Inhibition of BIGH3 C-terminal Cleavage as a Therapeutic Target for Diabetic Intervention

BIGH3 is a cell adhesion class proapoptotic extracellular matrix protein induced by transforming growth factor (TGFβ). We have previously shown that BIGH3 induces apoptosis in disease states such as diabetes. In high glucose, the TGFβ signaling pathway is upregulated, causing an increase in expression of the BIGH3 gene (TGFBI) and an increase in apoptosis of kidney proximal tubule epithelial cells. Importantly, our data indicate that the apoptotic signal resides in the C-terminal region of BIGH3, and the apoptotic signal is not activated until the C-terminus is cleaved by proteases. This forms the basis of our hypothesis that polyclonal anti-BIGH3 antibody blocks BIGH3 C-terminal cleavage and apoptosis. To test this hypothesis our methods will employ human cells cultured as a monolayer, cell synthesis and secretion of endogenous BIGH3 protein, anti-BIGH3 antibody, immunoprecipitation, SDS-PAGE and Western blot analysis to quantify the extent that antibody blocks BIGH3 cleavage. TUNEL analysis will test that antibody-treated BIGH3 does not induce apoptosis. Our preliminary results indicate that there is less cleavage of BIGH3 in the presence of antibody. We will extend this study and presently conclude that an ability to block BIGH3 C-terminal cleavage will also block apoptosis. If this conclusion is shown to be true, then we have a reagent that could lead toward translation al research to slow down the progression of kidney disease in diabetic patients.Research was supported by UTSA Work Study Research Training Program.