Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.23.5 (cathepsin D)
4,130 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The formation of beta-amyloid in the brains of individuals with Alzheimer disease requires the proteolytic cleavage of a membrane-associated precursor protein. The proteases that may be involved in this process have not yet been identified. Cathepsins are normally intracellular proteolytic enzymes associated with lysosomes; however, when sections from Alzheimer brains were stained by antisera to cathepsin D and cathepsin B, high levels of immunoreactivity were also detected in senile plaques. Extracellular sites of cathepsin immunoreactivity were not seen in control brains from age-matched individuals without neurologic disease or from patients with Huntington disease or Parkinson disease. In situ enzyme histochemistry of cathepsin D and cathepsin B on sections of neocortex using synthetic peptides and protein substrates showed that senile plaques contained the highest levels of enzymatically active cathepsin. At the ultrastructural level, cathepsin immunoreactivity in senile plaques was localized principally to lysosomal dense bodies and lipofuscin granules, which were extracellular. Similar structures were abundant in degenerating neurons of Alzheimer neocortex, and cathepsin-laden neuronal perikarya in various stages of disintegration could be seen within some senile plaques. The high levels of enzymatically competent lysosomal proteases abnormally localized in senile plaques represent evidence for candidate enzymes that may mediate the proteolytic formation of amyloid. We propose that amyloid precursor protein within senile plaques is processed by lysosomal proteases principally derived from degenerating neurons. Escape of cathepsins from the stringently regulated intracellular milieu provides a basis for an abnormal sequence of proteolytic cleavages of accumulating amyloid precursor protein.
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PMID:Enzymatically active lysosomal proteases are associated with amyloid deposits in Alzheimer brain. 169 25

Formalin-fixed paraffin-embedded hippocampal sections of brains with early-onset and late-onset Alzheimer's disease were studied immunohistochemically with antisera against cathepsin D and cathepsin B. In addition to the staining of neuronal perikarya, some of the senile plaques visualized by Bielshowsky silver staining and some of reactive astrocytes were positively stained with the antisera against cathepsin D and cathepsin B in brains with Alzheimer's disease. Abnormal localization of cathepsin D and cathepsin B immunoreactivity in neuronal perikarya was observed in brains with early-onset Alzheimer's disease. These findings demonstrate that the distribution of lysosomal proteases was altered in brains with Alzheimer's disease, suggesting the primary and/or secondary involvement of the lysosomal proteases in the pathological process of Alzheimer's disease.
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PMID:Abnormal distribution of cathepsins in the brain of patients with Alzheimer's disease. 179 81

With the rationale that the neuropathological similarities between scrapie and Alzheimer's disease reflect convergent pathological mechanisms involving altered gene expression, we set out to identify molecular events involved in both processes, using scrapie as a model to study the time course of these changes. We differentially screened a cDNA library constructed from scrapie-infected mice to identify mRNAs that increase or decrease during disease and discovered in this way two mRNAs that are increased in scrapie and Alzheimer's disease. These mRNAs were subsequently shown by sequence analysis to encode apolipoprotein E and cathepsin D (EC 3.4.23.5). Using in situ hybridization and immunocytochemistry to define the cellular and anatomic pathology of altered gene expression, we found that in both diseases the increase in apolipoprotein E and cathepsin D mRNAs and proteins occurred in activated astrocytes. In scrapie, the increase in gene expression occurred soon after the amyloid-forming abnormal isoform of the prion protein has been shown to accumulate in astrocytes. In Alzheimer's disease, the increased expression of cathepsin D also occurred in association with beta-amyloid. These studies reveal some of the molecular antecedents of neuropathological changes in scrapie and Alzheimer's disease and accord new prominence to the role of astrocytes in neurodegenerative conditions.
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PMID:Neuropathological changes in scrapie and Alzheimer's disease are associated with increased expression of apolipoprotein E and cathepsin D in astrocytes. 187 Feb

