The multiple-step cleavage of amyloid precursor protein (APP) generates amyloid-β peptides (Aβ), highly toxic molecules causing Alzheimer's disease (AD). The nonspecific cleavage between the transmembrane region of APP (APPTM) and γ-secretase is the key step of Aβ generation. Reconstituting APPTM under physiologically-relevant conditions is crucial to investigate how it interacts with γ-secretase and for future AD drug discovery. Although producing recombinant APPTM was reported before, the large scale purification was hindered by the use of biological protease in the presence of membrane protein. Here, we expressed recombinant APPTM in Escherichia coli using the pMM-LR6 vector and recovered the fusion protein from inclusion bodies. By combining Ni-NTA chromatography, cyanogen bromide cleavage, and reverse phase high performance liquid chromatography (RP-HPLC), isotopically-labeled APPTM was obtained in high yield and high purity. The reconstitution of APPTM into dodecylphosphocholine (DPC) micelle generated mono dispersed 2D ¹⁵N-¹H HSQC spectra in high quality. We successfully established an efficient and reliable method for the expression, purification and reconstruction of APPTM, which may facilitate future investigation of APPTM and its complex in more native like membrane mimetics such as bicelle and nanodiscs.
Humans ; Amyloid beta-Protein Precursor/chemistry* ; Micelles ; Amyloid Precursor Protein Secretases/metabolism* ; Magnetic Resonance Spectroscopy ; Recombinant Proteins

OBJECTIVETo study the role of presenilin1 (PS1) in the processing of beta-amyloid precursor protein (APP) to amyloid beta-peptide (Abeta) and its relation to gamma-secretase in the pathogenesis of Alzheimer's disease (AD).

METHODSSeveral CHO cell lines stably transfected with either wide-type or mutant PS1 (M(146)L) along with APP(751) genes were established. The expression of PS1 and its half-life were determined by immunoprecipitation, Western blotting and pulse-chase experiment. Abeta released into the conditional media was quantitated by ELISA.

RESULTSPS1 transfected CHO cells expressed an expected 45,000 full length protein. This over-expressed full length PS1 was subject to fast degradation with a half-life of less than 1 hour. In contrast to full length PS1, the truncated N-terminal and C-terminal proteins of PS1 were significantly more stable with a longer half-life of nearly 16 hours. Although the total amount of Abeta released into the conditional media did not show a significant difference between wild-type and mutant PS1 (M(146)L) transfected APP cells, mutant PS1 (M(146)L) transfected APP cells increase Abeta(1 - 42) (a subspecies of total Abeta) production with nearly a 2 fold increase, comparing to untransfected or wild-type PS1 transfected APP cells.

CONCLUSIONPS1 is involved in the processing of APP to Abeta, a nearly 2 fold increase of Abeta production in mutant PS1 (M(146)L) transfected APP cells indicates that PS1 may be the expected gamma-secretase itself.

Alzheimer Disease ; etiology ; metabolism ; Amyloid Precursor Protein Secretases ; genetics ; metabolism ; Amyloid beta-Peptides ; metabolism ; Amyloid beta-Protein Precursor ; genetics ; Animals ; CHO Cells ; Cricetinae ; Cricetulus ; Mutation ; Peptide Fragments ; metabolism ; Presenilin-1 ; genetics ; metabolism ; Transfection

OBJECTIVETo explore the effect of Panax notoginseng saponin (PNS) on the activity and content of beta-secretase in the brain of senescence accelerated mouse-prone 8 (SAMP8) mice with Alzheimer's disease.

METHODSTotally 32 SAMP8 mice were randomly divided into the normal control group, the high dose PNS group (200 mg/kg), the low dose group (100 mg/kg), and the huperzine A group (0.3 mg/kg), 8 in each group. Equal volume of double distilled water was given to those in the normal control group. All medication was given by gastrogavage, once daily for two successive months. The activity of BACE1 was assayed by direct immunofluorescent method (DIF). The content of BACE1 protein was detected by Western blot.

