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 effects of various protease inhibitors on the degradation of cadmium metallothionein (Cd-MT) by lysosomal proteases were studied in vitro. Degradation of Cd-MT was observed after incubation with the lysosomal extracts, but not after incubation with the cytosol or heat-treated lysosomal extracts. After incubation of [35S]-Cd-MT or 109Cd-MT with lysosomal extracts, 35S and 109Cd radioactivity in the MT fraction decreased, while the low molecular weight (LM) fraction increased with time (half life; 3 hr). When EDTA was added to this incubation mixture, most of the MT was degraded within 30 min. Cd in the LM fraction, produced after the incubation of Cd-MT with the lysosomal extracts, was moved to the high molecular weight fraction by the addition of cytosol. Both leupeptin and E-64, which reduced cathepsin B (cysteine protease) activity, inhibited the degradation of Cd-MT by the lysosomal extracts. But pepstatin A, a specific inhibitor of cathepsin D, did not inhibit this degradation. E-64 inhibited degradation, as well as inhibiting cathepsin B activity, in accordance with its concentration in the incubation mixture. The incubation of Cd-MT with purified cathepsin B resulted in its degradation which was inhibited by E-64. These results suggest that Cd-MT may be broken down by the cysteine protease in lysosomes and that the released Cd bound low molecular weight fragment(s) was subsequently transferred to the high molecular weight protein in cytosol.
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PMID:Degradation of cadmium metallothionein in vitro by lysosomal proteases. 156 39

1. Increases in activities of muscle muticatalytic proteinase, modori-inducing proteinase (latent trypsin-like proteinase), cathepsin B and L-like proteases and cathepsin D were observed more markedly for male fish than female fish, in the spawning stage. 2. Decreases in inhibitory activities of muscle serine and cysteine protease inhibitors were observed more markedly for male fish than female fish in the spawning stage.
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PMID:Effect of maturation on activities of various proteases and protease inhibitors in the muscle of Ayu (Plecoglossus altivelis). 176 22

3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase is a key regulatory enzyme of cholesterol biosynthesis and is located in the endoplasmic reticulum (ER). A fusion protein, HMGal, consisting of the membrane domain of HMG-CoA reductase fused to Escherichia coli beta-galactosidase and expressed in Chinese hamster ovary (CHO) cells from the SV40 promoter, was previously constructed and was found to respond to regulatory signals for degradation in a similar fashion to the intact HMG-CoA reductase. Degradation of both HMG-CoA reductase and HMGal in CHO cells was enhanced by addition of mevalonate or low density lipoprotein (LDL). In this report we show that 2 cysteine protease inhibitors, N-acetyl-leucyl-leucyl-norleucinal (ALLN) and N-acetyl-leucyl-leucyl-methioninal (ALLM), completely inhibit the mevalonate- or LDL-accelerated degradation of HMG-CoA reductase and HMGal and also block the basal degradation of these enzymes. It has been shown that in vitro these protease inhibitors inhibit the activities of Ca(2+)-dependent neutral proteases as well as lysosomal proteases, including cathepsin L, cathepsin b, and cathepsin D. However, the mevalonate-accelerated degradation of HMG-CoA reductase and HMGal is not affected by lysosomotropic agents, suggesting that the site of action of these inhibitor peptides in preventing the degradation is not the cathepsins. In brefeldin A-treated cells, where protein export from the ER is blocked, ALLN is still effective in inhibiting the degradation of HMG-CoA reductase and HMGal. These results indicate the involvement of non-lysosomal Ca(2+)-dependent proteases in the basal and the accelerated degradation of HMG-CoA reductase and HMGal. Enzymatic assays in vitro and immunoblot analyses have revealed calpain- and calpastatin-like proteins in CHO cells. The activities and the amount of these proteins do not change under conditions of enhanced degradation, indicating that the levels of these proteins are not subject to mevalonate regulation.
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PMID:Inhibition of degradation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase in vivo by cysteine protease inhibitors. 190 66

