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)

Various aspects of lysosome biogenesis have been studied in Chinese hamster ovary (CHO) cells of the End3 complementation group (designated G.7.1 cells), which display a temperature-sensitive defect in the acidification of endosomes, but not lysosomes. In G.7.1 and normal wild-type cells grown at the permissive temperature (34 degrees C), the lysosomal enzymes alpha-glucosidase and cathepsin D were synthesized as high-molecular-weight precursors that subsequently underwent intracellular proteolytic processing to yield lower molecular weight mature forms. The mature forms of the enzymes were retained in cells, and small amounts of each precursor were secreted. However, in G.7.1 cells grown at the restrictive temperature (41 degrees C), there was a massive and inappropriate oversecretion of lysosomal enzyme precursors, which resulted in very little of the mature forms being processed and retained by the cells. This mistargeting of lysosomal enzymes was not due to an absence of phosphorylated oligosaccharides on the enzymes, nor to a defect in mannose 6-phosphate (Man6P) receptors. However, it was found that whereas G.7.1 cells had the same number of cell surface Man6P receptors at 34 degrees C and 41 degrees C, the rate of accumulation and degradation of Man6P-containing ligands was about two to three times more rapid in cells maintained at the permissive temperature. There did not appear to be any gross changes in Golgi function as the oligosaccharides of alpha-glucosidase and the Man6P receptor were processed in a similar fashion at both 34 degrees C and 41 degrees C. In addition to these studies, electron microscopic observations revealed that at 41 degrees C, G.7.1 cells accumulated inclusion-type bodies reminiscent of those found in I-cell disease fibroblasts. Thus, the biochemical and electron microscopic results on G.7.1 cells provide further evidence that acidified endosomes are important for the biogenesis of lysosomes.
 ...
PMID:Biosynthesis of lysosomal enzymes in cells of the End3 complementation group conditionally defective in endosomal acidification. 184 19

Adler and Martin (1983, Curr. Eye Res. 2, 359-66) found cathepsin D to be present in crude preparations of bovine interphotoreceptor matrix (IPM). The purpose of the present study was to determine, by investigating several acid hydrolases in purer IPM samples, whether hydrolytic enzymes abundant in RPE lysosomes were present also as normal components of the IPM. IPM was prepared from bovine eyes by the introduction of a small bleb of buffer between the neural retina and the RPE. These IPM samples were free from significant contamination by surrounding tissues; they contained IRBP as their only major protein, and had negligible amounts of lactate dehydrogenase and ROS-specific proteins. Most acid hydrolases were assayed fluorometrically by measuring the 4-methylumbelliferone released upon hydrolysis of appropriate derivatives; the substrate for cathepsin was hemoglobin. The amounts of the enzymes found in the IPM were far from uniform and could not be correlated with enzyme activities in either RPE or retina homogenates. The hydrolases in the IPM varied in amount from beta-galactosidase (28% of the RPE level), through N-acetyl-beta-glucosaminidase (20%), alpha-fucosidase (15%), beta-glucuronidase (12%), alpha-glucosidase (8%), cathepsin D (7%), alpha-mannosidase (7%), down to beta-glucosidase, acid phosphatase, and acid lipase (trace amounts, less than 1%). These results agree with the relative amounts of enzymes found by Wilcox (1987) to be secreted into the medium by cultured human RPE cells. Furthermore, the rank order of hydrolases in the IPM is the same as that for hydrolases secreted (but not recaptured) by human fibroblasts in I-cell disease. The conclusion from these correlations is that lysosomal enzymes are probably secreted, as a normal process, by the RPE into the IPM, where they may have a role in digesting shed outer segments and in catabolizing IPM components.
 ...
PMID:Selective presence of acid hydrolases in the interphotoreceptor matrix. 261 85

The incorporation of [3H]leucine and [32P]phosphate into three lysosomal enzymes, cathepsin D, beta-hexosaminidase and arylsulfatase A by fibroblasts from six patients affected with mucolipidosis III was determined. In the mutant cells the incorporation of 32P in the enzymes was reduced by 70-97% as compared to controls. The residual phosphorylation of lysosomal enzymes is definitely higher than in fibroblasts from patients with mucolipidosis II, where apparently non-phosphorylated enzymes are formed. In mucolipidosis III the major part of the newly formed enzymes accumulated extracellularly and the cellular enzymes were recovered mainly in their processed forms. In mucolipidosis III arylsulfatase A and the processed forms of cathepsin D exhibited a heterogeneity that was not observed in controls. beta-Hexosaminidase and cathepsin D secreted by mucolipidosis III fibroblasts contained only a small amount of phosphorylated oligosaccharides with either one or two phosphate groups per oligosaccharide. As in controls the major fraction of phosphate was present as acid-labile phosphodiester resistant to alkaline phosphatase. The residual phosphorylation of lysosomal enzymes may be related to the partial intracellular retention and processing of these enzymes in fibroblasts from patients with mucolipidosis III.
 ...
PMID:Impaired phosphorylation of lysosomal enzymes in fibroblasts of patients with mucolipidosis III. 612 Aug 34

