Membrane-resident steroid receptors and methods of use thereof

DETAILED DESCRIPTION This invention pertains to the discovery that DPR-1 (formerly known as END-2) a putative nuclear hormone receptor (NHR) that, based on gene reporter studies, is expressed in the endoderm throughout the life of the worm C.
elegans.
NHR family members are transcriptional regulators that are activated when bound to their small lipophilic ligands such as steroids.
While some NHRs are localized to the nucleus, others are cytoplasmic in the absence of ligand and translocate to the nucleus upon ligand binding.
Once in the nucleus, they bind target sequences and regulate gene expression.
We have found that while DPR-1 is present in the nucleus during early development, unexpectedly, it appears to localize to the plasma membrane under certain conditions later in development.
DPR-1 antibody reveals nuclear expression of the protein in posterior cells of early embryos (pre-bean stage), consistent with RNA in situ analysis.
However, by the bean stage, DPR-1 antigen relocalizes to the plasma membranes of developing gut cells.
This membrane association continues through to hatching.
Our preliminary biochemical results further indicate that DPR-1 partially associates with the membrane fraction obtained from both early and late embryos based on western blot analysis of embryonic extracts.
We found that in larvae, DPR-1 antigen is either primarily cytoplasmic (and nuclear-excluded) or is localized to the membrane, depending on the preparation examined.
The variable localization of DPR-1 to the cytoplasm or membrane in larvae is attributable to variations in environmental conditions.
When C.
elegans is grown in uncrowded conditions, DPR-1 is present throughout the cytoplasm of gut cells.
However, when they are cultured at high density, the protein appears to partition to the membrane.
The effect of crowding on DPR-1 localization may be a response to dauer pheromone.
This intriguing localization pattern of DPR-1 is atypical for NHRs and suggests a possible novel mode of action.
One postulate is that membrane-associated DPR-1 transduces a signal from the membrane