STAU1 exhibits a dual function by promoting amyloidogenesis and tau phosphorylation in cultured cells.

Staufen-1 (STAU1) is a double-stranded RNA-binding protein (RBP) involved in a variety of pathological conditions. In this study, we investigated the potential role of STAU1 in Alzheimer's disease (AD), in which two hallmarks are well-established as cerebral ß-amyloid protein (Aß) deposition and Tau-centered neurofibrillary tangles. We found that STAU1 protein level was significantly increased in cells that stably express full-length APP and the brain of APP/PS1 mice, an animal model of AD. STAU1 knockdown, as opposed to overexpression, significantly decreased the protein levels of ß-amyloid converting enzyme 1 (BACE1) and Aß. We further found that STAU1 extended the half-life of the BACE1 mRNA through binding to the 3' untranslated region (3'UTR). Transcriptome analysis revealed that STAU1 enhanced the expression of growth arrest and DNA damage 45 ß (GADD45B) upstream of P38 MAPK signaling, which contributed to STAU1-induced regulation of Tau phosphorylation at Ser396 and Thr181. Together, STAU1 promoted amyloidogenesis by inhibiting BACE1 mRNA decay, and augmented Tau phosphorylation through activating GADD45B in relation to P38 MAPK. Targeting STAU1 that acts on both amyloidogenesis and tauopathy may serve as an optimistic approach for AD treatment.

Short-term regulation of TSFM level does not alter amyloidogenesis and mitochondrial function in type-specific cells.

BACKGROUND: Mitochondrial Ts translation elongation factor (TSFM) is an enzyme that catalyzes exchange of guanine nucleotides. By forming a complex with mitochondrial Tu translation elongation factor (TUFM), TSFM participates in mitochondrial protein translation. We have previously reported that TUFM regulates translation of beta-site APP cleaving enzyme 1 (BACE1) via ROS (reactive oxygen species)-dependent mechanism, suggesting a potential role in amyloid precursor protein (APP) processing associated with Alzheimer's disease (AD), which led to the speculation that TSFM may regulate APP processing in a similar way to TUFM. METHODS AND RESULTS: Here, we report that in cultured cells, knockdown or overexpression TSFM did not change protein levels in BACE1 and APP. Besides, the levels of cytoplasmic ROS and mitochondrial superoxide, in addition to ATP level, cell viability and mitochondrial membrane potential were not significantly altered by TSFM knockdown in the short term. Further transcriptome analysis revealed that expression of majority of mitochondrial genes were not remarkably changed by TSFM silencing. The possibility of TSFM involved in cardiomyopathy and cancer development was uncovered using bioinformatics analysis. CONCLUSIONS: Collectively, short-term regulation of TSFM level in cultured cells does not cause a significant change in proteins involved in APP processing, levels in ROS and ATP associated with mitochondrial function. Whereas our study could contribute to comprehend certain clinical features of TSFM mutations, the roles of TSFM in cardiomyopathy and cancer development might deserve further investigation.

SHMT2 Mediates Small-Molecule-Induced Alleviation of Alzheimer Pathology Via the 5'UTR-dependent ADAM10 Translation Initiation.

It is long been suggested that one-carbon metabolism (OCM) is associated with Alzheimer's disease (AD), whereas the potential mechanisms remain poorly understood. Taking advantage of chemical biology, that mitochondrial serine hydroxymethyltransferase (SHMT2) directly regulated the translation of ADAM metallopeptidase domain 10 (ADAM10), a therapeutic target for AD is reported. That the small-molecule kenpaullone (KEN) promoted ADAM10 translation via the 5' untranslated region (5'UTR) and improved cognitive functions in APP/PS1 mice is found. SHMT2, which is identified as a target gene of KEN and the 5'UTR-interacting RNA binding protein (RBP), mediated KEN-induced ADAM10 translation in vitro and in vivo. SHMT2 controls AD signaling pathways through binding to a large number of RNAs and enhances the 5'UTR activity of ADAM10 by direct interaction with GAGGG motif, whereas this motif affected ribosomal scanning of eukaryotic initiation factor 2 (eIF2) in the 5'UTR. Together, KEN exhibits therapeutic potential for AD by linking OCM with RNA processing, in which the metabolic enzyme SHMT2 "moonlighted" as RBP by binding to GAGGG motif and promoting the 5'UTR-dependent ADAM10 translation initiation.

ARL6IP1 mediates small-molecule-induced alleviation of Alzheimer pathology through FXR1-dependent BACE1 translation initiation.

