| 1. |
- Borgegard, Tomas, et al.
(författare)
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Alzheimers Disease: Presenilin 2-Sparing gamma-Secretase Inhibition Is a Tolerable A beta Peptide-Lowering Strategy
- 2012
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Ingår i: Journal of Neuroscience. - : Society for Neuroscience. - 0270-6474 .- 1529-2401. ; 32:48, s. 17297-17305
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Tidskriftsartikel (refereegranskat)abstract
- gamma-Secretase inhibition represents a major therapeutic strategy for lowering amyloid beta (A beta) peptide production in Alzheimers disease (AD). Progress toward clinical use of gamma-secretase inhibitors has, however, been hampered due to mechanism-based adverse events, primarily related to impairment of Notch signaling. The gamma-secretase inhibitor MRK-560 represents an exception as it is largely tolerable in vivo despite displaying only a small selectivity between A beta production and Notch signaling in vitro. In exploring the molecular basis for the observed tolerability, we show that MRK-560 displays a strong preference for the presenilin 1(PS1) over PS2 subclass of gamma-secretases and is tolerable in wild-type mice but causes dose-dependent Notch-related side effect in PS2-deficient mice at drug exposure levels resulting in a substantial decrease in brain A beta levels. This demonstrates that PS2 plays an important role in mediating essential Notch signaling in several peripheral organs during pharmacological inhibition of PS1 and provide preclinical in vivo proof of concept for PS2-sparing inhibition as a novel, tolerable and efficacious gamma-secretase targeting strategy for AD.
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| 2. |
- Borgegård, Tomas, et al.
(författare)
-
Alzheimer's Disease : Presenilin 2-Sparing γ-Secretase Inhibition Is a Tolerable Aβ Peptide-Lowering Strategy
- 2012
-
Ingår i: Journal of Neuroscience. - 0270-6474 .- 1529-2401. ; 32:48, s. 17297-17305
-
Tidskriftsartikel (refereegranskat)abstract
- γ-Secretase inhibition represents a major therapeutic strategy for lowering amyloid β (Aβ) peptide production in Alzheimer's disease (AD). Progress toward clinical use of γ-secretase inhibitors has, however, been hampered due to mechanism-based adverse events, primarily related to impairment of Notch signaling. The γ-secretase inhibitor MRK-560 represents an exception as it is largely tolerable in vivo despite displaying only a small selectivity between Aβ production and Notch signaling in vitro. In exploring the molecular basis for the observed tolerability, we show that MRK-560 displays a strong preference for the presenilin 1 (PS1) over PS2 subclass of γ-secretases and is tolerable in wild-type mice but causes dose-dependent Notch-related side effect in PS2-deficient mice at drug exposure levels resulting in a substantial decrease in brain Aβ levels. This demonstrates that PS2 plays an important role in mediating essential Notch signaling in several peripheral organs during pharmacological inhibition of PS1 and provide preclinical in vivo proof of concept for PS2-sparing inhibition as a novel, tolerable and efficacious γ-secretase targeting strategy for AD.
