Estrogen receptor α(ERα) target gene LRP16 interacts with ERα and enhances receptor’s transcriptional activity

Abstract

Objective

It has been shown that LRP16 is an estrogen-induced gene through its recepto rα(ERα). Although there is evidence demonstrating that inhibition of LRP16 gene expression in MCF-7 human breast cancer cells partially attenuates its estrogen-responsiveness, the underlying molecular mechanism is still unclear. Here, the effect of LRP16 expression on the ERα signaling transduction was investigated.

Methods

Cotransfection assays were used to measure the effect of LRP16 on ERα-mediated transcriptional activity. GST-pulldown and immunoprecipitation (CoIP) assays were employed to investigate the physical interaction of LRP16 and ERα. The mammalian two-hybrid method was used to map the functional interaction region.

Results

The results of cotransfection assays demonstrated that the transcriptional activities of ERα were enhanced in a LRP16 dose-dependent manner in MCF-7 in the presence of estrogen, however, it was abolished in the absence of E2 in MCF-7 cells. The physical interaction of LRP16 and ERα proteins was confirmed by GST-pulldown in vitro and CoIP in vivo assays, which was enhanced by E2 but not dependent on its presence. Furthermore, the results of the mammalian two-hybrid assays indicated that the binding region of ERα to LRP16 located at the A/B AF-1 functional domain and E2 stimulated the binding of LRP16 to the full-length ERα molecule but not to the A/B region alone.

Conclusion

These results support a role for estrogenically regulated LRP16 as an ERα coactivator, providing a positive feedback regulatory loop for ERα signal transduction. Based on this function of LRP16, we propose that ERα-positive breast cancer patients with high expression of LRP16 might benefit from targeting LRP16 therapy.