RESULTSThe relative fluorescence units (RFU/microg) was 2.008 +/- 0.031 in the high dose PNS group, 2.221 +/- 0.029 in the low dose PNS group, and 2.267 +/- 0.076 in the huperzine A group, all lower than that in the normal control group (2.403 +/- 0.058; all P < 0.01). The content of BACE1 protein was 0.900 +/- 0.028 in the high dose PNS group, 1.000 +/- 0.032 in the low dose PNS group, and 0.837 +/- 0.080 in the huperzine A group, all lower than that in the normal control group (2.210 +/- 0.074, all P < 0.01).

CONCLUSIONPNS higher than 100 mg/kg could decrease the activity of BACE1 and down-regulate the content of BACE1 protein in the brain of SAMP8 mice.

Aging ; Alzheimer Disease ; metabolism ; Amyloid Precursor Protein Secretases ; metabolism ; Animals ; Aspartic Acid Endopeptidases ; metabolism ; Brain ; metabolism ; Disease Models, Animal ; Male ; Mice ; Panax notoginseng ; RNA, Messenger ; genetics ; Saponins ; pharmacology

Physalin B (PB), one of the major active steroidal constituents of Solanaceae Physalis plants, has a wide variety of biological activities. We found that PB significantly down-regulated β-amyloid (Aβ) secretion in N2a/APPsw cells. However, the underlying mechanisms are not well understood. In the current study, we investigated the changes in key enzymes involved in β-amyloid precursor protein (APP) metabolism and other APP metabolites by treating N2a/APPsw cells with PB at different concentrations. The results indicated that PB reduced Aβ secretion, which was caused by down-regulation of β-secretase (BACE1) expression, as indicated at both the protein and mRNA levels. Further research revealed that PB regulated BACE1 expression by inducing the activation of forkhead box O1 (FoxO1) and inhibiting the phosphorylation of signal transducer and activator of transcription 3 (STAT3). In addition, the effect of PB on BACE1 expression and Aβ secretion was reversed by treatment with FoxO1 siRNA and STAT3 antagonist S3I-201. In conclusion, these data demonstrated that PB can effectively down-regulate the expression of BACE1 to reduce Aβsecretion by activating the expression of FoxO1 and inhibiting the phosphorylation of STAT3.
Alzheimer Disease ; Amyloid Precursor Protein Secretases/metabolism* ; Amyloid beta-Peptides/metabolism* ; Aspartic Acid Endopeptidases/metabolism* ; Down-Regulation ; Forkhead Box Protein O1/genetics* ; Humans ; Phosphorylation ; STAT3 Transcription Factor/metabolism* ; Secosteroids

To generate active recombinant human beta-secreatase (BACE1) for studying its interaction with its inhibitors, we constructed two recombinant plasmids, pPIC9K-MetBACE22 (bearing pro-bace1 gene) and pPIC9K-MetBACE46 (bearing bace1 gene). These two plasmids were then transformed into Pichia pastoris GS115 by electroporation to obtain the recombinant strains 9k-B22 and 9k-B46. After induction in buffered methanol complex medium, we found the supernatant activity of 9k-B22 significantly higher than that of 9k-B46. The culture filtrate of 9k-B22 was concentrated, and then purified by HisTrap affinity column. The purified proteins, showing good BACE1 protease activity, were found to be a mixture of glycoproteins because they can be stained by periodic acid-Schiff reagent. After this mixture was treated with Endo H(f) (a recombinant protein of endoglycosidase H), we found two new adjacent bands around 50 kDa on SDS-PAGE. These two bands were cut and subjected to peptide mass fingerprint analysis, and identified as proBACE1 and BACE1 proteins. Enzyme assays revealed that the activities of both BACE1 proteins in glycosylated and deglycosylated form were lower than that of commercial BACE1 (expressed in HEK-293), inferring glycosylation and the type of glycosylation are crucial to the activity. However, we found no apparent difference in the inhibition of those all above three enzyme forms by one known BACE1 inhibitor. This observation demonstrated that the glycosylation of BACE1 by Pichia pastoris does not affect its interaction with this inhibitor. After optimization of culture conditions, the production of BACE1 in Pichia pastoris was enhanced to about 1 mg/L. This work enables us to further investigate the interaction of BACE1 and its inhibitors, and assists in discovering and optimizing BACE1 inhibitors as anti-Alzheimer's disease agents.
Amyloid Precursor Protein Secretases ; biosynthesis ; genetics ; Aspartic Acid Endopeptidases ; biosynthesis ; genetics ; Electroporation ; Humans ; Pichia ; genetics ; metabolism ; Plasmids ; genetics ; Recombinant Proteins ; biosynthesis ; genetics ; isolation & purification

