Identification of Compounds That Inhibit IGF-I Signaling in Hyperglycemia

Abstract

Increased responsiveness of vascular cells to the growth factor IGF-I has been implicated in complications associated with diabetes. Here we describe the development of an assay and screening of a library of compounds for their ability to accelerate cleavage of the transmembrane protein integrin-associated protein (IAP) thereby disrupting the association between IAP and SHPS-1 which we have shown as critical for the enhanced response of vascular cells to IGF-I. The cell-based ELISA utilizes an antibody that specifically detects cleaved, but not intact, IAP. Of the 1040 compounds tested, 14 were considered active by virtue of their ability to stimulate an increase in antibody-binding indicative of IAP cleavage. In experiments with smooth muscle and retinal endothelial cell cultures in hyperglycemic conditions, each active compound was shown to accelerate the cleavage of IAP, and this was associated with a decrease in IAP association with SHPS-1 as determined by coimmunoprecipitation of the proteins from cell lysates. As a consequence of the acceleration in IAP cleavage, the compounds were shown to inhibit IGF-I-stimulated phosphorylation of key signaling molecules including Shc and ERK1/2, and this in turn was associated with a decrease in IGF-I-stimulated cell proliferation. Identification of these compounds that utilize this mechanism has the potential to yield novel therapeutic approaches for the prevention and treatment of vascular complications associated with diabetes.

CD47 Signaling Regulates the Immunosuppressive Activity of VEGF in T Cells

“…1C). Both antibodies detected the 50-55 kDa N-glycosylated and >200 kDa proteoglycan isoforms of CD47 and a previously described 36 kDa proteolytic fragment of CD47 (28, 35) in the immunoprecipitates from WT Jurkat cells that were absent in the corresponding immunoprecipitates from JinB8 cells. The CD47 antibody B6H12 detected several nonspecific bands in VEGFR2 immunoprecipitates from JinB8 cells that were not detected by the CD47 antibody R529.…”

CD47-dependent immunomodulatory and angiogenic activities of extracellular vesicles produced by T cells

“…Our previous studies have demonstrated that CD47 is released into conditioned medium by Jurkat T cells ( Kaur et al, 2011 ). This could be soluble CD47 produced by proteolytic cleavage of its IgV domain ( Maile et al, 2009 ) or intact CD47 associated with EVs. In order to identify a potential functional role of this released CD47 in T cell activation, we transferred conditioned media (CM) between wild type Jurkat and CD47-deficient JinB8 T cell cultures.…”

“…Because CD47 has been shown to be present on platelet ectosomes ( Sadallah et al, 2011 ) and as a proteolytically cleaved fragment in conditioned media ( Maile et al, 2009 ), we considered whether the transfer of CD47 to the CD47-deficient cells restores their sensitivity to modulation of TCR signaling by TSP1. Alternatively, this effect of CD47 could be indirect, and indirect effects of CD47 are obviously necessary to account for the ability of conditioned medium from CD47-deficient cells to confer resistance of WT Jurkat cells to TSP1 inhibition.…”

“…CD47 is a cell surface receptor that interacts laterally with VEGFR2 and integrins in endothelial cells ( Brown and Frazier, 2001 ; Kaur et al, 2010 ). CD47 can be cleaved via proteolysis from the surface of endothelial and smooth muscle cells and is important for SHP2-dependent insulin growth factor signaling ( Maile et al, 2009 ). CD47 shed into conditioned medium by endothelial cells, smooth muscle cells, and T cells has heparan sulfate modification ( Kaur et al, 2011 ).…”

Evaluation of Glycemic and Lipid Profile of Offspring of Diabetic Wistar Rats Treated withMalpighia emarginataJuice

“…The presence of diabetes may hasten the development of endothelial lesions and atherosclerosis, which may be minimized by the presence of antioxidants [43, 44]. …”