Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01034 (cystatin C)
 3,397 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We investigated the appearance and activity of the cysteine proteinase cathepsin B and its physiological inhibitors, stefins A and B, at the cellular level in human tumor cell lines HS-24, derived from a primary lung tumor (squamous cell), and SB-3, derived from a metastasis (lung adenocarcinoma). In addition to cathepsin B, these tumor cells also expressed the immunologically and functionally related cathepsin L, but not cathepsin H. Stefin A was found in HS-24 but not in SB-3 cells; stefin B was found in both cell types. Using a specific fluorogenic cytochemical assay, the intracellular activity of the enzyme was localized and quantified. Thus, the cellular cathepsin B kinetics for the synthetic substrates Z-Arg-Arg-4M beta NA and Z-Val-Lys-Lys-Arg-4M beta NA, its pH dependence and inhibition by E64, stefins A and B, and cystatin C could be determined. From these measurements it appeared that the enzyme exhibited different cleavage rates for these substrates in the different cell types, showed considerable cleavage activity at neutral pH, which was stable under these conditions for extended time periods, and was highly sensitive to the inhibitors E64 and cystatin C but was considerably less sensitive to stefins, particularly stefin A. By conventional light microscopy, confocal laser scanning microscopy, and electron microscopy the enzymatic activity was localized in lysosomes, as expected, but also in the endoplasmic reticulum, nuclear membrane, and plasma membrane. The endoplasmic reticulum is a site at which only pre-mature enzyme forms exist, which are usually not active. The appearance of enzymatic activity at the plasma membrane confirms earlier biochemical and immunofluorescence microscopic investigations. The different sites of localization within the cells make it likely that different forms of the enzyme are expressed simultaneously, which follow alternate ways of processing and sorting. Taken together, the results support an involvement of the enzyme under extracellular conditions in degradative processes.
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PMID:Cathepsin B activity in human lung tumor cell lines: ultrastructural localization, pH sensitivity, and inhibitor status at the cellular level. 801 75

To define the cellular processing of human cystatin C as well as to lay the groundwork for investigating its contribution to lcelandic Hereditary Cerebral Hemorrhage with Amyloidosis (HCHWA-I), we have characterized the trafficking, secretion, and extracellular fate of human cystatin C in transfected Chinese hamster ovary (CHO) cells. It is constitutively secreted with an intracellular half-life of 72 min. Gel filtration of cell lysates revealed the presence of three cystatin C immunoreactive species; an 11 kDa species corresponding to monomeric cystatin C, a 33 kDa complex that is most likely dimeric cystatin C and immunoreactive material, > or = 70 kDa, whose composition is unknown. Intracellular monomeric cystatin C is functionally active as a cysteine protease inhibitor, while the dimer is not. Medium from the transfected CHO cells contained only active monomeric cystatin C indicating that the cystatin C dimer, formed during intracellular trafficking, is converted to monomer at or before secretion. Cells in which exit from the endoplasmic reticulum (ER) was blocked with brefeldin A contained the 33 kDa species, indicating that cystatin C dimerization occurs in the ER. After removal of brefeldin A, there was a large increase in intracellular monomer suggesting that dimer dissociation occurs later in the secretion pathway, after exiting the ER but prior to release from the cell. Extracellular monomeric cystatin C was found to be internalized into lysosomes where it again dimerized, presumably as a consequence of the low pH of late endosome/lysosomes. As a dimer, cystatin C would be prevented from inhibiting the lysosomal cysteine proteases. These results reveal a novel mechanism, transient dimerization, by which cystatin C is inactivated during the early part of its trafficking through the secretory pathway and then reactivated prior to secretion. Similarly, its uptake by the cell also leads to its redimerization in the lysosomal pathway.
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PMID:Human cystatin C forms an inactive dimer during intracellular trafficking in transfected CHO cells. 936 56

