ER alpha17p is a GPER inverse agonist, corresponding to residues 295-311 of the human estrogen receptor alpha (ER alpha). This 295-311 region is targeted by post-translational modifications and is involved in the recruitment of Ca2+-calmodulin, Hsp70 and the ubiquitin-protein isopeptide ligase E6-associated protein (E6AP), an E3 ligase catalyzing the ubiquitination of ER alpha9, as well as associating with ER alpha. ER alpha17p triggers membrane-initiated pro apoptotic events in both ER alpha-positive and -negative breast cancer cell lines with a preference for ER alpha-positive cancer cells, and induces a decrease of more than 50% of the size of triple-negative breast tumour xenografts. ER alpha17p also exerts GPER mediated anti-hyperalgesic and anti-inflammatory actions in mice.
