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)

Proteolytic processing of the beta-amyloid precursor proteins (APP) is required for release of the beta/A4 protein and its deposition into the amyloid plaques characteristic of aging and Alzheimer's disease. We have examined the involvement of acidic intracellular compartments in APP processing in cultured human cells. The use of acidotropic agents and inhibitors to a specific class of lysosomal protease, coupled with metabolic labeling and immunoprecipitation, revealed that APP is degraded within an acidic compartment to produce at least 12 COOH-terminal fragments. Nine likely contain the entire beta/A4 domain and, therefore, are potentially amyloidogenic. Treatment with E64 or Z-Phe-Ala-CHN2 irreversibly blocked activities of the lysosomal cysteine proteases cathepsins B and L but did not inhibit the lysosomal aspartic protease cathepsin D and did not alter the production of potentially amyloidogenic fragments. Instead, the inhibitors prevented further degradation of the fragments. Thus, large numbers of potentially amyloidogenic fragments of APP are routinely generated in an acidic compartment by noncysteine proteases and then are eliminated within lysosomes by cysteine proteases. Immunoblot and immunohistochemical analyses confirmed that chronic cysteine protease inhibition leads to accumulation of potentially amyloidogenic APP fragments in lysosomes. The results provide further support for the hypothesis that an acidic compartment may be involved in amyloid formation and begin to define the proteolytic events that may be important for amyloidogenesis.
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PMID:Processing of the beta-amyloid precursor. Multiple proteases generate and degrade potentially amyloidogenic fragments. 834 42

To understand the bone resorption and lysosomal proteinases in osteoclasts, we examined by immunohistochemistry the localization of lysosomal cysteine and aspartic proteinases, acid phosphatase, and cystatin-beta in the rat tibial bone. Immunoreactivity for cathepsins B, C, H, and L, cathepsin D, acid phosphatase, and cystatin-beta was demonstrated in various cells of the bone tissue; in particular, large multinucleated osteoclasts attached to the bone surface and chondroclasts in the proximal growth plate. These cells showed intense immunoreactivity for these lysosomal enzymes and cystatin-beta. Bone surface-lining osteoblasts displayed distinct immunoreactivity for cathepsins B, C, D, H, and acid phosphatase, while osteocytes often exhibited that for cathepsins D, H and acid phosphatase. Chondrocytes in the growth plate demonstrated intense immunoreactivity for cathepsins B, D, and acid phosphatase. Immunoreactivity for cystatin-beta was detected in osteoclasts and chondroclasts only. Large, round multinucleated cells free from the bone surface exhibited weak, faint, or no immunoreactivity for the lysosomal enzymes and cystatin-beta. These results suggest that lysosomal cysteine and aspartic proteinases may play a role in the degradation of organic constituents of the bone matrix. Moreover, cystatin-beta can serve as an excellent marker protein for osteoclasts.
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PMID:Lysosomal cysteine and aspartic proteinases, acid phosphatase, and an endogenous cysteine proteinase inhibitor, cystatin-beta, in rat osteoclasts. 851 49

Extravasation and intravasation of tumor cells in solid malignant tumors is controlled by 3 steps: 1) attachment to and interaction of tumor cells with components of the basement membrane and the extracellular matrix, 2) local proteolysis, and 3) tumor cell migration. Evidence has accumulated that different types of tumor-associated proteases, their inhibitors and receptors are involved in tumor invasion and metastasis. Four different classes of proteases are known to be correlated with the malignant phenotype: 1) Matrix metalloproteases; including collagenases, gelatinases and stromelysins. 2) Cysteine proteases; including cathepsins B and L. 3) Aspartyl protease cathepsin D. 4) Serine proteases; including plasmin and tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA). A strong independent prognostic value (relapse-free and/or overall survival) has especially been demonstrated for uPA and its inhibitor PAI-1 in patients with cancer of the breast, ovary, stomach, esophagus, colon, lung, and kidney thus predicting the course of the cancer disease. The strong correlation between elevated uPA and/or PAI-1 values in primary cancer tissues and the malignant phenotype of cancer cells has prompted to explore new tumor biology-oriented concepts in order to suppress uPA or uPA receptor (CD87) expression or to abrogate interaction of uPA with CD87. Various very different approaches to interfere with the expression or reactivity of uPA or CD87 at the gene or protein level were successfully tested including antisense oligonucleotides, antibodies, inhibitors and recombinant or synthetic uPA and CD87 analogues.
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PMID:Urokinase-type plasminogen activator (uPA) and its receptor (CD87): a new target in tumor invasion and metastasis. 855 77

