| 41. |
- Gkanatsiou, Eleni, et al.
(författare)
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A distinct brain beta amyloid signature in cerebral amyloid angiopathy compared to Alzheimer's disease.
- 2019
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Ingår i: Neuroscience letters. - : Elsevier BV. - 1872-7972 .- 0304-3940. ; 701, s. 125-131
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Tidskriftsartikel (refereegranskat)abstract
- Cerebral amyloid angiopathy (CAA) is a type of vascular disease present in more than 50% of demented elderly and more than 80% of Alzheimer's disease (AD) patients. Both CAA and AD are characterized by extracellular Aβ deposits with the distinction that CAA has vascular deposits while AD has amyloid plaques. In this study, we used immunoprecipitation (IP) in combination with mass spectrometry (MS) to test the hypothesis that the Aβ peptide pattern differs between subjects having Aβ plaque pathology only and subjects with Aβ plaque pathology together with CAA pathology. Occipital lobes from 12 AD brains, ranging from no CAA to severe CAA, were extracted using 70% formic acid followed by IP-MS analysis. The Aβ peptide pattern differed greatly between subjects with no CAA compared to subjects with CAA. In cases with CAA, the most abundant Aβ peptides ended at amino acid 40 including Aβ1-40 (P=.048) and Aβ 2-40 (P=.0253) which were significantly increased compared to cases with no CAA. This was in contrast to subjects with no CAA where the most abundant Aβ peptides ended at amino acid 42 of which Aβ1-42 (P=.0101) and Aβ2-42 (P=.0051) as well as the pyroglutamate (pGlu)-modified peptides pGlu Aβ3-42 (P=.0177), and pGlu Aβ11-42 (P=.0088) were significantly increased compared to CAA subjects. The results are in line with earlier immunohistochemistry data and show that the molecular composition of the Aβ deposits found in blood vessels are different to the parenchymal deposits, suggesting they arise from distinct pathogenic pathways. This information may be useful in the development of pathology-specific biomarkers.
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| 42. |
- Gkanatsiou, Eleni, et al.
(författare)
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Amyloid pathology and synaptic loss in pathological aging
- 2021
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Ingår i: Journal of Neurochemistry. - : Wiley. - 0022-3042 .- 1471-4159. ; 159:2, s. 258-272
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Tidskriftsartikel (refereegranskat)abstract
- Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive memory dysfunction and cognitive decline. Pathological aging (PA) describes patients who are amyloid-positive but cognitively unimpaired at time of death. Both AD and PA contain amyloid plaques dominated by amyloid beta (A beta) peptides. In this study, we investigated and compared synaptic protein levels, amyloid plaque load, and A beta peptide patterns between AD and PA. Two cohorts of post-mortem brain tissue were investigated. In the first, consisting of controls, PA, AD, and familial AD (FAD) individuals, synaptic proteins extracted with tris(hydroxymethyl)aminomethane-buffered saline (TBS) were analyzed. In the second, consisting of tissue from AD and PA patients from three different regions (occipital lobe, frontal lobe, and cerebellum), a two-step extraction was performed. Five synaptic proteins were extracted using TBS, and from the remaining portion A beta peptides were extracted using formic acid. Subsequently, immunoprecipitation with several antibodies targeting different proteins/peptides was performed for both fractions, which were subsequently analyzed by mass spectrometry. The levels of synaptic proteins were lower in AD (and FAD) compared with PA (and controls), confirming synaptic loss in AD patients. The amyloid plaque load was increased in AD compared with PA, and the relative amount of A beta 40 was higher in AD while for A beta 42 it was higher in PA. In AD loss of synaptic function was associated with increased plaque load and increased amounts of A beta 40 compared with PA cases, suggesting that synaptic function is preserved in PA cases even in the presence of A beta.
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| 43. |
- Gkanatsiou, Eleni, et al.
(författare)
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Characterization of monomeric and soluble aggregated Aβ in Down's syndrome and Alzheimer's disease brains.
