IQGAP1 Binds To Estrogen Receptor-{alpha} and Modulates Its Function [Signal Transduction]

February 18th, 2014 by Erdemir, H. H., Li, Z., Sacks, D. B.

The estrogen receptor (ER) is a steroid hormone receptor that acts as a transcription factor, modulating genes that regulate a vast range of cellular functions. IQGAP1 interacts with several signaling proteins, cytoskeletal components and transmembrane receptors, thereby serving as a scaffold to integrate signaling pathways. Both estrogen receptor-α (ERα) and IQGAP1 contribute to breast cancer. In this study we report that IQGAP1 binds ERα and ERβ. In vitro analysis with pure proteins reveals a direct interaction between IQGAP1 and ERα Investigation with multiple short fragments of each protein showed that ERα binds to the IQ domain of IQGAP1, while the hinge region of ERα is responsible for binding IQGAP1. In addition, IQGAP1 and ERα co-immunoprecipitate from cells and the association is modulated by estradiol (E2). The interaction has functional effects. Knockdown of endogenous IQGAP1 attenuates the ability of E2 to induce transcription of the estrogen responsive genes pS2, progesterone receptor and cyclin D1. These data reveal that IQGAP1 binds to ERα and modulates its transcriptional function, suggesting that IQGAP1 might be a target for therapy in patients with breast carcinoma.