Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.23.5 (cathepsin D)
 4,130 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of curcumin on lysosomal hydrolases in serum and heart was studied by determining the activities of beta-glucuronidase, beta-N-acetylglucosaminidase, cathepsin B, cathepsin D, and acid phosphatase. Rats treated with isoproterenol (30 mg/100 g body weight) showed a significant increase in serum lysosomal hydrolase activities, which were found to decrease after curcumin treatment. Isoproterenol administration to rats resulted in decreased stability of the membranes, which was reflected by the lowered activity of cathepsin D in mitochondrial, lysosomal, and microsomal fractions. Curcumin treatment returned the activity levels almost to normal, showing that curcumin restored the normal function of the membrane. Histopathological studies of the infarcted rat heart also showed a decreased degree of necrosis after curcumin treatment.
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PMID:Effect of curcumin on certain lysosomal hydrolases in isoproterenol-induced myocardial infarction in rats. 853 67

The lysosomal hydrolases, cathepsin D (Cat D) and beta-hexosaminidase A (HEX), which are normally intracellular enzymes, colocalize with beta-amyloid in a subgroup of diffuse plaques in the cerebellum and striatum of individuals with Alzheimer's disease or Down's syndrome. Using specific antisera in combination with single- and double-label immunocytochemical techniques, extracellular hydrolase was detected in 30 to 40% of the diffuse plaques in the cerebellar molecular layer and nearly all of the diffuse plaques in the striatum. In both Alzheimer's disease and Down's syndrome, about 5 to 10% of the cerebellar Purkinje cells contained abnormally increased numbers of hydrolase-positive lysosomes despite their normal appearance by conventional histologic stains. Occasional atrophic Purkinje cells identified by Nissl stain were intensely immunostained. By confocal imaging analysis, abnormal hydrolase-laden Purkinje cell dendrites were seen coursing through some hydrolase-positive plaques and were continuous with dendritic branches that terminated within deposits of extracellular hydrolase and beta-amyloid. In the striatum, intensely immunostained abnormal-appearing neurons were commonly associated with extracellular deposits of hydrolase immunoreactivity and beta-amyloid within diffuse plaques and in the less commonly seen classical plaques. In both brain regions, other hydrolase-negative beta-amyloid deposits were seen, these being associated with blood vessels. The presence of HEX immunoreactivity in neurons, but not in glia, and its abundance in plaques support earlier studies, suggesting that neurons are the principal source of plaque hydrolase. An endosomal-lysosomal system upregulation, with increased hydrolase expression and extracellular enzyme deposition in plaques, is, like beta-amyloid deposition, an early marker of metabolic dysfunction potentially related to primary etiologic events in Alzheimer's disease and Down's syndrome.
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PMID:Colocalization of lysosomal hydrolase and beta-amyloid in diffuse plaques of the cerebellum and striatum in Alzheimer's disease and Down's syndrome. 864 96

MHC class II molecules associate with peptides in the endocytic pathway. Different endosomal locations for peptide loading of class II molecules, varying from early endosomes (EE) to lysosomes, have been assigned on the basis of subcellular fractionation experiments. We have determined the intracellular location of HLA-DM, a molecule that supports peptide loading of class II molecules, by separating vesicles from the melanoma cell line Mel JuSo on the basis of buoying density and surface charge. In both fractionations, HLA-DM co-fractionated with a lysosomal compartment containing beta-hexosaminidase (beta-hex) activity and not with endosomes. Further analysis showed that HLA-DM mainly co-fractionated with a sub-lysosomal structure characterized by a relative low density and containing both pro- and mature cathepsin D and MHC class II molecules. Fluid phase markers first enter this compartment before entering high-density lysosomes that contain exclusively mature cathepsin D, some HLA-DM and no detectable MC class II molecules. Finally we determined the intracellular location of neutral and acidic peptidases. Whereas neutral peptidase activity was detected in the endoplasmic reticulum and/or plasma membrane fractions, acidic peptidase activity exclusively migrated at the position of HLA-DM containing lysosomal vesicles. Our results show that class II molecules co-migrate with HLA-DM, pro- and mature cathepsin D, beta-hex and acidic peptidase activity. HLA-DM, cathepsin d and class II molecules were not observed at the position of EE. Our data suggest that HLA-DM-mediated peptide loading of class II molecules occurs in a lysosomal subcompartment.
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PMID:HLA-DM and MHC class II molecules co-distribute with peptidase-containing lysosomal subcompartments. 867 50

