Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.24.56 (insulin-degrading enzyme)
 737 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The activity of insulin-degrading enzyme (IDE), a thiol metalloprotease degrading insulin in many insulin target cells, was determined in human colon adenocarcinoma (Caco-2) cells. Insulin-degrading activity was localized in the cytosol of Caco-2 cells, accounting for 88% of total activity. Western blots and immunoprecipitation showed that IDE was present in the cytosol of Caco-2 cells and contributed to more than 93% cytosolic insulin-degrading activity. Cytosolic insulin degradation was strongly inhibited by IDE inhibitors, including N-ethylmaleimide, 1,10-phenanthroline, p-chloromericuribenzoate, and EDTA, but was not significantly or not as extensively inhibited by strong inhibitors of proteasome, i.e., chymostatin, soybean trypsin inhibitor, leupeptin, and Dip-F. These results suggest that IDE is present in Caco-2 cells, that Caco-2 IDE has properties similar to those of its counterparts in insulin-target tissues, and that it significantly contributes to intracellular insulin degradation.
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PMID:Insulin-degrading enzyme in a human colon adenocarcinoma cell line (Caco-2). 759 85

The insulin-degrading enzyme (IDE) plays an important role in the cellular metabolism of insulin. Recent studies have also suggested a regulatory role for this protein in controlling the activity of cytoplasmic protein complexes, including the proteasome [multicatalytic proteinase (MCP)] and the glucocorticoid and androgen receptors. Binding of IDE to these complexes increases their activity, whereas the addition of substrates for IDE inhibits activity. This provides a potential mechanism of action for internalized insulin and other IDE substrates in the control of protein turnover. To examine further the interactions, partially purified IDE-MCP complex was treated with EDTA or EGTA, and activity was measured in the absence and presence of various divalent cations (Ca2+, Mn2+, Co2+, and Zn2+) and insulin. EDTA treatment reduced MCP activity and eliminated the effect of insulin on the complex. Divalent cations partially or completely restored MCP activity, but did not restore the effect of insulin. EGTA treatment had a lesser effect on MCP activity, but abolished insulin inhibition of activity. Divalent cations restored the insulin effect. Inhibitors of IDE also blocked the insulin effect on MCP activity, as did treatment with SDS. These findings suggest that conformational changes in the complex may play a role in the insulin control of MCP activity.
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PMID:Regulation of multicatalytic enzyme activity by insulin and the insulin-degrading enzyme. 975 83

Insulin degradation is a regulated process that plays a role in controlling insulin action by removing and inactivating the hormone. Abnormalities in insulin clearance and degradation are present in various pathological conditions including type 2 diabetes and obesity and may be important in producing clinical problems. The uptake, processing, and degradation of insulin by cells is a complex process with multiple intracellular pathways. Most evidence supports IDE as the primary degradative mechanism, but other systems (PDI, lysosomes, and other enzymes) undoubtedly contribute to insulin metabolism. Recent studies support a multifunctional role for IDE, as an intracellular binding, regulatory, and degradative protein. IDE increases proteasome and steroid hormone receptor activity, and this activation is reversed by insulin. This raises the possibility of a direct intracellular interaction of insulin with IDE that could modulate protein and fat metabolism. The recent findings would place intracellular insulin-IDE interaction into the insulin signal transduction pathway for mediating the intermediate effects of insulin on fat and protein turnover.
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PMID:Insulin degradation: progress and potential. 979 60

A major metabolic effect of insulin is inhibition of cellular proteolysis, but the proteolytic systems involved are unclear. Tissues have multiple proteolytic systems, including the ATP- and ubiquitin-dependent proteasome pathway. The effect of insulin on this pathway was examined in vitro and in cultured cells. Insulin inhibited ATP- and ubiquitin-dependent lysozyme degradation more than 90% by reticulocyte extract, in a dose-dependent manner (IC50 approximately 50 nM). Insulin did not reduce the conjugation of ubiquitin to lysozyme and was not itself ubiquitin-conjugated. In HepG2 cells, insulin increased ubiquitin-conjugate accumulation 80%. The association between the 26S proteasome and an intracellular protease, the insulin-degrading enzyme (IDE), was examined by a purification scheme designed to enrich for the 26S proteasome. Copurification of IDE activity and immunoreactivity with the proteasome were detected through several chromatographic steps. Glycerol gradient analysis revealed cosedimentation of IDE with the 20S proteasome and possibly with the 26S proteasome. The proteasome-associated IDE was displaced when the samples were treated with insulin. These results suggest that insulin regulates protein catabolism, at least in part, by decreasing ubiquitin-mediated proteasomal activity, and provides a new target for insulin action. The displacement of IDE from the proteasome provides a mechanism for this insulin action.
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PMID:Insulin inhibits the ubiquitin-dependent degrading activity of the 26S proteasome. 1087 52

