Increased Butyrylcholinesterase Levels in Microsomal Membranes of Dystrophic Lama2dy Mouse Muscle

The proportions and the glycosylation of butyrylcholinesterase (BuChE) forms in vesicles rich in sarcoplasmic reticulum from normal (NMV) and dystrophic (DMV) muscle were analyzed, using merosin-deficient dystrophic mice. BuChE activity in DMV was two- to threefold that in NMV. Globular amphiphilic G1A, G2A, and G4A and hydrophilic G4H BuChE forms were identified in NMV and DMV. The amount of G2A forms increased sevenfold in DMV, and the other forms increased about twofold. The higher BuChE level in DMV might reflect a maturational defect, with dystrophy preventing the down-regulation of BuChE with muscle development. About half of G1A, G2A, and G4H BuChE forms in NMV or DMV bound to Lens culinaris agglutinin (LCA), a higher fraction to wheat germ agglutinin (WGA), and little to Ricinus communis agglutinin (RCA). Most of the G4A forms in NMV or DMV bound to LCA or WGA; those from NMV failed to bind to RCA, whereas most of the variants in DMV bound to it, suggesting that the excess of tetramers in DMV is mainly RCA-reactive. The differential interaction of lectins with BuChE components from muscle microsomes, serum, and nerves confirmed that the microsomal BuChE was muscle-intrinsic. The results provide clues regarding the alterations that dystrophy produces in the biosynthesis of BuChE forms in muscle.