PROPERTIES OF GROWTH-RELATED ACETYLCHOLINESTERASE IN A CELL LINE OF FIBROBLASTIC ORIGIN

The presence and regulation of an acetylcholine-hydrolyzing enzyme in high density suspension cultures of WRL-10A fibroblasts [a subline of L-929 mouse fibroblasts] was reported. Its activity increased 100-fold when growth was arrested. Substrate specificity, substrate inhibition, and product identification studies indicate that this enzyme is acetylcholinesterase (AChE, EC 3.1.1.7). Treatment of whole cells with 5 mM diazotized sulfanilic acid revealed that most of the AChE is located on the external surface of the cell membrane. The enzyme is released in the medium at a rate of 0.5 U[units]/h per mg cell protein and within a 24-h period the de novo synthesized and liberated AChE is equivalent to 90% of the activity associated with the cells. No similar synthesis of AChE was found in other L-929 fibroblast sublines examined (L-929, MA; NCTC 929-L; NCTC-2071; L-M), WI-38 human embryonic lung fibroblasts and 3T3 fibroblasts. These and related findings indicating that acetylcholine is also present in high density populations of WRL-10A cells suggest that this unique phenotype may be used profitably in exploring further the relationship between components of the cholinergic system and non-neuronal cell growth.