Apical and narrow cells of the initial segment and intermediate zone of the adult rat epididymis were glutaraldehyde fixed and Epon embedded for routine light (LM) and electron (EM) microscopic analysis and Bouin fixed and paraffin embedded for LM immunocytochemical analysis in order to examine their structural features, distribution, and functions. The goblet-shaped apical cells comprised 10.7 +/- 1.0% of the total epithelial population in the proximal initial segment but only 1.3 +/- 0.5% in the intermediate zone. In the EM, these cells presented numerous mitochondria, few C-shaped vesicles, and a pale round or oblong nucleus located in the upper half of their cytoplasm. The slender elongated narrow cells increased from 2.8 +/- 0.3% in the proximal initial segment to 6.3 +/- 0.4% in the intermediate zone. In an EM analysis, these cells presented numerous C-shaped vesicles and mitochondria and a small flattened nucleus located in the upper half of their cytoplasm. The structural features of both these cell types differed not only from each other but also from the neighboring principal and basal cells of each region. Of the various antibodies examined to lysosomal proteins, narrow and apical cells expressed high levels of cathepsin D, while beta-hexosaminidase A was expressed at high levels in narrow cells but only moderately in apical cells. Apical cells were intensely reactive for the Yf subunit of glutathione S-transferase (GST)-P, whereas no reaction was seen in narrow cells; the Yo subunit of GST was localized within both cell types but only in the proximal initial segment. Narrow cells exclusively expressed carbonic anhydrase II. Selective differences in the immunolocalization of these various proteins were also noted between these two cell types and principal and basal cells. The localization of cathepsin D and beta-hexosaminidase A within narrow and apical cells suggests these cells may be involved in the degradation of specific proteins within their lysosomes, whereas the presence of GSTs may aid in protecting spermatozoa from a changing environment of harmful electrophiles. Localization of carbonic anhydrase II exclusively within narrow cells suggests that these cells may modify the pH of the lumen resulting in the quiescence of sperm motility in the proximal end of the epididymis. Together, the data indicate that apical and narrow cells differ not only from each other but also from principal and basal cells in their structure and relative distribution. They also express different proteins within the distinct epididymal regions, indicating that they perform different functions.
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PMID:Apical and narrow cells are distinct cell types differing in their structure, distribution, and functions in the adult rat epididymis. 879 11

The phenotype of autosomal dominant polycystic kidney disease (ADPKD) is characterized by basement membrane abnormalities, hyperproliferation, and alterations in epithelial cell polarity. Since proteinases have been implicated in matrix degradation and growth factor activation, lysosomal enzymes were compared in normal and ADPKD tissues and cell cultures. Acidic proteolytic activity (azocasein) was reduced in ADPKD, and specific enzymatic assays detected disease-dependent decreases in the specific activities of beta-galactosidase, beta-hexosaminidase, and cathepsins, B, L, and H. Cathepsin D-specific activities were unchanged. Lucifer yellow fluorescence in ADPKD cells was consistent with an alteration in heterogeneity of lysosomal enzyme content in ADPKD rather than a decrease in total lysosomal number. Western analysis, metabolic labeling, and immunoprecipitation analysis confirmed decreases in the expression and synthesis of the major normal molecular immunoreactive species of beta-galactosidase and cathepsins B and H in ADPKD tissue and cells but no changes in cathepsin D. In addition, ADPKD-specific high-molecular-weight species of cathepsin H were seen and abnormal forms of cathepsin B and beta-galactosidase were common in ADPKD, suggesting abnormal molecular processing and posttranslational modifications. In addition, immunolocalization studies showed abnormal apical plasma-membrane localization of cathepsins B and H in ADPKD cyst epithelial cells, consistent with a protein sorting defect in ADPKD. Increased extracellular secretion of lysosomal enzymes was also measured in ADPKD cultured cells and in filter-grown epithelia shown to be predominantly directed to the basal compartment. These results demonstrate that lysosomal enzyme alterations in ADPKD may play a role in aberrant processing of the basement membrane. Alterations in the polarized secretion of lysosomal enzymes by ADPKD epithelia in vitro were also detected. Whereas all normal epithelia cells secreted lysosomal enzymes predominantly to the apical medium compartments, basally directed secretion was increased in all ADPKD epithelia and attained an overall reversal of polarity for cathepsins B + L. It is concluded that alterations in lysosomal enzyme function in ADPKD are the result of alterations in synthesis, molecular processing, and polarized secretion of specific enzymes and may have impact on proliferative and basement membrane abnormalities in this genetic disease. These results are consistent with a fundamental defect in protein processing sorting, and trafficking in ADPKD.
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PMID:Functional defects in lysosomal enzymes in autosomal dominant polycystic kidney disease (ADPKD): abnormalities in synthesis, molecular processing, polarity, and secretion. 906 78