A pathological feature of Type 2 diabetes is deposits in the pancreatic islets primarily composed of amylin (islet amyloid polypeptide). Although much attention has been paid to the expression and secretion of amylin, little is known about the enzymes involved in amylin turnover. Recent reports suggest that insulin-degrading enzyme (IDE) may have specificity for amyloidogenic proteins, and therefore we sought to determine whether amylin is an IDE substrate. Amylin-degrading activity co-purified with IDE from rat muscle through several chromatographic steps. Metalloproteinase inhibitors inactivated amylin-degrading activity with a pattern consistent with the enzymatic properties of IDE, whereas inhibitors of acid and serine proteases, calpains, and the proteasome were ineffective. Amylin degradation was inhibited by insulin in a dose-dependent manner, whereas insulin degradation was inhibited by amylin. Other substrates of IDE such as atrial natriuretic peptide and glucagon also competitively inhibited amylin degradation. Radiolabeled amylin and insulin were both covalently cross-linked to a protein of 110 kDa, and the binding was competitively inhibited by either unlabeled insulin or amylin. Finally, a monoclonal anti-IDE antibody immunoprecipitated both insulin- and amylin-degrading activities. The data strongly suggest that IDE is an amylin-degrading enzyme and plays an important role in the clearance of amylin and the prevention of islet amyloid formation.
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PMID:Degradation of amylin by insulin-degrading enzyme. 1097 71

Insulin-degrading enzyme is responsible for initiating insulin degradation in cells, but little is known about the factors controlling its activity. Because obesity and high levels of free fatty acids decrease insulin clearance, we examined the effect of some common free fatty acids and their acyl-coenzyme A thioesters on insulin-degrading enzyme partially purified from the livers of male Sprague Dawley rats. Octanoic acid (C8:0) had no effect on activity. Long-chain free fatty acids (C16-C20) inhibited between 50% and 90% of the insulin degradation with IC(50) values in the range of 10-50 micro M. In general, the corresponding acyl-coenzyme A thioesters had lower IC(50) values and were slightly more efficacious. (125)I-insulin cross-linking studies showed free fatty acids did not inhibit hormone binding to insulin-degrading enzyme. Kinetic analysis showed a noncompetitive type of inhibition. Furthermore, fatty acids eliminated the ability of insulin to inhibit the proteasome. These results suggest that when intracellular long-chain fatty acid concentrations are elevated, they may act directly on insulin-degrading enzyme to decrease insulin metabolism and alter insulin action in intact cells. This mechanism may contribute to the hyperinsulinemia and insulin resistance seen with elevated fatty acids and obesity.
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PMID:In vitro inhibition of insulin-degrading enzyme by long-chain fatty acids and their coenzyme A thioesters. 1274 1

A consequence of insulin-dependent diabetes mellitus is the loss of lean muscle mass as a result of accelerated proteolysis by the proteasome. Insulin inhibition of proteasomal activity requires interaction with insulin-degrading enzyme (IDE), but it is unclear if proteasome inhibition is dependent merely on insulin-NIDE binding or if degradation of insulin by IDE is required. To test the hypothesis that degradation by IDE is required for proteasome inhibition, a panel of insulin analogues with variable susceptibility to degradation by IDE binding was used to assess effects on the proteasome. The analogues used were [Lys(B28), Pro(B29)]-insulin (lispro), [Asp(B10)]-insulin (Asp(B10)) and [Glu(B4), Gln(B16), Phe(B17)]-insulin (EQF). Lispro was as effective as insulin at inhibition of degradation of iodine-125 ((125)I)-labeled insulin, but Asp(B10) and EQF were somewhat more effective. All agents inhibited cross-linking of (125)I-insulin to IDE, suggesting that all were capable of IDE binding. In contrast, although insulin and lispro were readily degraded by IDE, Asp(B10) was degraded more slowly, and EQF degradation was undetectable. Both insulin and lispro inhibited the proteasome, but Asp(B10) was less effective, and EQF had little effect. In summary, despite effective IDE binding, EQF was poorly degraded by IDE, and was ineffective at proteasome inhibition. These data suggest that insulin inhibition of proteasome activity is dependent on degradation by IDE. The mechanism of proteasome inhibition may be the generation of inhibitory fragments of insulin, or by displacement of IDE from the proteasome.
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PMID:Insulin inhibition of the proteasome is dependent on degradation of insulin by insulin-degrading enzyme. 1277 20

