibodies produced similar co-localization patterns. EcR was seen in the perinuclear aggregation of mitochondria, indicating that mitochondria are targets of ecdysone, which could influence mitochondrial gene transcription. EcR was also distributed throughout the microtubule network. Co-localization of EcR with tubulin or mitochondria was maintained after depolymerization of microtubules with colchicine. Treatment with taxol resulted in accumulation of EcR in the cytoplasm and simultaneous depletion of EcR from the nucleus, suggesting that microtubules may be involved in targeted intracellular transport of EcR to the nucleus (genomic action) or may play a role in rapid ecdysone signal transduction in the extranuclear compartment, i.e., in non-genomic actions of ecdysone. These findings align EcR more closely with steroid hormone receptors in vertebrates.
Department of Biology, York University, 4700 Keele Street, Toronto, Ontario, Canada. xanthev@yorku.ca
Xanthe
X
Vafopoulou
D000818:Animals; D003593:Cytoplasm / Q000378:metabolism*; D004330:Drosophila; D007150:Immunohistochemistry; D019476:Insect Proteins / Q000032:analysis / Q000378:metabolism* / Q000502:physiology; D007814:Larva / Q000378:metabolism / Q000648:ultrastructure; D008297:Male; D018402:Manduca; D008870:Microtubules / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D011987:Receptors, Steroid / Q000032:analysis / Q000378:metabolism* / Q000502:physiology; D012239:Rhodnius / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D014404:Tubulin / Q000378:metabolism
D019476:Insect Proteins; D011987:Receptors, Steroid; D014404:Tubulin; C034808:ecdysteroid receptor