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

---

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

We have investigated the distribution of newly synthesized lysosomal enzymes in endocytic compartments of normal rat kidney (NRK) cells. The mannose-6-phosphate (Man6-P) containing lysosomal enzymes could be iodinated in situ after internalization of lactoperoxidase (LPO) by fluid phase endocytosis and isolated on CI-MPR affinity columns. For EM studies, the ectodomain of the CI-MPR conjugated to colloidal gold was used as a probe specific for the phosphomannosyl marker of the newly synthesized hydrolases. In NRK cells, approximately 20-40% of the phosphorylated hydrolases present in the entire pathway were found in early endocytic structures proximal to the 18 degrees C temperature block including early endosomes. These structures were characterized by a low content of endogenous CI-MPR and were accessible to fluid phase markers internalized for 5-15 min at 37 degrees C. The bulk of the phosphorylated lysosomal enzymes was found in late endocytic structures distal to the 18 degrees C block, rich in endogenous CI-MPR and accessible to endocytic markers internalized for 30-60 min at 37 degrees C. The CI-MPR negative lysosomes were devoid of phosphorylated hydrolases. This distribution was unchanged in cells treated with Man6-P to block recapture of secreted lysosomal enzymes. However, lysosomal enzymes were no longer detected in the early endosomal elements of cells treated with cycloheximide. Immunoprecipitation of cathepsin D from early endosomes of pulse-labeled cells showed that this hydrolase is a transient component of this compartment. These data indicate that in NRK cells, the earliest point of convergence of the lysosomal biosynthetic and the endocytic pathways is the early endosome.
...
PMID:Distribution of newly synthesized lysosomal enzymes in the endocytic pathway of normal rat kidney cells. 166 30

The initial steps of proteolytic processing of newly synthesized cathepsin D were investigated in prelysosomal membranes, which were defined by their contents of 300 kDa mannose 6-phosphate receptor (MPR 300). MPR 300-containing vesicles were immuno-isolated from a postmitochondrial supernatant of HepG2 cells using a peptide-specific antibody directed against the 15 C-terminal amino acids of the cytoplasmic domain of MPR 300. In the immunoisolated fraction, MPR 300 was enriched 11.5-fold over [35S]polypeptides, 29-fold over the lysosomal marker beta-hexosaminidase and 4.5-fold over the trans Golgi marker galactosyltransferase, when referred to the postmitochondrial supernatant. MPR 300-containing vesicles harbored, on average, 12% of the cathepsin D precursor from the postmitochondrial supernatant, suggesting that segregation of MPR 300 and cathepsin D occurs rapidly in prelysosomal organelles. Detection of low, but significant amount of mature cathepsin D in the immunoisolated fraction suggests that proteolytic processing is initiated in MPR 300-containing vesicles or in tightly associated prelysosomal vesicles, which are distinct from mature lysosomes.
...
PMID:Proteolytic processing of cathepsin D in prelysosomal organelles. 795 14

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 GGAs (Golgi-localizing, gamma-adaptin ear homology domain, ARF-binding) are a multidomain family of proteins implicated in protein trafficking between the Golgi and endosomes. Recent evidence has established that the cation-independent (CI) and cation-dependent (CD) mannose 6-phosphate receptors (MPRs) bind specifically to the VHS domains of the GGAs through acidic cluster-dileucine motifs at the carboxyl ends of their cytoplasmic tails. However, the CD-MPR binds the VHS domains more weakly than the CI-MPR. Alignment of the C-terminal residues of the two receptors revealed a number of non-conservative differences in the acidic cluster-dileucine motifs and the flanking residues. Mutation of these residues in the CD-MPR cytoplasmic tail to the corresponding residues in the CI-MPR conferred either full binding (H63D mutant), intermediate binding (R60S), or unchanged binding (E56F/S57H) to the GGAs as determined by in vitro glutathione S-transferase pull-down assays. Furthermore, the C-terminal methionine of the CD-MPR, but not the C-terminal valine of the CI-MPR, inhibited GGA binding. Addition of four alanines to the C-terminal valine of the CI-MPR also severely reduced GGA binding, demonstrating the importance of the spacing of the acidic cluster-dileucine motif relative to the C terminus for optimal GGA interaction. Mouse L cells stably expressing CD-MPRs with mutations that enhance GGA binding sorted cathepsin D more efficiently than wild-type CD-MPR. These studies provide an explanation for the observed differences in the relative affinities of the two MPRs for the GGA proteins. Furthermore, they indicate that the GGAs participate in lysosomal enzyme sorting mediated by the CD-MPR.
...
PMID:Interaction of the cation-dependent mannose 6-phosphate receptor with GGA proteins. 1188 74

