In silico and in vitro studies to elucidate the role of Cu2+ and galanthamine as the limiting step in the amyloid beta (1–42) fibrillation process

Authors

  • Maricarmen Hernández-Rodríguez,

    1. Laboratorio de Modelado Molecular y Bioinformatica, Escuela Superior de Medicina, Instituto Politécnico Nacional, México
    2. Laboratorio de Biofísica y Biocatálisis, Escuela Superior de Medicina, Instituto Politécnico Nacional, México
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  • José Correa-Basurto,

    Corresponding author
    • Laboratorio de Modelado Molecular y Bioinformatica, Escuela Superior de Medicina, Instituto Politécnico Nacional, México
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  • Claudia G. Benitez-Cardoza,

    1. Laboratorio de Investigación Bioquímica, Laboratorio de Investigación Bioquímica, Sección de Estudios de Posgrado e Investigación. ENMyH-Instituto Politécnico Nacional, México
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  • Aldo Arturo Resendiz-Albor,

    1. Laboratorio de Investigación en Inmunología., Escuela Superior de Medicina, Instituto Politécnico Nacional, México
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  • Martha C. Rosales-Hernández

    Corresponding author
    • Laboratorio de Biofísica y Biocatálisis, Escuela Superior de Medicina, Instituto Politécnico Nacional, México
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Correspondence to: Jose Correa, Laboratorio de Modelado Molecular y Bioinformática, Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón, 11340, México City, México. E-mail: corrjose@gmail.com or Martha C. Rosales-Hernández. E-mail: marcrh2002@yahoo.com.mx

Abstract

The formation of fibrils and oligomers of amyloid beta (Aβ) with 42 amino acid residues (Aβ1–42) is the most important pathophysiological event associated with Alzheimer's disease (AD). The formation of Aβ fibrils and oligomers requires a conformational change from an α-helix to a β-sheet conformation, which is encouraged by the formation of a salt bridge between Asp 23 or Glu 22 and Lys 28. Recently, Cu2+ and various drugs used for AD treatment, such as galanthamine (Reminyl®), have been reported to inhibit the formation of Aβ fibrils. However, the mechanism of this inhibition remains unclear. Therefore, the aim of this work was to explore how Cu2+ and galanthamine prevent the formation of Aβ1–42 fibrils using molecular dynamics (MD) simulations (20 ns) and in vitro studies using fluorescence and circular dichroism (CD) spectroscopies. The MD simulations revealed that Aβ1–42 acquires a characteristic U-shape before the α-helix to β-sheet conformational change. The formation of a salt bridge between Asp 23 and Lys 28 was also observed beginning at 5 ns. However, the MD simulations of Aβ1−42 in the presence of Cu2+ or galanthamine demonstrated that both ligands prevent the formation of the salt bridge by either binding to Glu 22 and Asp 23 (Cu2+) or to Lys 28 (galanthamine), which prevents Aβ1−42 from adopting the U-characteristic conformation that allows the amino acids to transition to a β-sheet conformation. The docking results revealed that the conformation obtained by the MD simulation of a monomer from the 1Z0Q structure can form similar interactions to those obtained from the 2BGE structure in the oligomers. The in vitro studies demonstrated that Aβ remains in an unfolded conformation when Cu2+ and galanthamine are used. Then, ligands that bind Asp 23 or Glu 22 and Lys 28 could therefore be used to prevent β turn formation and, consequently, the formation of Aβ fibrils.

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