Exploring the potential lead compounds for Alzheimer's disease (AD) remains one of the challenging tasks. Here, we report that the plant extract conophylline (CNP) impeded amyloidogenesis by preferentially inhibiting BACE1 translation via the 5' untranslated region (5'UTR) and rescued cognitive decline in an animal model of APP/PS1 mice. ADP-ribosylation factor-like protein 6-interacting protein 1 (ARL6IP1) was then found to mediate the effect of CNP on BACE1 translation, amyloidogenesis, glial activation, and cognitive function. Through analysis of the 5'UTR-targetd RNA-binding proteins by RNA pulldown combined with LC-MS/MS, we found that FMR1 autosomal homolog 1 (FXR1) interacted with ARL6IP1 and mediated CNP-induced reduction of BACE1 by regulating the 5'UTR activity. Without altering the protein levels of ARL6IP1 and FXR1, CNP treatment promoted ARL6IP1 interaction with FXR1 and inhibited FXR1 binding to the 5'UTR both in vitro and in vivo. Collectively, CNP exhibited a therapeutic potential for AD via ARL6IP1. Through pharmacological manipulation, we uncovered a dynamic interaction between FXR1 and the 5'UTR in translational control of BACE1, adding to the understanding of the pathophysiology of AD.

TNIP2 inhibits amyloidogenesis by regulating the 3'UTR of BACE1: An in vitro study.

TNFAIP3-interacting protein 2 (TNIP2) is known as a negative regulator of NF-κB signaling and inhibit inflammatory response and apoptosis, and is also involved in RNA metabolism. In this study, we investigated the potential role of TNIP2 in amyloidogenesis critically associated with Alzheimer's disease (AD). We found a significant decline of TNIP2 protein level in both mouse and cell model of AD. In SH-SY5Y and HEK cells that stably express human full-length APP695 (SY5Y-APP and HEK-APP), TNIP2 overexpression decreased the protein levels of ß-secretase (BACE1) and C99, as well as Aß peptides (including Aß40 and Aß42), while those of α-secretase (ADAM10) and the related C83 remained unchanged. We further found that TNIP2 promoted the degradation of BACE1 mRNA and was able to bound to the 3' untranslated region (3'UTR) with the reduced luciferase activity. These results indicated that TNIP2 effectively inhibited amyloidogenic processing by regulating the 3'UTR-associated mRNA decay of BACE1.

Apicidin attenuates memory deficits by reducing the Aß load in APP/PS1 mice.

AIMS: Amyloid beta (Aß) is an important pathological feature of Alzheimer's disease (AD). A disintegrin and metalloproteinase 10 (ADAM10) can reduce the production of toxic Aß by activating the nonamyloidogenic pathway of amyloid precursor protein (APP). We previously found that apicidin, which is a histone deacetylase (HDAC) inhibitor, can promote the expression of ADAM10 and reduce the production of Aß in vitro. This study was designed to determine the potential of apicidin treatment to reverse learning and memory impairments in an AD mouse model and the possible correlation of these effects with ADAM10. METHODS: Nine-month-old APP/PS1 mice and C57 mice received intraperitoneal injections of apicidin or vehicle for 2 months. At 11 months of age, we evaluated the memory performance of mice with Morris water maze (MWM) and context fear conditioning tests. The Aß levels were assessed in mouse brain using the immunohistochemical method and ELISA. The expression of corresponding protein involved in proteolytic processing of APP and the phosphorylation of tau were assessed by Western blotting. RESULTS: Apicidin reversed the deficits of spatial reference memory and contextual fear memory, attenuated the formation of Aß-enriched plaques, and decreased the levels of soluble and insoluble Aß40/42 in APP/PS1 mice. Moreover, apicidin significantly increased the expression of ADAM10, improved the level of sAPPα, and reduced the production of sAPPß, but did not affect the levels of phosphorylated tau in APP/PS1 mice. CONCLUSION: Apicidin significantly improves the AD symptoms of APP/PS1 mice by regulating the expression of ADAM10, which may contribute to decreasing the levels of Aß rather than decreasing the phosphorylation of tau.

AP2S1 regulates APP degradation through late endosome-lysosome fusion in cells and APP/PS1 mice.