To investigate the role of proteolysis in amyloid formation, we studied the localization of the proteolytic enzymes, cathepsin D and cathepsin B, in the prefrontal cerebral cortex and hippocampus of human postmortem brains from patients with Alzheimer's disease and from individuals free of neurological disease. In control and Alzheimer brains, cathepsin immunoreactivity within cells was localized to lysosome-related structures, which were particularly abundant in neuronal perikarya. In Alzheimer brain, cathepsin immunoreactivity was also heavily concentrated extracellularly within senile plaques. Cathepsin immunoreactivity associated with plaques was not confined to lysosomes and was distributed throughout the plaque. Isolated amyloid cores, however, were not immunostained. Cathepsin-laden perikarya of degenerating neurons were frequently seen within senile plaques and, in the more advanced stages of degeneration, cathepsin immunoreactivity was present throughout the cytoplasm. Other identified constituents of senile plaques appeared to be less significant sources of cathepsin immunoreactivity, including astrocytes, degenerating neurites, microglia and macrophages. These results demonstrate that lysosomal proteinases are major constituents of the senile plaque and that degenerating neuronal perikarya are a principal source of the cathepsin immunoreactivity. We propose that the unregulated action of extracellular cathepsins liberated from degenerating neurons may lead to abnormal processing of the amyloid precursor protein and to the formation of amyloid locally within senile plaques in Alzheimer's disease.
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PMID:Lysosomal proteinase antigens are prominently localized within senile plaques of Alzheimer's disease: evidence for a neuronal origin. 235 Jun 88

In microtubules isolated from brains of very old rats, two of the major microtubule-associated proteins, MAP1 and MAP2, are found only in degraded form. MAP1 is present as a piece whose molecular weight on sodium dodecyl sulfate-polyacrylamide gel electrophoresis is circa 50,000 smaller than the native protein, and MAP2 is extensively fragmented. The native forms of both proteins are present in tissue homogenates but are rapidly degraded during microtubule isolation. The proteolytic activity responsible for this degradation is cathepsin D like, being more active at acid pH than neutral and being completely blocked by pepstatin at 10(-7) M. Fractionation of aged brain supernatant by gel permeation chromatography showed that the MAP1 and MAP2 degrading activity elutes with a single peak of cathepsin D like activity. MAP1 and MAP2 are known to promote microtubule assembly, and their degradation by a protease whose levels increase with age could be related to defective microtubule assembly which is known to occur in age-related degenerative conditions such as Alzheimer's disease.
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PMID:Age-related increase in a cathepsin D like protease that degrades brain microtubule-associated proteins. 332 17

Rabbits were injected intracerebrally with aluminum salt leading to experimental neurofibrillary change formation as a model of Alzheimer neurofibrillary change. Eleven days after the injection, the brain tissues were excised from the cortex, hippocampus, and cervical region of spinal cord. Five lysosomal enzymes (cathepsin D, beta-glucuronidase, acid phosphatase, acid DNase, alkaline DNase) were assayed and compared with the control. Cathepsin D, acid DNase and beta-glucuronidase activities increased significantly in all 3 areas of aluminum-injected brain. On the other hand, acid phosphatase and alkaline DNase activities remained at the same level. The results showed the lysosomal enzymes did not change in parallel after aluminum administration, suggesting a role of the increased enzymes in the brain with neurofibrillary changes.
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PMID:Activities of lysosomal enzymes in rabbit brain with experimental neurofibrillary changes. 339 97

The nature of the inclusions in the human muscle disease inclusion-body myositis (IBM) has been the subject of debate. Parallels with Alzheimer's disease have been drawn after these inclusions were found to be ubiquitinated, and immunoreactive with antibodies to beta-amyloid (A beta) and certain amyloid-associated proteins. We have used a battery of antibodies against A beta and associated proteins to immunostain muscle biopsies from patients with IBM. Although the inclusions are ubiquitinated, we could not show immunoreactivity for A beta or the associated proteins investigated. We did, however, find that the ubiquitinated inclusions colocalised with the lysosomal marker, cathepsin D.
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PMID:Ubiquitinated inclusions in inclusion-body myositis patients are immunoreactive for cathepsin D but not beta-amyloid. 747 7

