Mineralocorticoid receptor

The mineralocorticoid receptor (or MR, MLR, MCR), also called aldosterone receptor, is officially labelled nuclear receptor subfamily 3, group C, member 2, (NR3C2) and is a receptor with high affinity for mineralocorticoids. It belongs to the steroid hormone receptor family where the ligand diffuses into cells, interacts with the receptor and results in a signal transduction affecting specific gene expression in the nucleus.

The gene for the NR3C2 (located on chromosome 4q31.1-31.2) encodes for the 107 kDa MR protein. MR is expressed in many tissues, such as the kidney, colon, heart, central nerveous system (hippocampus), brown adipose tissue and sweat glands. In epithelial tissues, its activation leads to the expression of proteins regulating ionic and water transports (mainly the sodium epithelial channel or ENaC, Na/K ATPase pump, serum and glucocorticoid induced kinase or SGK1) resulting in the reabsoprtion of sodium, and as a consequence an increase in extracellular volume, increase in blood pressure, and an excretion of potassium to maintain a normal salt concentration in the body.

The receptor is activated by mineralocorticoids such as aldosterone and deoxycorticosterone as well as glucocorticoids, like cortisol and cortison. It also responds to some progestins. Spironolactone and eplerenone are MR receptor antagonists.

Activation of the mineralocorticoid receptor, upon the binding of its ligand aldosterone, results in its translocation to the cell nucleus, homodimerization and binding to hormone response elements present in the promoter of some genes. This results in the complex recruitment of the transcriptional machinery and the transcription into mRNA of the DNA sequence of the activated genes.

Related receptors
Receptors with a similar structure include: the androgen receptor, estrogen receptors, glucocorticoid receptor, progesterone receptor, thyroid hormone receptors, Peroxisome proliferator-activated receptors, retinoic acid receptor, farnesoid x receptor, pregnane x receptor, liver X receptor, vitamin D receptor, retinoid x receptor and the constitutive androstane receptor.