Membrane progesterone receptor

Membrane progesterone receptors (mPRs) are a group of cell surface receptors and membrane steroid receptors belonging to the progestin and adipoQ receptor (PAQR) family which bind the endogenous progestogen and neurosteroid progesterone, as well as the neurosteroid allopregnanolone.^[1][2] Unlike the progesterone receptor (PR), a nuclear receptor which mediates its effects via genomic mechanisms, mPRs are cell surface receptors which rapidly alter cell signaling via modulation of intracellular signaling cascades.^[1] The mPRs mediate important physiological functions in male and female reproductive tracts, liver, neuroendocrine tissues, and the immune system as well as in breast and ovarian cancer.

The mPRs appear to be involved in the neuroprotective and antigonadotropic effects of progesterone and allopregnanolone.^[1][2] The progesterone active metabolites 5α-dihydroprogesterone, also a progestogen, and allopregnanolone, which are positive allosteric modulators of the GABA_A receptor, have been found to rapidly influence sexual receptivity and behavior in mice, actions that are GABA_A receptor-dependent.^[3][4]

These proteins are classified into three groups known as mPRα (PAQR7), mPRβ (PAQR8), mPRγ (PAQR5), mPRδ (PAQR6), and mPRϵ (PAQR9).