Membrane-associated progesterone receptor (MAPR)

The Membrane-associated progesterone receptor (MAPR) family consists of four heme-binding proteins: Progesterone receptor membrane component 1 (PGRMC1), PGRMC2, Neudesin (NENF), and Neuferricin (CYB5D2) [1, 2]. These proteins are characterized by a conserved cytochrome b5-like heme-binding domain and mediate rapid, non-genomic actions of progesterone and other steroids, distinct from classical nuclear receptors [2, 5]. PGRMC1, the most extensively studied member, is a multi-functional protein localized primarily in the endoplasmic reticulum, where it interacts with Cytochrome P450 enzymes to regulate cholesterol biosynthesis, steroidogenesis, and drug metabolism [4, 9]. In oncology, MAPRs are frequently overexpressed and serve as pro-survival factors that promote tumor cell proliferation, invasion, and resistance to apoptosis and chemotherapy [6, 13, 18]. Beyond cancer, they play critical roles in neuroprotection, neural differentiation, and reproductive health [5, 11]. Due to their involvement in diverse pathological processes and their ability to bind small molecules, MAPRs are considered promising therapeutic targets and biomarkers for various cancers and neurological disorders [10, 18].

Other names

PGRMC familyProgesterone receptor membrane component familyCytochrome b5-like heme/steroid-binding domain proteins25-DxHPR6.6IZASigma-2 receptor (historical association)

MAPRs, particularly PGRMC1, function as non-canonical receptors that mediate rapid non-genomic signaling of progesterone through the activation of the MAPK and PI3K/Akt pathways [10, 12]. They also act as heme chaperones and co-activators for various Cytochrome P450 (CYP) enzymes, thereby regulating cholesterol biosynthesis, steroidogenesis, and drug metabolism [2, 9, 14]. In cancer cells, MAPRs promote survival, proliferation, and chemoresistance by inhibiting apoptosis and facilitating membrane trafficking of other receptors [6, 12, 18].