G. Poiana1, G. Scarsella1, S. Biagioni2, M.I. Senni3, G. Cossu3
1Dipartimento di Biologia Cellulare e dello Sviluppo, Università “La Sapienza”, RomaItaly
2Istituto di Istologia ed Analisi di Laboratorio, Università di Urbino, UrbinoItaly
3Istituto di Istologia ed Embriologia Generale, Università “La Sapienza”, Roma, Italy
Tóm tắt
AbstractMurine muscular dystrophy is characterized by a reduction of the 10S molecular form of acetylcholinesterase (AChE); this reduction occurs in both strains of dystrophic mice and at the time of the phenotypic appearance of the disease.In the present study we have analyzed the biochemical features, the cellular distribution and the developmental appearance of the AChE alteration. Sequential extractions with low salt, detergent and high salt revealed that this alteration affects only membrane‐bound forms (those requiring Triton X‐100 for solubilization), while both the low salt soluble and the high salt soluble forms appeared almost identical in normal and dystrophic muscles. Specific activity, sensitivity to different ions, pH dependence and Km were found to be identical in the enzymes from normal and dystrophic muscles, suggesting that the catalytic site of the 10S form is probably not altered.Further analysis, by non‐denaturing gel electrophoresis, of the detergent soluble forms separated by sedimentation, revealed a single band for the 4S, a doublet for the 6S and three bands for the 10S peaks, indicating the existence of charge heterogeneity in AChE molecular forms. The corresponding molecular forms from dystrophic muscles behaved identically upon electrophoresis: the residual activity in the detergent soluble 10S form could still be separated into three bands, comigrating with their normal counterparts. Neuraminidase treatment resulted in a reduction of migration of both the 6S and 10S derived bands, but not of the 4S species, showing that sialic acid is added only to polymeric forms. Interestingly, the reduction of the 10S form appears to be linked to a developmental stage not reached in cell cultures, as cultured myotubes from muscles of dystrophic mice contained normal amounts of membrane‐bound AChE forms. The molecular mechanism underlying the reduction of the tetrameric membrane bound AChE form in dystrophic muscle and the possible functional consequences are discussed.
