AT 1 R-AT 2 R-RXFP1 functional crosstalk: implications for the therapeutic targeting of fibrosis.

Class A rhodopsin-like G protein-coupled receptors (GPCRs) are by far the largest class of GPCRs, and are integral membrane proteins that are used by various cells to convert extracellular signals into intracellular responses. Initially, class A GPCRs were believed to function as monomers, but a growing body of evidence has emerged to suggest that these receptors can function as homo- and heterodimers, and undergo functional crosstalk to influence the actions of agonists or antagonists acting at each receptor. This review will focus on the angiotensin type 1 (AT 1 ) and type 2 (AT 2 ) receptors, as well as relaxin family peptide receptor 1 (RXFP1); which have their unique characteristics, but have been demonstrated to undergo some level of interaction when appropriately co-expressed, that influences the function of each receptor. In particular, this receptor functional crosstalk will be discussed in the context of fibrosis, the tissue scarring that results from a failed wound-healing response to injury, and which is a hallmark of chronic disease and related organ dysfunction.