Limits...
Fibril specific, conformation dependent antibodies recognize a generic epitope common to amyloid fibrils and fibrillar oligomers that is absent in prefibrillar oligomers.

Kayed R, Head E, Sarsoza F, Saing T, Cotman CW, Necula M, Margol L, Wu J, Breydo L, Thompson JL, Rasool S, Gurlo T, Butler P, Glabe CG - Mol Neurodegener (2007)

Bottom Line: The resulting immune serum (OC) specifically recognizes fibrils, but not random coil monomer or prefibrillar oligomers, indicating fibrils display a distinct conformation dependent epitope that is absent in prefibrillar oligomers.The fibril specific antibody also recognizes 100,000 x G soluble fibrillar oligomers ranging in size from dimer to greater than 250 kDa on western blots.Diffuse amyloid deposits stain intensely with anti-fibril antibody although they are thioflavin S negative, suggesting that they are indeed fibrillar in conformation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697, USA. cglabe@uci.edu.

ABSTRACT

Background: Amyloid-related degenerative diseases are associated with the accumulation of misfolded proteins as amyloid fibrils in tissue. In Alzheimer disease (AD), amyloid accumulates in several distinct types of insoluble plaque deposits, intracellular Abeta and as soluble oligomers and the relationships between these deposits and their pathological significance remains unclear. Conformation dependent antibodies have been reported that specifically recognize distinct assembly states of amyloids, including prefibrillar oligomers and fibrils.

Results: We immunized rabbits with a morphologically homogeneous population of Abeta42 fibrils. The resulting immune serum (OC) specifically recognizes fibrils, but not random coil monomer or prefibrillar oligomers, indicating fibrils display a distinct conformation dependent epitope that is absent in prefibrillar oligomers. The fibril epitope is also displayed by fibrils of other types of amyloids, indicating that the epitope is a generic feature of the polypeptide backbone. The fibril specific antibody also recognizes 100,000 x G soluble fibrillar oligomers ranging in size from dimer to greater than 250 kDa on western blots. The fibrillar oligomers recognized by OC are immunologically distinct from prefibrillar oligomers recognized by A11, even though their sizes overlap broadly, indicating that size is not a reliable indicator of oligomer conformation. The immune response to prefibrillar oligomers and fibrils is not sequence specific and antisera of the same specificity are produced in response to immunization with islet amyloid polypeptide prefibrillar oligomer mimics and fibrils. The fibril specific antibodies stain all types of amyloid deposits in human AD brain. Diffuse amyloid deposits stain intensely with anti-fibril antibody although they are thioflavin S negative, suggesting that they are indeed fibrillar in conformation. OC also stains islet amyloid deposits in transgenic mouse models of type II diabetes, demonstrating its generic specificity for amyloid fibrils.

Conclusion: Since the fibril specific antibodies are conformation dependent, sequence-independent, and recognize epitopes that are distinct from those present in prefibrillar oligomers, they may have broad utility for detecting and characterizing the accumulation of amyloid fibrils and fibrillar type oligomers in degenerative diseases.

No MeSH data available.


Related in: MedlinePlus

Schematic representation of the distinct types of amyloid oligomers and their relationships to amyloid fibrils. Amyloid aggregation pathways begin with misfolded amyloidogenic monomer (top) and can diverge in two directions depending on which conformation it adopts. It can aggregate to form prefibrillar oligomers by adopting the conformation recognized by A11 (left pathway). These prefibrillar oligomers then align to form protofibrils (not shown) and undergo another conformation change "en bloc" to form fibrils. They are termed prefibrillar oligomers because they are transient intermediates that ultimately become fibrils. Alternatively, amyloidogenic monomer can aggregate to adopt a fibrillar conformation recognized by OC antibody (right pathway). The resulting fibrillar oligomers may represent fibril nuclei which are the minimal stable aggregate that is capable of elongating by recruiting additional monomers. Addition of monomers on to the ends of fibrillar oligomers and fibrils result in fibril growth. The distinction between fibrillar oligomers and fibrils is based on an arbitrary size difference as no conformation difference is apparent. Fibrils may be distinct from fibrillar oligomers on the basis of their content of multiple protofilaments (not shown) but this does not necessarily imply a necessary conformation difference in their integral peptide constituents.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2100048&req=5

