Effect of denervation on sarcolemmal proteins and glycoproteins of fast and slow mammalian skeletal muscle.

We compared the protein and glycoprotein composition of a sarcolemmal membrane fraction isolated from normal and denervated rat extensor digitorum longus (EDL) and soleus muscles. Membranes from EDL and soleus muscles showed significantly different protein compositions. A relatively small number of glycoproteins, which were all minor proteins, accounted for the majority of concanavalin A (ConA) and Ricinus communis agglutinin (RCA120) binding. These glycoproteins appear to be common to EDL and soleus but bound different relative amounts of lectin in the two muscles. A large proportion of the ConA binding sites in EDL, but not soleus, were cryptic (not accessible by ConA unless the membrane structure was disrupted). Denervation had a differential effect on sarcolemma from the two muscles with EDL exhibiting large changes and soleus changing little if at all. Several major proteins changed their relative concentrations after denervation and the relative amount of RCA120 bound to the major glycoproteins also changed. The major ConA-binding glycoproteins did not change in either membrane but denervation resulted in the exposure of most of the cryptic ConA-binding sites in EDL membranes. Endogenous sialyl- and galactosyl-transferase activities in the membrane fractions significantly increased in EDL, but did not change in soleus, suggesting that the turnover of the glycoproteins is increased in EDL after denervation.