NEW COMPONENTS OF THE INSULIN SIGNALING PATHWAY: INVESTIGATING THE ROLE OF NOVEL PROTEINS IN GLUT4 TRANSLOCATION

Abstract

In the twentieth century, scientists Sir Frederick Banting and Charles Best demonstrated the effect of exogenous insulin to correct hyperglycemia. A later identified component of insulin signaling is the translocation of GLUT4, a glucose transporter protein that shuttles glucose from outside the cell membrane into the cell, lowering blood glucose levels and allowing cells to use circulating glucose as energy. Despite the extensive characterization of proteins upstream of GLUT4 translocation, the exact mechanism starting from insulin signaling to GLUT4 translocation is still not fully identified. Using quantitative proteomic analysis of mouse epididymal tissue samples, 604 proteins were identified that were significantly increased in adipocytes. It is hypothesized that knocking down a protein involved in insulin signal transduction will lead to a significantly decreased cellular uptake of glucose following insulin signaling. Identified protein candidates were knocked down in vitro using 3T3-L1 adipocytes. Cellular uptake of glucose was quantified using a radioactive glucose uptake assay and knockdown of proteins were executed by and confirmed with siRNA and quantitative PCR, respectively. Due to inconsistent fold changes in glucose uptake using known proteins in the insulin signal transduction pathway, further experimental design changes are needed before further protein screening can occur.