GFRA4 and atrial fibrillation: The Western blot analyses of cell lysates clearly showed the presence of a single protein band for NRTN (65 kDa), ARTN (24 kDa), PSPN (31 kDa), GFRA2 (46 kDa), GFRA3 (72 kDa), and GFRA4 (50 kDa) in both the NP and the AF cells.