Investigating the Role of Disulfide Bond Formation in FABP5

Abstract

EGF signaling activates multiple pathways within the cell that lead towards proliferation, rendering this pathway of interest for cancer therapy. Recent studies focused on triple-negative breast cancer have shown that EGF-induced tumorigenesis strongly correlates with the up-regulation of FABP5, which shuttles fatty acids from the cytoplasm of cells to the nucleus. Our work began with the identification of redox active cysteine residues upon EGF activation in situ using a caged electrophile to perform live cell labeling. In these studies, the C120 residue of FABP5 was identified as a cysteine with high redox activity and thus became a subject of further interest. The characterization of redox active cysteine residues yields important information about protein structure and function. We have confirmed these results via in-gel fluorescence and developed fluorescence assays to probe the significance of C120 and C127 in FABP5. Two fatty acids were chosen based on their conformation in the FABP5 binding pocket. Upon the addition of a fatty acid, wild type protein showed a decrease in fluorescence indicating that the fatty acids were outcompeting the fluorophores used. Future studies will investigate both wild type and mutant versions of FABP5 with emphasis on determining potential disulfide bond formation via phosphoproteomics and western blotting techniques.