The Angiotensin AT 2 Receptor: From a Binding Site to a Novel Therapeutic Target.

Discovered more than 30 years ago, the angiotensin AT 2 receptor (AT 2 R) has evolved from a binding site with unknown function to a firmly established major effector within the protective arm of the renin-angiotensin system (RAS) and a target for new drugs in development. The AT 2 R represents an endogenous protective mechanism that can be manipulated in the majority of preclinical models to alleviate lung, renal, cardiovascular, metabolic, cutaneous, and neural diseases as well as cancer. This article is a comprehensive review summarizing our current knowledge of the AT 2 R, from its discovery to its position within the RAS and its overall functions. This is followed by an in-depth look at the characteristics of the AT 2 R, including its structure, intracellular signaling, homo- and heterodimerization, and expression. AT 2 R-selective ligands, from endogenous peptides to synthetic peptides and nonpeptide molecules that are used as research tools, are discussed. Finally, we summarize the known physiological roles of the AT 2 R and its abundant protective effects in multiple experimental disease models and expound on AT 2 R ligands that are undergoing development for clinical use. The present review highlights the controversial aspects and gaps in our knowledge of this receptor and illuminates future perspectives for AT 2 R research. SIGNIFICANCE STATEMENT: The angiotensin AT 2 receptor (AT 2 R) is now regarded as a fully functional and important component of the renin-angiotensin system, with the potential of exerting protective actions in a variety of diseases. This review provides an in-depth view of the AT 2 R, which has progressed from being an enigma to becoming a therapeutic target.