Activation of Xenopus eggs by proteases: possible involvement of a sperm protease in fertilization.
Egg activation in cross-fertilization between Xenopus eggs and Cynops sperm may be caused by a protease activity against Boc-Gly-Arg-Arg-MCA in the sperm acrosome. To determine the role of the sperm protease in fertilization, the protease was purified from Cynops sperm using several chromatographic techniques. We found that purified sperm protease readily hydrolyzes Boc-Gly-Arg-Arg-MCA and Z-Arg-Arg-MCA, that protease activity was inhibited by the trypsin inhibitors aprotinin and leupeptin, and that not only the purified protease, but also cathepsin B, induces activation in Xenopus eggs. We inseminated unfertilized Xenopus eggs with homologous sperm in the presence of various peptidyl MCA substrates or protease inhibitors and demonstrated that trypsin inhibitors or MCA substrates containing Arg-Arg-MCA reversibly inhibited fertilization of both fully jellied and denuded eggs. Sperm motility was not affected by the reagents. An extract obtained from Xenopus sperm showed hydrolytic activity against Boc-Gly-Arg-Arg-MCA, Z-Arg-Arg-MCA, and Arg-MCA. These results suggest that the tryptic protease in Xenopus sperm is involved in fertilization, most likely by participating in egg activation. (+info)
Cathepsin B immunohistochemical staining in tumor and endothelial cells is a new prognostic factor for survival in patients with brain tumors.
The cysteine endopeptidase, cathepsin (Cat) B, and its endogenous inhibitor, stefin A, were found relevant for cancer progression of many neoplasms, including human brain tumors. Histological sections of 100 primary brain tumors, 27 benign and 73 malignant, were stained immunohistochemically for Cat B and stefin A. The immunohistochemical staining of Cat B in tumor cells, endothelial cells, and macrophages was scored separately from 0-12. The score in tumor and endothelial cells was significantly higher in malignant tumors compared with benign tumors (P<0.000). A significant correlation between immunostaining of Cat B (scored together for tumor and endothelial cells) and clinical parameters, such as duration of symptoms, Karnofsky score, psycho-organic symptoms, and histological score was demonstrated. Univariate survival analysis indicated that total Cat B score above 8 was a significant predictor for shorter overall survival (P = 0.003). In glioblastoma multiforme, intense Cat B staining of endothelial cells was a significant predictor for shorter survival (P = 0.003). Stefin A immunostaining was weak and detected only in a few benign and some malignant tumors, suggesting that this inhibitor alone is not sufficient in balancing proteolytic activity of Cat B. We conclude that specific immunostaining of Cat B in tumor and endothelial cells can be used to predict the risk of death in patients with primary tumors of the central nervous system. (+info)
Expression and alteration of the S2 subsite of the Leishmania major cathepsin B-like cysteine protease.
The mature form of the cathepsin B-like protease of Leishmania major (LmajcatB) is a 243 amino acid protein belonging to the papain family of cysteine proteases and is 54% identical to human-liver cathepsin B. Despite the high identity and structural similarity with cathepsin B, LmajcatB does not readily hydrolyse benzyloxycarbonyl-Arg-Arg-7-amino-4-methyl coumarin (Z-Arg-Arg-AMC), which is cleaved by cathepsin B enzymes. It does, however, hydrolyse Z-Phe-Arg-AMC, a substrate typically cleaved by cathepsin L and B enzymes. Based upon computer generated protein models of LmajcatB and mammalian cathepsin B, it was predicted that this variation in substrate specificity was attributed to Gly234 at the S2 subsite of LmajcatB, which forms a larger, more hydrophobic pocket compared with mammalian cathepsin B. To test this hypothesis, recombinant LmajcatB was expressed in the Pichia pastoris yeast expression system. The quality of the recombinant enzyme was confirmed by kinetic characterization, N-terminal sequencing, and Western blot analysis. Alteration of Gly234 to Glu, which is found at the corresponding site in mammalian cathepsin B, increased recombinant LmajcatB (rLmajcatB) activity toward Z-Arg-Arg-AMC 8-fold over the wild-type recombinant enzyme (kcat/Km=3740+/-413 M-1.s-1 versus 472+/-72.4 M-1.s-1). The results of inhibition assays of rLmajcatB with an inhibitor of cathepsin L enzymes, K11002 (morpholine urea-Phe-homoPhe-vinylsulphonylphenyl, kinact/Ki=208200+/-36000 M-1. s-1), and a cathepsin B specific inhibitor, CA074 [N-(L-3-trans-propylcarbamoyloxirane-2-carbonyl)-l-isoleucyl-l- prolin e, kinact/Ki=199200+/-32900 M-1.s-1], support the findings that this protozoan protease has the P2 specificity of cathepsin L-like enzymes while retaining structural homology to mammalian cathepsin B. (+info)
Kappa light chain-associated Fanconi's syndrome: molecular analysis of monoclonal immunoglobulin light chains from patients with and without intracellular crystals.
