Similarity and Difference in Distribution of Estrogen Receptor-alpha Protein in Artificially Differentiated and Senescent Neuronal Cultured Cell

ABSTRACT

BACKGROUND: We tried to see if the change in subcellular distribution of estrogen receptor alpha(ER-alpha) was occurring in the senescent or differentiated cells. And if any, we also tried to observe the similarities or differences of distribution changes in ER-alpha in these two groups. METHODS: By treatment with 3'-Azido-3'-deoxythymidine(AZT, Sigma-Aldrich, USA, 1micrometer) on PC12 pheochromocytoma cells line(ATCC CRL-1721). Immunohistochemistries with anti-ER-alpha antibody were also performed on the cells without treatment of AZT, with treatment of 74 days and 140 days. The same staining was also done on the arti-ficially differentiated cells induced by nerve growth factor(50ng/ml) for 5 days. The distribution of ER-alpha in these two cell groups were compared by confocal laser microscope. RESULTS: Senescent PC12 cells treated with AZT showed the changes in morphologies or cell sizes, comparing with normal counterparts. Subcellular localization of ER-alpha in cytoplasmic compartment increased in the cells treated with AZT during much longer duration. Same change in subcelluar distribution was also identified in the cells treated with NGF. In fully differentiated cells, we could find the presence of ER-alpha mainly in the cytoplasmic compartment. However, as to the organelles expressing ER-alpha, senescent and differentiated cells showed differences; mainly expressed in mitochondria in differentiated cells; but expressed diffused in cytoplasm in senescent cells. CONCLUSION: We could see the similarities in subcellular distribution of ER-alpha in the artificially senescent and differentiated neuronal cells. Increase in cytoplasmic expression of ER-alpha in cytoplasm was found in much senescent or differentiated cells. Considering that cell proliferation decrease both in senescence and differentiation, increase in ER-alpha in cytoplasmic compartment might be caused by decrease in cell proliferation of these two changes. This means that estrogen might play a role in inhibiting cell proliferation via its increased receptors within cytoplasmic compartment. In addition, we also found the differences in organelles expressing ER-alpha in both cases, suggesting that minor differences in mechanism for action of estrogen in both cases of senescent and differentiated cells. Estrogen might play a major role through mitochondria in cell differentiation; but not in cell senescence.