- 2021
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Ingår i: Neuroscience letters. - : Elsevier BV. - 1872-7972 .- 0304-3940. ; 754
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Tidskriftsartikel (refereegranskat)abstract
- The major characteristics of Alzheimer's disease (AD) are amyloid plaques, consisting of aggregated beta amyloid (Aβ) peptides, together with tau pathology (tangles, neuropil treads and dystrophic neurites surrounding the plaques), in the brain. Down's syndrome (DS) individuals are at increased risk to develop AD-type pathology; most DS individuals have developed substantial pathology already at the age of 40. DS individuals have an extra copy of chromosome 21, harbouring the amyloid precursor protein gene (APP). Our aim was to investigate the Aβ peptide pattern in DS and AD brains to investigate differences in their amyloid deposition and aggregation, respectively. Cortical tissue from patients with DS (with amyloid pathology), sporadic AD and controls were homogenized and fractionated into TBS (water soluble) and formic acid (water insoluble) fractions. Immunoprecipitation (IP) was performed using a variety of antibodies targeting different Aβ species including oligomeric Aβ. Mass spectrometry was then used to evaluate the presence of Aβ species in the different patient groups. A large number of Aβ peptides were identified including Aβ1-X, 2-X, 3-X, 4-X, 5-X, 11-X, and Aβ peptides extended N terminally of the BACE1 cleavage site and ending at amino 15 in the Aβ sequence APP/Aβ(-X to 15), as well as peptides post-translationally modified by pyroglutamate formation. Most Aβ peptides had higher abundance in AD and DS compared to controls, except the APP/Aβ(-X to 15) peptides which were most abundant in DS followed by controls and AD. Furthermore, the abundancies of AβX-40 and AβX-34 were increased in DS compared with AD. Aβ1-40, Aβ1-42, and Aβ4-42 were identified as the main constitutes of protofibrils (IP'd using mAb158) and higher relative Aβ1-42 signals were obtained compared with samples IP'd with 6E10+4G8, indicating that the protofibrils/oligomers were enriched with peptides ending at amino acid 42. All Aβ peptides found in AD were also present in DS indicating similar pathways of Aβ peptide production, degradation and accumulation, except for APP/Aβ(-X to 15). Likewise, the Aβ peptides forming protofibrils/oligomers in both AD and DS were similar, implying the possibility that treatment with clinical benefit in sporadic AD might also be beneficial for subjects with DS.
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| 44. |
- Grant, Marianne K O, et al.
(författare)
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Human cerebrospinal fluid 6E10-immunoreactive protein species contain amyloid precursor protein fragments.
- 2019
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Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 14:2
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Tidskriftsartikel (refereegranskat)abstract
- In a previous study, we reported that levels of two types of protein species-a type of ~55-kDa species and a type of ~15-kDa species-are elevated in the lumbar cerebrospinal fluid (CSF) of cognitively intact elderly individuals who are at risk for Alzheimer's disease (AD). These species are immunoreactive to the monoclonal antibody 6E10, which is directed against amino acids 6-10 of amyloid-β (Aβ), and their levels correlate with levels of total tau and tau phosphorylated at Thr181. In this study, we investigated the molecular composition of these AD-related proteins using immunoprecipitation (IP)/Western blotting coupled with IP/mass spectrometry. We show that canonical Aβ1-40/42 peptides, together with amyloid-β precursor protein (APP) fragments located N-terminally of Aβ, are present in the ~55-kDa, 6E10-immunoreactive species. We demonstrate that APP fragments located N-terminally of Aβ, plus the N-terminal region of Aβ, are present in the ~15-kDa, 6E10-immunoreactive species. These findings add to the catalog of AD-related Aβ/APP species found in CSF and should motivate further study to determine whether these species may serve as biomarkers of disease progression.
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| 45. |
- Halim, Adnan, et al.
(författare)
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Site-specific characterization of threonine, serine, and tyrosine glycosylations of amyloid precursor protein/amyloid {beta}-peptides in human cerebrospinal fluid.
- 2011
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 1091-6490. ; 108:29, s. 11848-53
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Tidskriftsartikel (refereegranskat)abstract
- The proteolytic processing of human amyloid precursor protein (APP) into shorter aggregating amyloid β (Aβ)-peptides, e.g., Aβ1-42, is considered a critical step in the pathogenesis of Alzheimer's disease (AD). Although APP is a well-known membrane glycoprotein carrying both N- and O-glycans, nothing is known about the occurrence of released APP/Aβ glycopeptides in cerebrospinal fluid (CSF). We used the 6E10 antibody and immunopurified Aβ peptides and glycopeptides from CSF samples and then liquid chromatography-tandem mass spectrometry for structural analysis using collision-induced dissociation and electron capture dissociation. In addition to 33 unglycosylated APP/Aβ peptides, we identified 37 APP/Aβ glycopeptides with sialylated core 1 like O-glycans attached to Thr(-39, -21, -20, and -13), in a series of APP/AβX-15 glycopeptides, where X was -63, -57, -52, and -45, in relation to Asp1 of the Aβ sequence. Unexpectedly, we also identified a series of 27 glycopeptides, the Aβ1-X series, where X was 20 (DAEFRHDSGYEVHHQKLVFF), 19, 18, 17, 16, and 15, which were all uniquely glycosylated on Tyr10. The Tyr10 linked O-glycans were (Neu5Ac)(1-2)Hex(Neu5Ac)HexNAc-O- structures with the disialylated terminals occasionally O-acetylated or lactonized, indicating a terminal Neu5Acα2,8Neu5Ac linkage. We could not detect any glycosylation of the Aβ1-38/40/42 isoforms. We observed an increase of up to 2.5 times of Tyr10 glycosylated Aβ peptides in CSF in six AD patients compared to seven non-AD patients. APP/Aβ sialylated O-glycans, including that of a Tyr residue, the first in a mammalian protein, may modulate APP processing, inhibiting the amyloidogenic pathway associated with AD.