Figure 9: Schematic representation of the distinct types of amyloid oligomers and their relationships to amyloid fibrils. Amyloid aggregation pathways begin with misfolded amyloidogenic monomer (top) and can diverge in two directions depending on which conformation it adopts. It can aggregate to form prefibrillar oligomers by adopting the conformation recognized by A11 (left pathway). These prefibrillar oligomers then align to form protofibrils (not shown) and undergo another conformation change "en bloc" to form fibrils. They are termed prefibrillar oligomers because they are transient intermediates that ultimately become fibrils. Alternatively, amyloidogenic monomer can aggregate to adopt a fibrillar conformation recognized by OC antibody (right pathway). The resulting fibrillar oligomers may represent fibril nuclei which are the minimal stable aggregate that is capable of elongating by recruiting additional monomers. Addition of monomers on to the ends of fibrillar oligomers and fibrils result in fibril growth. The distinction between fibrillar oligomers and fibrils is based on an arbitrary size difference as no conformation difference is apparent. Fibrils may be distinct from fibrillar oligomers on the basis of their content of multiple protofilaments (not shown) but this does not necessarily imply a necessary conformation difference in their integral peptide constituents.

Mentions: The fact that the epitopes recognized by OC and A11 are generic and mutually exclusive indicate that the conformational difference between fibrils and prefibrillar oligomers is a widespread and fundamental distinction for many different types of amyloids. This fundamental conformational difference forms an ideal and rational basis for the nomenclature of amyloid assembly states. We propose that oligomers can be classified as at least two distinct types: prefibrillar oligomers and fibrillar oligomers (Fig. 9). Prefibrillar oligomers are defined as an assembly state that can ultimately convert to a fibrillar state by concerted or "en bloc" conformational conversion, while fibrillar oligomers grow predominantly by addition of monomer to the ends without undergoing further conformational change. This elongation would involve a conformation conversion at the level of the monomer. The distinction between a fibrillar oligomer and a fibril is on the basis of size and it seems likely that there is a continuous distribution of potential sizes that vary by a single monomeric subunit. There is no obvious demarcation between fibrillar oligomers and fibrils, suggesting that the distinction is necessarily arbitrary and operational. This does not imply that size is not important pathologically as small oligomers may have more diffusional freedom than large fibrils and therefore may be able to move more freely and bind reversibly to cellular targets.


Fibril specific, conformation dependent antibodies recognize a generic epitope common to amyloid fibrils and fibrillar oligomers that is absent in prefibrillar oligomers.

Kayed R, Head E, Sarsoza F, Saing T, Cotman CW, Necula M, Margol L, Wu J, Breydo L, Thompson JL, Rasool S, Gurlo T, Butler P, Glabe CG - Mol Neurodegener (2007)

Schematic representation of the distinct types of amyloid oligomers and their relationships to amyloid fibrils. Amyloid aggregation pathways begin with misfolded amyloidogenic monomer (top) and can diverge in two directions depending on which conformation it adopts. It can aggregate to form prefibrillar oligomers by adopting the conformation recognized by A11 (left pathway). These prefibrillar oligomers then align to form protofibrils (not shown) and undergo another conformation change "en bloc" to form fibrils. They are termed prefibrillar oligomers because they are transient intermediates that ultimately become fibrils. Alternatively, amyloidogenic monomer can aggregate to adopt a fibrillar conformation recognized by OC antibody (right pathway). The resulting fibrillar oligomers may represent fibril nuclei which are the minimal stable aggregate that is capable of elongating by recruiting additional monomers. Addition of monomers on to the ends of fibrillar oligomers and fibrils result in fibril growth. The distinction between fibrillar oligomers and fibrils is based on an arbitrary size difference as no conformation difference is apparent. Fibrils may be distinct from fibrillar oligomers on the basis of their content of multiple protofilaments (not shown) but this does not necessarily imply a necessary conformation difference in their integral peptide constituents.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2100048&req=5

