The effect of denervation on mammalian sarcolemmal proteins and glycoproteins

The effects of surgical denervation on proteins and glycoproteins of sarcolemmal membranes have been investigated using sarcolemmal fractions prepared from mixed rat muscles. Denervation did not cause any gross change in the protein composition but some consistent quantitative changes were detected. Denervation caused a significant increase in the binding of 125I-labeled concanavalin A (ConA), Ricinus communis agglutinin (RCA120), and wheat germ agglutinin (WGA) to intact membranes. This increased binding appears to be brought about by two mechanisms: the synthesis of more binding-sites with the same apparent KD and the unmasking of previously cryptic binding sites. The activity of sialyl-, galactosyl-, and N-acetylglucosaminyltransferases in the sarcolemmal fractions increased, whereas fucosyl-glycoprotein-transferase activity decreased following denervation. Kinetic analysis of the sialyl- and galactosyltransferase activities showed that the change was due to an increase in Vmax with no change in Km. These results are consistent with an increase in the turnover of sarcolemmal glycoproteins following denervation.