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| 46. |
- Hanbouch, L., et al.
(författare)
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Specific Mutations in the Cholesterol-Binding Site of APP Alter Its Processing and Favor the Production of Shorter, Less Toxic A beta Peptides
- 2022
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Ingår i: Molecular Neurobiology. - : Springer Science and Business Media LLC. - 0893-7648 .- 1559-1182. ; 59, s. 7056-7073
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Tidskriftsartikel (refereegranskat)abstract
- Excess brain cholesterol is strongly implicated in the pathogenesis of Alzheimer's disease (AD). Here we evaluated how the presence of a cholesterol-binding site (CBS) in the transmembrane and juxtamembrane regions of the amyloid precursor protein (APP) regulates its processing. We generated nine point mutations in the APP gene, changing the charge and/or hydrophobicity of the amino-acids which were previously shown as part of the CBS. Most mutations triggered a reduction of amyloid-beta peptides A beta 40 and A beta 42 secretion from transiently transfected HEK293T cells. Only the mutations at position 28 of A beta in the APP sequence resulted in a concomitant significant increase in the production of shorter A beta peptides. Mass spectrometry (MS) confirmed the predominance of A beta x-33 and A beta x-34 with the APP(K28A) mutant. The enzymatic activity of alpha-, beta-, and gamma-secretases remained unchanged in cells expressing all mutants. Similarly, subcellular localization of the mutants in early endosomes did not differ from the APP(WT) protein. A transient increase of plasma membrane cholesterol enhanced the production of A beta 40 and A beta 42 by APP(WT), an effect absent in APP(K28A) mutant. Finally, WT but not CBS mutant A beta derived peptides bound to cholesterol-rich exosomes. Collectively, the present data revealed a major role of juxtamembrane amino acids of the APP CBS in modulating the production of toxic A beta species. More generally, they underpin the role of cholesterol in the pathophysiology of AD.
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| 47. |
- Hansson, Karl, 1985, et al.
(författare)
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Expanding the cerebrospinal fluid endopeptidome
- 2017
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Ingår i: Proteomics. - : Wiley. - 1615-9853. ; 17:5
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Tidskriftsartikel (refereegranskat)abstract
- Biomarkers of neurodegenerative disorders are needed to assist in diagnosis, to monitor disease progression and therapeutic interventions, and to provide insight into disease mechanisms. One route to identify such biomarkers is by proteomic and peptidomic analysis of cerebrospinal fluid (CSF). In the current study, we performed an in-depth analysis of the human CSF endopeptidome to establish an inventory thatmay serve as a basis for future targeted biomarker studies. High-pH RP HPLC was employed for off-line sample prefractionation followed by low-pH nano-LC-MS analysis. Different software programs and scoring algorithms for peptide identification were employed and compared. A total of 18 031 endogenous peptides were identified at a FDR of 1%, increasing the number of known endogenous CSF peptides 10fold compared to previous studies. The peptides were derived from 2 053 proteins of which more than 60 have been linked to neurodegeneration. Notably, among the findings were six peptides derived from microtubule-associated protein tau, three of which span the diagnostically interesting threonine-181 (Tau-F isoform). Also, 213 peptides from amyloid precursor protein were identified, 58 of which were partially or completely within the sequence of amyloid beta 1-40/42, as well as 109 peptides from apolipoprotein E, spanning sequences that discriminate between the E2/E3/E4 isoforms of the protein.
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| 48. |
- Haußmann, Ute, et al.
(författare)
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Analysis of Amino-Terminal Variants of Amyloid-β Peptides by Capillary Isoelectric Focusing Immunoassay.
