MAS1 (MAS proto-oncogene) is a G protein-coupled receptor for angiotensin (1-7), an active RAS (renin-angiotensin system) heptapepide that functions as a vasodilator agent in cardiovascular organs. MAS1 is a functional antagonist of angiotensin-2 type 1 receptor (AGTR1), which it also upregulates. This occurs through G-protein GNA11 and GNAQ activation and through stimulation of the protein kinase C signaling cascade. MAS1 may have neuroprotective effects via Angiotensin (1-7) binding and loss of this receptor increases cerebral inflammation in mice. Furthermore, induced activation of MAS1 through angiotensin (1-7) treatment therapies seems to relieve bone pain in some cancer patients. In immunohistochemistry, MAS1 is has membranous positivity primarily in the cerebral cortex, hippocampus and amygdala in the brain, and it also has some expression in reproductive tissues, immune tissues, and blood. References: Br J Pharmacol. 2017 May; 174(9): 737–753, PMID: 28194766