A Preliminary Study: PS1 Increases U1 snRNA Expression Associated with AD

Understanding the mechanisms of disease modifying effects of aerobic exercise in people with Alzheimer's disease

Alzheimer's disease (AD) is a very disabling disease. Pathologically, it is characterized by the presence of amyloid plaques and neurofibrillary tangles in the brain that results in neurodegeneration. Its clinical manifestations include progressive memory impairment, language decline and difficulty in carrying out activities of daily living (ADL). The disease is managed using interventions such as pharmacological interventions and aerobic exercise. Use of aerobic exercise has shown some promises in reducing the risk of developing AD, and improving cognitive function and the ability to carry out both basic and instrumental ADL. Although, the mechanisms through which aerobic exercise improves AD are poorly understood, improvement in vascular function, brain glucose metabolism and cardiorespiratory fitness, increase in antioxidant capacity and haemoglobin level, amelioration of immune-related and inflammatory responses, modulation of concentration of circulating Neurotrophins and peptides and decrease in concentration of tau protein and cortisol level among others seem to be the possible mechanisms. Therefore, understanding these mechanisms is important to help characterize the dose and the nature of the aerobic exercise to be given. In addition, they may also help in finding ways to optimize other interventions such as the pharmacological interventions. However, more quality studies are needed to verify the mechanisms.

Neuroprotective Effects of Vapreotide on Tau Transfection-Induced Neurodegeneration

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by loss of neurons and synapses. The aim of this study was to investigate the effect of somatostatin analogue Vapreotide in an in vitro Alzheimer's model and its effects based on the relationship between somatostatinergic transmission and neurodegenerative functions. In this study, tau transfection was performed using the MAPT gene cloned into the pcDNA3.1 vector and transfection reagent into the SH-SY5Y cell line. In viability experiments using 10 µM Memantine as a positive control, it was observed that Vapreotide at 50 µM (p < 0.0001) and 100 µM (p < 0.05) had a protective effect on cell viability, 100 µM CYN154806 was found to decrease (p < 0.05) cell viability. It was determined that Vapreotide, decreased the expression levels (50 µM-p < 0.001; 100 µM-p < 0.001; 200 µM-p < 0.0001) and phosphorylation of Tau and p-Tau proteins by western blots. With the qRT-PCR method, it was found that Vapreotide, decreased the BAX/BCL2 (50 µM-p < 0.001; 100 µM-p < 0.01; 200 µM-p < 0.001) expression level and decreased the expression level (50 µM-p < 0.01; 100 µM-p < 0.01; 200 µM-p < 0.001) of the APOE4 gene, which constitutes a genetic risk for AD. This study demonstrates a potential therapeutic role for a somatostatin analogue Vapreotide in Alzheimer's disease.

Autophagy regulation by RNA alternative splicing and implications in human diseases

Autophagy and RNA alternative splicing are two evolutionarily conserved processes involved in overlapping physiological and pathological processes. However, the extent of functional connection is not well defined. Here, we consider the role for alternative splicing and generation of autophagy-related gene isoforms in the regulation of autophagy in recent work. The impact of changes to the RNA alternative splicing machinery and production of alternative spliced isoforms on autophagy are reviewed with particular focus on disease relevance. The use of drugs targeting both alternative splicing and autophagy as well as the selective regulation of single autophagy-related protein isoforms, are considered as therapeutic strategies.

Nano-CuO causes cell damage through activation of dose-dependent autophagy and mitochondrial lncCyt b-AS/ND5-AS/ND6-AS in SH-SY5Y cells

Metal copper oxide nanoparticles (nano-CuO) are under mass production and have been widely utilized in many fields including catalysis, gas sensors, semiconductor materials, etc. The broad applications of nano-CuO have increased the possibility of risk to incidental exposure to the environment, and therefore, an in-depth investigation of their effects on live cells is required. This study investigated the impact of the nano-CuO on SH-SY5Y cells, and findings showed that the ratio of LC3-II/LC3-I was significantly increased in SH-SY5Y cells when the cells were treated with nano-CuO. However, if the autophagy inhibitor Bafilomycin A1 (Baf A1) was co-treated, the ratio of LC3-II/LC3-I was further improved. These outcomes might indicate that autophagy flux was permanently elevated by adding nano-CuO. Further results found highly activated levels of long noncoding RNAs (lncRNAs) under nano-CuO treatment. The data illustrate a mechanism that nano-CuO can promote autophagy and activate lncCyt b-AS/ND5-AS/ND6-AS in SH-SY5Y cells and have critical implications for nanoparticle biomedical applications.