OBJECTIVETo investigate the effects of exogenous hydrogen sulfide (H2S) on β-site APP cleaving enzyme 1 (BACE-1) and β-amyloid peptide (Aβ) metabolism in primary culture of neurons under high-glucose condition.

METHODSThe cortical neurons in primary culture under normal and high glucose (60 mmol/L) conditions for 24 h were exposed to 25, 50 and 100 µmol/L NaHS. Aβ1-42 concentration in the cell culture was measured by ELISA, and BACE-1 mRNA and protein levels were detected by fluorescent quantitative real-time PCR and Western blotting, respectively.

RESULTSCompared with the neurons cultured in normal glucose, the neurons exposed to high glucose showed significantly increased Aβ1-42 concentration and BACE-1 mRNA and protein expressions (P<0.05). Exposure to 25, 50 and 100 µmol/L NaHS significantly decreased Aβ1-42 concentration and BACE-1 mRNA and protein expressions in the high-glucose cell culture (P<0.05).

CONCLUSIONNeurons exposed to high glucose exhibit increased Aβ1-42 levels and BACE-1 mRNA and protein expressions, which can be concentration-dependently decreased by NaHS.

Amyloid Precursor Protein Secretases ; metabolism ; Amyloid beta-Peptides ; metabolism ; Animals ; Aspartic Acid Endopeptidases ; metabolism ; Cells, Cultured ; Culture Media ; chemistry ; Glucose ; chemistry ; Hydrogen Sulfide ; pharmacology ; Neurons ; drug effects ; metabolism ; Peptide Fragments ; metabolism ; Rats ; Rats, Sprague-Dawley

BACKGROUNDAmyloid β (Aβ) has been established as a key factor for the pathological changes in the brains of patients with Alzheimer's disease (AD), and cellular senescence is closely associated with aging and cognitive impairment. However, it remains blurred whether, in the AD brains, Aβ accelerates the neuronal senescence and whether this senescence, in turn, impairs the cognitive function. This study aimed to explore the expression of senescence-associated genes in the hippocampal tissue from young to aged 5XFAD mice and their age-matched wild type (WT) mice to determine whether senescent neurons are present in the transgenic AD mouse model.

METHODSThe 5XFAD mice and age-matched wild type mice, both raised from 1 to 18 months, were enrolled in the study. The senescence-associated genes in the hippocampus were analyzed and differentially expressed genes (DEGs) were screened by quantitative real-time polymerase chain reaction. Cognitive performance of the mice was evaluated by Y-maze and Morris water maze tests. Oligomeric Aβ (oAβ) (1-42) was applied to culture primary neurons to simulate the in vivo manifestation. Aging-related proteins were detected by Western blotting analysis and immunofluorescence.

RESULTSIn 5XFAD mice, of all the DEGs, the senescence-associated marker p16 was most significantly increased, even at the early age. It was mainly localized in neurons, with a marginal expression in astrocytes (labeled as glutamine synthetase), nil expression in activated microglia (labeled as Iba1), and negatively correlated with the spatial cognitive impairments of 5XFAD mice. oAβ (1-42) induced the production of senescence-related protein p16, but not p53 in vitro, which was in line with the in vivo manifestation.

CONCLUSIONSoAβ-accelerated neuronal senescence may be associated with the cognitive impairment in 5XFAD mice. Senescence-associated marker p16 can serve as an indicator to estimate the cognitive prognosis for AD population.

