TREM2 modulates differential deposition of post-translationally modified Aβ variants in the brain parenchyma and the vasculature
TREM2 modulates differential deposition of post-translationally modified Aβ variants in the brain parenchyma and the vasculature
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DissertationPrüfungsdatum
02.06.2022Datum der Veröffentlichung
01.08.2022Erstgutachter
Walter, JochenZweitgutachter
Lang, ThorstenMetadaten
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Inhalt
Alzheimer’s disease (AD) is characterized by the combined presence of extracellular amyloid-beta (Aβ) plaques and intracellular neurofibrillary tangles (NFTs) with abnormally phosphorylated tau (t) protein in the brain. Genome-wide association studies (GWAS) and whole exome sequencing (WES) of sporadic AD cases have recently identified DNA polymorphisms that increase the risk for AD, including the Triggering Receptor Expressed on Myeloid cells 2 (TREM2). ADAM proteases shed this surface TREM2, resulting in the generation of soluble ectodomain fraction of TREM2 (sTREM2). To investigate the potential role of sTREM2, to compare sTREM2 with disease-associated mutations (in particular R47H and T66M), and to characterize ligand interactions; stable cell lines were generated using the Flp-In system. The cellular trafficking and processing of AD-associated variants (such as R47H) are similar to wild-type TREM2, but frontotemporal dementia (FTD) or Nasu-Hakola disease (NHD) mutations (such as T66M) impair folding, trafficking to the plasma membrane and accumulates TREM2 in the endoplasmic reticulum (ER).
The heterogeneity of proteolytic cleavages and post-translational modifications by various enzymes can lead to modified Aβ peptides with differences in the stability, toxicity, and aggregation kinetics. In particular, phosphorylation at serine 8 (pSer8-Aβ) promotes fibrillization, while phosphorylation at serine 26 (pSer26-Aβ) stabilizes oligomeric assemblies, and rather decreases the fibrillization of Aβ. While pSer8-Aβ was abundant in plaque core, the reactivity of pSer26-Aβ is limited in extracellular plaques and both of these species were detected in neurons and vessels resembling cerebral amyloid angiopathy (CAA). In parallel, a novel AβS26D-Tg transgenic mouse model was generated, which demonstrated the presence of Aβ oligomers within neurons throughout life and exhibited cognitive impairment without evidence of extracellular plaques as observed in old age mice.
Further, to assess whether phosphorylation of Aβ affects the interaction with TREM2, interaction studies were performed by Biolayer interferometry, co-immunoprecipitation, and dot blot overlay assays. Phosphorylation of Aβ increases its binding to TREM2 and this increased interaction plays an important role in the uptake of Aβ in distinct aggregation states by the primary microglia. Also, TREM2 deletion or functional mutation of TREM2 in the microglia leads to the accumulation of these toxic Aβ species in transgenic mice. In addition, human brains with rare TREM2 AD risk variants showed an altered deposition of modified Aβ species in the different brain lesions as compared to AD cases with the common variant of TREM2.
Together, this work demonstrates that the differences in the aggregation of phosphorylated Aβ species led to differential deposition characteristics in the form of plaques, intraneuronal and CAA. Also, this study provides a new perspective on TREM2 function and highlights the importance of further investigating the potential of targeting phosphorylated Aβ species for AD therapy and prevention.
The heterogeneity of proteolytic cleavages and post-translational modifications by various enzymes can lead to modified Aβ peptides with differences in the stability, toxicity, and aggregation kinetics. In particular, phosphorylation at serine 8 (pSer8-Aβ) promotes fibrillization, while phosphorylation at serine 26 (pSer26-Aβ) stabilizes oligomeric assemblies, and rather decreases the fibrillization of Aβ. While pSer8-Aβ was abundant in plaque core, the reactivity of pSer26-Aβ is limited in extracellular plaques and both of these species were detected in neurons and vessels resembling cerebral amyloid angiopathy (CAA). In parallel, a novel AβS26D-Tg transgenic mouse model was generated, which demonstrated the presence of Aβ oligomers within neurons throughout life and exhibited cognitive impairment without evidence of extracellular plaques as observed in old age mice.
