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 transport of proteins from the secretory to the endocytic pathway is mediated by carrier vesicles coated with the AP-1 Golgi assembly proteins and clathrin. The mannose 6-phosphate receptors (MPHs) are two major transmembrane proteins segregated into these transport vesicles. Together with the GTPase ARF-1, these cargo proteins are essential components for the efficient translocation of the cytosolic AP-1 onto membranes of the trans-Golgi network, the first step of clathrin coat assembly, MPR-negative fibroblasts have a low capacity of recruiting AP-1 which can be restored by re-expressing the MPRs in these cells. This property was used to identify the protein motif of the cation-dependent mannose 6-phosphate receptor (CD-MPR) cytoplasmic domain that is essential for these interactions. Thus, the affinity of AP-1 for membranes and in vivo transport of cathepsin D were measured for MPR-negative cells re-expressing various CD-MPR mutants. The results indicate that the targeting of lysosomal enzymes requires the CD-PDR cytoplasmic domain that are different from tyrosine-based endocytosis motifs. The first is a casein kinase II phosphorylation site (ESEER) that is essential for high affinity binding of AP-1 and therefore probably acts as a dominant determinant controlling CD-MPR sorting in the trans-Golgi network. The second is the adjacent di-leucine motif (HLLPM), which, by itself, is not critical for AP-1 binding, but is absolutely required for a downstream sorting event.
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PMID:A casein kinase II phosphorylation site in the cytoplasmic domain of the cation-dependent mannose 6-phosphate receptor determines the high affinity interaction of the AP-1 Golgi assembly proteins with membranes. 856 75

The study of several human breast cancer cell lines containing oestrogen receptors has allowed characterization of a number of oestrogen-induced proteins (e.g. progesterone receptor, cathepsin D, pS2, Hsp27, c-Myc). In primary tumours these markers have different prognostic significance for predicting whether the tumour will be hormone responsive (e.g. pS2, progesterone receptor) and whether it will metastasize (e.g. cathepsin D). The mechanism of regulation of gene expression by oestrogens and anti-oestrogens in breast cancer is complex and varies according to the nature of both the gene and the cell in which it is transcribed. Our laboratory has identified the sequences mediating oestrogen activity in the proximal region of cathepsin D, including a non-consensus oestrogen-responsive element located at -260 which acts in synergy with other regulatory elements. In addition to the classical effect of oestrogen receptor in stimulating transcription of genes controlled by the oestrogen-responsive element, we found that estrogen receptor is able to modulate transcription of AP-1-responsive genes without interacting directly with DNA. Cross-talk between oestrogen receptor and members of the Fos/Jun family via protein-protein interactions may explain how anti-oestrogens inhibit the mitogenic effect of growth factors in the apparent absence of oestrogens and why tamoxifen is able to stimulate cathepsin D gene expression and induce apoptosis in certain oestrogen receptor-positive breast cancer cells. The nature and degree of this cross-talk appears to vary according to the gene, the cell type and the type of oestrogen receptor ligand involved. Studies of oestrogen-regulated genes are not only useful for classifying breast cancers according to their ability to metastasize and respond to therapies, but also should lead to new therapeutic approaches for hormone-dependent and hormone-resistant cancers.
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PMID:Oestrogen- and anti-oestrogen-regulated genes in human breast cancer. 858 2

After uptake by murine macrophages, Salmonella typhimurium is able to survive and replicate within specialized phagosomes called Salmonella-containing vacuoles (SCVs), which are segregated from the late endocytic pathway. The molecular basis of this process and the virulence factors required are not fully understood. In this study, we used confocal fluorescence microscopy to evaluate interactions between the endocytic pathway of the murine macrophage cell line RAW 264.7 and different S. typhimurium strains. The analysis was carried out using the fluid-phase marker Texas red-ovalbumin and antibodies against the lysosomal enzyme cathepsin D, the late endosomal lipid lysobisphosphatidic acid and the adaptor proteins AP-1 and AP-3. Less than 10% of wild-type SCVs were associated with these markers at 24 h after uptake by macrophages. A similar low level of association was observed for vacuoles containing mutant strains affected in the function of the Salmonella pathogenicity island (SPI)-2 type III secretion system or the virulence plasmid spv operon. However, at this time point, the proportion of vacuoles containing phoP-mutant bacteria that were associated with each of the markers ranged from 25% to 50%. These results show that the regulon controlled by the PhoP/Q two-component system makes a major contribution to trafficking of the SCV in macrophages. Segregation of SCVs from the endocytic pathway was also found to be dependent on bacterial proteins synthesized between 15 min and 4 h after uptake into macrophages. However, after this time, protein synthesis was not required to maintain the segregation of SCVs from late endosomes and lysosomes.
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PMID:A role for the PhoP/Q regulon in inhibition of fusion between lysosomes and Salmonella-containing vacuoles in macrophages. 1169 33

