Influence of hormone response elements (HREs) on ecdysteroid receptor concentration

Abstract

Transcriptional activity of nuclear receptors is the result of transactivation capability and receptor protein concentration. The concentration of ecdysteroid receptor (EcR) constitutively expressed in vertebrate cells varies depending on the isoforms. Besides ligand binding and heterodimerization with ultraspiracle (USP), which stabilizes receptor protein concentration, degradation is regulated by interaction of the receptor complex with different ecdysteroid response elements (EcREs). Coexpression of EcREs significantly reduces ecdysteroid receptor concentration depending on the type of EcRE. Transcriptional activity and interaction with hormone response elements (HREs) as determined by Electrophoretic Mobility Shift Assay (EMSA) are often inversely related to receptor protein concentration. The complex regulation of receptor protein concentration offers an additional opportunity to regulate transcriptional activity in an isoform- and target cell-specific manner and allows the temporal limitation of hormone action.

N‐ and C‐terminal degradation of ecdysteroid receptor isoforms, when transiently expressed in mammalian CHO cells, is regulated by the proteasome and cysteine and threonine proteases

“…In conclusion, the present results indicate that transcriptional activity is not only the result of differences in the transactivation capability of the EcR, as shown previously (Nakagawa & Henrich, 2009), but is also influenced by differences in receptor concentration, which is regulated in a complex manner by interaction with DNA (Schauer et al ., 2011a), ligand binding (Ruff et al ., 2009), and heterodimerization, in an isoform‐specific manner.…”

“…The plasmid map of pGL4.19TK hsp27 3× is available upon request. For further information see Schauer et al . (2011a, b).…”