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)

Whether specific proteases influence MHC class II antigen presentation is still not clearly defined. Cathepsin D, one of the most abundant lysosomal proteases, is thought to be dispensable for MHC class II antigen presentation, yet in vitro digestions of antigen substrates with endosomes/lysosomes from antigen-presenting cells sometimes reveal a dominant role for pepstatin-sensitive aspartyl proteases of which cathepsin D is the major representative. We tested whether the aspartyl protease substrate myoglobin requires cathepsin D activity for presentation to T cells. Surprisingly, in dendritic cells (DC) lacking cathepsin D, presentation of two different myoglobin T cell epitopes was enhanced rather than hindered. This paradox is resolved by the finding that pepstatin-sensitive myoglobin processing activity persists in lysosomes from cathepsin D-null DC and that this reduced activity, most likely due to cathepsin E, is closer to the optimum level required for myoglobin antigen presentation. Our results indicate redundancy among lysosomal aspartyl proteases and show that while processing activities can be productive for MHC class II T cell epitope generation at one level, they can become destructive above an optimal level.
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PMID:Destructive potential of the aspartyl protease cathepsin D in MHC class II-restricted antigen processing. 1625 9

Cathepsin E (CE) is an endosomal aspartic proteinase of the A1 family that is highly homologous to the lysosomal aspartic proteinase cathepsin D (CD). Newly synthesized CE undergoes several proteolytic processing events to yield mature CE, from which the N-terminal propeptide usually comprising 39 amino acids is removed. To define the role of the propeptide of CE in its biosynthesis and processing, we constructed two fusion proteins using chimeric DNAs encoding the CE propeptide fused to the mature CD tagged with HA at the COOH terminus (termed ED-HA) and encoding the CD propeptide fused to the mature CE (termed DE). Pulse-chase analysis revealed that wild-type CE expressed in human embryonic kidney cells is autoproteolytically processed into mature CE within a 12-h chase, whereas the chimeric DE failed to be converted into mature CE even after a 24-h chase. The DE chimera was nevertheless capable of acid-dependent autoactivation in vitro to yield a catalytically active form, although its specificity constants (kcat/Km) were considerably high but less (35%) than those of the wild-type CE. By contrast, the chimeric ED-HA expressed in HeLa cells underwent neither processing into a catalytically active enzyme nor acid-dependent autoactivation in vitro. The ED-HA protein was less stable than wt-CD-HA, as determined on pulse-chase analysis and on trypsin digestion. These data indicate that the propeptide of CE is essential for the correct folding, maturation, and targeting of this protein to its final destination.
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PMID:The role of the cathepsin E propeptide in correct folding, maturation and sorting to the endosome. 1627 74

Two bis-trifluoromethyl pepstatin A analogues, carboxylic acid 1 and its methyl ester 2, have been synthesised in order to probe the properties and size of the trifluoromethyl (Tfm) group and compare it to the "bigger" isobutyl that is present in pepstatin A. The results demonstrate that Tfm can effectively replace the isobutyl chain as far as inhibitory activity against plasmepsin II (PM II), an aspartic proteinase from Plasmodium falciparum, is concerned. On the other hand, replacement of isobutyl by Tfm selectively affected activity against other aspartic proteinases tested. Two lines of evidence led to these conclusions. Firstly, compounds 1 and 2 retained single-digit nanomolar inhibitory activity against PM II, but were markedly less active against PM IV, cathepsin D and cathepsin E. Secondly, the X-ray crystal structures of the three complexes of PM II with 1, 2 and pepstatin A were obtained at 2.8, 2.4 and 1.7 A resolution, respectively. High overall similarity among the three complexes indicated that the central Tfm was well accommodated in the lipophilic S1 pocket of PM II, where it was involved in tight hydrophobic contacts. The interaction of PM II with Phe111 appeared to be crucial. Comparison of the crystal structures presented here, with X-ray structures or structural models of PM IV and cathepsin D, allowed an interpretation of the inhibition profiles of pepstatin A and its Tfm variants against these three enzymes. Interactions of the P1 side chain with amino acids that point into the S1 pocket appear to be critical for inhibitory activity. In summary, Tfm can be used to replace an isobutyl group and can affect the selectivity profile of a compound. These findings have implications for the design of novel bioactive molecules and synthetic mimics of natural compounds.
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PMID:Replacement of isobutyl by trifluoromethyl in pepstatin A selectively affects inhibition of aspartic proteinases. 1630 63