Macrophages actively internalize macromolecules into endosomal vesicles containing proteases. The plant toxin, ricin A chain delivered into this pathway by receptor-mediated endocytosis, was found to be exquisitely sensitive to cleavage by these proteases. Proteolytic fragments of ricin A chain were generated within cells as early as 2-3 min after internalization. Toxin proteolysis was initiated in early endosomal vesicles, and transport to lysosomes was not required. As endosomes transit the cell, their lumenal pH drops from neutral to acidic. Previous studies in macrophages had suggested that endosomal proteolysis is dependent on vesicle acidification. Isolated endosomal vesicles containing ricin A chain catalyzed the cleavage of this protein in vitro; however, proteolysis was observed at both neutral and acidic pH. Experiments using isolated endosomes demonstrated that both cysteine and aspartyl proteases were responsible for the cleavage of ricin A chain. The cysteine protease, cathepsin B, catalyzed toxin proteolysis in endosomes between pH 4.5 and 7.0 while aspartyl protease activity was maximal below pH 5.5. Radiolabeling the lumenal contents of macrophage endosomes confirmed that both the cysteine protease, cathepsin B, and the aspartyl protease, cathepsin D, were present in these vesicles. These proteases were not present on the plasma membrane but were found in early endosomes indicating they are derived from an intracellular source. The presence of proteases with different pH optima in early endosomes suggests that processing in these vesicles may be regulated by changes in endosomal pH. This result represents an important difference in protein processing in endosomes versus lysosomes and provides new insights into the function of endosomal proteases.
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PMID:Proteolytic cleavage of ricin A chain in endosomal vesicles. Evidence for the action of endosomal proteases at both neutral and acidic pH. 193 30

To examine the effects of cysteine protease inhibitors on cathepsin D intracellular transport, proteolytic processing, and secretion, primary cultures of rabbit cardiac fibroblasts were grown to confluence and exposed (24 h) to media containing leupeptin (0-10 mM), E 64 (0-10 mM), or chloroquine (0-50 microM). Cathepsin D maturation was then evaluated in pulse-chase biosynthetic labeling experiments. None of the three agents affected the charge modification of procathepsin D (Mr 53,000) within the Golgi apparatus. However, all three agents interfered with the subsequent proteolytic processing of procathepsin D isoforms to active cathepsin D (Mr 48,000). Both leupeptin and E 64 caused the intracellular accumulation of large amounts of a Mr 51,000 processing intermediate (not detectable in control fibroblasts). Trace amounts of this intermediate were also detected in chloroquine-treated cells. Combined activity assay and radioimmunoassay of cell lysates indicated that this partially processed form of cathepsin D possessed proteolytic activity. Whereas low medium concentrations of leupeptin (10-100 microM) but not E 64 appeared to stimulate procathepsin D secretion, neither agent appeared to have a major effect on the rate of proenzyme secretion at doses required to inhibit proteolytic maturation (1-10 mM). Furthermore, pretreatment of cells with 10 mM leupeptin appeared only to delay, but not prevent, the intracellular transport of cathepsin D to lysosomes. In contrast, chloroquine increased procathepsin D secretion in a dose-dependent manner, diverting the majority of newly synthesized procathepsin D from the intracellular protease(s) responsible for proteolytic processing. These results suggest that cysteine proteases participate in the proteolytic maturation of procathepsin D during the transport of newly synthesized enzyme to lysosomes, but cysteine protease-mediated proteolytic processing is not required for cathepsin D activation or lysosomal translocation.
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PMID:Effects of cysteine protease inhibitors on rabbit cathepsin D maturation. 261 Feb 47

Acute muscle necrosis was induced in rats by intramuscular injection of plasmocid, a known myotoxic agent. A single injection of 5 mg/ml plasmocid produced massive fiber necrosis with extensive phagocytosis. Plasmocid administration led to a preferential decrease of alpha-actinin with preservation of other structural proteins within 3 h after injection, and large increases (2-7-fold) in the activities of acid hydrolases, cathepsins B and L, cathepsin D and alpha-galactosidase within 48 h after injection. The plasmocid-induced stimulation of alpha-actinin loss seen at 3 h, when no increases of acid hydrolases occurred, could be inhibited by a cysteine protease inhibitor, Ep-475 (E-64-c), and EGTA. On the other hand, increased lysosomal enzyme activity seemed to have a close correlation with the appearance of invading mononuclear cells, probably macrophages, and not muscle lysosomes. These observations suggest that a two step mechanism of protein degradation (nonlysosomal and lysosomal processes) possibly occurs in plasmocid-induced muscle degradation and macrophages can serve as a main endogenous reservoir of proteases in pathological states.
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PMID:Two-step mechanism of myofibrillar protein degradation in acute plasmocid-induced muscle necrosis. 642 26

