Spectrin extractability from erythrocyte in Duchenne muscular dystrophies and the effect of proteases on erythrocyte ghosts.

We studied the erythrocyte membrane proteins from patients with Duchenne muscular dystrophy (DMD) using SDS-polyacrylamide gel electrophoresis. Our observations were the following: (1) The electrophoretic densitogram of freshly prepared DMD-ghosts was similar to that of controls. After the extraction of spectrin from ghosts with 1 mmol/l EDTA, pH 8.0, the unextractable spectrin remained more firmly bound in the DMD ghost residues than in controls. Extractability of spectrin from DMD ghosts was decreased about 20%. In addition, several minor bands were detected between spectrin and Band 3 in the DMD ghost residues (treated ghosts). (2) Ca2+-activated, neutral protease reacted more effectively with spectrin of DMD ghosts and ATP-depleted ghosts than with that of controls. (3) Erythrocyte actin (Band 5) of DMD ghosts was more fragile than that of controls and of ATP-depleted actin in the EDTA extracts. Gradually, partial degradation of actin was observed for three weeks at 4 degrees C. (4) The intracellular ATP level and the activities of membrane-bound (Mg2+--Ca2+) ATPases in DMD erythrocytes were unchanged. We suggest that spectrin from DMD ghosts as well as actin may be subject to increased degradation.