Proteolysis of apolipoprotein E (apoE) may be involved in the pathogenesis of Alzheimer's disease (AD). We previously identified aspartic protease(s) as possibly contributing to the proteolysis of apoE in human brain homogenates. The current study used biochemical and immunohistochemical methods to examine whether cathepsin D (catD) and cathepsin E (catE), candidate aspartic proteases, may be involved in apoE proteolysis. CatD was found to proteolyze both lipid-free recombinant full-length human apoE and lipidated human plasma full-length apoE (apoE4/dipalmitoylphosphatidylcholine-reconstituted discs). CatE was found to proteolyze lipid-free recombinant human apoE to a much greater extent than lipidated apoE. This proteolysis, as well as proteolysis of human apoE added to brain homogenates from apoE-deficient mice, was inhibited by pepstatin A (an aspartic protease inhibitor), but not by phenylmethanesulfonyl fluoride (a serine protease inhibitor). The major apoE fragment obtained with catD included the receptor-binding domain and had an apparent molecular weight similar to that found in human brain homogenates. There was little immunoreactivity for catE in AD brain tissue sections. In contrast, qualitative and quantitative analyses of immunostained sections of the frontal cortex revealed that catD and apoE are colocalized in a subset of predominantly dense-core neuritic plaques and in some neurofibrillary tangles. A positive correlation was observed between estimated duration of illness and the percentage of apoE-positive plaques that were also catD-positive. These results suggest that aspartic proteases, catD in particular, may be involved in proteolysis of apoE and perhaps contribute to the generation of apoE fragments previously implicated in AD pathology.
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PMID:Cathepsin D-mediated proteolysis of apolipoprotein E: possible role in Alzheimer's disease. 1699 86

Selective inhibition of enzymes involved in antigen processing such as cathepsin E and cathepsin D is a valuable tool for investigating the roles of these enzymes in the processing pathway. However, the aspartic protease inhibitors, including the highly potent pepstatin A (PepA), are inefficiently transported across the cell membrane and thus have limited access to antigen processing compartments. Previously described mannose-pepstatin conjugates were efficiently taken up by the cells via receptor mediated uptake. However, cells without mannose receptors are unable to take up these conjugates efficiently. The aim of the present study was to synthesize new cell-permeable aspartic protease inhibitors by conjugating pepstatin A with well-known cell penetrating peptides (CPPs). To achieve this, the most commonly used CPPs namely pAntp(43-58) (penetratin), Tat(49-60), and 9-mer of l-arginine (R9), were synthesized and coupled to pepstatin. The enzyme inhibitory properties of these bioconjugates and their cellular uptake into MCF7 (human breast cancer cell line), Boleths (EBV-transformed B-cell line) and dendritic cells (DC) were the focus of our study. We found that the bioconjugate PepA-penetratin (PepA-P) was the most efficient cell-permeable aspartic protease inhibitor tested, and was more efficient than unconjugated PepA. Additionally, we found that PepA-P efficiently inhibited the tetanus toxoid C-fragment processing in peripheral blood mononuclear cells (PBMC), primary DC and in primary B cells. Therefore, PepA-P can be used in studying the role of intracellular aspartic proteases in the MHC class II antigen processing pathway. Moreover, inhibition of tetanus toxoid C-fragment processing by PepA-P clearly implicates the role of aspartic proteinases in antigen processing.
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PMID:A novel cell penetrating aspartic protease inhibitor blocks processing and presentation of tetanus toxoid more efficiently than pepstatin A. 1793 27

The levels of cathepsins D and E in various rat tissues during development were determined with the sensitive assay method we have developed. The level of cathepsin D increased gradually in each tissue during fetal development suggesting the gradual maturation of the lysosomal system in a cell. The level of cathepsin E differed significantly between tissues at various developmental stages. The level in liver increased rapidly from 13-day-gestation fetal stage and decreased gradually at later fetal stages. The level in other tissues such as stomach and spleen began to increase at later fetal stages or the infant stage. Cathepsin E was found in fetal hepatocytes and its gene was hypomethylated when the expression of the gene was elevated. The enzyme was found to be present mainly as a proform suggesting that, after working, an active form is rapidly inactivated.
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PMID:Development-dependent expression of cathepsins d and e in various rat tissues, with special reference to the high expression of cathepsin e in fetal liver. 1846 30

