Glucose-regulated and drug perturbed beta-cell phosphoproteome reveals molecular mechanisms controlling insulin secretion

Insulin-secreting beta cells play an essential role in maintaining physiological blood glucose levels, and their dysfunction leads to the development of diabetes. To elucidate the signaling events regulating insulin secretion, we applied a recently developed proteomics and phosphoproteomics workflow. We quantified the time-resolved phosphoproteome of beta cells following their exposure to glucose and in combination with small molecule compounds that promote insulin secretion. The quantitative phosphoproteome of 30,000 sites clustered into three main groups in concordance with the modulation of three key signaling pathways. In addition to their differential modulation of key cellular kinases, all compounds affected pathways regulating the cell cycle. A high-resolution time course revealed key novel regulatory sites in early and late insulin secretion, and unexpected connections to epigenetic regulation of gene expression. Our comprehensive and multi-parametric phosphoproteomics study reveals that control of insulin secretion is embedded in an unexpectedly broad and complex range of cellular functions.