Estrogen receptor alpha 36 (ERα-36) (ERα-36)

Estrogen receptor alpha 36 (ERα-36) is a 36-kDa splice variant of the classical estrogen receptor alpha (ERα-66) that lacks the transcriptional activation domains AF-1 and AF-2 (Wang et al., 2006). Unlike the full-length receptor, ERα-36 is primarily localized to the plasma membrane and cytoplasm, where it mediates rapid, non-genomic estrogen signaling rather than traditional nuclear transcription. It plays a critical role in cancer progression by activating the PI3K/AKT and MAPK/ERK pathways, which in turn can trigger the stabilization and nuclear translocation of β-catenin to promote cell proliferation and stemness (Yin et al., 2014). In clinical contexts, high expression of ERα-36 is strongly associated with resistance to conventional endocrine therapies like tamoxifen, as tamoxifen can paradoxically act as an agonist for this specific variant (Zhang et al., 2011). Consequently, ERα-36 is an emerging therapeutic target and a predictive biomarker for treatment response in various malignancies, including breast, gastric, and hepatic cancers. Research into small molecules like Icaritin has shown promise in specifically modulating ERα-36 to overcome endocrine resistance (Fan et al., 2019).

Other names

ER-alpha36hER-alpha3636-kDa variant of estrogen receptor alphaESR1 variantER-α36

ERα-36 functions as a dominant-negative inhibitor of genomic estrogen signaling mediated by ERα-66 while simultaneously activating rapid non-genomic pathways such as MAPK/ERK and PI3K/AKT/β-catenin signaling upon binding to estrogen or certain anti-estrogens (Wang et al., 2006; Yin et al., 2014).