Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.22.56 (caspase-3)
 35,750 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Fibroblast growth factor receptor signaling is an important mechanism regulating osteoblast function. To gain an insight into the regulatory role of FGF receptor-2 (FGFR2) signaling in osteoblasts, we investigated integrin-mediated attachment and cell survival in human calvarial osteoblasts expressing activated FGFR2. FGFR2 activation reduced osteoblast attachment on fibronectin. This was associated with reduced expression of the alpha5 integrin subunit normally expressed in human calvarial osteoblasts in vivo. Treatment with lactacystin, a potent inhibitor of proteasome, restored alpha5 integrin levels in FGFR2 mutant osteoblasts. Immunoprecipitation analysis showed that alpha5 integrin interacts with both the E3 ubiquitin ligase Cbl and ubiquitin. Immunocytochemistry revealed that alpha5 integrin colocalizes with FGFR2 and Cbl at the leading edge in membrane ruffle regions. Transfection with the 70Z-Cbl mutant lacking the RING domain required for Cbl-ubiquitin interaction, or with the G306E Cbl mutant that abolishes the binding ability of Cbl phosphotyrosine-binding domain restored alpha5 integrin levels. This suggests that Cbl-mediated ubiquitination plays an essential role in alpha5 integrin proteasome degradation induced by FGFR2 activation. Reduced alpha5 integrin expression was associated with an increased Bax/Bcl-2 ratio and increased caspase-9 and -3 activities in FGFR2 mutant osteoblasts. Forced expression of alpha5 integrin rescued cell attachment and corrected both the Bax/Bcl-2 ratio and caspase-3 and caspase-9 activities in FGFR2 mutant osteoblasts. We show that Cbl recruitment induced by FGFR2 activation triggers alpha5 integrin degradation by the proteasome, which results in reduced osteoblast attachment on fibronectin and caspase-dependent apoptosis. This identifies a functional role of the alpha5 integrin subunit in the induction of apoptosis triggered by FGFR2 activation in osteoblasts, and reveals that a Cbl-dependent mechanism is involved in the coordinated regulation of cell apoptosis induced by alpha5 integrin degradation.
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PMID:Cbl-mediated ubiquitination of alpha5 integrin subunit mediates fibronectin-dependent osteoblast detachment and apoptosis induced by FGFR2 activation. 1572 56

Muscle atrophy is a prominent feature of chronic kidney disease (CKD) and is frequent in other catabolic conditions. Results from animal models of these conditions as well as patients indicate that atrophy is mainly owing to accelerated muscle proteolysis in the ubiquitin-proteasome (Ub-P'some) proteolytic system. The Ub-P'some system, however, rapidly degrades actin or myosin but cannot breakdown actomyosin or myofibrils. Consequently, another protease must initially cleave the complex structure of muscle. We identified caspase-3 as an initial and potentially rate-limiting proteolytic step that cleaves actomyosin/myofibrils to produce substrates degraded by the Ub-P'some system. In rodent models of CKD and other catabolic conditions, we find that caspase-3 is activated and cleaves actomyosin to actin, myosin and their fragments. This initial proteolytic step in muscle leaves a characteristic footprint, a 14-kDa actin band, providing a potential diagnostic tool to detect muscle catabolism. We also found that stimulation of caspase-3 activity depends on inhibition of IRS-1-associated phosphatidylinositol 3-kinase (PI3K) activity; inhibiting PI3K in muscle cells also leads to expression of a critical E3-ubiquitin-conjugating enzyme involved in muscle protein breakdown: atrogin-1/MAFbx. Thus, protein breakdown by caspase-3 and the ubiquitin-proteasome system in muscle are stimulated by the same signal: a low PI3K activity. These responses could yield therapeutic strategies to block muscle atrophy.
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PMID:Molecular mechanisms activating muscle protein degradation in chronic kidney disease and other catabolic conditions. 1573 69

