| 21. |
- Roselli, Sandra, et al.
(författare)
-
APP-BACE1 Interaction and Intracellular Localization Regulate A beta Production in iPSC-Derived Cortical Neurons
- 2023
-
Ingår i: Cellular and Molecular Neurobiology. - 0272-4340. ; 43
-
Tidskriftsartikel (refereegranskat)abstract
- Alzheimer's disease (AD) is characterized pathologically by amyloid beta (A beta)-containing plaques. Generation of A beta from amyloid precursor protein (APP) by two enzymes, beta- and gamma-secretase, has therefore been in the AD research spotlight for decades. Despite this, how the physical interaction of APP with the secretases influences APP processing is not fully understood. Herein, we compared two genetically identical human iPSC-derived neuronal cell types: low A beta-secreting neuroprogenitor cells (NPCs) and high A beta-secreting mature neurons, as models of low versus high A beta production. We investigated levels of substrate, enzymes and products of APP amyloidogenic processing and correlated them with the proximity of APP to beta- and gamma-secretase in endo-lysosomal organelles. In mature neurons, increased colocalization of full-length APP with the beta-secretase BACE1 correlated with increased beta-cleavage product sAPP beta. Increased flAPP/BACE1 colocalization was mainly found in early endosomes. In the same way, increased colocalization of APP-derived C-terminal fragment (CTF) with presenilin-1 (PSEN1), the catalytic subunit of gamma-secretase, was seen in neurons as compared to NPCs. Furthermore, most of the interaction of APP with BACE1 in low A beta-secreting NPCs seemed to derive from CTF, the remaining APP part after BACE1 cleavage, indicating a possible novel product-enzyme inhibition. In conclusion, our results suggest that interaction of APP and APP cleavage products with their secretases can regulate A beta production both positively and negatively. beta- and gamma-Secretases are difficult targets for AD treatment due to their ubiquitous nature and wide range of substrates. Therefore, targeting APP-secretase interactions could be a novel treatment strategy for AD.
|
|
| 22. |
- Satir, Tugce Munise, et al.
(författare)
-
Accelerated neuronal and synaptic maturation by BrainPhys medium increases Aβ secretion and alters Aβ peptide ratios from iPSC-derived cortical neurons.
- 2020
-
Ingår i: Scientific reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
-
Tidskriftsartikel (refereegranskat)abstract
- One of the neuropathological hallmarks of Alzheimer's disease (AD) is cerebral deposition of amyloid plaques composed of amyloid β (Aβ) peptides and the cerebrospinal fluid concentrations of those peptides are used as a biomarker for AD. Mature induced pluripotent stem cell (iPSC)-derived cortical neurons secrete Aβ peptides in ratios comparable to those secreted to cerebrospinal fluid in human, however the protocol to achieve mature neurons is time consuming. In this study, we investigated if differentiation of neuroprogenitor cells (NPCs) in BrainPhys medium, previously reported to enhance synaptic function of neurons in culture, would accelerate neuronal maturation and, thus increase Aβ secretion as compared to the conventional neural maintenance medium. We found that NPCs cultured in BrainPhys displayed increased expression of markers for cortical deep-layer neurons, increased synaptic maturation and number of astroglial cells. This accelerated neuronal maturation was accompanied by increased APP processing, resulting in increased secretion of Aβ peptides and an increased Aβ38 to Aβ40 and Aβ42 ratio. However, during long-term culturing in BrainPhys, non-neuronal cells appeared and eventually took over the cultures. Taken together, BrainPhys culturing accelerated neuronal maturation and increased Aβ secretion from iPSC-derived cortical neurons, but changed the cellular composition of the cultures.
|
|
| 23. |
|
|
| 24. |
- Satir, Tugce Munise, et al.
(författare)
-
Partial reduction of amyloid β production by β-secretase inhibitors does not decrease synaptic transmission
- 2020
-
Ingår i: Alzheimer's Research and Therapy. - : Springer Science and Business Media LLC. - 1758-9193. ; 12
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Alzheimer's disease (AD) is the most common form of age-related neurodegenerative diseases. Cerebral deposition of Aβ peptides, especially Aβ42, is considered the major neuropathological hallmark of AD and the putative cause of AD-related neurotoxicity. Aβ peptides are produced by sequential proteolytic processing of APP, with β-secretase (BACE) being the initiating enzyme. Therefore, BACE has been considered an attractive therapeutic target in AD research and several BACE inhibitors have been tested in clinical trials, but so far, all have had negative outcomes or even led to worsening of cognitive function. AD can be triggered by Aβ years before the first symptoms appear and one reason for the failures could be that the clinical trials were initiated too late in the disease process. Another possible explanation could be that BACE inhibition alters physiological APP processing in a manner that impairs synaptic function, causing cognitive deterioration. Methods: The aim of this study was to investigate if partial BACE inhibition, mimicking the putative protective effect of the Icelandic mutation in the APP gene, could reduce Aβ generation without affecting synaptic transmission. To investigate this, we used an optical electrophysiology platform, in which effects of compounds on synaptic transmission in cultured neurons can be monitored. We employed this method on primary cortical rat neuronal cultures treated with three different BACE inhibitors (BACE inhibitor IV, LY2886721, and lanabecestat) and monitored Aβ secretion into the cell media. Results: We found that all three BACE inhibitors tested decreased synaptic transmission at concentrations leading to significantly reduced Aβ secretion. However, low-dose BACE inhibition, resulting in less than a 50% decrease in Aβ secretion, did not affect synaptic transmission for any of the inhibitors tested. Conclusion: Our results indicate that Aβ production can be reduced by up to 50%, a level of reduction of relevance to the protective effect of the Icelandic mutation, without causing synaptic dysfunction. We therefore suggest that future clinical trials aimed at prevention of Aβ build-up in the brain should aim for a moderate CNS exposure of BACE inhibitors to avoid side effects on synaptic function. © 2020 The Author(s).
|
|
| 25. |
- Sofou, Kalliopi, et al.
(författare)
-
Bi-allelic VPS16 variants limit HOPS/CORVET levels and cause a mucopolysaccharidosis-like disease.
- 2021
-
Ingår i: EMBO molecular medicine. - : EMBO. - 1757-4684 .- 1757-4676. ; 13
-
Tidskriftsartikel (refereegranskat)abstract
- Lysosomal storage diseases, including mucopolysaccharidoses, result from genetic defects that impair lysosomal catabolism. Here, we describe two patients from two independent families presenting with progressive psychomotor regression, delayed myelination, brain atrophy, neutropenia, skeletal abnormalities, and mucopolysaccharidosis-like dysmorphic features. Both patients were homozygous for the same intronic variant in VPS16, a gene encoding a subunit of the HOPS and CORVET complexes. The variant impaired normal mRNA splicing and led to an ~85% reduction in VPS16 protein levels in patient-derived fibroblasts. Levels of other HOPS/CORVET subunits, including VPS33A, were similarly reduced, but restored upon re-expression of VPS16. Patient-derived fibroblasts showed defects in the uptake and endosomal trafficking of transferrin as well as accumulation of autophagosomes and lysosomal compartments. Re-expression of VPS16 rescued the cellular phenotypes. Zebrafish with disrupted vps16 expression showed impaired development, reduced myelination, and a similar accumulation of lysosomes and autophagosomes in the brain, particularly in glia cells. This disorder resembles previously reported patients with mutations in VPS33A, thus expanding the family of mucopolysaccharidosis-like diseases that result from mutations in HOPS/CORVET subunits.
|
|
