Utrophin and dystrophin-associated glycoproteins in normal and dystrophin deficient cardiac muscle.

In this study, various members of the dystrophin family (dystrophin, the short dystrophin product Dp 71, utrophin and DRP2), and different members of the dystrophin-associated glycoprotein (DAG) complex (beta-dystroglycan, alpha-, beta-, gamma- and delta-sarcoglycans) were localized in bovine cardiac muscle using a battery of specific antibodies. We have established that dystrophin is exclusively associated with beta-dystroglycan and both alpha- and delta-sarcoglycans in cardiac muscle cell membranes. In contrast, utrophin is a specific component of intercalated disks together with beta- and gamma-sarcoglycans, while beta-dystroglycan, alpha- and delta-sarcoglycans are not present. Dp 71 is mainly localized at the T tubule transverse area. In dystrophin deficient cardiac muscle, utrophin and beta-sarcoglycan were observed in intercalated disks and at the sarcolemma of each cardiocyte. Our results revealed that complexes of associated glycoproteins differ in cardiac muscle when associated with dystrophin or utrophin. Despite the described sequence homologies between dystrophin and utrophin, the present results indicate that these proteins have different roles in some specific cardiac cell areas.