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

In this study, various members of the dystrophin family (dystrophin, the sh ort dystrophin product Dp 71, utrophin and DRP2), and different members of the dystrophin-associated glycoprotein (DAG) complex (beta-dystroglycan, al pha-, beta-, gamma- and delta-sarcoglycans) were localized in bovine cardia c muscle using a battery of specific antibodies. We have established that d ystrophin is exclusively associated with beta-dystroglycan and both alpha- and delta-sarcoglycans in cardiac muscle cell membranes. In contrast, utrop hin is a specific component of intercalated disks together with beta- and g amma-sarcoglycans, while beta-dystroglycan, alpha- and delta-sarcoglycans a re 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. Ou r results revealed that complexes of associated glycoproteins differ in car diac muscle when associated with dystrophin or utrophin. Despite the descri bed sequence homologies between dystrophin and utrophin, the present result s indicate that these proteins have different roles in some specific cardia c cell areas.