Presenilin 1 mutation likely contributes to U1 small nuclear RNA dysregulation and Alzheimer's disease-like symptoms

Previous studies showed that U1 small nuclear RNA (snRNA) was selectively enriched in the brain of individuals with familial Alzheimer's disease (AD), resulting in widespread changes in RNA splicing. Our study further reported that presenilin-1 (PSEN1) induced an increase in U1 snRNA expression, accompanied by changed amyloid precursor protein expression, β-amyloid level, and cell death in SH-SY5Y cells. However, the effect of U1 snRNA overexpression on learning and memory is still unclear. In the present study, we found that neuronal U1 snRNA overexpression could generate U1 snRNA aggregates in the nuclear, accompanied by the widespread alteration of RNA splicing, resulting in the impairments of synaptic plasticity and spatial memory. In addition, more U1 snRNAs is bound to the intron binding sites accompanied by an increased intracellular U1 snRNA level. This suggests that U1 snRNA overexpression regulates RNA splicing and gene expression in neurons by manipulating the recruitment of the U1 snRNA to the nascent transcripts. Using in situ hybridization staining of human central nervous system-type neurons, we identified nuclear aggregates of U1 snRNA in neurons by upregulating the U1 snRNA level. Quantitative polymerase chain reaction analysis showed U1 snRNA accumulation in the insoluble fraction of neurons with PSEN1 mutation neurons rather than other types of U snRNAs. These results show an independent function of U1 snRNA in regulating RNA splicing, suggesting that aberrant RNA processing may mediate neurodegeneration induced by PSEN1 mutation.

U1 snRNA over-expression affects neural oscillations and short-term memory deficits in mice

Small nuclear RNAs (snRNAs) and other RNA spliceosomal components are involved in neurological and psychiatric disorders. U1 snRNA has recently been demonstrated to be altered in pathology in some neurodegenerative diseases, but whether it has a causative role is not clear. Here we have studied this by overexpressing U1 snRNA in mice and measured their hippocampal oscillatory patterns and brain functions. Novel object recognition test showed that the recognition index was significantly decreased in the U1 snRNA over-expression mice compared to that in the C57BL mice. U1 snRNA over-expression regulated not only the pattern of neural oscillations but also the expression of neuron excitatory and inhibitory proteins. Here we show that U1 snRNA over-expression contains the shrinkage distribution of theta-power, theta-phase lock synchronization, and theta and low-gamma cross-frequency coupling in the hippocampus. The alternations of neuron receptors by the U1 snRNA overexpression also modulated the decreasing of recognition index, the energy distribution of theta power spectrum with the reductions of theta phase synchronization and phase-amplitude coupling between theta and low-gamma. Linking these all together, our results suggest that U1 snRNA overexpression particularly causes a deficit in short-term memory. These findings make a bedrock of our research that U1 snRNA bridges the gap about the mechanism behind short-term memory based on the molecular and mesoscopic level.

