Influence of cell cycle on ecdysteroid receptor in CHO-K1 cells.

摘要

CHO-K1 cells are routinely used for characterization of ecdysone receptor (EcR) function, because these vertebrate cells are devoid of endogenous ecdysone receptor protein. Moreover, the endogenous expression of RXR, the vertebrate orthologue of Ultraspiracle (Usp), the most important heterodimerization partner, is neglectable. In contrast to insect cells, there is also no influence of moulting hormone on CHO-K1 cells on cell proliferation either in the absence or presence of transiently expressed EcR. In contrast to Usp, which is exclusively found in nuclei, EcR is heterogeneously distributed between cytoplasm and nuclei in non-synchronized cells. Synchronization of CHO-K1 cells by nocodazole revealed that the cell cycle influences receptor concentration with lowest amounts in late S-phase and G2/M phase and intracellular distribution of the receptor protein showing a minimum of receptors present in nuclei during S-phase. EcR, but not Usp reduces cyclin D1 expression and cyclin D1 concentration is impaired by cyclin D1. Coimmunoprecipitation studies reveal physical interaction of EcR and cyclin D1.