SCHWANN-CELLS MODIFY EXPRESSION OF ACETYLCHOLINESTERASE AND BUTYRYLCHOLINESTERASE AT RAT NEUROMUSCULAR-JUNCTIONS

Using a monoclonal antibody (6.17) directed against a Schwann antigen, we have shown that Schwann cells synthesize a molecule implicated in a change of expression of synaptic cholinesterases, AChE and BChE, dur ing muscle differentiation. In vitro, during synaptogenesis, the two e nzymes are first present at developing synapses, and addition of Schwa nn cells to muscle-neuron co-cultures induces a disappearance of BChE, leaving only AChE activity as in the adult neuromuscular junction. Th is effect is inhibited by the 6.17 antibody. Thus, a molecule produced by Schwann cells is involved in the maturation of the neuromuscular s ynapse, in addition to the neuronal factors (CGRP, ARIA/heregulin, agr in), which are known to control the synthesis, maturation and accumula tion of acetylcholine receptors and other synaptic components. In addi tion, in vivo, in the newborn rat, butyrylcholinesterase and acetylcho linesterase activities are initially present in equal amounts in the n eural zone, but butyrylcholinesterase levels diminish sharply between 7 and 15 days after birth, the stage at which the synaptic Schwann cel l membrane becomes juxtaposed with the muscle membrane.