Proteomic identification of P rofilin1 as a corepressor of estrogen receptor alpha in MCF 7 breast cancer cells

• Published in: Proteomics (Weinheim) 2013-07, Vol.13 (14), p.2100-2112
• Main Authors: Kanaujiya, Jitendra Kumar, Lochab, Savita, Kapoor, Isha, Pal, Pooja, Datta, Dipak, Bhatt, Madan LB, Sanyal, Sabyasachi, Behre, Gerhard, Trivedi, Arun Kumar
• Format: Article
• Language: English
• ISSN: 1615-9853; 1615-9861
• DOI: 10.1002/pmic.201200534

Nuclear receptor coregulators play an important role in the transcriptional regulation of nuclear receptors. In the present study, we aimed to identify estrogen receptor [alpha] ( ER [alpha]) interacting proteins in T amoxifen treated MCF 7 cells. Using in vitro GST -pull down assay with ER [alpha] ligand-binding domain ( ER [alpha]- LBD ) and MS -based proteomics approach we identified P rofilin1 as a novel ER [alpha] interacting protein. Profilin1 contains I / LXX / L / H / I amino acid signature motif required for corepressor interaction with ER [alpha]. We show that these two proteins physically interact with each other both in vitro as well as in vivo by GST -pull down and coimmunoprecipitation, respectively. We further show that these two proteins also colocalize together in the nucleus. Previous studies have reported reduced expression of P rofilin1 in breast cancer; and here we found that T amoxifen increases P rofilin1 expression in MCF 7 cells. Our data demonstrate that over expression of P rofilin1 inhibits ER [alpha]-mediated transcriptional activation as well as its downstream target genes in ER [alpha] positive breast cancer cells MCF 7. In addition, P rofilin1 overexpression in MCF 7 cells leads to inhibition of cell proliferation that apparently is due to enhanced apoptosis. In nutshell, these data indicate that MS -based proteomics approach identifies a novel ER [alpha] interacting protein P rofilin1 that serves as a putative corepressor of ER [alpha] functions.