Ecdysteroid receptors, effect

Lin et al. [149] have recently reported the synthesis of 2-(4,5-dimethoxy-2-nitrobenzyl)-20-hydroxyecdysone (6-6), which itself has a very low affinity for ecdysteroid receptors expressed in mammalian 293T cells, but can be photolysed at 348 nm to release 20E, which then activates the receptor-regulated reporter gene. With this system, it will be possible not only to control the temporal activation of transfected genes, but also their spatial activation. The authors recognise that the effectiveness of this system can be considerably improved in future by derivatising an ecdysteroid (poA or muA) which is more active in ecdysteroid-responsive mammalian cells. 

Fig. 25.1.1. Chemical structures of 20-hydroxyecdysone (20E 1 R] = OH), the first bisacylhydrazine found to have an ecdysone agonist effect in insect assays (2), and the first bisacylhydrazine (RH-5849 3) well characterized for its ecdysone effects at cellular and whole insect level, as well as binding to Drosophila melanogaster ceW extracts containing ecdysteroid receptor complexes. Numbers on the 20E structure represent the carbon-numbering system.

In addition to the actions mediated by intracellular receptors, steroid hormones also demonstrate certain rapid (occurring within seconds) actions, which appear to be mediated by membrane effects/receptors this is true for vertebrate [114] and invertebrate [115] steroids. One presumes that the SAR studies for ecdysteroids which have been performed to date are predominantly determined by interaction of ecdysteroids with nuclear receptors, but one should bear in mind that in certain assay systems the... 

Due to their structural similarity, ecdysteroids might compete with brassinosteroids for the same receptor site. With the aim of looking at a possible interaction of both BR-1 and ecydsone, the compounds were combined covering a wide range of concentrations (Table IV). The effect of BR-1 was largely... 

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