We have used GST pulldowns from A431 cell cytosol to identify three new binding partners for the gamma-adaptin appendage: Snx9, ARF GAP1, and a novel ENTH domain-containing protein, epsinR. EpsinR is a highly conserved protein that colocalizes with AP-1 and is enriched in purified clathrin-coated vesicles. However, it does not require AP-1 to get onto membranes and remains membrane-associated in AP-1-deficient cells. Moreover, although epsinR binds AP-1 via its COOH-terminal domain, its NH(2)-terminal ENTH domain can be independently recruited onto membranes, both in vivo and in vitro. Brefeldin A causes epsinR to redistribute into the cytosol, and recruitment of the ENTH domain requires GTPgammaS, indicating that membrane association is ARF dependent. In protein-lipid overlay assays, the epsinR ENTH domain binds to PtdIns(4)P, suggesting a possible mechanism for ARF-dependent recruitment onto TGN membranes. When epsinR is depleted from cells by RNAi, cathepsin D is still correctly processed intracellularly to the mature form. This indicates that although epsinR is likely to be an important component of the AP-1 network, it is not necessary for the sorting of lysosomal enzymes.
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PMID:EpsinR: an ENTH domain-containing protein that interacts with AP-1. 1258 59

We have cloned a 969-bp fragment of genomic DNA that spans 821 bp of the 5' untranslated region, exon 1, a short intron, and part of exon 2 of the Schistosoma mansoni cathepsin D gene by inverse PCR. Inspection of this sequence revealed the presence of two TATA-box motifs, two inverted CCAAT-box (inverted NF-Y) motifs and sequences with homology to binding sites for the transcription factors, AP-1 and NF-Y. This sequence and deletion variants were cloned into reporter gene constructs, in order to examine the ability of these putative regulatory sequences to drive heterologous reporter gene activity. PCR products were cloned into the luciferase reporter vector pXP2. These reporter gene constructs were used to transform HeLa cells which were cultured and examined for luciferase activity. Additionally, HeLa cells transiently transfected with an EGFP reporter plasmid driven by the putative promoter from the S. mansoni cathepsin D gene were examined for EGFP transcripts and fluorescence. The 5' untranslated region of the S. mansoni cathepsin D gene, from position -772 to +40 (translation start ATG), included functional regulatory sequences capable of driving luciferase and EGFP expression, whereas shorter fragments from position -264 or -185 to +40 were insufficient to drive reporter activities.
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PMID:Organization and functional analysis of the Schistosoma mansoni cathepsin D-like aspartic protease gene promoter. 1565 55

Aftiphilin is a protein that was recently identified in database searches for proteins with motifs that interact with AP-1 and clathrin, but its function is unknown. Here we demonstrate that aftiphilin has a second, atypical clathrin binding site, YQW, that colocalizes with AP-1 by immunofluorescence, and that is enriched in clathrin-coated vesicles (CCVs), confirming that it is a bona fide component of the CCV machinery. By gel filtration, aftiphilin coelutes with two other AP-1 binding partners, p200a and gamma-synergin. Antibodies against any one of these three proteins immunoprecipitate the other two, and knocking down any of the three proteins by siRNA causes a reduction in the levels of the other two, indicating that they form a stable complex. Like AP-1-depleted cells, aftiphilin-depleted cells missort a CD8-furin chimera and the lysosomal enzyme cathepsin D. However, whereas AP-1-depleted cells recycle endocytosed transferrin more slowly than untreated cells, aftiphilin-depleted cells accumulate endocytosed transferrin in a peripheral compartment and recycle it more rapidly. These observations show that in general, the aftiphilin/p200/gamma-synergin complex facilitates AP-1 function, but the complex may have additional functions as well, because of the opposing effects of the two knockdowns on transferrin recycling.
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PMID:The aftiphilin/p200/gamma-synergin complex. 1575 25

