RAGE-mediated signaling contributes to intraneuronal transport of amyloid-β and neuronal dysfunction

Abstract

Intracellular amyloid-␤ peptide (A␤) has been implicated in neuronal death associated with Alzheimer's disease. Although A␤ is predominantly secreted into the extracellular space, mechanisms of A␤ transport at the level of the neuronal cell membrane remain to be fully elucidated. We demonstrate that receptor for advanced glycation end products (RAGE) contributes to transport of A␤ from the cell surface to the intracellular space. Mouse cortical neurons exposed to extracellular human A␤ subsequently showed detectable peptide intracellularly in the cytosol and mitochondria by confocal microscope and immunogold electron microscopy. Pretreatment of cultured neurons from wild-type mice with neutralizing antibody to RAGE, and neurons from RAGE knockout mice displayed decreased uptake of A␤ and protection from A␤-mediated mitochondrial dysfunction. A␤ activated p38 MAPK, but not SAPK/JNK, and then stimulated intracellular uptake of A␤-RAGE complex. Similar intraneuronal co-localization of A␤ and RAGE was observed in the hippocampus of transgenic mice overexpressing mutant amyloid precursor protein. These findings indicate that RAGE contributes to mechanisms involved in the translocation of A␤ from the extracellular to the intracellular space, thereby enhancing A␤ cytotoxicity.is a progressive neurodegenerative process characterized by senile plaques, neurofibrillary tangles, and neuronal loss (1, 2). Deposition of amyloid-␤ peptide (A␤), a 39-43-amino acid peptide derived from the transmembrane amyloid precursor protein (APP), is found in extracellular senile plaque cores and is associated with neurodegeneration in later stages of AD. In contrast, recent studies suggest that accumulation of intraneuronal A␤ may be an early event in the pathogenesis of AD (3-16). Addition of A␤ to human neuronal-like cells caused significant mitochondrial damage (17). Furthermore, our recent study revealed that binding of A␤ to A␤-binding alcohol dehydrogenase (ABAD) or cyclophilin D (10, 11) intracellularly triggered events leading to neuronal apoptosis through a mitochondrial pathway (12,13,18,19). However, mechanisms through which A␤ produced at the plasma membrane and released into the extracellular space reaches the intracellular milieu remain to be elucidated.Receptor for advanced glycation end products (RAGE) is a multiligand receptor of the Ig superfamily of cell surface molecules (20)(21)(22). RAGE acts as a counter-receptor for several quite distinct classes of ligands, such as AGEs, S100/calgranulins, HMG1 (high mobility group 1 or amphoterin), and the family of crossed ␤-sheet fibrils/macromolecular assemblies, which activate receptormediated signal transduction pathways. These ligand-receptor interactions are believed to exert pathogenic effects through sustained cellular perturbation in a range of chronic disorders, including the secondary complications of diabetes, inflammation, and neurodegenerative processes (23,24). RAGE, a cell surface binding site for A␤ (25), is expressed at higher levels in an A␤-rich environment (...

Phosphorylation of CHIP at Ser20 by Cdk5 promotes tAIF-mediated neuronal death

“…Rate of cell survival was determined by the MTT reduction assay as previously described with some modifications. 57 Briefly, cortical neurons cultured on a 24-well plate were incubated with 1 mg/ml MTT solution at 37°C for 1 h and lysed in a buffer containing in 20% SDS and 50% aqueous dimethylformamide for 24 h. The optical density of the dissolved formazan grains was measured at 595 and 650 nm as a test and a reference wavelength, respectively, using a VICTOR X3 multilabel plate reader (Perkin Elmer, Waltham, MA, USA).…”

Synaptic Function and Dysfunction in Alzheimer’s Disease

“…It has been reported that RAGE expressed in brain endothelial cells mediates Aβ transport across the blood brain barrier [61]. More recently, Takuma et al [62] reported that RAGE represents at least a co-factor contributing to translocation across cell membrane of Aβ driving its transport and delivery to different subcellular spaces including mitochondria. Mitochondrial dysfunction with resultant neuronal perturbation and cognitive impairment [29,63] is considered a key feature in AD neuropathology and synapto-toxicity.…”

Dysfunction of the lower gastrointestinal tract as a complication of diabetes — a problematic issue in the diabetic care

“…through special receptors (RAGEs) and increase oxidative stress [7]. In research conducted by Takuma et al it was shown that blocking RAGE receptors in mice resulted in reduced frequency of nerve complications [21]. Oxidative stress, which is greatly increased in diabetes, is currently considered an important factor in pathogenesis of gastrointestinal complications [9,22].…”

“…Its etiology comprises complex mechanisms described above which lead to, among others, motility disorders of the small intestine. In case of diarrhea, the microbiological factor and the small intestinal bacterial overgrowth (SIBO) [8,21,27,28,30,32] linked with it should always be taken into account. In research conducted by Bettin Z. et al SIBO was diagnosed in over 1/3 of patients with diabetes complicated by symptoms of autonomic neuropathy in respect to the circulatory system [32].…”