Serum is required for release of Alzheimer's amyloid precursor protein in neuroblastoma cells

Monocyte-mediated regulation of genes by the amyloid and prion peptides in SH-SY5Y neuroblastoma cells

Alzheimer's disease as well as prion-related encephalopathies are neurodegenerative disorders of the central nervous system, which cause mental deterioration and progressive dementia. Both pathologies appear to be primarily associated with the pathological accumulation and deposit of β-amyloid or prion peptides in the brain, and it has been even suggested that neurotoxicity induced by these peptides would be associated to essentially similar pathogenic mechanisms, in particular to those that follow the activation of microglial cells. To probe whether the neurotoxic effects induced by the β-amyloid and prion peptides are actually mediated by similar glial-associated mechanisms, we have examined the differential expression of genes in SH-SY5Y neuroblastoma cells incubated with conditioned media from β-amyloid or prion-stimulated THP-1 monocytic cells. According to microarray analysis, not many coincidences are observed and only four genes (Hint3, Psph, Daam1 and c-Jun) appear to be commonly upregulated by both peptides. Furthermore, c-Jun appears to be involved in the cell death mediated by both peptides.

Identification of genes differentially expressed in SH-SY5Y neuroblastoma cells exposed to the prion peptide 106-126

Prion diseases are a group of neurodegenerative disorders characterized by astrocytosis and progressive neuronal degeneration. As a causative agent, prions have been intensely investigated in different experimental models. However, the mechanisms and pathways involved in the prion-induced neurological dysfunction are poorly understood. In this work we have investigated the influence of prion infection on the gene expression profile in a human neuroblastoma cell line. Using a DNA microarray and quantitative reverse transcriptase-polymerase chain reaction methods, we have analysed in SH-SY5Y cells the effects of a synthetic peptide corresponding to the 106-126 neurotoxic region of the cellular human prion protein. Our results show that addition of this peptide to the neuronal culture specifically changes the expression of a relative high number of genes, and causes a progressive neuronal death even in the absence of microglia.

Gene expression profile in β-amyloid-treated SH-SY5Y neuroblastoma cells

The beta-amyloid peptide, the major component of the senile plaques in Alzheimer's disease (AD), has been probed to be toxic to neurons both in vivo and in vitro. Several mechanisms have been proposed to be involved in the amyloid-induced neurotoxicity; among others it has been suggested that the beta-amyloid peptide exerts its toxic effect mainly by activating the surrounding microglia population, which in turn induces the synthesis and release of preapoptotic and pro-inflammatory factors. In addition, a direct effect of beta-amyloid on neurons has been also described. However, the precise mechanisms involved in the amyloid-induced neurotoxicity have been not yet definitely clarified. To characterize the effects directly induced on neurons, we have analyzed the gene expression profile induced by the 25-35 beta-amyloid fragment in human SH-SY5Y neuroblastoma cells, by using the Affymetrix GeneChip Human Genome U133 Plus 2.0 Array. Our results confirm that beta-amyloid may directly induce neuronal cell death; activating signals that in vivo have been described as causative of Alzheimer's disease.

Direct involvement of G protein alpha(q/11) subunit in regulation of muscarinic receptor-mediated sAPPalpha release

The G(q/11) protein-coupled receptors, such as muscarinic (M1 & M3) receptors, have been shown to regulate the release of a soluble amyloid precursor protein (sAPPalpha) produced from alpha-secretase processing. However, there is no direct evidence for the precise characteristics of G proteins, and the signaling mechanism for the regulation of G(q/11) protein-coupled receptor-mediated sAPPalpha release is not clearly understood. This study examined whether the muscarinic receptor-mediated release of sAPPalpha is directly regulated by Galpha(q/11) proteins. The HEK293 cells were transiently cotransfected with muscarinic M3 receptors and a dominant-negative minigene construct of the G protein alpha subunit. The sAPPalpha release in the media was measured using an antibody specific for sAPP. The sAPPalpha release enhancement induced by muscarinic receptor stimulation was decreased by a G(q/11) minigene construct, whereas it was not blocked by a control minigene construct (the Galpha carboxy peptide in random order, Galpha(q)R) or Galpha(i) constructs. This indicated a direct role of the Galpha(q/11) protein in the regulation of muscarinic M3 receptor-mediated sAPPalpha release. We also investigated whether the transactivation of the epidermal growth factor receptor (EGFR) by a muscarinic agonist could regulate the sAPPalpha release in SH-SY5Y cells. Pretreatment of a specific EGFR kinase inhibitor, tyrophostin AG1478 (250 nM), blocked the EGF-stimulated sAPPalpha release, but did not block the oxoM-stimulated sAPPalpha release. This demonstrated that the transactivation of the EGFR by muscarinic receptor activation was not involved in the muscarinic receptor-mediated sAPPalpha release.

Mutant presenilin (A260V) affects Rab8 in PC12D cell

Most familial early-onset Alzheimer's disease (FAD) is caused by mutations in the presenilin-1 (PS1) gene. Abeta is derived from amyloid precursor protein (APP) and an increased concentration of Abeta 42 is widely believed to be a pathological hallmark of abnormal PS function. Therefore, the interaction between PS1 and APP is a central theme in attempts to clarify the molecular mechanism of AD. To examine the effect of PS1 mutations on APP metabolism, we made PC12D cell lines that express human PS1 or mutant PS1 (A260V). In PC12D cells expressing the PS1A260V mutant, we found that Rab8, a GTPase involved in transport from the trans-Golgi network (TGN) to the plasma membrane (PM), was significantly reduced in PC12D cells expressing the A260V mutant and that APP C-terminal fragment (CTF), the direct precursor of Abeta, accumulated in the heavy membrane fraction including membrane vesicles involved in TGN-to-PM transport. Furthermore, the total intracellular Abeta production was reduced in these cells. Combined together, we have observed that PS1 mutation disturbs membrane vesicle transport, resulting in prolonged residence of APP CTF during TGN-to-PM transport pathway. Therefore, it is highly likely that reduction of Abeta is closely related to the retention of APP CTF during TGN-to-PM transport.