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The nuclear receptor DHR3 modulates dS6 kinase-dependent growth in Drosophila.

Montagne J, Lecerf C, Parvy JP, Bennion JM, Radimerski T, Ruhf ML, Zilbermann F, Vouilloz N, Stocker H, Hafen E, Kozma SC, Thomas G - PLoS Genet. (2010)

Bottom Line: S6 kinases (S6Ks) act to integrate nutrient and insulin signaling pathways and, as such, function as positive effectors in cell growth and organismal development.Consistent with these findings, we have identified an endogenous DHR3 isoform that lacks the DBD.These results provide the first molecular link between the dS6K pathway, critical in controlling nutrient-dependent growth, and that of DHR3, a major mediator of ecdysone signaling, which, acting together, coordinate metamorphosis.

View Article: PubMed Central - PubMed

Affiliation: Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland. montagne@cgm.cnrs-gif.fr

ABSTRACT
S6 kinases (S6Ks) act to integrate nutrient and insulin signaling pathways and, as such, function as positive effectors in cell growth and organismal development. However, they also have been shown to play a key role in limiting insulin signaling and in mediating the autophagic response. To identify novel regulators of S6K signaling, we have used a Drosophila-based, sensitized, gain-of-function genetic screen. Unexpectedly, one of the strongest enhancers to emerge from this screen was the nuclear receptor (NR), Drosophila hormone receptor 3 (DHR3), a critical constituent in the coordination of Drosophila metamorphosis. Here we demonstrate that DHR3, through dS6K, also acts to regulate cell-autonomous growth. Moreover, we show that the ligand-binding domain (LBD) of DHR3 is essential for mediating this response. Consistent with these findings, we have identified an endogenous DHR3 isoform that lacks the DBD. These results provide the first molecular link between the dS6K pathway, critical in controlling nutrient-dependent growth, and that of DHR3, a major mediator of ecdysone signaling, which, acting together, coordinate metamorphosis.

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DHR3 is a specific dS6K interacter.Induction of UAS constructs and EPs by the ap promoter directed Gal4 expression within the dorsal compartment of the wing imaginal disc: (A) ap-Gal4 control; (B, E, H, J, K) UAS-dS6K; (C, F, I) UAS-S6K1dE/D3E; (D, E, F) DHR3-EP; (G, H, I, K) UAS-DHR3-RNAi and (J) unidirectional DHR3-EP. The bending down of the wing indicates a slight overgrowth of the dorsal compartment, whereas a bending up reveals a slight growth deficit of this compartment.
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pgen-1000937-g001: DHR3 is a specific dS6K interacter.Induction of UAS constructs and EPs by the ap promoter directed Gal4 expression within the dorsal compartment of the wing imaginal disc: (A) ap-Gal4 control; (B, E, H, J, K) UAS-dS6K; (C, F, I) UAS-S6K1dE/D3E; (D, E, F) DHR3-EP; (G, H, I, K) UAS-DHR3-RNAi and (J) unidirectional DHR3-EP. The bending down of the wing indicates a slight overgrowth of the dorsal compartment, whereas a bending up reveals a slight growth deficit of this compartment.

Mentions: Imaginal discs are subdivided into compartments, with each constituting an individual growth unit that differentiates into an adult structure during metamorphosis [22]. In this context, ectopic expression of dS6K within the developing dorsal wing compartment, using the apterous-Gal4 (ap-Gal4) driver, induces a moderate overgrowth in this unit [18] and a bending-down of the adult wing (Figure 1A and 1B). Consistent with PDK1 being the mammalian S6K1 activation-loop kinase [35], [36], we have previously demonstrated an enhanced bending-down of the adult wing by co-expression of the Drosophila PDK1 (dPDK1), whereas expression of dPDK1 alone had no effect on this phenotype [17]. Likewise, the expression of particular phosphorylation-site mutants of dS6K that would be predicted to increase or decrease the activation state of dS6K, enhances or suppresses this phenotype, respectively [19]. These findings demonstrate that the bent-down wing phenotype varies according to dS6K activation status, and prompted us to use this sensitized phenotype in a gain-of-function genetic screen to identify novel modulators of dS6K activity. We also found that ectopic expression of an active form of the mammalian S6 Kinase 1, S6K1dE/D3E [37], induced a bent-down wing phenotype equivalent to that induced by dS6K (compare Figure 1B and 1C). Like dS6K, co-expression of S6K1dE/D3E and dPDK1 led to an enhancement of the bent-down wing phenotype, but not to the extent observed with dS6K (data not shown). We reasoned that this differential phenotype may represent dPDK1 specificity for dS6K, a bona fide substrate, unlike S6K1dE/D3E [17], [38], and have utilized this differential effect to increase the selectivity of the gain-of-function screen (see below).