Lysosomes are considered to be a terminal degradative compartment of the endocytic pathway, into which transport is mostly unidirectional. However, specialized secretory vesicles regulated by Ca2+, such as neutrophil azurophil granules, mast cell-specific granules, and cytotoxic lymphocyte lytic granules, share characteristics with lysosomes that may reflect a common biogenesis. In addition, the involvement of Ca2+ transients in the invasion mechanism of the parasite Trypanosoma cruzi, which occurs by fusion of lysosomes with the plasma membrane, suggested that lysosome exocytosis might be a generalized process present in most cell types. Here we demonstrate that elevation in the intracellular free Ca2+ concentration of normal rat kidney (NRK) fibroblasts induces fusion of lysosomes with the plasma membrane. This was verified by measuring the release of the lysosomal enzyme beta-hexosaminidase, the appearance on the plasma membrane of the lysosomal glycoprotein lgp120, the release of fluid-phase tracers previously loaded into lysosomes, and the release of the lysosomally processed form of cathepsin D. Exposure to the Ca2+ ionophore ionomycin or addition of Ca2+-containing buffers to streptolysin O-permeabilized cells induced exocytosis of approximately 10% of the total lysosomes of NRK cells. The process was also detected in other cell types such as epithelial cells and myoblasts. Lysosomal exocytosis was found to require micromolar levels of Ca2+ and to be temperature and ATP dependent, similar to Ca2+-regulated secretory mechanisms in specialized cells. These findings highlight a novel role for lysosomes in cellular membrane traffic and suggest that fusion of lysosomes with the plasma membrane may be an ubiquitous form of Ca2+-regulated exocytosis.
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PMID:Lysosomes behave as Ca2+-regulated exocytic vesicles in fibroblasts and epithelial cells. 910 39

In the present work, we analyzed the variations in the expression and trafficking of cathepsin D (CD), a lysosomal endopeptidase, associated with the enterocytic differentiation of the human colon carcinoma HT-29 cell line. In spite of the fact that the abundance of CD mRNA was severalfold higher in undifferentiated HT-29 cells than in their enterocyte-like differentiated counterparts, the intracellular levels of CD activity and protein were found to be much higher in the latter. The kinetic of transport of newly synthesized proCD was different in the two cell populations: (a) full conversion of proCD into the lysosomal mature form required more than 24 h in differentiated cells, whereas it was almost complete within 8 h in undifferentiated HT-29 cells; and (b) the extracellular release of proCD was shown to occur more rapidly and to a higher degree in undifferentiated than in differentiated cells. Most of the secreted proCD contained phosphomannoses. Secretion of beta-hexosaminidase activity doubled, whereas that of CD activity was unchanged, upon vacuolar alkalinization with ammonium chloride or chloroquine. Inhibition of the lysosomal-autophagic degradative pathway resulted in the accumulation of proCD molecules in undifferentiated HT-29 cells. Altogether these data suggest that: (a) the expression and the posttranslational fate of CD in HT-29 colon cancer cells are largely affected by the state of their enterocytic differentiation; and (b) in this cell line the acid-dependent mannose 6-phosphate receptor pathway is, at best, little involved in the trafficking of CD.
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PMID:Expression and posttranslational fate of cathepsin D in HT-29 tumor cells depend on their enterocytic differentiation state. 930 Jan 84