We previously reported that a substantial amount of newly synthesized apoE in mouse macrophages is degraded prior to secretion; a portion of this pool of apoE can be rescued by the addition of HDL3 to the incubation medium. In the present studies, the location and nature of the intracellular degradation of apoE were more closely examined. Inhibitors of protein trafficking (brefeldin A) as well as a number of protease inhibitors were used. The experiments using brefeldin A (5 micrograms/ml) clearly established that neither the endoplasmic reticulum nor the Golgi complex are the sites of apoE degradation. Using a pulse-chase design, [35S]apoE cannot be chased out in the presence of brefeldin A and remains undegraded within the cell. The accumulated apoE lacks the sialic acid residues, indicating that this final stage of processing must occur in the trans-Golgi network or later. Lysosomotropic agents, ammonium chloride and chloroquine, on the other hand, inhibit apoE degradation by over 70 and 80%, respectively, while total cell protein degradation remains unaffected. Similarly, a cocktail consisting of four lysosomal protease inhibitors (pepstatin, E-64, chymostatin, and antipain), inhibits specifically apoE degradation by over 60%. In contrast, ALLN, an inhibitor of Ca(2+)-dependent cysteine proteases, has a moderate effect on apoE degradation (30% inhibition) and a more pronounced effect on total protein degradation. These data suggest that the site of intracellular apoE degradation in the macrophage is the lysosome. These conclusions are supported by light and electron microscopy of macrophages, clearly showing the presence of immunoreactive apoE (along with cathepsin D) in the endosomal/lysosomal compartment of control and lysosomotropic agent-treated cells. In contrast, little or no labeling is seen in this compartment in brefeldin A-treated cells. At lower concentrations of the lysosomotropic agents, the extent of inhibition of apoE degradation is compensated for by its increased secretion, in a manner analogous to the effect of these agents on lysosomal enzymes. Higher concentrations of these agents, which lead to a profound inhibition of apoE degradation, also specifically block apoE secretion. The block in apoE secretion in the presence of high concentrations of chloroquine leads to undiminished or higher concentrations of immunoreactive apoE in the endosomal/lysosomal compartment, suggesting that apoE is targeted for lysosomal degradation directly, without prior secretion or surface association. These data strongly suggest pH-dependent sorting of apoE in macrophages to the degradative and secretory pathways and imply a protein-protein interaction in the process.
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PMID:Lysosomal degradation and sorting of apolipoprotein E in macrophages. 857 39

Brain lysosomes were isolated from rat cerebra by Percoll density gradient centrifugation. The lysosomes had little and no contamination by marker enzymes from mitochondria and other organellae, respectively, and the yield was approximately 14% of the postnuclear supernatant. The activities of cathespins B, L, and/or J were similar to those of liver or kidney lysosomes, but the levels of cathepsin H activity were much lower than those of liver or kidney lysosomes. The degradation of native L-lactate dehydrogenase (LDH) and rat serum albumin by the isolated brain lysosomes in vitro was markedly suppressed by a low level of the cysteine proteinase inhibitor cystatin alpha, with slight inhibition of the activities of cathepsins B, L, and/or J. The degradation of rat serum albumin was also considerably inhibited by N-(L-3-trans-propylcarbamoyloxirane-2-carbonyl)- L-isoleucyl-L-proline (CA-074), a selective inhibitor of cathepsin B. In contrast, the degradation of brain proteins from the postmitochondrial supernatant by the same brain lysosomes was not or little suppressed by the same concentration of either inhibitor. However, it was considerably suppressed by leupeptin with marked inhibition of the activities of cathepsins B, L, and/or J, and with only slight inhibition of cathepsin H, indicating that cysteine proteinases that are highly sensitive to leupeptin are involved in the lysosomal degradation of the brain proteins. It was also moderately suppressed by pepstatin, an inhibitor of cathepsin D and was almost completely suppressed by a combination of leupeptin and pepstatin.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Simple preparation of rat brain lysosomes and their proteolytic properties. 858 28

We have examined whether the two cysteine residues (Cys30 and Cys34) in the cytoplasmic tail of the cation-dependent mannose 6-phosphate receptor are palmitoylated via thioesters and whether these residues influence the biologic function of the receptor. To do this, mouse L cells expressing wild-type and mutant receptors were analyzed by metabolic labeling with [3H]palmitate, immunoprecipitation, and SDS-PAGE. Both Cys30 and Cys34 were found to be sites of palmitoylation and together they accounted for the total palmitoylation of the receptor. The palmitate rapidly turned over with a half-life of approximately 2 h compared to a half-life of greater than 40 h for the protein. Mutation of Cys34 to Ala resulted in the gradual accumulation of the receptor in dense lysosomes and the total loss of cathepsin D sorting function in the Golgi. A Cys30 to Ala mutation had no biologic consequences, showing the importance of Cys34. Mutation of amino acids 35-39 to alanines impaired palmitoylation of Cys30 and Cys34 and resulted in abnormal receptor trafficking to lysosomes and loss of cathepsin D sorting. These data suggest that palmitoylation of Cys30 and Cys34 leads to anchoring of this region of the cytoplasmic tail to the lipid bilayer. Anchoring via Cys34 is essential for the normal trafficking and lysosomal enzyme sorting function of the receptor.
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PMID:Cysteine34 of the cytoplasmic tail of the cation-dependent mannose 6-phosphate receptor is reversibly palmitoylated and required for normal trafficking and lysosomal enzyme sorting. 864 89