Alzheimer Disease ; metabolism ; physiopathology ; Amyloid Precursor Protein Secretases ; genetics ; metabolism ; Amyloid beta-Peptides ; metabolism ; Amyloid beta-Protein Precursor ; metabolism ; Animals ; Aspartic Acid Endopeptidases ; genetics ; metabolism ; Brain ; metabolism ; physiopathology ; Cells, Cultured ; Cellular Senescence ; genetics ; physiology ; Cognition ; physiology ; Cognition Disorders ; metabolism ; physiopathology ; Disease Models, Animal ; Male ; Mice ; Mice, Inbred C57BL ; Mice, Transgenic ; Neurons ; metabolism ; pathology ; Real-Time Polymerase Chain Reaction

OBJECTIVETo study the effects of Huannao Yicong Recipe (HNYCR)extract on the learning and memory ability, and the expressions of amyloid precursor protein (APP), beta-site APP-cleaving enzyme 1 (BACE1), presenilin-1 (PS-1), and beta amyloid protein (Abeta)in hippocampus CA1 area of APP transgenic mice, and to explore its mechanisms for treating Alzheimer's disease (AD).

METHODSTotally 3-month-old APP695V7171 transgenic mice were used to establish the AD model in this research. They were randomly divided into the model group, the Donepezil group, the large dose HNYCR extract group, the small dose HNYCR extract group, and the normal control group (C57BL/6J mice), 15 in each group. These animals were gavaged for 4 continuous months. Relevant indicators were detected: Morris water maze test was used to measure the spatial learning and memory ability. The immunohistochemical assay was used to detect the expressions of APP, BACE1, PS-1, and Abeta.

RESULTSThe times of crossing the original platform and the swimming time and distance in the fourth quadrant of the 7-month-old APP transgenic mice were significantly reduced in Morris water maze test, when compared with the normal control group (P < 0.01). The times of crossing original platform and the swimming time and distance in the fourth quadrant of all treatment groups significantly increased in Morris water maze test, when compared with the model group (P < 0.05). The expressions of APP, BACE1, PS-1, and Abeta in hippocampus CA1 area of 7-month-old model mice increased significantly (P < 0.01), when compared with the normal control group. The expressions of APP, BACE1, PS-1, and Abeta in each 7-month-old intervention groups were significantly reduced, when compared with the model group (P < 0.01).

CONCLUSIONEarly application of HNYCR extract can obviously improve the learning and memory ability of APP transgenic mice that has declined, reduce the expressions of APP, BACE1, PS-1, and Abeta in the hippocampal CA1 area, reduce the production of Abeta, and slow down the pathological process of brains in APP transgenic mice.

Alzheimer Disease ; metabolism ; Amyloid Precursor Protein Secretases ; genetics ; metabolism ; Amyloid beta-Peptides ; genetics ; metabolism ; Amyloid beta-Protein Precursor ; genetics ; metabolism ; Animals ; Aspartic Acid Endopeptidases ; genetics ; metabolism ; Brain ; drug effects ; metabolism ; CA1 Region, Hippocampal ; drug effects ; metabolism ; Disease Models, Animal ; Drugs, Chinese Herbal ; pharmacology ; Female ; Male ; Maze Learning ; drug effects ; Memory ; drug effects ; Mice ; Mice, Inbred C57BL ; Mice, Transgenic ; Presenilin-1 ; genetics ; metabolism

OBJECTIVETo investigate the expression of miR-140-5p and ADAM10 in hypopharyngeal carcinoma tissues and their effects on the migration and invasion of FaDu cells and underlying mechanism.

METHODSThe miR-140-5p and ADAM10 mRNA levels in 33 cases of hypopharyngeal carcinoma tissues and adjacent normal tissues were measured by real-time quantitative polymerase chain reaction (RT-qPCR). Transwell migration assay and transwell invasion assay were used to test the metastasis ability of FaDu cells after upregulation or downregulation of miR-140-5p and downregulation of ADAM10. The protein expression levels of ADAM10 in hypopharyngeal carcinoma tissues and the FaDu cells after transfection were determined by Western blot assays.

