Overexpression of Insulin Degrading Enzyme: Cellular Localization and Effects on Insulin Signaling

Seta, Karen A.; Roth, Richard A.

doi:10.1006/bbrc.1997.6066

Cited by 78 publications

(56 citation statements)

References 24 publications

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“…The other, IDE E111V , also exhibits about 1% activity but binds substrate with virtually the same K m as the wild type enzyme. 2 Based on the induced conformational change model, a dimer between IDE H112Q and wild type IDE should not exhibit significant activation by peptides since only one of its subunits can bind substrate and catalyze the reaction. In contrast, a dimer between wild type IDE and IDE E111V would be expected to exhibit peptide-dependent activation since both subunits can bind substrate, and the catalytically inactive subunit should be able to induce the hypothetical conformation change in the active subunit.…”

Section: Resultsmentioning

confidence: 99%

Substrate Activation of Insulin-degrading Enzyme (Insulysin)

Song

Juliano

et al. 2003

Journal of Biological Chemistry

122

164

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The rate of the insulin-degrading enzyme (IDE)-catalyzed hydrolysis of the fluorogenic substrate 2-aminobenzoyl-GGFLRKHGQ-ethylenediamine-2,4-dinitrophenyl is increased 2-7-fold by other peptide substrates but not by peptide non-substrates. This increased rate is attributed to a decrease in K m with little effect on V max . An ϳ2.5-fold increase in the rate of amyloid ␤ peptide hydrolysis is produced by dynorphin B-9. However, with insulin as substrate, dynorphin B-9 is inhibitory. Immunoprecipitation of differentially tagged IDE and gel filtration analysis were used to show that IDE exists as a mixture of dimers and tetramers. The equilibrium between dimer and tetramer is concentration-dependent, with the dimer the more active form. Bradykinin shifted the equilibrium toward dimer. Activation of substrate hydrolysis is not seen with a mixed dimer of IDE containing one active subunit and one subunit that is catalytically inactive and deficient in substrate binding. On the other hand, a mixed dimer containing one active subunit and one subunit that is catalytically inactive but binds substrate with normal affinity is activated by peptides. These findings suggest that peptides bind to one subunit of IDE and induce a conformational change that shifts the equilibrium to the more active dimer as well as activates the adjacent subunit. The selective activation of IDE toward amyloid ␤ peptide relative to insulin suggests the potential for development of compounds that increase IDE activity toward amyloid ␤ peptide as a therapeutic intervention for the treatment of Alzheimer's disease.

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Section: Resultsmentioning

confidence: 99%

Substrate Activation of Insulin-degrading Enzyme (Insulysin)

Song

Juliano

et al. 2003

Journal of Biological Chemistry

122

164

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“…Loss-offunction mutations or pharmacological inhibition of IDE increases amyloid accumulation in pancreatic beta cells and in the central nervous system [19][20][21]. On the other hand, IDE overproduction increases insulin degradation and decreases the efficiency of insulin stimulation in the insulin signalling pathway [22]. These data demonstrate that the regulation of IDE expression and/or the activity of the protein may contribute to the pathogenesis of type 2 diabetes.…”

Section: Introductionmentioning

confidence: 82%

Glucose inhibits the insulin-induced activation of the insulin-degrading enzyme in HepG2 cells

et al. 2009

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Aims/hypothesis Hepatic insulin degradation decreases in type 2 diabetes. Insulin-degrading enzyme (IDE) plays a key role in insulin degradation and its gene is located in a diabetes-associated chromosomal region. We hypothesised that IDE may be regulated by insulin and/or glucose in a liver cell model. To validate the observed regulation of IDE in vivo, we analysed biopsies of human adipose tissue during different clamp experiments in men. Methods Human hepatoma HepG2 cells were incubated in normal (1 g/l) or high (4.5 g/l) glucose medium and treated with insulin for 24 h. Catalytic activity, mRNA and protein levels of IDE were assessed. IDE mRNA levels were measured in biopsies of human subcutaneous adipose tissue before and at 240 min of hyperinsulinaemic, euglycaemic and hyperglycaemic clamps. Results In HepG2 cells, insulin increased IDE activity under normal glucose conditions with no change in IDE mRNA or protein levels. Under conditions of high glucose, insulin increased mRNA levels of IDE without changes in IDE activity. Both in normal and high glucose medium, insulin increased levels of the catalytically more active 15a IDE isoform compared with the 15b isoform. In subcutaneous adipose tissue, IDE mRNA levels were not significantly upregulated after euglycaemic or hyperglycaemic clamps. Conclusions/interpretation Insulin increases IDE activity in HepG2 cells in normal but not in high glucose conditions. This disturbance cannot be explained by corresponding alterations in IDE protein levels or IDE splicing. The loss of insulin-induced regulation of IDE activity under hyperglycaemia may contribute to the reduced insulin extraction and peripheral hyperinsulinaemia in type 2 diabetes.