Linking Endoplasmic Reticular Stress and Alternative Splicing

RNA splicing patterns in antibody-secreting cells are shaped by endoplasmic reticulum stress, ELL2 (eleven-nineteen lysine-rich leukemia gene 2) induction, and changes in the levels of snRNAs. Endoplasmic reticulum stress induces the unfolded protein response comprising a highly conserved set of genes crucial for cell survival; among these is Ire1, whose auto-phosphorylation drives it to acquire a regulated mRNA decay activity. The mRNA-modifying function of phosphorylated Ire1 non-canonically splices Xbp1 mRNA and yet degrades other cellular mRNAs with related motifs. Naïve splenic B cells will activate Ire1 phosphorylation early on after lipopolysaccharide (LPS) stimulation, within 18 h; large-scale changes in mRNA content and splicing patterns result. Inhibition of the mRNA-degradation function of Ire1 is correlated with further differences in the splicing patterns and a reduction in the mRNA factors for snRNA transcription. Some of the >4000 splicing changes seen at 18 h after LPS stimulation persist into the late stages of antibody secretion, up to 72 h. Meanwhile some early splicing changes are supplanted by new splicing changes introduced by the up-regulation of ELL2, a transcription elongation factor. ELL2 is necessary for immunoglobulin secretion and does this by changing mRNA processing patterns of immunoglobulin heavy chain and >5000 other genes.

RNA Splicing in the Transition from B Cells to Antibody-Secreting Cells: The Influences of ELL2, Small Nuclear RNA, and Endoplasmic Reticulum Stress

In the transition from B cells to Ab-secreting cells (ASCs) many genes are induced, such as ELL2, Irf4, Prdm1, Xbp1, whereas other mRNAs do not change in abundance. Nonetheless, using splicing array technology and mouse splenic B cells plus or minus LPS, we found that induced and "uninduced" genes can show large differences in splicing patterns between the cell stages, which could influence ASC development. We found that ∼55% of these splicing changes depend on ELL2, a transcription elongation factor that influences expression levels and splicing patterns of ASC signature genes, genes in the cell-cycle and N-glycan biosynthesis and processing pathways, and the secretory versus membrane forms of the IgH mRNA. Some of these changes occur when ELL2 binds directly to the genes encoding those mRNAs, whereas some of the changes are indirect. To attempt to account for the changes that occur in RNA splicing before or without ELL2 induction, we examined the amount of the small nuclear RNA molecules and found that they were significantly decreased within 18 h of LPS stimulation and stayed low until 72 h. Correlating with this, at 18 h after LPS, endoplasmic reticulum stress and Ire1 phosphorylation are induced. Inhibiting the regulated Ire1-dependent mRNA decay with 4u8C correlates with the reduction in small nuclear RNA and changes in the normal splicing patterns at 18 h. Thus, we conclude that the RNA splicing patterns in ASCs are shaped early by endoplasmic reticulum stress and Ire1 phosphorylation and later by ELL2 induction.

U1 snRNP Alteration and Neuronal Cell Cycle Reentry in Alzheimer Disease

The aberrancy of U1 small nuclear ribonucleoprotein (snRNP) complex and RNA splicing has been demonstrated in Alzheimer's disease (AD). Importantly, the U1 proteopathy is AD-specific, widespread and early-occurring, thus providing a very unique clue to the AD pathogenesis. The prominent feature of U1 histopathology is its nuclear depletion and redistribution in the neuronal cytoplasm. According to the preliminary data, the initial U1 cytoplasmic distribution pattern is similar to the subcellular translocation of the spliceosome in cells undergoing mitosis. This implies that the U1 mislocalization might reflect the neuronal cell cycle-reentry (CCR) which has been extensively evidenced in AD brains. The CCR phenomenon explains the major molecular and cellular events in AD brains, such as Tau and amyloid precursor protein (APP) phosphorylation, and the possible neuronal death through mitotic catastrophe (MC). Furthermore, the CCR might be mechanistically linked to inflammation, a critical factor in the AD etiology according to the genetic evidence. Therefore, the discovery of U1 aberrancy might strengthen the involvement of CCR in the AD neuronal degeneration.

