Amyloid and Alzheimer's disease: inside and out.
Summary of "Amyloid and Alzheimer's disease: inside and out."
Alzheimer's disease (AD) is poised to become the most serious healthcare issue of our generation. The leading theory of AD pathophysiology is the Amyloid Cascade Hypothesis, and clinical trials are now proceeding based on this hypothesis. Here, we review the original evidence for the Amyloid Hypothesis, which was originally focused on the extracellular deposition of beta amyloid peptides (Aβ) in large fibrillar aggregates, as well as how this theory has been extended in recent years to focus on highly toxic small soluble amyloid oligomers. We will also examine emerging evidence that Aβ may actually begin to accumulate intracellularly in lysosomes, and the role for intracellular Aβ and lysosomal dysfunction may play in AD pathophysiology. Finally, we will review the clinical implications of these findings.
J. Allyn Taylor Centre for Cell Biology, University of Western Ontario, London, Ontario, Canada Department of Physiology and Pharmacology, Schulich School of Medicine, University of Western Ontario, London, Ontario, Canada.
This article was published in the following journal.
Name: The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques
Medical and Biotech [MESH] Definitions
Amyloid Beta-protein Precursor
A precursor to the AMYLOID BETA-PROTEIN (beta/A4). Alterations in the expression of the amyloid beta-protein precursor (ABPP) gene, located on chromosome 21, plays a role in the development of the neuropathology common to both ALZHEIMER DISEASE and DOWN SYNDROME. ABPP is associated with the extensive extracellular matrix secreted by neuronal cells. Upon cleavage, this precursor produces three proteins of varying amino acid lengths: 695, 751, and 770. The beta/A4 (695 amino acids) or beta-amyloid protein is the principal component of the extracellular amyloid in senile plaques found in ALZHEIMER DISEASE; DOWN SYNDROME and, to a limited extent, in normal aging.
Peptides generated from AMYLOID BETA-PEPTIDES PRECURSOR. An amyloid fibrillar form of these peptides is the major component of amyloid plaques found in individuals with Alzheimer's disease and in aged individuals with trisomy 21 (DOWN SYNDROME). The peptide is found predominantly in the nervous system, but there have been reports of its presence in non-neural tissue.
Cerebral Amyloid Angiopathy
A heterogeneous group of sporadic or familial disorders characterized by AMYLOID deposits in the walls of small and medium sized blood vessels of CEREBRAL CORTEX and MENINGES. Clinical features include multiple, small lobar CEREBRAL HEMORRHAGE; cerebral ischemia (BRAIN ISCHEMIA); and CEREBRAL INFARCTION. Cerebral amyloid angiopathy is unrelated to generalized AMYLOIDOSIS. Amyloidogenic peptides in this condition are nearly always the same ones found in ALZHEIMER DISEASE. (from Kumar: Robbins and Cotran: Pathologic Basis of Disease, 7th ed., 2005)
A 4-kDa protein, 39-43 amino acids long, expressed by a gene located on chromosome 21. It is the major protein subunit of the vascular and plaque amyloid filaments in individuals with Alzheimer's disease and in aged individuals with trisomy 21 (DOWN SYNDROME). The protein is found predominantly in the nervous system, but there have been reports of its presence in non-neural tissue.
A chromosome disorder associated either with an extra chromosome 21 or an effective trisomy for chromosome 21. Clinical manifestations include hypotonia, short stature, brachycephaly, upslanting palpebral fissures, epicanthus, Brushfield spots on the iris, protruding tongue, small ears, short, broad hands, fifth finger clinodactyly, Simian crease, and moderate to severe MENTAL RETARDATION. Cardiac and gastrointestinal malformations, a marked increase in the incidence of LEUKEMIA, and the early onset of ALZHEIMER DISEASE are also associated with this condition. Pathologic features include the development of NEUROFIBRILLARY TANGLES in neurons and the deposition of AMYLOID BETA-PROTEIN, similar to the pathology of ALZHEIMER DISEASE. (Menkes, Textbook of Child Neurology, 5th ed, p213)
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