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“…Cerebrospinal Fluid-Although there have been reports of the release of IDE from cells (14,15) and the presence of intact, 110-kDa IDE at the cell surface (16), it has generally been assumed that IDE is restricted to the cytosol and peroxisomes and is not normally released from cells (7,17). However, our results in the previous section show that readily detectable amounts of enzymatically active IDE are found in the medium of intact BV-2 cells under normal culture conditions, including in serum-containing cultures.…”

Section: Detection Of Intact Ide In Fresh Humanmentioning

confidence: 99%

Insulin-degrading Enzyme Regulates Extracellular Levels of Amyloid β-Protein by Degradation

Qiu

Walsh

et al. 1998

Journal of Biological Chemistry

765

617

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Excessive cerebral accumulation of the 42-residue amyloid ␤-protein (A␤) is an early and invariant step in the pathogenesis of Alzheimer's disease. Many studies have examined the cellular production of A␤ from its membrane-bound precursor, including the role of the presenilin proteins therein, but almost nothing is known about how A␤ is degraded and cleared following its secretion. We previously screened neuronal and nonneuronal cell lines for the production of proteases capable of degrading naturally secreted A␤ under biologically relevant conditions and concentrations. The major such protease identified was a metalloprotease released particularly by a microglial cell line, BV-2. We have now purified and characterized the protease and find that it is indistinguishable from insulin-degrading enzyme (IDE), a thiol metalloendopeptidase that degrades small peptides such as insulin, glucagon, and atrial natriuretic peptide. Degradation of both endogenous and synthetic A␤ at picomolar to nanomolar concentrations was completely inhibited by the competitive IDE substrate, insulin, and by two other IDE inhibitors. Immunodepletion of conditioned medium with an IDE antibody removed its A␤-degrading activity. IDE was present in BV-2 cytosol, as expected, but was also released into the medium by intact, healthy cells. To confirm the extracellular occurrence of IDE in vivo, we identified intact IDE in human cerebrospinal fluid of both normal and Alzheimer subjects. In addition to its ability to degrade A␤, IDE activity was unexpectedly found be associated with a time-dependent oligomerization of synthetic A␤ at physiological levels in the conditioned media of cultured cells; this process, which may be initiated by IDE-generated proteolytic fragments of A␤, was prevented by three different IDE inhibitors. We conclude that a principal protease capable of down-regulating the levels of secreted A␤ extracellularly is IDE.Converging lines of evidence support the hypothesis that progressive cerebral accumulation of the 40 -42-residue amyloid ␤-proteins (A␤s) 1 is an early, invariant, and necessary step in the pathogenesis of Alzheimer's disease (AD). As a result, there is growing interest in decreasing cerebral A␤ levels as a therapeutic and preventative approach to the disease. A␤ is generated by endoproteolysis of the ␤-amyloid precursor protein (APP) and secreted constitutively by most mammalian cells throughout life. Whereas many studies have examined the proteolytic processing of APP and the mechanisms of A␤ production, almost nothing is known about how A␤ peptides are normally degraded and cleared following their secretion. We recently screened the conditioned media of several different cell lines for A␤-degrading activity and found that the principal such activity was conferred by a nonmatrix metalloprotease that was released by microglial cells and other cells and efficiently degraded both endogenous and synthetic A␤ (1). The release of the protease from microglial cells was augmented by activating the cells with lipopolysa...

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Overexpression of Insulin Degrading Enzyme: Cellular Localization and Effects on Insulin Signaling

Cited by 78 publications

References 24 publications

Substrate Activation of Insulin-degrading Enzyme (Insulysin)

Substrate Activation of Insulin-degrading Enzyme (Insulysin)

Glucose inhibits the insulin-induced activation of the insulin-degrading enzyme in HepG2 cells

Insulin-degrading Enzyme Regulates Extracellular Levels of Amyloid β-Protein by Degradation

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