- 2013
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Ingår i: Analytical chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 85:17, s. 8142-9
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Tidskriftsartikel (refereegranskat)abstract
- Here we present a novel assay for the separation and detection of amino-terminal amyloid-β (Aβ) peptide variants by capillary isoelectric focusing (CIEF) immunoassay. Specific amino-terminally truncated Aβ peptides appear to be generated by β-secretase (BACE1)-independent mechanisms and have previously been observed in cerebrospinal fluid (CSF) after BACE1 inhibitor treatment in an animal model. CIEF immunoassay sensitivity is sufficient to detect total Aβ in CSF without preconcentration. To analyze low-abundance amino-terminally truncated Aβ peptides from cell culture supernatants, we developed a CIEF-compatible immunoprecipitation protocol, allowing for selective elution of Aβ peptides with very low background. CIEF immunoassay and immunoprecipitation mass spectrometry analysis identified peptides starting at residue Arg(5) as the main amino-terminal Aβ variants produced in the presence of tripartite BACE1 inhibitor in our cell culture model. The CIEF immunoassay allows for robust relative quantification of Aβ peptide patterns in biological samples. To assess the future possibility of absolute quantification, we have prepared the Aβ peptides Aβx-10, Aβx-16, and Aβ5-38(D23S) by using solid phase peptide synthesis as internal standards for the CIEF immunoassay.
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| 49. |
- Hellwig, K., et al.
(författare)
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Neurogranin and YKL-40: independent markers of synaptic degeneration and neuroinflammation in Alzheimer's disease
- 2015
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Ingår i: Alzheimers Research & Therapy. - : Springer Science and Business Media LLC. - 1758-9193. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Neuroinflammation and synaptic degeneration are major neuropathological hallmarks in Alzheimer's disease (AD). Neurogranin and YKL-40 in cerebrospinal fluid (CSF) are newly discovered markers indicating synaptic damage and microglial activation, respectively. Methods: CSF samples from 95 individuals including 39 patients with AD dementia (AD-D), 13 with mild cognitive impairment (MCI) due to AD (MCI-AD), 29 with MCI not due to AD (MCI-o) and 14 patients with non-AD dementias (non-AD-D) were analyzed for neurogranin and YKL-40. Results: Patients with dementia or MCI due to AD showed elevated levels of CSF neurogranin (p < 0.001 for AD-D and p < 0.05 for MCI-AD) and YKL-40 (p < 0.05 for AD-D and p = 0.15 for MCI-AD) compared to mildly cognitively impaired subjects not diagnosed with AD. CSF levels of neurogranin and YKL-40 did not differ between MCI not due to AD and non-AD dementias. In AD subjects no correlation between YKL-40 and neurogranin was found. The CSF neurogranin levels correlated moderately with tau and p-tau but not with A beta 42 or the MMSE in AD samples. No relevant associations between YKL-40 and MMSE or the core AD biomarkers, A beta 42, t-tau and p-tau were found in AD subjects. Conclusions: Neurogranin and YKL-40 are promising AD biomarkers, independent of and complementary to the established core AD biomarkers, reflecting additional pathological changes in the course of AD.
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| 50. |
- Höglund, Kina, 1976, et al.
(författare)
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Alzheimer's disease - Recent biomarker developments in relation to updated diagnostic criteria.
- 2015
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Ingår i: Clinica chimica acta; international journal of clinical chemistry. - : Elsevier BV. - 1873-3492. ; 449, s. 3-8
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Tidskriftsartikel (refereegranskat)abstract
- Alzheimer's disease (AD) is the most common cause of dementia and is characterized by neuroaxonal and synaptic degeneration accompanied by intraneuronal neurofibrillary tangles and accumulation of extracellular plaques in specific brain regions. These features are reflected in the AD cerebrospinal fluid (CSF) by increased concentrations of total tau (t-tau) and phosphorylated tau (p-tau), together with decreased concentrations of β-amyloid (Aβ42), respectively. In combination, Aβ42, p-tau and t-tau are 85-95% sensitive and specific for AD in both prodromal and dementia stages of the disease and they are now included in the diagnostic research criteria for AD. However, to fully implement these biomarkers into clinical practice, harmonization of data is needed. This work is ongoing through the standardization of analytical procedures between clinical laboratories and the production of reference materials for CSF Aβ42, p-tau and t-tau. To monitor other aspects of AD neuropathology, e.g., synaptic dysfunction and/or to develop markers of progression, identifying novel candidate biomarkers is of great importance. Based on knowledge from the established biomarkers, exemplified by Aβ and its many variants, and emerging data on neurogranin fragments as biomarker candidate(s), a thorough protein characterization in order to fully understand the diagnostic value of a protein is a suggested approach for successful biomarker discovery.
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