Autophagy/antioxidant response coupling in pancreatic beta-cell homeostasis regulation

The incidence of diabetes in the US population has been rapidly increasing over the past several decades. Type 1 diabetes is a result of β-cell death, or apoptosis of the insulin-producing cells in the pancreas. While there are a variety of known triggers for β-cell apoptosis, most feed into pathways that lead to increased generation of reactive oxygen species (ROS) in the β-cell. Unchecked accumulation of β-cell ROS can disrupt cellular homeostasis, cause oxidative damage, and lead to apoptosis. A typical adaptive response to increased ROS includes activation of the transcription factor NRF2, which stimulates the cell-protective antioxidant response and restores homeostasis. We recently found that tandem activation of interleukin-6 (IL-6) receptor signaling and NRF2 in the β-cell couples autophagy to the antioxidant response, reduces β-cell ROS, and protects against oxidative damage to increase β-cell survival in vivo. Importantly, we discovered that non-canonical actions of NRF2 in the mitochondria were associated with the stimulation of mitophagy, the selective degradation of mitochondria by autophagy. Collectively, these data lead to our hypothesis that autophagy and antioxidant response are coupled in the β-cell and that orchestration of these processes is essential for maintenance of β-cell homeostasis and diabetes prevention. The proposed work will incorporate both in vitro experiments using cultured islets/ β-cells and in vivo analyses in mice. We will pursue the following specific aims: 1) To identify the mechanism controlling NRF2 mitochondrial translocation and determine its role in β-cell autophagy/antioxidant response coupling; and 2) To determine the in vivo contributions of autophagy/antioxidant response coupling to β-cell homeostasis. Overall, these experiments will define the role of autophagy/antioxidant response coupling in the adaptive response to stress and allow us to identify therapeutic targets guiding the signaling events within the islet under conditions known to lead to β-cell failure. My background in β-cell biology and resources within the Indiana Center for Diabetes and Metabolic Diseases makes me uniquely suited to accomplish the aims of this project.