Plasma cell dyscrasias may be responsible for Fanconi's syndrome, due to the toxicity of a free monoclonal kappa light chain toward kidney proximal tubules. Eight cases of Fanconi's syndrome were analyzed. We compared the structures of VkappaI variability subgroup V domains from five cases of Fanconi's syndrome and one myeloma without renal involvement. Among Fanconi cases, four putative structures were obtained after molecular modeling by homology, and the other had previously been refined by X-ray crystallography. The complete sequences of one VkappaI, one VkappaIII and N-terminal sequences of two VkappaI light chains, from patients with different forms of Fanconi's syndrome, were compared with four previously studied sequences. All three kappa chains responsible for a 'classical' form with intralysosomal crystals and a low mass myeloma, were encoded by the LCO2/O12 germline gene and had an unusual non-polar residue exposed to the solvent in the CDR-L1 loop. Of both VkappaI light chains from patients with Fanconi's syndrome without intracellular crystals, one derived from LCO2/O12 and the other from LCO8/O18 gene. Another feature that could be related to non-crystallization was the absence of accessible side chains in the CDR-L3 loop which is known to be implicated in dimer formation. (+info)
Collagenase, cathepsin B and cathepsin L gene expression in the synovial membrane of patients with early inflammatory arthritis.
OBJECTIVE: To examine the expression of the matrix metalloproteinase, MMP-1, and the cysteine proteases, cathepsin B (CB) and cathepsin L (CL), in the synovial membrane (SM) of patients with early inflammatory arthritis. METHODS: Samples of SM were obtained by blind needle biopsy or needle arthroscopy from inflamed knees of 28 patients with early inflammatory arthritis (mean disease duration 10.2 months, range 2 weeks-18 months). Sixteen patients had rheumatoid arthritis (RA), nine psoriatic arthritis and there was one each with ankylosing spondylitis, gout and an undifferentiated arthritis. Comparison was made with tissue from two patients with established erosive RA and three normal synovial tissue samples. In situ hybridization was performed using digoxigenin-labelled RNA probes. RESULTS: MMP-1, CB and CL were expressed in all patients with early arthritis and in established erosive RA, whereas normal synovium showed only scanty expression. The three proteases were prominent in perivascular infiltrates and endothelial cells of early arthritis tissue. MMP-1 was observed primarily in the lining layer, but was also evident in the sublining area. CB and CL were expressed to a lesser extent in the lining layer, and were present mainly in the subintima. The three proteases were not found in lymphoid aggregrates. No differences were observed between the disease categories. CONCLUSIONS: The detection of MMP-1, CB and CL in the synovium shortly after symptom onset implies that the potential for joint destruction exists at a very early stage in the disease. In addition, the perivascular and endothelial cell expression suggests a role for these proteases in mononuclear cell influx to the inflamed synovium and in angiogenesis. (+info)
Antigen secreted from noncytosolic Listeria monocytogenes is processed by the classical MHC class I processing pathway.