General intelligence is a heritable trait that is a risk factor for both the onset of dementia and the rate of cognitive decline in community-dwelling older persons. Previous studies screening for quantitative trait loci (QTLs) that influence general intelligence in healthy individuals have identified four loci, two of which are located within the genes insulin-like growth factor 2 receptor (IGF2R) and the Msx1 homeobox. Here, we report the finding of another QTL associated with general intelligence that is located within exon 2 of the cathepsin D (CTSD) gene. A group of 767 healthy adults with a follow-up period of over 15 years have been analyzed for cross-sectional and longitudinal trends in cognitive change using the Heim intelligence test score (AH4-1). We observed a significant association (P = 0.01) between a functional C > T (Ala > Val) transition within exon 2 of the CTSD gene that increases the secretion of pro-CTSD from the cell, and the AH4-1 score at initial testing on entry to the longitudinal study. Interestingly, CTSD is transported by IGF2R from the trans Golgi network to the lysosome.
...
PMID:Cathepsin D exon 2 polymorphism associated with general intelligence in a healthy older population. 1255 98

It has been reported that an accumulation of cholesterol within late endosomes/lysosomes in Niemann-Pick type C (NPC) fibroblasts and U18666A-treated cells causes impairment of retrograde trafficking of the cation-independent mannose 6-phosphate/IGF-II receptor (MPR300) from late endosomes to the trans-Golgi network (TGN). In apparent conflict with these results, here we show that as in normal fibroblasts, MPR300 localizes exclusively to the TGN in NPC fibroblasts as well as in normal fibroblasts treated with U18666A. This localization can explain why several lysosomal properties and functions, such as intracellular lysosomal enzyme activity and localization, the biosynthesis of cathepsin D, and protein degradation, are all normal in NPC fibroblasts. These results, therefore, suggest that the accumulation of cholesterol in late endosomes/lysosomes does not affect the retrieval of MPR300 from endosomes to the TGN. Furthermore, treatment of normal and NPC fibroblasts with chloroquine, which inhibits membrane traffic from early endosomes to the TGN, resulted in a redistribution of MPR300 to EEA1 and internalized transferrin-positive, but LAMP-2-negative, early-recycling endosomes. We propose that in normal and NPC fibroblasts, MPR300 is exclusively targeted from the TGN to early endosomes, from where it rapidly recycles back to the TGN without being delivered to late endosomes. This notion provides important insights into the definition of late endosomes, as well as the biogenesis of lysosomes.
...
PMID:Distribution and trafficking of MPR300 is normal in cells with cholesterol accumulated in late endocytic compartments: evidence for early endosome-to-TGN trafficking of MPR300. 1286 41

Aberrant secretion of lysosomal hydrolases such as (pro)cathepsin D (proCD) is a common phenotypic change in many human cancers. Here we explore the underlying molecular defect(s) and find that MCF-7 breast and CaCo-2 colorectal cancer cells that are unable to acidify their endosomal compartments secreted higher amounts of proCD than did acidification-competent cancer cell types. The latter secreted equivalent amounts of proCD only after dissipation of their organellar pH gradients with NH(4)Cl. Assessing the critical steps that resulted in proCD secretion revealed that the Golgi-associated sorting receptor for CD, i.e. the cation-independent mannose-6-phosphate receptor (MPR300), was aberrantly distributed in acidification-defective MCF-7 cells. It accumulated mainly in late endosomes and/or lysosomes as a complex with its ligand (proCD or intermediate CD), as evidenced by its co-localization with both CD and LAMP-2, a late endosome/lysosome marker. Our immunoprecipitation analyses also showed that MCF-7 cells possessed 7-fold higher levels of receptor-enzyme complexes than did acidification-competent cells. NH(4)Cl induced similar receptor redistribution into LAMP-2-positive structures in acidification-competent cells but not in MCF-7 cells. The receptor also recovered its normal Golgi localization upon drug removal. Based on these observations, we conclude that defective acidification results in the aberrant secretion of proCD in certain cancer cells and interferes mainly with the normal disassembly of the receptor-enzyme complexes and efficient receptor reutilization in the Golgi.
...
PMID:Defective acidification of intracellular organelles results in aberrant secretion of cathepsin D in cancer cells. 1525 39

