Calreticulin and the Heart.

Calreticulin is an endoplasmic Ca 2+ binding protein and molecular chaperone. As a cardiac embryonic gene, calreticulin is essential for heart development. The protein supports Ca 2+ -dependent signaling events that are critical to cardiomyocyte differentiation and cardiogenesis. The increased expression of calreticulin and endoplasmic reticulum/sarcoplasmic reticulum Ca 2+ capacity produces cardiomyocytes with enhanced efficiency, and detrimental mechanical stretching of cardiac fibroblasts, leading to cardiac pathology. Deletion of the calreticulin gene in adult cardiomyocytes results in left ventricle dilation, an impaired electrocardiogram, and heart failure. These observations indicate that a well-adjusted endoplasmic reticulum and calreticulin-dependent Ca 2+ pool in cardiomyocytes are critical for the maintenance of proper cardiac function.