Acetylcholinesterase (AChE) is well-known for its cholinergic functions in the nervous system; however, this enzyme is also found in other tissues where its function is still not understood. AChE is synthesized through alternative splicing as splicing variants, with isoforms including read-through (AChER), tailed (AChET) and hydrophobic (AChEH). In human erythrocytes, AChEH is a glycophosphatidylinositol-linked dimer on the plasma membrane. Three N-linked glycosylation sites have been identified in the catalytic domain of human AChE. Here, we investigate the roles of glycosylation in assembly and trafficking of human AChEH. In transfected fibroblasts, expression of AChEH was able to mimic the function of the dimeric form of AChE on the erythrocyte membrane. A glycan-depleted form was constructed by site-directed mutagenesis. By comparison with the wild-type AChEH, the mutant had a much lower enzymatic activity and a much higher Km value. In addition, the mutant was dimerized in the endoplasmic reticulum, but was not trafficked to the Golgi apparatus. The results suggest that the glycosylation may affect AChEH enzymatic activity and trafficking, but not dimer formation. The present findings indicate the significance of N-glycosylation in controlling the biosynthesis of the AChEH dimer form.
Structured digital abstract