Receptor for angiotensin 1-7 (By similarity). Acts specifically as a functional antagonist of AGTR1 (angiotensin-2 type 1 receptor), although it up-regulates AGTR1 receptor levels. Positive regulation of AGTR1 levels occurs through activation of the G-proteins GNA11 and GNAQ, and stimulation of the protein kinase C signaling cascade. The antagonist effect on AGTR1 function is probably due to AGTR1 being physically altered by MAS1 (By similarity). Interacts with AGTR1. Interacts with FLNA (via filamin repeat 21); increases PKA-mediated phosphorylation of FLNA. Expressed in platelets. Belongs to the G-protein coupled receptor 1 family.