Nieva Claudia, Spindler-Barth Margarethe, Spindler Klaus-Dieter
Institute of General Zoology and Endocrinology, University of Ulm, Ulm, Germany.
Arch Insect Biochem Physiol. 2008 May;68(1):40-8. doi: 10.1002/arch.20234.
Initially, nuclear import of the ecdysteroid receptor (EcR) in vertebrate cells (CHO-K1 and COS-7) does not afford a heterodimerization partner. Later on, EcR is retained in the nucleus only in the presence of a heterodimerization partner. Ultraspiracle (Usp) is more efficient compared to its vertebrate orthologue RXR and leads to an exclusively nuclear localization of EcR even in the absence of ligand. The DNA binding domain of the heterodimerization partner is important for retainment of EcR in the nucleus as shown by Usp4 (Usp(R130C)), which has lost its DNA binding capability. The C-terminal end of Usp (Usp(Delta205-508)) encompassing the C-terminal part of the D-domain and the E- and F-domains are essential for retainment of EcR in the nucleus. Nuclear localization is further influenced by cell-specific factors, since hormone and heterodimerization stabilizes the EcR protein in a cell-specific way.
最初，在脊椎动物细胞（CHO - K1和COS - 7）中，蜕皮甾体受体（EcR）的核输入无法提供异源二聚化伴侣。后来，只有在存在异源二聚化伴侣的情况下，EcR才会保留在细胞核中。与脊椎动物同源物RXR相比，超气门蛋白（Usp）效率更高，即使在没有配体的情况下，也能使EcR完全定位于细胞核。如失去DNA结合能力的Usp4（Usp(R130C)）所示，异源二聚化伴侣的DNA结合结构域对于EcR在细胞核中的保留很重要。超气门蛋白（Usp(Delta205 - 508)）的C末端包含D结构域的C末端部分以及E结构域和F结构域，对于EcR在细胞核中的保留至关重要。核定位还受到细胞特异性因子的进一步影响，因为激素和异源二聚化以细胞特异性方式稳定EcR蛋白。