Figure 9: Schematic representation of the distinct types of amyloid oligomers and their relationships to amyloid fibrils. Amyloid aggregation pathways begin with misfolded amyloidogenic monomer (top) and can diverge in two directions depending on which conformation it adopts. It can aggregate to form prefibrillar oligomers by adopting the conformation recognized by A11 (left pathway). These prefibrillar oligomers then align to form protofibrils (not shown) and undergo another conformation change "en bloc" to form fibrils. They are termed prefibrillar oligomers because they are transient intermediates that ultimately become fibrils. Alternatively, amyloidogenic monomer can aggregate to adopt a fibrillar conformation recognized by OC antibody (right pathway). The resulting fibrillar oligomers may represent fibril nuclei which are the minimal stable aggregate that is capable of elongating by recruiting additional monomers. Addition of monomers on to the ends of fibrillar oligomers and fibrils result in fibril growth. The distinction between fibrillar oligomers and fibrils is based on an arbitrary size difference as no conformation difference is apparent. Fibrils may be distinct from fibrillar oligomers on the basis of their content of multiple protofilaments (not shown) but this does not necessarily imply a necessary conformation difference in their integral peptide constituents.
Mentions: The fact that the epitopes recognized by OC and A11 are generic and mutually exclusive indicate that the conformational difference between fibrils and prefibrillar oligomers is a widespread and fundamental distinction for many different types of amyloids. This fundamental conformational difference forms an ideal and rational basis for the nomenclature of amyloid assembly states. We propose that oligomers can be classified as at least two distinct types: prefibrillar oligomers and fibrillar oligomers (Fig. 9). Prefibrillar oligomers are defined as an assembly state that can ultimately convert to a fibrillar state by concerted or "en bloc" conformational conversion, while fibrillar oligomers grow predominantly by addition of monomer to the ends without undergoing further conformational change. This elongation would involve a conformation conversion at the level of the monomer. The distinction between a fibrillar oligomer and a fibril is on the basis of size and it seems likely that there is a continuous distribution of potential sizes that vary by a single monomeric subunit. There is no obvious demarcation between fibrillar oligomers and fibrils, suggesting that the distinction is necessarily arbitrary and operational. This does not imply that size is not important pathologically as small oligomers may have more diffusional freedom than large fibrils and therefore may be able to move more freely and bind reversibly to cellular targets.

Bottom Line: The resulting immune serum (OC) specifically recognizes fibrils, but not random coil monomer or prefibrillar oligomers, indicating fibrils display a distinct conformation dependent epitope that is absent in prefibrillar oligomers.The fibril specific antibody also recognizes 100,000 x G soluble fibrillar oligomers ranging in size from dimer to greater than 250 kDa on western blots.Diffuse amyloid deposits stain intensely with anti-fibril antibody although they are thioflavin S negative, suggesting that they are indeed fibrillar in conformation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697, USA. cglabe@uci.edu.

ABSTRACT

Background: Amyloid-related degenerative diseases are associated with the accumulation of misfolded proteins as amyloid fibrils in tissue. In Alzheimer disease (AD), amyloid accumulates in several distinct types of insoluble plaque deposits, intracellular Abeta and as soluble oligomers and the relationships between these deposits and their pathological significance remains unclear. Conformation dependent antibodies have been reported that specifically recognize distinct assembly states of amyloids, including prefibrillar oligomers and fibrils.

Results: We immunized rabbits with a morphologically homogeneous population of Abeta42 fibrils. The resulting immune serum (OC) specifically recognizes fibrils, but not random coil monomer or prefibrillar oligomers, indicating fibrils display a distinct conformation dependent epitope that is absent in prefibrillar oligomers. The fibril epitope is also displayed by fibrils of other types of amyloids, indicating that the epitope is a generic feature of the polypeptide backbone. The fibril specific antibody also recognizes 100,000 x G soluble fibrillar oligomers ranging in size from dimer to greater than 250 kDa on western blots. The fibrillar oligomers recognized by OC are immunologically distinct from prefibrillar oligomers recognized by A11, even though their sizes overlap broadly, indicating that size is not a reliable indicator of oligomer conformation. The immune response to prefibrillar oligomers and fibrils is not sequence specific and antisera of the same specificity are produced in response to immunization with islet amyloid polypeptide prefibrillar oligomer mimics and fibrils. The fibril specific antibodies stain all types of amyloid deposits in human AD brain. Diffuse amyloid deposits stain intensely with anti-fibril antibody although they are thioflavin S negative, suggesting that they are indeed fibrillar in conformation. OC also stains islet amyloid deposits in transgenic mouse models of type II diabetes, demonstrating its generic specificity for amyloid fibrils.

Conclusion: Since the fibril specific antibodies are conformation dependent, sequence-independent, and recognize epitopes that are distinct from those present in prefibrillar oligomers, they may have broad utility for detecting and characterizing the accumulation of amyloid fibrils and fibrillar type oligomers in degenerative diseases.

No MeSH data available.


Related in: MedlinePlus