Recent studies suggest that aspartic proteinase cathepsin D may be implicated in tumor invasion and metastasis either directly by degrading extracellular matrix or indirectly by activating the cysteine proteinases such as procathepsin B, H, and L to mature forms or by inactivating cysteine proteinase inhibitors. In this study we determined for the first time whether increased levels of cathepsin D correlate with glioma progression by enzymatic assay, ELISA, and western blotting. Cathepsin D activity and content were higher in anaplastic astrocytoma and in glioblastoma tissue extracts especially when compared to normal brain tissue and low-grade gliomas. There was a significantly increased intensity of an M(r) 29,000 band in glioblastoma and anaplastic astrocytoma compared to low-grade glioma and normal brain tissue on Western blotting analysis using its specific antibodies. Cathepsin D antibody inhibited the invasion of glioblastoma cell lines in a dose-dependent manner. These results suggest that the expression of cathepsin D is dramatically upregulated in malignant gliomas, and that its increase correlates with the malignant progression of human gliomas in vivo.
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PMID:Expression of cathepsin D during the progression of human gliomas. 873 97

Affinity-purified lysosomal protease cathepsin D cleaved recombinant human IGFBP-1 to -5 in fragments of defined sizes, while IGFBP-6 was not degraded. To assess the role of cathepsin D for proteolytic processing of IGFBP in vivo, serum from cathepsin D-deficient mice and conditioned media from cathepsin D-deficient fibroblasts and organ explants were analyzed. No differences for the pattern and level of IGFBPs were detected. When conditioned media from fibroblasts were incubated at acid pH, proteolysis of IGFBP-1 and -4 was observed only in media derived from cathepsin D-expressing cells. Additional experiments showed that the proteolysis of IGFBP-4 is mediated by cathepsin D and not by a protease activated by cathepsin D. The IGFBP-4 degrading activities in media from organ explants from cathepsin D-deficient mice were found to be sensitive to inhibitors of aspartyl and cysteine proteases. The data indicate that different classes of acid pH-dependent proteases can contribute to the regulation of IGFBP-4 abundance.
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PMID:Proteolysis of IGFBPs by cathepsin D in vitro and in cathepsin D-deficient mice. 881 69

The cysteine present in the Ig micro chain tailpiece (microtp) prevents the secretion of unpolymerized IgM intermediates and causes their accumulation in the endoplasmic reticulum (ER). In principle, this can be the consequence of actual retention in this organelle or of retrieval from the Golgi. To determine which of the two mechanisms underlies the cysteine-dependent ER localization, we analyze here the post-translational modifications of suitably engineered cathepsin D (CD) molecules. The glycans of this protease are phosphorylated by post-ER phosphotransferases and further modified in the trans-Golgi to generate a mannose 6-phosphate lysosome targeting signal. Only trace amounts of the mutp-tagged CD (CDM&mutpCys) are phosphorylated, unless retention is reversed by exogenous reducing agents or the critical cysteine mutated (CDMmutpSer). In contrast, a KDEL-tagged CD, that is retrieved from the Golgi into the ER, acquires phosphates, though mainly resistant to alkaline phosphatase. Similarly to CDMmutpSer, the few CDMmutpCys molecules that escape retention and acquire phosphates in the cis-Golgi are transported beyond the KDEL retrieval compartment, as indicated by their sensitivity to alkaline phosphatase. These results demonstrate that the thiol-dependent ER localization arises primarily from true retention, without recycling through the Golgi.
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PMID:Exposed thiols confer localization in the endoplasmic reticulum by retention rather than retrieval. 882 58

To examine localization of cysteine and aspartic proteinases, and ubiquitin in rat and human urinary bladders, immunocytochemistry was applied to the tissues. In semi-thin sections, immunoreactivity for cathepsins B and D was densely localized throughout epithelial layers of rats and humans, while that for cathepsins H and L was mainly localized in rat superficial and human intermediate cells. Immunoreactivity for cathepsin C was relatively high in rat and human epithelia, especially in humans. Immunoreactivity for ubiquitin was detected in rat and human epithelial cells. By electron microscopy, vesicular or heterogeneously dense lysosomes labeled with immunogold particles indicating cathepsin B were seen in rat and human epithelial cells; particularly, they often appeared near fusiform vesicles in rat superficial cells and in human intermediate and superficial cells. By double immunostaining, lysosomes with or without vesicular structures were co-labeled with immunogold particles showing both cathepsin B and ubiquitin. The results suggest that cathepsins B, C, H, and L, and cathepsin D are involved in the lysosomal system of rat and human bladder epithelia. Moreover, considering that ubiquitin is a cofactor in the soluble ATP-dependent proteolysis, the results may also indicate that epithelial cells actively form autophagolysosomes.
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PMID:Lysosomal cysteine and aspartic proteinases and ubiquitin in rat and human urinary bladder epithelium. 887 57


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