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To date, 37 human proteins have been found to form amyloid in pathology and be associated with well-defined diseases. [2] The International Society of Amyloidosis classifies amyloid fibrils and their associated diseases based upon associated proteins (for example ATTR is the group of diseases and associated fibrils formed by TTR). [3]
Amyloid beta (Aβ) is a small protein, most often 40 or 42 amino acids in length, that is released from a longer parent protein called the Aβ-precursor protein (APP). [24] APP is produced by many types of cell in the body, but it is especially abundant in neurons. It is a single-pass transmembrane protein, passing once through cellular membranes.
Amyloid-beta precursor protein is highly versatile with several isoforms generated through alternative splicing of its mRNA. The primary isoforms include APP695, APP751, and APP770, differing in their inclusion of certain exons, mainly exon 7 and 8. APP695 is predominantly expressed in neuronal cells and is crucial for normal neuronal function.
Brain Aβ is elevated in people with sporadic Alzheimer's disease. Aβ is the main constituent of brain parenchymal and vascular amyloid; it contributes to cerebrovascular lesions and is neurotoxic. [33] [34] [35] It is unresolved how Aβ accumulates in the central nervous system and subsequently initiates the disease of cells. Significant ...
Inclusion bodies have a non-unit (single) lipid membrane [citation needed].Protein inclusion bodies are classically thought to contain misfolded protein.However, this has been contested, as green fluorescent protein will sometimes fluoresce in inclusion bodies, which indicates some resemblance of the native structure and researchers have recovered folded protein from inclusion bodies.
Acute-phase serum amyloid A proteins (A-SAAs) are secreted during the acute phase of inflammation.These proteins have several roles, including the transport of cholesterol to the liver for secretion into the bile, the recruitment of immune cells to inflammatory sites, and the induction of enzymes that degrade extracellular matrix.
According to the prevailing amyloid hypothesis of Alzheimer's disease, the aggregation of amyloid-beta (a peptide normally produced in and cleared from the healthy young brain) into extracellular plaques drives the neuronal loss and brain atrophy that is the hallmark of Alzheimer's dementia.
They are frequently seen in hippocampal pyramidal cells. [5] An experimental model of Hirano body formation has been reported, using a genetically altered strain of the slime mold Dictyostelium discoideum. [6] Hirano bodies have been noted as a function of age without obvious underlying neurodegeneration. [7]