Cell models for prion infection, replication, and strain behavior have long been available to prion researchers. These include stable lines producing transmissible prion aggregates and inducible cell lines that are dependent on the addition of exogenous prions. More recently, cell models for prion-like behavior of tau and synuclein aggregates have become available to facilitate studies of seeding, transmission, structural polymorphisms, and the search for drugs to target these mechanisms. All of this has contributed to a growing understanding that the prion-like properties of strain polymorphisms, seeding, transmission, and templated replication are fundamental properties of all amyloids.
Indeed, even for Aβ amyloid there is evidence from transgenic animals that demonstrates prion-like properties of strain polymorphisms, seeding, and transmission. It isn’t clear why the development of cell models of Aβ prion-like properties has lagged behind, but perhaps bias against the idea of significance of intracellular Aβ may be at least partly responsible. Most of the “action” for Aβ seems to be outside of the cell. Intraneuronal amyloid deposits have been known since the first Aβ and APP antibodies became available, but fell out of favor after the discovery of soluble secreted Aβ. Indeed, intraneuronal amyloid is sometimes viewed as normal because it contains epitopes from APP outside the traditional soluble Aβ regions. However, intraneuronal Aβ is not just APP. It has prion-like properties as well. It is insoluble and protease-resistant. It is aggregated in an amyloid-like structure because it stains with traditional amyloid-binding dyes and reacts with antibodies specific for amyloid aggregates that do not recognize Aβ monomer or soluble APP.
Now in this paper, Gunnar Gouras and co-workers describe a cellular model of intracellular Aβ amyloid seeding and nucleation. They report the interesting and exciting findings that treating N2a cells expressing human FAD mutant APP with a particulate lysate from transgenic mice that have accumulated amyloid deposits leads to the seeding of amyloid Aβ inclusions of cells that demonstrate prion-like properties. Cells expressing these inclusions were cloned and shown to accumulate amyloid that reacts with 82E1, a monoclonal antibody specific for the amino terminus of Aβ and OC serum that is specific for fibrillar oligomers or fibril aggregates, but does not react with APP or Aβ monomer.
The clones expressing these amyloid inclusions remain phenotypically stable for at least 10 passages and can be stored frozen at -80°C. Moreover, particulate extracts of these stable cell lines with Aβ amyloid inclusions, but not extracts from wild-type brain extract-treated cells, seeded further formation of intracellular amyloid inclusions in naïve N2A cells, demonstrating the fundamental prion-like property of transmissibility. The authors further demonstrate that the intracellular amyloid inclusions are resistant to proteinase K digestion, contain β-sheet secondary structure, and contain high molecular weight oligomeric Aβ in the range of 250–670 kDa.
If these cells are like other cellular models of the prion-like properties of amyloids, they will facilitate studies on the strain polymorphisms of Aβ amyloid structures and their nucleation and transmission as well as studies on their pathological significance. They may also be useful in high-throughput screens for drugs that inhibit nucleation, replication, or transmission of Aβ prion-like seeds. Although the results of cell culture studies need to be verified in animal models, it helps to know what to look for first and these clues often come from cell culture models.
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University of California, Irvine
Cell models for prion infection, replication, and strain behavior have long been available to prion researchers. These include stable lines producing transmissible prion aggregates and inducible cell lines that are dependent on the addition of exogenous prions. More recently, cell models for prion-like behavior of tau and synuclein aggregates have become available to facilitate studies of seeding, transmission, structural polymorphisms, and the search for drugs to target these mechanisms. All of this has contributed to a growing understanding that the prion-like properties of strain polymorphisms, seeding, transmission, and templated replication are fundamental properties of all amyloids.
Indeed, even for Aβ amyloid there is evidence from transgenic animals that demonstrates prion-like properties of strain polymorphisms, seeding, and transmission. It isn’t clear why the development of cell models of Aβ prion-like properties has lagged behind, but perhaps bias against the idea of significance of intracellular Aβ may be at least partly responsible. Most of the “action” for Aβ seems to be outside of the cell. Intraneuronal amyloid deposits have been known since the first Aβ and APP antibodies became available, but fell out of favor after the discovery of soluble secreted Aβ. Indeed, intraneuronal amyloid is sometimes viewed as normal because it contains epitopes from APP outside the traditional soluble Aβ regions. However, intraneuronal Aβ is not just APP. It has prion-like properties as well. It is insoluble and protease-resistant. It is aggregated in an amyloid-like structure because it stains with traditional amyloid-binding dyes and reacts with antibodies specific for amyloid aggregates that do not recognize Aβ monomer or soluble APP.
Now in this paper, Gunnar Gouras and co-workers describe a cellular model of intracellular Aβ amyloid seeding and nucleation. They report the interesting and exciting findings that treating N2a cells expressing human FAD mutant APP with a particulate lysate from transgenic mice that have accumulated amyloid deposits leads to the seeding of amyloid Aβ inclusions of cells that demonstrate prion-like properties. Cells expressing these inclusions were cloned and shown to accumulate amyloid that reacts with 82E1, a monoclonal antibody specific for the amino terminus of Aβ and OC serum that is specific for fibrillar oligomers or fibril aggregates, but does not react with APP or Aβ monomer.
The clones expressing these amyloid inclusions remain phenotypically stable for at least 10 passages and can be stored frozen at -80°C. Moreover, particulate extracts of these stable cell lines with Aβ amyloid inclusions, but not extracts from wild-type brain extract-treated cells, seeded further formation of intracellular amyloid inclusions in naïve N2A cells, demonstrating the fundamental prion-like property of transmissibility. The authors further demonstrate that the intracellular amyloid inclusions are resistant to proteinase K digestion, contain β-sheet secondary structure, and contain high molecular weight oligomeric Aβ in the range of 250–670 kDa.
If these cells are like other cellular models of the prion-like properties of amyloids, they will facilitate studies on the strain polymorphisms of Aβ amyloid structures and their nucleation and transmission as well as studies on their pathological significance. They may also be useful in high-throughput screens for drugs that inhibit nucleation, replication, or transmission of Aβ prion-like seeds. Although the results of cell culture studies need to be verified in animal models, it helps to know what to look for first and these clues often come from cell culture models.
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