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

The biosyntheses, processing, and intracellular transport of lysosomal APase were studied using pulse-chase experiments with primary cultured rat hepatocytes and subcellular fractionation techniques of rat liver after pulse-labeling with [35S] methionine in vivo. Apase was transported as a membrane-bound enzyme from the site of synthesis in the ER through the Golgi complex to lysosomes. Unlike many lysosomal enzymes which are translocated into lysosomes through the mediation of the Man-6-P receptors, transport of APase to lysosomes was independent of the Man-6-P receptor system. The transport of APase to lysosomes is dependent on the GY-motif which is located in its cytoplasmic domain. Kinetic experiments combined with subcellular fractionation of rat liver showed that after reaching the lysosomes, the membrane-bound APase (67 kDa) is subsequently released into the lysosomal matrix in the 64 kDa form, which is further processed via the 55 kDa form to the 48 kDa one, the major form of APase in rat liver lysosomal content. Our data from the in vitro experiments further showed that APase is released from lysosomal membranes into the lysosomal matrix by cathepsin D in the 65 kDa form, with release of a 1 kDa peptide, following which the released enzyme is further processed to the 64 kDa form, probably by lysosomal cysteine protease.
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PMID:[Biosynthesis, processing, and lysosome targeting of acid phosphatase]. 857 32

Antigen-presenting cells (APC) degrade endocytosed antigens into peptides that are bound and presented to T cells by major histocompatibility complex (MHC) class II molecules. Class II molecules are delivered to endocytic compartments by the class II accessory molecule invariant chain (Ii), which itself must be eliminated to allow peptide binding. The cellular location of Ii degradation, as well as the enzymology of this event, are important in determining the sets of antigenic peptides that will bind to class II molecules. Here, we show that the cysteine protease cathepsin S acts in a concerted fashion with other cysteine and noncysteine proteases to degrade mouse Ii in a stepwise fashion. Inactivation of cysteine proteases results in incomplete degradation of Ii, but the extent to which peptide loading is blocked by such treatment varies widely among MHC class II allelic products. These observations suggest that, first, class II molecules associated with larger Ii remnants can be converted efficiently to class II-peptide complexes and, second, that most class II-associated peptides can still be generated in cells treated with inhibitors of cysteine proteases. Surprisingly, maturation of MHC class II in mice deficient in cathepsin D is unaffected, showing that this major aspartyl protease is not involved in degradation of Ii or in generation of the bulk of antigenic peptides.
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PMID:Degradation of mouse invariant chain: roles of cathepsins S and D and the influence of major histocompatibility complex polymorphism. 925 53

Deterioration of the aortic wall resulting in formation of aneurysms may be caused by increased activity of metalloproteases and lysosomal proteases. The aim of this work was the evaluation of cathepsin D and cathepsin L activities, and activities of inhibitors of cysteine cathepsins in the wall of aortic aneurysms and in parietal thrombus. Aortic aneurysms were obtained during operation. Aortas taken from organ donors and blood clots were used as control material. Activities of cathepsin D and cathepsin L in the aortic aneurysm wall and parietal thrombus were higher than in the control groups. The aneurysm wall showed lower activity of inhibitors of cysteine proteases than the normal aorta. Parietal thrombus had a higher level of cysteine protease inhibitor activity than blood clot. Cathepsin D and cathepsin L present in the aneurysm wall and in the parietal thrombus filling the aneurysm may act on proteins determining elasticity and mechanical resistance of arteries.
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PMID:Cathepsin D and cathepsin L activities in aortic aneurysm wall and parietal thrombus. 974 68


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