Lipid rafts of mouse liver contain nonextended and extended acetylcholinesterase variants along with M3 muscarinic receptors

Abstract

The observation of acetylcholinesterase (AChE) type H (AChE), which is the predominant AChE variant in visceral organs and immune cells, in lipid rafts of muscle supports functional reasons for the raft targeting of glypiated AChE The search for these reasons revealed that liver AChE activity is mostly confined to rafts and that the liver is able to make N-extended AChE variants and target them to rafts. These results prompted us to test whether AChE and muscarinic receptors existed in the same raft. Isolation of flotillin-2-rich raft fractions by their buoyancy in sucrose gradients, followed by immunoadsorption and matrix-assisted laser desorption ionization-time of flight-mass spectrometry application, gave the following results: 1) most hepatic AChE activity emanates from AChE-H mRNA, and its product, glypiated AChE, accumulates in rafts; 2) N-extended N-AChE readthrough variant, nonglypiated N-AChE, and N-AChE tailed variant were all identified in liver rafts; and 3) M3 AChRs were observed in rafts, and coprecipitation of raft-confined N-AChE and M3 receptors by using anti-M3 antibodies showed that enzyme and receptor reside in the same raft unit. A raft domain that harbors tightly packed muscarinic receptor and AChE may represent a molecular device that, by means of which, the intensity and duration of cholinergic inputs are regulated.-Montenegro, M. F., Cabezas-Herrera, J., Campoy, F. J., Muñoz-Delgado, E., Vidal, C. J. Lipid rafts of mouse liver contain nonextended and extended acetylcholinesterase variants along with M3 muscarinic receptors.

Cholesterol and the Safety Factor for Neuromuscular Transmission

“…AChE mainly resides in synaptic cleft, but the pool of AChE is located in association with lipid rafts through a GPI anchor [82]. Close distribution of raft-linked AChE to plasma membrane enriched with the receptors (e.g., M3 muscarinic receptors) could be important for control local levels of ACh near the receptors [83]. Accordingly, presence of cholesterol-rich microdomains may control sensitivity of feedback mechanisms which regulate ACh release from nerve terminals.…”

Nerve Growth Factor: A Dual Activator of Noradrenergic and Cholinergic Systems of the Rat Ovary

“…Therefore, to determine if the decrease in ovarian ACh levels is mediated by an increase in AChE, we analyzed its levels by western blot. In this sense, while AChE-R has a size of approximately 55 kDa ( 33 – 35 ), AChE-S has several posttranslational modifications, and its size could be 70, 60, and even 55 kDa ( 33 – 36 ). Figure 2 shows the western blot analysis results for AChE, and we found two main bands at 70 kDa and 55 kD ( Figure 2A ).…”

“…In studies involving mice and humans, AChE-S has shown different molecular weights (55, 60, and 70 kDa) depending on posttranslational modifications ( 33 – 36 ). The molecular size of AChE-R was found to be 55 kDa in studies involving mice and humans ( 33 – 35 ). When we analyzed AChE by western blotting after NGF stimulation and found a 2-fold increase only in the 55 kDa-isoform.…”

“…It is known that they have different characteristics and distributions: isoform S is able to form multimers that join to anchoring proteins and bind them to the synaptic membrane, while AChE-R cannot form it and once secreted, it is soluble. In studies involving mice and humans, AChE-S has shown different molecular weights (55, 60, and 70 kDa) depending on posttranslational modifications (33)(34)(35)(36). The molecular size of AChE-R was found to be 55 kDa in studies involving mice and humans (33)(34)(35).…”