Intracellular bacteria can reside in a vacuolar compartment, or they can escape the vacuole and become free living in the cytoplasm. The presentation of Ag by class I MHC molecules has been defined primarily for Ag present in the cytoplasm. It was therefore thought that Ags from bacteria that remain in a vacuole would not be presented by MHC class I molecules. Although some studies have provided data to support this idea, it is not necessarily true for all intracellular bacteria. For example, we have previously demonstrated that an epitope from the p60 protein secreted by LLO- Listeria monocytogenes, which does not reside in the cytoplasm, can be presented by MHC class I molecules to a T cell clone specific for the epitope, p60217-225. We have further examined the route by which Ag secreted by LLO- L. monocytogenes is presented by MHC class I molecules. Using pharmacological inhibitors, we demonstrate that MHC class I presentation of the p60 epitope derived from by LLO- L. monocytogenes requires phagolysosome fusion and processing by the proteasome. Lysosomal cathepsins, however, are not required for processing of the p60 epitope. Similarly, processing of the AttM epitope, secreted by LLO- L. monocytogenes and presented by H2-M3, also requires phagolysosome fusion and cleavage by the proteasome. Thus, p60 and AttM secreted by LLO- L. monocytogenes are processed via the classical class I pathway for presentation by MHC class I molecules. (+info)
The affinity and kinetics of inhibition of cysteine proteinases by intact recombinant bovine cystatin C.
Recent studies have shown that the bovine cysteine proteinase inhibitor, cystatin C, is synthesized as a preprotein containing a 118-residue mature protein. However, the forms of the inhibitor isolated previously from bovine tissues had shorter N-terminal regions than expected from these results, and also lower affinity for proteinases than human cystatin C. In this work, we report the properties of recombinant, full-length bovine cystatin C having a complete N-terminal region. The general characteristics of this form of the inhibitor, as reflected by the isoelectric point, the far-ultraviolet circular dichroism spectrum, the thermal stability and the changes of tryptophan fluorescence on interaction with papain, resembled those of human cystatin C. The affinity and kinetics of inhibition of papain and cathepsins B, H and L by the bovine inhibitor were also comparable with those of the human inhibitor, although certain differences were apparent. Notably, the affinity of bovine cystatin C for cathepsin H was somewhat weaker than that of human cystatin C, and bovine cystatin C bound to cathepsin L with about a four-fold higher association rate constant than the human inhibitor. This rate constant is comparable with the highest values reported previously for cystatin-cysteine proteinase reactions. The full-length, recombinant bovine cystatin C bound appreciably more tightly to proteinases than the shorter form characterized previously. Digestion of the recombinant inhibitor with neutrophil elastase resulted in forms with truncated N-terminal regions and appreciably decreased affinity for papain, consistent with the forms of bovine cystatin C isolated previously having arisen by proteolytic cleavage of a mature, full-length inhibitor. (+info)
Accumulation of sialic acid in endocytic compartments interferes with the formation of mature lysosomes. Impaired proteolytic processing of cathepsin B in fibroblasts of patients with lysosomal sialic acid storage disease.
The impact of an altered endocytic environment on the biogenesis of lysosomes was studied in fibroblasts of patients suffering from sialic acid storage disease (SASD). This inherited disorder is characterized by the accumulation of acidic monosaccharides in lysosomal compartments and a concomitant decrease of their buoyant density. We demonstrate that C-terminal trimming of the lysosomal cysteine proteinase cathepsin B is inhibited in SASD fibroblasts. This late event in the biosynthesis of cathepsin B normally takes place in mature lysosomes, suggesting an impaired biogenesis of these organelles in SASD cells. When normal fibroblasts are loaded with sucrose, which inhibits transport from late endosomes to lysosomes, C-terminal cathepsin B processing is prevented to the same extent. Further characterization of the terminal endocytic compartments of SASD cells revealed properties usually associated with late endosomes/prelysosomes. In addition to a decreased buoyant density, SASD "lysosomes" show a reduced acidification capacity and appear smaller than their normal counterparts. We conclude that the accumulation of small non-diffusible compounds within endocytic compartments interferes with the formation of mature lysosomes and that the acidic environment of the latter organelles is a prerequisite for C-terminal processing of lysosomal hydrolases. (+info)