Ubiquitination is required throughout all developmental stages of mammalian spermatogenesis. Ubiquitin C-terminal hydrolase (UCH) L1 is thought to associate with monoubiquitin to control ubiquitin levels. Previously, we found that UCHL1-deficient testes of gad mice have reduced ubiquitin levels and are resistant to cryptorchid stress-related injury. Here, we analyzed the function of UCHL1 during the first round of spermatogenesis and during sperm maturation, both of which are known to require ubiquitin-mediated proteolysis. Testicular germ cells in the immature testes of gad mice were resistant to the early apoptotic wave that occurs during the first round of spermatogenesis. TUNEL staining and cell quantitation demonstrated decreased germ cell apoptosis and increased numbers of premeiotic germ cells in gad mice between Postnatal Days 7 and 14. Expression of the apoptotic proteins TRP53, Bax, and caspase-3 was also significantly lower in the immature testes of gad mice. In adult gad mice, cauda epididymidis weight, sperm number in the epididymis, and sperm motility were reduced. Moreover, the number of defective spermatozoa was significantly increased; however, complete infertility was not detected. These data indicate that UCHL1 is required for normal spermatogenesis and sperm quality control and demonstrate the importance of UCHL1-dependent apoptosis in spermatogonial cell and sperm maturation.
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PMID:Ubiquitin C-terminal hydrolase L-1 is essential for the early apoptotic wave of germinal cells and for sperm quality control during spermatogenesis. 1574 22

Accumulation of cytoplasmic inclusion bodies in many neurodegenerative diseases, including Alzheimer's disease (AD), might result from dysfunction of the ubiquitin-proteasome system. This system degrades many cellular proteins, including beta-catenin, a member of the Wnt signaling pathway, and a presenilin-1-interacting protein. Phosphorylation of beta-catenin marks it for ubiquitination and rapid proteasomal degradation. We found phospho-beta-catenin accumulated as detergent-insoluble, punctate, cytoplasmic inclusions in hippocampal pyramidal neurons more abundantly in AD than in aged controls. In AD, beta-catenin was ubiquitin conjugated, thus suggesting impaired proteasome-dependent degradation. Phospho-beta-catenin was partially sequestered within granulovacuolar degeneration bodies but not in lysosomes, indicating sequestration within autophagosomes. Exposure of neuronal cultures to proteasome inhibitors induced formation of detergent-insoluble, phospho-beta-catenin-positive cytoplasmic inclusions that coalesced into aggresomes and colocalized with gamma-tubulin and vimentin. These aggregates were associated with apoptotic cell death and with activation of caspase-3, c-Jun-N-terminal kinases, and c-Jun. These findings suggest that phospho-beta-catenin accumulation in AD might result from impaired proteasome function.
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PMID:Phospho-beta-catenin accumulation in Alzheimer's disease and in aggresomes attributable to proteasome dysfunction. 1578 69

The primary mechanism that contributes to decreasing skeletal muscle strength and size with healthy aging is not presently known. This study examined the contribution of the ubiquitin-proteasome pathway and apoptosis to skeletal muscle wasting in older adults (n = 21; mean age = 72.76 +/- 8.31 years) and young controls (n = 21; mean age = 21.48 +/- 2.93 years). Subjects underwent a percutaneous muscle biopsy of the vastus lateralis to determine: (1) ubiquitin ligase gene expression (MAFbx and MuRF1); (2) frequency of apoptosis; and (3) individual fiber type and cross-sectional area. In addition, a whole muscle strength test was also performed. A one-way ANOVA revealed significant increases in the number of positive TUNEL cells in older adults (87%; p < 0.05), although no significant increase in caspase-3/7 activity was detected. Additionally, ubiquitin ligase gene expression, individual muscle fiber type and CSA were not different between old and young subjects. Muscle strength was also significantly lower in old compared to young subjects (p < 0.05). In conclusion, this study indicates a preferential role for apoptosis contributing to decreases in muscle function with age.
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PMID:Contributions of the ubiquitin-proteasome pathway and apoptosis to human skeletal muscle wasting with age. 1595 31