AP2S1 is the sigma 2 subunit of adaptor protein 2 (AP2) that is essential for endocytosis. In this study, we investigated the potential role of AP2S1 in intracellular processing of amyloid precursor protein (APP), which contributes to the pathogenesis of Alzheimer disease (AD) by generating the toxic ß-amyloid peptide (Aß). We found that knockdown or overexpression of AP2S1 decreased or increased the protein levels of APP and Aß in cells stably expressing human full-length APP695, respectively. This effect was unrelated to endocytosis but involved lysosomal degradation. Morphological studies revealed that silencing of AP2S1 promoted the translocalization of APP from RAB9-positive late endosomes (LE) to LAMP1-positive lysosomes, which was paralleled by the enhanced LE-lysosome fusion. In support, silencing of vacuolar protein sorting-associated protein 41 (VPS41) that is implicated in LE-lyso fusion prevented AP2S1-mediated regulation of APP degradation and translocalization. In APP/PS1 mice, an animal model of AD, AAV-mediated delivery of AP2S1 shRNA in the hippocampus significantly reduced the protein levels of APP and Aß, with the concomitant APP translocalization, LE-lyso fusion and the improved cognitive functions. Taken together, these data uncover a LE-lyso fusion mechanism in APP degradation and suggest a novel role for AP2S1 in the pathophysiology of AD.

HMGCS2-Induced Autophagic Degradation of Tau Involves Ketone Body and ANKRD24.

BACKGROUND: Accumulation of hyperphosphorylated Tau (pTau) contributes to the formation of neurofibrillary tangles in Alzheimer's disease (AD), and targeting Tau/pTau metabolism has emerged as a therapeutic approach. We have previously reported that mitochondrial 3-hydroxy-3-methylglutaryl-COA synthase 2 (HMGCS2) is involved in AD by promoting autophagic clearance of amyloid-ß protein precursor via ketone body-associated mechanism, whether HMGCS2 may also regulate Tau metabolism remains elusive. OBJECTIVE: The present study was to investigate the role of HMGCS2 in Tau/p degradation. METHODS: The protein levels of Tau and pTau including pT217 and pT181, as well as autophagic markers LAMP1 and LC3-II were assessed by western blotting. The differentially regulated genes by HMGCS2 were analyzed by RNA sequencing. Autophagosomes were assessed by transmission electron microscopy. RESULTS: HMGCS2 significantly decreased Tau/pTau levels, which was paralleled by enhanced formation of autophagic vacuoles and prevented by autophagic regulators chloroquine, bafilomycin A1, 3-methyladenine, and rapamycin. Moreover, HMGCS2-induced alterations of LAMP1/LC3-II and Tau/pTau levels were mimicked by ketone body acetoacetate or ß-hydroxybutyrate. Further RNA-sequencing identified ankyrin repeat domain 24 (ANKRD24) as a target gene of HMGCS2, and silencing of ANKRD24 reduced LAMP1/LC3-II levels, which was accompanied by the altered formation of autophagic vacuoles, and diminished the effect of HMGCS2 on Tau/pTau. CONCLUSION: HMGCS2 promoted autophagic clearance of Tau/pTau, in which ketone body and ANKRD24 played an important role.

Sulfuretin exerts diversified functions in the processing of amyloid precursor protein.

Sulfuretin is a flavonoid that protects cell from damage induced by reactive oxygen species and inflammation. In this study, we investigated the role of sulfuretin in the processing of amyloid precursor protein (APP), in association with the two catalytic enzymes the α-secretase a disintegrin and metalloproteinase (ADAM10), and the beta-site APP cleaving enzyme 1 (BACE1) that play important roles in the generation of ß amyloid protein (Aß) in Alzheimer's disease (AD). We found that sulfuretin increased the levels of the immature but not the mature form of ADAM10 protein. The enhanced ADAM10 transcription by sulfuretin was mediated by the nucleotides -444 to -300 in the promoter region, and was attenuated by silencing or mutation of transcription factor retinoid X receptor (RXR) and by GW6471, a specific inhibitor of peroxisome proliferator-activated receptor α (PPAR-α). We further found that sulfuretin preferentially increased protein levels of the immature form of APP (im-APP) but significantly reduced those of BACE1, sAPPß and ß-CTF, whereas Aß1-42 levels were slightly increased. Finally, the effect of sulfuretin on BACE1 and im-APP was selectively attenuated by the translation inhibitor cycloheximide and by lysosomal inhibitor chloroquine, respectively. Taken together, (1) RXR/PPAR-α signaling was involved in sulfuretin-mediated ADAM10 transcription. (2) Alteration of Aß protein level by sulfuretin was not consistent with that of ADAM10 and BACE1 protein levels, but was consistent with the elevated level of im-APP protein, suggesting that im-APP, an isoform mainly localized to trans-Golgi network, plays an important role in Aß generation.

TUFM is involved in Alzheimer's disease-like pathologies that are associated with ROS.

