Chronic oxidative stress in diabetes, resulting from a combination of chronic inflammation and mitochondrial dysfunction, is a major contributing factor in the debilitating pathologies associated with this disease. Due to JAK2's crucial role as a signal transducer for leptin, growth hormone, ciliary neurotrophic factor, stromal derived factor 1?, insulin, and other growth and survival factors, the loss of JAK2's kinase activity would be predicted to contribute to the genesis and progression of many diabetes-associated pathologies. Yet there is such a poor understanding of the fundamental biochemical and cellular mechanisms whereby oxidative stress regulates JAK2-mediated signal propagation that the true linkage between JAK/STAT and redox pathways in diabetes may be unrecognized. Based on a recent discovery of a """"""""redox switch"""""""" that directly links oxidizing conditions to JAK2's catalytic behavior, the applicant's lab is poised to conduct a series of """"""""proof of concept"""""""" experiments to demonstrate that chronic oxidative stress results in the pathophysiological redox regulation of JAK2 in diabetes. A three-pronged approach is proposed to test the following central hypothesis: Sustained oxidative stress impairs JAK2's kinase activity by oxidizing a """"""""redox switch"""""""" in its catalytic domain, and the resulting loss of signal throughput causes pathological consequences in a cell-dependent fashion. The first approach will be to confirm that the specific physiologically-relevant reactive oxygen species generated in type II diabetic oxidative stress are capable of inhibiting JAK2's activity in vitro, and that the redox potential that triggers the """"""""redox switch"""""""" is indeed within the physiological range observed in the redox state of diabetic tissues. The second approach will be to confirm that the """"""""redox switch"""""""" functions as proposed in the context of the cell, and to confirm that physiologically-relevant reactive oxygen species impairs JAK2-mediated signal transduction in several different cytokine/cell combinations. The third approach is to confirm that the interplay between redox-sensitive kinases and phosphatases will determine the net JAK2-mediated signal throughput in silico, by developing a systems biology model system which inputs authentic biological parameters and validates the predicted outcome against the observed biological results. This will spur the generation of new hypotheses about the potential contribution of oxidative inhibition of JAK2 in specific debilitating pathologies and guide future efforts to develop novel therapies.
It is now clear that chronic oxidative stress leads to many of the debilitating and often fatal conditions that accompany diabetes, such as kidney failure, cardiovascular disease, nerve damage and blindness, although we do not fully understand the molecular chain of events that allows chronic oxidative stress to cause such dreadful consequences. We do know, however, that most of the damaged cells require an enzyme (JAK2) to process signals from dozens of cytokines and hormones, including insulin. Based on their recent discovery of a redox switch in this important enzyme, the applicants will investigate how oxidative stress interferes with the function of JAK2 in diabetes, and provide a better understanding of the molecular processes that need to be corrected in order to cure this disease.
| Kurdi, Mazen; Sivakumaran, Vidhya; Duhe, Roy J et al. (2012) Depletion of cellular glutathione modulates LIF-induced JAK1-STAT3 signaling in cardiac myocytes. Int J Biochem Cell Biol 44:2106-15 |
| Smith, John K; Patil, Chetan N; Patlolla, Srikant et al. (2012) Identification of a redox-sensitive switch within the JAK2 catalytic domain. Free Radic Biol Med 52:1101-10 |
| Zouein, Fouad A; Duhe, Roy J; Booz, George W (2011) JAKs go nuclear: emerging role of nuclear JAK1 and JAK2 in gene expression and cell growth. Growth Factors 29:245-52 |
