Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0086543 (cataract)
 29,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Calpastatin is the natural specific inhibitor of calpain. Recent research has linked uncontrolled calpain activation to tissue damage after neuronal and cardiac ischemias, traumatic spine and brain injuries, as well as Alzheimer's disease and cataract formation. An imbalance between the activities of calpain and calpastatin is believed to be responsible for the pathological role of calpain. An important key to understanding calpain regulation by calpastatin is to determine, at the molecular level, how calpastatin interacts with calpain to inhibit its enzymatic activity. A 27-residue peptide (DPMSSTYIEELGKREVTIPPKYRELLA) derived from subdomain 1B of the repetitive domains of calpain, named peptide B27-WT, was previously shown to be a potent inhibitor of mu- and m-calpain. In this report, a combination of beta-alanine scanning mutagenesis and kinetic measurements was used to probe, in a quantitative, systematic, and simultaneous fashion, the relative contribution of the amino acid side chain and backbone functionalities to the overall calpain-inhibitory activity of B27-WT. The study identified two "hot spots," Leu(11)-Gly(12) and Thr(17)-Ile(18)-Pro(19), in B27-WT within which the residues critical for inhibitory function are clustered. Mutation of any one of the key residues in either of the two hot spots resulted in a dramatic loss of inhibitory activity. Furthermore, it was shown that a restricted conformation of the Leu(11)-Gly(12) and Thr(17)-Ile(18)-Pro(19) backbones is required for the peptide inhibitory function. These results suggest a plausible model in which the two hot spots are situated at or near the interface(s) of the calpain-calpastatin complex and act in a concerted fashion to inhibit calpain. The information on the specific contribution of the amide bond and side chain of each key residue to the bioactivity of B27-WT will contribute to a better understanding of the mechanism of calpain inhibition and lead to novel and effective therapies based on the specific inhibition of dysregulated or overactivated calpain.
 ...
PMID:Structural determinants of the calpain inhibitory activity of calpastatin peptide B27-WT. 1250 Sep 71

To explore cornea permeable calpain inhibitors, four compounds displaying different characteristics were designed and synthesized based on the known potent calpain inhibitor, peptidyl aldehyde SJA6017. Two approaches were adopted; an improvement in the physicochemical properties, and conversion of the active aldehyde. The water-soluble peptidyl aldehyde 1 containing a pyridine ring at the P3 site showed a modest inhibition against calpains and an improvement of corneal permeability in comparison with SJA6017. Replacement of the aldehyde of SJA6017 by an alpha-ketoamide provided compound 2 that was approximately equipotent with SJA6017, but it was extremely water-insoluble. However, compound 3, in which the aldehyde was converted into a cyclic hemiacetal, proved to be a less potent calpain inhibitor than SJA6017, but demonstrated excellent transcorneal permeability. Further modification generating the cyclic hemiacetal 4 containing a thiourea linker between the P3 and P2 sites exhibited potent inhibitory activities, high cornea permeability and excellent efficacy in the rat lens culture cataract model.
 ...
PMID:Exploration of cornea permeable calpain inhibitors as anticataract agents. 1262 63

Calpain, a Ca(2+)-requiring cytoplasmic cysteine protease, plays indispensable roles in various cellular functions such as signal transduction, cell growth and differentiation, apoptosis, necrosis, and so on. Although most of the detailed physiological functions of calpains have not yet been elucidated, the importance of calpain is obvious from the increasing numbers of papers describing relationships between human disease states (such as Alzheimer's disease, cataract, and muscular dystrophies) and malfunction of calpain. One of the recent remarkable topics of calpain is that a single nucleotide polymorphism of CAPN10, the gene for calpain 10, is related to type 2 diabetes. However, physiological functions of calpain 10 and its relation to diabetes are still unclear. Among 14 human calpain genes, mutations in CAPN3, the gene for p94/calpain 3a and Lp82/calpain 3b, are the only example that genetically connects the calpain gene and human disease, in this case, limb-girdle muscular dystrophy type 2A (LGMD2A). p94 has unique characteristics such as apparent Ca(2+)-independent activation and very rapid autolytic activity, which are dependent on p94-specific regions, NS, IS1, and IS2. Based on the 3D structures of micro - and m-calpain, molecular functions of p94 in relation to LGMD2A are discussed, with the hope of providing us with some clues to understand calpain functions and its relationships to human diseases.
 ...
PMID:[Calpain and pathology in view of structure-function relationships]. 1284 69

