Acetylcholinesterase of Mammalian Neuromuscular Junctions: Presence of Tailed Asymmetric Acetylcholinesterase in Synaptic Basal Lamina and Sarcolemma

A sarcolemma-rich fraction can be isolated after subcellular fractionation of mouse intercostal muscles by sedimentation on a discontinuous sucrose gradient. The quantitative recovery of the acetylcholine receptor in this fraction is about 50%, which indicates the presence of a high proportion of po...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1983-11, Vol.80 (21), p.6698-6702
Main Authors: Dreyfus, Patrick A., Rieger, François, Pinçon-Raymond, Martine
Format: Article
Language:English
Subjects:
acetylcholinesterase
Acetylcholinesterase - metabolism
Animals
Basement membrane
Basement Membrane - enzymology
Cell membranes
Centrifugation
Detergents
Extracellular matrix
Extracellular Matrix - enzymology
Fractionation
Macromolecular Substances
Matrix materials
Mice
microsomes
Motor Endplate - enzymology
Neuromuscular Junction - enzymology
neuromuscular junctions
Salts
Sarcolemma - enzymology
Solubility
Solubilization
Subcellular fractions
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Summary:A sarcolemma-rich fraction can be isolated after subcellular fractionation of mouse intercostal muscles by sedimentation on a discontinuous sucrose gradient. The quantitative recovery of the acetylcholine receptor in this fraction is about 50%, which indicates the presence of a high proportion of postsynaptic membranes. Acetylcholinesterase (AcChoEase; EC 3.1.1.7) is found mainly in three different layers: the top layer, which contains soluble AcChoEase, the intermediate layer (fraction A), and the last, AcChoR-rich, layer (fraction C). The relative proportions of the molecular forms of AcChoEase are different in the three layers. The ``16S'' AcChoEase is in a higher proportion in both types of membrane fractions (A and C) compared to soluble AcChoEase. Both total AcChoEase and 16S AcChoEase are enriched in the A and C fractions. In the C fraction, the sequential use of homogenizations in the presence of detergent and high ionic strength allows the ``solubilization'' of two distinct AcChoEase pools. One is detergent-soluble and mainly composed of slow-sedimenting forms; the other one is detergent-insoluble, high-ionic strength-soluble, and composed mainly of collagen-like, tailed, asymmetric (16S) AcChoEase. Thus, most of the asymmetric AcChoEase is specifically localized in the synaptic extracellular matrix of the mammalian muscle fiber. However, in the A fraction, most of the 16S AcChoEase found is solubilized by detergent alone, suggesting an association with microsomal membranes. It may mean that at least some of the basal lamina-embedded 16S AcChoEase is preassembled intracellularly in the sarcoplasmic reticulum.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.80.21.6698