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Subcellular localization

cilia, Nucleoplasm, Vesicles

Functional category

• Metabolism

Function

We have investigated the intracellular localization and regulatory patterns for ERbeta isoforms in rat fallopian tubes. Western blot analysis reveals that two ERbeta isoforms corresponding to ERbeta1 and ERbeta2 are expressed in rat fallopian tubes. However, ERbeta2 is the predominant form of ERbeta in this tissue. High-resolution confocal imaging and immunohistochemical analysis provide ample evidence that ERbeta expression is limited almost exclusively to the ciliated epithelial cells, in contrast to ERalpha, which is widely distributed. Furthermore, within the ciliated epithelial cells, ERbeta is colocalized with beta-tubulin IV at stem portion of the cilia. We show that ERbeta2 protein expression is tightly regulated by E(2) or DPN in a time-dependent manner without changes in ERbeta1 expression. These estrogenic effects are inhibited by an ER antagonist, ICI 182,780. In addition, significant alteration of ERbeta immunoreactivity is detected only histologically in the ampullary region. Since the cilia are considered an essential determinant of tubal transport, we further demonstrate that E(2)- or DPN-induced ERbeta2 activation is associated with alterations in tubal protein expression crucial for the regulation of calcium-dependent ciliary beating. Given the coordinated regulation and interaction of ER and progesterone receptor in the cilia, we hypothesize that tubal ERbeta2 may facilitate the estrogen-mediated transport process by processing protein-protein interaction under physiological and/or pathological conditions. We show for the first time that a previously unrecognized localization of ERbeta isoform in rat fallopian tubes can combine with estrogen to individually control the expression of ER beta-isoforms in normal target tissues(17374697). We identified ERbeta expression and localization in rat fallopian tubes, suggesting a potential biological function of ERbeta related to calcium-dependent ciliated beating. Here we provide for the first time insight into the less studied ERalpha isoforms, which mediate estrogen-dependent production and secretion of IGFs in vivo. First, Western blot studies revealed that three ERalpha isoforms were expressed in mouse fallopian tubes. Subsequent immunohistochemical analysis showed that ERalpha was detected in all cell types, whereas ERbeta was mainly localized in ciliated epithelial cells. Second, ERalpha isoform levels were dramatically downregulated in mouse fallopian tubes by treatment with E(2) or PPT, an ERalpha agonist, in a time-dependent manner. Third, the presence of ICI 182,780, an ER antagonist, blocked the E(2)- or PPT-induced downregulation of tubal ERalpha isoform expression in mice. However, alteration of ERalpha immunoreactivity following ICI 182,780 treatment was only detected in epithelial cells of the ampullary region. Fourth, changes in ERalpha isoform expression were found to be coupled to multiple E(2) effects on tubal growth, protein synthesis, and secretion in mouse fallopian tube tissues and fluid. In particular, E(2) exhibited positive regulation of IGF-I and IGF-II protein levels. Finally, using growth hormone receptor (GHR) gene-disrupted mice, we showed that regulation by E(2) of IGF production was independent of GH-induced GHR signaling in mouse fallopian tubes in vivo. These data, together with previous studies from our laboratory, suggest that the long-term effects of estrogen agonist promote IGF synthesis and secretion in mouse tubal epithelial cells and fallopian tube fluid via stimulation of ERalpha(17848632).