Cathepsin S (CatS) is a lysosomal cysteine protease belonging to the papain superfamily. Because of the relatively broad substrate specificity of this family, a specific substrate for CatS is not yet known. Based on a detailed study of the CatS endopeptidase specificity, using six series of internally quenched fluorescent peptides, we were able to design a specific substrate for CatS. The peptide series was based on the sequence GRWHTVGLRWE-Lys(Dnp)-DArg-NH2, which shows only one single cleavage site between Gly and Leu and where every substrate position between P-3 and P-3' was substituted with up to 15 different amino acids. The endopeptidase specificity of CatS was mainly determined by the P-2, P-1', and the P-3' substrate positions. Based on this result, systematically modified substrates were synthesized. Two of these modified substrates, Mca-GRWPPMGLPWE-Lys(Dnp)-DArg-NH2 and Mca-GRWHPMGAPWE-Lys(Dnp)-DArg-NH2, did not react with the purified cysteine proteases cathepsin B (CatB) and cathepsin L (CatL). Using a specific CatS inhibitor, we could further show that these two peptides were not cleaved by endosomal fractions of antigen presenting cells (APCs), when CatS was inhibited and related cysteine proteases cathepsin B, H, L and X were still active. Although aspartic proteases like cathepsin E and cathepsin D were also present, our substrates were suitable to quantify cathepsin S activity specifically in APCs, including B cells, macrophages, and dendritic cells without the use of any protease inhibitor. We find that CatS activity differs significantly not only between the three types of professional APCs but also between endosomal and lysosomal compartments.
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PMID:Quantifying cathepsin S activity in antigen presenting cells using a novel specific substrate. 1895 8

Proteases are involved in various biological functions. Thus, inhibition of their activities is scientifically interesting and medically important. However, there is no systematic method established to date to generate endopeptidase inhibitory peptides. Here, we report a general system to identify endopeptidase inhibitory peptides based on the use of in vitro evolution. Using this system, we generated peptides that inhibit cathepsin E (CE) specifically at a submicromolar IC(50). This system generates protease inhibitor peptides utilizing techniques of cDNA display, selection-by-function, Y-ligation-based block shuffling, and others. We further demonstrated the importance and effectiveness of a secondary library for obtaining small-sized and active peptides. CE inhibitory peptides generated by this method were characterized by a small size (8 to 12 aa) and quite different sequences, suggesting that they bind to different sites on CE. Typical CE inhibitory peptide aptamers obtained here (P(i)101; SCGG IIII SCIA) have half an inhibition activity (K(i); 5 nM) of pepstatin A (potent CE inhibitor) without inhibiting cathepsin D (structurally similar to CE). The general applicability of this system suggests that it may be useful to identify inhibitory peptides for various kinds of proteases and that it may therefore contribute to protein science and drug discovery. The peptide binding to a protein is discussed in comparison with the antibody binding to an antigen.
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PMID:Development of systemic in vitro evolution and its application to generation of peptide-aptamer-based inhibitors of cathepsin E. 1915 Mar 54

Cathepsin E belongs to the third class of enzymes - hydrolases, a subclass of peptide bond hydrolases and a sub-subclass of endopeptidases with aspartic catalytic sites. Cathepsin E is an endopeptidase with substrate specificity similar to that of cathepsin D. In a human organism, cathepsin E occurs in: erythrocytes, thymus, dendritic cells, epithelial M cells, microglia cells, Langerhans cells, lymphocytes, epithelium of gastrointestinal tract, urinary bladder, lungs, osteoclasts, spleen and lymphatic nodes. In human cells, loci of the gene of pre-procathepsin E are located on chromosome 1 in the region 1231-32. The catalytic site of cathepsin E is two residues of aspartic acid - Asp96 and Asn281, occurring in amino acid triads with sequences DTG96-98 and DTG281-283. To date, no particular role of cathepsin E in the metabolism of proteins in normal tissues has been found. However, it is known that there are many documented pathological conditions in which overexpression of cathepsin E occurs.
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PMID:Cathepsin E (EC 3.4.23.34)--a review. 2225 49

Aspartic proteinases form a widely distributed protein superfamily, including cathepsin D, cathepsin E, pepsins, renin, BACE and napsin. Human napsin genes are located on human chromosome 19q13, which comprises napsin A and napsin B. Napsin B has been annotated as a pseudogene because it lacks an in-frame stop codon; its nascent chains are cotranslationally degraded. Until recently, there have been no studies concerning the molecular evolution of the napsin protein family in the human genome. In the present study, we investigated the evolution and gene organization of the napsin protein family. Napsin B orthologs are primarily distributed in primates, while napsin A orthologs are the only napsin genes in other species. The corresponding regions of napsin B in the available sequences from primate species contain an in-frame stop codon at a position equivalent to that of human napsin A. In addition, a rare single-nucleotide polymorphism (SNP) that creates a proper stop codon in human napsin B was identified using HapMap populations. Recombinant protein expression and three-dimensional comparative modeling revealed that napsin B exhibits residual activity toward synthetic aspartic protease substrates compared with napsin A, presumably through a napsin B-specific Arg287 residue. Thus, napsin B was duplicated from napsin A during the early stages of primate evolution, and the subsequent loss of napsin B function during primate evolution reflected ongoing human-specific napsin B pseudogenization.
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PMID:Structural and phylogenetic comparison of napsin genes: the duplication, loss of function and human-specific pseudogenization of napsin B. 2333 8


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