GAL-ALPHA-1-]4GAL-GLYCANS ARE EXPRESSED ON MYOFIBRILLAR ASSOCIATED PROTEINS

There is evidence that glycans carrying terminal galactose residues ar e differently expressed in the sarcoplasm of different muscle fiber ty pes. In this study monoclonal antibodies directed against P blood grou p antigens P-k: Gal alpha 1-4Gal beta 1-4Glc beta- and P-1: Gal alpha 1-4Gal beta 1-4GlcNAc beta- were used to detect terminal alpha-galacto sylated glycoconjugates on muscle proteins. Electrotransfer of protein s, extracted from human masseter and biceps muscles, to nitrocellulose after polyacrylamide gel electrophoresis (PAGE) and incubation with a nti-P-k (CD77) consistently showed two bands with apparent molecular w eights of 66 kDa and 64 kDa. In fresh frozen muscle sections from some humans there was endothelial reaction with anti-CD77 in capillaries, venules and veins but not in arterioles and arteries. In muscle sample s from other humans there was no staining of endothelial cells. Formal in-fixed human muscle displayed a CD77 reaction with highest accumulat ion of reaction product at the periphery of the fibers. This may be ex plained by the presence of P-k glycoconjugates on intermediate filamen ts in muscle fibers. In preparations of cat masseter muscle proteins t he antibodies against P1Pk antigens reacted with a 170 kDa and a 55 kD a band while in preparations of cat biceps brachii only a 55 kDa band was reactive. The specificities of the antibodies were investigated by fluorescence-activated cell sorter (FACS), alpha- and beta-galactosid ase digestion and inhibitory sugars. This study indicates that glycans carrying Gal alpha 1-4Gal beta 1- epitopes are expressed on myofibril lar associated proteins.