Most mammalian cells contain two types of mannose 6-phosphate (Man-6-P) receptors (MPRs): the 300 kDa cation-independent (CI) MPR and 46 kDa cation-dependent (CD) MPR. The two MPRs have overlapping function in intracellular targeting of newly synthesized lysosomal proteins, but both are required for efficient targeting. Despite extensive investigation, the relative roles and specialized functions of each MPR in targeting of specific proteins remain questions of fundamental interest. One possibility is that most Man-6-P glycoproteins are transported by both MPRs, but there may be subsets that are preferentially transported by each. To investigate this, we have conducted a proteomics analysis of serum from mice lacking either MPR with the reasoning that lysosomal proteins that are selectively transported by a given MPR should be preferentially secreted into the bloodstream in its absence. We purified and identified Man-6-P glycoproteins and glycopeptides from wild-type, CDMPR-deficient, and CIMPR-deficient mouse serum and found both lysosomal proteins and proteins not currently thought to have lysosomal function. Different mass spectrometric approaches (spectral count analysis of nanospray LC-MS/MS experiments on unlabeled samples and LC-MALDI/TOF/TOF experiments on iTRAQ-labeled samples) revealed a number of proteins that appear specifically elevated in serum from each MPR-deficient mouse. Man-6-P glycoforms of cellular repressor of E1A-stimulated genes 1, tripeptidyl peptidase I, and heparanase were elevated in absence of the CDMPR and Man-6-P glycoforms of alpha-mannosidase B1, cathepsin D, and prosaposin were elevated in the absence of the CIMPR. Results were confirmed by Western blot analyses for select proteins. This study provides a comparison of different quantitative mass spectrometric approaches and provides the first report of proteins whose cellular targeting appears to be MPR-selective under physiological conditions.
...
PMID:Proteomics analysis of serum from mutant mice reveals lysosomal proteins selectively transported by each of the two mannose 6-phosphate receptors. 1784 85

Clathrin-coated vesicles (CCVs) are major carriers for endocytic cargo and mediate important intracellular trafficking events at the trans-Golgi network (TGN) and endosomes. Whereas clathrin heavy chain provides the structural backbone of the clathrin coat, the role of clathrin light chains (CLCs) is poorly understood. We now demonstrate that CLCs are not required for clathrin-mediated endocytosis but are critical for clathrin-mediated trafficking between the TGN and the endosomal system. Specifically, CLC knockdown (KD) causes the cation-independent mannose-6 phosphate receptor (CI-MPR) to cluster near the TGN leading to a delay in processing of the lysosomal hydrolase cathepsin D. A recently identified binding partner for CLCs is huntingtin-interacting protein 1-related (HIP1R), which is required for productive interactions of CCVs with the actin cytoskeleton. CLC KD causes mislocalization of HIP1R and overassembly of actin, which accumulates in patches around the clustered CI-MPR. A dominant-negative CLC construct that disrupts HIP1R/CLC interactions causes similar alterations in CI-MPR trafficking and actin assembly. Thus, in mammalian cells CLCs function in intracellular membrane trafficking by acting as recruitment proteins for HIP1R, enabling HIP1R to regulate actin assembly on clathrin-coated structures.
...
PMID:Clathrin light chains function in mannose phosphate receptor trafficking via regulation of actin assembly. 1816 18

The multifunctional growth factor mannose-6-phosphate/insulin-like growth factor 2 receptor (M6P/IGF2-R) binds proteins sharing M6P signals, including cathepsins and IGF2. It is involved in targeting newly synthesized mannose-6-phosphorylated lysosomal enzymes, activating transforming growth factor beta (TGFbeta), and neutralising the mitogen IGF2 by transporting it to lysosomes. The M6P/IGF2-R was proposed as being coded by a tumor suppressor gene. We measured gene expression at the protein level by quantitative immunohistochemistry, using chicken high affinity IgY antibodies directed against human M6P/IGF2-R. Chicken immunization was performed with human purified M6P/IGF2-R, and IgY antibodies were extracted from egg yolk by polyethylene glycol precipitation method. The biosensor analysis showed that IgY antibodies bind M6P/IGF2-R with high affinity (Kd = 7.5 nM). Quantitative immunohistochemical studies in sections from invasive breast carcinoma and ductal carcinoma in situ (DCIS) indicated various levels (from 5 to 400 units) of the M6P/IGF2-R protein, which did not correlate with tumor size, histological grade, estrogen and progesterone receptors. Moreover, the M6P/IGF2-R level was increased in DCIS relative to adjacent normal tissue (p < 0.005) and then decreased in invasive carcinoma compared with DCIS (p < 0.02). The hypothesis of tumor suppressor gene is not supported by these studies. However, it is not excluded for a small proportion of the tumors. Its assay might help to complement the cathepsin D assay to predict breast cancer prognosis and physiopathology.
...
PMID:Is the mannose-6-phosphate/insulin-like growth factor 2 receptor coded by a breast cancer suppressor gene? 1849 53


1 2 Next >>

---