Estrogen receptor alpha (or Estrogen receptor beta) (ERα (for estrogen receptor alpha), ERβ (for estrogen receptor beta))

The **estrogen receptors**, primarily **ERα and ERβ**, are ligand-dependent nuclear hormone receptors that mediate most biological effects of endogenous estrogens such as estradiol. Upon ligand binding at their C-terminal ligand-binding domain, they undergo conformational changes allowing dimerization and subsequent DNA binding at specific sequences called *estrogen response elements* within target genes. This leads to recruitment of coactivators or corepressors via LXXLL motifs on interacting proteins,[1] modulating gene transcription involved in cell growth, differentiation, reproductive tissue development/function,[2] bone homeostasis,[7] cardiovascular health,[2] neural function,[2], among others. There are multiple isoforms due to alternative splicing; both full-length functional forms have similar domain structures but differ somewhat in tissue distribution and regulatory roles.[2][7] Deregulation or overexpression—especially of ERα—is strongly implicated in several cancers including ~80% of breast carcinomas.[7] Drugs targeting these receptors form a cornerstone of endocrine therapy for hormone-responsive cancers.[4] A third class—the membrane-associated GPCR-type *G-protein coupled estrogen receptor* (**GPER1/GPR30**)—also binds estrogens but mediates rapid non-genomic signaling distinct from classical nuclear actions.[2]

Other names

Estrogen nuclear hormone receptorESR1 (gene for ERα)ESR2 (gene for ERβ)Oestrogen receptorGPER1 or GPR30 (G protein-coupled estrogen receptor)

Drugs targeting the estrogen receptors act by: - Agonism—activating the transcriptional activity of the ERs when bound to endogenous or synthetic estrogens. - Antagonism—blocking coactivator recruitment or DNA binding when bound by antagonists like fulvestrant. - Modulation—SERMs can act as agonists in some tissues and antagonists in others depending on coregulator expression patterns.[1][6]