Feedback Regulation of Prothoracic Gland Activity

Sakurai, Shunsuke

doi:10.1016/b0-44-451924-6/00041-7

Cited by 16 publications

(18 citation statements)

References 138 publications

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“…This finding gives direct support to the various, but largely indirect, physiological studies that have indicated a feedback regulation of the neuroendocrine system by ecdysteroids in Rhodnius (Steel 1973(Steel , 1975 and in other insects (for a review, see Sakurai 2005). However, the finding that EcR is rhythmic in the neuroendocrine system indicates that the action of ecdysteroids is not merely stimulatory or inhibitory but rather influences rhythmicity in the system.…”

Section: Discussionmentioning

confidence: 40%

hormone nuclear receptor (EcR) exhibits circadian cycling in certain tissues, but not others, during development in Rhodnius prolixus (Hemiptera)

Vafopoulou

Steel

2005

Cell Tissue Res

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The insect moulting hormones, viz. the ecdysteroids, regulate gene expression during development by binding to an intracellular protein, the ecdysteroid receptor (EcR). In the insect Rhodnius prolixus, circulating levels of ecdysteroids exhibit a robust circadian rhythm. This paper demonstrates associated circadian rhythms in the abundance and distribution of EcR in several major target tissues of ecdysteroids, but not in others. Quantitative analysis of immunofluorescence images obtained by confocal laser-scanning microscopy following the use of anti-EcR has revealed a marked daily rhythm in the nuclear abundance of EcR in cells of the abdominal epidermis, brain, fat body, oenocytes and rectal epithelium of Rhodnius. This EcR rhythm is synchronous with the rhythm of circulating hormone levels. It free-runs in continuous darkness for several cycles, showing that EcR nuclear abundance is under circadian control. Circadian control of a nuclear receptor has not been shown previously in any animal. We infer that the above cell types detect and respond to the temporal signals in the rhythmic ecdysteroid titre. In several cell types, the rhythm in cytoplasmic EcR peaks several hours prior to the EcR peak in the nucleus each day, thereby implying a daily migration of EcR from the cytoplasm to the nucleus. This finding shows that EcR is not a constitutive nuclear receptor, as has previously been assumed. In the brain, rhythmic nuclear EcR has been found in peptidergic neurosecretory cells, indicating a potential pathway for feedback regulation of the neuroendocrine system by ecdysteroids, and also in regions containing circadian clock neurons, suggesting that the circadian timing system in the brain is also sensitive to rhythmic ecdysteroid signals.

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Section: Discussionmentioning

confidence: 40%

hormone nuclear receptor (EcR) exhibits circadian cycling in certain tissues, but not others, during development in Rhodnius prolixus (Hemiptera)

Vafopoulou

Steel

2005

Cell Tissue Res

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“…In mammals, Steroidogenic Factor 1 (SF-1) plays an important role in regulating steroidogenic hydroxylases (see Parker et al, 2002). In insects, nuclear receptors are critical for the control of the ecdysteroid levels and molting (Bialecki et al, 2002;see Henrich, 2005;Sakurai, 2005). A recent study by Parvy et al (2005) demonstrated that bFTZ-F1 (ftz transcription factor), the Drosophila homolog of SF-1, is involved in the regulation of phm and dib in the ring gland.…”

Section: Article In Pressmentioning

confidence: 97%

Identification, characterization and developmental expression of Halloween genes encoding P450 enzymes mediating ecdysone biosynthesis in the tobacco hornworm, Manduca sexta

Rewitz

Rybczynski

Warren

et al. 2006

Insect Biochemistry and Molecular Biology

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“…We selected the cells of the prothoracic gland (PG) for analysis, partly because of the central importance of this gland as the site of synthesis of Ec in insects, but also because the gland comprises about 200 very large and ultrastructurally uniform cells (Beaulaton et al, 1984), which are easily isolated for microscopic analysis (Wigglesworth, 1952). In addition, there is evidence that steroid synthesis by PGs is influenced by Ec showing that PG cells are responsive to their own hormone (suggestive of genomic responses to Ec) (reviewed by Sakurai, 2005), but also exhibit calcium-dependent action potentials (suggestive of non-genomic responses to Ec) (Eusebio and Moody, 1986). Both the cytoskeleton and mitochondria have been implicated in the mediation of non-genomic responses of steroid hormones in mammalian systems (see Discussion).…”

Section: Introductionmentioning

confidence: 97%

Ecdysteroid receptor (EcR) is associated with microtubules and with mitochondria in the cytoplasm of prothoracic gland cells of Rhodnius prolixus (Hemiptera)

Vafopoulou¹

2009

Arch Insect Biochem Physiol

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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.

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Feedback Regulation of Prothoracic Gland Activity

Cited by 16 publications

References 138 publications

hormone nuclear receptor (EcR) exhibits circadian cycling in certain tissues, but not others, during development in Rhodnius prolixus (Hemiptera)

hormone nuclear receptor (EcR) exhibits circadian cycling in certain tissues, but not others, during development in Rhodnius prolixus (Hemiptera)

Identification, characterization and developmental expression of Halloween genes encoding P450 enzymes mediating ecdysone biosynthesis in the tobacco hornworm, Manduca sexta

Ecdysteroid receptor (EcR) is associated with microtubules and with mitochondria in the cytoplasm of prothoracic gland cells of Rhodnius prolixus (Hemiptera)

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