An autosomal recessive murine mutation, coined "aly/aly" or "alymphoplasia," was recently reported. Homozygotes for aly are defective in both humoral and cell-mediated immune function and have diffuse lymphoid cell infiltration of various tissues, particularly around the conduit ducts of the pancreas and salivary glands. In pilot studies in our laboratories, aly/aly mice were found to have peculiar biliary tract lesions, which were analyzed histologically and immunohistochemically in the present study. The livers of aly/aly mice older than 8 weeks consistently showed a variable lymphoid cell infiltration with lymph follicle formation in portal tracts; intrahepatic biliary epithelial cells showed various types of damage including pseudopyloric gland metaplasia and proliferative changes. In addition, the extrahepatic bile duct and intrahepatic large bile duct were found to contain an acidophilic substance in their epithelial cytoplasm. In the lumen and occasionally in the cytoplasm of these bile ducts, acidophilic crystals were also seen. Ultrastructurally, the intracytoplasmic acidophilic substances consisted of membrane-bound intracytoplasmic inclusions with homogeneous electron density, likely derived from rough endoplasmic reticulum (ER). Immunohistochemically, the cytoplasmic acidophilic substances were simultaneously positive for cystatin C, gastrin, serotonin, and somatostatin. In contrast, the acidophilic crystals did not react with any of these antibodies. These findings suggest that the intracytoplasmic acidophilic substances may contain a precursor of the peptide hormones, possibly because of defective secretion or intracellular transport. We believe that the aly/aly mouse is a useful model for the analysis of biliary metabolic events, and for studies of the interaction of the immune system and biliary destruction.
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PMID:aly/aly mice: a unique model of biliary disease. 962 Mar 19

An important gap in our understanding of the pathogenesis of the amyloidoses is the identification of the cellular events that lead from synthesis of an amyloid precursor protein to its conversion to the amyloid fiber subunit. We address this question by characterizing the effects of an amyloidogenic mutation on the intracellular processing of its protein product. The protein, a mutant of the cysteine protease inhibitor cystatin C, is the amyloid precursor protein in Hereditary Cerebral Hemorrhage with Amyloidosis--Icelandic type (HCHWA-I). The amyloid fibers are composed of mutant cystatin C (L68Q) that lacks the first 10 amino acids. We have previously shown that processing of wild-type cystatin C entails formation of a transient intracellular dimer that dissociates prior to secretion, such that extracellular cystatin C is monomeric. We report here that the cystatin C mutation engenders several alterations in its intracellular trafficking. It forms a stable intracellular dimer that is partially retained in the endoplasmic reticulum and degraded. The bulk of mutant cystatin C that is secreted does not dissociate and is secreted as an inactive dimer. Thus, formation of the stable mutant cystatin C dimer is an early event in the pathogenesis of this disease.
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PMID:Cellular processing of the amyloidogenic cystatin C variant of hereditary cerebral hemorrhage with amyloidosis, Icelandic type. 1052 81

We compared the distribution of a cysteine proteinase inhibitor, cystatin C, with that of cathepsin K in osteoclasts of the mouse tibia by immunolight and immunoelectron microscopy. Light microscopically, strong immunoreactivity for cystatin C was found extracellularly along the resorption lacuna and intracellularly in the organelles of osteoclasts. In serial sections, various patterns of cystatin C and cathepsin K localization were seen, specifically: (1) some resorption lacuna were positive for both cystatin C and cathepsin K; (2) others were positive for either cystatin C or cathepsin K, but not both; and (3) some lacuna were negative for both. In osteoclasts, the localization of cystatin C was similar to that of cathepsin K. Furthermore, cystatin C immunoreactivity was detected in preosteoclasts and osteoblasts, whereas cathepsin K was seen only in preosteoclasts. Electron microscopically, cystatin C immunoreactive products were found in the rough endoplasmic reticulum (ER), Golgi apparatus, vesicles, granules, and vacuoles of osteoclasts. These cystatin C-positive vesicles had fused or were in the process of fusion with the ampullar vacuoles (extracellular spaces) containing cystatin C-positive, fragmented, fibril-like structures. The extracellular cystatin C was deposited on and between the cytoplasmic processes of ruffled borders, and on and between type I collagen fibrils. In the basolateral region of osteoclasts, cystatin C-positive vesicles and granules also fused with vacuoles that contained cystatin C-positive or negative fibril-like structures. These results indicate that osteoclasts not only synthesize and secrete cathepsin K from the ruffled border into the bone resorption lacunae, but also a cysteine proteinase inhibitor, cystatin C. Therefore, it is suggested that cystatin C regulates the degradation of bone matrix by cathepsin K, both extracellularly and intracellularly.
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PMID:Comparison in localization between cystatin C and cathepsin K in osteoclasts and other cells in mouse tibia epiphysis by immunolight and immunoelectron microscopy. 1147 90