Muscle atrophy is a prominent feature of catabolic conditions and in animal models of these conditions there is accelerated muscle proteolysis that is dependent on the ubiquitin-proteasome system. However, ubiquitin system cannot degrade actomyosin or myofibrils even though it rapidly degrades actin or myosin. We identified caspase-3 as the initial and potentially rate-limiting proteolytic step that cleaves actomyosin/myofibrils. In rodent models of catabolic conditions, we find that caspase-3 is activated to cleave muscle proteins and actomyosin to fragments that are rapidly degraded by the ubiquitin system. This initial proteolytic step in muscle can be recognized because it leaves a footprint of a characteristic 14-kDa actin band. Stimulation of caspase-3 activity depends on activation of phosphatidylinositol 3-kinase. When we suppressed this enzyme in muscle cells, protein breakdown increased as did the expression of caspase-3. In addition, there was increased expression of E3-ubiquitin-conjugating enzymes that are involved in muscle proteolysis, atrogin-1/MAFbx and MuRF1. Thus, when phosphatidylinositol 3-kinase activity is low in muscle cells or rat muscle, both caspase-3 and the ubiquitin-proteasome system are stimulated to degrade protein. Additional investigations will be needed to define the cell signaling processes that activate muscle proteolysis in uremia and catabolic conditions.
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PMID:Cellular signals activating muscle proteolysis in chronic kidney disease: a two-stage process. 1598 20

Exposure to pesticides is implicated in the etiopathogenesis of Parkinson's disease (PD). The organochlorine pesticide dieldrin is one of the environmental chemicals potentially linked to PD. Because recent evidence indicates that abnormal accumulation and aggregation of alpha-synuclein and ubiquitin-proteasome system dysfunction can contribute to the degenerative processes of PD, in the present study we examined whether the environmental pesticide dieldrin impairs proteasomal function and subsequently promotes apoptotic cell death in rat mesencephalic dopaminergic neuronal cells overexpressing human alpha-synuclein. Overexpression of wild-type alpha-synuclein significantly reduced the proteasomal activity. Dieldrin exposure dose-dependently (0-70 microM) decreased proteasomal activity, and 30 microM dieldrin inhibited activity by more than 60% in alpha-synuclein cells. Confocal microscopic analysis of dieldrin-treated alpha-synuclein cells revealed that alpha-synuclein-positive protein aggregates colocalized with ubiquitin protein. Further characterization of the aggregates with the autophagosomal marker mondansyl cadaverine and the lysosomal marker and dot-blot analysis revealed that these protein oligomeric aggregates were distinct from autophagosomes and lysosomes. The dieldrin-induced proteasomal dysfunction in alpha-synuclein cells was also confirmed by significant accumulation of ubiquitin protein conjugates in the detergent-insoluble fraction. We found that proteasomal inhibition preceded cell death after dieldrin treatment and that alpha-synuclein cells were more sensitive than vector cells to the toxicity. Furthermore, measurement of caspase-3 and DNA fragmentation confirmed the enhanced sensitivity of alpha-synuclein cells to dieldrin-induced apoptosis. Together, our results suggest that increased expression of alpha-synuclein predisposes dopaminergic cells to proteasomal dysfunction, which can be further exacerbated by environmental exposure to certain neurotoxic compounds, such as dieldrin.
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PMID:Dieldrin induces ubiquitin-proteasome dysfunction in alpha-synuclein overexpressing dopaminergic neuronal cells and enhances susceptibility to apoptotic cell death. 1598 30

