Amphiphilic properties of molecular forms of acetylcholinesterase in normal and dystrophic muscle

Abstract

Acetylcholinesterase (AChE) molecular forms were studied in normal (NM) and in dystrophic (DM) 129B6F1/J mouse muscle. Successive extractions of the tissue with saline and saline-Triton X-100 buffers yielded two soluble fractions, S1 and S2. Forty percent of the AChE in NM was measured in S1 and 60% in S2, and 65% and 35%, respectively, in extracts from DM. A12, A8, G4, G2, and G1 forms of AChE were found in S1 and S2 from NM and DM. A similar content of asymmetric molecules was noticed between NM and DM. G4 AChE was a minor species in DM, and G1 and G2 AChE were more abundant in DM than in NM. The amphiphilic properties of the several molecules were assessed by Triton X-114 phase-partitioning and hydrophobic chromatography. Thirty and 70% of the enzyme in a mixture of S1 and S2 partitioned in the detergent-rich and in the detergent-poor phases, respectively, whether the extracts were obtained from NM or DM. Asymmetric and G4 AChE predominated in the aqueous phase and G1 and G2 in the detergent phase. Ten and 25% of the enzyme in S1 from NM or DM, respectively, was adsorbed to the phenyl-agarose. Elution of the retained enzyme followed by sedimentation analysis revealed that a certain amount of asymmetric and most of the G1 and G2 forms were associated with the matrix. The content of amphiphilic asymmetric and light globular forms was notably higher in DM than in NM. The results suggest that dystrophic muscle produces a specific pattern of molecular forms of AChE.

Characterization of acetylcholinesterase and butyrylcholinesterase forms in normal and dystrophic Lama2dy mouse heart

“…AChE activity in NH homogenates (9.2 U/g) was in the range reported in different regions of mouse heart (19.8-3.2 U/g, Nyquist-Battie and Trans-Saltzmann, 1989). Moreover, AChE activity was 5-or 30-fold lower than in skeletal muscle (Cabezas-Herrera et al, 1994a) or mouse brain (Moral-Naranjo et al, 1996), the AChE specific activity being much lower in heart than in the other tissues. In agreement with previous results (Nyquist-Battie et al, 1987), BuChE predominated over AChE in heart.…”

“…In contrast to the complete adsorption of the light AChE forms of mouse skeletal muscle (Cabezas-Herrera et al, 1994a) or brain (Moral-Naranjo et al, 1996) to phenyl-agarose, only a fraction of the heart isoforms binds to the resin. However, as in mouse brain, the weak hydrophobicity of the light BuChE species of heart does not suffice for their adsorption to phenyl-agarose, but has the capacity to bind to octyl-Sepharose.…”

“…The AChE forms of 8.6S, 4.2S, or 3.0S migrated at 9.4 Ϯ 0.5S, 5.0 Ϯ 0.2S, and 3.8 Ϯ 0.4S in gradients with Triton X-100 (profiles not shown). The modification of the hydrodynamic properties of proteins with the detergent added to the sucrose gradient is considered as a positive test of amphiphilicity (Cabezas-Herrera et al, 1994a;Moral-Naranjo et al, 1996). According to previous data concerning the sedimentation values of individual AChE forms (Moral-Naranjo et al, 1996), the results indicated that mouse heart is rich in amphiphilic (detergentinteracting) AChE dimers (G 2 A ) and monomers (G 1 A ), migrating at 4.2S and 3.0S in gradients with Brij 96, which together accounted for about half of the enzyme activity (Table II).…”

“…The skeletal muscle of the Lama2 dy mouse shows a specific deficit of G 4 AChE forms (Gisiger and Stephens, 1988;Skau, 1990), an increase of amphiphilic AChE components (Cabezas-Herrera et al, 1994a), and a differential interaction of AChE and BuChE tetramers with RCA (Cabezas-Herrera et al, 1994b), these anomalies probably being related to the abnormal response of acetylcholine receptors in muscle cells of dystrophic mice Lansman, 1994, 1995). Neither the composition nor the glycosylation of ChE forms are altered in serum (Cabezas-Herrera et al, 1994b) or brain (Moral-Naranjo et al, 1996 of Lama2 dy mice.…”

Muscular dystrophy alters the processing of light acetylcholinesterase but not butyrylcholinesterase forms in liver ofLama2dy mice

“…About 40 fractions were collected and assayed for AChE, BuChE, and the sedimentation markers (catalase, 11.4S, and alkaline phosphatase, 6.1S). Sedimentation coefficients for the ChE forms were calculated as reported before (Cabezas-Herrera et al, 1994b). After seven runs with the supernatants S 1 and S 2 from NL, and six from DL, mean values and standard deviation for sedimentation coefficients of ChE species were obtained.…”