Cystatin F is a cysteine peptidase inhibitor recently discovered in haematopoietic cells by cDNA cloning. To further investigate the expression, distribution and properties of the native human inhibitor the promyeloid cell line U937 has been studied. The cells expressed relatively large quantities of cystatin F, which was found both secreted and intracellularly. The intracellular levels were unusually high for a secreted cystatin ( approximately 25% of the cystatin F in 2- or 4-day culture medium). By contrast, U937 cells contained only 3-4% of the related inhibitor, cystatin C. Cystatin F purified from lysates of U937 cells showed three major forms carrying two, one or no carbohydrate chains. Immunocytochemistry demonstrated a marked cytoplasmic cystatin F staining in a granular pattern. Double staining with a marker for endoplasmic reticulum revealed no colocalization for cystatin F. Analysis of the promoter region of the cystatin F gene (CST7) showed that it, like that of the cystatin C gene (CST3), is devoid of typical TATA- and CAAT-box elements. In contrast to the cystatin C promoter, it does not contain multiple Sp1 binding sites, but has a unique site for C/EBPalpha, possibly explaining the restricted expression of the cystatin F gene. Cells stimulated with all-trans retinoic acid to differentiate them towards a granulocytic pathway, showed a strong ( approximately 18-fold) down-regulation of intracellular cystatin F and almost abolished secreted levels of the inhibitor. Stimulation with tetradecanoyl phorbol acetate, causing monocytic differentiation, also resulted in down-regulation (two fold to threefold) of cystatin F expression, whereas the cystatin C expression was essentially unaltered in both experiments. The results suggest that cystatin F as an intracellular cysteine peptidase inhibitor with readily regulated expression, may be a candidate to control the cysteine peptidase activity known to be essential for antigen presentation in different blood cell lineages.
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PMID:Regulated expression and intracellular localization of cystatin F in human U937 cells. 1242 48

We intensively examined the spinal cord of an autosomal recessive juvenile parkinsonism (ARJP) female patient with a homozygous exon 3 deletion in the parkin gene, anticipating a possible involvement of anterior horn neurons. Although the clinical features of the patient were consistent with parkinsonism as a result of parkin mutation, her tendon reflex was abolished in the lower limbs. This feature was in contrast with hyperreflexia, usually found in previous reports of ARJP. Histologically, on the level of the cervical, thoracic, and sacral spinal cord, anterior horn neurons were well preserved and normal. However, the lumbar spinal cord exhibited many swellings of proximal axons (spheroids) and degenerative changes in the somata of the large anterior horn neurons such as central chromatolysis, cystatin C-negative small eosinophilic inclusions, and eosinophilic Lewy body-like inclusions. Ultrastructurally, accumulations of neurofilaments and abnormal structures, such as inclusion bodies similar to skein-like inclusions and disorganized rough endoplasmic reticulum, were observed in the somata and neuronal processes. Lewy body-like inclusions in this study were positively immunostained for both alpha-synuclein and ubiquitin that closely resemble Lewy bodies, but are different from Lewy body-like inclusions negatively immunostained for alpha-synuclein in amyotrophic lateral sclerosis. These findings suggest that eosinophilic inclusions that closely resemble Lewy bodies may be formed in the spinal motor neurons of ARJP patients with parkin mutations and the motor neurons of these patients may be vulnerable to neurodegeneration.
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PMID:Involvement of spinal motor neurons in parkin-positive autosomal recessive juvenile parkinsonism. 1803 67

