TY - JOUR T1 - Chromomycin A<sub>2</sub> potently inhibits glucose-stimulated insulin secretion from pancreatic beta cells JF - bioRxiv DO - 10.1101/337113 SP - 337113 AU - Michael A Kalwat AU - In Hyun Hwang AU - Jocelyn Macho AU - Magdalena G Grzemska AU - Jonathan Z Yang AU - Kathleen McGlynn AU - John B MacMillan AU - Melanie H Cobb Y1 - 2018/01/01 UR - http://biorxiv.org/content/early/2018/06/04/337113.abstract N2 - Compounds that enhance or inhibit insulin secretion could become therapeutics as well as lead to the identification of requisite β cell regulatory pathways and increase our understanding of pancreatic islet function. Toward this goal, we previously generated an insulin-linked luciferase that is co-secreted with insulin in MIN6 β cells. With this assay we completed a high-throughput natural product screen for chronic effects on glucose-stimulated insulin secretion. Using a distributive phenotypic analysis approach we identified that one of the top natural product hits, chromomycin A2 (CMA2), potently inhibited insulin secretion (EC50=11.8 nM) through at least three mechanisms: disruption of Wnt signaling, interfering with β cell gene expression, and suppression of triggering calcium influx. Chronic treatment with CMA2 largely ablated glucose-stimulated insulin secretion even post-washout, but did not inhibit glucose-stimulated generation of ATP, Ca2+ influx, or ERK1/2 activation. However, experiments using the KATP channel opener diazoxide uncovered defects in the triggering Ca2+ influx which may contribute to the suppressed secretory response. Using the FUSION bioinformatic database, we found that the phenotypic effects of CMA2 clustered with a number of Wnt/GSK3β pathway-related genes. Consistently, CMA2 decreased GSK3β phosphorylation and suppressed activation of a β-catenin activity reporter. CMA2 and a related natural product mithramycin are described to have DNA-interaction properties, possibly abrogating transcription factor binding to critical β cell gene promoters. We observed that CMA2, but not mithramycin, suppressed expression of PDX1 and UCN3. Neither expression of INSI/II or insulin content was affected. We conclude that chronic treatment with CMA2 treatment results in the disruption of signaling pathways and expression of genes that support β cell function that both support Ca2+ influx and are required downstream, independent of insulin abundance. Future applications of CMA2 and similar aureolic acid analogs for disease therapies should consider the potential impacts on pancreatic islet function. ER -