Thyrocytes are known for their ability to iodinate thyroglobulin from which the thyroid hormones are generated. In the intact thyroid gland the iodination process is almost exclusively executed at the apical plasma membrane of thyroid epithelial cells. Here, we show that freshly isolated thyrocytes iodinated polypeptides other than thyroglobulin and that one of the major iodinated polypeptides was the mature form of the lysosomal protease cathepsin D (CD). The detection of mature CD as an iodinated polypeptide suggested that a fraction of the lysosomally maturated enzyme was delivered to the apical plasma membrane where it became available for iodination. After labeling of thyrocytes with [35S]methionine/cysteine overnight part of the mature CD was released into the culture medium. This was abolished by inhibiting maturation of CD with NH4Cl, indicating that mature CD appeared in the medium after its proteolytic maturation in an acidic compartment. Besides CD other soluble lysosomal polypeptides like the beta-N-acetylhexosaminidase and the sphingolipid-activating protein D (Sap D) were iodinated and partially secreted as mature polypeptides. In contrast, the membrane-associated lysosomal ceramidase was iodinated and partially secreted as immature single-chain enzyme and not as fully maturated two-chain enzyme. These data indicate that a portion of mature CD and other soluble lysosomal enzymes is delivered from lysosomes to the cell surface whereas some membrane-associated enzymes from the terminal lysosomal compartment are efficiently excluded from this process.
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PMID:Iodination of mature cathepsin D in thyrocytes as an indicator for its transport to the cell surface. 965 Jul 83

Previous studies have implicated the failure to degrade aggregated Abeta1-42 in late endosomes or secondary lysosomes as a mechanism for the accumulation of beta-amyloid in Alzheimer's disease. We examined the consequences of intracellular accumulation of Abeta1-42 on the integrity of the endosomal/lysosomal compartment by monitoring Lucifer Yellow fluorescence and the release of lysosomal hydrolases into the soluble, cytosolic fraction. In control cells, the Lucifer Yellow fluorescence is observed as punctate staining in a perinuclear distribution with no apparent cytoplasmic fluorescence, consistent with its localization in late endosomes or secondary lysosomes. After incubation with Abeta1-42 for 6 hr, a loss of lysosomal membrane impermeability is observed as evidenced by redistribution of the fluorescence to a diffuse, cytoplasmic pattern. The loss of lysosomal membrane impermeability is correlated with Abeta1-42 accumulation, since incubation of the cells with the nonaccumulating isoform of amyloid, Abeta1-40, does not induce leakage. The same results were obtained using the release of soluble lysosomal hydrolases, cathepsin D and beta-hexosaminidase, into the cytosol as an assay for the leakage of lysosomal contents. Together, our results suggest that the loss of lysosomal membrane impermeability may be an early event in Abeta pathogenesis, and provide an explanation for the miscompartmentalization of extracellular and cytoplasmic components observed in Alzheimer's disease (AD). The release of hydrolases may further cause the breakdown of the cytoskeleton and the blebbing of the plasma membrane, and the leakage of heparan sulfate glycosaminoglycans from the lysosome may ultimately promote the assembly of tau into neurofibrillary tangles (NFT).
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PMID:Loss of endosomal/lysosomal membrane impermeability is an early event in amyloid Abeta1-42 pathogenesis. 966 18

The two mannose 6-phosphate (Man-6-P) binding sites of the insulin-like growth factor-II/mannose 6-phosphate receptor (IGF-II/MPR) have been localized to domains 1-3 and 7-9, and studies have shown that Arg435 in domain 3 and Arg 1334 in domain 9 are essential for Man-6-P binding. To determine whether the IGF-II/MPR containing a single Man-6-P binding site is functional, clonal mouse L cell lines stably transfected with either mutant bovine IGF-II/MPR cDNA, containing substitutions at position 435 and/or 1334, or the wild type receptor cDNA were assayed for their ability to sort lysosomal enzymes to the lysosome. Mutant receptors containing a single Man-6-P binding site were approximately 50% less efficient than the wild type receptor in the overall targeting of lysosomal enzymes to the lysosome. Mutant receptors containing a substitution at Arg1334 (Dom9(Ala)), in contrast to those containing a substitution at Arg435 (Dom3(Ala)), were unable to target cathepsin D and beta-hexosaminidase to the lysosome. Equilibrium binding assays using 125I-labeled beta-glucuronidase demonstrated that Dom3(Ala) and Dom9(Ala) had a Kd of 2.0 and 4.3 nM, respectively. In addition, Dom3(Ala), unlike Dom9(Ala), was unable to completely dissociate from ligand under acidic pH conditions. These data indicate that the two Man-6-P binding sites of the IGF-II/MPR are not functionally equivalent.
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PMID:The two mannose 6-phosphate binding sites of the insulin-like growth factor-II/mannose 6-phosphate receptor display different ligand binding properties. 971 56


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