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

RIN-m cells, cultured from a rat insulinoma, not only bind and secrete but also degrade insulin (Diabetes 1982; 31:521-31). The insulin-degrading activity resides in the cytosol and is similar to the insulin-specific proteases previously described in muscle and other tissues. It has an apparent Km of 0.15 microM for porcine insulin in crude cell-free extracts, a competitive inhibition constant for proinsulin that is close to the Km, and a lower but measurable affinity for glucagon. The enzyme is inactive at pHs below 6.0, indicating that it is not lysosomal, is completely inhibited by N-ethylmaleimide, and exhibits apparent competitive inhibition constants (microM) for the following peptides: desoctapeptide insulin, 0.043; guinea pig insulin, 0.048; proinsulin, 0.64; insulin B-chain, 1.17; glucagon, 7.0; and cyclic somatostatin, 8.6. Highly active insulin-degrading activity was found using cell suspensions of 22 cloned and 8 subcloned cell lines derived from RIN-m as well as 11 other continuous cell lines derived from a variety of nonislet tissues of rat, mouse, and human origin. Homogenates of the original rat islet tumor and cytosol of normal rat islets also contained insulin-degrading activity. Although insulin protease is present in a variety of tissues, it may have an additional regulatory function in cells that are actively synthesizing, storing, and secreting insulin.
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PMID:Cytosolic insulin-degrading activity in islet-derived tumor cell lines and in normal rat islets. 298 50

A tumor antigen isolated from the cytosol of a methylcholanthrene-induced sarcoma (Meth A) has been purified to homogeneity by the criteria of two-dimensional gel analysis and NH2- and COOH-terminal sequencing. The purified antigen has a mol. wt of 82,000 by SDS gel electrophoresis. However, the apparent mol. mass of the antigen was found to be 71,600 and 67,700 by gel filtration chromatography and sedimentation analysis, respectively. It is not a glycoprotein, possesses an acidic isoelectric point (6.0) and exists as dimeric and monomeric species. The dimer is not held together by disulfide bonds. The purified protein retains its ability to induce transplantation immunity in syngeneic hosts when challenged with Meth A sarcomas. Chemical analyses of the NH2- and COOH-termini gave the following sequences: NH2-PKPINVRVTTMDAELEFAIQPN and IDE(F,A)EM-COOH, respectively.
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PMID:Characterization of a chemically homogeneous tumor antigen from a methylcholanthrene-induced sarcoma, Meth A. 374 14

A method has been described for the direct measurement of proinsulin in human plasma. The method makes use of an insulin-degrading enzyme designated "insulin-specific protease (ISP)", which is obtained from rat skeletal muscle. Under the conditions used, this enzyme rapidly degrades insulin and insulin-like polypeptides to nonimmunoassayable components, whereas proinsulin and proinsulin cleaved at position B(54,55) are not appreciably affected. The incubation of plasma with ISP results in the disappearance of insulin, but not proinsulin, as demonstrated by column chromatography. Immunoassay of the plasma, therefore, before and after incubation, determines the values for the total immunoreactive substance (TIR) and for immunoreactive proinsulin (IRP), respectively. The values obtained for proinsulin levels are reproducible and compare closely with the more complicated column fractionation methods. Proinsulin responses were studied in four normal subjects and one patient with an insulinoma after a glucose load. Fasting proinsulin levels varied widely in the normal subjects, and the levels rose more slowly than TIR levels after glucose. IRP levels in the patient with an insulinoma were very high and fell to normal after removal of the tumor. The ISP method, therefore, appears to be suitable for the direct, accurate, and rapid determination of proinsulin and proinsulin-like materials in human plasma.
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PMID:Direct measurement of proinsulin in human plasma by the use of an insulin-degrading enzyme. 432 76

