GLYCYL-L-GLUTAMINE STIMULATES THE ACCUMULATION OF A12 ACETYLCHOLINESTERASE BUT NOT OF NICOTINIC ACETYLCHOLINE-RECEPTORS IN QUAIL EMBRYONIC MYOTUBES BY A CYCLIC AMP-INDEPENDENT MECHANISM

Myotubes prepared from the Japanese quail embryo at 9 days gestation were cultivated in the presence of glycyl‐L‐glutamine (Gly‐Gln, β‐endorphin C‐terminal dipeptide) or glycyl‐glutamic acid (Gly‐Glu), and changes in the activity of acetylcholinesterase (AChE) molecular forms and binding of 125I‐α‐bungarotoxin (αBGT) to cell surface nicotinic acetylcholine receptors were measured. The A12 oligomer was the major form of AChE in the cultures. The activity of all molecular forms of the enzyme was increased in the presence of Gly‐Gln, but Gly‐Glu did not alter AChE activity. In cells infected with the temperature‐sensitive mutant, La31C, of Rous sarcoma virus (ts‐RSV) and transferred to the nonpermissive temperature, the A12 form of AChE was absent, but its activity could be induced following exposure of the cells to Gly‐Gln. When cells treated in this way were incubated in the presence of collagenase, there was a small but significant loss of A12 AChE activity, indicating that Gly‐Gln stimulated the activity of a pool of this oligomer which was mainly but not entirely intracellular. Neither Gly‐Gln nor Gly‐Glu influenced 125I‐αBGT binding after exposure of the cells to the peptides for any duration. Neither Gly‐Gln nor Gly‐Glu influenced the accumulation of cyclic AMP in the cultures. β‐Endorphin is one of a family of peptides that coexist transiently with acetylcholine in lower motoneurones of vertebrates in the perinatal period. This report provides evidence for the selective trophic activity of one of its derivatives toward the postsynaptic cholinergic system in avian muscle cells. Copyright © 1990, Wiley Blackwell. All rights reserved