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| 3. |
- Wanngren, Johanna
(författare)
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Molecular studies of the γ-secretase complex : focus on genetic and pharmacological modulation
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- γ-Secretase is a multi-subunit protease complex, composed of presenilin (PS1 or PS2), Nicastrin, Pen-2 and Aph-1, which generates the Alzheimer disease (AD) related 30-43 amino acid long amyloid β-peptide (Aβ). The complex is also crucial for important cell signaling, such as the Notch receptor pathway. More than 200 different Familial AD (FAD) causing mutations have been identified. They are all restricted to either PS1, PS2 or the amyloid β-precursor protein (APP), from which Aβ is generated, therefore proving how central γ-secretase mediated Aβ production is in AD pathogenesis. A common feature of FAD mutants is an increased Aβ42/Aβ40 ratio production. This results in a more amyloidogenic Aβ product and accelerated oligomerization and plaque formation. A number of γ-secretase inhibitors have been in clinical trials but so far there have been no major progress, due to mechanism-based side effects that is probably caused by impaired Notch signaling. It is therefore very important to develop novel therapeutic strategies targeting Aβ production without interfering with other crucial γ-secretase signaling pathwats. The aim of my thesis was to i) get a better understanding of the molecular basis behind the heterogeneous activity of γ-secretase resulting in different Aβ peptides, ii) to identify novel ways to target γ-secretase mediated Aβ production in a Notch sparing manner, iii) to explore the impact of a novel class of drugs called γ-secretase modulators (GSMs) on different γ-secretase processes. In Paper I, we specifically investigated whether the membrane integration and/or the active site of PS would be affected by different PS1 FAD mutations, which cause an increased Aβ42/Aβ40 production ratio. We found that while some FAD mutations located in hydrophobic domains around the catalytic site (TMD6, H7 and TMD7) changed the membrane integration of PS1, all FAD mutations studied affected the structure of the catalytic site of γ-secretase. In Paper II the large hydrophilic loop of PS1 was examined. Interestingly, by using a deletion mutant strategy, we found that, similar to many FAD mutants, Aβ38, Aβ39 and Aβ40 were dramatically decreased in the absence of the loop, while Aβ42 was affected to a lesser extent, resulting in a net increase in the Aβ42/Aβ40 ratio. Importantly, neither AICD nor NICD formation was impaired, suggesting that the integrity of the loop region is important for proper γ-site cleavage but not for the overall cleavage activity at the ε-site. To further study the mechanism of γ-secretase processing, we reported in Paper III the first study describing single residues in a γ-secretase component besides presenilin, such as Nicastrin, that affects the processing of γ-secretase substrates differently. In the final study, Paper IV, we studied the pharmacology of different GSMs and found that it is possible to generate in vivo potent second-generation γ-secretase-targeting modulatory compounds that are pre-selective for Aβ over Nβ production without affecting NICD formation. These findings may have major implications for the development of GSMs for AD and will be further discussed in the thesis.
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| 4. |
- Wanngren, Johanna, et al.
(författare)
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Second generation γ-secretase modulators exhibit different modulation of Notch β and Aβ production.
- 2012
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Ingår i: The Journal of biological chemistry. - 1083-351X. ; 287:39, s. 32640-50
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Tidskriftsartikel (refereegranskat)abstract
- The γ-secretase complex is an appealing drug target when the therapeutic strategy is to alter amyloid-β peptide (Aβ) aggregation in Alzheimer disease. γ-Secretase is directly involved in Aβ formation and determines the pathogenic potential of Aβ by generating the aggregation-prone Aβ42 peptide. Because γ-secretase mediates cleavage of many substrates involved in cell signaling, such as the Notch receptor, it is crucial to sustain these pathways while altering the Aβ secretion. A way of avoiding interference with the physiological function of γ-secretase is to use γ-secretase modulators (GSMs) instead of inhibitors of the enzyme. GSMs modify the Aβ formation from producing the amyloid-prone Aβ42 variant to shorter and less amyloidogenic Aβ species. The modes of action of GSMs are not fully understood, and even though the pharmacology of GSMs has been thoroughly studied regarding Aβ generation, knowledge is lacking about their effects on other substrates, such as Notch. Here, using immunoprecipitation followed by MALDI-TOF MS analysis, we found that two novel, second generation GSMs modulate both Notch β and Aβ production. Moreover, by correlating S3-specific Val-1744 cleavage of Notch intracellular domain (Notch intracellular domain) to total Notch intracellular domain levels using immunocytochemistry, we also demonstrated that Notch intracellular domain is not modulated by the compounds. Interestingly, two well characterized, nonsteroidal anti-inflammatory drugs (nonsteroidal anti-inflammatory drug), R-flurbiprofen and sulindac sulfide, affect only Aβ and not Notch β formation, indicating that second generation GSMs and nonsteroidal anti-inflammatory drug-based GSMs have different modes of action regarding Notch processing.
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