The cleaved N terminus of GPR56 associates with the 7TM region of the receptor. A, lysates from HEK-293 cells transfected with empty vector (EV) or GPR56 were probed with anti-GPR56 C-terminal antibody. B, the same antibody was used to immunoprecipitate (IP) the GPR56 7TM region from solubilized lysates. The IP samples were then probed with the GPR56 N-terminal antibody (n = 3). C, rat kidney tissue was solubilized and probed for GPR56 expression using the GPR56 C-terminal antibody. The mock lane (MK) was loaded with buffer only. D, IP was performed with the GPR56 C-terminal antibody, and IP samples were probed with the GPR56 N-terminal antibody. Mock (MK) in this case represents the IP protocol performed with beads but no antibody (n = 3). WB, Western blotting.