Mitochondrial Tu translation elongation factor (TUFM or EF-Tu) is part of the mitochondrial translation machinery. It is reported that TUFM expression is reduced in the brain of Alzheimer's disease (AD), suggesting that TUFM might play a role in the pathophysiology. In this study, we found that TUFM protein level was decreased in the hippocampus and cortex especially in the aged APP/PS1 mice, an animal model of AD. In HEK cells that stably express full-length human amyloid-ß precursor protein (HEK-APP), TUFM knockdown or overexpression increased or reduced the protein levels of ß-amyloid protein (Aß) and ß-amyloid converting enzyme 1 (BACE1), respectively. TUFM-mediated reduction of BACE1 was attenuated by translation inhibitor cycloheximide (CHX) or α-[2-[4-(3,4-Dichlorophenyl)-2-thiazolyl]hydrazinylidene]-2-nitro-benzenepropanoic acid (4EGI1), and in cells overexpressing BACE1 constructs deleting the 5' untranslated region (5'UTR). TUFM silencing increased the half-life of BACE1 mRNA, suggesting that RNA stability was affected by TUFM. In support, transcription inhibitor Actinomycin D (ActD) and silencing of nuclear factor κB (NFκB) failed to abolish TUFM-mediated regulation of BACE1 protein and mRNA. We further found that the mitochondria-targeted antioxidant TEMPO diminished the effects of TUFM on BACE1, suggesting that reactive oxygen species (ROS) played an important role. Indeed, cellular ROS levels were affected by TUFM knockdown or overexpression, and TUFM-mediated regulation of apoptosis and Tau phosphorylation at selective sites was attenuated by TEMPO. Collectively, TUFM protein levels were decreased in APP/PS1 mice. TUFM is involved in AD pathology by regulating BACE1 translation, apoptosis, and Tau phosphorylation, in which ROS plays an important role.

Mitochondrial TXN2 attenuates amyloidogenesis via selective inhibition of BACE1 expression.

Thioredoxin-2 (TXN2) is a mitochondrial protein and represents one of the intrinsic antioxidant enzymes. It has long been recognized that mitochondrial dysfunction and oxidative stress contribute to the pathogenesis of Alzheimer's disease (AD). We hypothesized that mitochondrial TXN2 might play a role in AD-like pathology. In this study, we found that in SH-SY5Y and HEK cells stably express full-length human amyloid-ß precursor protein (HEK-APP), TXN2 silencing or over-expression selectively increased or decreased the transcription of beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), respectively, without altering the protein levels of others enzymes involved in the catalytic processing of APP. As a result, ß-amyloid protein (Aß) levels were significantly decreased by TXN2. In addition, in cells treated with 3-nitropropionic acid (3-NP) that is known to increase reactive oxygen species (ROS) and promote mitochondrial dysfunction, TXN2 silencing resulted in further enhancement of BACE1 protein levels, suggesting a role of TXN2 in ROS removal. The downstream signaling might involve NFκB, as TXN2 reduced the phosphorylation of p65 and IκBα; and p65 knockdown significantly attenuated TXN2-mediated regulation of BACE1. Concomitantly, the levels of cellular ROS, apoptosis-related proteins and cell viability were altered by TXN2 silencing or over-expression. In APPswe/PS1E9 mice, an animal model of AD, the cortical and hippocampal TXN2 protein levels were decreased at 12 months but not at 6 months, suggesting an age-dependent decline. Collectively, TXN2 regulated BACE1 expression and amyloidogenesis via cellular ROS and NFκB signaling. TXN2 might serve as a potential target especially for early intervention of AD.

[The establishment of diagnosis model on occupational medicamentosa-like dermatitis induced by trichloroethylene].

OBJECTIVE: Based on magnetic beads based weak cation exchange chromatography (MB-WCX), matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) and ClinProTools software, the polypeptides of serum about occupational medicamentosa-like dermatitis induced by trichloroethylene (OMLDT) patients were studied, and a diagnostic model of OMLDT was built. METHODS: According to diagnostic criteria of OMLDT, serum of 28 OMLDT patients and 28 controls which were diagnosed by Shenzhen prevention and treatment center for occupational disease were collected. With the combination of MB-WCX and MALDI-TOF-MS, the polypeptides fingerprint of serum of 14 OMLDT patients and 14 controls were detected, what's more, the ClinProTools software and SNN algorithm was used for screening characteristic polypeptides and establishing diagnostic model of OMLDT. Then other objects were applied to validate the model to evaluate accuracy. RESULTS: A total of 159 peaks were attained by ClinProTools software, of which 33 peaks were statistical content (P < 0.05). What is more, comparing with the control group, 20 peaks in case group were decreased, and 13 peaks were increased. Two peaks of them were identified, that is 2106.29 and 3263.78, to classify and determine that two groups by receiver operating characteristic curve (ROC) analysis.2D peaks distribution map certified this finding and the area under the ROC curve was closed to 1. A model was established by SNN algorithm, whose cross validation and recognition capability were 87.5% and 98.5%, respectively. Its sensitivity and specificity were 84.8% and 82.1%, separately, which displayed good separating capacity. CONCLUSION: In the combination of MB-WCX, MALDI-TOF-MS and ClinProTools software, specifical different polypeptides were screened and OMLDT diagnostic model was built primarily. Also, the model and the results were positively validated, which would play a significant role in early diagnosis.

