Modulation of Erythrocyte Acetylcholinesterase Activity and Its Association with G Protein-Band 3 Interactions

Circulating acetylcholine, substrate of membrane acetylcholinesterase (AChE), is known to enhance the band 3 protein degree of phosphorylation. The purpose of this study was to verify whether the band 3 phosphorylation status is associated with a G protein and whether it is an influent factor on AChE enzyme activity. From blood samples of healthy donors, erythrocyte suspensions were prepared and incubated with AChE substrate (acetylcholine) and inhibitor (velnacrine), along with protein tyrosine kinase (PTK) and tyrosine phosphatase (PTP) inhibitors. AChE activity was determined by spectrophotometry and extract samples were analyzed by western blotting using primary antibodies to different G protein subunits. Our results with phosphorylated band 3 (PTP inhibitor) show an increase in erythrocyte AChE (p < 0.0001). A dephosphorylated band 3 state (PTK inhibitor) shows a significant decrease. We identified a potential linkage of protein subunits Gα_i1/2 and G_β with band 3 protein. Gα_i1/2 and G_β may be linked to the band 3 C-terminal site. Gα_i1/2 is associated with the band 3 N-terminal domain, except for the control and ACh aliquots. G_β is associated with both phosphorylated and dephosphorylated band 3 in the presence of velnacrine. We conclude that an erythrocyte G protein with subunits Gα_i1/2 and G_β is associated with band 3. AChE depends on the degree of band 3 phosphorylation and its association with Gα_i1/2 and G_β.