A procedure is described that allows the characterization of the molecular forms of beta-hexosaminidase and cathepsin D in controls and pathological specimens of human serum and human urine. The following observations were made. (1) In human serum, beta-hexosaminidase (alpha- and beta-chain) and cathepsin D are present predominantly in their high-molecular-weight precursor forms. In human urine, these enzymes exist as both precursor and mature forms. (2) Cathepsin D precursor from serum and urine differs in the number of oligosaccharides that are sensitive to endo-beta-N-acetylglucosaminidase H. Therefore the urine enzyme is not likely to originate from the serum. (3) The presence exclusively of precursors of beta-hexosaminidase and of cathepsin D in the sera of patients with hepatitis suggests that in hepatitis secretion of lysosomal enzymes is elevated, rather than the enzymes leaking from damaged cells. (4) In the urine of patients with nephrotic syndrome, beta-hexosaminidase and cathepsin D are present in grossly elevated amounts, but do not differ in the polypeptide patterns from controls. (5) In urine from a patient with mucolipidosis II, the elevated activity of beta-hexosaminidase is accounted for mainly by the precursor forms. Mature beta-chain of beta-hexosaminidase is lacking, and incompletely processed beta-hexosaminidase polypeptides are present. Both the precursor and the mature forms of cathepsin D are increased. They contain only complex oligosaccharides.
 ...
PMID:Molecular forms of beta-hexosaminidase and cathepsin D in serum and urine of healthy subjects and patients with elevated activity of lysosomal enzymes. 622 25

The distribution of the different types of oligosaccharides in cathepsin D and in beta-hexosaminidase synthesized in cultured human fibroblasts was studied by using endo-beta-N-acetylglucosaminidase H as a probe for high-mannose oligosaccharides. The enzymes were specifically labelled in the protein or the carbohydrate moiety. In both enzymes, resistant and cleavable oligosaccharides were found. The resistant oligosaccharides prevailed in the secreted enzymes. Precursor molecules of cathepsin D contained two oligosaccharide side chains. Multiple forms of the precursor are synthesized with both, one or none of two oligosaccharides sensitive to the action of the endo-beta-N-acetylglucosaminidase H. In fibroblasts unable to phosphorylate lysosomal enzymes (mucolipidosis II) the excessively secreted lysosomal enzymes contained predominantly oligosaccharides resistant to endo-beta-N-acetylglucosaminidase H.
 ...
PMID:Oligosaccharides in lysosomal enzymes. Distribution of high-mannose and complex oligosaccharides in cathepsin D and beta-hexosaminidase. 645 26

B lymphocytes from patients with I-cell disease (ICD) maintain normal cellular levels of lysosomal enzymes despite a deficiency of the enzyme UDP-N-acetylglucosamine: lysosomal enzyme N-acetylglucosamine-1-phosphotransferase. We find that an ICD B lymphoblastoid cell line targets about 45% of the lysosomal protease cathepsin D to dense lysosomes. This targeting occurs in the absence of detectable mannose 6-phosphate residues on the cathepsin D and is not observed in ICD fibroblasts. The secretory protein pepsinogen, which is closely related to cathepsin D in both amino acid sequence and three-dimensional structure, is mostly excluded from dense lysosomes, indicating that the lymphoblast targeting pathway is specific. Carbohydrate residues are not required for lysosomal targeting, since a non-glycosylated mutant cathepsin D is sorted with comparable efficiency to the wild type protein. Analysis of a number of cathepsin D/pepsinogen chimeric proteins indicates that an extensive polypeptide determinant in the cathepsin D carboxyl lobe can confer efficient lysosomal sorting when introduced into the pepsinogen sequence. This determinant overlaps but is not identical to the recognition marker for phosphotransferase. These results indicate that a specific protein recognition event underlies Man-6-P-independent lysosomal sorting in ICD lymphoblasts.
 ...
PMID:Mannose 6-phosphate-independent targeting of lysosomal enzymes in I-cell disease B lymphoblasts. 840 10