The paradigm of endoplasmic reticulum (ER)-associated degradation (ERAD) holds that misfolded secretory and membrane proteins are translocated back to the cytosol and degraded by the proteasome in a coupled process. Analyzing the degradation of ER-localized amyloid beta-peptide (Abeta), we found a divergence from this general model. Cell-free reconstitution of the export in biosynthetically loaded ER-derived brain microsomes showed that the export was mediated by the Sec61p complex and required a cytosolic factor but was independent of ATP. In contrast to the ERAD substrates known so far, the exported Abeta was degraded by both, a proteasome-dependent and a proteasome-independent pathway. RNA interference experiments in Abeta-transfected cells identified the protease of the proteasome-independent pathway as insulin-degrading enzyme (IDE). The IDE-mediated clearance mechanism for ER-localized Abeta represents an as yet unknown type of ERAD which is not entirely dependent on the proteasome.
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PMID:Endoplasmic reticulum-localized amyloid beta-peptide is degraded in the cytosol by two distinct degradation pathways. 1469 Apr 98

HIV-1 protease inhibitors have revolutionized the treatment of HIV infection, but their use has been associated with lipodystrophy and insulin resistance. One suggestion for this has been the inhibition of insulin-degrading enzyme (IDE). We have previously demonstrated that insulin, through IDE, can inhibit the proteasome, thus decreasing cytosolic protein degradation. We examined whether the protease inhibitor nelfinavir inhibited IDE and its effect on protein degradation both in vitro and in whole cells. 125I-Insulin degradation was measured by trichloroacetic acid precipitation. Proteasome activities were measured using fluorogenic peptide substrates. Cellular protein degradation was measured by prelabelling cells with 3H-leucine and determining the release of TCA-soluble radioactivity. Nelfinavir inhibited IDE in a concentration-dependent manner with 50% inhibition at the maximal concentration tested, 100 microm. Similarly, the chymotrypsin-like and trypsin-like activities of the proteasome were decreased with an IC50 of approximately 3 microm. The ability of insulin to inhibit the proteasome was abrogated by nelfinavir. Treatment of HepG2 cells with 50 microm nelfinavir decreased 125I-insulin degradation and increased cell-associated radioactivity. Insulin alone maximally decreased protein degradation by 15%. Addition of 50 microm nelfinavir inhibited cellular protein degradation by 14% and blunted the effect of insulin. These data show that nelfinavir inhibits IDE, decreases insulin's ability to inhibit protein degradation via the proteasome and provides another possible mechanism for the insulin resistance seen in protease inhibitor-treated HIV patients.
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PMID:Effect of nelfinavir on insulin metabolism, proteasome activity and protein degradation in HepG2 cells. 1702 90

Proteins are vital to the overall structure of cells and to the function of cells in the form of enzymes. Thus the control of protein metabolism is among the most important aspects of cellular metabolism. Insulin's major effect on protein metabolism in the adult animal is inhibition of protein degradation. This is via inhibition of proteasome activity via an interaction with insulin-degrading enzyme (IDE). IDE is responsible for the majority of cellular insulin degradation. We hypothesized that a reduction in IDE would reduce insulin degradation and insulin's ability to inhibit protein degradation. HepG2 cells were transfected with siRNA against human IDE and insulin degradation and protein degradation measured. Both IDE mRNA and protein were reduced by >50% in the IDE siRNA transfected cells. Insulin degradation was reduced by approximately 50%. Cells were labeled with [3H]-leucine to investigate protein degradation. Short-lived protein degradation was unchanged in the cells with reduced IDE expression. Long-lived and very-long-lived protein degradation was reduced in the cells with reduced IDE expression (14.0+/-0.16 vs. 12.5+/-0.07%/4h (long-lived), 9.6+/-2.2% vs. 7.3+/-0.2%/3h (very-long-lived), control vs. IDE transfected, respectively, P<0.005). The inhibition of protein degradation by insulin was reduced 37-76% by a decreased expression of IDE in HepG2 cells. This shows that IDE is involved in cellular insulin metabolism and provides further evidence that insulin inhibits protein degradation via an interaction with IDE.
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PMID:Regulation of protein degradation by insulin-degrading enzyme: analysis by small interfering RNA-mediated gene silencing. 1796 27


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