Crosstalk between insulin receptor and G protein-coupled receptor signaling systems leads to Ca²+ oscillations in pancreatic cancer PANC-1 cells.

We examined crosstalk between the insulin receptor and G protein-coupled receptor (GPCR) signaling pathways in individual human pancreatic cancer PANC-1 cells. Treatment of cells with insulin (10 ng/ml) for 5 min markedly enhanced the proportion of cells that display an increase in intracellular [Ca²+] induced by picomolar concentrations of the GPCR agonist neurotensin. Interestingly, insulin increased the proportion of a subpopulation of cells that exhibit intracellular [Ca²+] oscillations in response to neurotensin at concentrations as low as 50-200 pM. Insulin enhanced GPCR-induced Ca²+ signaling in a time- and dose-dependent manner; a marked potentiation was obtained after an exposure to a concentration of 10 ng/ml for 5 min. Treatment with the mTORC1 inhibitor rapamycin abrogated the increase in GPCR-induced [Ca²+](i) oscillations produced by insulin. Our results identify a novel aspect in the crosstalk between insulin receptor and GPCR signaling systems in pancreatic cancer cells, namely that insulin increases the number of [Ca²+](i) oscillating cells induced by physiological concentrations of GPCR agonists through an mTORC1-dependent pathway.