ABSTRACT
Two genes on chromosome 21, namely dual specificity tyrosine phosphorylation-regulated kinase 1A (Dyrk1A) and regulator of calcineurin 1 (RCAN1), have been implicated in some of the phenotypic characteristics of Down syndrome, including the early onset of Alzheimer disease. Although a link between Dyrk1A and RCAN1 and the nuclear factor of activated T cells (NFAT) pathway has been reported, it remains unclear whether Dyrk1A directly interacts with RCAN1. In the present study, Dyrk1A is shown to directly interact with and phosphorylate RCAN1 at Ser(112) and Thr(192) residues. Dyrk1A-mediated phosphorylation of RCAN1 at Ser(112) primes the protein for the GSK3ß-mediated phosphorylation of Ser(108). Phosphorylation of RCAN1 at Thr(192) by Dyrk1A enhances the ability of RCAN1 to inhibit the phosphatase activity of calcineurin (Caln), leading to reduced NFAT transcriptional activity and enhanced Tau phosphorylation. These effects are mediated by the enhanced binding of RCAN1 to Caln and its extended half-life caused by Dyrk1A-mediated phosphorylation. Furthermore, an increased expression of phospho-Thr(192)-RCAN1 was observed in the brains of transgenic mice overexpressing the Dyrk1A protein. These results suggest a direct link between Dyrk1A and RCAN1 in the Caln-NFAT signaling and Tau hyperphosphorylation pathways, supporting the notion that the synergistic interaction between the chromosome 21 genes RCAN1 and Dyrk1A is associated with a variety of pathological features associated with DS.
Subject(s)
Intracellular Signaling Peptides and Proteins/metabolism , Muscle Proteins/metabolism , Protein Serine-Threonine Kinases/metabolism , Protein-Tyrosine Kinases/metabolism , Animals , Calcineurin/genetics , Calcineurin/metabolism , Calcium-Binding Proteins , Chromosomes, Human, Pair 21/genetics , Chromosomes, Human, Pair 21/metabolism , DNA-Binding Proteins , Down Syndrome/genetics , Down Syndrome/metabolism , Glycogen Synthase Kinase 3/genetics , Glycogen Synthase Kinase 3/metabolism , Glycogen Synthase Kinase 3 beta , HEK293 Cells , Humans , Intracellular Signaling Peptides and Proteins/genetics , Mice , Mice, Transgenic , Muscle Proteins/genetics , NFATC Transcription Factors/genetics , NFATC Transcription Factors/metabolism , Phosphorylation/genetics , Protein Binding/genetics , Protein Serine-Threonine Kinases/genetics , Protein-Tyrosine Kinases/genetics , Signal Transduction/genetics , Transcription, Genetic/genetics , tau Proteins/genetics , tau Proteins/metabolism , Dyrk KinasesABSTRACT
The dual-specificity tyrosine(Y)-phosphorylation-regulated kinase 1A (Dyrk1A) gene is located on human chromosome 21 and encodes a proline-directed protein kinase that might be responsible for mental retardation and early onset of Alzheimer's disease (AD) in Down syndrome (DS) patients. Presenilin 1 (PS1) is a key component of the γ-secretase complex in the generation of ß-amyloid (Aß), an important trigger protein in the pathogenesis of AD. Increased Dyrk1A expression has been reported in human AD and DS brains. We previously showed that Dyrk1A increased Aß production in mammalian cells and transgenic mice that over-express Dyrk1A. In this study, we describe a potential mechanism by which Aß is increased in Dyrk1A-over-expressing DS and AD brains. First, we show that PS1 is phosphorylated by the Dyrk1A at Thr(354) and that this phosphorylation increases γ-secretase activity. Then, using transgenic mice that over-express human Dyrk1A, we demonstrate that phospho-Thr354-PS1 (pT354-PS1) expression is enhanced when Dyrk1A level is increased. We also show that pT354-PS1 is more stable than the unphosphorylated form of PS1. These results reveal a potential regulatory link between Dyrk1A and PS1 in the Aß pathway of DS and AD brains, suggesting that up-regulated Dyrk1A may accelerate AD pathogenesis through PS1 phosphorylation.