The localization and intracellular transport of major histocompatibility complex (MHC) class II molecules nd lysosomal hydrolases were studied in I-Cell Disease (ICD) B lymphoblasts, which possess a mannose 6-phosphate (Man-6-P)-independent targeting pathway for lysosomal enzymes. In the trans-Golgi network (TGN), MHC class II-invariant chain complexes colocalized with the lysosomal hydrolase cathepsin D in buds and vesicles that lacked markers of clathrin-coated vesicle-mediated transport. These vesicles fused with the endocytic pathway leading to the formation of "early" MHC class II-rich compartments (MIICs). Similar structures were observed in the TGN of normal beta lymphoblasts although they were less abundant. Metabolic labeling and subcellular fractionation experiments indicated that newly synthesized cathepsin D and MHC class II-invariant chain complexes enter a non-clathrin-coated vesicular structure after their passage through the TGN and segregation from the secretory pathway. These vesicles were also devoid of the cation-dependent mannose 6-phosphate (Man-6-P) receptor, a marker of early and late endosomes. These findings suggest that in ICD B lymphoblasts the majority of MHC class II molecules are transported directly from the TGN to "early" MIICs and that acid hydrolases cam be incorporated into MIICs simultaneously by a Man-6-P-independant process.
 ...
PMID:The biogenesis of the MHC class II compartment in human I-cell disease B lymphoblasts. 860 11

It has been reported that besides defects in the phosphorylation such as in the I-cell disease, a failure in the uncovering of mannose 6-phosphate residues may result in an increase of lysosomal enzyme activities in serum [Alexander et al., Hum. Genet. 73, 53-59 (1986)]. We examined fibroblasts that were derived from the original biopsy, observed an enhanced secretion of lysosomal enzymes including cathepsin D, but found that both the phosphorylation and uncovering of mannose 6-phosphate residues were normal. The enhanced secretion of cathepsin D was characterized by an increase in the secretion of phosphorylated molecules that were sensitive to a treatment with alkaline phosphatase. The enhanced secretion of the phosphatase-sensitive form of procathepsin D was further increased in the presence of antibodies directed to cation-independent mannose 6-phosphate receptors. In contrast, antibodies specific to cation-dependent mannose 6-phosphate receptors selectively inhibited the secretion of the phosphatase-sensitive procathepsin D molecules. A chromatographic analysis of oligosaccharides from the secreted procathepsin D confirmed that the cells secrete proenzyme molecules rich in oligosaccharides with two uncovered phosphate residues. It is suggested that the enhanced secretion of procathepsin D in the variant fibroblasts results from an abnormal sorting rather than processing of phosphorylated lysosomal enzymes.
 ...
PMID:Abnormal lysosomal sorting with an enhanced secretion of cathepsin D precursor molecules bearing monoester phosphate groups. 984 Apr 63

Viable mice nullizygous in genes encoding the 300 kDa and the 46 kDa mannose 6-phosphate receptors (MPR 300 and MPR 46) and the insulin like growth factor II (IGF II) were generated to study the trafficking of lysosomal enzymes in the absence of MPRs. The mice have an I-cell disease-like phenotype, with increase of lysosomal enzymes in serum and normal activities in tissues. Surprisingly, the ability of MPR-deficient cells to transport newly synthesized lysosomal enzymes to lysosomes and the underlying mechanisms were found to depend on the cell type. MPR-deficient thymocytes target newly synthesized cathepsin D to lysosomes via an intracellular route. In contrast, hepatocytes and fibroblasts secrete newly synthesized cathepsin D. In fibroblasts recapture of secreted lysosomal enzymes, including that of cathepsin D, is limited and results in lysosomal storage, both in vivo and in vitro, whereas recapture by hepatocytes is remarkably effective in vivo and can result in lysosomal enzyme levels even above normal.
 ...
PMID:Alternative mechanisms for trafficking of lysosomal enzymes in mannose 6-phosphate receptor-deficient mice are cell type-specific. 1021 52

The role of cathepsin D in stress-induced cell death has been investigated by using ovine fibroblasts exhibiting a missense mutation in the active site of cathepsin D. The cathepsin D (lysosomal aspartic protease) deficiency did not protect cells against toxicity induced by doxorubicin and other cytotoxic agents, neither did it protect cells from caspase activation. Moreover, the cathepsin D inhibitor, pepstatin A, did not prevent stress-induced cell death in human fibroblasts or lymphoblasts. The possible role of lysosomal ceramide or sphingosine-mediated activation of cathepsin D in apoptosis was also excluded by using human cells either overexpressing or deficient in acid ceramidase. However, a normal lysosomal function seems to be required for efficient cell death, as indicated by the finding that fibroblasts from patients with mucolipidosis II were partially resistant to staurosporine, sphingosine and TNF-induced apoptosis, suggesting a key role of lysosomes in cell death.
 ...
PMID:Stress-induced apoptosis is impaired in cells with a lysosomal targeting defect but is not affected in cells synthesizing a catalytically inactive cathepsin D. 1293 83


1 2 Next >>