Communications Project

Document Type:Master's Thesis
Name:Nirav Parghi
Title:Characterization of Insulin-like Growth Factor Binding Protein-3 (IGFBP-3) interaction with the Bovine Aortic Endothelial (BAE) cell surface : Examination of the Role of Heparan Sulfate Proteoglycans (HSPG).
Degree:Master of Science
Department:Chemical Engineering
Committee Chair: Kimberly E. Forsten
Committee Members:R. Michael Akers
William L. Conger
Keywords:HSPG, IGFBP-3, binding, BAE, KD
Date of defense:July 15, 1998
Availability:Release the entire work immediately worldwide.


Insulin-like growth factor binding proteins (IGFBPs) are known to be important modulators of the insulin-like growth factor (IGF-I). However, their precise role is as yet unclear. Further, recent studies have indicated that IGFBP-3 has a receptor mediated growth inhibitory response of its own. In the present study, we quantified the binding characteristics of IGFBP-3 to bovine aortic endothelial (BAE) cells. Binding studies at 4 oC were conducted and a specific binding curve for IGFBP-3 was obtained. IGFBP-3 was found to bind with an equilibrium dissociation constant (KD) value of 3.1 x 10-10 M. The role of heparan sulfate proteoglycans (HSPG) in the IGFBP-3 binding mechanism was also examined. It was seen that inactivation of the cell surface HSPGs with 75 mM sodium chlorate did not affect IGFBP-3 binding. Further, there have been reports of inhibition of IGFBP-3 binding by heparin in the media. Hence, the most probable interaction of HSPG with IGFBP-3 occurs in the extracellular region, with soluble HSPGs acting as receptors for IGFBP-3 and decreasing the net cell associated ligand receptor interaction. This is likely, since IGFBP-3 is known to possess a heparin binding domain. Simultaneous introduction of IGF-I and IGFBP-3 into the extracellular media decreased IGFBP-3 binding to the cell surface, which might imply that IGF-I and IGFBP-3 regulate each otherís action.

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