Metastasis of cancer cells from the primary tumor is associated with poor prognosis and decreased overall survival. One protein implicated in inhibiting metastasis is the tumor metastasis suppressor nonmetastatic protein 23 homologue 1 (NM23-H1). NM23-H1 is a multifunctional protein, which, in addition to limiting metastasis, has DNase and histidine protein kinase activities. We have identified new functions for NM23-H1 in influencing estrogen receptor alpha (ER alpha)-mediated gene expression. Using a battery of molecular and biochemical techniques, we show that NM23-H1 interacts with ER alpha and increases the ER alpha-estrogen response element (ERE) interaction. When NM23-H1 expression is increased in U2 osteosarcoma and MDA-MB-231 breast cancer cells, transcription of a transiently transfected, estrogen-responsive reporter plasmid is decreased. More importantly, when endogenous NM23-H1 expression is knocked down in MCF-7 human breast cancer cells using small interfering RNA, estrogen responsiveness of the progesterone receptor (PR), Bcl-2, cathepsin D, and cyclin D1 genes, but not the pS2 gene, is enhanced. Furthermore, NM23-H1 associates with the region of the PR gene containing the +90 activator protein 1 site, but not with the ERE-containing region of the pS2 gene, indicating that NM23-H1 mediates gene-specific effects by association with endogenous chromatin. Our studies suggest that the capacity of NM23-H1 to limit the expression of estrogen-responsive genes such as cathepsin D and Bcl-2, which are involved in cell migration, apoptosis, and angiogenesis, may help to explain the metastasis-suppressive effects of this protein. The complementary abilities of ER alpha and NM23-H1 together to influence gene expression, cell migration, and apoptosis could be key factors in helping to determine tumor cell fate.
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PMID:Interaction of the tumor metastasis suppressor nonmetastatic protein 23 homologue H1 and estrogen receptor alpha alters estrogen-responsive gene expression. 1797 5

Most soluble lysosomal hydrolases are sorted in the trans-Golgi network (TGN) and delivered to the lysosomes by the mannose 6-phosphate receptor (M6PR). However, the non-enzymic sphingolipid activator protein (SAP), prosaposin, as well as certain soluble lysosomal hydrolases, is sorted and trafficked to the lysosomes by sortilin. Based on previous results demonstrating that prosaposin requires sphingomyelin to be targeted to the lysosomes, we hypothesized that sortilin and its ligands are found in detergent-resistant membranes (DRMs). To test this hypothesis we have analyzed DRM fractions and demonstrated the presence of sortilin and its ligand, prosaposin. Our results showed that both the M6PR and its cargo, cathepsin B, were also present in DRMs. Cathepsin H has previously been demonstrated to interact with sortilin, while cathepsin D interacts with both sortilin and the M6PR. Both of these soluble lysosomal proteins were also found in DRM fractions. Using sortilin shRNA we have showed that prosaposin is localized to DRM fractions only in the presence of sortilin. These observations suggest that in addition to interacting with the same adaptor proteins, such as GGAs, AP-1 and retromer, both sortilin and the M6PR localize to similar membrane platforms, and that prosaposin must interact with sortilin to be recruited to DRMs.
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PMID:Sortilin and prosaposin localize to detergent-resistant membrane microdomains. 1899 38

The delivery of soluble lysosomal proteins to the lysosomes is dependent primarily on the mannose 6-phosphate receptor (MPR). The MPR has been demonstrated to attain the early endosomes via a process that requires the interaction of its cytosolic domain with the GGA and AP-1 adaptor proteins. Additionally, the MPR can be recycled back to the trans-Golgi network (TGN) through its interaction with the retromer complex. Interestingly, in I-cell disease (ICD), in which the MPR pathway is non-functional, many soluble lysosomal proteins continue to traffic to the lysosomes. This observation led to the discovery that sortilin is responsible for the MPR-independent targeting of the sphingolipid activator proteins (SAPs) and acid sphingomyelinase (ASM). More recently, our laboratory has tested the hypothesis that sortilin is also capable of sorting a variety of cathepsins that exhibit varying degrees of MPR-independent transport. We have demonstrated that the transport of cathepsin D is partially dependent upon sortilin, that cathepsin H requires sortilin, and that cathepsins K and L attain the lysosomes in a sortilin-independent fashion. As a type-1 receptor, sortilin also has numerous cytosolic binding partners. It has been observed that like the MPR, the anterograde trafficking of sortilin and its cargo require both GGAs and AP-1. Similarly, the retrograde recycling pathway of sortilin also involves an interaction with retromer through a YXXphi site in the cytosolic tail of sortilin. In conclusion, the cytosolic domains of sortilin and MPR possess a high degree of functional homology and both receptors share a conserved trafficking mechanism.
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PMID:The interactomics of sortilin: an ancient lysosomal receptor evolving new functions. 1922 51