U1 snRNP Alteration and Neuronal Cell Cycle Reentry in Alzheimer Disease

The aberrancy of U1 small nuclear ribonucleoprotein (snRNP) complex and RNA splicing has been demonstrated in Alzheimer’s disease (AD). Importantly, the U1 proteopathy is AD-specific, widespread and early-occurring, thus providing a very unique clue to the AD pathogenesis. The prominent feature of U1 histopathology is its nuclear depletion and redistribution in the neuronal cytoplasm. According to the preliminary data, the initial U1 cytoplasmic distribution pattern is similar to the subcellular translocation of the spliceosome in cells undergoing mitosis. This implies that the U1 mislocalization might reflect the neuronal cell cycle-reentry (CCR) which has been extensively evidenced in AD brains. The CCR phenomenon explains the major molecular and cellular events in AD brains, such as Tau and amyloid precursor protein (APP) phosphorylation, and the possible neuronal death through mitotic catastrophe (MC). Furthermore, the CCR might be mechanistically linked to inflammation, a critical factor in the AD etiology according to the genetic evidence. Therefore, the discovery of U1 aberrancy might strengthen the involvement of CCR in the AD neuronal degeneration.

U1 small nuclear RNA overexpression implicates autophagic-lysosomal system associated with AD

Recently, we reported that presenilin 1 considerably increased the expression level of U1 small nuclear RNA (snRNA) accompanied with the adverse change of amyloid precursor protein (APP) expression, β-amyloid (Aβ) production and cell apoptosis. In the present study, it was found that U1 snRNA overexpression significantly elevated the expression level of autophagy. Moreover, rapamycin further enhanced the Aβ production and cell apoptosis, whereas these processes were effectively inhibited by 3-MA. Acridine orange staining images showed that U1 snRNA overexpression not only activated autophagy pathway, but also led to the autophagic-lysosomal system dysfunction in cells. Immunofluorescence assay showed autophagic vacuoles localization with APP, which was the precursor protein of main component of toxic protein in AD. Meanwhile, the superoxide dismutase activity was remarkably decreased and MDA level was significantly increased by U1 snRNA overexpression in cells, suggesting that there was a possible pathway to elucidate how the U1 snRNA overexpression induced cell damage. We further found that U1 snRNA overexpression altered lysosomal biogenesis and autophagic-lysosomal fusion. In combination with our previous results, it suggests that the malfunction of autophagy pathway provides important insight into molecular mechanisms of augment the aggregation of Aβ and induction of cell apoptosis contributed to AD.

Gene expression profiling reveals U1 snRNA regulates cancer gene expression

U1 small nuclear RNA (U1 snRNA), as one of the most abundant ncRNAs in human cells, plays an important role in splicing of pre-mRNAs. Compared to previous studies which have focused on the primary function of U1 snRNA and the neurodegenerative diseases caused by abnormalities of U1 snRNA, this study is to investigate how U1 snRNA over-expression affects the expression of mammal genes on a genome-wide scale. By comparing the gene expression profiles of U1 snRNA over-expressed cells with those of their controls using microarray experiments, 916 genes or loci were identified significantly Differentially Expressed (DE). These 595 up-regulated DE genes and 321 down-regulated DE genes were analyzed using annotations from GO categories and pathways from the KEGG database. As a result, three of 12 enriched pathways were well-known cancer pathways, while the other nine pathways were associated to cancers in previous studies. The further analysis of 73 genes involved in 12 pathways suggested that U1 snRNA could regulate cancer gene expression. The microarray data under the GEO Series accession number GSE84304 is available in the NCBI GEO database.

Overexpression of U1 snRNA induces decrease of U1 spliceosome function associated with Alzheimer's disease

We recently reported that presenilin-1 (PS1) induced an increase of U1 snRNA expression accompanied with the change of amyloid precursor protein expression, β-amyloid level and cell death. In the present study, our data showed that both overexpression and knockdown of U1 snRNA could cause the loss in the function of U1 snRNA and resulted in PCPA as well as the same downstream phenomena including the expression changes of genes specific to AD, tau hyperphosphorylation on the site of Thr212, the decrease of acetylated α-tubulin, the reduction of cell viability and upregulation of RIPK1, RIPK3 and caspase8. These findings not only helped researchers better understand the functions of U1 snRNA, but also paved the way to reveal the mechanisms of AD from a different point of view and may find a new therapeutic target for the disease.