Browsing by Subject "GPI-anchored proteins"

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    Muscular dystrophy by merosin deficiency decreases acetylcholinesterase activity in thymus of Lama2dy mice
    (WILEY, 2005-08-31) Vidal Moreno, Cecilio Jesús; Nieto Cerón, Susana; Campoy Menéndez, Francisco Javier; Muñoz Delgado, Encarnación; Sánchez del Campo Ferrer, Luis; Bioquímica y Biología Molecular A
    Half of congenital muscular dystrophy cases arise from laminin alpha 2 (merosin) deficiency, and merosin-deficient mice (Lama2dy) exhibit a dystrophic phenotype. The abnormal development of thymus in Lama2dy mice, the occurrence of acetylcholinesterase (AChE) in the gland and the impaired distribution of AChE molecules in skeletal muscle of the mouse mutant prompted us to compare the levels of AChE mRNAs and enzyme species in thymus of control and Lama2dy mice. AChE activity in normal thymus (mean +/- SD 1.42 +/- 0.28 mu mol acetylthiocholine/h/mg protein, U/mg) was decreased by similar to 50% in dystrophic thymus (0.77 +/- 0.23 U/mg) (p = 0.007), whereas butyrylcholinesterase activity was little affected. RT-PCR assays revealed variable levels of R, H and T AChE mRNAs in thymus, bone marrow and spinal cord. Control thymus contained amphiphilic AChE dimers (G(2)(A), 64%) and monomers (G(1)(A), 19%), as well as hydrophilic tetramers (G(4)(H), 9%) and monomers (G(1)(H), 8%). The dimers consisted of glycosylphosphatidylinositol-anchored H subunits. Western blot assays with anti-AChE antibodies suggested the occurrence of inactive AChE in mouse thymus. Despite the decrease in AChE activity in Lama2dy thymus, no differences between thymuses from control and dystrophic mice were observed in the distribution of AChE forms, phosphatidylinositol-specific phospholipase C sensitivity, binding to lectins and size of AChE subunits.
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    Targeting of acetylcholinesterase to lipid rafts of muscle
    (Elsevier, 2008-09-25) Moral Naranjo, M. T.; Montenegro Arce, María Fernanda; Muñoz Delgado, Encarnación; Campoy, M. J.; Vidal, C. J.; Bioquímica y Biología Molecular A
    Despite the great progress made in setting the basis for the molecular diversity of acetylcholinesterase (AChE), an explanation for the existence oftwo types of amphiphilic subunits, with and without glicosylphosphatidylinositol (GPI) (Types I and II), has not been provided yet. In searching whether, as for the deficiency of dystrophin, that of merosin (laminin- 2 chain) alters the number of caveolae in muscle, a high increase in caveolin-3 (Cav3) was observed in the Triton X-100-resistant membranes (TRM) isolated from muscle of merosin-deficient dystrophic mice (Lama2dy). The rise in Cav3 was accompanied by that of non-caveolar lipid rafts, as showed by the greater ecto-5 -nucleotidase (eNT) activity, a marker of non-caveolar rafts, in TRM of dystrophic muscle. The observation of AChE activity in TRM, the increased levels of rafts and raft-bound AChE activity in merosin-deficient muscle and the presence of phospholipase C-sensitive AChE dimers in TRM supported targeting of glypiated AChE to rafts. This issue and the involvement of TRM in conveying nicotinic receptors to the neuromuscular junction and particular muscarinic receptors to cardiac sarcolemma strongly support a role for lipid rafts in targeting ACh receptors and glypiated AChE. Their nearby location in the surface membrane may provide cells with a fine tuning for regulating cholinergic responses.