Further, to assess whether phosphorylation of Aβ affects the interaction with TREM2, interaction studies were performed by Biolayer interferometry, co-immunoprecipitation, and dot blot overlay assays. Phosphorylation of Aβ increases its binding to TREM2 and this increased interaction plays an important role in the uptake of Aβ in distinct aggregation states by the primary microglia. Also, TREM2 deletion or functional mutation of TREM2 in the microglia leads to the accumulation of these toxic Aβ species in transgenic mice. In addition, human brains with rare TREM2 AD risk variants showed an altered deposition of modified Aβ species in the different brain lesions as compared to AD cases with the common variant of TREM2.
Together, this work demonstrates that the differences in the aggregation of phosphorylated Aβ species led to differential deposition characteristics in the form of plaques, intraneuronal and CAA. Also, this study provides a new perspective on TREM2 function and highlights the importance of further investigating the potential of targeting phosphorylated Aβ species for AD therapy and prevention.
Schlagwörter
Alzheimer's disease, Brain, Microglia, Neurons, TREM2, Amyloid-beta, Transgenic mice
Klassifikation (DDC)
570 Biowissenschaften, Biologie 610 Medizin, GesundheitZugehörige Publikation(en)
https://doi.org/10.1002/glia.24077https://doi.org/10.1186/s40478-021-01263-x
Joshi, Pranav Chintamani: TREM2 modulates differential deposition of post-translationally modified Aβ variants in the brain parenchyma and the vasculature. - Bonn, 2022. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5-66996
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5-66996
@phdthesis{handle:20.500.11811/10127,
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5-66996,
author = {{Pranav Chintamani Joshi}},
title = {TREM2 modulates differential deposition of post-translationally modified Aβ variants in the brain parenchyma and the vasculature},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2022,
month = aug,
note = {Alzheimer’s disease (AD) is characterized by the combined presence of extracellular amyloid-beta (Aβ) plaques and intracellular neurofibrillary tangles (NFTs) with abnormally phosphorylated tau (t) protein in the brain. Genome-wide association studies (GWAS) and whole exome sequencing (WES) of sporadic AD cases have recently identified DNA polymorphisms that increase the risk for AD, including the Triggering Receptor Expressed on Myeloid cells 2 (TREM2). ADAM proteases shed this surface TREM2, resulting in the generation of soluble ectodomain fraction of TREM2 (sTREM2). To investigate the potential role of sTREM2, to compare sTREM2 with disease-associated mutations (in particular R47H and T66M), and to characterize ligand interactions; stable cell lines were generated using the Flp-In system. The cellular trafficking and processing of AD-associated variants (such as R47H) are similar to wild-type TREM2, but frontotemporal dementia (FTD) or Nasu-Hakola disease (NHD) mutations (such as T66M) impair folding, trafficking to the plasma membrane and accumulates TREM2 in the endoplasmic reticulum (ER).
The heterogeneity of proteolytic cleavages and post-translational modifications by various enzymes can lead to modified Aβ peptides with differences in the stability, toxicity, and aggregation kinetics. In particular, phosphorylation at serine 8 (pSer8-Aβ) promotes fibrillization, while phosphorylation at serine 26 (pSer26-Aβ) stabilizes oligomeric assemblies, and rather decreases the fibrillization of Aβ. While pSer8-Aβ was abundant in plaque core, the reactivity of pSer26-Aβ is limited in extracellular plaques and both of these species were detected in neurons and vessels resembling cerebral amyloid angiopathy (CAA). In parallel, a novel AβS26D-Tg transgenic mouse model was generated, which demonstrated the presence of Aβ oligomers within neurons throughout life and exhibited cognitive impairment without evidence of extracellular plaques as observed in old age mice.
