Insulin signaling (IIS) regulates metabolism, growth, and environmental stress responses and influences longevity in multicellular organisms. Specialized endocrine cells (pancreatic b cells of vertebrates or insulin producing cells, IPCs, of Drosophila) produce Insulin-like peptides (ILPs) and thus systemically regulate a range of biological processes in several distinct IIP target tissues. A better understanding of how insulin production is regulated by environmental parameters is required for rational approaches to treat and prevent metabolic diseases that are caused by IIS dysregulation, such as diabetes. Preliminary studies by the sponsor have shown that the stress-responsive Jun-N-terminal Kinase (JNK) signaling pathway represses ILP expression in IPCs of Drosophila and thereby regulates IIS activity throughout the organism. These findings suggest the JNK pathway as a relay for metabolic responses to stress. It remains unclear, however, how JNK is activated in IPCs. This application proposes to investigate potential mechanisms of this activation. The experiments proposed in aim 1 will identify which of the JNK - activating kinases (JNKKKs) encoded by the Drosophila genome are required for IPC-specific JNK activation and Insulin regulation.
Aim2 intends to assess whether JNK activation in IPCs is initiated by oxidative stress directly or by hormones secreted from peripheral tissues. The experiments proposed in the first two aims will use a candidate approach to identify and characterize the role of potential regulators of JNK signaling.
In aim 3, in contrast, an unbiased genetic screen to identify novel regulators of JNK and Insulin production in IPCs is proposed.
All aims are based on genetic approaches using Drosophila and include transcriptional and metabolic analysis, as well as demographic analysis of mortality in populations of different genotypes exposed to a variety of environmental conditions. PUBLIC HEALTH REALEVANCE: The studies proposed here will assess the regulation of insulin production and physiology by stress signaling in an intact organism. Due to the evolutionary conservation of IIS and JNK signaling, as well as the functional analogy of IPCs and pancreatic b cells, it can be expected that the insight generated by studies in Drosophila will help to understand this regulatory system, its components, and its physiological and pathological impact on metabolic homeostasis and aging in vertebrates.
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