A major pre-beta-amyloid protein695 (APP695) processing activity from Alzheimer's disease brain extracts was identified and found to be indistinguishable from the activity of cathepsin D.APP695 processing activity cleaved APP695 into a series of fragments that reacted on immunoblots to a monoclonal antibody (C286.8a) against beta-amyloid-(1-7)-peptide and cleaved N-dansyl-APP-(591-601)-amide at the Glu-Val and Met-Asp bonds. Fragments of 5.5 kDa and 10-12 kDa were formed from the cleavage of APP695 by cathepsin D at the Glu593-Val594 bond, and had the same N-terminus as a minor form of beta-amyloid released by cells. The Lys595-->Asn and Met596-->Leu substitutions found in a pedigree of familial Alzheimer's disease, increased the cathepsin D-catalyzed rate of accumulation of 5.5 kDa and 10-12 kDa C286.8a-reactive fragments 5-10fold. This substitution also increased the rate of N-dansyl-APP-(591-601)-amide cleavage at the Xaa-Asp bond by up to 41-fold. These observations suggest a role of cathepsin D in beta-amyloid formation under certain circumstances.
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PMID:Processing of the pre-beta-amyloid protein by cathepsin D is enhanced by a familial Alzheimer's disease mutation. 752 15

Recent evidence, based upon immunocytochemical and histochemical analysis of brain cortical tissue from alzheimer's disease patients, has suggested that altered activity and/or distribution of the lysosomal proteases cathepsins B and D may be implicated in the abnormal protein processing pathway resulting in formation of the neurotoxic amyloid A4 peptide, characteristic of this neurodegenerative disorder. We have therefore compared, via biochemical assay techniques using conventional or specially synthesised (corresponding to protein cleavage points of relevant to A4 peptide formation) fluorogenic substrates, the levels of activity of the lysosomal proteases cathepsins B, D, H and L, and dipeptidyl aminopeptidases I and II in frontal cortex (grey/white matter) from control and Alzheimer's disease patients. For comparative purposes, activity levels of the above enzymes were also determined in frontal cortex tissue from cases with Lewy body dementia and Parkinson's disease, and in caudate tissue from control and Huntington's disease cases. There was no significant difference in activity for any protease types in tissue from control cases and cases with Alzheimer's disease, Lewy body dementia or Parkinson's disease, with the exception of reduced dipeptidyl aminopeptidase II activity in Lewy body dementia and Parkinson's cases. We have therefore been unable to confirm a potential role for lysosomal cathepsins in the characteristic neurodegeneration associated with Alzheimer's disease; however the finding of significant increases in activity of dipeptidyl aminopeptidase II, cathepsin H and cathepsin D specifically in cases with Huntington's disease is of particular note. We therefore suggest the potential role of the latter enzymes in the pathogenesis of Huntington's disease requires further investigation.
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PMID:Comparison of cathepsin protease activities in brain tissue from normal cases and cases with Alzheimer's disease, Lewy body dementia, Parkinson's disease and Huntington's disease. 756 49

To investigate the potential contribution of the lysosomal compartment in the processing of amyloid precursor protein (APP) to amyloid beta-peptides (A beta s), we stably overexpressed a series of lysosomal proteases (the cysteine proteases, cathepsins B, L and S, and the aspartic protease, cathepsin D) in a human kidney epithelial cell line (293) transfected to express high levels of beta APP. Preliminary experiments indicated that 293 cells endogenously synthesize cathepsins B, L and D, but not cathepsin S. A beta secretion was assessed by immunoprecipitation and ELISA and found to be increased approximately 2-fold following cathepsin S expression, but to be unchanged (cathepsins B, L) or decreased (cathepsin D) in the other double transfectants. E-64d, an inhibitor of lysosomal cysteine proteases, significantly reduced A beta secretion by the cathepsin S transfectants, but had no effect on cells expressing the other proteases. Radiosequencing of A beta secreted by cathepsin S-expressing cells revealed that a previously unreported variant beginning at Met -1 (relative to the most common A beta N-terminus, Asp -1) accounted for most of the increase in A beta secretion. Immunostaining of human brain sections revealed cathepsin S in cortical neurons and glia in samples of brain from patients with Alzheimer's disease. These results provide evidence in living cells for a pathway in which cathepsin S generates A beta from amyloidogenic fragments of beta APP in the endosomal/lysosomal compartment. This pathway appears to be inducible, distinct from a constitutive pathway used by 293 and other cells to generate A beta, and may be relevant to the pathogenesis of Alzheimer's disease.
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PMID:Lysosomal processing of amyloid precursor protein to A beta peptides: a distinct role for cathepsin S. 757 68


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