S-phase kinase associated protein 2 (Skp2) is a member of an F-box family of substrate-recognition subunits of SCF ubiquitin-protein ligase complexes that has been implicated in the ubiquitin-mediated degradation of several key regulators of mammalian G1 progression, including the cyclin-dependent kinase inhibitor p27Kip1, a dosage-dependent tumor suppressor protein. The anti-sense effect was confirmed in two cell lines of oral cancer cells that also exhibited over-expression of the Skp2 protein. In this study, we examined the mechanism responsible for anti-sense-mediated growth inhibition of oral cancer cells in vitro and in vivo. Skp2-anti-sense treatment induced apoptosis characterized by an increase in the early apoptosis, fragmentation of nuclei and activation of caspase-3, -8 and -9. Moreover, the growth of xenograft tumors was markedly suppressed by Skp2-anti-sense treatment. Furthermore, histological specimen revealed apoptotic cell death was increased in Skp2-anti-sense treated tumors. Our results suggest that down-regulation of Skp2 appears to induce apoptosis in oral cancer cells, targeting this molecule could represent a promising new therapeutic approach for this type of cancer.
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PMID:Down-regulation of S-phase kinase associated protein 2 (Skp2) induces apoptosis in oral cancer cells. 1605 17

The small ubiquitin-related modifier-1 (SUMO-1) with broad cellular expression has been implicated in a range of cellular processes, such as cell proliferation, differentiation, and apoptosis. As shown recently, SUMO-1 is expressed and regulated by gonadotropins, in particular an ovulatory hCG stimulus in mouse granulosa cells in vivo. To test the hypothesis that modulation of granulosa cell apoptosis changes SUMO-1 expression during granulosa cell differentiation in the mouse ovary, we demonstrate that progesterone receptor (PR) proteins are absent in pre-ovulatory granulosa cell nuclei, whereas they are expressed in periovulatory granulosa cell nuclei in parallel with decreases in SUMO-1 expression, caspase-3 activation, and DNA fragmentation in vivo. Second, treatment with either PR antagonists or a cell permeable ceramide analog consistently increases SUMO-1 expression in parallel with an increase in apoptosis as well as a decrease in cell proliferation in periovulatory granulosa cells in vitro. However, we do not observe an increase in SUMO-1 expression in pre-ovulatory granulosa cells that have undergone the same treatment. Third, we have also demonstrated, in pre-ovulatory granulosa cells in vitro, neither induction of spontaneous apoptosis nor the protective effect of EGF against spontaneous apoptosis changes SUMO-1 protein expression. Fourth, we show that induction of apoptosis enhances SUMO-1 conjugation in periovulatory granulosa cells in vitro, pointing to the pivotal link between the SUMO-1 conjugation and cell death. Taken together, our observations suggest that SUMO-1 via sumoylation has an important role in the regulation of granulosa cell apoptosis during granulosa cell differentiation in the mouse ovary.
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PMID:Induction of apoptosis increases SUMO-1 protein expression and conjugation in mouse periovulatory granulosa cells in vitro. 1617 36

A variety of conditions lead to skeletal muscle atrophy including muscle inactivity or disuse, multiple disease states (i.e., cachexia), fasting, and age-associated atrophy (sarcopenia). Given the impact on mobility in the latter conditions, inactivity could contribute in a secondary manner to muscle atrophy. Because different events initiate atrophy in these different conditions, it seems that the regulation of protein loss may be unique in each case. In fact differences exist between the regulation of the various atrophy conditions, especially sarcopenia, as evidenced in part by comparisons of transcriptional profiles as well as by the unique triggering molecules found in each case. By contrast, recent studies have shown that many of the intracellular signaling molecules and target genes are similar, particularly among the atrophies related to inactivity and cachexia. This review focuses on the most recent findings related to intracellular signaling during muscle atrophy. Key findings are discussed that relate to signaling involving muscle ubiquitin ligases, the IGF/PI3K/Akt pathway, FOXO activity, caspase-3 activity, and NF-kappaB signaling, and an attempt is made to construct a unifying picture of how these data can be connected to better understand atrophy. Once more detailed cellular mechanisms of the atrophy process are understood, more specific interventions can be designed for the attenuation of protein loss.
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PMID:Intracellular signaling during skeletal muscle atrophy. 1622 71


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