Estrogen receptor pathway (ER)

The estrogen receptors are ligand-dependent nuclear hormone receptors that function as transcription factors upon activation by estrogens such as estradiol. There are two main forms—estrogen receptor alpha (ESR1, NR3A1) and beta (ESR2, NR3A2)—which differ in tissue distribution and physiological roles. Upon binding their ligand inside cells—primarily within reproductive organs but also bone, cardiovascular system, brain—they dimerize and regulate gene expression via direct DNA interaction at estrogen response elements or through interactions with other transcriptional regulators. These pathways control cell growth/differentiation/survival across multiple organ systems. Aberrant signaling through these pathways is implicated in various cancers—most notably breast cancer—and other diseases such as osteoporosis and cardiovascular disorders. Drugs targeting these receptors include both agonists for hormone replacement therapy and antagonists/modulators for treatment/prevention of hormone-sensitive cancers.

Other names

EREstrogen nuclear hormone receptorEstradiol receptorNuclear receptor subfamily 3 group A member 1 (for ERα)NR3A1 (for ERα)Nuclear receptor subfamily 3 group A member 2 (for ERβ)NR3A2 (for ERβ)

Agonists bind to the estrogen receptors to activate transcription of estrogen-responsive genes. SERMs act as agonists in some tissues but antagonists in others by modulating coactivator/corepressor recruitment. Antiestrogens block estrogen binding or promote degradation of the receptors.