In previous literature, the existence of a new insulin-like substance found in tumor tissues, termed substance immunologically cross-reactive with insulin (SICRI), has been proposed. In these studies, insulin-specific radioimmunoassay (RIA) was the only detection method for SICRI. The mouse melanoma B16BL6 cell line was found to be a rich source of SICRI. In this paper, we show that SICRI is not expressed in B16BL6 cells. Previous RIA measurements were wrongly ascribed to SICRI. What was really measured was a positive artifact caused by insulin tracer degradation in RIA. Several lines of evidence indicate that protease responsible for insulin degradation in B16BL6 cells in insulin-degrading enzyme (IDE; EC 3.4.22.11). First, SICRI activity of B16BL6 cytosol measured by insulin RIA was inhibited by thiol protease inhibitor N-ethylmaleimide (NEM). Thiol active agents as well as metal chelators, both potent IDE blockers, inhibited also the insulin-degrading activity of the same sample. Second, cross-linking to 125I-labeled insulin of partially purified sample with highest insulin RIA activity specifically labeled only a single protein with molecular mass similar to IDE (110 kDa). Labeling was blocked by 'cold' insulin in excess. Third, kinetic studies of insulin degradation by RIA active chromatographic fractions revealed an apparent Kd of 90 nM which is very similar to the reported affinity of insulin for IDE (Kd = 100 nM). Additionally, in B16BL6 as well as in mouse myeloid leukemia cells, IDE gene is actively transcribed and this expression was found to be much stronger than in normal mouse tissues. In conclusion, our results strongly question the real existence of SICRI.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Detection of the substance immunologically cross-reactive with insulin in insulin RIA is an artifact caused by insulin tracer degradation: involvement of the insulin-degrading enzyme. 789 11

Insulin is a hormone crucial to metabolism and an essential growth factor for normal and neoplastic tissues. We have now determined insulin in extracts of 23 primary breast cancer specimens and of non-neoplastic breast tissues by a chemiluminescent immunoassay. Remarkably, insulin was measured only in grade 3 tumors, whereas grade 2 carcinomas and the normal mammary gland were each insulin-negative. We also performed immunohistochemistry for insulin-degrading enzyme (IDE), a cytoplasmic zinc metalloprotease belonging to the inverzincin family and participating in insulin cleavage. IDE was detected in most insulin-positive grade 3 carcinomas, indicating that it might be dysfunctional in these anaplastic tumors. IDE was equally present in the insulin-negative grade 2 carcinomas. Moreover, five grade 3 carcinomas and one grade 2 carcinoma displayed a loss of heterozygosity in the 10q chromosomal region harboring the IDE gene, but, despite these alterations, IDE was detected immunohistochemically, indicating a retention of the second allele. Compared to the expression of IDE in 92% of the tumors examined, only 57% of 21 normal breast specimens stained positively for IDE. In contrast to this increase in IDE-positive epithelial cells in breast cancer vs. normal breast, additional immunohistochemical analysis of 17 node-positive breast carcinomas and corresponding tumor-bearing lymph nodes showed that IDE expression decreases from primary tumor to lymph node metastasis. Altogether, this study represents the first demonstration of IDE in normal and neoplastic human mammary tissues. Our present report should also provide an experimental starting point towards exploring a potential role of IDE in the control of tumor progression.
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PMID:Immunohistochemical demonstration of the zinc metalloprotease insulin-degrading enzyme in normal and malignant human breast: correlation with tissue insulin levels. 1714 14

Immunohistochemical evidence of ubiquitous distribution of the metalloprotease insulin-degrading enzyme (IDE; insulysin) in human non-malignant tissues and tumor cells is presented. Immunohistochemical staining was performed on a multi-organ tissue microarray (pancreas, lung, kidney, central/peripheral nervous system, liver, breast, placenta, myocardium, striated muscle, bone marrow, thymus, and spleen) and on a cell microarray of 31 tumor cell lines of different origin, as well as trophoblast cells and normal blood lymphocytes and granulocytes. IDE protein was expressed in all the tissues assessed and all the tumor cell lines except for Raji and HL-60. Trophoblast cells and granulocytes, but not normal lymphocytes, were also IDE-positive.
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PMID:Immunohistochemical evidence of ubiquitous distribution of the metalloendoprotease insulin-degrading enzyme (IDE; insulysin) in human non-malignant tissues and tumor cell lines. 1878 35