The nuclear receptor DHR3 modulates dS6 kinase-dependent growth in Drosophila.

Montagne J, Lecerf C, Parvy JP, Bennion JM, Radimerski T, Ruhf ML, Zilbermann F, Vouilloz N, Stocker H, Hafen E, Kozma SC, Thomas G - PLoS Genet. (2010)

DHR3 is a specific dS6K interacter.Induction of UAS constructs and EPs by the ap promoter directed Gal4 expression within the dorsal compartment of the wing imaginal disc: (A) ap-Gal4 control; (B, E, H, J, K) UAS-dS6K; (C, F, I) UAS-S6K1dE/D3E; (D, E, F) DHR3-EP; (G, H, I, K) UAS-DHR3-RNAi and (J) unidirectional DHR3-EP. The bending down of the wing indicates a slight overgrowth of the dorsal compartment, whereas a bending up reveals a slight growth deficit of this compartment.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2865512&req=5

pgen-1000937-g001: DHR3 is a specific dS6K interacter.Induction of UAS constructs and EPs by the ap promoter directed Gal4 expression within the dorsal compartment of the wing imaginal disc: (A) ap-Gal4 control; (B, E, H, J, K) UAS-dS6K; (C, F, I) UAS-S6K1dE/D3E; (D, E, F) DHR3-EP; (G, H, I, K) UAS-DHR3-RNAi and (J) unidirectional DHR3-EP. The bending down of the wing indicates a slight overgrowth of the dorsal compartment, whereas a bending up reveals a slight growth deficit of this compartment.
Mentions: Imaginal discs are subdivided into compartments, with each constituting an individual growth unit that differentiates into an adult structure during metamorphosis [22]. In this context, ectopic expression of dS6K within the developing dorsal wing compartment, using the apterous-Gal4 (ap-Gal4) driver, induces a moderate overgrowth in this unit [18] and a bending-down of the adult wing (Figure 1A and 1B). Consistent with PDK1 being the mammalian S6K1 activation-loop kinase [35], [36], we have previously demonstrated an enhanced bending-down of the adult wing by co-expression of the Drosophila PDK1 (dPDK1), whereas expression of dPDK1 alone had no effect on this phenotype [17]. Likewise, the expression of particular phosphorylation-site mutants of dS6K that would be predicted to increase or decrease the activation state of dS6K, enhances or suppresses this phenotype, respectively [19]. These findings demonstrate that the bent-down wing phenotype varies according to dS6K activation status, and prompted us to use this sensitized phenotype in a gain-of-function genetic screen to identify novel modulators of dS6K activity. We also found that ectopic expression of an active form of the mammalian S6 Kinase 1, S6K1dE/D3E [37], induced a bent-down wing phenotype equivalent to that induced by dS6K (compare Figure 1B and 1C). Like dS6K, co-expression of S6K1dE/D3E and dPDK1 led to an enhancement of the bent-down wing phenotype, but not to the extent observed with dS6K (data not shown). We reasoned that this differential phenotype may represent dPDK1 specificity for dS6K, a bona fide substrate, unlike S6K1dE/D3E [17], [38], and have utilized this differential effect to increase the selectivity of the gain-of-function screen (see below).

Bottom Line: S6 kinases (S6Ks) act to integrate nutrient and insulin signaling pathways and, as such, function as positive effectors in cell growth and organismal development.Consistent with these findings, we have identified an endogenous DHR3 isoform that lacks the DBD.These results provide the first molecular link between the dS6K pathway, critical in controlling nutrient-dependent growth, and that of DHR3, a major mediator of ecdysone signaling, which, acting together, coordinate metamorphosis.

View Article: PubMed Central - PubMed

Affiliation: Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland. montagne@cgm.cnrs-gif.fr

ABSTRACT
S6 kinases (S6Ks) act to integrate nutrient and insulin signaling pathways and, as such, function as positive effectors in cell growth and organismal development. However, they also have been shown to play a key role in limiting insulin signaling and in mediating the autophagic response. To identify novel regulators of S6K signaling, we have used a Drosophila-based, sensitized, gain-of-function genetic screen. Unexpectedly, one of the strongest enhancers to emerge from this screen was the nuclear receptor (NR), Drosophila hormone receptor 3 (DHR3), a critical constituent in the coordination of Drosophila metamorphosis. Here we demonstrate that DHR3, through dS6K, also acts to regulate cell-autonomous growth. Moreover, we show that the ligand-binding domain (LBD) of DHR3 is essential for mediating this response. Consistent with these findings, we have identified an endogenous DHR3 isoform that lacks the DBD. These results provide the first molecular link between the dS6K pathway, critical in controlling nutrient-dependent growth, and that of DHR3, a major mediator of ecdysone signaling, which, acting together, coordinate metamorphosis.

Show MeSH