The purpose of the present study was to compare the susceptibility of crystallins proteolyzed by ubiquitous calpain 2 and by lens-specific calpain Lp82 to insolubilization. To test this, transgenic (TG) mice expressing a calpain 2, in which the active site cysteine 105 was mutated to alanine, were produced. Expression of mutated calpain 2 was driven in lens by coupling the mutated gene to the betaB1-crystallin promoter. Light scattering was measured in solutions of lens proteins after activation of endogenous calpain 2 and/or Lp82. Mass spectrometric analysis was performed to determine the cleavage sites and the calpain responsible for insolubilization of crystallins. Lens proteins from TG mice incubated in vitro with calcium showed higher light scattering compared to proteins from wild type (WT) mice. alphaA-crystallin from TG mice was proteolyzed by Lp82. In contrast, alphaA-crystallin in lenses from WT mice were proteolyzed by both calpain 2 and Lp82. These results suggested that Lp82-induced proteolysis of crystallins caused increased susceptibility of truncated crystallins to in vitro precipitation. Since Lp82 is highest in young animals, Lp82-induced proteolysis and precipitation may be one of the factors responsible for the cataract formation in young rodents.
 ...
PMID:Differential influence of proteolysis by calpain 2 and Lp82 on in vitro precipitation of mouse lens crystallins. 1289 59

An overdose of sodium selenite induces cataracts in young rats. The mid-stage events producing the cataract include calpain-induced hydrolysis and precipitation of lens proteins. Apoptosis in lens epithelial cells has been suggested as an initial event in selenite cataracts. Expression levels of two genes associated with apoptosis were altered in lens epithelial cells from selenite-injected rats. The purpose of the present experiment was to perform a more comprehensive search for changes in expression of mRNAs in lens epithelial cells in order to more fully delineate the early events in selenite-induced cataracts. Lens epithelial cells were harvested at 1 and 2 days after a single subcutaneous injection of sodium selenite (30 mumol/kg body weight) into 12-day-old rats. Gene expression was analyzed using a commercial DNA array (Rat Genome U34A GeneChip array, Affymetrix). Of approximately 8000 genes assayed by hybridization, 13 genes were decreased and 27 genes were increased in the rat lens epithelial cells after injection of selenite. Some of the up-regulated genes included apoptosis-related genes, and a majority of the down-regulated genes were mitochondrial genes. Previously observed changes in expression of EGR-1 mRNA were also confirmed. Changes in the expression patterns of mRNAs were also confirmed by RT-PCR. To determine the mechanism for damage of lens epithelial cells (alpha TN4 cell) by culture in selenite, leakage of cytochrome c from mitochondria was measured. Selenite caused significant leakage of cytochrome c into the cytosol of alpha TN4 cells. Our data suggested that the loss of integrity of lens epithelial cells by selenite might be caused by preferential down-regulation of mitochondrial RNAs, release of cytochrome c, and impaired mitochondrial function. Up-regulation of mRNAs involved in maintenance of DNA, regulation of metabolism, and induction of apoptosis may also play roles.
 ...
PMID:Expression changes in mRNAs and mitochondrial damage in lens epithelial cells with selenite. 1457 11

Acetaminophen (APAP) is biotransformed by hepatic cytochrome P450 (CYP) enzymes to the cataractogenic metabolite N-acetyl-p-benzoquinone imine (NAPQI). In the previous studies in which NAPQI was injected into the anterior chamber of mouse eye, we observed mitochondrial dysfunction and disturbances in Ca2+ homeostasis in the lens epithelium, and activation of the nonlysosomal neutral protease calpain. In this work we investigated whether intraperitoneal injection of APAP elicits similar cellular responses in the lens epithelium prior to the onset of lens opacity development. Following APAP injection, reactive oxygen species generation, intracellular free Ca2+ increase and calpain activation in the lens epithelium were determined in situ by fluorescence confocal microscopy. It was found that cellular events in the lens prior to the onset of opacification were essentially identical to those elicited by NAPQI. In addition, lens calpain activities were characterized based on their Ca2+ requirement and several calpain inhibitors were shown to prevent cataract development.
 ...
PMID:Cellular events preceding acetaminophen cataractogenesis studied by confocal fluorescence microscopy. 1460 27

There is emerging evidence to suggest that the unregulated Ca(2+)-mediated proteolysis of essential lens proteins by calpains might be a major contributor to some forms of cataract in both animals and humans. Moreover, recently solved calpain structures have revealed molecular-level details of the activation mechanism used by these proteases, enabling the structure-based design of potent calpain inhibitors with the potential to act as anti-cataract agents. These agents offer the first real hope of an urgently needed alternative to the surgical treatment of at least some forms of cataract and relief from a life-depreciating condition on a global scale.
 ...
PMID:Calpains: targets of cataract prevention? 1510 61