Ultrastructural changes of the bone marrow in chicks inoculated with chicken anaemia agent (CAA: MSB1-TK5803 strain) and age-matched controls are described. Erythropoiesis in the lumen of the intravascular spaces (sinuses) of unaffected bone marrow were classed into four consecutive stages according to cell morphology: proerythroblasts, basophilic erythroblasts, polychromatophilic erythroblasts and erythrocytes. In the early stage of infection, haematopoietic cells showed irregular plasma membrane, vacuolisation, formation of pseudopods and electron-opaque regions in the cytoplasm as well as intranuclear inclusions consisting of fine granular or homogeneous materials. Aggregation of virus-like particles, of 14 nm in diameter, was rarely observed in the degenerative haematopoietic cells. Subsequently, an increase in numbers of macrophages with engulfed degenerative and necrotic haematopoietic cells and plasma cells with prominent Golgi complex and well developed rough endoplasmic reticulum was observed in the anaemic stage. Although immature cells were rarely seen on day 12 of postinoculation (pi), active erythropoiesis resumed on day 20 pi or later.
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PMID:Ultrastructure of bone marrow in chicks inoculated with chicken anaemia agent (MSB1-TK5803 strain). 1867 64

Cystatins are present in mammals, birds, fish, insects, plants, fungi and protozoa and constitute a large protein family, with most members sharing a cysteine protease inhibitory function. In humans 12 functional cystatins exist, forming three groups based on molecular organisation and distribution in the organism. The type 1 cystatins (A and B) are known as intracellular, type 2 cystatins (C, D, E/M, F, G, S, SN and SA) extracellular and type 3 cystatins (L- and H-kininogen) intravascular proteins. The present paper is focused on the human cystatins and especially those of type 2, which are directed (with signal peptides) for cellular export following translation. Results indicating existence of systems for significant internalisation of type 2 cystatins from the extracellular to intracellular compartments are reviewed. Data showing that human neuroblastoma cell lines generally secrete high levels, but also contain high amounts of cystatin C are presented. Culturing of these cells in medium containing cystatin C at concentrations found in body fluids resulted in increased intracellular cystatin C, as a result of an uptake process. At immunofluorescence cytochemistry a pronounced vesicular cystatin C staining was observed. The simplistic denotation of the type 2 cystatins as extracellular inhibitors is thus challenged, and possible biological functions of the internalised cystatins are discussed. To illustrate the special case of high cellular cystatin content seen in cells of patients with hereditary cystatin C amyloid angiopathy, expression vectors for wild-type and L68Q mutated cystatin C were used to transfect SK-N-BE(2) cells. Clones overexpressing the two variants showed increased secreted levels of cystatin C. Within the cells the L68Q variant appeared to mainly localise to the endoplasmic reticulum rather than to acidic vesicular organelles, indicating limitations in the transport out from the cell rather than increased uptake as explanation for the elevated cellular cystatin levels seen in hereditary cystatin C amyloid angiopathy.
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PMID:Cystatins--Extra- and intracellular cysteine protease inhibitors: High-level secretion and uptake of cystatin C in human neuroblastoma cells. 2080 88

The cysteine protease inhibitor cystatin C is thought to be secreted by most cells and eliminated in the kidneys, so its concentration in plasma is diagnostic of kidney function. Low extracellular cystatin C is linked to pathologic protease activity in cancer, arthritis, atherosclerosis, aortic aneurism, and emphysema. Cystatin C forms non-inhibitory dimers and aggregates by a mechanism known as domain swapping, a property that reportedly protects against Alzheimer disease but can also cause amyloid angiopathy. Despite these clinical associations, little is known about the regulation of cystatin C production, dimerization, and secretion. We show that hematopoietic cells are major contributors to extracellular cystatin C levels in healthy mice. Among these cells, macrophages and dendritic cells (DC) are the predominant producers of cystatin C. Both cell types synthesize monomeric and dimeric cystatin C in vivo, but only secrete monomer. Dimerization occurs co-translationally in the endoplasmic reticulum and is regulated by the levels of reactive oxygen species (ROS) derived from mitochondria. Drugs or stimuli that reduce the intracellular concentration of ROS inhibit cystatin C dimerization. The extracellular concentration of inhibitory cystatin C is thus partly dependent on the abundance of macrophages and DC, and the ROS levels. These results have implications for the diagnostic use of serum cystatin C as a marker of kidney function during inflammatory processes that induce changes in DC or macrophage abundance. They also suggest an important role for macrophages, DC, and ROS in diseases associated with the protease inhibitory activity or amyloidogenic properties of cystatin C.
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PMID:Developmental regulation of synthesis and dimerization of the amyloidogenic protease inhibitor cystatin C in the hematopoietic system. 2457 4


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