Insulin-degrading enzyme (IDE, insulysin, insulinase; EC 3.4.22.11), a thiol metalloendopeptidase, is involved in intracellular degradation of insulin, thereby inhibiting its translocation and accumulation to the nucleus. Recently, protein expression of IDE has been demonstrated in the epithelial ducts of normal breast and breast cancer tissue. Utilizing four different antibodies generated against different epitopes of the IDE molecule, we performed Western blot analysis and immunohistochemical staining on several normal human tissues, on a plethora of tumor cell lines of different tissue origin, and on malignant breast and ovarian tissue. Applying the four IDE-directed antibodies, we demonstrated IDE expression at the protein level, by means of immunoblotting and immunocytochemistry, in each of the tumor cell lines analyzed. Insulin-degrading enzyme protein expression was found in normal tissues of the kidney, liver, lung, brain, breast and skeletal muscle, as well as in breast and ovarian cancer tissues. Immunohistochemical visualization of IDE indicated cytoplasmic localization of IDE in each of the cell lines and tissues assessed. In conclusion, we performed for the first time a wide-ranging survey on IDE protein expression in normal and malignant tissues and cells thus extending our knowledge on the cellular and tissue distribution of IDE, an enzyme which to date has mainly been studied in connection with Alzheimer's disease and diabetes but not in cancer.
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PMID:Expression of metalloprotease insulin-degrading enzyme insulysin in normal and malignant human tissues. 1881 47

Previous investigations on proteasomal preparations containing insulin-degrading enzyme (IDE; EC 3.4.24.56) have invariably yielded a co-purifying protein with a molecular weight of about 110kDa. We have now found both in MCF-7 breast cancer and HepG2 hepatoma cells that this associated molecule is the retinoblastoma tumor suppressor protein (RB). Interestingly, the amount of RB in this protein complex seemed to be lower in HepG2 vs. MCF-7 cells, indicating a higher (cytoplasmic) protein turnover in the former vs. the latter cells. Moreover, immunofluorescence showed increased nuclear localization of RB in HepG2 vs. MCF-7 cells. Beyond these subtle differences between these distinct tumor cell types, our present study more generally suggests an interplay between RB and IDE within the proteasome that may have important growth-regulatory consequences.
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PMID:Retinoblastoma protein co-purifies with proteasomal insulin-degrading enzyme: implications for cell proliferation control. 2036 53

Most antigenic peptides presented by major histocompatibility complex (MHC) class I molecules are produced by the proteasome. Here we show that a proteasome-independent peptide derived from the human tumor protein MAGE-A3 is produced directly by insulin-degrading enzyme (IDE), a cytosolic metallopeptidase. Cytotoxic T lymphocyte recognition of tumor cells was reduced after metallopeptidase inhibition or IDE silencing. Separate inhibition of the metallopeptidase and the proteasome impaired degradation of MAGE-A3 proteins, and simultaneous inhibition of both further stabilized MAGE-A3 proteins. These results suggest that MAGE-A3 proteins are degraded along two parallel pathways that involve either the proteasome or IDE and produce different sets of antigenic peptides presented by MHC class I molecules.
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PMID:Production of an antigenic peptide by insulin-degrading enzyme. 2036 50

Antigen presentation by MHC class I molecules requires degradation of epitope source proteins in the cytosol. Although the preeminent role of the proteasome is clearly established, evidence suggesting a significant role for proteasome-independent generation of class I ligands has been reported repeatedly. However, an enzyme responsible for such a role has not been identified. Recently insulin-degrading enzyme (IDE) was shown to produce an antigenic peptide derived from the tumor antigen MAGE-A3 in an entirely proteasome-independent manner, raising the question of the global impact of IDE in MHC class I antigen processing. Here we report that IDE knockdown in human cell lines, or knockout in two different mouse strains, has no effect on cell surface expression of various MHC class I molecules, including allomorphs such as HLA-A3 and HLA-B27 suggested to be loaded in an at least a partly proteasome-independent manner. Moreover, reduced or absent IDE expression does not affect presentation of five epitopes including epitopes derived from beta amyloid and proinsulin, two preferred IDE substrates. Thus, IDE does not play a major role in MHC class I antigen processing, confirming the dominant and almost exclusive role of the proteasome in cytosolic production of MHC class I ligands.
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PMID:No major role for insulin-degrading enzyme in antigen presentation by MHC molecules. 2451 42


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