Sensing the Insulin Signaling Pathway with an Antibody Array
Hua-Jun He, Y Zong, Michel Bernier, Lili Wang
Defects within the insulin signaling pathways are a major locus for the development of insulin resistance and type 2 diabetes. The phorbol 12-myristate 13-acetate (PMA) is commonly described as a mediator of insulin resistance through the activation of the protein kinase C isoforms, IB kinase (IKK ) and c-Jun N-terminal kinase (JNK), and subsequent inhibition of the proximal insulin signaling pathway via the insulin receptor substrate 1 (IRS1) and Akt. The molecular mechanism of the insulin resistance is still largely unknown. Because the studies of insulin resistance are generally carried out with western blot analysis that is labor intensive and limited by the low sensitivity, it is pivotal to develop a fast and efficient high-throughput method for studying insulin resistance and screening diabetes drug candidates. To obtain broad information about the insulin signaling cascade, we have used human HepG2 hepatoma cells as a cell model system and targeted a few key signaling biomolecules involving in the metobolic and mitogenic signaling pathways, using a newly developed antibody array. The results of the antibody array were further compared to those from the multiplexed bead arrays and conventional western blot analysis. For the effects of PMA on the insulin signaling pathways, our antibody array results are consistent with the previous reports. Moreover, we found the evidence for a new possible mechanism of PMA-induced insulin resistance that could involve the activation of a phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase and dual-specificity protein phosphatase (PTEN) and a heat shock 27kDa protein (Hsp27). Our study suggests that this antibody array provides a powerful mean for investigating the mechanism of the insulin resistance and evaluating the effects of therapeutic drugs for type 2 diabetes.