Substitution of a glycogen synthase kinase-3beta phosphorylation site in presenilin 1 separates presenilin function from beta-catenin signaling.
The majority of cases with early onset familial Alzheimer's disease have been attributed to mutations in the presenilin 1 (PS1) gene. PS1 protein is a component of a high molecular weight membrane-bound complex that also contains beta-catenin. The physiological relevance of the association between PS1 and beta-catenin remains controversial. In this study, we report the identification and functional characterization of a highly conserved glycogen synthase kinase-3beta consensus phosphorylation site within the hydrophilic loop domain of PS1. Site-directed mutagenesis, together with in vitro and in vivo phosphorylation assays, indicates that PS1 residues Ser(353) and Ser(357) are glycogen synthase kinase-3beta targets. Substitution of one or both of these residues greatly reduces the ability of PS1 to associate with beta-catenin. By disrupting this interaction, we demonstrate that the association between PS1 and beta-catenin has no effect on Abeta peptide production, beta-catenin stability, or cellular susceptibility to apoptosis. Significantly, in the absence of PS1/beta-catenin association, we found no alteration in beta-catenin signaling using induction of this pathway by exogenous expression of Wnt-1 or beta-catenin and a Tcf/Lef transcriptional assay. These results argue against a pathologically relevant role for the association between PS1 and beta-catenin in familial Alzheimer's disease.
Pubmed ID: 11104755 RIS Download
Alzheimer Disease | Amino Acid Motifs | Amino Acid Sequence | Amyloid beta-Peptides | Apoptosis | Binding Sites | Blotting, Western | Calcium-Calmodulin-Dependent Protein Kinases | Cell Death | Cell Line | Cell Nucleus | Cytoskeletal Proteins | Cytosol | DNA, Complementary | Genetic Vectors | Glycogen Synthase Kinase 3 | Glycogen Synthase Kinases | Humans | Luciferases | Membrane Proteins | Microscopy, Fluorescence | Models, Molecular | Molecular Sequence Data | Mutagenesis, Site-Directed | Mutation | Peptide Fragments | Phosphorylation | Precipitin Tests | Presenilin-1 | Protein Binding | Protein Structure, Tertiary | Sequence Homology, Amino Acid | Serine | Signal Transduction | Trans-Activators | Transfection | beta Catenin