UV-A radiation produces cataract in animals, enhances photoaging of the lens and skin and increases the phototoxicity of drugs. However, the nature of genes that are activated or repressed after cellular exposure to UV-A radiation remains enigmatic. Because lens epithelial cells exposed to UV-A radiation undergo apoptosis 4 h after exposure to the stress, we sought to establish the change in gene expression in cells by UV-A radiation using gene expression profiling using complementary DNA microarrays containing about 12 000 genes. We identified 78 genes abnormally expressed in UV-A-irradiated cells (showing >2.5-fold change at P < 0.05). These genes are implicated in various biological processes, including signal transduction and nucleic acid binding, and genes encoding enzymes. A majority of the genes were downregulated. Our analysis revealed that the expression of genes for the transcription factors ATF-3 and Pilot increased four-fold, whereas the gene for the apoptosis regulator NAPOR-1 decreased five-fold. These changes were confirmed by real-time quantitative reverse transcriptase-polymerase chain reaction. The calpain large polypeptide 3 (CANP3) gene also increased nine-fold after UV-A radiation. In addition, peroxisomal biogenesis factor 7, glucocorticoid receptor-alpha and tumor-associated calcium signal transducer genes decreased three- to eight-fold. Western blot analysis further confirmed the increase in protein expression of ATF-3 and CANP3 and decreased expression of glucocorticoid receptor-alpha in the irradiated cells. Surprisingly, most of these genes had not been previously shown to be modulated by UV-A radiation. Our results show that human lens epithelial cells respond to a single dose of UV-A radiation by enhancing or suppressing functionally similar sets of genes, some of which have opposing functions, around the time at which apoptosis occurs. These studies support the intriguing concept that activation of competing pathways favoring either cell survival or death is a means to coordinate the response of cells to UV-A stress.
 ...
PMID:Identification of genes responsive to UV-A radiation in human lens epithelial cells using complementary DNA microarrays. 1533 8

Premature visual impairment due to lens opacification is a debilitating characteristic of untreated diabetes. Lens opacification is primarily due to the insolubilization of crystallins, proteins essential for lens optical properties, and recent studies have suggested that a major cause of this insolubilization may be the unregulated proteolysis of crystallins by calpains. These are intracellular cysteine proteases whose activation requires the presence of calcium (Ca2+) and elevated levels of lens Ca2+ is a condition associated with both diabetic cataractogenesis and other forms of the disorder. A number of calpains have been identified in the lens, including calpain 2, calpain 10 and two isozymes of calpain 3: Lp82 and Lp85. The use of animal hereditary cataract models have suggested that calpain 2 and/or Lp82 may be the major calpains involved in murine cataractogenesis with contributions from calpain 10 and Lp85. However, calpain 2 appears to be the major calpain involved in murine diabetic cataractogenesis and the strongest candidate of the calpains for a role in human types of cataractogenesis. Here, we present an overview of recent evidence on which these observations are based with an emphasis on the ability of calpains to proteolyse lens crystallins and calpain structural features, which appear to be involved in the Ca2+-mediated activation of these enzymes.
 ...
PMID:Role of calpains in diabetes mellitus-induced cataractogenesis: a mini review. 1536 98

Calpain inhibitors show the potential to serve as non-surgical alternatives in treating diabetic cataract and other types of these disorders. Here, we have tested the recently developed calpain inhibitor, SJA6017, for its ability to inhibit cataractogenesis in porcine lenses. These lenses were incubated in increasing levels of extralenticular calcium (Ca2+; 5-30 mM). Atomic absorption spectroscopy was used to determine total internal lens Ca2+ and a correlation between porcine lens Ca2+ uptake and levels of lens opacification were found with a total internal lens Ca2+ level of 5.8 microM Ca2+ g(-1) wet lens weight corresponding to the onset of catarctogenesis. A total internal lens Ca2+ level of 8.0 microM Ca2+ g(-1) wet lens weight corresponded to cataract occupying approximately 70% of the lens cell volume. This degree of cataract was reduced by approximately 40%, when SJA6017 (final concentration 0.8 microM) was included in the extralenticular medium, suggesting that the Ca2+-mediated activation of calpains may be involved in the observed opacification. Supporting this suggestion atomic absorption spectroscopy showed that the effect of SJA6017 (final concentration 0.8 microM) on lens opacification was not due to the compound restricting porcine lens Ca2+ uptake. The results indicate that calpain-induced cataractogenesis is dependent on extracellular Ca2+ and the calpain inhibitor SJA6017 (0.8 microM) had no significant effect on Ca2+ uptake by lens. Its inhibitory effect on lens opacification may be due to a direct action on the activity of calpain.
 ...
PMID:The in vitro retardation of porcine cataractogenesis by the calpain inhibitor, SJA6017. 1536


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>