Disease relevance of EcR

• Expression of EcR and USP in Escherichia coli: purification and functional studies [1].
• A similar block was observed when ecdysone receptor-containing RKO cells were infected with a replication-defective recombinant adenovirus containing an inducible KLF4 and treated with ponasterone A [2].
• Hypertrophy of the ventriculus correlated with a decrease in ecdysteroid hormone receptor B1 (EcRB1) protein, and furthermore could be suppressed by a heat-inducible EcRB1 transgene [3].
• Using an oligonucleotide derived from the amino-acid sequence of the Drosophila melanogaster ecdysone receptor, genes encoding homologues of the nuclear hormone receptor family were identified in the genome of the human filarial parasite Onchocerca volvulus [4].

High impact information on EcR

• DHR38 also heterodimerizes with USP, and this complex responds to a distinct class of ecdysteroids in a manner that is independent of EcR [5].
• We conclude that the Drosophila Activin signaling pathway mediates neuronal remodeling in part by regulating EcR-B1 expression [6].
• Binding of the insect steroid hormone ecdysone to distinct ecdysone receptor isoforms induces different metamorphic responses in various larval tissues [6].
• TAI protein colocalized with the ecdysone receptor in vivo and augmented transcriptional activation by the ecdysone receptor in cultured cells [7].
• In the larval salivary gland, loss of EcR-B1 results in loss of activation of ecdysone-induced genes [8].

Biological context of EcR

• We have identified the regions of Drosophila EcR and USP responsible for transcriptional activation of a semisynthetic Eip71CD promoter in Kc cells [9].
• EcR helix 12 mutants (F645A and W650A) exhibit a dominant negative phenotype [9].
• Mutagenesis reveals that AF2 function depends on EcR helix 12, but not on the cognate USP region [9].
• A mutation, K497E, in the shared ligand-binding domain of the EcR isoforms caused elevated EcRB2-specific affinity for a canonical ecdysone response element [10].
• Given the modest level of 20E-dependent activation, it is likely that the EcR-USP receptor acts synergistically with other transcription factors to bring about the high level of Vg gene expression [11].

Anatomical context of EcR

• VgEcRE binds directly to EcR-USP produced in vitro and extracted from the vitellogenic fat body nuclei [11].
• Cell-autonomous requirement of the USP/EcR-B ecdysone receptor for mushroom body neuronal remodeling in Drosophila [12].
• Ligand-dependent de-repression via EcR/USP acts as a gate to coordinate the differentiation of sensory neurons in the Drosophila wing [13].
• Moreover, a highly synergistically formed heterodimeric complex with the DNA-binding domain of EcR was observed on hsp27EcRE, but not on the native Usp response element from the chorion s15 gene promoter [14].
• USP and EcR fusion proteins could be expressed in separate cell lines and then recombined following isolation to yield a ligand binding preparation with a dissociation constant (K(D)) for Ponasterone A of 1.5 nM and a total yield of 1.9 pmol ligand binding sites/mg protein [15].

Associations of EcR with chemical compounds

• As with other retinoid X receptor heterodimers, EcR/USP affects gene transcription in a ligand-modulated manner [16].
• Our observations suggest that silencing by the unliganded EcR/USP receptor and the subsequent release of silencing by moderate steroid levels may play an important role in coordinating early phases of steroid driven development [17].
• Like, USP, it activates transcription in Drosophila Schneider S2 cells in a 20-hydroxyecdysone-dependent manner, via its interaction with the endogenous EcR protein [18].
• EcRB1 is normally induced with a form of USP that is missing its DNA-binding domain (DBD), although potentiation by juvenile hormone (JH) III is reduced [10].
• Whereas EcR-USP DNA-binding activity is unaffected by hormone, EcR-RXR DNA-binding activity is stimulated by either ecdysteroid or 9-cis-retinoic acid, demonstrating that hormone can play a role in heterodimer stabilization [19].

Physical interactions of EcR

• These results are consistent with a model in which these latter processes are induced by a signal arising during the middle of the last larval stage but suppressed by the unliganded EcR/USP complex [17].
• Polarity of the ecdysone receptor complex interaction with the palindromic response element from the hsp27 gene promoter [20].
• The developmental profile of fully activated, ligand refractory receptor complexes closely correlated with that of yolk protein expression, suggesting an intimate involvement of the ecdysone receptor complex in both the induction and maintenance of high level expression of yolk protein genes [21].
• Mutations in trr interact in eye development with EcR, and EcR and TRR can be co-immunoprecipitated on ecdysone treatment [22].
• The 20E receptor can bind to each of the sequences recognized by DHR78 and DHR96, indicating that these proteins may compete with the receptor for binding to a common set of target sequences [23].

Regulatory relationships of EcR

• This gene encodes the BR-C Z1 transcription factor and its expression is directly regulated by ecdysone through the ecdysone receptor (EcR/Usp) [24].
• Here we show that rpr is induced directly by the ecdysone-receptor complex through an essential response element in the rpr promoter [25].

Other interactions of EcR

• Surprisingly, most identified primary EcR/USP targets are dispensable for MB neuronal remodeling [12].
• Broad-complex, but not ecdysone receptor, is required for progression of the morphogenetic furrow in the Drosophila eye [26].
• DHR78, which encodes another candidate ecdysteroid receptor, is also not required [26].
• Di-RXR-1 can bind in vitro to EcR and DHR38, both known insect USP partners [18].
• Finally, BmEcR can substitute for DmEcR in an EcR-deficient Drosophila tissue culture line, stimulating trans-activation of an ecdysone-inducible reporter gene construct [27].

Analytical, diagnostic and therapeutic context of EcR

• Site-directed mutagenesis revealed that Phe529 in Aedes EcR, corresponding to Tyr611 in Drosophila EcR, was most critical for ligand specificity and hormone-independent DNA binding activity [28].
• AF2 function was studied using a two-hybrid assay in Kc cells, based on the observation that potent hormone-dependent activation by the EcR/USP ligand-binding domain heterodimer requires the participation of both partners [9].
• Analysis of transcriptional activity mediated by Drosophila melanogaster ecdysone receptor isoforms in a heterologous cell culture system [10].
• In this study, we developed a competitive reverse transcription polymerase chain reaction (RT-PCR) method to quantify the transcripts of functional ecdysone receptor components in individual tissues and for the whole body [29].
• Some amino acids are involved either in ligand binding to EcR (E476, M504, D572, I617, N626) or ligand-dependent heterodimerization as determined by gel mobility shift assays (A612, L615, T619), while others are involved in both functions (K497, E648) [30].

References