Further, to assess whether phosphorylation of Aβ affects the interaction with TREM2, interaction studies were performed by Biolayer interferometry, co-immunoprecipitation, and dot blot overlay assays. Phosphorylation of Aβ increases its binding to TREM2 and this increased interaction plays an important role in the uptake of Aβ in distinct aggregation states by the primary microglia. Also, TREM2 deletion or functional mutation of TREM2 in the microglia leads to the accumulation of these toxic Aβ species in transgenic mice. In addition, human brains with rare TREM2 AD risk variants showed an altered deposition of modified Aβ species in the different brain lesions as compared to AD cases with the common variant of TREM2.
Together, this work demonstrates that the differences in the aggregation of phosphorylated Aβ species led to differential deposition characteristics in the form of plaques, intraneuronal and CAA. Also, this study provides a new perspective on TREM2 function and highlights the importance of further investigating the potential of targeting phosphorylated Aβ species for AD therapy and prevention.},
url = {https://hdl.handle.net/20.500.11811/10127}
}
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5-66996,
author = {{Pranav Chintamani Joshi}},
title = {TREM2 modulates differential deposition of post-translationally modified Aβ variants in the brain parenchyma and the vasculature},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2022,
month = aug,
note = {Alzheimer’s disease (AD) is characterized by the combined presence of extracellular amyloid-beta (Aβ) plaques and intracellular neurofibrillary tangles (NFTs) with abnormally phosphorylated tau (t) protein in the brain. Genome-wide association studies (GWAS) and whole exome sequencing (WES) of sporadic AD cases have recently identified DNA polymorphisms that increase the risk for AD, including the Triggering Receptor Expressed on Myeloid cells 2 (TREM2). ADAM proteases shed this surface TREM2, resulting in the generation of soluble ectodomain fraction of TREM2 (sTREM2). To investigate the potential role of sTREM2, to compare sTREM2 with disease-associated mutations (in particular R47H and T66M), and to characterize ligand interactions; stable cell lines were generated using the Flp-In system. The cellular trafficking and processing of AD-associated variants (such as R47H) are similar to wild-type TREM2, but frontotemporal dementia (FTD) or Nasu-Hakola disease (NHD) mutations (such as T66M) impair folding, trafficking to the plasma membrane and accumulates TREM2 in the endoplasmic reticulum (ER).
The heterogeneity of proteolytic cleavages and post-translational modifications by various enzymes can lead to modified Aβ peptides with differences in the stability, toxicity, and aggregation kinetics. In particular, phosphorylation at serine 8 (pSer8-Aβ) promotes fibrillization, while phosphorylation at serine 26 (pSer26-Aβ) stabilizes oligomeric assemblies, and rather decreases the fibrillization of Aβ. While pSer8-Aβ was abundant in plaque core, the reactivity of pSer26-Aβ is limited in extracellular plaques and both of these species were detected in neurons and vessels resembling cerebral amyloid angiopathy (CAA). In parallel, a novel AβS26D-Tg transgenic mouse model was generated, which demonstrated the presence of Aβ oligomers within neurons throughout life and exhibited cognitive impairment without evidence of extracellular plaques as observed in old age mice.
Further, to assess whether phosphorylation of Aβ affects the interaction with TREM2, interaction studies were performed by Biolayer interferometry, co-immunoprecipitation, and dot blot overlay assays. Phosphorylation of Aβ increases its binding to TREM2 and this increased interaction plays an important role in the uptake of Aβ in distinct aggregation states by the primary microglia. Also, TREM2 deletion or functional mutation of TREM2 in the microglia leads to the accumulation of these toxic Aβ species in transgenic mice. In addition, human brains with rare TREM2 AD risk variants showed an altered deposition of modified Aβ species in the different brain lesions as compared to AD cases with the common variant of TREM2.
Together, this work demonstrates that the differences in the aggregation of phosphorylated Aβ species led to differential deposition characteristics in the form of plaques, intraneuronal and CAA. Also, this study provides a new perspective on TREM2 function and highlights the importance of further investigating the potential of targeting phosphorylated Aβ species for AD therapy and prevention.},
url = {https://hdl.handle.net/20.500.11811/10127}
}
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