title: Phosphorylation modulates the alpha-helical structure and polymerization of a peptide from the third tau microtubule-binding repeat.
abstract: Paired helical filaments (PHFs) isolated from patients with Alzheimer's disease (AD) mainly consist of the microtubule-associated protein tau in a hyperphosphorylated form. It has been found that PHFs are the first example of pathological protein aggregation associated with formation of alpha-helices [Biochemistry (2002) 41, 7150-5]. In an effort to investigate the interplay between phosphorylation and the putative role of short regions of alpha-helix in the polymerization of tau, we have focused on the region of tau encompassing residues 317 to 335. This region is able to form protein fibrils in vitro and has two serines that are often found phosphorylated in PHFs. Using trifluoroethanol as an indicator of the alpha-helix, we find that the stability of the alpha-helix conformation is enhanced by phosphorylation. Circular dichroism data show that the phosphorylated peptide in water presents a content in alpha-helix similar to the unphosphorylated peptide at 40% of trifluoroethanol. Phosphorylation also stimulates the effect of juglone in promoting the in vitro polymerization. Furthermore, Fourier transformed infrared spectroscopy of samples of phosphorylated peptide polymerized with juglone renders a spectrum with maxima at approximately 1665 and approximately 1675 cm(-1), which are suggestive of a mixture of turns and alpha-helix conformations. Our results provide a direct mechanistic connection between phosphorylation and polymerization in tau. The connection between phosphorylation and polymerization appears to involve formation of alpha-helix structure.
authors.affiliation: Centro de Biología Molecular Severo Ochoa CSIC/UAM, Fac. Ciencias, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Mendieta
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Fuertes
authors.forename: Rani
authors.initials: R
authors.lastname: Kunjishapatham
authors.forename: Ismael
authors.initials: I
authors.lastname: Santa-María
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Moreno
authors.forename: Carlos
authors.initials: C
authors.lastname: Alonso
authors.forename: Federico
authors.initials: F
authors.lastname: Gago
authors.forename: Victor
authors.initials: V
authors.lastname: Muñoz
authors.forename: Jesús
authors.initials: J
authors.lastname: Avila
authors.forename: Félix
authors.initials: F
authors.lastname: Hernández
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002942:Circular Dichroism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D008870:Microtubules / Q000378:metabolism*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011108:Polymers / Q000737:chemistry; D017433:Protein Structure, Secondary; D020449:Repetitive Sequences, Amino Acid; D017550:Spectroscopy, Fourier Transform Infrared; D016875:tau Proteins / Q000737:chemistry*
chemical_list: D011108:Polymers; D016875:tau Proteins; D000071679:Glycogen Synthase Kinase 3 beta; D017868:Cyclic AMP-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3