Metabolic signaling of the beta cell primary cilium

Project Summary Primary cilia serve as cellular sensors for rapid detection of environmental changes. These microtubule- based antennae are expressed on almost all eukaryotic cells across unicellular and multicellular systems and encompass wide roles in development and homeostasis. In recent years, primary cilia have come into the limelight in diabetes and metabolism research, as previously unappreciated functions have been attributed to these organelles on endocrine cells. Recent human genetic and GWAS studies show that cilia have clinically important roles in metabolic diseases including obesity and diabetes. In the pancreatic islet, we observe that loss of cilia disrupts β-cell endocrine functions including glucose-stimulated Ca2+ signaling and insulin secretion. Mice lacking cilia on β-cells develop glucose intolerance and diet-induced diabetes. These findings suggest that primary cilia mediate glucose responsiveness in normal β-cells, but the molecular drivers of ciliary glucose- sensing and signaling are unknown. In addition, proteome and metabolome profiling have been done in other mammalian cilia but not in pancreatic islet β-cells, posing a knowledge gap regarding cilia-dependent regulatory mechanisms in β-cell glucose metabolism and secretory function. Our preliminary studies identify glycolytic signaling machinery in β-cell cilia, both by proteomics and with a palette of newly developed biosensors that monitor the dynamics of ciliary signaling. We further demonstrate that glycolytic fluxes differ between primary cilia and cytosol in β-cells. Based on these findings, we hypothesize that compartmentalized glucose metabolism in β-cell cilia generates signals that regulate ciliary and cellular function. To test this hypothesis, we will combine genetic loss-of-function models with state-of-the-art proteomic and metabolic profiling tools, microscopy, electrophysiological recordings, and islet function tests to delineate the mechanisms by which cilia effect glucose-dependent β-cell functional changes. Aim 1 will leverage strong functional imaging, proteomic, and metabolomics expertise and promising pilot data to delineate the signaling network by which primary cilia relay glycolytic information and to comprehensively identify ciliary signaling pathways relevant to β- cell function. Aim 2 will determine the mechanisms by which cilia regulate β-cell electrophysiological properties and intracellular metabolic crosstalk leading to insulin secretion. A detailed understanding of these regulations by primary cilia could support the development of novel therapies to modulate β-cell function in diabetes.