[Dynamic change study of dermatitis medicamentosa-like of trichloroethylene patients with liver damage].

OBJECTIVE: Observing the dynamic change characteristics of serum liver function indexes in occupational dermatitis medicamentosa-like of trichloroethylene patients with liver damage, we can underlie for guiding therapy, prognosis and mechanism of dermatitis medicamentosa-like of trichloroethylene patients with liver damage. METHODS: We collected serum of 10 cases of occupational dermatitis medicamentosa-like of trichloro-ethylene patients with liver damage from different time points since they were hospitalized, using automatic biochemistry analyzer to detect total protein (TP), albumin (ALB), total bilirubin (TBIL), direct bilirubin (DBIL), indirect bilirubin (IBIL), alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transpeptidase (GGT), alkaline phosphatase (ALP), albumin/globulin ratio etc 11 liver function biochemical indicators. We used Excel to establish database, professional drawing software gnuplot to draw dynamic variation diagram of each index. RESULTS: The variation range of 11 liver function indexes of 10 cases was TP 43.2-74.2 g/L, ALB 24.6-44.6 g/L, A/G 0.77-2.10, TBIL 3.7-268.2 umol/L, DBIL 1.0-166.0 umol/L, IBIL 2.4 -167.5 umol/L, ALT 11-5985 U/L, AST 14-5586 U/L, GGT 15-1500 U/L, ALP 35-309 U/L, S/L 0.07-1.94, respectively. TBIL, DBIL, ALT, AST, GGT, ALP concentration significantly increased, especially ALT, AST, GGT, ALT topped 5985 U/L, AST topped 5586 U/L, GGT topped 1500 U/L. But TP, ALB and S/L significantly decreased, TP lowest to 43.2 g/L, S/L lowest to 0.07. A/G basically remained unchanged, but IBIL didn't change regularly. CONCLUSION: The early liver damage in dermatitis medicamentosa-like of trichloroethylene patients was serious, and repeatedly attacked, so we should lead to enough attention to the clinical work and prevention. This also provided the basis for studying the mechanism of trichloroethylene poisoning.

[Effect of potassium iodide on prevention of experimental lead nephropathy and expression of nuclear factor-kappaB and fibronectin].

OBJECTIVE: To investigate the effect of potassium iodide on the expression of nuclear factor-kappaB and fibronectin. METHODS: The experiment was performed with 72 SD rats weighing about 180-220 g. The animals were randomly assigned into nine groups. Group A, B, C (n=8) served as control and were fed with distilled water for 1 month, 2 month, 3 month respectively. Group D, E, F (n=8) served as lead exposed and were fed with water with 0.5% lead acetate for 1 month, 2 month, 3 month respectively. Group G, H, I (n=8) served as potassium iodide and lead exposed and were treated with 0.5% lead acetate simultaneously taking potassium iodide 3 mg/100 g weight by intragastric administration for 1 month, 2 month, 3 month respectively. Animals of different groups were sacrificed at the end of the treatment. Ultrastructure of kidney was observed by electron microscopy; Expression of NF-kappaB and FN protein and mRNA in kidney were measured respectively by immunohistochemistry and RT-PCR. RESULTS: Electron microscopic examination revealed potassium iodide could restrain the denaturalization in epithelial cells and mitochondrial cristae. The expressions of NF-kappaB protein (0.2315 +/- 0.0624, 0.3213 +/- 0.0740, 0.4729 +/- 0.0839) and mRNA (0.4370 +/- 0.0841, 0.5465 +/- 0.0503, 0.6443 +/- 0.0538) in all the lead exposed groups continuously increased compared with correspondent control groups; Group I was decreased obviously compared with group F. The expressions of FN protein (0.4243 +/- 0.0595, 0.4917 +/- 0.0891) and mRNA (0.8650 +/- 0.0880, 0.8714 +/- 0.0980) in group E and F increased compared with group B and C, but the expressions of FN protein in group I significantly decreased compared with group F; The expressions of FN mRNA in Group H and I significantly decreased compared with group E and F. CONCLUSION: The potassium iodide can ameliorate renal ultrastructure and degrade expression of nuclear factor-kappaB and fibronectin induced by lead.