RESULTSThe expression level of miR-140-5p was significantly downregulated in hypopharyngeal carcinoma tissues compared with adjacent tissues (t=-4.016, P<0.01), which was significantly correlated with tumor classification and lymph node metastasis (P<0.05). Conversely, mRNA and protein expressions of ADAM10 were significantly upregulated in tumor tissues (t=3.960, P<0.01; t=12.089, P<0.01), and were significantly downregulated in the FaDu cells after tranfected with si-ADAM10 (t=8.653, P<0.05; t=5.191, P<0.05). Transwell assay showed that compare with control group, the migration and invasive cells decreased significantly in hsa-mir-140-5p group (t=3.255, P<0.05; t=2.942, P<0.05), while increased significantly in anti-hsa-mir-140-5p group, (t=-13.521, P<0.05; t=-6.223, P<0.05). The migration and invasive cells in si-ADAM10 group were less than those in control group (t=4.759, P<0.05; t=3.663, P<0.05). The downregulation of ADAM10 attenuated the effect of anti-mir-140-5p in FaDu cells. Western blot assay showed that ADAM10 expression was apparently decreased in hsa-mir-140-5p group and increased in anti-mir-140-5p group compared with control group.

CONCLUSIONSThe expression of miR-140-5p was significantly downregulated in hypopharyngeal carcinoma tissues and correlated with tumor classification and lymph node metastasis. ADAM10 was upregulated in tumor tissues. MiR-140-5p suppresses the migration and invasion abilities of FaDu cells, possibly through downregulation of ADAM10.

ADAM Proteins ; metabolism ; ADAM10 Protein ; Amyloid Precursor Protein Secretases ; metabolism ; Cell Line, Tumor ; Cell Movement ; Down-Regulation ; Gene Expression Regulation, Neoplastic ; Humans ; Hypopharyngeal Neoplasms ; pathology ; Lymphatic Metastasis ; Membrane Proteins ; metabolism ; MicroRNAs ; metabolism ; RNA, Messenger ; metabolism ; Transfection

AIMTo investigate the inhibition of amyloid beta-protein 42 (Abeta42) production in M146L cells by gamma-schisandrin.

METHODSM146L cells which can produce considerable Abeta42 in vitro were treated with gamma-schisandrin (1.67, 5.00 and 15.00 microg x mL(-1)), beta-secretase inhibitor (S4562, 100.00 microg x mL(-1)) and gamma-secretase inhibitor (S2188, 13.68 microg x mL(-1)), separately. Cell counting kit-8 (CCK-8) was used to assess cell viability. Enzyme-linked immunosorbent assay (ELISA) was carried out to determine the amount of Abeta42. Western blotting was used to examine C99, an intermediary product of APP cleaved by beta-secretase. beta-Secretase and gamma-secretase activities were assayed by commercial kits.

RESULTSThe CCK-8 assay indicated that different concentrations of gamma-schisandrin had no neurotoxicity on the cultured M146L. And the ELISA test showed that the amount of Abeta42 secreted by M146L cells treated with gamma-schisandrin (5.00 and 15.00 microg x mL(-1)) decreased obviously as compared with solvent control. The results of Western blotting test indicated that there was no change of C99 contents and beta-secretase activity in gamma-schisandrin treated cells, while gamma-secretase activity decreased obviously.

CONCLUSIONgamma-Schisandrin inhibited production of Abeta42 in M146L cells through inhibiting gamma-secretase.

Alzheimer Disease ; drug therapy ; Amyloid Precursor Protein Secretases ; antagonists & inhibitors ; metabolism ; Amyloid beta-Peptides ; antagonists & inhibitors ; biosynthesis ; Animals ; CHO Cells ; Cricetinae ; Cricetulus ; Cyclooctanes ; Dose-Response Relationship, Drug ; Humans ; Lignans ; Peptide Fragments ; antagonists & inhibitors ; biosynthesis ; Polycyclic Compounds ; pharmacology