Possible role of cell surface insulin degrading enzyme in cultured human lymphocytes

Abstract

The kinetic changes of insulin receptors and cell surface insulin degrading enzyme were examined in Bri-7 cultured human lymphocytes after preincubation with or without insulin. The concentration of cell surface insulin degrading enzyme was determined by immunoenzymatic labeling method using a polyclonal antiserum to insulin degrading enzyme. In Bri-7 cells preincubated with 10(-10) to 10(-5) mol/l insulin for 18 h, the surface insulin receptors and insulin degrading enzyme decreased progressively as a function of the concentration of insulin in the preincubation medium. The surface insulin receptors and insulin degrading enzyme of cells preincubated with 10(-6) mol/l insulin were decreased to 25 and 35% of the control respectively. In Bri-7 cells preincubated with 10(-6) mol/l insulin for 30 min to 18 h, the loss of surface insulin degrading enzyme was slightly slower than that of the receptors; however, the curves were essentially parallel to each other. Thus, the treatment of Bri-7 cells with insulin caused down-regulation of insulin receptors in a dose- and time-dependent manner. Cell surface insulin degrading enzyme also decreased simultaneously. A combination of several insulin degradation assays (trichloroacetic acid precipitation, gel filtration and receptor rebinding) demonstrated that cell surface bound insulin remained intact, and that the degradation in Bri-7 cells seemed to be a limiting proteolysis of insulin. Furthermore, by the receptor rebinding method insulin degrading activity in cells after preincubation with 10(-6) mol/l insulin (19.6 +/- 4.6%) was decreased, although not significantly, as compared with cells after preincubation without insulin (24.6 +/- 4.8%).(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin Degrading Enzyme Is a Cellular Receptor Mediating Varicella-Zoster Virus Infection and Cell-to-Cell Spread

“…Interestingly, VZV as well as the two coronaviruses use enzymes as receptors, independent of the activity of the enzyme. Although IDE is predominately a cytosolic protein, it is also present on the plasma membrane (Goldfine et al, 1984;Kuo et al, 1993;Yaso et al, 1987). It localizes to apical or basolateral regions in different tissues (Kuo et al, 1993).…”

“…Computer analysis indicates that the predicted sequence of IDE contains a putative amino-terminal signal peptide with a potential cleavage site between residues 22 and 23, and the majority of the sequence might be extracellular; however, a typical transmembrane domain is not apparent (TMHMM program, Technical University of Denmark). Cell fractionation studies showed that IDE is localized primarily in the cytosol (Akiyama et al, 1988), with a small amount present on the cell-surface plasma membrane (Seta and Roth, 1997;Yaso et al, 1987). Vekrellis et al (2000) identified a 115 kDa cell-surface membrane-associated IDE isoform on neuronal cells (Vekrellis et al, 2000).…”

Pathways of Processing of Insulin by Antigen‐Presenting Cells

“…More recently, IDE has been detected on the surface plasma membrane of cultured Bri-7 human B lymphocytes (Yaso et al 1987) and in cytosolic fractions of IM-9 B lymphocytes (Shii & Roth 1986). However, the nature of the insulin peptides cleaved by IDE in this cell type has not been identified.…”

“…"We believe that insulin protease is actively released from TA3 B lymphocytes since the cell viabiUty did not change significantly during the 4h incubation. It is noteworthy that IDE also appears to be released from the surface membrane of cultured hepatocytes (Duckworth et al 1979, Yokono et al 1982, Goldfine et al 1984) and lymphocytes (Yaso et al 1987). This may suggest that shedding or active release of IDE occurs regularly in different cell types and may serve some physiological function.…”

“…Since IDE activity is associated with the surface plasma membrane and this activity is somewhat labile (Yaso et al 1987), we next sought to determine whether processing of insulin by IDE is sufficient to generate insulin peptides which can bind to MHC class II on isolated plasma membranes. For these experiments, we used a monoclonal antibody, 9B12, specific for IDE (Shii & Roth 1986).…”