The mineralocorticoid receptor (MR) belongs to the steroid receptor superfamily together with receptors for progesterone, estrogens, androgens and glucocorticoids. In classical target tissues like epithelia of the kidney, colon, sweat and salivary glands, the MR is activated by aldosterone and subsequently increases sodium and water reabsorption, enhanced potassium secretion and thereby contributes to the maintenance of blood pressure.  The MR is expressed abundantly in the limbic brain where it surprisingly was found to mediate predominantly the action of the naturally occurring glucocorticoids cortisol and corticosterone. MR is expressed in cells of nonepithelial tissue like heart and vasculature, where it can lead to pathophysiological changes initiated by inflammation or an altered micromilieu followed by fibrosis, hypertrophy and remodeling. There is an intense cross-talk between MR outside the nucleus and other signaling components that is crucial for its non-canonical actions. These interactions include different membrane receptors, namely receptor tyrosine kinases and the angiotensin 1 receptor. Activation of these receptors occurs not only by binding of ligands but also by a mechanism called transactivation, the receptor tyrosine kinases considered are epidermal growth factor receptor (EGFR), insulin receptor (IR)/insulin-like growth factor receptor (IGF-1 receptor), platelet-derived growth factor receptor (PDGFR) and vascular endothelial growth factor receptor (VEGFR).

References

1.Meinel S, et al. Steroids. 2014;91:3–10.