Estrogen receptor alpha 46 kDa isoform (ERα46)

The Estrogen receptor alpha 46 kDa isoform (ERα46) is a naturally occurring, truncated variant of the full-length 66 kDa estrogen receptor alpha (ERα66), lacking the N-terminal A/B domain which contains the transactivation function-1 (AF-1) (Flouriot et al., 2000, EMBO J). It is frequently localized to the plasma membrane (mERα) via palmitoylation, where it mediates rapid, non-genomic signaling pathways such as the activation of endothelial nitric oxide synthase (eNOS) and the PI3K/Akt and MAPK/ERK cascades (Li et al., 2003, PNAS; Simoncini et al., 2000, Nature). In the nucleus, ERα46 can form heterodimers with ERα66, acting as a dominant-negative inhibitor of AF-1-dependent gene transcription while retaining AF-2-dependent activity (Penot et al., 2005, Mol Cell Biol). This isoform is particularly significant in the cardiovascular system, where it contributes to the protective effects of estrogen on the endothelium (Chambliss et al., 2002, Circ Res). In oncology, ERα46 is expressed in various breast cancer cell lines and tissues, and its ratio relative to ERα66 may influence the effectiveness of endocrine therapies like tamoxifen and fulvestrant (Figtree et al., 2003, J Biol Chem). Because it lacks the AF-1 domain, drugs that specifically target or bypass this domain may show differential efficacy in cells where ERα46 is the predominant isoform.

Other names

ER46mERα-ER46ESR1 isoform 2hERα46Truncated estrogen receptor alphaMembrane estrogen receptor alpha 46

ERα46 lacks the AF-1 domain, making its genomic activity dependent on the AF-2 domain. It primarily functions by mediating rapid non-genomic signaling at the plasma membrane through the activation of G proteins and downstream kinases like PI3K and MAPK, and by competitively inhibiting the AF-1 activity of the full-length ERα66 isoform.