Calmodulin Lobes Facilitate Dimerization and Activation of Estrogen Receptor-α

J Biol Chem. 2017 Mar 17;292(11):4614-4622. doi: 10.1074/jbc.M116.754804. Epub 2017 Feb 7.

Abstract

Estrogen receptor α (ER-α) is a nuclear hormone receptor that controls selected genes, thereby regulating proliferation and differentiation of target tissues, such as breast. Gene expression controlled by ER-α is modulated by Ca2+ via calmodulin (CaM). Here we present the NMR structure of Ca2+-CaM bound to two molecules of ER-α (residues 287-305). The two lobes of CaM bind to the same site on two separate ER-α molecules (residues 292, 296, 299, 302, and 303), which explains why CaM binds two molecules of ER-α in a 1:2 complex and stabilizes ER-α dimerization. Exposed glutamate residues in CaM (Glu-11, Glu-14, Glu-84, and Glu-87) form salt bridges with key lysine residues in ER-α (Lys-299, Lys-302, and Lys-303), which is likely to prevent ubiquitination at these sites and inhibit degradation of ER-α. Transfection of cells with full-length CaM slightly increased the ability of estrogen to enhance transcriptional activation by ER-α of endogenous estrogen-responsive genes. By contrast, expression of either the N- or C-lobe of CaM abrogated estrogen-stimulated transcription of the estrogen responsive genes pS2 and progesterone receptor. These data suggest that CaM-induced dimerization of ER-α is required for estrogen-stimulated transcriptional activation by the receptor. In light of the critical role of ER-α in breast carcinoma, our data suggest that small molecules that selectively disrupt the interaction of ER-α with CaM may be useful in the therapy of breast carcinoma.

Keywords: breast cancer; calmodulin (CaM); estrogen receptor; receptor structure-function; signaling; structure-function; transcription.

MeSH terms

  • Calmodulin / chemistry
  • Calmodulin / genetics
  • Calmodulin / metabolism*
  • Estrogen Receptor alpha / chemistry
  • Estrogen Receptor alpha / genetics
  • Estrogen Receptor alpha / metabolism*
  • Estrogens / metabolism
  • HEK293 Cells
  • Humans
  • MCF-7 Cells
  • Molecular Docking Simulation
  • Protein Conformation
  • Protein Multimerization*
  • Transcriptional Activation
  • Transfection

Substances

  • Calmodulin
  • ESR1 protein, human
  • Estrogen Receptor alpha
  • Estrogens

Associated data

  • PDB/5T0X