GRK2 and familial dilated cardiomyopathy: Furthermore, the fraction of cardiomyocytes whose membrane was positively stained by GRK2 was the largest in the TTS group (NC, 2.0 (1.0–5.0)%; TTS, 28.0 (16.5–39.0)%; DCM, 8.5 (4.0–13.3)%, P < 0.001, Fig. 1c).