Anti-estrogen binding site (AEBS)

The anti-estrogen binding site (AEBS) is a high-affinity, microsomal protein complex located in the endoplasmic reticulum that is distinct from the classical estrogen receptor (PMID: 12161439). It is primarily composed of the enzyme 3-beta-hydroxysterol-delta-8,delta-7-isomerase (also known as the emopamil binding protein, EBP) and is essential for the cholesterol biosynthetic pathway, where it catalyzes the conversion of 8(9)-cholestenol to lathosterol (PMID: 12538608). Beyond its metabolic role, the AEBS is a key mediator of the non-genomic, anti-tumor effects of selective estrogen receptor modulators (SERMs) like tamoxifen. When targeted by drugs, the AEBS triggers the accumulation of specific sterols and reactive oxygen species, leading to cell differentiation or programmed cell death in various cancer types, including breast and colon cancer (PMID: 15308670). Furthermore, the AEBS is involved in the production of dendrogenin A, a natural mammalian sterol metabolite with potent tumor-suppressive and neuroprotective properties that is often depleted in malignant cells (PMID: 24391464). Consequently, the AEBS represents a significant therapeutic target for both oncology and neurodegenerative disorders.

Other names

Microsomal anti-estrogen binding siteTamoxifen binding siteEmopamil binding protein complexEBP complexD8-D7 sterol isomerase complex

Ligands bind to the AEBS complex, specifically inhibiting the 3-beta-hydroxysterol-delta-8,delta-7-isomerase (EBP) activity, which leads to the accumulation of sterol precursors, induction of reactive oxygen species, and subsequent cell cycle arrest or differentiation.