Acetylcholinesterase activation of peritoneal macrophages is independent of catalytic activity

Abstract

1. In diverse tissues, acetylcholinesterase appears to play a critical role in the functional state of cells completely dependent of cholinergic transmission. However, very little is known about the mechanisms and actual molecular structures mediating the fundamental interactions between this protein and the cellular membrane. 2. In this study, peritoneal macrophages were used as a model system to study the possible interaction between acetylcholinesterase, acting in a non-cholinergic capacity, and the cellular membrane. 3. When acetylcholinesterase was incubated with macrophages harvested from rat peritoneum, the rate of oxygen consumption was increased in a concentration-dependent manner that was independent of mitochondrial block with sodium cyanide. Furthermore, heat inactivation of enzymatic activity or application of BW 284C51 at a concentration which totally blocks catalytic activity did not eliminate the effect. 4. In contrast, incubation with bovine serum albumin or butyrylcholinesterase actually retarded oxygen consumption. 5. The effect of acetylcholinesterase depended on the presence of divalent cations and was inhibited by mannan and D-mannose, but not D-galactose. It is concluded that acetylcholinesterase can induce a "respiratory burst" in macrophages independent of its conventional catalytic site but involving either the mannose receptor of the monocyte-derived macrophage or a possible sugar binding site on acetylcholinesterase itself.

Toxic effects of acetylcholinesterase on neuronal and glial-like cells in vitro

“…Neither an inhibitor blocking its active site nor heat inactivation of the enzyme modified its cytotoxic effect. Effects independent of the catalytic activity of AChE have described as non-cholinergic actions of the enzyme, which include cellular effects such as the induction of neurite outgrowth, 45 respiratory bursts in macrophages and behavioral changes in rats 11,[46][47][48] Oligonucleosomal DNA degradation is one of the hallmarks of apoptotic 42 cell death. Our results using the TUNEL technique which detects DNA fragmentation in situ, strongly suggest that for both neuronal and glial-like cells, apoptotic cell death is at least one of the mechanisms by which AChE exerts its toxic effects.…”

“…AChE could be internalized by cells in a temperature-dependent manner, as occurs with exogenously-applied AChE in the dopaminergic neurons of the substantia nigra. 46 On the other hand, it has been suggested that the respiratory burst induced by AChE in peritoneal macrophages is likely to be mediated by the macrophage mannose-fucose receptor, 47,48 Future studies are planned in order to examine the possibility that AChE toxicity may be mediated via endocytosis.…”

Regulation of Cholinesterase Gene Expression Affects Neuronal Differentiation as Revealed by Transfection Studies on Reaggregating Embryonic Chicken Retinal Cells

“…A role for non-catalytic parts of cholinesterase proteins has been suggested repeatedly (for references see Introduction). Several studies have shown that neurite growth in various in vitro systems is modulated by cholinesterases, the mechanism being nonenzymatic Klegeris et al, 1994;Jones et aZ., 1995;Small and Reed, 1995). By microinjecting various human AChE DNA constructs into cultured glioma cells, Karpel et al (1996) have reported that variable expression levels and splicing alternatives of the AChE gene correlate with specific glial differentiation modes.…”

“…Appropriate in vitro systems have been applied to show that AChE indeed can regulate neurite differentiation by an enzyme-independent mechanism Klegeris et al, 1994: Jones rt cd., 1995Small and Reed, 1995). As another in v i m system, we reaggregated retinal cells of 6-day-old chick embryos in rotation culture, which then formed three-dimensional retina-like spheres.…”

Donepezil prevents RANK-induced bone loss via inhibition of osteoclast differentiation by downregulating acetylcholinesterase

“…Axonal and neurite growth is regulated by AChE without hydrolytic activity in chick nerve cells [11] , and the neurite outgrowth-promoting effect of AChE was associated with a non-catalytic mechanism in chick sympathetic neurons [7] . The rate of oxygen consumption in macrophages is increased by stimulating AChE independent of catalytic activity [12] .…”