Proteomic identification of Profilin1 as a corepressor of estrogen receptor alpha in MCF7 breast cancer cells

Abstract

Nuclear receptor coregulators play an important role in the transcriptional regulation of nuclear receptors. In the present study, we aimed to identify estrogen receptor α (ERα) interacting proteins in Tamoxifen treated MCF7 cells. Using in vitro GST-pull down assay with ERα ligand-binding domain (ERα-LBD) and MS-based proteomics approach we identified Profilin1 as a novel ERα interacting protein. Profilin1 contains I/LXX/L/H/I amino acid signature motif required for corepressor interaction with ERα. 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 Profilin1 in breast cancer; and here we found that Tamoxifen increases Profilin1 expression in MCF7 cells. Our data demonstrate that over expression of Profilin1 inhibits ERα-mediated transcriptional activation as well as its downstream target genes in ERα positive breast cancer cells MCF7. In addition, Profilin1 overexpression in MCF7 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 ERα interacting protein Profilin1 that serves as a putative corepressor of ERα functions.

Differentially Expressed Proteins in ER+MCF7 and ER-MDA-MB-231 Human Breast Cancer Cells by RhoGDI-α Silencing and Overexpression

“…This protein is involved in cell migration and breast cancer metastasis (Ding et al, 2013). Interestingly, Profilin1 was identified as a corepressor of estrogen receptor alpha in MCF7 breast cancer cells (Kanaujiya et al, 2013). Consistent with our finding, it has been reported that the loss of profilin-1 expression enhances breast cancer cell motility by Ena/VASP proteins (Bae et al, 2009).…”

Profilin 1: Do we have a novel proteome-found biomarker predicting response to anticancer therapy?

“…Thus, in this issue Kanaujiya et al indicated that profilin 1 could be considered as a corepressor of estrogen receptor alpha in hormone-dependent breast carcinoma cells [1]. Proteome-based preclinical data presented here clearly demonstrate that profilin 1 can be proposed for further validation as a biomarker to predict treatment response to tamoxifen in breast carcinoma patients.…”

Estrogen-related Receptor β Reduces the Subnuclear Mobility of Estrogen Receptor α and Suppresses Estrogen-dependent Cellular Function

“…ERR␤ contains this signature motif within the LBD, rather than the NTD. However, the NTD of ERR␤ has at least four signature (I/L)XX(L/H/I) motifs at positions 27-30, 30 -33, 49 -52, and 95-98 (NCBI Protein Database under NCBI accession number NP_001008516.2) that are responsible for co-repressor protein interactions with NRs, including ER␣ (53,65). This sequence is referred to as a co-repressor-nuclear receptor box and may function as a binding surface of ER␣ that causes transrepression, as confirmed for co-repressors.…”