Size and charge isomers of acetylcholinesterase in the cerebral cortex of young and aged rats |
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Authors: | Guillermo M Bisso Rossella Briancesco Hanna Michalek MD PhD |
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Institution: | (1) Laboratory of Pharmacology, Istituto Superiode di Sanità, Viale Regina Elena, 299, 00161 Roma, Italy |
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Abstract: | Previous studies in this laboratory showed an age-related decline of acetylcholinesterase (AChE) activity in the cerebral cortex of rats. In the present study the age-related differences in enzymatic activity were evaluated in terms of individual molecular forms. Extracts containing total, soluble and membrane-bound AChE were analyzed both by ultracentrifugation in sucrose gradient and by non-denaturing gradient polyacrylamide gel electrophoresis. By ultracentrifugation two molecular forms, namely 10S and 4S (corresponding to tetrameric-G4 and monomeric-G1 forms, respectively) were separated in extracts of total and soluble AChE, while only 10S forms were present in extracts of membrane-bound AChE. Electrophoresis of soluble AChE extracts revealed slowly- and fast-migrating bands, grouped in two clusters of at least three bands each; membrane-bound AChE contained only a single slowly-migrating band. Electrophoresis of the single forms isolated by ultracentrifugation showed that slowly- and fast-migrating bands corresponded to G4 and G1 forms, respectively. Therefore, in soluble AChE no one-to-one relationship between charge- and size-isomers was observed; on the contrary, such relationship has been shown for membrane-bound AChE. This implies that soluble G4 forms and membrane-bound-G4 form are electrophoretically different, being heterogeneous the former and homogeneous the latter. The age-related decline of total AChE, accompanied by a decrease of G4/G1 ratio, depended mainly on a decrease of membrane-bound AChE while soluble AChE and its G4/G1 ratio was unchanged. The qualitative pattern of charge isomers was not modified by aging. |
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Keywords: | AChE rat brain aging electrophoretic pattern soluble-and membrane-bound AChE |
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